SessionStart hook error on Windows: node:internal/modules/cjs/loader:1423 (non-blocking)

[flupkede]

Bug

On Windows, the SessionStart hook reports a non-blocking error at every startup:

SessionStart:startup hook error
Failed with non-blocking status code: node:internal/modules/cjs/loader:1423

The error is non-blocking — superpowers skill content IS correctly injected into the session, so the plugin functions normally. The error is purely cosmetic but appears on every session start.

Environment

• OS: Windows 11
• Claude Code: v2.1.142
• Superpowers: v5.1.0
• Username: develterf (no spaces — different from SessionStart hook fails on Windows when username contains spaces #1142)
• Shell: Git Bash (Git for Windows)

Details

The hook command configured in hooks/hooks.json:

"command": "\"${CLAUDE_PLUGIN_ROOT}/hooks/run-hook.cmd\" session-start"

The run-hook.cmd polyglot script successfully finds C:\Program Files\Git\bin\bash.exe and runs session-start, which outputs valid JSON (the context IS injected). Despite this, Claude Code's hook runner reports a failure with node:internal/modules/cjs/loader:1423 as the "status code".

node:internal/modules/cjs/loader:1423 is a Node.js internal module path — not a valid integer exit code — suggesting the error originates inside Claude Code's own Node.js hook-spawning code rather than from the bash process itself.

Related

• Similar Windows hook failure: SessionStart hook fails on Windows when username contains spaces #1142 (different root cause — spaces in username)

Suggested Investigation

• Does Claude Code's hook runner on Windows correctly capture the exit code from .cmd files spawned via Node.js child_process?
• Is the Node.js CJS loader error thrown when Claude Code attempts to resolve/spawn the hook command path on Windows?

Workaround

None available without patching the plugin cache (fragile, overwritten on update).

[mvanhorn]

Cross-linking anthropics/claude-code#59072 (filed yesterday) - paired-machine repro showing this is a v2.1.141 hook-spawn regression where Claude Code's Node dispatcher mangles backslashes in the hook command path. The node:internal/modules/cjs/loader:1423 string comes from that node process, not from run-hook.cmd (the polyglot never invokes node), so the fix has to land upstream.

[arittr]

Since this was filed, v6.2.0 changed the Windows SessionStart dispatch: the hook now declares shell: "bash" (5151e7a), so Claude Code 2.1.81+ runs the hook through Git Bash directly instead of the spawn path that produced this loader error, and the linked claude-code report has since been closed. Closing as resolved on current versions — if you still see the error with Superpowers 6.2.0+ on a current Claude Code, please reopen with the version pair. Thanks for the detailed report.