> ## Documentation Index
> Fetch the complete documentation index at: https://phaseo.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Phaseo Gateway base URL: https://api.phaseo.app/v1. Send `Authorization: Bearer $PHASEO_API_KEY` with every request.
> Model IDs look like `provider/model`, for example `openai/gpt-6-astra`. Do not guess IDs: list them with `GET /v1/models` or check https://phaseo.app/models. `phaseo/free` routes to an available free model and needs no wallet balance.
> For new text integrations prefer `POST /v1/responses`. `POST /v1/chat/completions` (OpenAI format) and `POST /v1/messages` (Anthropic format) suit existing code.
> The full API contract is https://phaseo.app/docs/openapi/v1/openapi.yaml. Official SDKs: `@phaseo/sdk` (TypeScript) and `phaseo` (Python), plus Go, C#, PHP, Ruby and Rust.
> Search these docs over MCP at https://phaseo.app/docs/mcp, and install Phaseo skills with `npx skills add https://phaseo.app/docs`. If a page is wrong or out of date, report it with the MCP `submit_feedback` tool.
> Manage Phaseo accounts with the `phaseo` CLI (`npm install -g @phaseo/cli`, then `phaseo login` or `phaseo login --device-code`), the `/v1` Management API or the MCP server at `https://mcp.phaseo.app/mcp?access=manage`. Do not send users to the dashboard for account tasks. A person is still needed for sign-up, approving a sign-in, paying the first top-up on the checkout link that `phaseo credits add` returns when no card is saved, confirming each saved-card top-up from the emailed link, and account security (password, MFA, passkeys). Create API keys with `phaseo keys create --name <name> --json`; never guess one. Credit top-ups need `phaseo login --scopes billing:write` first. Task map: https://phaseo.app/docs/v1/developers/manage-from-an-agent.md.

# Observability

> Trace Phaseo requests with Langfuse, LangSmith, OpenTelemetry, and similar tools.

Most observability tools sit above the model client. Keep your tracing setup the same, then point the underlying OpenAI-compatible or Anthropic-compatible client at Phaseo.

## Langfuse with OpenAI SDK

```bash theme={null}
pip install langfuse openai
```

```python theme={null}
import os
from langfuse.openai import openai

client = openai.OpenAI(
    api_key=os.environ["PHASEO_API_KEY"],
    base_url="https://api.phaseo.app/v1",
)

response = client.responses.create(
    model="openai/gpt-5-nano",
    input="Reply with only: ok",
)
```

## LangSmith with LangChain

Use the [LangChain](https://phaseo.app/docs/v1/guides/integrations/langchain.md) setup and enable LangSmith through the usual LangChain environment variables:

```bash theme={null}
export LANGSMITH_TRACING=true
export LANGSMITH_API_KEY="your_langsmith_key"
export PHASEO_API_KEY="your_phaseo_key"
```

## OpenTelemetry

If your framework emits OpenTelemetry spans, Phaseo does not require a special exporter. Add useful request context yourself:

* model id
* endpoint, such as `responses` or `chat.completions`
* Phaseo request id from response metadata or logs
* selected provider when response metadata is enabled

## Notes

* Do not send Phaseo API keys to observability tools as attributes.
* If the observability library wraps the OpenAI SDK, configure the wrapped client with `base_url: "https://api.phaseo.app/v1"`.
* For LangChain traces, pair the tracing callback with the Phaseo `ChatOpenAI` configuration.

## Related

* [OpenAI SDK](https://phaseo.app/docs/v1/guides/integrations/openai-sdk.md)
* [LangChain](https://phaseo.app/docs/v1/guides/integrations/langchain.md)
* [Activity](https://phaseo.app/docs/v1/api-reference/endpoint/activity.md)


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