Vibecode Screaming Frog SEO Spider

You are building a lean indie version of Screaming Frog SEO Spider.

Create the following project files first, then implement the application by following them. Keep the files updated as decisions change. Do not collapse this into a single README or prompt.

===== README.md =====
# Screaming Frog SEO Spider · indie build

Build a bounded crawler for an owned site with evidence-based technical reports.

Estimated effort: **multi-day**. Work `BUILD_PLAN.md` top to bottom · every phase ends in a check that has to pass before the next one starts.

## Stack

| Part | Choice | Why |
| --- | --- | --- |
| Runtime | Python 3.12+ and Flask | A small local HTTP application with readable server-side handlers and no JavaScript build pipeline. |
| Storage | SQLite through Python sqlite3 | Local ownership with explicit transactions and a portable backup path. |
| Interface | Jinja HTML templates, CSS and vanilla JavaScript | Implement the specified screens directly with labelled controls and progressive enhancement. |
| Verification | Python unittest and browser acceptance fixtures | Check invariants and the actual user workflow before the next phase. |
| Focused libraries | beautifulsoup4, requests | Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions. |

## Before you start

Have every one of these ready. The plan assumes them from step one.

- [ ] **Python 3.12 or newer and a terminal** · Python is free; this local prototype requires no hosting subscription.
  - Why: The local backend, tests and storage use Python.
  - Get it: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages.
  - Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds.
- [ ] **A current desktop browser and text editor** · No paid service required for this local step.
  - Why: You need to view the local interface and edit generated project files.
  - Get it: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository.
  - Verify: You can create a text file in the project folder and open browser developer tools.
- [ ] **Screaming Frog SEO Spider acceptance sample** · No paid service required for this local step.
  - Why: This fixture makes the first end-to-end check reproducible.
  - Get it: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records.
  - Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account.
- [ ] **Confirm the bounded replacement** · No paid service required for this local step.
  - Why: The full commercial product is larger than this guide.
  - Get it: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first.
  - Verify: You can name the primary workflow and the vendor features this version deliberately leaves out.

## Quick start

```sh
python -m venv .venv
python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
python -m pip freeze > requirements.txt
python -m flask --app app run --host 127.0.0.1
```

Then copy `.env.example` to `.env` and fill in the values it documents.

## Honest limits

This build deliberately does not replace:

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

If one of those is essential to you, that is the reason to keep paying for Screaming Frog SEO Spider, and the README should say so rather than pretend.

===== BRIEF.md =====
# Build brief · Screaming Frog SEO Spider

The one-shot brief this plan expands. `BUILD_PLAN.md` (or `MILESTONES.md`) is the same sequence broken into steps and checks; where the two disagree, the plan wins.

Build me a bounded crawler for an owned site with evidence-based technical reports as a bounded replacement for Screaming Frog SEO Spider.
Build it in phases in the order below. Do not write the whole product in one pass.
Finish the current phase, run its Done when checks, fix failures, then continue.
Indie mode completes Phases 1-5. Phase 6 is required before shared or public deployment.

### Stack (fixed, do not substitute)
- Runtime: Python 3.12+ and Flask. A small local HTTP application with readable server-side handlers and no JavaScript build pipeline.
- Storage: SQLite through Python sqlite3. Local ownership with explicit transactions and a portable backup path.
- Interface: Jinja HTML templates, CSS and vanilla JavaScript. Implement the specified screens directly with labelled controls and progressive enhancement.
- Verification: Python unittest and browser acceptance fixtures. Check invariants and the actual user workflow before the next phase.
- Focused libraries: beautifulsoup4, requests. Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions.

### Data model (create this before Phase 1)
- crawls(id,origin,started_at,limit,state)
- urls(id,crawl_id,url,status,content_type,title,canonical,depth,error)
- edges(source_id,target_url)
- findings(id,url_id,rule,evidence)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address.

### Prerequisites and configuration
- Python 3.12 or newer and a terminal: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages. Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds. Cost: Python is free; this local prototype requires no hosting subscription.
- A current desktop browser and text editor: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository. Verify: You can create a text file in the project folder and open browser developer tools. Cost: No paid service required for this local step.
- Screaming Frog SEO Spider acceptance sample: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records. Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account. Cost: No paid service required for this local step.
- Confirm the bounded replacement: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first. Verify: You can name the primary workflow and the vendor features this version deliberately leaves out. Cost: No paid service required for this local step.
- Configuration: DATA_DIR, SECRET_KEY, APP_MODE, SITE_URL. Ship .env.example, replace placeholders and exclude secrets from git.

### Phase 1 · Local foundation and data contract
Build: Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

- Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch. Commands, after creating the named files: `python -m venv .venv`; `python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests`; `python -m pip freeze > requirements.txt`; `python -m flask --app app run --host 127.0.0.1`.
- For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data. Commands, after creating the named files: `python manage.py init`; `python manage.py seed`.
- Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
- Trap: The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

Done when: The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000. Restarting preserves the seeded records or canonical files; running init again deletes nothing. A cross-origin state-changing request to an admin route is refused.
Do not build yet: Do not start safe crawl boundary until these checks pass.

### Phase 2 · Safe crawl boundary
Build: Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

- Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
- Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

Done when: The page cap stops enqueueing beyond its limit. In normal mode a redirect to a private address is refused before fetching it.
Do not build yet: Do not start extract and explain until these checks pass.

### Phase 3 · Extract and explain
Build: Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

- Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
- Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Do not treat canonical declarations as redirects or guaranteed indexing behavior.

Done when: The fixture reports its 404 link and both duplicate-title pages. A noindex page is reported as noindex, not automatically classified as an error.
Do not build yet: Do not start resumable audit exports until these checks pass.

### Phase 4 · Resumable audit exports
Build: Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

- Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
- Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Network errors and blocked pages need an unknown state rather than an invented success score.

Done when: Stopping and resuming the fixture does not create duplicate URL rows. Each reported finding can be reproduced from its saved evidence.
Do not build yet: Do not start portable delivery and clean-start proof until these checks pass.

### Phase 5 · Portable delivery and clean-start proof
Build: Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

- Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
- Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
- Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete. Commands, after creating the named files: `python -m pip install -r requirements.txt`; `python -m unittest discover -s test`.
- Trap: Export without an import or restore rehearsal is not verified portability.

Done when: A new folder reaches the documented fixture outcome using only README instructions. A backup restored in isolation preserves the proof data and can be opened.
Do not build yet: Do not start operate and share with access controls until these checks pass.

### Phase 6 · Operate and share with access controls (product-builder only)
Build: Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

- Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
- Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them. Commands, after creating the named files: `waitress-serve --listen=127.0.0.1:5000 app:app`.
- Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
- Trap: Product mode is additional engineering, not a switch that makes a local prototype production-ready.

Done when: An unauthenticated visitor cannot read private records, download private files or mutate the admin surface. A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries. Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.
Do not build yet: Do not add new providers or vendor-scale features until the release gates are recorded.

### Out of scope (and why)
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance: retain the paid product if this capability is essential; it is outside this bounded build.
- massive hosted crawl capacity: retain the paid product if this capability is essential; it is outside this bounded build.
- proprietary scoring: retain the paid product if this capability is essential; it is outside this bounded build.
- continuous monitoring: retain the paid product if this capability is essential; it is outside this bounded build.
- agency reporting and support: retain the paid product if this capability is essential; it is outside this bounded build.

### README must contain
- Exact install, configure, initialize, start, test and recovery commands for a clean folder.
- The schema, fixture, acceptance results, private data locations and export format.
- Every prerequisite and secret source, actual running costs and deliberately excluded capabilities.
- An honest distinction between tests actually run and checks still awaiting real credentials or deployment.
- Dependency documentation reviewed 2026-09-05: https://flask.palletsprojects.com/en/stable/installation/ ; https://docs.python.org/3/library/sqlite3.html ; https://flask-wtf.readthedocs.io/en/1.2.x/csrf/ ; https://docs.pylonsproject.org/projects/waitress/en/stable/usage.html. Recheck before upgrading; freeze the versions actually tested.

===== AGENTS.md =====
# Agent instructions · Screaming Frog SEO Spider indie build

- Read `README.md` and `BUILD_PLAN.md` before writing code. The stack is fixed: Python 3.12+ and Flask, SQLite through Python sqlite3, Jinja HTML templates, CSS and vanilla JavaScript, Python unittest and browser acceptance fixtures, beautifulsoup4, requests. Do not substitute.
- Work one phase at a time, in order. Do not start a phase until every "Done when" item of the previous one passes.
- Prefer the fewest moving parts that satisfy the step. No frameworks, services or dependencies the plan does not name.
- Secrets live in `.env`, never in source or logs. Keep `.env.example` current when a variable is introduced.
- Do not invent cryptography, security guarantees, APIs or compliance claims.
- Add a focused test for every destructive, security-sensitive or data-loss path the plan names.
- Run the project checks before declaring a phase complete, and record any deliberate shortcut in the README under "Tradeoffs".

## Known traps

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- Do not treat canonical declarations as redirects or guaranteed indexing behavior.
- Network errors and blocked pages need an unknown state rather than an invented success score.
- Export without an import or restore rehearsal is not verified portability.

===== BUILD_PLAN.md =====
# Build plan · Screaming Frog SEO Spider

Build a bounded crawler for an owned site with evidence-based technical reports.

Phases are in dependency order. Each ends in a "Done when" list; treat an unticked item as a blocker, not a note.

