acp-background-runs

# ACP / Codex Background Runs

When a user asks to use ACP or an external coding agent such as Codex, Claude Code, Gemini CLI, or OpenCode, do not execute the task synchronously in the current chat. Route it through the ACP runtime instead.

## Default Rules

- Prefer `sessions_spawn` and set `runtime: "acp"` with the appropriate `agentId`
- Default to `mode: "run"`
- Only use `thread: true` or `mode: "session"` when the user explicitly asks for an ongoing interactive or thread-bound session
- Set `cwd` when the target repository or directory is known
- Prefer absolute paths for `cwd`; do not pass `~` directly, expand it first
- Use a relaxed `runTimeoutSeconds` for longer tasks; do not mechanically default to `300`
- Do not wait in the current conversation and do not poll for progress
- Reply immediately after submission that the task has been accepted and is running in the background
- Rely on `sessions_spawn` completion notifications to send the final result back to the current conversation
- Only add `streamTo: "parent"` when the user explicitly asks for progress updates

## Default Handling

If the user is simply dispatching an ACP / Codex task and does not explicitly request a persistent interactive session, treat it as a one-shot background run. Do not block the current conversation. Send the result back only when the background run completes.

## Timeout Guidance

- Quick read-only checks, short analysis, light tasks: `runTimeoutSeconds: 120-300`
- Normal coding tasks, project inspection, small scoped edits: `runTimeoutSeconds: 600`
- Research, code changes, file generation, test runs, longer reports: `runTimeoutSeconds: 1200`
- Clearly long-running tasks: increase further to `1800-3600` as needed
- Do not default to `0`; only use `0` when the user explicitly wants no timeout

## `mode` / `thread` Decision Rules

- If the user only wants the external agent to finish a task in the background, use `mode: "run"`
- If the user explicitly wants to continue talkin...