openai/openai-python · error · ValueError

Expected a non-empty value for `completion_id` but received

Error message

Expected a non-empty value for `completion_id` but received {completion_id!r}

What it means

ChatCompletions.retrieve (sync) requires a truthy completion_id for GET /chat/completions/{completion_id}. The SDK validates required path parameters client-side and raises ValueError for None/empty values instead of sending a malformed URL.

Solutions

1. Capture the id at creation: `completion = client.chat.completions.create(...)`; store `completion.id` and pass it to retrieve.
2. Validate the stored id is a non-empty string before calling.
3. Make sure you pass `completion.id`, not the response object.

Example fix

# before
client.chat.completions.retrieve(completion_id="")
# after
completion = client.chat.completions.create(model="gpt-4o", messages=[...])
stored = completion.id
fetched = client.chat.completions.retrieve(completion_id=stored)

if not completion_id:
    raise ValueError("completion_id must be non-empty")
client.chat.completions.retrieve(completion_id)

def is_valid_id(value: object) -> bool:
    return isinstance(value, str) and value.startswith("chatcmpl-")

When it happens

Trigger: `client.chat.completions.retrieve("")` or passing a completion id variable that is None because the create call's response wasn't captured (`resp.id` missing) or a dict lookup failed.

Common situations: Storing completions for later retrieval but failing to persist `completion.id`; copy-pasting code with the placeholder `chatcmpl-abc123` left empty; passing the whole response object instead of `.id`.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

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AI-assisted analysis of openai/openai-python@9917c6e28e (2026-08-28). Data as JSON: /api/errors/23f3b90ff50b923e. Report an issue: GitHub.

Appendix: source

Thrown at src/openai/resources/chat/completions/completions.py:1380

        extra_body: Body | None = None,
        timeout: float | httpx2.Timeout | None | NotGiven = not_given,
    ) -> ChatCompletion:
        """Get a stored chat completion.

        Only Chat Completions that have been created with
        the `store` parameter set to `true` will be returned.

        Args:
          extra_headers: Send extra headers

          extra_query: Add additional query parameters to the request

          extra_body: Add additional JSON properties to the request

          timeout: Override the client-level default timeout for this request, in seconds
        """
        if not completion_id:
            raise ValueError(f"Expected a non-empty value for `completion_id` but received {completion_id!r}")
        return self._get(
            path_template("/chat/completions/{completion_id}", completion_id=completion_id),
            options=make_request_options(
                extra_headers=extra_headers,
                extra_query=extra_query,
                extra_body=extra_body,
                timeout=timeout,
                security={"bearer_auth": True},
            ),
            cast_to=ChatCompletion,
        )

    def update(
        self,
        completion_id: str,
        *,
        metadata: Optional[Metadata],
        # Use the following arguments if you need to pass additional parameters to the API that aren't available via kwargs.

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