## Phase 1 · Local foundation and data contract

Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

### Steps

1. Create and start the local application
   Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch.
   Files: `app.py`, `requirements.txt`, `.env.example`, `.gitignore`

   ```sh
   python -m venv .venv
   python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
   python -m pip freeze > requirements.txt
   python -m flask --app app run --host 127.0.0.1
   ```

2. Implement storage and seed the named fixture
   For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data.
   Files: `schema.sql`, `db.py`, `manage.py`, `fixtures/README.md`

   ```sh
   python manage.py init
   python manage.py seed
   ```

3. Protect the local request boundary
   Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
   Files: `app.py`, `templates/base.html`, `test/test_foundation.py`

### Done when

- [ ] The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000.
- [ ] Restarting preserves the seeded records or canonical files; running init again deletes nothing.
- [ ] A cross-origin state-changing request to an admin route is refused.

### Watch out

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

## Phase 2 · Safe crawl boundary

Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

### Steps

1. Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Files: `features/safe_crawl_boundary.py`, `templates/safe_crawl_boundary.html`
2. Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Files: `features/safe_crawl_boundary.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_safe_crawl_boundary.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] In normal mode a redirect to a private address is refused before fetching it.

### Watch out

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

## Phase 3 · Extract and explain

Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

### Steps

1. Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Files: `features/extract_and_explain.py`, `templates/extract_and_explain.html`
2. Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Files: `features/extract_and_explain.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_extract_and_explain.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] A noindex page is reported as noindex, not automatically classified as an error.

### Watch out

- Do not treat canonical declarations as redirects or guaranteed indexing behavior.

## Phase 4 · Resumable audit exports

Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

### Steps

1. Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Files: `features/resumable_audit_exports.py`, `templates/resumable_audit_exports.html`
2. Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Files: `features/resumable_audit_exports.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_resumable_audit_exports.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] Each reported finding can be reproduced from its saved evidence.

### Watch out

- Network errors and blocked pages need an unknown state rather than an invented success score.

## Phase 5 · Portable delivery and clean-start proof

Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

### Steps

1. Write the user-facing runbook
   Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
   Files: `README.md`, `.env.example`
2. Create and rehearse a recoverable backup
   Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
   Files: `OPERATIONS.md`, `scripts/backup.py`
3. Reproduce the first-run experience
   Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete.
   Files: `README.md`, `verification.md`

   ```sh
   python -m pip install -r requirements.txt
   python -m unittest discover -s test
   ```


### Done when

- [ ] A new folder reaches the documented fixture outcome using only README instructions.
- [ ] A backup restored in isolation preserves the proof data and can be opened.

### Watch out

- Export without an import or restore rehearsal is not verified portability.

## Not in this build

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

## After v1, if you want it

- Extend resumable audit exports only after the fixture and recovery checks pass.
- Before adding another integration, document its credentials, limits, cost and failure behavior with primary-source links.

===== .env.example =====
# Copy to .env and fill in. Never commit .env; this file documents it.

# Required. A new private folder this application creates on first run; never serve it as static files.
DATA_DIR=./data/screaming-frog-seo-spider

# Required · secret. Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
SECRET_KEY=replace-with-a-random-secret

# Required. Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
APP_MODE=indie

# Required. The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
SITE_URL=http://127.0.0.1:5000

You are building a lean indie version of Screaming Frog SEO Spider.

Create the following project files first, then implement the application by following them. Keep the files updated as decisions change. Do not collapse this into a single README or prompt.

===== README.md =====
# Screaming Frog SEO Spider · indie build

Build a bounded crawler for an owned site with evidence-based technical reports.

Estimated effort: **multi-day**. Work `BUILD_PLAN.md` top to bottom · every phase ends in a check that has to pass before the next one starts.

## Stack

| Part | Choice | Why |
| --- | --- | --- |
| Runtime | Python 3.12+ and Flask | A small local HTTP application with readable server-side handlers and no JavaScript build pipeline. |
| Storage | SQLite through Python sqlite3 | Local ownership with explicit transactions and a portable backup path. |
| Interface | Jinja HTML templates, CSS and vanilla JavaScript | Implement the specified screens directly with labelled controls and progressive enhancement. |
| Verification | Python unittest and browser acceptance fixtures | Check invariants and the actual user workflow before the next phase. |
| Focused libraries | beautifulsoup4, requests | Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions. |

## Before you start

Have every one of these ready. The plan assumes them from step one.

- [ ] **Python 3.12 or newer and a terminal** · Python is free; this local prototype requires no hosting subscription.
  - Why: The local backend, tests and storage use Python.
  - Get it: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages.
  - Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds.
- [ ] **A current desktop browser and text editor** · No paid service required for this local step.
  - Why: You need to view the local interface and edit generated project files.
  - Get it: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository.
  - Verify: You can create a text file in the project folder and open browser developer tools.
- [ ] **Screaming Frog SEO Spider acceptance sample** · No paid service required for this local step.
  - Why: This fixture makes the first end-to-end check reproducible.
  - Get it: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records.
  - Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account.
- [ ] **Confirm the bounded replacement** · No paid service required for this local step.
  - Why: The full commercial product is larger than this guide.
  - Get it: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first.
  - Verify: You can name the primary workflow and the vendor features this version deliberately leaves out.

## Quick start

```sh
python -m venv .venv
python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
python -m pip freeze > requirements.txt
python -m flask --app app run --host 127.0.0.1
```

Then copy `.env.example` to `.env` and fill in the values it documents.

## Honest limits

This build deliberately does not replace:

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

If one of those is essential to you, that is the reason to keep paying for Screaming Frog SEO Spider, and the README should say so rather than pretend.

===== BRIEF.md =====
# Build brief · Screaming Frog SEO Spider

The one-shot brief this plan expands. `BUILD_PLAN.md` (or `MILESTONES.md`) is the same sequence broken into steps and checks; where the two disagree, the plan wins.

Build me a bounded crawler for an owned site with evidence-based technical reports as a bounded replacement for Screaming Frog SEO Spider.
Build it in phases in the order below. Do not write the whole product in one pass.
Finish the current phase, run its Done when checks, fix failures, then continue.
Indie mode completes Phases 1-5. Phase 6 is required before shared or public deployment.

### Stack (fixed, do not substitute)
- Runtime: Python 3.12+ and Flask. A small local HTTP application with readable server-side handlers and no JavaScript build pipeline.
- Storage: SQLite through Python sqlite3. Local ownership with explicit transactions and a portable backup path.
- Interface: Jinja HTML templates, CSS and vanilla JavaScript. Implement the specified screens directly with labelled controls and progressive enhancement.
- Verification: Python unittest and browser acceptance fixtures. Check invariants and the actual user workflow before the next phase.
- Focused libraries: beautifulsoup4, requests. Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions.

### Data model (create this before Phase 1)
- crawls(id,origin,started_at,limit,state)
- urls(id,crawl_id,url,status,content_type,title,canonical,depth,error)
- edges(source_id,target_url)
- findings(id,url_id,rule,evidence)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address.

### Prerequisites and configuration
- Python 3.12 or newer and a terminal: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages. Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds. Cost: Python is free; this local prototype requires no hosting subscription.
- A current desktop browser and text editor: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository. Verify: You can create a text file in the project folder and open browser developer tools. Cost: No paid service required for this local step.
- Screaming Frog SEO Spider acceptance sample: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records. Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account. Cost: No paid service required for this local step.
- Confirm the bounded replacement: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first. Verify: You can name the primary workflow and the vendor features this version deliberately leaves out. Cost: No paid service required for this local step.
- Configuration: DATA_DIR, SECRET_KEY, APP_MODE, SITE_URL. Ship .env.example, replace placeholders and exclude secrets from git.

### Phase 1 · Local foundation and data contract
Build: Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

- Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch. Commands, after creating the named files: `python -m venv .venv`; `python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests`; `python -m pip freeze > requirements.txt`; `python -m flask --app app run --host 127.0.0.1`.
- For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data. Commands, after creating the named files: `python manage.py init`; `python manage.py seed`.
- Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
- Trap: The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

Done when: The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000. Restarting preserves the seeded records or canonical files; running init again deletes nothing. A cross-origin state-changing request to an admin route is refused.
Do not build yet: Do not start safe crawl boundary until these checks pass.

### Phase 2 · Safe crawl boundary
Build: Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

- Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
- Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

Done when: The page cap stops enqueueing beyond its limit. In normal mode a redirect to a private address is refused before fetching it.
Do not build yet: Do not start extract and explain until these checks pass.

### Phase 3 · Extract and explain
Build: Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

- Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
- Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Do not treat canonical declarations as redirects or guaranteed indexing behavior.

Done when: The fixture reports its 404 link and both duplicate-title pages. A noindex page is reported as noindex, not automatically classified as an error.
Do not build yet: Do not start resumable audit exports until these checks pass.

### Phase 4 · Resumable audit exports
Build: Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

- Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
- Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Network errors and blocked pages need an unknown state rather than an invented success score.

Done when: Stopping and resuming the fixture does not create duplicate URL rows. Each reported finding can be reproduced from its saved evidence.
Do not build yet: Do not start portable delivery and clean-start proof until these checks pass.

### Phase 5 · Portable delivery and clean-start proof
Build: Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

- Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
- Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
- Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete. Commands, after creating the named files: `python -m pip install -r requirements.txt`; `python -m unittest discover -s test`.
- Trap: Export without an import or restore rehearsal is not verified portability.

