[vierja]

What

Adds Muse (Meta's muse CLI) as a ninth native harness in Zeron, driven through its own wire — the MSP session-host protocol (muse serve, JSON-RPC 2.0 over stdio) — the same way Codex is driven through its app-server. No ACP adapter in between.

• HarnessId::Muse (wire name "muse") in zeron-proto.
• New zeron-harness::MuseHarness (crates/harness/src/muse/):
  • Persistent muse serve host per session: initialize handshake, session/start / session/resume (with fresh-start fallback + notice when a session is gone), turn/start per prompt.
  • Streaming: item/delta / item/completed, session/todoListChanged, session/tokenUsage, session/contextUsage normalized into AgentEvents; completed text is reconciled against streamed deltas so nothing duplicates. turn/completed is the authoritative turn end (deterministic_turn_end).
  • Steering: turn/steer mid-turn (a steer that loses the race with turn end becomes the next turn/start), turn/interrupt on stop, model changes via session/setModel on the live host.
  • Server→client requests: approval/request and userInput/request are receipted immediately, then decided via approval/decide / userInput/answer after round-tripping Zeron's question panel. Unattended sessions (auto-approve / danger sandbox) start with approvalMode: allowAll so no approval ever blocks the queue; DangerFullAccess also launches the host with --disable-sandbox (sandbox posture is fixed at host start on this wire).
  • A leading /skill invocation the host advertises becomes a native MSP skill input part; image attachments are inlined as base64 parts; Zeron's MCP server is injected via session/start config. Command ids are UUIDv7, as the host requires.
  • Catalogs: model/list and skill/list probed over short-lived hosts; skills also surface as slash commands.
• Registration and naming everywhere a harness appears: engine default_registry (lazy slot mirroring the harness descriptor), harness-update provider table, agent-account slugs/CLI names, install tables (no script installer is known for Muse, so it is manual-only), skill discovery (.agents/skills), UI picker brand mark (new muse-mark.svg), Providers/settings rows, and the README agent list. The workspace uuid dependency gains the v7 feature for MSP command ids.

Deliberate v1 limits

• Titles: Muse has no tools-off title mode, so it does not claim supports_titles; title generation keeps falling back to the existing title-capable harnesses.
• Accounts: sign-in stays with muse login; Muse is not added to the Accounts providers until the engine can detect/swap its credentials.
• Subagent/workflow/reminder items render as spawn chips / are skipped where Zeron has no generic rendering; nested child transcripts are not subscribed yet.

Testing

• Unit: MSP normalizer (delta/completion reconciliation, tool open/settle, failed turns, todos) and model catalog parsing.
• Integration (crates/harness/tests/muse.rs, fake muse serve in tests/fixtures/fake-muse.py): echo turn, typed tool calls, failed turn error, native skill part, user-input round-trip, resume fallback notice, live catalog/skills, wire-name round-trip — 8 passed.
• Ignored live smokes against the real binary (run locally, all passing): model/list catalog and a full echo-provider turn end-to-end through MuseHarness.
• cargo check --workspace --all-targets clean; clippy clean in the new module; proto (76), engine registry (18), harness lib, and UI settings/pickers suites pass. Two timing tests in unrelated subsystems (executable version probe, harness-update installer) flake under full parallel load on this machine and pass in isolation.

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