BerriAI/litellm · error · Exception

Error fetching prompt version

Error message

Error fetching prompt version '{prompt_version_id}': {e}

What it means

Companion branch in ArizePhoenixClient.get_prompt_version: raised when the caught exception has no attached HTTP response — i.e. the request never completed. Typical causes are DNS resolution failure, connection refused, TLS errors, or timeouts raised by httpx before/transport-level, rather than a Phoenix status code.

Solutions

  1. Verify Phoenix is reachable from where litellm runs: `curl <api_base>/prompt_versions -H "Authorization: Bearer $PHOENIX_API_KEY"`
  2. Fix the api_base hostname/port; for local dev, ensure Phoenix is actually listening on 6006
  3. If behind a proxy, configure HTTPS_PROXY/HTTP_PROXY for the process or extend the client's timeout
Defensive patterns

Strategy: retry

Validate before calling

import httpx, os

try:
    httpx.get(f"{api_base}/prompt_versions", headers={"Authorization": f"Bearer {os.environ['PHOENIX_API_KEY']}"}, timeout=5)
except httpx.ConnectError:
    raise SystemExit(f"Phoenix unreachable at {api_base} — check host/port/network before enabling prompts")

Try / catch

try:
    manager.compile(prompt_id=prompt_id, prompt_variables=vars)
except Exception as e:
    msg = str(e)
    if "Error fetching prompt version" in msg and any(k in msg for k in ("Connect", "DNS", "timeout")):
        # transport-level: safe to retry after a short backoff; if persistent, fix network/api_base
        time.sleep(2)
        return manager.compile(prompt_id=prompt_id, prompt_variables=vars)
    raise

Prevention

When it happens

Trigger: api_base host unreachable (wrong hostname, Phoenix not running locally, network policy blocking egress), DNS failure, or a slow Phoenix causing the client timeout while GETting the prompt version.

Common situations: Local development with Phoenix not started (connection refused on localhost:6006); typo in api_base; k8s NetworkPolicy blocking the proxy-to-Phoenix path; corporate proxy/MTLS requirements not configured for the httpx client.

Related errors

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/8cc4b95f342ac2da. Report an issue: GitHub.

Appendix: source

Thrown at litellm/integrations/arize/arize_phoenix_client.py:92

            data: Final = response.json()
            return data.get("data")

        except Exception as e:
            # Check if it's an HTTP error
            response = getattr(e, "response", None)
            if response is not None and hasattr(response, "status_code"):
                if response.status_code == 404:
                    return None
                elif response.status_code == 403:
                    raise Exception(
                        f"Access denied to prompt version '{prompt_version_id}'. Check your Arize Phoenix permissions."
                    )
                elif response.status_code == 401:
                    raise Exception("Authentication failed. Check your Arize Phoenix API key and permissions.")
                else:
                    raise Exception(f"Failed to fetch prompt version '{prompt_version_id}': {e}")
            else:
                raise Exception(f"Error fetching prompt version '{prompt_version_id}': {e}")

    def test_connection(self) -> bool:
        """
        Test the connection to the Arize Phoenix API.

        Returns:
            True if connection is successful, False otherwise
        """
        try:
            # Try to access the prompt_versions endpoint to test connection
            url: Final = f"{self.api_base}/prompt_versions"
            response: Final = self.http_handler.client.get(url, headers=self.headers)
            response.raise_for_status()
            return True
        except Exception:
            return False

    def close(self):

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