Done when: A new folder reaches the documented fixture outcome using only README instructions. A backup restored in isolation preserves the proof data and can be opened.
Do not build yet: Do not start operate and share with access controls until these checks pass.

### Phase 6 · Operate and share with access controls (product-builder only)
Build: Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

- Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
- Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them. Commands, after creating the named files: `waitress-serve --listen=127.0.0.1:5000 app:app`.
- Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
- Trap: Product mode is additional engineering, not a switch that makes a local prototype production-ready.

Done when: An unauthenticated visitor cannot read private records, download private files or mutate the admin surface. A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries. Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.
Do not build yet: Do not add new providers or vendor-scale features until the release gates are recorded.

### Out of scope (and why)
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance: retain the paid product if this capability is essential; it is outside this bounded build.
- massive hosted crawl capacity: retain the paid product if this capability is essential; it is outside this bounded build.
- proprietary scoring: retain the paid product if this capability is essential; it is outside this bounded build.
- continuous monitoring: retain the paid product if this capability is essential; it is outside this bounded build.
- agency reporting and support: retain the paid product if this capability is essential; it is outside this bounded build.

### README must contain
- Exact install, configure, initialize, start, test and recovery commands for a clean folder.
- The schema, fixture, acceptance results, private data locations and export format.
- Every prerequisite and secret source, actual running costs and deliberately excluded capabilities.
- An honest distinction between tests actually run and checks still awaiting real credentials or deployment.
- Dependency documentation reviewed 2026-09-05: https://flask.palletsprojects.com/en/stable/installation/ ; https://docs.python.org/3/library/sqlite3.html ; https://flask-wtf.readthedocs.io/en/1.2.x/csrf/ ; https://docs.pylonsproject.org/projects/waitress/en/stable/usage.html. Recheck before upgrading; freeze the versions actually tested.

===== AGENTS.md =====
# Agent instructions · Screaming Frog SEO Spider indie build

- Read `README.md` and `BUILD_PLAN.md` before writing code. The stack is fixed: Python 3.12+ and Flask, SQLite through Python sqlite3, Jinja HTML templates, CSS and vanilla JavaScript, Python unittest and browser acceptance fixtures, beautifulsoup4, requests. Do not substitute.
- Work one phase at a time, in order. Do not start a phase until every "Done when" item of the previous one passes.
- Prefer the fewest moving parts that satisfy the step. No frameworks, services or dependencies the plan does not name.
- Secrets live in `.env`, never in source or logs. Keep `.env.example` current when a variable is introduced.
- Do not invent cryptography, security guarantees, APIs or compliance claims.
- Add a focused test for every destructive, security-sensitive or data-loss path the plan names.
- Run the project checks before declaring a phase complete, and record any deliberate shortcut in the README under "Tradeoffs".

## Known traps

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- Do not treat canonical declarations as redirects or guaranteed indexing behavior.
- Network errors and blocked pages need an unknown state rather than an invented success score.
- Export without an import or restore rehearsal is not verified portability.

===== BUILD_PLAN.md =====
# Build plan · Screaming Frog SEO Spider

Build a bounded crawler for an owned site with evidence-based technical reports.

Phases are in dependency order. Each ends in a "Done when" list; treat an unticked item as a blocker, not a note.

## Phase 1 · Local foundation and data contract

Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

### Steps

1. Create and start the local application
   Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch.
   Files: `app.py`, `requirements.txt`, `.env.example`, `.gitignore`

   ```sh
   python -m venv .venv
   python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
   python -m pip freeze > requirements.txt
   python -m flask --app app run --host 127.0.0.1
   ```

2. Implement storage and seed the named fixture
   For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data.
   Files: `schema.sql`, `db.py`, `manage.py`, `fixtures/README.md`

   ```sh
   python manage.py init
   python manage.py seed
   ```

3. Protect the local request boundary
   Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
   Files: `app.py`, `templates/base.html`, `test/test_foundation.py`

### Done when

- [ ] The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000.
- [ ] Restarting preserves the seeded records or canonical files; running init again deletes nothing.
- [ ] A cross-origin state-changing request to an admin route is refused.

### Watch out

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

## Phase 2 · Safe crawl boundary

Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

### Steps

1. Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Files: `features/safe_crawl_boundary.py`, `templates/safe_crawl_boundary.html`
2. Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Files: `features/safe_crawl_boundary.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_safe_crawl_boundary.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] In normal mode a redirect to a private address is refused before fetching it.

### Watch out

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

## Phase 3 · Extract and explain

Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

### Steps

1. Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Files: `features/extract_and_explain.py`, `templates/extract_and_explain.html`
2. Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Files: `features/extract_and_explain.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_extract_and_explain.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] A noindex page is reported as noindex, not automatically classified as an error.

### Watch out

- Do not treat canonical declarations as redirects or guaranteed indexing behavior.

## Phase 4 · Resumable audit exports

Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

### Steps

1. Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Files: `features/resumable_audit_exports.py`, `templates/resumable_audit_exports.html`
2. Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Files: `features/resumable_audit_exports.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_resumable_audit_exports.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] Each reported finding can be reproduced from its saved evidence.

### Watch out

- Network errors and blocked pages need an unknown state rather than an invented success score.

## Phase 5 · Portable delivery and clean-start proof

Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

### Steps

1. Write the user-facing runbook
   Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
   Files: `README.md`, `.env.example`
2. Create and rehearse a recoverable backup
   Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
   Files: `OPERATIONS.md`, `scripts/backup.py`
3. Reproduce the first-run experience
   Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete.
   Files: `README.md`, `verification.md`

   ```sh
   python -m pip install -r requirements.txt
   python -m unittest discover -s test
   ```


### Done when

- [ ] A new folder reaches the documented fixture outcome using only README instructions.
- [ ] A backup restored in isolation preserves the proof data and can be opened.

### Watch out

- Export without an import or restore rehearsal is not verified portability.

## Not in this build

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

## After v1, if you want it

- Extend resumable audit exports only after the fixture and recovery checks pass.
- Before adding another integration, document its credentials, limits, cost and failure behavior with primary-source links.

===== .env.example =====
# Copy to .env and fill in. Never commit .env; this file documents it.

# Required. A new private folder this application creates on first run; never serve it as static files.
DATA_DIR=./data/screaming-frog-seo-spider

# Required · secret. Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
SECRET_KEY=replace-with-a-random-secret

# Required. Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
APP_MODE=indie

# Required. The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
SITE_URL=http://127.0.0.1:5000

You are building a production product version of Screaming Frog SEO Spider.

Create the following project files first, then implement the application by following them. Keep the files updated as decisions change. Do not collapse this into a single README or prompt.

===== PRODUCT.md =====
# Screaming Frog SEO Spider · product brief

## Problem

The core loop is small enough for a capable coding agent to produce a useful local version in one sitting. For Screaming Frog SEO Spider, crawl an owned site locally, inspect technical signals, and export raw audit data. The hard boundary is years of crawl edge cases, javascript rendering, integrations, and desktop performance, plus crawl scale, rule depth, and operational polish.

## Product outcome

An operated version of a bounded crawler for an owned site with evidence-based technical reports, with authorized access, restore evidence and honest scope limits.

## Target user

A builder who needs a maintainable product foundation, not a one-off demo.

## Required capabilities

- Python 3.12
- Playwright browsers
- permission to crawl the target site
- local disk space

## Explicit non-goals for v1

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

## Success criteria

- The page cap stops enqueueing beyond its limit.
- The fixture reports its 404 link and both duplicate-title pages.
- Stopping and resuming the fixture does not create duplicate URL rows.
- A private-data authorization check passes using a second identity.
- An off-host restore drill has a date, observed result and recovery time in OPERATIONS.md.
- README names the excluded vendor capabilities and actual provider/hosting costs.

===== BRIEF.md =====
# Build brief · Screaming Frog SEO Spider

The one-shot brief this plan expands. `BUILD_PLAN.md` (or `MILESTONES.md`) is the same sequence broken into steps and checks; where the two disagree, the plan wins.

Build me a bounded crawler for an owned site with evidence-based technical reports as a bounded replacement for Screaming Frog SEO Spider.
Build it in phases in the order below. Do not write the whole product in one pass.
Finish the current phase, run its Done when checks, fix failures, then continue.
Indie mode completes Phases 1-5. Phase 6 is required before shared or public deployment.

### Stack (fixed, do not substitute)
- Runtime: Python 3.12+ and Flask. A small local HTTP application with readable server-side handlers and no JavaScript build pipeline.
- Storage: SQLite through Python sqlite3. Local ownership with explicit transactions and a portable backup path.
- Interface: Jinja HTML templates, CSS and vanilla JavaScript. Implement the specified screens directly with labelled controls and progressive enhancement.
- Verification: Python unittest and browser acceptance fixtures. Check invariants and the actual user workflow before the next phase.
- Focused libraries: beautifulsoup4, requests. Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions.

### Data model (create this before Phase 1)
- crawls(id,origin,started_at,limit,state)
- urls(id,crawl_id,url,status,content_type,title,canonical,depth,error)
- edges(source_id,target_url)
- findings(id,url_id,rule,evidence)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address.

