Returning to chat.hermes.bstein.dev after a Keycloak logout/login showed
"This session is unavailable to this account. Start a new chat." even
though the session was intact and owned by the same subject.
The banner comes from the continuity fallback the router injects into
every chat page. It polled `/api/sessions/<id>` and
`/api/sessions/<id>/messages` — routes that belong to the Hermes agent
dashboard (added by scripts/patch_web_session_activity.py, applied only
in agent-deployment.yaml). The router proxies browser traffic to the
tenant Hermes WebUI instead, whose only session read is
`GET /api/session?session_id=<id>`; the dashboard paths are unrouted
there, so server.py answered its generic 404 for every poll and the
fallback reported a false ownership failure.
The script runs only on a full document load of `/session/<id>`, which is
exactly what the OIDC round-trip produces when oauth2-proxy returns the
browser to `rd=/session/<id>` — hence the "only after relogin" symptom.
Poll the WebUI contract instead, and let its own answers decide what the
banner claims: 409 `session_profile_mismatch` is the single response that
means the session is outside this account's active scope, 404 now means
the conversation is no longer stored, and 401/403 still re-enter OIDC.
The steady-state poll drops to one request and backs off to 3s/15s now
that it reaches a real endpoint on the tenant Raspberry Pi.
`boundSessionSnapshot` follows the same move: it caps the WebUI envelope
`{"session": {..., "messages": [...]}}`, relaying every other session key
verbatim rather than re-serializing a fixed struct that would silently
drop metadata the banner depends on.
Isolation is unchanged and now covered: the router still resolves the
slot from the salted Keycloak subject, overwrites any client-supplied
X-Hermes-Tenant-Identity, and forwards only the two tenant cookies.
Tests: relogin keeps a stable slot and resolves the durable session; a
second subject replaying the owner's session id, WebUI cookie and a
forged tenant header gets 404 from its own backend and never reaches the
owner's; the legacy dashboard paths are pinned as permanent 404s against
a stub of the deployed WebUI dispatch.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
