Vibecode PostHog

You are building a lean indie version of PostHog.

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 =====
# PostHog indie build

## Goal

Build the smallest trustworthy replacement for the core PostHog workflow for one developer or a tiny team.

## Scope

Collect first-party pageviews and custom events from your own sites, keep the raw rows yourself, and answer a handful of product questions from a local dashboard.

## Quick start

1. Install the documented dependencies.
2. Copy `.env.example` to `.env`.
3. Run the development command chosen during implementation.
4. Complete the acceptance checks in `BUILD_PLAN.md`.

## Honest limits

This build deliberately does not replace:
- session replay
- feature flags and experiments
- identity stitching across devices
- SQL over years of events
- ingestion that stays up without you watching it

If those capabilities are essential, use Umami instead of pretending the gap is solved.

===== AGENTS.md =====
# Agent instructions

- Optimize for a working, understandable weekend build.
- Prefer the fewest moving parts that satisfy the brief.
- Do not invent cryptography, security guarantees, APIs, or compliance claims.
- Keep secrets out of source control and logs.
- Add focused tests for destructive, security-sensitive, and data-loss paths.
- Run the project checks before declaring the build complete.
- Record any deliberate shortcut in the README under "Tradeoffs".

===== BUILD_PLAN.md =====
# Build plan

## Original build brief

Build me a self-hosted web analytics box to replace PostHog. Requirements:

- One Node 22 + Express process with better-sqlite3, serving the collector and the
  dashboard on port 8787. No frontend framework, no build step, no Docker.
- A tracker.js I paste on my sites: pageviews on load and history change, plus
  window.track('signup', { plan: 'pro' }), POSTed to /e on my own domain so
  collection stays first-party.
- One SQLite events table: site, event, path, referrer, UTM fields, country from the
  proxy header, device class, and a JSON properties blob.
- Count visitors by a daily-rotating salted hash of IP plus user agent, salt in .env.
  No cookie, never the raw IP. That is the whole privacy design, keep it.
- Dashboard at / with a date range picker: visitors and pageviews by day, top pages,
  referrers, countries, any event split by one property, and a three-step funnel.
- Nightly rollup into a daily-summary table, raw events pruned past the retention
  window in .env, /export.csv for the raw rows.
- Basic auth on the dashboard, collector open. No accounts, no telemetry, my box
  holds the only copy.
- Out of scope: session replay, feature flags, and stitching one person across
  devices. Do not build a plugin system or a warehouse connector.
- README: the snippet to paste, where the SQLite file lives, and how to back it up.

## Required capabilities

- Node 22
- a small always-on VPS
- a domain you control, for first-party collection

## Delivery order

1. Scaffold the smallest runnable application and document its commands.
2. Implement the primary data model and core workflow.
3. Add validation, safe failure states, and persistence.
4. Cover the critical path with automated tests.
5. Exercise a clean install from the README and fix every missing step.

## Done when

- A new user can go from clone to first successful workflow using only the README.
- The core workflow works without paid infrastructure unless the brief requires it.
- Tests cover the highest-risk behavior.
- Known limitations are explicit rather than hidden.

===== .env.example =====
# Copy to .env and document every variable when it is introduced.
# Never put real credentials in this file.

APP_ENV=development
# Add only values required by the selected implementation.

You are building a lean indie version of PostHog.

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 =====
# PostHog indie build

## Goal

Build the smallest trustworthy replacement for the core PostHog workflow for one developer or a tiny team.

## Scope

Collect first-party pageviews and custom events from your own sites, keep the raw rows yourself, and answer a handful of product questions from a local dashboard.

## Quick start

1. Install the documented dependencies.
2. Copy `.env.example` to `.env`.
3. Run the development command chosen during implementation.
4. Complete the acceptance checks in `BUILD_PLAN.md`.