### Prerequisites and configuration
- Python 3.12 or newer and a terminal: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages. Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds. Cost: Python is free; this local prototype requires no hosting subscription.
- A current desktop browser and text editor: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository. Verify: You can create a text file in the project folder and open browser developer tools. Cost: No paid service required for this local step.
- Screaming Frog SEO Spider acceptance sample: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records. Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account. Cost: No paid service required for this local step.
- Confirm the bounded replacement: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first. Verify: You can name the primary workflow and the vendor features this version deliberately leaves out. Cost: No paid service required for this local step.
- Configuration: DATA_DIR, SECRET_KEY, APP_MODE, SITE_URL. Ship .env.example, replace placeholders and exclude secrets from git.

### Phase 1 · Local foundation and data contract
Build: Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

- Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch. Commands, after creating the named files: `python -m venv .venv`; `python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests`; `python -m pip freeze > requirements.txt`; `python -m flask --app app run --host 127.0.0.1`.
- For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data. Commands, after creating the named files: `python manage.py init`; `python manage.py seed`.
- Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
- Trap: The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

Done when: The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000. Restarting preserves the seeded records or canonical files; running init again deletes nothing. A cross-origin state-changing request to an admin route is refused.
Do not build yet: Do not start safe crawl boundary until these checks pass.

### Phase 2 · Safe crawl boundary
Build: Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

- Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
- Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

Done when: The page cap stops enqueueing beyond its limit. In normal mode a redirect to a private address is refused before fetching it.
Do not build yet: Do not start extract and explain until these checks pass.

### Phase 3 · Extract and explain
Build: Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

- Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
- Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Do not treat canonical declarations as redirects or guaranteed indexing behavior.

Done when: The fixture reports its 404 link and both duplicate-title pages. A noindex page is reported as noindex, not automatically classified as an error.
Do not build yet: Do not start resumable audit exports until these checks pass.

### Phase 4 · Resumable audit exports
Build: Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

- Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
- Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Network errors and blocked pages need an unknown state rather than an invented success score.

Done when: Stopping and resuming the fixture does not create duplicate URL rows. Each reported finding can be reproduced from its saved evidence.
Do not build yet: Do not start portable delivery and clean-start proof until these checks pass.

### Phase 5 · Portable delivery and clean-start proof
Build: Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

- Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
- Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
- Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete. Commands, after creating the named files: `python -m pip install -r requirements.txt`; `python -m unittest discover -s test`.
- Trap: Export without an import or restore rehearsal is not verified portability.

Done when: A new folder reaches the documented fixture outcome using only README instructions. A backup restored in isolation preserves the proof data and can be opened.
Do not build yet: Do not start operate and share with access controls until these checks pass.

### Phase 6 · Operate and share with access controls (product-builder only)
Build: Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

- Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
- Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them. Commands, after creating the named files: `waitress-serve --listen=127.0.0.1:5000 app:app`.
- Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
- Trap: Product mode is additional engineering, not a switch that makes a local prototype production-ready.

Done when: An unauthenticated visitor cannot read private records, download private files or mutate the admin surface. A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries. Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.
Do not build yet: Do not add new providers or vendor-scale features until the release gates are recorded.

### Out of scope (and why)
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance: retain the paid product if this capability is essential; it is outside this bounded build.
- massive hosted crawl capacity: retain the paid product if this capability is essential; it is outside this bounded build.
- proprietary scoring: retain the paid product if this capability is essential; it is outside this bounded build.
- continuous monitoring: retain the paid product if this capability is essential; it is outside this bounded build.
- agency reporting and support: retain the paid product if this capability is essential; it is outside this bounded build.

### README must contain
- Exact install, configure, initialize, start, test and recovery commands for a clean folder.
- The schema, fixture, acceptance results, private data locations and export format.
- Every prerequisite and secret source, actual running costs and deliberately excluded capabilities.
- An honest distinction between tests actually run and checks still awaiting real credentials or deployment.
- Dependency documentation reviewed 2026-09-05: https://flask.palletsprojects.com/en/stable/installation/ ; https://docs.python.org/3/library/sqlite3.html ; https://flask-wtf.readthedocs.io/en/1.2.x/csrf/ ; https://docs.pylonsproject.org/projects/waitress/en/stable/usage.html. Recheck before upgrading; freeze the versions actually tested.

===== ARCHITECTURE.md =====
# Architecture · Screaming Frog SEO Spider

## Stack

| Part | Choice | Why |
| --- | --- | --- |
| Runtime | Python 3.12+ and Flask | A small local HTTP application with readable server-side handlers and no JavaScript build pipeline. |
| Storage | SQLite through Python sqlite3 | Local ownership with explicit transactions and a portable backup path. |
| Interface | Jinja HTML templates, CSS and vanilla JavaScript | Implement the specified screens directly with labelled controls and progressive enhancement. |
| Verification | Python unittest and browser acceptance fixtures | Check invariants and the actual user workflow before the next phase. |
| Focused libraries | beautifulsoup4, requests | Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions. |

## Modules

Each module has one owner concern and a documented way to replace it.

| Module | Owns | How to replace it |
| --- | --- | --- |
| Data and identity | crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence) | Keep stable ids and a versioned repository interface; migrate storage behind it with a fixture round-trip. |
| Safe crawl boundary | Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay. | Keep the acceptance contract: The page cap stops enqueueing beyond its limit. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Extract and explain | Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links. | Keep the acceptance contract: The fixture reports its 404 link and both duplicate-title pages. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Resumable audit exports | Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages. | Keep the acceptance contract: Stopping and resuming the fixture does not create duplicate URL rows. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Operations | Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. | Change host or backup destination only after an isolated restore and authorization check. |

## Configuration

Every runtime setting is an environment variable documented in `.env.example`, validated at startup, with a safe local default wherever one exists.

- `DATA_DIR` · required · A new private folder this application creates on first run; never serve it as static files.
- `SECRET_KEY` · required, secret · Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
- `APP_MODE` · required · Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
- `SITE_URL` · required · The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.

## Production baseline

- Security: least privilege, input validation at every boundary, secret redaction in logs, rate limits on abuse-prone paths, no invented security primitives.
- Data: explicit schema and migrations, transactional writes where integrity matters, backup and restore procedures that have been exercised.
- Integrations: adapters around third-party providers, idempotent webhook or job processing, bounded retries, timeouts.
- Observability: structured logs with request or operation ids, an error-tracking hook, and health and readiness checks where a server exists.
- Quality: unit tests for domain rules, integration tests at module boundaries, one end-to-end test of the critical path.

## Decision records

For each dependency in the stack table, keep a short note: why it was chosen, its failure mode, and how it is replaced. Do not add infrastructure until a requirement in `PRODUCT.md` justifies it.

===== AGENTS.md =====
# Agent instructions · Screaming Frog SEO Spider product build

- Read `PRODUCT.md` and `ARCHITECTURE.md` before changing code. The stack is fixed: Python 3.12+ and Flask, SQLite through Python sqlite3, Jinja HTML templates, CSS and vanilla JavaScript, Python unittest and browser acceptance fixtures, beautifulsoup4, requests.
- Implement milestone by milestone from `MILESTONES.md`; keep each change reviewable and leave the application runnable at every commit.
- Treat authentication, payments, encryption, imports, webhooks and destructive actions as high-risk boundaries when present.
- Never invent cryptography or silently weaken a requirement to make a check pass.
- Put every external service behind an interface with a deterministic fake for tests.
- Add migrations and rollback or recovery notes for every persistent data change.
- Log useful operational context without credentials, tokens, passwords or personal data.
- Update documentation and run every check before completing a milestone.

## Known traps

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- Do not treat canonical declarations as redirects or guaranteed indexing behavior.
- Network errors and blocked pages need an unknown state rather than an invented success score.
- Export without an import or restore rehearsal is not verified portability.
- Product mode is additional engineering, not a switch that makes a local prototype production-ready.

===== MILESTONES.md =====
# Delivery milestones · Screaming Frog SEO Spider

Estimated effort: **multi-day** for the indie phases; the production-only milestones add the trust and operability layer.

## M1 · Local foundation and data contract

Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

### Steps

1. Create and start the local application
   Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch.
   Files: `app.py`, `requirements.txt`, `.env.example`, `.gitignore`

   ```sh
   python -m venv .venv
   python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
   python -m pip freeze > requirements.txt
   python -m flask --app app run --host 127.0.0.1
   ```

2. Implement storage and seed the named fixture
   For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data.
   Files: `schema.sql`, `db.py`, `manage.py`, `fixtures/README.md`

   ```sh
   python manage.py init
   python manage.py seed
   ```

3. Protect the local request boundary
   Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
   Files: `app.py`, `templates/base.html`, `test/test_foundation.py`

### Done when

- [ ] The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000.
- [ ] Restarting preserves the seeded records or canonical files; running init again deletes nothing.
- [ ] A cross-origin state-changing request to an admin route is refused.

### Watch out

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

## M2 · Safe crawl boundary

Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

### Steps

1. Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Files: `features/safe_crawl_boundary.py`, `templates/safe_crawl_boundary.html`
2. Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Files: `features/safe_crawl_boundary.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_safe_crawl_boundary.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] In normal mode a redirect to a private address is refused before fetching it.

### Watch out

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

## M3 · Extract and explain

Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

### Steps

1. Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Files: `features/extract_and_explain.py`, `templates/extract_and_explain.html`
2. Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Files: `features/extract_and_explain.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_extract_and_explain.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] A noindex page is reported as noindex, not automatically classified as an error.

### Watch out

- Do not treat canonical declarations as redirects or guaranteed indexing behavior.

