[rudycelekli]

When the watcher cannot start gh at all, for example because it is not on PATH or the spawn fails with a system error, the spawn error escapes run() as a raw rejection. Nothing above it converts that into a WatcherQueryError, so the CLI dies with an uncaught stack trace and never prints a JSON verdict. Callers that expect the documented status-query BLOCKER (exit 7, "verify current PR context, GitHub authentication, and API availability") get a crash instead. Under Bun the error is thrown synchronously from spawn; under Node it arrives as an error event, and neither path was handled.

run() now treats a command that cannot start the same as one that exits nonzero: it resolves with code -1 and the spawn error as stderr. The existing runJson path then raises a command-exit query failure, so the error goes through the normal retry budget and ends as a status-query BLOCKER whose detail names the problem (for example Executable not found in $PATH: "gh"). Callers that already check code !== 0, such as the origin and checks fast paths, fall back as they do for any other failed command.

Validation: added a github.test.ts case that runs GhGitHubReader.pullRequest in a subprocess with a PATH that has no gh. On main it receives the raw "Executable not found" error; with the fix it receives a command-exit WatcherQueryError. Running the CLI by hand with --status-only and no gh on PATH now prints the BLOCKER JSON and exits 7 instead of a stack trace. Ran bun test watch-pr check-plan.test.ts (62 pass), bun run typecheck, node scripts/validate-plugins.mjs, node scripts/generate-pstack-harness-trees.mjs --check, node --test pstack/skills/*/scripts/test/*.test.mjs (57 pass), and git diff --check.

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Note

Low Risk
Narrow change to subprocess error handling in the GitHub CLI wrapper; improves fail-closed behavior without altering successful gh paths.

Overview
When gh cannot be started (missing from PATH, spawn failure), the watch-pr GitHub helper no longer lets that error bubble out as an uncaught rejection.

run() now treats “command failed to start” like a nonzero exit: it resolves with code: -1 and the error text in stderr, covering Bun’s synchronous spawn throw and Node’s error event. runJson then raises the existing command-exit WatcherQueryError, so the CLI can surface the usual status-query BLOCKER (exit 7) instead of crashing.

A subprocess test runs GhGitHubReader.pullRequest with a PATH that has no gh and expects command-exit rather than a raw executable-not-found string.

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