BerriAI/litellm · error · RuntimeError

Error parsing chunk: {e}, Received chunk: {chunk}

Error message

Error parsing chunk: {e},
Received chunk: {chunk}

What it means

RuntimeError from the sync Anthropic stream iterator's parsing stage: after a raw line is successfully fetched, converting it into a GenericStreamingChunk raised a ValueError, and the handler re-raises it as RuntimeError including both the error and the raw chunk. The ' Received chunk:' part is the debugging gold — it shows the exact payload that could not be parsed.

Source

Thrown at litellm/llms/anthropic/chat/handler.py:1141

                if str_line.startswith("data:"):
                    result = self._parse_sse_data(str_line)
                    if result is not None:
                        return result
                    # If None, continue loop to get more chunks for accumulation
                else:
                    return GenericStreamingChunk(
                        text="",
                        is_finished=False,
                        finish_reason="",
                        usage=None,
                        index=0,
                        tool_use=None,
                    )
            except StopIteration:
                raise StopIteration
            except ValueError as e:
                raise RuntimeError(f"Error parsing chunk: {e},\nReceived chunk: {chunk}")

    # Async iterator
    def __aiter__(self):
        self.async_response_iterator = self.streaming_response.__aiter__()
        return self

    async def __anext__(self):
        while True:
            try:
                chunk = await self.async_response_iterator.__anext__()
            except StopAsyncIteration:
                # If we have accumulated JSON when stream ends, try to parse it
                if self.accumulated_json:
                    try:
                        data_json = json.loads(self.accumulated_json)
                        self.accumulated_json = ""
                        return self.chunk_parser(chunk=data_json)
                    except json.JSONDecodeError:

View on GitHub (pinned to 6c2dcb801b)

Solutions

1. Look at 'Received chunk:' in the message to see the exact malformed payload and identify its origin (OpenAI-style, HTML, truncated).
2. If the chunk looks like OpenAI SSE ('"choices": [...]'), remove the anthropic/ prefix or fix the model routing so the OpenAI transformation is used.
3. If the chunk is truncated JSON, check for proxy buffering/read-timeout settings that cut the stream early.
4. Reproduce with stream=False against the same endpoint to inspect the full response body.
5. Catch RuntimeError around stream consumption and degrade gracefully (keep partial content, surface the error to the user).

Example fix

# before
result = "".join(c.choices[0].delta.content or "" for c in resp)

# after
result = []
try:
    for c in resp:
        if c.choices and c.choices[0].delta.content:
            result.append(c.choices[0].delta.content)
except RuntimeError as e:
    log.warning("anthropic stream parse failure: %s", e)
print("".join(result))

collected = []
try:
    for chunk in stream:
        collected.append(chunk)
except RuntimeError as e:
    if "Error parsing chunk" in str(e):
        log.error("unparseable frame: %s", e)  # includes raw chunk
        return merge_partial(collected)  # graceful degradation
    raise

When it happens

Trigger: Sync streaming where a 'data:' line's JSON parses but its shape is unexpected (missing fields the parser expects, unexpected event type), or where the chunk text is not valid JSON (e.g. 'data: [DONE]' style payloads from an OpenAI-format upstream served under an anthropic/ model prefix).

Common situations: Pointing anthropic/ models at OpenAI-compatible or mock servers; API format drift after an Anthropic API version change; gateways that append trailers or rewrite events; testing with recorded/replayed SSE fixtures that were truncated.

Related errors

• Failed to decode JSON from chunk: {chunk}
• Error receiving chunk from stream: {e}
• Error parsing chunk: {e}, Received chunk: {chunk}
• Received streaming error - {e}
• error_message or raw_response.text

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/266f59c67721513c. Report an issue: GitHub.