## M4 · Resumable audit exports

Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

### Steps

1. Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Files: `features/resumable_audit_exports.py`, `templates/resumable_audit_exports.html`
2. Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Files: `features/resumable_audit_exports.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_resumable_audit_exports.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] Each reported finding can be reproduced from its saved evidence.

### Watch out

- Network errors and blocked pages need an unknown state rather than an invented success score.

## M5 · Portable delivery and clean-start proof

Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

### Steps

1. Write the user-facing runbook
   Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
   Files: `README.md`, `.env.example`
2. Create and rehearse a recoverable backup
   Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
   Files: `OPERATIONS.md`, `scripts/backup.py`
3. Reproduce the first-run experience
   Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete.
   Files: `README.md`, `verification.md`

   ```sh
   python -m pip install -r requirements.txt
   python -m unittest discover -s test
   ```


### Done when

- [ ] A new folder reaches the documented fixture outcome using only README instructions.
- [ ] A backup restored in isolation preserves the proof data and can be opened.

### Watch out

- Export without an import or restore rehearsal is not verified portability.

## M6 · Operate and share with access controls (production only)

Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

### Steps

1. Establish owner access before exposure
   Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
   Files: `ARCHITECTURE.md`, `OPERATIONS.md`
2. Deploy a monitored service
   Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them.
   Files: `Caddyfile`, `OPERATIONS.md`

   ```sh
   waitress-serve --listen=127.0.0.1:5000 app:app
   ```

3. Rehearse loss and recovery
   Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
   Files: `OPERATIONS.md`, `release-checklist.md`

### Done when

- [ ] An unauthenticated visitor cannot read private records, download private files or mutate the admin surface.
- [ ] A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries.
- [ ] Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.

### Watch out

- Product mode is additional engineering, not a switch that makes a local prototype production-ready.

===== OPERATIONS.md =====
# Operations · Screaming Frog SEO Spider

## Backup

Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider.

## Restore

Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.

Do a restore drill before the first real user, and write the date here when it passes.

## Monitoring

Check HTTP availability, free disk, backup age and domain failures for Safe crawl boundary, Extract and explain, Resumable audit exports. Alert without logging private payloads.

## Incident checklist

Pause outbound jobs and public intake as appropriate, preserve redacted diagnostics, restore an isolated verified backup, rotate affected credentials and reconcile uncertain effects before reopening.

1. Contain the issue without destroying evidence or user data.
2. Record the timeline and affected scope.
3. Rotate exposed secrets and revoke compromised sessions or credentials.
4. Restore from a verified backup when needed.
5. Document the root cause, the remediation and the regression test.

## Release gate

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] A private-data authorization check passes using a second identity.
- [ ] An off-host restore drill has a date, observed result and recovery time in OPERATIONS.md.
- [ ] README names the excluded vendor capabilities and actual provider/hosting costs.

## Launch constraint

Do not market omitted Screaming Frog SEO Spider capabilities as implemented. The non-goals in `PRODUCT.md` remain user-visible limitations until they are deliberately delivered.

===== .env.example =====
# Copy to .env and fill in. Never commit .env; this file documents it.

# Required. A new private folder this application creates on first run; never serve it as static files.
DATA_DIR=./data/screaming-frog-seo-spider

# Required · secret. Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
SECRET_KEY=replace-with-a-random-secret

# Required. Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
APP_MODE=indie

# Required. The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
SITE_URL=http://127.0.0.1:5000

# Screaming Frog SEO Spider · indie build

Build a bounded crawler for an owned site with evidence-based technical reports.

Estimated effort: **multi-day**. Work `BUILD_PLAN.md` top to bottom · every phase ends in a check that has to pass before the next one starts.

## Stack

| Part | Choice | Why |
| --- | --- | --- |
| Runtime | Python 3.12+ and Flask | A small local HTTP application with readable server-side handlers and no JavaScript build pipeline. |
| Storage | SQLite through Python sqlite3 | Local ownership with explicit transactions and a portable backup path. |
| Interface | Jinja HTML templates, CSS and vanilla JavaScript | Implement the specified screens directly with labelled controls and progressive enhancement. |
| Verification | Python unittest and browser acceptance fixtures | Check invariants and the actual user workflow before the next phase. |
| Focused libraries | beautifulsoup4, requests | Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions. |

## Before you start

Have every one of these ready. The plan assumes them from step one.

- [ ] **Python 3.12 or newer and a terminal** · Python is free; this local prototype requires no hosting subscription.
  - Why: The local backend, tests and storage use Python.
  - Get it: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages.
  - Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds.
- [ ] **A current desktop browser and text editor** · No paid service required for this local step.
  - Why: You need to view the local interface and edit generated project files.
  - Get it: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository.
  - Verify: You can create a text file in the project folder and open browser developer tools.
- [ ] **Screaming Frog SEO Spider acceptance sample** · No paid service required for this local step.
  - Why: This fixture makes the first end-to-end check reproducible.
  - Get it: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records.
  - Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account.
- [ ] **Confirm the bounded replacement** · No paid service required for this local step.
  - Why: The full commercial product is larger than this guide.
  - Get it: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first.
  - Verify: You can name the primary workflow and the vendor features this version deliberately leaves out.

## Quick start

```sh
python -m venv .venv
python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
python -m pip freeze > requirements.txt
python -m flask --app app run --host 127.0.0.1
```

Then copy `.env.example` to `.env` and fill in the values it documents.

## Honest limits

This build deliberately does not replace:

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

If one of those is essential to you, that is the reason to keep paying for Screaming Frog SEO Spider, and the README should say so rather than pretend.

# Build brief · Screaming Frog SEO Spider

The one-shot brief this plan expands. `BUILD_PLAN.md` (or `MILESTONES.md`) is the same sequence broken into steps and checks; where the two disagree, the plan wins.

Build me a bounded crawler for an owned site with evidence-based technical reports as a bounded replacement for Screaming Frog SEO Spider.
Build it in phases in the order below. Do not write the whole product in one pass.
Finish the current phase, run its Done when checks, fix failures, then continue.
Indie mode completes Phases 1-5. Phase 6 is required before shared or public deployment.

### Stack (fixed, do not substitute)
- Runtime: Python 3.12+ and Flask. A small local HTTP application with readable server-side handlers and no JavaScript build pipeline.
- Storage: SQLite through Python sqlite3. Local ownership with explicit transactions and a portable backup path.
- Interface: Jinja HTML templates, CSS and vanilla JavaScript. Implement the specified screens directly with labelled controls and progressive enhancement.
- Verification: Python unittest and browser acceptance fixtures. Check invariants and the actual user workflow before the next phase.
- Focused libraries: beautifulsoup4, requests. Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions.

### Data model (create this before Phase 1)
- crawls(id,origin,started_at,limit,state)
- urls(id,crawl_id,url,status,content_type,title,canonical,depth,error)
- edges(source_id,target_url)
- findings(id,url_id,rule,evidence)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address.

### Prerequisites and configuration
- Python 3.12 or newer and a terminal: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages. Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds. Cost: Python is free; this local prototype requires no hosting subscription.
- A current desktop browser and text editor: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository. Verify: You can create a text file in the project folder and open browser developer tools. Cost: No paid service required for this local step.
- Screaming Frog SEO Spider acceptance sample: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records. Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account. Cost: No paid service required for this local step.
- Confirm the bounded replacement: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first. Verify: You can name the primary workflow and the vendor features this version deliberately leaves out. Cost: No paid service required for this local step.
- Configuration: DATA_DIR, SECRET_KEY, APP_MODE, SITE_URL. Ship .env.example, replace placeholders and exclude secrets from git.

### Phase 1 · Local foundation and data contract
Build: Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

- Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch. Commands, after creating the named files: `python -m venv .venv`; `python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests`; `python -m pip freeze > requirements.txt`; `python -m flask --app app run --host 127.0.0.1`.
- For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data. Commands, after creating the named files: `python manage.py init`; `python manage.py seed`.
- Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
- Trap: The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

Done when: The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000. Restarting preserves the seeded records or canonical files; running init again deletes nothing. A cross-origin state-changing request to an admin route is refused.
Do not build yet: Do not start safe crawl boundary until these checks pass.

### Phase 2 · Safe crawl boundary
Build: Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

- Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
- Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

Done when: The page cap stops enqueueing beyond its limit. In normal mode a redirect to a private address is refused before fetching it.
Do not build yet: Do not start extract and explain until these checks pass.

### Phase 3 · Extract and explain
Build: Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

- Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
- Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Do not treat canonical declarations as redirects or guaranteed indexing behavior.

Done when: The fixture reports its 404 link and both duplicate-title pages. A noindex page is reported as noindex, not automatically classified as an error.
Do not build yet: Do not start resumable audit exports until these checks pass.

### Phase 4 · Resumable audit exports
Build: Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

- Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
- Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Network errors and blocked pages need an unknown state rather than an invented success score.

Done when: Stopping and resuming the fixture does not create duplicate URL rows. Each reported finding can be reproduced from its saved evidence.
Do not build yet: Do not start portable delivery and clean-start proof until these checks pass.

### Phase 5 · Portable delivery and clean-start proof
Build: Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

- Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
- Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
- Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete. Commands, after creating the named files: `python -m pip install -r requirements.txt`; `python -m unittest discover -s test`.
- Trap: Export without an import or restore rehearsal is not verified portability.

Done when: A new folder reaches the documented fixture outcome using only README instructions. A backup restored in isolation preserves the proof data and can be opened.
Do not build yet: Do not start operate and share with access controls until these checks pass.

