OK! Now let's plan the next few activities. Tomorrow and next Thursday we hav...

In CBTF, students go through the quiz-api subdomain: quiz-api.usingandunderstanding.ai → api-service:3001. The quizzes.usingandunderstanding.ai web subdomain pairs with it.

The split exists because the edge nginx in front of those two hosts injects x-cbtf: true on inbound requests, which our cbtfDetection middleware (apps/api/src/middleware/cbtf.ts) uses to flip isCbtf=true and then enforce the route whitelist via cbtfRestriction. api.usingandunderstanding.ai doesn't get the header, so requests through it aren't treated as CBTF.

That's also why the cbtf e2e tests distinguish API_URL (regular) from QUIZ_API_URL (CBTF-flagged) — the latter exercises the restriction path.

Two places to track this: an inline TODO next to getPresentStudentCount (matches the pattern from recent commits) and a backlog memory entry.

Logged:

• Inline TODO at apps/api/src/socket.ts above getPresentStudentCount
• Backlog memory project_presence_hysteresis.md, indexed in MEMORY.md

Ready to commit alongside whatever else is pending, or separately.

Implementing hysteresis. Need an override mechanism so the existing presence.spec.ts doesn't have to wait 30s, so I'll add an e2e endpoint to tune the window.

Now the e2e endpoint for tuning the window, and update the presence test.

Let me also add a dedicated hysteresis-behavior test before running everything.

Those TS errors are in unrelated spec files. Let me confirm my changes didn't add any, then run the presence tests.

Both tests pass. Let me stop the dev server.

API type-check clean. Summary of the hysteresis implementation:

apps/api/src/socket.ts:

• Module-level HYSTERESIS_MS (default 30s, overridable via PRESENCE_HYSTERESIS_MS env var)
• Per-room Map<userId, lastSeenAt> tombstone store with markStudentRecentlyDisconnected / clearStudentRecentlyDisconnected helpers
• Added disconnecting handler (fires before socket.rooms is cleared, unlike disconnect) — records tombstones for every meeting room the socket was in
• room:join now clears the tombstone so returning students don't linger post-hysteresis
• room:leave also records a tombstone (explicit leave within hysteresis still holds)
• getPresentStudentCount unions live sockets with tombstones inside the window; prunes expired entries opportunistically
• Exported setPresenceHysteresisMs / getPresenceHysteresisMs for test overrides

apps/api/src/routes/e2e.ts:

• POST /api/e2e/presence/hysteresis { ms: 0..60000 } — tunes the window for e2e tests (dynamic import avoids pulling socket deps into every e2e route)

testing/e2e/tests/presence.spec.ts:

• Existing dedupe test now sets hysteresis to 500ms so tab-close drops reflect within one SWR poll cycle
• New hysteresis window holds the count steady through a brief disconnect test — 8s window, verifies the count holds at 1 during the window and drops to 0 after it elapses
• afterEach restores the 30s default so later tests aren't affected

Both presence tests pass (presence project: 7/7 green, 35.5s). Ready to commit.

Committed 33270c5 on presence_hysteresis. Working tree clean.