The actual cause-fix for the staging-tabs E2E saga (#2073/#2074/#2075).
Old behaviour: ANY 401 from any fetch on a SaaS tenant subdomain
called redirectToLogin → window.location.href = AuthKit. This is
wrong. Plenty of 401s don't mean "session is dead":
- workspace-scoped endpoints (/workspaces/:id/peers, /plugins)
require a workspace-scoped token, not the tenant admin bearer
- resource-permission mismatches (user has tenant access but not
this specific workspace)
- misconfigured proxies returning 401 spuriously
A single transient one of those yanked authenticated users back to
AuthKit. Same bug yanked the staging-tabs E2E off the tenant origin
mid-test for 6+ hours tonight, leading to the cascade of test-side
mocks (#2073/#2074/#2075) that worked around the symptom without
fixing the cause.
This PR fixes it at the source. The new logic:
- 401 on /cp/auth/* path → that IS the canonical session-dead
signal → redirect (unchanged)
- 401 on any other path with slug present → probe /cp/auth/me:
probe 401 → session genuinely dead → redirect
probe 200 → session fine, endpoint refused this token →
throw a real Error, caller renders error state
probe network err → assume session-fine (conservative) →
throw real Error
- slug empty (localhost / LAN / reserved subdomain) → throw
without redirect (unchanged)
The probe adds one extra fetch on a 401, only when slug is set
and the path isn't already auth-scoped. That's rare and
worthwhile — a transient probe round-trip is cheap; an unwanted
auth redirect is a UX disaster.
Tests:
- api-401.test.ts rewritten with the full matrix:
* /cp/auth/me 401 → redirect (no probe, that IS the signal)
* non-auth 401 + probe 401 → redirect
* non-auth 401 + probe 200 → throw, no redirect ← the fix
* non-auth 401 + probe network err → throw, no redirect
* empty slug paths (localhost/LAN/reserved) → throw, no probe
- 43 tests in canvas/src/lib/__tests__/api*.test.ts all pass
- tsc clean
The staging-tabs E2E spec's universal-401 route handler stays as
defense-in-depth (silences resource-load console noise + guards
against panels without try/catch), but the comment now describes
its role honestly: api.ts is the primary fix, the route is the
safety net.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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