fix(web): send anonymous PostHog events as personless

[brendan-kellam]

Problem

In posthog.ts, unauthenticated server-side captures shipped with an empty distinctId. PostHog treated each such request as a new person, inflating person counts and billing.

Fix

tryGetPostHogDistinctId now resolves identity by mirroring the client's identified_only contract:

• Cookie present → use its distinct_id; identified iff $user_state === 'identified'.
• No cookie, authenticated → use the user id (identified).
• No cookie, unauthenticated → key the event to the install id.

Non-identified events are sent personless ($process_person_profile: false), so logged-out visitors and anonymous API calls no longer create a person profile per request. Identified users are unchanged.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Anonymous user events are now processed as personless, preventing unauthenticated requests from inflating analytics person counts and ensuring more accurate user metrics.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e19992f1-6351-4a53-b9c5-6adae7e017f7

📥 Commits

Reviewing files that changed from the base of the PR and between 889e2b1 and 7ed0a41.

📒 Files selected for processing (3)

• CHANGELOG.md
• packages/web/src/features/chat/llm.server.ts
• packages/web/src/lib/posthog.ts

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Walkthrough

PostHogCookie gains an optional $user_state field. tryGetPostHogDistinctId is refactored to return { distinctId, isIdentified } instead of a bare string. captureEvent uses isIdentified to inject $process_person_profile: false for anonymous events and falls back distinctId to SOURCEBOT_INSTALL_ID. llm.server.ts adopts the same destructuring and fallback.

Changes

PostHog Personless Event Handling

Layer / File(s)	Summary
PostHogCookie type and tryGetPostHogDistinctId refactor packages/web/src/lib/posthog.ts	PostHogCookie adds optional $user_state?: 'anonymous' | 'identified'. tryGetPostHogDistinctId return type changes from string | undefined to Promise<{ distinctId: string | undefined; isIdentified: boolean }>, deriving isIdentified from the cookie's $user_state or from the presence of an authenticated user id.
captureEvent personless mode and llm.server.ts wiring packages/web/src/lib/posthog.ts, packages/web/src/features/chat/llm.server.ts, CHANGELOG.md	captureEvent destructures the new return shape, conditionally injects $process_person_profile: false when isIdentified is false, and falls back distinctId to env.SOURCEBOT_INSTALL_ID. llm.server.ts applies the same destructuring and fallback when supplying posthogDistinctId to withTracing.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• sourcebot-dev/sourcebot#882: Modifies packages/web/src/lib/posthog.ts by refactoring the PostHog distinct-id helper and how captureEvent derives distinctId, which is the same file and function this PR extends with the isIdentified / personless-mode logic.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(web): send anonymous PostHog events as personless' directly and specifically describes the main change—making anonymous PostHog events personless to prevent person count inflation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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• Create stacked PR
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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch brendan/posthog-anonymous-events

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