✗ WRONG

litellm 1.105.5

stream.missing-finish · anthropic

Requirements

Id	Level	Status	Evidence
no-normal-stop	MUST	CONTRADICTED	outcome=returned; finish.value="stop" (primary: choices[0].finish_reason); truth.finish="none"; forbidden finish="stop"
stream-incomplete	MUST	NOT_OBSERVABLE	stream.completed=null; outcome=returned; truth.stream_completed=false

What the provider sent

Finish: none
Raw finish: null
Text: Octopuses change colour by
Tool calls: []
Usage: { "alternatives": {}, "cached_input": null, "input": 25, "output": 1, "raw": { "input_tokens": 25, "output_tokens": 1 }, "reasoning": null, "total": 26 }
Stream completed: false
Error: null

Wire excerpt

status: 200
content-type: text/event-stream
body (sse):
event: message_start
data: {"type": "message_start", "message": {"id": "msg_01Aq9w938a90dw8q", "type": "message", "role": "assistant", "content": [], "model": "claude-sonnet-5-5", "stop_reason": null, "stop_sequence": null, "usage": {"input_tokens": 25, "output_tokens": 1}}}


event: content_block_start
data: {"type": "content_block_start", "index": 0, "content_block": {"type": "thinking", "thinking": "", "signature": ""}}


event: ping
data: {"type": "ping"}


event: content_block_delta
data: {"type": "content_block_delta", "index": 0, "delta": {"type": "thinking_delta", "thinking": ""}}


event: content_block_delta
data: {"type": "content_block_delta", "index": 0, "delta": {"type": "signature_delta", "signature": "EqQBCgIYAhIM1gbcDa9GJwZA2b3hGgxBdjrkzLoky3dl1pkiMOYds..."}}


event: content_block_stop
data: {"type": "content_block_stop", "index": 0}


event: content_block_start
data: {"type": "content_block_start", "index": 1, "content_block": {"type": "text", "text": ""}}


event: content_block_delta
data: {"type": "content_block_delta", "index": 1, "delta": {"type": "text_delta", "text": "Octopuses "}}


event: content_block_delta
data: {"type": "content_block_delta", "index": 1, "delta": {"type": "text_delta", "text": "change colour by"}}


event: content_block_stop
data: {"type": "content_block_stop", "index": 1}

What the library reported

Outcome

returned

Finish

{
  "raw": "stop",
  "source": "choices[0].finish_reason",
  "surface": "primary",
  "value": "stop"
}

Text

Value: Octopuses change colour by
Surface: primary

Tool calls

[]

Usage

{
  "cached_input": null,
  "input": null,
  "output": null,
  "reasoning": null,
  "surface": {
    "cached_input": "absent",
    "input": "absent",
    "output": "absent",
    "reasoning": "absent",
    "total": "absent"
  },
  "total": null
}

Stream

{
  "chunks_seen": 4,
  "completed": null,
  "used": true
}

Error

null

Unsupported reason

null

Full observation JSON

{
  "elapsed_ms": 605.4759901016951,
  "error": null,
  "finish": {
    "raw": "stop",
    "source": "choices[0].finish_reason",
    "surface": "primary",
    "value": "stop"
  },
  "format": "wiretruth.observation/v1",
  "library": {
    "api": "litellm.completion",
    "language": "python",
    "name": "litellm",
    "version": "1.105.5"
  },
  "notes": [],
  "outcome": "returned",
  "stream": {
    "chunks_seen": 4,
    "completed": null,
    "used": true
  },
  "structured": {
    "attempted": false,
    "returned_as_success": false,
    "value": null
  },
  "text": {
    "surface": "primary",
    "value": "Octopuses change colour by"
  },
  "tool_calls": [],
  "unsupported_reason": null,
  "usage": {
    "cached_input": null,
    "input": null,
    "output": null,
    "reasoning": null,
    "surface": {
      "cached_input": "absent",
      "input": "absent",
      "output": "absent",
      "reasoning": "absent",
      "total": "absent"
    },
    "total": null
  }
}

Fixture

derived anthropic/stream.missing-finish

Provenance	Value
Transform	strip_finish
Source fixture	anthropic/truncation.text-stream
Rationale	The stream ends cleanly without its finish signal.
Evidence	https://platform.claude.com/docs/en/build-with-claude/streaming#event-types

Reproduce

wiretruth serve anthropic/stream.missing-finish

Plain-library snippet from the shim manifest.

litellm.completion(model='anthropic/' + model, api_base=WIRETRUTH_BASE_URL_ANTHROPIC, api_key=WIRETRUTH_API_KEY); host root, LiteLLM appends /v1/messages

Upstream

reported Issue

Fixed in: not specified

A stream that ends cleanly without any finish reason is reported with finish_reason stop. CustomStreamWrapper.finish_reason_handler falls back to stop when no finish reason was received (https://github.com/BerriAI/litellm/blob/v1.105.1/litellm/litellm_core_utils/streaming_handler.py#L1715-L1727). The Responses path keeps the missing finish and passes.

History

Version	Grade
1.105.5	✗ WRONG
1.105.1	✗ WRONG