pi-cursor-provider

Pi extension that provides access to Cursor models via OAuth authentication and a local OpenAI-compatible proxy.

How it works

pi  →  openai-completions  →  localhost:PORT/v1/chat/completions
                                      ↓
                              proxy.ts (HTTP server)
                                      ↓
                              h2-bridge.mjs (Node HTTP/2)
                                      ↓
                              api2.cursor.sh gRPC

1. PKCE OAuth — browser-based login to Cursor, no client secret needed
2. Model discovery — queries Cursor's GetUsableModels gRPC endpoint
3. Local proxy — translates OpenAI /v1/chat/completions to Cursor's protobuf/HTTP2 Connect protocol
4. Tool routing — rejects Cursor's native tools, exposes pi's tools via MCP

Install

# Via pi install
pi install npm:pi-cursor-provider

# Or manually
git clone https://github.com/ndraiman/pi-cursor-provider ~/.pi/agent/extensions/cursor-provider
cd ~/.pi/agent/extensions/cursor-provider
npm install

Usage

/login cursor     # authenticate via browser
/model            # select a Cursor model

Model Mapping

Cursor exposes many model variants that encode effort level (low, medium, high, xhigh, max, none) and speed (-fast) or thinking (-thinking) in the model ID. This extension deduplicates them so pi's reasoning effort setting controls the effort level.

How it works

Each raw Cursor model ID is parsed into components:

{base}-{effort}[-fast|-thinking]

Examples:

| Raw Cursor ID | Base | Effort | Variant | |---|---|---|---| | gpt-5.4-medium | gpt-5.4 | medium | — | | gpt-5.4-high-fast | gpt-5.4 | high | -fast | | claude-4.6-opus-max-thinking | claude-4.6-opus | max | -thinking | | gpt-5.1-codex-max-high | gpt-5.1-codex-max | high | — | | composer-2 | composer-2 | — | — |

Models sharing the same (base, variant) with ≥2 effort levels and a sensible default (medium or no-suffix) are collapsed into a single entry with supportsReasoningEffort: true. Pi's thinking level maps to the effort suffix:

| Pi Level | Cursor Suffix | |---|---| | minimal | none (if available) or low | | low | low | | medium | medium or no suffix (default) | | high | high | | xhigh | max (Claude) or xhigh (GPT) |

The proxy inserts the effort before -fast/-thinking:

pi selects: gpt-5.4-fast  +  effort: high  →  Cursor receives: gpt-5.4-high-fast
pi selects: gpt-5.4       +  effort: medium  →  Cursor receives: gpt-5.4-medium
pi selects: composer-2     +  (no effort)     →  Cursor receives: composer-2

When a group is collapsed, the proxy registers one model with supportsReasoningEffort: true and an internal effort map (see table above).

Collapsed when Cursor returns either:

• Multiple effort suffixes for the same (base, -fast, -thinking) group, or
• A single variant whose parsed effort suffix is non-empty (for example only claude-4.5-opus-high is listed). The suffix is removed from the displayed ID so Pi's reasoning-effort setting supplies it.

Left as-is (raw Cursor ID on that row, supportsReasoningEffort: false) when the group has one variant and the parsed effort suffix is empty—typically IDs with no effort segment, such as composer-2, gemini-3.1-pro, or kimi-k2.5.

Disabling the mapping

To see all raw Cursor model variants without dedup:

PI_CURSOR_RAW_MODELS=1 pi

Session Management

The proxy maintains conversation state per pi session, enabling multi-turn conversations with Cursor models while preserving forks, tool continuations, and interruptions correctly.

How it works

• Session tracking — pi's session ID is injected into requests via a before_provider_request hook. The proxy keys bridge state and stored conversation state from that real session ID.
• Checkpoints — Cursor returns a conversation checkpoint after completed turns. The proxy stores that checkpoint, plus the completed-turn count and a fingerprint of the completed structured history, and reuses it only when the incoming history still matches.
• Session-scoped state — real pi session state is kept in memory until explicit cleanup or process restart. Anonymous fallback state can still be TTL-evicted.
• Lifecycle cleanup — session state is cleaned up on pi lifecycle events such as session switch, fork, /tree, and shutdown.

Tool continuations

When Cursor pauses for a tool call, the proxy keeps the live upstream bridge open and waits for pi to send the tool result on the next request. That tool result is sent back into the same in-flight Cursor run, so the tool continuation stays part of the original user turn instead of inflating completed history.

Interruptions

If the client disconnects or interrupts a turn mid-stream, the proxy cancels the upstream Cursor run and does not commit the pending checkpoint. Checkpoints are only committed after a turn finishes successfully.

Session fork

When you navigate back in pi's session tree and branch from an earlier point, the proxy discards the stored checkpoint whenever the completed history no longer matches the stored checkpoint metadata. That includes both:

• completed turn count mismatches, and
• same-depth branch changes detected via completed-history fingerprint mismatch.

After discarding a stale checkpoint, the proxy reconstructs proper protobuf conversation turns from the message history pi sends, so Cursor sees the actual conversation structure at the fork point.

Session resume

Conversation state is stored in memory. If the proxy restarts, checkpoints are lost. On the next request, pi sends the full conversation history, and the proxy reconstructs structured protobuf turns from that history instead of relying on an inline plaintext fallback.

That reconstruction preserves:

• assistant messages
• tool calls
• tool results
• final assistant text after tool results

Requirements

• Pi
• Node.js >= 18
• Active Cursor subscription

Development

npm install
npm test

Debug log timeline

When PI_CURSOR_PROVIDER_DEBUG=1 is enabled, the proxy writes timestamped JSONL logs to os.tmpdir() by default. You can turn a log into a compact human-readable timeline with:

npm run debug:timeline -- --latest
npm run debug:timeline -- /path/to/pi-cursor-provider-debug-2026-04-08T14-06-07-565Z-41184.log

Add --json if you want the parsed summary as JSON instead of formatted text.

Credits

OAuth flow and gRPC proxy adapted from opencode-cursor by Ephraim Duncan.