[Bug] Built-in Herdr reporter never connects on Windows, leaving panes stuck on Unknown

[vinchey]

Affected area

Coding agent and CLI

What happened?

Herdr listens on a named pipe on Windows, and the pipe name embeds the socket path. The built-in reporter in packages/coding-agent/src/core/extensions/builtin/herdr-agent-state.ts dials the bare HERDR_SOCKET_PATH:

const socket = createConnection(socketPath!);

On Windows that fails with ENOTSOCK. sendRequest treats every socket error as a completed send:

socket.on("error", finish);

so the failure is silent. A pane running Prime Agent inside Herdr stays Unknown forever with nothing logged, and Herdr's working/blocked/idle labelling never works on Windows.

Measured from inside a real Herdr pane:

\\.\pipe\<HERDR_SOCKET_PATH>  -> CONNECTED
<HERDR_SOCKET_PATH>          -> ENOTSOCK

Herdr's own file-based integration (herdr integration install pi) already applies the named-pipe transform, so the two disagree.

Steps to reproduce

1. On Windows, install Herdr and start a pane.
2. Run Prime Agent from a source checkout inside that pane.
3. herdr pane get <pane-id>
4. Observe "agent_status": "unknown" and no agent field, before and after sending a prompt.

Expected behavior

The pane reports idle, and transitions to working and back while a turn runs, the same way it does on macOS and Linux.

Prime Agent version

0.7.2 (source checkout, 9f95011)

Environment

Windows 11, Herdr 0.8.0-preview.2026-08-04, Windows Terminal / ConPTY

Additional context

packages/coding-agent/test/herdr-agent-state.test.ts cannot catch this, because it cannot run on Windows at all. Its fake server also listens on the bare path, so server.listen() throws EACCES before any assertion runs:

Tests  9 failed | 3 passed (12)

Applying the same transform in the test helper brings it to 12 passed, and reverting only the source change then gives 8 failed / 4 passed, so it becomes a real regression test rather than one that passes either way.

I have a working patch (6 lines of source, 11 of test) and verified it end to end in a Herdr pane:

before:  agent_status = unknown   agent = None
after:   agent_status = idle      agent = prime-agent
prompt:  working -> idle

npm run check passes. No protocol, command, or event shape changes. Happy to open a PR if a maintainer wants it; per CONTRIBUTING.md I am starting here instead.