fix(server): installed editors no longer vanish when discovery is slow

[bfowler]

What Changed

Editor discovery lists each PATH directory once per scan and only stats names that appear in the listing. Before, it stat-ed every PATH × PATHEXT candidate for every known editor.

• withPathDirectoryListings (packages/shared/src/shell.ts) provides a per-scan Cache of directory listings. resolveAvailableEditors wraps its scan in it. Single lookups outside a scan are unchanged.
• Each listing records the directory's mtime, read before the directory is listed. Before a lookup reuses a listing, it checks the mtime again and relists the directory if it changed. A command installed mid-scan is still found.
• A missing directory is treated as empty. A directory that can't be dated or listed (permissions, a busy share, or a PATH entry that isn't a directory) falls back to direct probes, as on main.
• The final stat still checks the exact spelling and rejects non-files, so case-sensitive directories behave as before.

Why

Fixes #4697. #4291 bounds discovery at 5 seconds and turns a timeout into [], so the Open menu shows "No installed editors found". On long Windows PATHs the scan routinely took longer than that. On the machine that produced this PR (73 PATH entries, 12 PATHEXT extensions), running both scans against the real filesystem:

	main	This PR
Time	6.2–11.1 s	245–266 ms
Filesystem calls	34,212 stats	1,567 stats (mostly directory mtime checks) + 88 listings
Found	cursor, vscode, zed, file-manager	same

The listing approach and its fallback come from #6124 / #11071. Earlier revisions of this PR also probed editors concurrently and kept partial or previous results when the 5-second bound hit. I dropped those to keep this PR focused. They only matter when a probe hangs outright (for example, an unreachable network share on PATH), which the speed-up doesn't change, and they can follow separately.

Validation

• packages/shared: vp test run src/shell.test.ts, 34 passed. The new test checks that PATH order is preserved, that only listed names are stat-ed, and that a directory changed mid-batch is relisted. It fails if either the listing filter or the mtime recheck is removed.
• apps/server: vp test run src/process/externalLauncher.test.ts, 15 passed / 22 skipped (POSIX-only tests skip on a Windows host). Existing tests pass unchanged.
• tsc --noEmit is clean for apps/server and packages/shared, and targeted lint and fmt are clean.
• Not verified in a packaged desktop build.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (no UI change; the Open menu now receives the correct list)
• I included a video for animation/interaction changes (n/a)

Model: Claude Opus 5.5 (1M context). Harness: Claude Code in T3 Code.

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Summary by CodeRabbit

• Bug Fixes
  • Editor discovery now continues without a local scan time limit, and incomplete or interrupted scans no longer replace previously cached results.
  • Command lookup now refreshes results when a PATH directory changes and checks candidates directly when a directory listing is unavailable or cannot be used. This helps command resolution reflect the current filesystem state.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This production fix substantially changes editor discovery through concurrency, timeout-based partial results, and shared PATH-listing caches across server and shared code. An unresolved Medium finding also flags that stale listings can hide newly installed commands, warranting human review.

Not approved because:

• 1 blocking correctness issue found at or above your repo's Minimum Blocking Severity

^{Adjust the Minimum Blocking Severity for this repo — including turning it Off — in Settings. You can add or adjust custom eligibility rules. Learn more.}

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📝 Walkthrough

Walkthrough

PATH directory listings now handle non-directory entries and refresh when directory modification times change. Editor discovery uses sequential probes, shares PATH listings during discovery, and updates its cache only after successful completion.

Changes

Windows editor discovery and PATH lookup

Layer / File(s)	Summary
Cache and refresh PATH listings packages/shared/src/shell.ts, packages/shared/src/shell.test.ts	PATH listing creation handles missing, non-directory, and unlistable paths. Command resolution reloads cached listings when a listed directory's modification time changes. The updated test checks PATH order, matching executable-name probes, and relisting after a directory changes.
Sequential editor discovery and cache updates apps/server/src/process/externalLauncher.ts	Editor discovery probes editors sequentially and shares PATH listings during discovery. The cache updates after successful discovery; failed or interrupted discovery does not update it.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge, utkarshusername

Merge Risk: 🔵 Low · up to 614f1

A newly installed command may be missed during a scan if its PATH directory reports the same modification time. This narrow issue remains open, but the claimed editor-scan regression is not introduced by this PR.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 614f1

A slow editor lookup can now cause the server to report no installed editors, even when other editors are available. The server still limits how long configuration discovery takes, and no new privilege or trust-boundary change is evident.

Retained concerns

• Medium · reliability · inferred: Sequential probes remove the scan's partial-result budget. A slow early probe can make configuration discovery return no editors and prevent later probes from running for that attempt.

Security review details

Security Blast Radius

• inferred — The demonstrated adverse outcome is incorrect editor availability in configuration responses. Its inputs are host environment and filesystem state; the inspected configuration call does not pass client-supplied command names into discovery.

Trust Boundaries and Controls

• inferred — The changed discovery code does not establish a new request parameter, execution sink, or identity transition. The existing configuration timeout still bounds the caller, but it no longer preserves completed editor results when the sequential scan exceeds that bound.

Resilience and Maintainability Implications

• observed — Failure or interruption before the cache write leaves the last completed entry intact for a later attempt; it does not make that entry the result of a caller whose discovery times out.

Hardening Proposals

• proposed — Restore bounded, independently progressing probes and preserve completed results on timeout, while retaining the rule that interrupted scans do not overwrite the completed cache.

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The current implementation does not fully address [#4697]. buildAvailableEditors probes editors sequentially, and the current code has no local four-second discovery budget or concurrent probes. A s…	Restore a bounded discovery strategy that prevents one slow probe from blocking the menu. Preserve the last complete editor result when a rescan is interrupted or times out. Add tests for slow probes and incomplete initial or repeat scans.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Out of Scope Changes check	✅ Passed	The current changes remain within [#4697]. They modify editor command discovery, PATH-directory listing, cache invalidation, and related tests. These changes directly target reliable detection of inst…
Title check	✅ Passed	The title clearly describes the main bug fix: installed editors remain available when discovery is slow.
Description check	✅ Passed	The description explains what changed, why it changed, the implementation details, validation results, and scope limitations. The UI checklist items are marked incomplete but explicitly identified as …

Full details: Linked Issues check

Explanation

The current implementation does not fully address [#4697]. buildAvailableEditors probes editors sequentially, and the current code has no local four-second discovery budget or concurrent probes. A slow probe can therefore reach the outer configuration timeout and return no editors on an initial scan. The current changes also remove partial-result retention, so no prior result exists to protect the menu on the first slow scan. The current tests no longer cover the removed stalled-probe and incomplete-rescan behavior.

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Inline comments:
In `@packages/shared/src/shell.ts`:
- Line 558: Update readPathDirectoryNames so a Windows candidate missing from a
cached directory listing is refreshed or probed directly before being skipped,
even when the reported millisecond mtime is unchanged. Preserve the cached fast
path for candidates present in the listing, and add a test covering a newly
added entry with an unchanged reported mtime.

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