Build Sentry

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Saved on this device only. Tick prerequisites first, then work the phases in order · do not start one until the checks above it pass.

Build a private error collector with deterministic grouping and one alert channel.

estimated effort multi-daythe files for this build are in the project pack

RuntimePython 3.12+ and FlaskStorageSQLite through Python sqlite3InterfaceJinja HTML templates, CSS and vanilla JavaScriptVerificationPython unittest and browser acceptance fixtures

Before step 1

Everything below is assumed from the first step. Tick each one when you actually have it, not when you plan to.

installPython 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. open ↗
Verify python --version reports 3.12+ and python -c "import sqlite3" succeeds.
installNo 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.
have readyNo 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: Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. 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.
decideNo paid service required for this local step.
Why The full commercial product is larger than this guide.
Get it The deliverable is a private error collector with deterministic grouping and one alert channel. 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.
accountProvider-specific relay fees and domain costs; no free tier or delivery guarantee is assumed.
Why Outbound confirmations or replies need a delivery provider; a fake adapter covers automated tests.
Get it Obtain SMTP host, port, username and password from your chosen relay dashboard under SMTP settings. Verify the sender/domain using that provider DNS instructions. Use only your own test recipient initially and record the actual plan and rate limit in OPERATIONS.md.
Verify The supplied smtp_probe.py sends one labelled test message to your own inbox and reports the relay response without logging credentials.

Data model

Create these before the first phase that stores anything. Changing a table later is the expensive kind of change.

- projects(id,name,ingest_key_hash)
- events(id,project_id,event_key,release,message,frames_json,at)
- issues(id,project_id,fingerprint,state)
- occurrences(event_id,issue_id)
- alert_outbox(id,issue_id,state,attempts)
- Use stable ids and explicit relationships; add auxiliary tables named by the phases before those phases use them.
- Acceptance fixture: Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context.

Environment variables

These go in a .env file the app reads at startup. The pack's .env.example is this table as a file · copy it, never commit the filled-in version.

Variable	Needed	Example	Where the value comes from
`DATA_DIR`	required	`./data/sentry`	A new private folder this application creates on first run; never serve it as static files.
`SECRET_KEY`secret	required	`replace-with-a-random-secret`	Generate with python -c "import secrets; print(secrets.token_hex(32))" and save only in .env.
`APP_MODE`	required	`indie`	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	`http://127.0.0.1:5000`	The origin used for local forms and links; replace with the chosen HTTPS origin in product mode.
`SMTP_HOST`	required	`replace-with-relay-host`	Copy the SMTP hostname from the relay dashboard.
`SMTP_PORT`	required	`587`	Use a relay supporting STARTTLS on this port; confirm it in its setup instructions.
`SMTP_USER`secret	required	`replace-with-smtp-user`	Copy the relay username; it may differ from your sign-in email.
`SMTP_PASSWORD`secret	required	`replace-with-smtp-password`	Create SMTP credentials in the relay dashboard, not your personal mailbox password.
`MAIL_FROM`	required	`owner@example.com`	Your relay-verified sender address; replace before real sends.
`MAIL_TEST_TO`	required	`owner@example.com`	An inbox you control for the explicit preflight test.

