Muse Code

Signet connects to Muse Code, Meta’s terminal coding agent, through its settings-file hooks and MCP server registry.

Setup

Select Muse Code in the interactive wizard, or run:

signet setup --harness muse-code

The connector edits ~/.config/muse/settings.json (or $XDG_CONFIG_HOME/muse/settings.json). It adds Signet hook groups under hooks and a signet entry under mcp_servers, and leaves model settings, other hooks, and other MCP servers untouched. Re-running setup replaces only Signet-owned entries.

Muse requires "schema_version": 1 in that file. When the file is missing, Signet creates it with that version. Setup refuses to modify the file, and reports why, in these cases:

• it is not valid JSON;
• it lacks schema_version: 1;
• hooks or mcp_servers is not an object;
• a hook group is not an object with a hooks array of objects, or a handler timeout is not a non-negative integer.

Muse rejects the first three outright, and either of the last problems disables every hook in the file. Other handler problems, such as a missing command, make Muse skip only that handler, so setup leaves them alone. Fix the file first. A symlinked settings.json is updated at its target.

Signet detects Muse from its config directory, its data directory (~/.local/share/muse), or a muse binary on PATH.

Hook behavior

Muse event	Signet command	Effect
SessionStart	signet hook session-start -H muse-code --codex-json	Injects identity and recalled context as a developer context block.
UserPromptSubmit	signet hook user-prompt-submit -H muse-code --codex-json	Injects prompt-time recall and clock context.
Stop	signet hook session-end -H muse-code	Records a turn checkpoint and runs deferred session-end work.

Context hooks emit hookSpecificOutput.additionalContext JSON. Muse parses hook stdout as JSON whenever it starts with [ or {, so plain Signet context, which begins with [signet active], would be rejected as malformed.

Signet uses Stop instead of SessionEnd. Muse cancels unfinished SessionEnd hooks within about half a second of its shutdown budget, which is shorter than the Signet CLI needs to start. Muse’s SessionEnd payload carries reason: "other", which the daemon treats as a turn checkpoint, so Stop delivers the same request at a point where it can complete.

Muse sends transcript_path: null in hook payloads, so Signet records Muse sessions from the hook stream keyed by Muse’s session_id: each prompt from UserPromptSubmit, and each turn’s final assistant reply from the last_assistant_message field of Stop. Intermediate assistant text and tool calls within a turn are not recorded, and Signet does not read Muse’s own session log. PreCompact is not installed.

Environment

Muse starts hook commands and MCP servers with a cleared environment. Hooks keep only HOME, PATH, USER, SHELL, TERM, LANG, PWD, and LOGNAME. Setup therefore writes the same set of values into each hook command and into the MCP entry’s env block, so both reach the same daemon and workspace:

• SIGNET_PATH is always set to the absolute workspace path selected during setup.
• SIGNET_DAEMON_URL is set when the resolved daemon address differs from http://127.0.0.1:3850, including SIGNET_HOST/SIGNET_PORT overrides.
• SIGNET_API_KEY is set when it is present at setup time, and is then stored in settings.json in plain text. A settings file that Signet creates is written with mode 0600. Signet does not change the mode of an existing file.
• SIGNET_SESSION_START_TIMEOUT, SIGNET_FETCH_TIMEOUT, and SIGNET_PROMPT_SUBMIT_TIMEOUT are carried over when set, and size the hook timeouts.

When setup runs from the native signet binary, the hooks and the MCP server use that same binary path. Otherwise the hooks call signet from PATH. The MCP entry is registered with mode: "optional". A required server that fails to start aborts every Muse run; an optional one is skipped with a startup warning.

Re-run setup after changing the workspace, daemon address, API key, or timeouts.

Agent identity

signet hook user-prompt-submit and session-end have no agent option, so Muse hooks write as the daemon’s default agent. Setup refuses when SIGNET_AGENT_ID names another agent, rather than splitting a session between agents.

Skills

Muse discovers skills from ~/.agents/skills on its own, so Signet does not link a skills directory. If your Signet workspace is not ~/.agents, setup warns that workspace skills are not visible to Muse.

Platform support

Setup is supported on macOS and Linux. On Windows, Muse runs hooks through PowerShell, and setup refuses rather than writing POSIX hook commands.

Remove the integration

Disconnect Muse Code from the dashboard’s harness list, or run the connector’s uninstall command:

bunx @signetai/connector-muse-code uninstall

Uninstall removes only Signet-owned hooks and the signet MCP entry, and keeps schema_version and the rest of the file. If the file cannot be parsed, uninstall fails with the reason instead of reporting success.