### Phase 6 · Operate and share with access controls (product-builder only)
Build: Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

- Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
- Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them. Commands, after creating the named files: `waitress-serve --listen=127.0.0.1:5000 app:app`.
- Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
- Trap: Product mode is additional engineering, not a switch that makes a local prototype production-ready.

Done when: An unauthenticated visitor cannot read private records, download private files or mutate the admin surface. A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries. Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.
Do not build yet: Do not add new providers or vendor-scale features until the release gates are recorded.

### Out of scope (and why)
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance: retain the paid product if this capability is essential; it is outside this bounded build.
- massive hosted crawl capacity: retain the paid product if this capability is essential; it is outside this bounded build.
- proprietary scoring: retain the paid product if this capability is essential; it is outside this bounded build.
- continuous monitoring: retain the paid product if this capability is essential; it is outside this bounded build.
- agency reporting and support: retain the paid product if this capability is essential; it is outside this bounded build.

### README must contain
- Exact install, configure, initialize, start, test and recovery commands for a clean folder.
- The schema, fixture, acceptance results, private data locations and export format.
- Every prerequisite and secret source, actual running costs and deliberately excluded capabilities.
- An honest distinction between tests actually run and checks still awaiting real credentials or deployment.
- Dependency documentation reviewed 2026-09-05: https://flask.palletsprojects.com/en/stable/installation/ ; https://docs.python.org/3/library/sqlite3.html ; https://flask-wtf.readthedocs.io/en/1.2.x/csrf/ ; https://docs.pylonsproject.org/projects/waitress/en/stable/usage.html. Recheck before upgrading; freeze the versions actually tested.

# Agent instructions · Screaming Frog SEO Spider indie build

- Read `README.md` and `BUILD_PLAN.md` before writing code. The stack is fixed: Python 3.12+ and Flask, SQLite through Python sqlite3, Jinja HTML templates, CSS and vanilla JavaScript, Python unittest and browser acceptance fixtures, beautifulsoup4, requests. Do not substitute.
- Work one phase at a time, in order. Do not start a phase until every "Done when" item of the previous one passes.
- Prefer the fewest moving parts that satisfy the step. No frameworks, services or dependencies the plan does not name.
- Secrets live in `.env`, never in source or logs. Keep `.env.example` current when a variable is introduced.
- Do not invent cryptography, security guarantees, APIs or compliance claims.
- Add a focused test for every destructive, security-sensitive or data-loss path the plan names.
- Run the project checks before declaring a phase complete, and record any deliberate shortcut in the README under "Tradeoffs".

## Known traps

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- Do not treat canonical declarations as redirects or guaranteed indexing behavior.
- Network errors and blocked pages need an unknown state rather than an invented success score.
- Export without an import or restore rehearsal is not verified portability.

# Build plan · Screaming Frog SEO Spider

Build a bounded crawler for an owned site with evidence-based technical reports.

Phases are in dependency order. Each ends in a "Done when" list; treat an unticked item as a blocker, not a note.

## Phase 1 · Local foundation and data contract

Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

### Steps

1. Create and start the local application
   Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch.
   Files: `app.py`, `requirements.txt`, `.env.example`, `.gitignore`

   ```sh
   python -m venv .venv
   python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
   python -m pip freeze > requirements.txt
   python -m flask --app app run --host 127.0.0.1
   ```

2. Implement storage and seed the named fixture
   For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data.
   Files: `schema.sql`, `db.py`, `manage.py`, `fixtures/README.md`

   ```sh
   python manage.py init
   python manage.py seed
   ```

3. Protect the local request boundary
   Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
   Files: `app.py`, `templates/base.html`, `test/test_foundation.py`

### Done when

- [ ] The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000.
- [ ] Restarting preserves the seeded records or canonical files; running init again deletes nothing.
- [ ] A cross-origin state-changing request to an admin route is refused.

### Watch out

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

## Phase 2 · Safe crawl boundary

Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

### Steps

1. Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Files: `features/safe_crawl_boundary.py`, `templates/safe_crawl_boundary.html`
2. Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Files: `features/safe_crawl_boundary.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_safe_crawl_boundary.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] In normal mode a redirect to a private address is refused before fetching it.

### Watch out

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

## Phase 3 · Extract and explain

Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

### Steps

1. Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Files: `features/extract_and_explain.py`, `templates/extract_and_explain.html`
2. Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Files: `features/extract_and_explain.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_extract_and_explain.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] A noindex page is reported as noindex, not automatically classified as an error.

### Watch out

- Do not treat canonical declarations as redirects or guaranteed indexing behavior.

## Phase 4 · Resumable audit exports

Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

### Steps

1. Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Files: `features/resumable_audit_exports.py`, `templates/resumable_audit_exports.html`
2. Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Files: `features/resumable_audit_exports.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_resumable_audit_exports.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] Each reported finding can be reproduced from its saved evidence.

### Watch out

- Network errors and blocked pages need an unknown state rather than an invented success score.

## Phase 5 · Portable delivery and clean-start proof

Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

### Steps

1. Write the user-facing runbook
   Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
   Files: `README.md`, `.env.example`
2. Create and rehearse a recoverable backup
   Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
   Files: `OPERATIONS.md`, `scripts/backup.py`
3. Reproduce the first-run experience
   Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete.
   Files: `README.md`, `verification.md`

   ```sh
   python -m pip install -r requirements.txt
   python -m unittest discover -s test
   ```


### Done when

- [ ] A new folder reaches the documented fixture outcome using only README instructions.
- [ ] A backup restored in isolation preserves the proof data and can be opened.

### Watch out

- Export without an import or restore rehearsal is not verified portability.

## Not in this build

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

## After v1, if you want it

- Extend resumable audit exports only after the fixture and recovery checks pass.
- Before adding another integration, document its credentials, limits, cost and failure behavior with primary-source links.

# Copy to .env and fill in. Never commit .env; this file documents it.

# Required. A new private folder this application creates on first run; never serve it as static files.
DATA_DIR=./data/screaming-frog-seo-spider

# Required · secret. Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
SECRET_KEY=replace-with-a-random-secret

# Required. Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
APP_MODE=indie

# Required. The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
SITE_URL=http://127.0.0.1:5000

# Screaming Frog SEO Spider · product brief

## Problem

The core loop is small enough for a capable coding agent to produce a useful local version in one sitting. For Screaming Frog SEO Spider, crawl an owned site locally, inspect technical signals, and export raw audit data. The hard boundary is years of crawl edge cases, javascript rendering, integrations, and desktop performance, plus crawl scale, rule depth, and operational polish.

## Product outcome

An operated version of a bounded crawler for an owned site with evidence-based technical reports, with authorized access, restore evidence and honest scope limits.

## Target user

A builder who needs a maintainable product foundation, not a one-off demo.

## Required capabilities

- Python 3.12
- Playwright browsers
- permission to crawl the target site
- local disk space

## Explicit non-goals for v1

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance
- massive hosted crawl capacity
- proprietary scoring
- continuous monitoring
- agency reporting and support

## Success criteria

- The page cap stops enqueueing beyond its limit.
- The fixture reports its 404 link and both duplicate-title pages.
- Stopping and resuming the fixture does not create duplicate URL rows.
- A private-data authorization check passes using a second identity.
- An off-host restore drill has a date, observed result and recovery time in OPERATIONS.md.
- README names the excluded vendor capabilities and actual provider/hosting costs.

# Build brief · Screaming Frog SEO Spider

The one-shot brief this plan expands. `BUILD_PLAN.md` (or `MILESTONES.md`) is the same sequence broken into steps and checks; where the two disagree, the plan wins.

Build me a bounded crawler for an owned site with evidence-based technical reports as a bounded replacement for Screaming Frog SEO Spider.
Build it in phases in the order below. Do not write the whole product in one pass.
Finish the current phase, run its Done when checks, fix failures, then continue.
Indie mode completes Phases 1-5. Phase 6 is required before shared or public deployment.

### Stack (fixed, do not substitute)
- Runtime: Python 3.12+ and Flask. A small local HTTP application with readable server-side handlers and no JavaScript build pipeline.
- Storage: SQLite through Python sqlite3. Local ownership with explicit transactions and a portable backup path.
- Interface: Jinja HTML templates, CSS and vanilla JavaScript. Implement the specified screens directly with labelled controls and progressive enhancement.
- Verification: Python unittest and browser acceptance fixtures. Check invariants and the actual user workflow before the next phase.
- Focused libraries: beautifulsoup4, requests. Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions.

### Data model (create this before Phase 1)
- crawls(id,origin,started_at,limit,state)
- urls(id,crawl_id,url,status,content_type,title,canonical,depth,error)
- edges(source_id,target_url)
- findings(id,url_id,rule,evidence)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address.

