Adds an optional roster.json (set of allowed student IDs) loaded at
startup. add_participant() raises StudentIdNotInRoster when the gate is
on and the supplied id is not present; route returns 403 with a clear
message and logs a roster_reject audit event. Names are NOT checked
against the roster: the join form asks for a current name as a soft
deterrent, but the only hard check is the id.
Includes a deploy/build_roster.py helper that turns class_register
attendance.xlsx into roster.json. Bootstrap env file now exports
QUIZ_ROSTER_PATH; missing file disables the gate (legacy behaviour).
Also drops the user-facing "The cookie is per-device." line from the
join card — students don't need to know the implementation; replaced
with "Enter your registered student ID and your current full name."
Three small UX/fairness tweaks from manual live testing:
1. Post-submit "wait for reveal" screen: show only the response time, no
score. The +score reveal leaked correctness — any positive number =
correct, zero = wrong — short-circuiting the "stop and think" beat
the reveal pause was supposed to enforce. Time stays as the
engagement signal; score now waits for the instructor reveal.
2. Final-screen "Correct X / Y" denominator is now total_questions
instead of questions_answered. Missed questions are scored zero, so
they belong in the denominator visibly. Server adds total_questions
to the session_ended payload.
3. Projector score-distribution: drop the in-chart count labels (they
collided with each other and with the median tag at small N), restore
the previously-computed-but-not-rendered x-axis tick labels at the
bottom. Stats line at the foot keeps n / mean / max.
Also: short-circuit the per-submit instructor + presence broadcasts
when no instructor / projector is connected (no listener, no DB work).
The 50-student load test was tight on margin against its 2 s
time_limit; with the new presence_message / live_histogram_message DB
queries firing on every submit, the margin disappeared on busy boxes.
Conftest fixture also bumped to 8 s per question for the same reason —
gives breathing room for sequential WS submits in the load test.
71/71 pytest green.
Both student-facing surfaces (the per-device join page and the
front-of-room projector) now render options as text only, no A/B/C/D
chips, no numeric prefixes. The letter-namespace remains internal:
canonical A..D in pool.json + submissions storage; canonical position
1..4 in the CSV export. Admin dashboard keeps letters because it is the
instructor's private console.
Why this lands now: the discussion of per-student option shuffling
flagged that A/B/C/D as discussion handles ("the answer is B") is itself
a leaky channel. Removing the labels closes that channel for the
non-shuffled case and keeps it closed if shuffling is added later.
Wire protocol: the submit message carries the option's full text
("answer": "Pipelining"). Server's submit_answer resolves text -> letter
via app.pool.resolve_option_key, which also accepts a canonical letter
so internal callers and tests stay readable. A non-matching string is
recorded as a zero-score submission with answer=NULL, locked in via the
PK + existing_submit_ack short-circuit. So an attempted UI bypass that
posts a fabricated string just produces a wrong answer; no retry.
CSV: A=1 .. D=2 .. C=3 .. D=4 in the answer column. Empty when no option
matched. Header unchanged so downstream pandas readers don't break, but
the value type is int instead of letter.
Histogram: the failsafe "submitted-but-no-match" row buckets into
"missed" alongside genuine misses — both yield zero credit and the
instructor cares about the same thing.
Tests:
- test_submit_accepts_option_text_resolves_to_canonical: production
wire format produces correct grading + canonical-letter storage.
- test_submit_failsafe_locks_in_zero_score_on_garbage_text: a non-
matching string is recorded at score=0 and a follow-up correct
submission cannot overwrite it.
71/71 green.
Closes the post-recovery re-attack window. Previously cookies were
authenticated purely cryptographically — once a hijacker received a
signed cookie for student_id=X, that cookie remained valid forever
(until QUIZ_SECRET_KEY rotated), even after admin clear-student + legit
re-claim issued a fresh cookie_id for X.
Now /me, /event, and /ws/student all check that the cookie's cookie_id
matches participants.cookie_id for the (sid, student_id). Mismatch ->
401 + Set-Cookie clearing for HTTP, ws.close(4001) for WS. The legit
re-claim wins because admin clear_student deletes the row and the next
join inserts the new student's cookie_id; the hijacker's cookie now
fails the DB check on every subsequent request.
Test: tests/test_anti_cheat.py::test_post_recovery_old_cookie_is_dead
covers the full hijack -> clear -> re-claim -> hijacker-locked-out
sequence end to end.
Refinement pass on top of the validated v1.2 base.
Hardening / quick fixes
- Caddyfile.tpl: CSP / HSTS / X-Frame / Referrer-Policy / Permissions-Policy,
1 MiB request body cap, X-Forwarded-For pass-through; stock-Caddy compatible.
- auth.py: STUDENT_MAX_AGE 1y -> 30d.
- bootstrap.sh: stage 5 prepends `git config --add safe.directory` so the
re-bootstrap path no longer 'detected dubious ownership' faults.