## Honest limits

This build deliberately does not replace:
- session replay
- feature flags and experiments
- identity stitching across devices
- SQL over years of events
- ingestion that stays up without you watching it

If those capabilities are essential, use Umami instead of pretending the gap is solved.

===== AGENTS.md =====
# Agent instructions

- Optimize for a working, understandable weekend build.
- Prefer the fewest moving parts that satisfy the brief.
- Do not invent cryptography, security guarantees, APIs, or compliance claims.
- Keep secrets out of source control and logs.
- Add focused tests for destructive, security-sensitive, and data-loss paths.
- Run the project checks before declaring the build complete.
- Record any deliberate shortcut in the README under "Tradeoffs".

===== BUILD_PLAN.md =====
# Build plan

## Original build brief

Build me a self-hosted web analytics box to replace PostHog. Requirements:

- One Node 22 + Express process with better-sqlite3, serving the collector and the
  dashboard on port 8787. No frontend framework, no build step, no Docker.
- A tracker.js I paste on my sites: pageviews on load and history change, plus
  window.track('signup', { plan: 'pro' }), POSTed to /e on my own domain so
  collection stays first-party.
- One SQLite events table: site, event, path, referrer, UTM fields, country from the
  proxy header, device class, and a JSON properties blob.
- Count visitors by a daily-rotating salted hash of IP plus user agent, salt in .env.
  No cookie, never the raw IP. That is the whole privacy design, keep it.
- Dashboard at / with a date range picker: visitors and pageviews by day, top pages,
  referrers, countries, any event split by one property, and a three-step funnel.
- Nightly rollup into a daily-summary table, raw events pruned past the retention
  window in .env, /export.csv for the raw rows.
- Basic auth on the dashboard, collector open. No accounts, no telemetry, my box
  holds the only copy.
- Out of scope: session replay, feature flags, and stitching one person across
  devices. Do not build a plugin system or a warehouse connector.
- README: the snippet to paste, where the SQLite file lives, and how to back it up.

## Required capabilities

- Node 22
- a small always-on VPS
- a domain you control, for first-party collection

## Delivery order

1. Scaffold the smallest runnable application and document its commands.
2. Implement the primary data model and core workflow.
3. Add validation, safe failure states, and persistence.
4. Cover the critical path with automated tests.
5. Exercise a clean install from the README and fix every missing step.

## Done when

- A new user can go from clone to first successful workflow using only the README.
- The core workflow works without paid infrastructure unless the brief requires it.
- Tests cover the highest-risk behavior.
- Known limitations are explicit rather than hidden.

===== .env.example =====
# Copy to .env and document every variable when it is introduced.
# Never put real credentials in this file.

APP_ENV=development
# Add only values required by the selected implementation.

You are building a production product version of PostHog.

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 =====
# PostHog product brief

## Problem

First-party collection and a dashboard that answers your top five questions is one sitting of work, and PostHog's free tier covers a million events a month before you pay anything. What the bill buys past that is the rest of the platform: session replay, feature flags, SQL over years of events, and ingestion that stays correct while your event schema drifts underneath it.

## Product outcome

Collect first-party pageviews and custom events from your own sites, keep the raw rows yourself, and answer a handful of product questions from a local dashboard.

## Target user

A serious builder who needs a maintainable product foundation rather than a one-off demo.

## Required capabilities

- Node 22
- a small always-on VPS
- a domain you control, for first-party collection

## Explicit non-goals for v1

- session replay
- feature flags and experiments
- identity stitching across devices
- SQL over years of events
- ingestion that stays up without you watching it

## Success criteria

- The primary workflow is measurable end to end.
- Setup is reproducible in a clean environment.
- Failure, recovery, and support paths are documented.
- Product claims match what the implementation actually guarantees.

