Daemon Backend Cursor

Cursor Daemon Backend — Flag Discovery Entrypoint

The installed CLI's own help is the authority for Cursor Agent flags; this page is only the entrypoint. Conversion rules live in the parent reference/cli-backends/SKILL.md.

Discover flags from the installed CLI

1. Run agent --version and agent --help in bash. The daemon spawns root agent directly (the root binary is agent; older docs said cursor-agent) — agent -p --force --output-format stream-json <prompt> — so root help is authoritative (keychain errors happen before help on some builds).
2. Translate what you found into backend_options with the parent's generic conversion rules (nothing Cursor-specific is added).

Example: model selection via the generic route

backend_options keys become long flags, inserted after the harness-owned flags and before the task prompt:

{
  "backend": "cursor",
  "tasks": [{
    "task": "Implement and validate the change.",
    "tools": [],
    "backend_options": {
      "model": "opus"
    }
  }]
}
// argv: --model opus

The flag and model vocabulary belong to the installed CLI — LingTai does not validate, enumerate, or simulate them. Confirm --model and its accepted values in your installed agent --help before relying on this; an unknown flag or value is the CLI's error, not the daemon's.

Source-pinned stream-json usage

For installed agent-cli@2026.05.28-a70ca7c, accept usage only from type=result, subtype=success, is_error=false with all four non-negative integer fields: inputTokens, outputTokens, cacheReadTokens, cacheWriteTokens. inputTokens is already net; UI-only cli_tokens adds read + write as cached, preserves raw usage, ignores invalid/all-zero blocks, and counts duplicate terminal results once. Join model only from a preceding matching system/init by session_id; provider stays unknown because this source emits no provider identity (do not infer it from apiKeySource, model, backend, credentials, or environment). This is version-pinned, not a cross-release claim.

Subscription & auth

Cursor account/subscription (keychain login); LingTai does not inject credentials — the CLI must be signed in.

Official docs: https://docs.cursor.com/agent

Harness boundary

Cursor declares no reserved-flag list at validation, so nothing is refused beyond generic key/value safety rules. Still, do not re-set harness-owned surfaces: -p (non-interactive print mode), --force (allows file modifications in print mode), --output-format stream-json (one JSON event per stdout line — the daemon's progress/result parser and the session-id capture depend on it), and --resume (owned by ask follow-ups, which replay the captured session id).

Session and completion: the first session-id-shaped stream event is stored as cursor_session_id; ask resumes with agent -p --force --resume <cursor_session_id> --output-format stream-json <message> (one follow-up in flight per session). Per-run MCP injection is not wired for this backend yet, so no finish contract: success comes from the stream's final result event and the process exit code.

backend_options is honored only at emanate time; ask follow-ups reuse the session without re-passing it.