### Prerequisites and configuration
- Python 3.12 or newer and a terminal: Install Python from python.org. Open a terminal in a new empty project folder. On Windows, use py -3 where this guide says python if python is not on PATH; on macOS/Linux use python3 if needed. Create .venv and activate it before installing packages. Verify: python --version reports 3.12+ and python -c "import sqlite3" succeeds. Cost: Python is free; this local prototype requires no hosting subscription.
- A current desktop browser and text editor: Use an installed Chrome, Firefox or Edge browser. Open the empty project folder in your editor; open the terminal there, not in this catalog repository. Verify: You can create a text file in the project folder and open browser developer tools. Cost: No paid service required for this local step.
- Screaming Frog SEO Spider acceptance sample: Create synthetic sample data before implementation: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Save it under fixtures/ with the expected results in fixtures/README.md; use no real credentials or customer records. Verify: The fixture files and expected outcomes exist and can be inspected without a vendor account. Cost: No paid service required for this local step.
- Confirm the bounded replacement: The deliverable is a bounded crawler for an owned site with evidence-based technical reports. Read every exclusion below. Indie mode runs locally; any public or shared use requires the product access and deployment gates first. Verify: You can name the primary workflow and the vendor features this version deliberately leaves out. Cost: No paid service required for this local step.
- Configuration: DATA_DIR, SECRET_KEY, APP_MODE, SITE_URL. Ship .env.example, replace placeholders and exclude secrets from git.

### Phase 1 · Local foundation and data contract
Build: Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

- Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch. Commands, after creating the named files: `python -m venv .venv`; `python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests`; `python -m pip freeze > requirements.txt`; `python -m flask --app app run --host 127.0.0.1`.
- For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data. Commands, after creating the named files: `python manage.py init`; `python manage.py seed`.
- Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
- Trap: The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

Done when: The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000. Restarting preserves the seeded records or canonical files; running init again deletes nothing. A cross-origin state-changing request to an admin route is refused.
Do not build yet: Do not start safe crawl boundary until these checks pass.

### Phase 2 · Safe crawl boundary
Build: Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

- Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
- Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

Done when: The page cap stops enqueueing beyond its limit. In normal mode a redirect to a private address is refused before fetching it.
Do not build yet: Do not start extract and explain until these checks pass.

### Phase 3 · Extract and explain
Build: Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

- Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
- Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Do not treat canonical declarations as redirects or guaranteed indexing behavior.

Done when: The fixture reports its 404 link and both duplicate-title pages. A noindex page is reported as noindex, not automatically classified as an error.
Do not build yet: Do not start resumable audit exports until these checks pass.

### Phase 4 · Resumable audit exports
Build: Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

- Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
- Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
- Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser. Commands, after creating the named files: `python -m unittest discover -s test`.
- Trap: Network errors and blocked pages need an unknown state rather than an invented success score.

Done when: Stopping and resuming the fixture does not create duplicate URL rows. Each reported finding can be reproduced from its saved evidence.
Do not build yet: Do not start portable delivery and clean-start proof until these checks pass.

### Phase 5 · Portable delivery and clean-start proof
Build: Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

- Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
- Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
- Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete. Commands, after creating the named files: `python -m pip install -r requirements.txt`; `python -m unittest discover -s test`.
- Trap: Export without an import or restore rehearsal is not verified portability.

Done when: A new folder reaches the documented fixture outcome using only README instructions. A backup restored in isolation preserves the proof data and can be opened.
Do not build yet: Do not start operate and share with access controls until these checks pass.

### Phase 6 · Operate and share with access controls (product-builder only)
Build: Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

- Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
- Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them. Commands, after creating the named files: `waitress-serve --listen=127.0.0.1:5000 app:app`.
- Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
- Trap: Product mode is additional engineering, not a switch that makes a local prototype production-ready.

Done when: An unauthenticated visitor cannot read private records, download private files or mutate the admin surface. A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries. Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.
Do not build yet: Do not add new providers or vendor-scale features until the release gates are recorded.

### Out of scope (and why)
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- This is a bounded crawler for an owned site with evidence-based technical reports; full Screaming Frog SEO Spider feature parity, vendor hosting and support are not included.
- years of crawl edge cases, JavaScript rendering, integrations, and desktop performance: retain the paid product if this capability is essential; it is outside this bounded build.
- massive hosted crawl capacity: retain the paid product if this capability is essential; it is outside this bounded build.
- proprietary scoring: retain the paid product if this capability is essential; it is outside this bounded build.
- continuous monitoring: retain the paid product if this capability is essential; it is outside this bounded build.
- agency reporting and support: retain the paid product if this capability is essential; it is outside this bounded build.

### README must contain
- Exact install, configure, initialize, start, test and recovery commands for a clean folder.
- The schema, fixture, acceptance results, private data locations and export format.
- Every prerequisite and secret source, actual running costs and deliberately excluded capabilities.
- An honest distinction between tests actually run and checks still awaiting real credentials or deployment.
- Dependency documentation reviewed 2026-09-05: https://flask.palletsprojects.com/en/stable/installation/ ; https://docs.python.org/3/library/sqlite3.html ; https://flask-wtf.readthedocs.io/en/1.2.x/csrf/ ; https://docs.pylonsproject.org/projects/waitress/en/stable/usage.html. Recheck before upgrading; freeze the versions actually tested.

# Architecture · Screaming Frog SEO Spider

## Stack

| Part | Choice | Why |
| --- | --- | --- |
| Runtime | Python 3.12+ and Flask | A small local HTTP application with readable server-side handlers and no JavaScript build pipeline. |
| Storage | SQLite through Python sqlite3 | Local ownership with explicit transactions and a portable backup path. |
| Interface | Jinja HTML templates, CSS and vanilla JavaScript | Implement the specified screens directly with labelled controls and progressive enhancement. |
| Verification | Python unittest and browser acceptance fixtures | Check invariants and the actual user workflow before the next phase. |
| Focused libraries | beautifulsoup4, requests | Use these only for the specific file, parsing or provider operations named in the phases; freeze tested versions. |

## Modules

Each module has one owner concern and a documented way to replace it.

| Module | Owns | How to replace it |
| --- | --- | --- |
| Data and identity | crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence) | Keep stable ids and a versioned repository interface; migrate storage behind it with a fixture round-trip. |
| Safe crawl boundary | Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay. | Keep the acceptance contract: The page cap stops enqueueing beyond its limit. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Extract and explain | Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links. | Keep the acceptance contract: The fixture reports its 404 link and both duplicate-title pages. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Resumable audit exports | Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages. | Keep the acceptance contract: Stopping and resuming the fixture does not create duplicate URL rows. Replace only this module after replaying its fixture; preserve ids and existing records. |
| Operations | Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. | Change host or backup destination only after an isolated restore and authorization check. |

## Configuration

Every runtime setting is an environment variable documented in `.env.example`, validated at startup, with a safe local default wherever one exists.

- `DATA_DIR` · required · A new private folder this application creates on first run; never serve it as static files.
- `SECRET_KEY` · required, secret · Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
- `APP_MODE` · required · Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
- `SITE_URL` · required · The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.

## Production baseline

- Security: least privilege, input validation at every boundary, secret redaction in logs, rate limits on abuse-prone paths, no invented security primitives.
- Data: explicit schema and migrations, transactional writes where integrity matters, backup and restore procedures that have been exercised.
- Integrations: adapters around third-party providers, idempotent webhook or job processing, bounded retries, timeouts.
- Observability: structured logs with request or operation ids, an error-tracking hook, and health and readiness checks where a server exists.
- Quality: unit tests for domain rules, integration tests at module boundaries, one end-to-end test of the critical path.

## Decision records

For each dependency in the stack table, keep a short note: why it was chosen, its failure mode, and how it is replaced. Do not add infrastructure until a requirement in `PRODUCT.md` justifies it.

# Agent instructions · Screaming Frog SEO Spider product build

- Read `PRODUCT.md` and `ARCHITECTURE.md` before changing code. The stack is fixed: Python 3.12+ and Flask, SQLite through Python sqlite3, Jinja HTML templates, CSS and vanilla JavaScript, Python unittest and browser acceptance fixtures, beautifulsoup4, requests.
- Implement milestone by milestone from `MILESTONES.md`; keep each change reviewable and leave the application runnable at every commit.
- Treat authentication, payments, encryption, imports, webhooks and destructive actions as high-risk boundaries when present.
- Never invent cryptography or silently weaken a requirement to make a check pass.
- Put every external service behind an interface with a deterministic fake for tests.
- Add migrations and rollback or recovery notes for every persistent data change.
- Log useful operational context without credentials, tokens, passwords or personal data.
- Update documentation and run every check before completing a milestone.

## Known traps

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.
- Do not treat canonical declarations as redirects or guaranteed indexing behavior.
- Network errors and blocked pages need an unknown state rather than an invented success score.
- Export without an import or restore rehearsal is not verified portability.
- Product mode is additional engineering, not a switch that makes a local prototype production-ready.

# Delivery milestones · Screaming Frog SEO Spider

Estimated effort: **multi-day** for the indie phases; the production-only milestones add the trust and operability layer.

## M1 · Local foundation and data contract

Create the runnable local foundation for a bounded crawler for an owned site with evidence-based technical reports, including the real schema and acceptance fixture.

