hermes-cursor-acp

Use your Cursor subscription models (Claude, GPT, Grok, Gemini, Composer) as the model behind Hermes Agent.

Cursor doesn't expose a chat-completions API, but the Cursor CLI ships an ACP server (agent acp). This plugin drives it through Hermes' ACP shim. Hermes keeps its own tools, memory, and skills. Cursor only supplies the model.

How it works

Hermes tool schemas go to the model as text. The model replies with <tool_call> blocks, and Hermes runs those calls itself.
The plugin parses tool calls with its own extractor. Hermes' built-in bridge silently drops two common shapes: the flat {"name", "arguments"} form, and a real block that follows a mention of <tool_call> in prose.
The plugin rewrites .cursor/cli.json in an empty private workspace ($HERMES_HOME/cache/cursor-acp-workspace) every time a client starts, with a deny-all list (Read, Write, Shell, WebFetch, Mcp). This deny list is the security fence. Cursor's native tools run inside the CLI rather than over ACP, and without the list its Read tool can open any absolute path on disk.
Models can be chosen by bare name (claude-opus-5-5) or by full advertised id (claude-opus-5-5[context=300k,effort=high,fast=false]). An unknown name raises an error instead of silently using Cursor's default.
Responses report usage=None. Cursor sends no token counts, and a zero reading would stall Hermes' proactive context compression.

Install

Option 1: One-command install (recommended)

npx hermes-cursor-acp

This installs and enables the plugin in Hermes, verifies your Cursor CLI (agent) installation, and checks that your subscription models are accessible.

Option 2: Manual install

curl https://cursor.com/install -fsS | bash   # Cursor CLI
agent login                                   # sign in with your Cursor account
agent models                                  # confirm what your plan offers

git clone git@github.com:neerazz/hermes-cursor-acp.git ~/.hermes/plugins/cursor-acp
hermes plugins enable cursor-acp

Use

hermes --provider cursor-acp -m claude-opus-5-5

Or run /model inside Hermes and pick Cursor Subscription (ACP).

Settings (env)

Variable	Default	Purpose
`HERMES_CURSOR_ACP_COMMAND`	`agent`	Path to the Cursor CLI
`HERMES_CURSOR_ACP_ARGS`	`acp`	Argv tail
`HERMES_CURSOR_ACP_MODE`	`agent`	Cursor session mode. `ask` made gpt-5.6-sol refuse the bridge 2 times in 5.
`HERMES_CURSOR_ACP_CWD`	`$HERMES_HOME/cache/cursor-acp-workspace`	Private workspace

Tests

H=~/.hermes/hermes-agent
PYTHONPATH=$H uv run --no-project --python $H/venv/bin/python --with pytest python -m pytest tests -q -o addopts=
CURSOR_LIVE=1 ...   # adds live tests against the real CLI (needs `agent login`)

Live results on 2026-10-06 (Hermes v0.21.5, Cursor CLI 2026.10.01):

Hermes tool-call bridging over 6 trials per model: claude-sonnet-5-5 6/6, claude-opus-5-5 6/6, composer-2.5 6/6, grok-4.7 6/6, gpt-5.6-sol 5/6. The one gpt miss answered from context without calling the tool.
Fence probes sent as raw prompts, so the model was told to escape: Cursor's native Read, Grep, Shell, Write, and WebFetch were all blocked. The canary file content and a live GitHub SHA never came back.
End-to-end multi-step runs through hermes chat (read_file, then terminal) executed both tools for real with composer-2.5 and gpt-5.6-sol.

Known limits

Every turn starts a new ACP session. That adds 7–16s of latency and about 17k tokens of Cursor's harness prompt.
Hermes records no token or cost data for these calls, so /usage and /insights undercount.
When several sessions start at once, Cursor occasionally answers set_model with Internal error. The plugin retries up to 3 times.

License

MIT

cursor-acp

README