Count the visits, and say whether anyone got anywhere

A hosted demo raises a question a local app never does: is anyone using it,
and do they reach the part that matters? `/analytics` answers it — visitors,
pages, referrers, countries, devices, which shared scenarios get played, turns
and demo-key spend, API and turn errors, and a funnel from visited to played a
turn to signed up.

Not a third-party script, for reasons specific to this one. The CSP allows
`script-src 'self'`, so a tracker means loosening it; adblockers eat the
popular ones, which silently biases exactly the technical audience this
project gets shown to; and none of them can see the measurement that actually
matters here, which is a turn, not a pageview.

**A visit is a write and never a read.** After the 189x egress fix it would be
perverse to add a feature that reads rows per request, so counts accumulate in
a process-local dict and flush every 60s as UPSERTs. Storage is a generic
`(day, metric, label) -> hits` counter, so measuring something new later costs
a constant rather than a migration, plus one row per visitor per day for the
funnel flags. Every dashboard query is a GROUP BY returning tens of rows
however much traffic sits behind it; a month reads back in a few kilobytes.
The buffer's cost is that a hard restart can lose up to a minute — the flusher
also runs on shutdown, and a tier that sleeps when idle sleeps on an empty
buffer anyway.

**The counters are anonymous; the access log beside them is not, on purpose.**
A visitor is `HMAC(secret, "visitor:<user id>")` truncated to 32 chars —
one-way, so `analytics_daily` and `analytics_visitor_days` cannot be joined
back to `users`, and keyed, so no client can compute one. Story content never
reaches that module, and the only content it ever names is a seeded public
scenario's title; a player's own titles are theirs. `accesslog.py` is the
identifying half and is a separate module writing a separate table so that
separation is a property of the code rather than a convention: `access_events`
records sessions, sign-ins, registrations and failed attempts with address,
email and device, read on a second tab of the same page behind the same gate.

Both halves are gated on `AIDND_ANALYTICS_EMAILS`, not `POWER_USERS`. An
unmetered tester is not automatically someone who should see the traffic. The
route 404s and the nav link is absent for everyone else, the same treatment
AI Chat gets; unset in a hosted deploy means nobody sees it, including me.

Three things came out of building it that a test would not have suggested.

**A failed turn is an HTTP 200 with a bad ending.** The status-code middleware
cannot see one, so a demo whose model had started refusing every request would
look perfectly healthy from outside. All five SSE error paths in
`_generate_turn` now go through a `turn_error()` helper that counts on the way
out. Error buckets elsewhere are labelled by the matched route template rather
than the requested path — one bucket per endpoint instead of one per adventure
id, and, the reason it isn't merely tidier, an unmatched path is entirely
attacker-chosen, so labelling by it would let anyone mint rows.

**The funnel counts people, not clicks.** A player who starts six adventures
is one person who started an adventure. That is the whole reason the
per-visitor-day table exists; its flags only ever turn on, and `is_new` is
settled by the first write of a visitor's first day.

**The tests run on SQLite and production is Neon.** A flush that raises is
caught and logged, so a dialect mistake in the UPSERTs would have stayed
invisible until the dashboard quietly never filled.
`test_the_upserts_compile_for_postgres` compiles both statements against the
Postgres dialect without connecting to one.

Two things this leans on elsewhere. `limits._client_ip` is now public
`client_ip`: the access log needs the same answer, and two functions both
deciding which hop is the caller's is how one of them ends up trusting a
header it shouldn't. And the cleanup sweeper now starts if *either* job has
work — a deployment can keep every guest forever and still want its
visitor-day rows aged out.

No migration. Both tables are new and `bootstrap()` calls `create_all` on
existing databases too, the route `branches` took in Phase 14, so
`LATEST_VERSION` is still 64.

497 tests green, frontend lint and build clean, driven by hand against a
synthetic 90-day fixture at 1568px. The narrow-screen layout follows the
existing 720px block but is unverified: `resize_window` is ignored on a
maximized Chrome and `frame-ancestors 'none'` rules out checking it in a sized
iframe. Also repaired here: a rename in test_ratelimit_hardening.py had run
through the test names themselves, leaving `testclient_ip_*` — still collected
by pytest, which is why it passed unnoticed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DfMCsN1KBLsTqMkj5hSgrY

backend/app/routers/auth.py

@@ -3,7 +3,7 @@ import re
 from fastapi import APIRouter, Depends, HTTPException, Request, Response
 from sqlalchemy.orm import Session
 
-from .. import auth, cleanup, limits, models, schemas, security
+from .. import accesslog, analytics, auth, cleanup, limits, models, schemas, security
 from ..database import get_db
 from .settings import get_settings
 
@@ -34,6 +34,8 @@ def me_payload(user: models.User, db: Session) -> dict:
         "is_guest": user.is_guest,
         # Trusted testers: unmetered demo turns, plus the AI Chat scratchpad.
         "power_user": auth.is_power_user(user),
+        # Separate allowlist: shows the visit-analytics page and its nav link.
+        "analytics": auth.is_owner(user),
         # How long an idle guest is kept before cleanup deletes it (None when
         # the policy is off). Served rather than hardcoded in the UI so the
         # number a guest is shown is the number actually enforced.
@@ -65,6 +67,9 @@ def me(request: Request, response: Response, db: Session = Depends(get_db)):
             db.add(user)
             db.commit()
             _set_session_cookie(response, user.id)
+    # This endpoint is the SPA's bootstrap call, so it is where a session first
+    # shows itself; accesslog thins the rows down to one per day per address.
+    accesslog.note_session(db, user, request)
     return me_payload(user, db)
 
 
@@ -93,6 +98,8 @@ def register(
     user.password_hash = security.hash_password(payload.password)
     user.is_guest = False
     db.commit()
+    analytics.record_event(analytics.EV_SIGNUP, user)
+    accesslog.record(db, accesslog.REGISTER, request, user=user)
     return me_payload(user, db)
 
 
@@ -119,9 +126,15 @@ def login(
         or not security.verify_password(payload.password, user.password_hash)
     ):
         limits.note_login_failure(email)
+        # Logged with the address that was tried, not the account that owns it:
+        # a guessing run against an address that has no account is exactly the
+        # thing worth being able to see.
+        accesslog.record(db, accesslog.LOGIN_FAILED, request, who=email)
         raise HTTPException(401, "Incorrect email or password.")
     limits.note_login_success(email)
     _set_session_cookie(response, user.id)
+    analytics.record_event(analytics.EV_LOGIN, user)
+    accesslog.record(db, accesslog.LOGIN, request, user=user)
     return me_payload(user, db)