Muse subscription for OpenCode (serverless)

Route OpenCode's coder / reviewer agents at your Muse coding
subscription. OpenCode calls https://api.meta.ai/v1 directly from its own
process — no local server, proxy, or background task.

Already have your Muse Code authenticated? Otherwise it does not work.
Run muse login (device-code OAuth) BEFORE installing. The installer
reuses that login's subscription key and refuses to continue without it.

Install

Windows:

powershell -NoProfile -ExecutionPolicy Bypass -File .\install.ps1

macOS / Linux:

sh ./install.sh

What it does:

1. Refuses unless muse is installed and ~/.config/muse/auth.json holds a
   subscription key.
2. Copies that key into OpenCode's auth.json as muse-sub (read from disk
   on every launch — no env-var timing issues).
3. Merges a muse-sub provider (muse-spark-1.3) plus coder/reviewer
   agent mappings into opencode.jsonc (or .json), preserving comments.
   A timestamped backup is kept next to the config; a failed merge restores
   it automatically. Existing entries are never overwritten.
4. Verifies against the live Meta API.

Then restart OpenCode. Re-run the installer whenever Muse rotates the key.

Notes

• Spend is metered to the Muse subscription (the API streams
  response.subscription_usage per call).
• Reasoning effort is the API default; per-model effort selection is not
  wired up.
• Uninstall: delete the muse-sub block from the provider section, the two
  agent mappings, and the muse-sub entry in auth.json.