===== ARCHITECTURE.md =====
# Architecture

## Starting brief

Build me a self-hosted web analytics box to replace PostHog. Requirements:

- One Node 22 + Express process with better-sqlite3, serving the collector and the
  dashboard on port 8787. No frontend framework, no build step, no Docker.
- A tracker.js I paste on my sites: pageviews on load and history change, plus
  window.track('signup', { plan: 'pro' }), POSTed to /e on my own domain so
  collection stays first-party.
- One SQLite events table: site, event, path, referrer, UTM fields, country from the
  proxy header, device class, and a JSON properties blob.
- Count visitors by a daily-rotating salted hash of IP plus user agent, salt in .env.
  No cookie, never the raw IP. That is the whole privacy design, keep it.
- Dashboard at / with a date range picker: visitors and pageviews by day, top pages,
  referrers, countries, any event split by one property, and a three-step funnel.
- Nightly rollup into a daily-summary table, raw events pruned past the retention
  window in .env, /export.csv for the raw rows.
- Basic auth on the dashboard, collector open. No accounts, no telemetry, my box
  holds the only copy.
- Out of scope: session replay, feature flags, and stitching one person across
  devices. Do not build a plugin system or a warehouse connector.
- README: the snippet to paste, where the SQLite file lives, and how to back it up.

## Boundaries

Separate the product into replaceable modules for interface, application logic, persistence, external integrations, and operational concerns. Keep domain logic independent from delivery frameworks and vendors.

## Production baseline

- Configuration: validated at startup with safe local defaults where possible.
- Security: least privilege, input validation, secret redaction, rate limits on abuse-prone paths, and no invented security primitives.
- Data: explicit schema and migrations, transactional writes where integrity matters, backup and restore instructions.
- Integrations: adapters around third-party providers, idempotent webhook or job processing, bounded retries, and timeouts.
- Observability: structured logs with request or operation IDs, an error-tracking hook, and health/readiness checks where a server exists.
- Quality: unit tests for domain rules, integration tests at module boundaries, and one end-to-end critical-path test.

## Decision records

For each major dependency, document why it was chosen, its failure mode, and how it can be replaced. Do not introduce infrastructure until a requirement justifies it.

===== AGENTS.md =====
# Agent instructions

- Read `PRODUCT.md` and `ARCHITECTURE.md` before changing code.
- Implement milestone by milestone; keep each change reviewable and leave the application runnable.
- 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 test pass.
- Use provider interfaces for external services and deterministic fakes in tests.
- Add migrations and rollback or recovery notes for persistent data changes.
- Log useful operational context without credentials, tokens, passwords, or personal data.
- Update documentation and run all checks before completing a milestone.

===== MILESTONES.md =====
# Delivery milestones

## M0 — Decisions and scaffold

- Confirm the runtime, persistence model, threat boundaries, and deployment target.
- Create a reproducible local environment and continuous checks.

## M1 — Core workflow

- Implement the smallest end-to-end product path with validation and tests.
- Keep integrations behind interfaces.

## M2 — Trust layer

- Add secure failure behavior, recovery paths, audit-relevant events, and data safeguards.
- Test abuse cases and destructive operations.

## M3 — Operability

- Add structured logs, error reporting hooks, health signals, backup/restore documentation, and deployment configuration.

## M4 — Release gate

- Run a clean-install test, critical-path end-to-end test, dependency review, and documented rollback exercise.
- Compare the shipped behavior with `PRODUCT.md` and publish remaining limitations.

===== OPERATIONS.md =====
# Operations

## Before release

- Validate configuration and secrets at startup.
- Define backup, restore, and rollback procedures and test them.
- Document logs, error tracking, health signals, and alert ownership.
- Set dependency update and vulnerability review expectations.

## Incident checklist

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 source when needed.
5. Document the root cause, remediation, and regression test.

## Launch constraint

Do not market omitted PostHog capabilities as implemented. The v1 non-goals in `PRODUCT.md` remain user-visible limitations until they are deliberately delivered.

# PostHog indie build

## Goal

Build the smallest trustworthy replacement for the core PostHog workflow for one developer or a tiny team.