The build, in order

1
Local foundation and data contract
Create the runnable local foundation for a private error collector with deterministic grouping and one alert channel, including the real schema and acceptance fixture.
1. 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.pyrequirements.txt.env.example.gitignore
  terminal
  python -m venv .venv python -m pip install Flask Flask-WTF python-dotenv waitress tzdata python -m pip freeze > requirements.txt python -m flask --app app run --host 127.0.0.1
2. For database-backed state create schema.sql and db.py using this model: projects(id,name,ingest_key_hash); events(id,project_id,event_key,release,message,frames_json,at); issues(id,project_id,fingerprint,state); occurrences(event_id,issue_id); alert_outbox(id,issue_id,state,attempts). 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: Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. Re-running init must not erase data.
  Files schema.sqldb.pymanage.pyfixtures/README.md
  terminal
  python manage.py init python manage.py seed
3. 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.pytemplates/base.htmltest/test_foundation.py
4. Create providers/mail.py using smtplib with a timeout, verified TLS/STARTTLS and an EmailMessage. Refuse placeholder credentials and non-test recipients until the owner enables sending. Implement scripts/smtp_probe.py to send one labelled message only to MAIL_TEST_TO, and provide a fake adapter for tests. Store no password or full message body in logs.
  Files providers/mail.pyscripts/smtp_probe.py
  terminal
  python scripts/smtp_probe.py
done when · tick each as it passes
watch out
- The Flask development server is for local development only. Loopback binding alone does not replace CSRF and origin validation.
next phase
2
Bounded ingestion
Bounded ingestion for Sentry: Accept a small JSON event schema using a project-scoped ingest token and per-token limits; cap payload and frame counts.
1. Accept a small JSON event schema using a project-scoped ingest token and per-token limits; cap payload and frame counts.
  Files features/bounded_ingestion.pytemplates/bounded_ingestion.html
2. Redact configured sensitive fields before persistence and reject duplicate event ids using a unique constraint.
  Files features/bounded_ingestion.py
3. Use Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. Check: Replaying an event id stores one event. Then check: The fixture secret is absent from stored event data and request logs. 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_bounded_ingestion.py
  terminal
  python -m unittest discover -s test
done when · tick each as it passes
watch out
- Ingest credentials only permit event submission, never dashboard reads.
next phase
3
Grouping and release views
Grouping and release views for Sentry: Fingerprint normalized exception type plus top application frames; exclude timestamps and line numbers from the chosen rule.
1. Fingerprint normalized exception type plus top application frames; exclude timestamps and line numbers from the chosen rule.
  Files features/grouping_and_release_views.pytemplates/grouping_and_release_views.html
2. Show issue counts, first/last seen and releases and allow resolve/reopen; retain the grouping rule version.
  Files features/grouping_and_release_views.py
3. Use Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. Check: The two matching exceptions form one issue and the distinct exception forms another. Then check: A new occurrence after resolution reopens the issue once. 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_grouping_and_release_views.py
  terminal
  python -m unittest discover -s test
done when · tick each as it passes
watch out
- A deterministic heuristic will over-group or split some errors; make manual inspection possible.
next phase
4
Alerts and retention
Alerts and retention for Sentry: Create one email alert outbox item for a new or reopened issue and throttle repeated occurrences.
1. Create one email alert outbox item for a new or reopened issue and throttle repeated occurrences.
  Files features/alerts_and_retention.pytemplates/alerts_and_retention.html
2. Add retention deletion for old events and keep explicit issue summaries; expose failed/unknown delivery for owner review.
  Files features/alerts_and_retention.py
3. Use Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. Check: A burst of 100 repeated occurrences produces one new-issue alert. Then check: Deleting expired events leaves current events queryable and updates counts consistently. 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_alerts_and_retention.py
  terminal
  python -m unittest discover -s test
done when · tick each as it passes
watch out
- SMTP acknowledgement is not proof of inbox delivery; do not promise exactly-once notifications.
next phase
5
Portable delivery and clean-start proof
Finish the Sentry replacement with a documented first-run path and a recoverable export.
1. Document prerequisites, every configuration variable, data locations and the three domain workflows: Bounded ingestion; Grouping and release views; Alerts and retention. 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. 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 sentry. Restore into a separate empty directory or isolated deployment, with all outbound actions and schedules disabled. Recreate this proof: Two exceptions with matching application frames, a distinct exception, a repeated event id and a secret in context. Compare ids/counts and open the result before recording the restore date. Never test a restore over the only live copy.
  Files OPERATIONS.mdscripts/backup.py
3. 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.mdverification.md
  terminal
  python -m pip install -r requirements.txt python -m unittest discover -s test
done when · tick each as it passes
watch out
- Export without an import or restore rehearsal is not verified portability.
6
Operate and share with access controlsproduct builder
Product-builder only: make a private error collector with deterministic grouping and one alert channel operable for its stated audience before allowing remote access.
1. 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.mdOPERATIONS.md
2. 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 CaddyfileOPERATIONS.md
  terminal
  waitress-serve --listen=127.0.0.1:5000 app:app
3. 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 sentry. 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.mdrelease-checklist.md
done when · tick each as it passes
watch out
- Product mode is additional engineering, not a switch that makes a local prototype production-ready.

what this build does not replace

This is a private error collector with deterministic grouping and one alert channel; full Sentry feature parity, vendor hosting and support are not included.
SDK ecosystem, grouping models, tracing, replay, global ingestion, and enterprise operations
global probe network
phone and SMS delivery
massive retention
advanced incident response and support

after v1, if you want it

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

Need the files? The project pack on the verdict page hands your agent the whole brief · more monitoring.