feat: add OpenRouter proxy for Cursor CLI agent#3087
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Cursor CLI uses a proprietary ConnectRPC/protobuf protocol with BiDi
streaming over HTTP/2. It validates API keys against Cursor's own servers
and hardcodes api2.cursor.sh for agent streaming — making direct
OpenRouter integration impossible.
This adds a local translation proxy that intercepts Cursor's protocol
and routes LLM traffic through OpenRouter:
Architecture:
Cursor CLI → Caddy (HTTPS/H2, port 443) → split routing:
/agent.v1.AgentService/* → H2C Node.js (BiDi streaming → OpenRouter)
everything else → HTTP/1.1 Node.js (fake auth, models, config)
Key components:
- cursor-proxy.ts: proxy scripts + deployment functions
- Caddy reverse proxy for TLS + HTTP/2 termination
- /etc/hosts spoofing to intercept api2.cursor.sh
- Hand-rolled protobuf codec for AgentServerMessage format
- SSE stream translation (OpenRouter → ConnectRPC protobuf frames)
Proto schemas reverse-engineered from Cursor CLI binary v2026.03.25:
- AgentServerMessage.InteractionUpdate.TextDeltaUpdate.text
- agent.v1.ModelDetails (model_id, display_model_id, display_name)
- TurnEndedUpdate (input_tokens, output_tokens)
Tested end-to-end on Sprite VM: Cursor CLI printed proxy response with
EXIT=0.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Adds a local ConnectRPC-to-REST translation proxy that enables Cursor CLI to route LLM traffic through OpenRouter, bypassing Cursor's proprietary protocol lock-in.
Architecture
How it works
configure()— installs Caddy, uploads Node.js proxy scripts, configures hosts spoofingpreLaunch()— starts Caddy + two Node.js backends (systemd or setsid fallback)/v1/chat/completions(streaming) → encodes response asAgentServerMessageprotobuf framesProto schemas (reverse-engineered from CLI binary)
AgentServerMessage.InteractionUpdate.TextDeltaUpdate.textfor streaming textagent.v1.ModelDetails(model_id=1, display_model_id=3, display_name=4) for model listTurnEndedUpdate(field 14) for turn completionNew files
packages/cli/src/shared/cursor-proxy.ts— proxy scripts + deployment functionspackages/cli/src/__tests__/cursor-proxy.test.ts— 17 tests (protobuf, framing, deployment)Verified
Test plan
spawn cursor sprite→ verify proxy starts, Cursor CLI launchesspawn cursor hetzner→ verify works on non-Sprite cloud🤖 Generated with Claude Code