- admin.js: drop the misleading `closedPayload?.state || session.state`
shim; state derives from session only.
Anti-cheat
- New `student_events` audit table; new POST /api/session/{sid}/event for
blur / visibility_hidden / focus / visibility_visible. quiz.js debounces
events at 1.5s and uses sendBeacon for visibility_hidden so the event
survives a navigation. Counts surface in admin presence + CSV export.
- First-claim-wins on join: add_participant raises DuplicateStudentId on
PK violation; route returns 409 + records a duplicate_join audit event
with attempted name + IP + UA. Admin dashboard surfaces a per-row red
badge for hits on real participants and a top-of-page alert for orphan
attempts.
- DELETE /admin/api/students/{id} as the recovery hatch: clears the
participant + submissions, kicks active WS sockets so a stale cookie
cannot continue submitting. quiz.js surfaces the FastAPI detail message
in the join form so users see the 'already in use' guidance.
Presence panel
- New presence_update WS message; in-process presence map keyed on
student_id tracks ws_count + last_seen_ms. Admin dashboard renders
per-student rows: connected/idle/dropped dot, blur+hidden+duplicate
badges, 'answered current Q' tick, and a clear-student button.
Projector view (public, read-only)
- /projector/?sid=..., GET /api/session/{sid}/projector, WS
/ws/projector/{sid}. Single self-contained projector_state snapshot
pushed on every state change. Public leaderboard strips student_id;
QR rendered server-side as data: URL (CSP-compliant).
- Includes per-Q answer histogram, 8-bucket response-time distribution,
10-bucket score distribution.
- static/projector.{html,css,js}: editorial-broadside design — masthead,
registration crosses, conic-gradient countdown ring, SVG stepped-area
score distribution with median tick, leaderboard row-stagger. Inherits
light/dark tokens from style.css; honours prefers-reduced-motion. No
scroll at 1366x768 / 1920x1080 / 3440x1440.
Tests
- tests/test_anti_cheat.py: blur logging + CSV count, unknown-kind 422,
unauthenticated event 401, duplicate-join 409 + audit, admin
clear-student happy + 404, server-side submit lockout regression.
- tests/test_projector.py: snapshot shape, leaderboard student_id
redaction, WS push on state change, 404 for unknown sid, page redirect
when no sid.
- Existing tests updated for the new presence_update snapshot frame +
CSV header columns + first-claim-wins refusal of re-key.
57/57 pytest green; smoke-tested locally end-to-end.
Per-question score is now a float in [0.0, 1.0] snapped to a 21-level
0.05 grid, replacing the previous 0-1000 integer scale. Easier to read
on a leaderboard, ties become acceptable rather than vanishingly rare,
and small clock-skew differences no longer split rankings.
DB schema: score is REAL now (SQLite type affinity is loose enough that
existing rows still read fine, but new inserts go in as floats).
Frontend: added fmtScore() helpers in admin.js and quiz.js to render
two decimal places consistently (0.85, 1.20, 5.00) so float-arithmetic
sums never display as 0.8500000000000001.
Tests: linear_decay/flat/exponential_decay assertions updated; added
a snap-to-grid invariant test.
Students joining or reconnecting while the session is in question_closed
or finished previously got only a 'state' broadcast and nothing else,
leaving the SPA stuck on whatever was rendered before (typically the
join form's disabled state). Now send_student_snapshot replays the
question_closed message (and on finished, the session_ended payload)
so the SPA can render the reveal or final card immediately.
Mirrors the instructor-side reconnect fix in 22d1096.
Two issues from the first user test pass:
1. POST /admin/login was 500'ing on any password attempt that contained
non-ASCII characters (e.g. a smart-quote autofill from the browser
password manager). secrets.compare_digest(str, str) requires both
sides to be bytes or ASCII-only str; otherwise it raises TypeError.
Encoding both sides to UTF-8 bytes before the constant-time compare
makes the route degrade cleanly to 401 instead of 500.
2. Reconnecting an instructor while the session is in question_closed
left the dashboard stuck on "Reveal pending..." because
send_instructor_snapshot only replayed state + lobby_update +
full_leaderboard for closed sessions, not the question_open and
question_closed payloads needed to render the reveal card.
Now we replay question_open + question_closed + full_leaderboard
for the question_closed branch, so the SPA renders the full reveal
immediately on reconnect without waiting for the next event.
Three coupled fixes from the first manual test pass:
1. Stale signed cookie no longer 500s. `rooms.me()` now raises KeyError
when the participant row is gone (the previous code deref'd None and
threw TypeError, caught by quiz.js's catch-all as 'link expired').
`/api/session/{sid}/me` translates KeyError into 401 + delete_cookie,
so the client falls back to the join form cleanly.
Returning a JSONResponse directly because `raise HTTPException`
discards Response.delete_cookie mutations (FastAPI middleware
composes a fresh response on exception).