### Steps

1. Create and start the local application
   Run the venv command first, then stop and activate it before running the remaining commands. Use your OS instructions: Windows .venv\Scripts\activate.bat in cmd, or .venv\Scripts\Activate.ps1 in PowerShell; macOS/Linux source .venv/bin/activate. Then install the listed packages. Create app.py exposing app, load .env with python-dotenv, and add a /healthz route. Freeze tested dependency versions to requirements.txt. Create .env manually from .env.example; replace SECRET_KEY before launch.
   Files: `app.py`, `requirements.txt`, `.env.example`, `.gitignore`

   ```sh
   python -m venv .venv
   python -m pip install Flask Flask-WTF python-dotenv waitress tzdata beautifulsoup4 requests
   python -m pip freeze > requirements.txt
   python -m flask --app app run --host 127.0.0.1
   ```

2. Implement storage and seed the named fixture
   For database-backed state create schema.sql and db.py using this model: crawls(id,origin,started_at,limit,state); urls(id,crawl_id,url,status,content_type,title,canonical,depth,error); edges(source_id,target_url); findings(id,url_id,rule,evidence). Add the auxiliary relationships explicitly used in later phases; use stable ids, foreign keys, parameterized values and transactions. For canonical files use atomic replacement and hashes instead. Implement python manage.py init and python manage.py seed to create only synthetic data: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Re-running init must not erase data.
   Files: `schema.sql`, `db.py`, `manage.py`, `fixtures/README.md`

   ```sh
   python manage.py init
   python manage.py seed
   ```

3. Protect the local request boundary
   Install Flask-WTF CSRF protection for forms and same-origin fetches, validate Host and Origin against SITE_URL, bound inputs and escape output. Deliberately public intake endpoints get bounded validation and rate limits; signed provider webhooks use signature checks instead of browser CSRF tokens. All other admin routes stay local until product authentication exists. When a later phase tests viewer/member permissions, implement the users, hashed passwords, expiring server sessions and role checks in this foundation first; product mode must never use a fabricated identity from request input. Add error, empty, keyboard-focus and retry states now.
   Files: `app.py`, `templates/base.html`, `test/test_foundation.py`

### Done when

- [ ] The documented start command serves /healthz and the initial screen at http://127.0.0.1:5000.
- [ ] Restarting preserves the seeded records or canonical files; running init again deletes nothing.
- [ ] A cross-origin state-changing request to an admin route is refused.

### Watch out

- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.

## M2 · Safe crawl boundary

Safe crawl boundary for Screaming Frog SEO Spider: Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.

### Steps

1. Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Require an explicit owned origin and page cap; honor robots.txt, use one worker and a configurable delay.
   Files: `features/safe_crawl_boundary.py`, `templates/safe_crawl_boundary.html`
2. Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Normalize fragments, limit response size/time and recheck DNS plus destination scope on every redirect; provide a test-only loopback mode.
   Files: `features/safe_crawl_boundary.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The page cap stops enqueueing beyond its limit. Then check: In normal mode a redirect to a private address is refused before fetching it. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_safe_crawl_boundary.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] In normal mode a redirect to a private address is refused before fetching it.

### Watch out

- This is an HTTP HTML crawler, not a JavaScript rendering browser or an internet scanner.

## M3 · Extract and explain

Extract and explain for Screaming Frog SEO Spider: Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.

### Steps

1. Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Use an HTML parser to extract titles, descriptions, headings, canonical and robots metadata and internal links.
   Files: `features/extract_and_explain.py`, `templates/extract_and_explain.html`
2. Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Implement missing/duplicate title, broken internal link and conflicting canonical rules with source URL and raw evidence.
   Files: `features/extract_and_explain.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: The fixture reports its 404 link and both duplicate-title pages. Then check: A noindex page is reported as noindex, not automatically classified as an error. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_extract_and_explain.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] A noindex page is reported as noindex, not automatically classified as an error.

### Watch out

- Do not treat canonical declarations as redirects or guaranteed indexing behavior.

## M4 · Resumable audit exports

Resumable audit exports for Screaming Frog SEO Spider: Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.

### Steps

1. Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Persist the queue and visited URL set so a stopped crawl can resume without refetching completed pages.
   Files: `features/resumable_audit_exports.py`, `templates/resumable_audit_exports.html`
2. Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Export raw URL and edge CSV plus findings with the rule version and crawl timestamp.
   Files: `features/resumable_audit_exports.py`
3. Exercise the acceptance fixture
   Use A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Check: Stopping and resuming the fixture does not create duplicate URL rows. Then check: Each reported finding can be reproduced from its saved evidence. Add a focused regression for the failure case under test/ using a temporary database or folder and fake external services; also perform the visible workflow in a browser.
   Files: `test/test_resumable_audit_exports.py`

   ```sh
   python -m unittest discover -s test
   ```


### Done when

- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] Each reported finding can be reproduced from its saved evidence.

### Watch out

- Network errors and blocked pages need an unknown state rather than an invented success score.

## M5 · Portable delivery and clean-start proof

Finish the Screaming Frog SEO Spider replacement with a documented first-run path and a recoverable export.

### Steps

1. Write the user-facing runbook
   Document prerequisites, every configuration variable, data locations and the three domain workflows: Safe crawl boundary; Extract and explain; Resumable audit exports. Include the exclusions, actual costs and source check date 2026-09-05. Commands shown earlier that reference project files are files the builder must implement before running them.
   Files: `README.md`, `.env.example`
2. Create and rehearse a recoverable backup
   Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
   Files: `OPERATIONS.md`, `scripts/backup.py`
3. Reproduce the first-run experience
   Use a new folder and only README instructions to reach the fixture outcome. Install from requirements.txt, initialize storage, run the tests and exercise the UI at 375px and 1280px; use keyboard-only controls and inspect browser errors. Record exactly what passed; do not mark unrun checks complete.
   Files: `README.md`, `verification.md`

   ```sh
   python -m pip install -r requirements.txt
   python -m unittest discover -s test
   ```


### Done when

- [ ] A new folder reaches the documented fixture outcome using only README instructions.
- [ ] A backup restored in isolation preserves the proof data and can be opened.

### Watch out

- Export without an import or restore rehearsal is not verified portability.

## M6 · Operate and share with access controls (production only)

Product-builder only: make a bounded crawler for an owned site with evidence-based technical reports operable for its stated audience before allowing remote access.

### Steps

1. Establish owner access before exposure
   Add owner/member/viewer authorization as appropriate, password hashes through Werkzeug, expiring server-side sessions, CSRF and login rate limits. Add users, sessions and audit schema migrations plus an owner-init command prompting securely for its password. Enforce ownership on every private read/write/download and fail closed when product setup is incomplete. Existing learner or admin identities must use this same boundary.
   Files: `ARCHITECTURE.md`, `OPERATIONS.md`
2. Deploy a monitored service
   Serve app:app with Waitress on loopback behind Caddy HTTPS. Configure trusted proxy headers narrowly, Secure/HttpOnly/SameSite cookies, upload limits, request ids and structured logs without private content. Run background jobs as a separate supervised process when the domain workflow requires them.
   Files: `Caddyfile`, `OPERATIONS.md`

   ```sh
   waitress-serve --listen=127.0.0.1:5000 app:app
   ```

3. Rehearse loss and recovery
   Add a scheduled encrypted off-host backup using this procedure: Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider. Monitor health, disk space, failed jobs and backup age. Stop the service to test an alert; rehearse recovery with outbound effects disabled and record recovery time. Rotate any exposed credentials and require reconciliation before resuming queues.
   Files: `OPERATIONS.md`, `release-checklist.md`

### Done when

- [ ] An unauthenticated visitor cannot read private records, download private files or mutate the admin surface.
- [ ] A viewer cannot mutate data by making a direct request, and guessed ids cannot cross ownership boundaries.
- [ ] Stopping the service triggers the configured alert and the latest off-host backup restores the fixture in isolation.

### Watch out

- Product mode is additional engineering, not a switch that makes a local prototype production-ready.

# Operations · Screaming Frog SEO Spider

## Backup

Use sqlite3.Connection.backup for the database in DATA_DIR and pause writers while taking the matching attachment snapshot. Keep schema version, hashes and a manifest for screaming-frog-seo-spider.

## Restore

Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: A local test site with a redirect, 404 link, duplicate title, noindex page and a redirect toward a private address. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.

Do a restore drill before the first real user, and write the date here when it passes.

## Monitoring

Check HTTP availability, free disk, backup age and domain failures for Safe crawl boundary, Extract and explain, Resumable audit exports. Alert without logging private payloads.

## Incident checklist

Pause outbound jobs and public intake as appropriate, preserve redacted diagnostics, restore an isolated verified backup, rotate affected credentials and reconcile uncertain effects before reopening.

1. Contain the issue without destroying evidence or user data.
2. Record the timeline and affected scope.
3. Rotate exposed secrets and revoke compromised sessions or credentials.
4. Restore from a verified backup when needed.
5. Document the root cause, the remediation and the regression test.

## Release gate

- [ ] The page cap stops enqueueing beyond its limit.
- [ ] The fixture reports its 404 link and both duplicate-title pages.
- [ ] Stopping and resuming the fixture does not create duplicate URL rows.
- [ ] A private-data authorization check passes using a second identity.
- [ ] An off-host restore drill has a date, observed result and recovery time in OPERATIONS.md.
- [ ] README names the excluded vendor capabilities and actual provider/hosting costs.

## Launch constraint

Do not market omitted Screaming Frog SEO Spider capabilities as implemented. The non-goals in `PRODUCT.md` remain user-visible limitations until they are deliberately delivered.

# Copy to .env and fill in. Never commit .env; this file documents it.

# Required. A new private folder this application creates on first run; never serve it as static files.
DATA_DIR=./data/screaming-frog-seo-spider

# Required · secret. Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
SECRET_KEY=replace-with-a-random-secret

# Required. Use indie for loopback-only personal work. Product mode must refuse to start until owner login and the deployment gates are configured.
APP_MODE=indie

# Required. The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
SITE_URL=http://127.0.0.1:5000

$ choose a build depth, inspect the files, then open the complete pack in your agent