## Scope

Collect first-party pageviews and custom events from your own sites, keep the raw rows yourself, and answer a handful of product questions from a local dashboard.

## Quick start

1. Install the documented dependencies.
2. Copy `.env.example` to `.env`.
3. Run the development command chosen during implementation.
4. Complete the acceptance checks in `BUILD_PLAN.md`.

## Honest limits

This build deliberately does not replace:
- session replay
- feature flags and experiments
- identity stitching across devices
- SQL over years of events
- ingestion that stays up without you watching it

If those capabilities are essential, use Umami instead of pretending the gap is solved.

# Agent instructions

- Optimize for a working, understandable weekend build.
- Prefer the fewest moving parts that satisfy the brief.
- Do not invent cryptography, security guarantees, APIs, or compliance claims.
- Keep secrets out of source control and logs.
- Add focused tests for destructive, security-sensitive, and data-loss paths.
- Run the project checks before declaring the build complete.
- Record any deliberate shortcut in the README under "Tradeoffs".

# Build plan

## Original build brief

Build me a self-hosted web analytics box to replace PostHog. Requirements:

- One Node 22 + Express process with better-sqlite3, serving the collector and the
  dashboard on port 8787. No frontend framework, no build step, no Docker.
- A tracker.js I paste on my sites: pageviews on load and history change, plus
  window.track('signup', { plan: 'pro' }), POSTed to /e on my own domain so
  collection stays first-party.
- One SQLite events table: site, event, path, referrer, UTM fields, country from the
  proxy header, device class, and a JSON properties blob.
- Count visitors by a daily-rotating salted hash of IP plus user agent, salt in .env.
  No cookie, never the raw IP. That is the whole privacy design, keep it.
- Dashboard at / with a date range picker: visitors and pageviews by day, top pages,
  referrers, countries, any event split by one property, and a three-step funnel.
- Nightly rollup into a daily-summary table, raw events pruned past the retention
  window in .env, /export.csv for the raw rows.
- Basic auth on the dashboard, collector open. No accounts, no telemetry, my box
  holds the only copy.
- Out of scope: session replay, feature flags, and stitching one person across
  devices. Do not build a plugin system or a warehouse connector.
- README: the snippet to paste, where the SQLite file lives, and how to back it up.

## Required capabilities

- Node 22
- a small always-on VPS
- a domain you control, for first-party collection

## Delivery order

1. Scaffold the smallest runnable application and document its commands.
2. Implement the primary data model and core workflow.
3. Add validation, safe failure states, and persistence.
4. Cover the critical path with automated tests.
5. Exercise a clean install from the README and fix every missing step.

## Done when

- A new user can go from clone to first successful workflow using only the README.
- The core workflow works without paid infrastructure unless the brief requires it.
- Tests cover the highest-risk behavior.
- Known limitations are explicit rather than hidden.

# Copy to .env and document every variable when it is introduced.
# Never put real credentials in this file.

APP_ENV=development
# Add only values required by the selected implementation.

# PostHog product brief

## Problem

First-party collection and a dashboard that answers your top five questions is one sitting of work, and PostHog's free tier covers a million events a month before you pay anything. What the bill buys past that is the rest of the platform: session replay, feature flags, SQL over years of events, and ingestion that stays correct while your event schema drifts underneath it.

## Product outcome

Collect first-party pageviews and custom events from your own sites, keep the raw rows yourself, and answer a handful of product questions from a local dashboard.

## Target user

A serious builder who needs a maintainable product foundation rather than a one-off demo.

## Required capabilities

- Node 22
- a small always-on VPS
- a domain you control, for first-party collection

## Explicit non-goals for v1

- session replay
- feature flags and experiments
- identity stitching across devices
- SQL over years of events
- ingestion that stays up without you watching it

## Success criteria

- The primary workflow is measurable end to end.
- Setup is reproducible in a clean environment.
- Failure, recovery, and support paths are documented.
- Product claims match what the implementation actually guarantees.

