# LiteLLM

Use one recording path per request: the existing function callback, `VeqenLogger`, or the hosted logging endpoint. Combining them records the same request twice.

## Python and proxy CustomLogger

Install the SDK with LiteLLM support:

```bash
pip install 'veqen[litellm]>=1.1.0'
```

Create `veqen_callback.py` beside the proxy configuration:

```python
import veqen
from veqen.integrations.litellm_logger import VeqenLogger

veqen.init()  # reads VEQEN_API_KEY; use an ingest-only key
veqen_logger = VeqenLogger()
```

Register the instance in the proxy:

```yaml
litellm_settings:
  callbacks: [veqen_callback.veqen_logger]
```

For a Python application, set `litellm.callbacks = [VeqenLogger()]` after `veqen.init()`. The logger handles synchronous and asynchronous terminal callbacks. Intermediate streaming chunks and deployment-attempt hooks do not record additional calls. It queues only allowlisted model, usage, timing and attribution fields; prompts, responses, exception text and request headers are not copied.

Pass attribution in `metadata={"veqen": {"customer": "acme", "feature": "chat"}}`. Use pseudonymous identifiers, not customer contact details. CustomLogger observes completed calls; it cannot stop a call that has already run. Use Veqen's wrapper and budget checks for pre-call enforcement.

## Hosted logging endpoint

`POST https://veqen-app.com/v1/integrations/litellm` accepts a JSON array of LiteLLM `StandardLoggingPayload` records, or one record. Authenticate with `Authorization: Bearer <ingest-key>`. It shares the normal ingest rate and plan limits and accepts at most 1,000 records per request. Responses report `accepted`, `duplicates`, `dropped` and per-record `rejected` errors. Retries use LiteLLM's request identifier and completion timestamp, so an identical export is recorded once per organization.

The endpoint discards raw content, headers and arbitrary metadata. **Configure redaction at the sender too**: a generic HTTP logger can otherwise transmit model content before Veqen discards it. LiteLLM's `turn_off_message_logging: true` removes model content from its logging payload, but does not remove every metadata field. Prefer `VeqenLogger` when only cost metadata may leave your process. The built-in callback submission is separate from availability in a released LiteLLM version; do not configure a callback name your installed version does not recognize. Generic custom-endpoint logging may require a LiteLLM Enterprise license.

Normalized cache tokens come from the payload's `hidden_params.usage_object` or `metadata.usage_object`. If those details are absent, only the exported aggregate token counts are available. Known models are priced by Veqen's current price book or your custom prices; unknown models retain LiteLLM's reported cost, labeled `reported`. Neither calculation is proof of agreement with an invoice—use provider reconciliation. Proxy cache hits have no new provider charge and are recorded at zero cost.

See the [LiteLLM callback documentation](https://docs.litellm.ai/docs/observability/custom_callback), [logging specification](https://docs.litellm.ai/docs/proxy/logging_spec) and [redaction controls](https://docs.litellm.ai/docs/proxy/logging).