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/limits.py

@@ -32,6 +32,10 @@ RATE_LIMITS: dict[str, tuple[int, int]] = {
     "import": (30, 60),           # large writes
     "auth": (10, 300),            # register/login attempts, per IP
     "guest": (30, 300),           # new guest users, per IP (each is a DB row)
+    # Pageview beacons. Generous — a real reader clicking around a SPA fires a
+    # handful a minute — but low enough that nobody can inflate the traffic
+    # numbers faster than they could by actually reloading the page.
+    "analytics": (120, 60),
 }
 
 _windows: dict[tuple[str, str], deque] = defaultdict(deque)
@@ -49,11 +53,15 @@ _windows_guard = threading.Lock()
 TRUSTED_PROXY_HOPS = max(1, int(os.environ.get("AIDND_TRUSTED_PROXY_HOPS", "1") or 1))
 
 
-def _client_ip(request: Request) -> str:
-    """The real client IP for rate-limit keying, resistant to a spoofed
-    X-Forwarded-For. Takes the hop the trusted edge appended (rightmost minus
-    any extra trusted hops); falls back to the socket peer when no forwarded
-    header is present (local/dev, or a direct connection)."""
+def client_ip(request: Request) -> str:
+    """The real client IP, resistant to a spoofed X-Forwarded-For. Takes the
+    hop the trusted edge appended (rightmost minus any extra trusted hops);
+    falls back to the socket peer when no forwarded header is present
+    (local/dev, or a direct connection).
+
+    Public because the access log needs the same answer, and two functions that
+    both decide "which address is the caller's" is how one of them ends up
+    trusting a header it shouldn't."""
     forwarded = request.headers.get("x-forwarded-for")
     if forwarded:
         parts = [p.strip() for p in forwarded.split(",") if p.strip()]
@@ -68,7 +76,7 @@ def rate_limit(scope: str, request: Request, user: models.User | None = None) ->
     if not auth.MULTI_USER:
         return
     limit, window_seconds = RATE_LIMITS[scope]
-    key = (scope, f"u{user.id}" if user else f"ip{_client_ip(request)}")
+    key = (scope, f"u{user.id}" if user else f"ip{client_ip(request)}")
     now = time.time()
     with _windows_guard:
         window = _windows[key]