# Architecture

## Starting brief

Build me a self-hosted web analytics box to replace PostHog. Requirements:

- One Node 22 + Express process with better-sqlite3, serving the collector and the
  dashboard on port 8787. No frontend framework, no build step, no Docker.
- A tracker.js I paste on my sites: pageviews on load and history change, plus
  window.track('signup', { plan: 'pro' }), POSTed to /e on my own domain so
  collection stays first-party.
- One SQLite events table: site, event, path, referrer, UTM fields, country from the
  proxy header, device class, and a JSON properties blob.
- Count visitors by a daily-rotating salted hash of IP plus user agent, salt in .env.
  No cookie, never the raw IP. That is the whole privacy design, keep it.
- Dashboard at / with a date range picker: visitors and pageviews by day, top pages,
  referrers, countries, any event split by one property, and a three-step funnel.
- Nightly rollup into a daily-summary table, raw events pruned past the retention
  window in .env, /export.csv for the raw rows.
- Basic auth on the dashboard, collector open. No accounts, no telemetry, my box
  holds the only copy.
- Out of scope: session replay, feature flags, and stitching one person across
  devices. Do not build a plugin system or a warehouse connector.
- README: the snippet to paste, where the SQLite file lives, and how to back it up.

## Boundaries

Separate the product into replaceable modules for interface, application logic, persistence, external integrations, and operational concerns. Keep domain logic independent from delivery frameworks and vendors.

## Production baseline

- Configuration: validated at startup with safe local defaults where possible.
- Security: least privilege, input validation, secret redaction, rate limits on abuse-prone paths, and no invented security primitives.
- Data: explicit schema and migrations, transactional writes where integrity matters, backup and restore instructions.
- Integrations: adapters around third-party providers, idempotent webhook or job processing, bounded retries, and timeouts.
- Observability: structured logs with request or operation IDs, an error-tracking hook, and health/readiness checks where a server exists.
- Quality: unit tests for domain rules, integration tests at module boundaries, and one end-to-end critical-path test.

## Decision records

For each major dependency, document why it was chosen, its failure mode, and how it can be replaced. Do not introduce infrastructure until a requirement justifies it.

# Agent instructions

- Read `PRODUCT.md` and `ARCHITECTURE.md` before changing code.
- Implement milestone by milestone; keep each change reviewable and leave the application runnable.
- 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 test pass.
- Use provider interfaces for external services and deterministic fakes in tests.
- Add migrations and rollback or recovery notes for persistent data changes.
- Log useful operational context without credentials, tokens, passwords, or personal data.
- Update documentation and run all checks before completing a milestone.

# Delivery milestones

## M0 — Decisions and scaffold

- Confirm the runtime, persistence model, threat boundaries, and deployment target.
- Create a reproducible local environment and continuous checks.

## M1 — Core workflow

- Implement the smallest end-to-end product path with validation and tests.
- Keep integrations behind interfaces.

## M2 — Trust layer

- Add secure failure behavior, recovery paths, audit-relevant events, and data safeguards.
- Test abuse cases and destructive operations.

## M3 — Operability

- Add structured logs, error reporting hooks, health signals, backup/restore documentation, and deployment configuration.

## M4 — Release gate

- Run a clean-install test, critical-path end-to-end test, dependency review, and documented rollback exercise.
- Compare the shipped behavior with `PRODUCT.md` and publish remaining limitations.

# Operations

## Before release

- Validate configuration and secrets at startup.
- Define backup, restore, and rollback procedures and test them.
- Document logs, error tracking, health signals, and alert ownership.
- Set dependency update and vulnerability review expectations.

## Incident checklist

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 source when needed.
5. Document the root cause, remediation, and regression test.

## Launch constraint

Do not market omitted PostHog capabilities as implemented. The v1 non-goals in `PRODUCT.md` remain user-visible limitations until they are deliberately delivered.

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