test(desktop): unmount every TerminalSubstrate tree before the window closes - #9440

Summary

desktop/src/features/terminal/TerminalSubstrate.test.mjs can pass every test and then run the Desktop JS job out of memory several minutes later. This moves the React Testing Library unmount from beforeEach to afterEach, so no tree is still mounted when the jsdom window closes. Only the test file changes (6 insertions, 2 deletions).

Commit (cherry-picked unchanged from a local flake-fix series):

• test(desktop): unmount every TerminalSubstrate tree before the window closes

CI sighting

One sighting was found in the CI runs from 7 to 12 November 2026 that were searched:

• 9 November 2026, "Desktop Domain / Desktop JS", run 42706004493 attempt 1 (on feat(workflow): add owner-only agent mentions for workflow messages #9227; the rerun passed):
  • https://github.com/block/buzz/actions/runs/42706004493/job/129463488242

In that job the suite reported 6,950 of 6,951 passing. The log shows An update to TerminalSubstrate inside a test was not wrapped in act(...) at 21:54:33Z, then FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory at 22:02:17Z, and the file is reported as failed at file level (test at src/features/terminal/TerminalSubstrate.test.mjs:1:1) after 504.6 s.

Root cause

The file called cleanup() only in beforeEach, so the last test's tree was still mounted when after(() => dom.window.close()) ran. If ThemeProvider's asynchronous palette update landed after that close, it re-rendered the substrate, the splash effect's palette guard passed, and requestAnimationFrame on the closed window started a fresh jsdom interval that nothing cleared. That 60 Hz loop repainted the banner into the test's recording getContext stub indefinitely, and paintLog grew until the heap limit. No individual test hangs, so a per-test timeout would not catch it.

Fix

afterEach(() => cleanup?.()) unmounts every tree, including the last, before after() closes the window. The beforeEach call became redundant and is removed. No assertions change, and no timeouts, retries or sleeps are added.

Related issue

N/A (flake fix). No existing issue or PR for this failure was found. Three open PRs touch the same test file (#5057, #5485, #7777); none of them changes where cleanup runs.

Testing

Human testing is still required. This PR does not carry buzz-review-completed; the author has not yet run this test themselves on this branch.

Verification of the fix (before this branch was split out)

• The test file, 5 consecutive runs: 25 of 25 tests passed each time in about 6.8 s, with no act warning.
• The CI out-of-memory failure was not reproduced with the real test file. Its mechanism was reproduced in a scratch harness with the same stubs: without cleanup before the window close, 3 of 3 runs left the palette unresolved at close, added 11,556 paintLog entries per 100 ms, kept one live timer, and never exited. With cleanup before the close, 3 of 3 runs added no entries, left no timers, and exited on their own.

Local checks on this branch

The push ran the repository's full pre-push hook set from a checkout of this branch's head (7f4117340), with no lanes excluded and without --no-verify. The branch is one commit behind main; that commit changes only mobile and docs files, none of them touched here.

Ran and passed:

• branch-skew, push-head-scope and file-size-check
• desktop-check (pnpm check)
• desktop-typecheck (pnpm typecheck)
• desktop-test (pnpm test, the full desktop unit suite, which includes TerminalSubstrate.test.mjs)

Did not run:

• rust-tests, desktop-tauri-checks and mobile-checks. The hook selects lanes by changed path, and this branch changes no Rust, Tauri or mobile file.
• Desktop builds and the Playwright E2E suites, which are CI-only.
• just ci.
• The 5-run repetition and the scratch harness above were not repeated on this branch.

A green run does not prove the flake is gone: the failure needs the palette update to land after the window closes.

🤖 Generated with Claude Code