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/cleanup.py

@@ -42,7 +42,7 @@ from sqlalchemy import delete, func
 from sqlalchemy.orm import Session
 from starlette.concurrency import run_in_threadpool
 
-from . import auth, models
+from . import analytics, auth, models
 from .database import SessionLocal
 
 logger = logging.getLogger(__name__)
@@ -72,6 +72,13 @@ def enabled() -> bool:
     return auth.MULTI_USER and RETENTION_DAYS > 0
 
 
+def anything_to_sweep() -> bool:
+    """Whether the periodic task is worth starting at all. The two jobs it runs
+    are independent: a deployment can keep every guest forever and still want
+    its analytics rows aged out, and vice versa."""
+    return enabled() or analytics.RETENTION_DAYS > 0
+
+
 def delete_stale_guests(db: Session, *, now: datetime | None = None) -> int:
     """Delete guests idle for RETENTION_DAYS or more. Returns the row count.
 
@@ -105,12 +112,19 @@ def delete_stale_guests(db: Session, *, now: datetime | None = None) -> int:
 
 def sweep() -> int:
     """One pass, with its own session. Never raises: a failed cleanup must not
-    be able to take the app down (same rule as seeding)."""
-    if not enabled():
+    be able to take the app down (same rule as seeding). Returns the guest
+    count, which is the number worth logging about."""
+    if not anything_to_sweep():
         return 0
     db = SessionLocal()
     try:
-        removed = delete_stale_guests(db)
+        # Ages out the per-visitor analytics rows, on its own terms: it is not
+        # about guests, and it must still happen on a deployment that has
+        # chosen to keep every account it ever minted.
+        aged = analytics.purge_old_visitor_days(db)
+        if aged:
+            logger.info("Aged out %d analytics visitor-day row(s).", aged)
+        removed = delete_stale_guests(db) if enabled() else 0
         if removed:
             logger.info(
                 "Cleaned up %d guest account(s) idle for %d+ days.",
@@ -135,16 +149,18 @@ async def _sweep_loop() -> None:
 
 
 def start_sweeper() -> asyncio.Task | None:
-    """Kick off the periodic sweep; None when the policy is off."""
+    """Kick off the periodic sweep; None when there is nothing to sweep."""
     if not enabled():
         logger.info("Guest cleanup disabled (multi_user=%s, retention_days=%d).",
                     auth.MULTI_USER, RETENTION_DAYS)
+    else:
+        logger.info(
+            "Guest cleanup on: deleting guests idle %d+ days, every %d hour(s).",
+            RETENTION_DAYS,
+            SWEEP_INTERVAL_SECONDS // 3600,
+        )
+    if not anything_to_sweep():
         return None
-    logger.info(
-        "Guest cleanup on: deleting guests idle %d+ days, every %d hour(s).",
-        RETENTION_DAYS,
-        SWEEP_INTERVAL_SECONDS // 3600,
-    )
     return asyncio.create_task(_sweep_loop())