pi-litellm

LiteLLM integration extensions for Pi. Provides model sync, accurate cost tracking, and session grouping when routing Pi through a LiteLLM proxy.

Features

Model Sync (litellm-sync.ts)

Keeps the Pi model selector in sync with LiteLLM's live model list. On startup (and on /reload), fetches GET /v1/models from LiteLLM and registers the provider with the exact model IDs that LiteLLM exposes.

Before: claude-opus-4.6 [litellm] (stale, doesn't match LiteLLM routing names) After: bedrock/claude-opus-4.6 [litellm], openrouter/claude-sonnet-4.6 [litellm]

Model capabilities (reasoning, context window, max tokens, thinking levels) are auto-detected from the model ID.

Cost Tracking (litellm-cost.ts)

Overrides Pi's static cost calculation with accurate pricing from LiteLLM:

1. Response header — Reads x-litellm-response-cost from each LLM response for exact per-request cost.
2. Model pricing fallback — At startup, fetches model pricing from LiteLLM's /model/info endpoint. When the response header isn't available (e.g., streaming), calculates cost from token counts × per-token rates.

Session Grouping (litellm-session.ts)

Injects litellm_session_id into every outgoing request payload so all API calls within one Pi session are grouped in LiteLLM's session logs. The session ID is derived from the Pi session filename.

Requires drop_params: true in your LiteLLM litellm_settings config.

Installation

pi install npm:pi-litellm

Or in .pi/settings.json:

{
  "packages": ["npm:pi-litellm"]
}

Configuration

Set environment variables (or configure in ~/.pi/agent/models.json):

Variable	Default	Description
LITELLM_BASE_URL	http://localhost:4000	LiteLLM proxy URL
LITELLM_API_KEY	sk-cedar-local	LiteLLM API key

models.json (optional)

If you prefer file-based config over env vars, add a litellm provider entry to ~/.pi/agent/models.json:

{
  "providers": {
    "litellm": {
      "baseUrl": "http://localhost:4000",
      "api": "anthropic-messages",
      "apiKey": "sk-cedar-local"
    }
  }
}

The sync extension reads baseUrl, apiKey, and api from this config. You do not need to define models here — they're populated dynamically from LiteLLM.

Priority: environment variables > models.json > defaults.

LiteLLM Setup

Your LiteLLM config.yaml should include:

litellm_settings:
  drop_params: true

This ensures:

• litellm_session_id is stripped before forwarding to upstream providers
• Unknown params from Pi don't cause upstream errors

How Model Sync Works

1. Extension loads as an async factory (runs before session_start)
2. Fetches GET /v1/models from LiteLLM → returns model_name values from config.yaml
3. Calls pi.registerProvider("litellm", { models: [...] }) with those exact IDs
4. On /reload, re-fetches and re-registers to pick up config changes

If LiteLLM is unreachable at startup, the extension logs a warning and skips registration — Pi continues with whatever models are already configured.

License

MIT