The pre-fix tests at tab-isolation.test.ts:43,57 encoded the broken
behavior as the contract — they specifically asserted "scoped agent
cannot write to unowned tab," which was the exact failure mode that
broke browser-skills. They passed because they tested the wrong
invariant.
This commit replaces those tests with explicit shared-vs-own-only
coverage that documents what each policy actually means:
- Shared scoped agents (skill spawns, default scoped clients) can
read AND write any tab — unowned, their own, or another agent's.
The capability is gated by scope checks + rate limits, not by tab
ownership.
- Own-only scoped agents (pair-agent over tunnel) cannot read OR
write any tab they don't own. Pre-fix this case was conflated with
shared writes; now it's explicit.
9 unit assertions on checkTabAccess, up from 6. Each test names
the policy axis it's covering so a future refactor can't quietly
flip the contract.
Adds source-shape regression test 10a in server-auth.test.ts:
"tab gate predicate is own-only-scoped, not write-scoped." The
gate's `if (...)` line MUST contain `tabPolicy === 'own-only'` and
MUST NOT contain `WRITE_COMMANDS.has(command) ||`. If a future
refactor re-introduces the write-scoped gate, this fails immediately
in free-tier `bun test`.
Updates the marker for the existing newtab-excluded test to match
the new comment block ("Tab ownership check (own-only tokens /
pair-agent isolation)").
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Garry Tan
6022db2c9a