A valid session:// deep link to a session owned by a DIFFERENT Hermes
profile used to look identical to a deleted session (404 -> frontend
self-heals away). Now GET /api/session returns a structured 409
session_profile_mismatch envelope (error/code/session_id/profile ONLY,
no transcript) ONLY when the owning profile is KNOWN, and loadSession()
catches it, switches to the owning profile, and retries once. Truly
missing/deleted or legacy None-profile sessions keep the 404 self-heal.
Gate fixes applied (Codex + Fable):
- Codex CORE: added a post-await stale-load guard after
_switchProfileForSessionLoad so a navigation during the switch can't
hijack the UI back to the old session.
- Fable Finding 1: only emit 409 when _session_profile is truthy;
a None-profile (missing/legacy) session under a non-default active
profile now keeps 404 instead of a useless profile=null 409 (which
skipped self-heal + spun the SSE reconnect against a dead sid). Both
detail branches. + 2 regression tests.
- Fable Finding 2: _switchProfileForSessionLoad now clears the sidebar
skeleton + re-renders from cache on switch-POST failure (mirrors the
#4671 canonical-switch catch), then rethrows, so a failed switch can't
strand the sidebar on the skeleton.
Reconciled tests/test_issue1611_session_profile_filtering.py (4 tests) to
the 409 contract while preserving the no-leak boundary assertion.
Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>
