Bug Report: Claude Code Stop hook does not receive stdin on Windows (PowerShell 5.1 + pwsh 7)

Reporters: Kousei Izumida & ClaudeChat (Claude Sonnet 4.6)

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Environment

• OS: Windows 11
• PowerShell: 5.1.26100.8115
• Claude Code: v2.1.101
• pwsh: 7.x (C:\Program Files\PowerShell\7\pwsh.exe)
• bash: not present (where.exe bash returns no result)

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Issue Summary

The Stop hook does not deliver stdin to the handler script on Windows when using pwsh as the executor.

Specifically:

• [Console]::IsInputRedirected returns False inside the hook script
• A full diagnostic dump script (checking stdin, environment variables, and command-line arguments) produced an empty log file
• No data was received through any channel

The UserPromptSubmit hook using identical pwsh configuration works correctly and returns additionalContext as expected.

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Configuration (settings.json hooks section)

"hooks": {
  "UserPromptSubmit": [{
    "hooks": [{
      "type": "command",
      "command": "pwsh -ExecutionPolicy Bypass -File C:\Users\kouse\.claude\hooks\inject-constraints.ps1"
    }]
  }],
  "Stop": [{
    "hooks": [{
      "type": "command",
      "command": "pwsh -ExecutionPolicy Bypass -File C:\Users\kouse\.claude\hooks\block-self-judgment.ps1"
    }]
  }]
}

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Steps to Reproduce

1. Install Claude Code v2.1.101 on Windows with pwsh 7 (no bash)
2. Register a Stop hook pointing to a pwsh script
3. In the script, check [Console]::IsInputRedirected and log all incoming data
4. Trigger the Stop hook by completing a Claude Code session turn
5. Observe: log file is empty, IsInputRedirected = False

Expected: Stop hook receives JSON context via stdin as documented
Actual: stdin is empty, IsInputRedirected = False

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Note

We are using hooks to enforce output constraints (blocking self-judgment phrases) as a governance layer for an AI automation pipeline. This issue prevents the Stop hook from functioning as a structural safety gate on Windows.

We would appreciate guidance on:

1. Whether stdin delivery for Stop hooks is supported on Windows
2. Whether there is an alternative delivery method (env vars, args) on Windows
3. Whether this is a known issue with a workaround

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Sincerely,
Kousei Izumida & ClaudeChat
MIRAI AI Orchestra
Iwaki, Fukushima, Japan