test(hermes): wait for the hook installer instead of racing a 1 s deadline

[teamleaderleo]

Summary

tests/test_hermes_wrapper_hooks.py fails on main in shard 4's CLI no-socket lane with bare: unexpected installer calls: [] (main run 36326938624; #14958 run 36329092303, attempts 1 and 2). That blocks ci-status on unrelated PRs.

Neither the wrapper nor the test changed near the first failure; both were last touched on 2026-09-24. The first failing main run (23d22d78439) is the first one to include #14990, which runs that lane eight tests at a time. The last passing run (3761671f520) didn't include it.

The harness gave every launch a 1 s installer deadline (CMUX_HERMES_AGENT_HOOK_INSTALL_TIMEOUT_SECONDS=1). When the deadline passes, the wrapper kills the installer and launches Hermes anyway, which is the intended product behavior. On a busy runner, the first launch's cold start of perl and the bash installer can take over a second. The fake installer was killed before it recorded anything, so the check saw no call.

Now only the deadline tests set an installer deadline: stalled installer keeps 1 s and non-positive timeout keeps 0. Every other launch gets as long as the wrapper hang guard (5 s, unchanged). Those checks now wait for the installer to finish and the wrapper to exit instead of racing the installer's start. A real hang still fails, and the hang guard now reports it as wrapper execution deadline exceeded before the installer deadline can hide it. The wrapper itself is unchanged.

Testing

The installer checks are portable, so these ran on Linux. The TUI bridge checks fail on Linux on both main and this branch because the wrapper needs /usr/bin/plutil; they're unrelated to this change.

• Regression (f15cbd20b95): a new check delays the fake installer's start by 1.5 s. python3 tests/test_hermes_wrapper_hooks.py fails with the same messages as CI: slow installer start: unexpected installer calls: [] and installer lost surface/workspace attribution: {}.
• Fix (2e18ce8008d): the same command passes that check. The only remaining failures are the two Linux-only TUI bridge lines that main also shows.
• Under load: I ran the session-entrypoint, installer-failure and profile checks with 64 CPU spinners on 16 cores and the test at nice 12. On main, 2 of 2 iterations failed (installer lost surface attribution: {} and explicit-profile-long: installer targeted the wrong profile: {}, meaning the installer was killed mid-run). With the fix, 3 of 3 passed.
• python3 scripts/verify-local.py passed 12 of 13 selected checks. It doesn't cover native builds.

The macOS lane on this PR is the first run of the full file on a Mac with this change.

Changelog

none

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Summary by cubic

Fixes a flaky Hermes hooks test that failed on busy CI runners when the installer took over a second to start.

• The launch-path checks no longer impose the 1 s installer deadline; only deadline-focused tests set one.
• Added a check that a slow-starting installer's call is still observed.
• A real installer hang still fails, now reported as wrapper execution deadline exceeded.

^{Written for commit 2e18ce8. Summary will update on new commits.}

[github-actions]

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• tests/test_hermes_wrapper_hooks.py

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[teamleaderleo]

Toolbox g1 🔔 reviewed the Hermes test-only fix. It keeps the one-second timeout only for deadline tests, gives normal launch assertions the existing five-second hang guard, and adds a regression for slow installer startup. Required checks are green; landing it to unblock ci-status failures.

[github-actions]

Merge receipt for 2e18ce8008: every check was green at merge (10 verified; 11 skipped by policy). Full suite runs on main after merge.