On Windows, an npm-installed `claude` resolves to a .cmd shim, so
_resolve_launch_command wraps it in `cmd.exe /d /s /c ...`. cmd.exe treats a
newline inside an argument as end-of-command, silently truncating a multiline
prompt at the first line break -- the agent received only the "## Task Brief"
heading and replied that no task was included.
Detect this case in _interactive_prompt_transport and deliver the prompt over
the existing stdin channel instead. The guard requires all three of: nt
platform, a newline in the prompt, and a command that resolves to .cmd/.bat.
It reuses _resolve_windows_command_shim so the check matches the same
resolution logic that decides whether cmd.exe wrapping happens.
Also records prompt_transport_reason in the stdin metadata to distinguish this
trigger from the pre-existing oversized-prompt path.
Verified against the real claude CLI: transport flips to stdin and the CLI
confirms all prompt lines arrive intact.
CatJuly
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