2. Reset is now a soft restart from the student's perspective. Before
closing each student WS in `RoomManager.reset`, the server now sends
a `{"type": "session_reset"}` message. The student SPA tears down
local state and re-runs boot(); /me returns 401 (now that the
participant is gone) and the join form renders without the user
having to manually reload. The WS close handler suppresses its
"Disconnected" screen during a reset to avoid a flash.
3. "You" highlight on the student leaderboard is now matched by id, not
by name. `RoomManager.leaderboard()` accepts an optional
`you_student_id` and stamps `is_you: true` on the matching entry only.
No other students' ids leak over the wire (we still don't include
`student_id` in the public top5 payload). quiz.js's renderBoard
prefers `r.is_you` when any row is marked, falling back to name match
for backward compatibility.
41/41 tests pass. Two new tests cover (a) the 401 + cookie-clear path
after reset and (b) `is_you` marking only the requesting student.
Backend simplification:
- The server now loads ONE pool JSON from $QUIZ_POOL_PATH at startup and
upserts a single canonical session. The session id comes from the pool
JSON's optional "session_id" field, falling back to $QUIZ_SESSION_ID.
- The multi-quiz / multi-session CRUD API is gone:
DELETED GET/POST /admin/api/quizzes
DELETED POST /admin/api/quizzes/upload
DELETED GET/POST /admin/api/sessions
DELETED GET /admin/login (HTML stub)
DELETED GET /admin/api/sessions/{sid}/csv (replaced by /admin/api/csv)
Replaced with a single-session control surface:
GET /admin/ — serves admin.html unconditionally
GET /admin/api/state — admin-gated; pool meta + state + QR + join URL
POST /admin/api/reset — admin-gated; wipe submissions + back to lobby
POST /admin/logout — clear admin cookie
GET /admin/api/csv — single-session results
WS /ws/instructor/{sid} — kept; new commands "next" + "reset"
- Instructor "Next" button is now a single state-driving command
(RoomManager.advance_to_next): from lobby it opens Q0; from question_open
it closes the current Q and opens the next; from question_closed it
opens the next; if past the last question it ends the session.
- New RoomManager.reset wipes submissions, participants, and per-question
state, then broadcasts a clean lobby.
- Student GET / now redirects to /?sid=<canonical> when no sid is given,
so the QR / share URL is fully deterministic.
Frontend rewrite (functional baseline; visual polish to follow):
- /admin/ is now a single SPA: GET /admin/api/state decides login form
vs dashboard. No separate /admin/login URL bar.
- Admin dashboard is state-driven with one primary action per state.
QR code, join URL, and live participant list are always visible on the
left so the operator can leave the page on a projector.
- Student answer buttons are big and tappable; reveal screen highlights
correct/wrong choice + shows score, total, and rank.
- Static admin/student SPAs share a CSS palette with light/dark support.
Tests rewritten around the single canonical session id.
The auto-bootstrapped session lets each test fixture skip the old
quiz/session creation dance. 39/39 tests pass.
Cleanup:
- Deleted CODEX_PROMPT.md, IMPLEMENTATION_REPORT.md, NOTES.md, SPEC.md,
static/observer.html (obsolete codex-build artifacts and the unused
observer view).
- .gitignore now blocks /pool.json (the runtime file the operator drops
on the server) and the leftover .codex_done / codex_run.log / etc.
- bootstrap.sh seeds /opt/quiz/pool.json from examples/pool_example.json
on first deploy so a fresh box reaches a usable state without manual
intervention; .env now includes QUIZ_POOL_PATH.
The first-pass JSON-decode hardening exposed two latent bugs that the
fuzz scenario hits as soon as the WS handler stays alive past a bad
message:
1) `data.get("type")` is called on whatever `receive_json()` decodes,
but valid JSON can be a list/string/number, not just a dict. Reject
non-object payloads with a structured bad_message error before
dispatch.
2) `submit_answer` did `if answer not in {"A","B","C","D"}` which
raises TypeError when the client sends an unhashable answer
(e.g. a dict). Add an isinstance(str) guard so any non-string
answer falls into the bad_answer branch instead of crashing the
handler.
31/31 pytest still passes. Together with the prior commit, the WS
handlers now survive the full set of fuzz payloads without dropping
the connection.
A single malformed JSON message (or a "WebSocket is not connected" race
on disconnect) was killing the per-client handler with an uncaught
exception in the ASGI app. The surrounding try/except only caught
WebSocketDisconnect, so the server would log a stack trace and the
client would silently drop.
Wrap receive_json() to catch JSONDecodeError, send a structured
{"type":"error","code":"bad_message"} ack, and continue. Widen the
outer except to (WebSocketDisconnect, RuntimeError) so disconnect
races on send/receive after close exit the handler cleanly instead
of bubbling up the ASGI stack.
Both student_ws and instructor_ws hardened in parallel. 31/31 pytest
suite still passes; this fixes the recurring fuzz-scenario warn and
the cycle-187-style cascade observed in the stress loop.
