✓ PASS

pydantic-ai 2.61.0

truncation.text-stream · anthropic

Requirements

Id	Level	Status	Evidence
cause-is-truncation	MUST	SATISFIED	finish.value="length" (primary: ModelResponse.finish_reason); truth.finish="length"; error.category=null; structured.returned_as_success=false
text-reported	SHOULD	SATISFIED	text.value="Octopuses change colour by" (primary); truth.text="Octopuses change colour by"
usage-reported	SHOULD	SATISFIED	usage.output=16 (primary); truth.usage.output=16

What the provider sent

Finish: length
Raw finish: max_tokens
Text: Octopuses change colour by
Tool calls: []
Usage: { "alternatives": {}, "cached_input": null, "input": 25, "output": 16, "raw": { "input_tokens": 25, "output_tokens": 16, "output_tokens_details": { "thinking_tokens": 8 } }, "reasoning": 8, "total": 41 }
Stream completed: true
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}


event: message_delta
data: {"type":"message_delta","delta":{"stop_reason":"max_tokens","stop_sequence":null},"usage":{"output_tokens":16,"output_tokens_details":{"thinking_tokens":8}}}


event: message_stop
data: {"type": "message_stop"}

What the library reported

Outcome

returned

Finish

{
  "raw": "max_tokens",
  "source": "ModelResponse.finish_reason",
  "surface": "primary",
  "value": "length"
}

Text

Value: Octopuses change colour by
Surface: primary

Tool calls

[]

Usage

{
  "cached_input": 0,
  "input": 25,
  "output": 16,
  "reasoning": 8,
  "surface": {
    "cached_input": "primary",
    "input": "primary",
    "output": "primary",
    "reasoning": "primary",
    "total": "primary"
  },
  "total": 41
}

Stream

{
  "chunks_seen": 9,
  "completed": true,
  "used": true
}

Error

null

Unsupported reason

null

Full observation JSON

{
  "elapsed_ms": 236.96659784764051,
  "error": null,
  "finish": {
    "raw": "max_tokens",
    "source": "ModelResponse.finish_reason",
    "surface": "primary",
    "value": "length"
  },
  "format": "wiretruth.observation/v1",
  "library": {
    "api": "Agent.run_stream_events",
    "language": "python",
    "name": "pydantic-ai",
    "version": "2.61.0"
  },
  "notes": [],
  "outcome": "returned",
  "stream": {
    "chunks_seen": 9,
    "completed": true,
    "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": 0,
    "input": 25,
    "output": 16,
    "reasoning": 8,
    "surface": {
      "cached_input": "primary",
      "input": "primary",
      "output": "primary",
      "reasoning": "primary",
      "total": "primary"
    },
    "total": 41
  }
}

Fixture

documented anthropic/truncation.text-stream

Provenance	Value
Source	https://platform.claude.com/docs/en/build-with-claude/streaming#streaming-request-with-thinking
Notes	Documented shapes, not a recording. Message envelope and stop fields follow handling-stop-reasons; content blocks follow thinking/streaming and handle-tool-calls. Model changed to claude-sonnet-5-5; IDs and scenario text are filled in. Token counts are illustrative, filled in to include thinking within the requested output limit, not measured. ASSUMED composition: omitted thinking followed by a short text prefix at max_tokens; the docs do not show this exact small-budget response. Thinking is empty and the signature placeholder is copied literally from streaming#thinking-delta. SSE names, JSON shapes, field order and spaced text/thinking events follow streaming examples; the compact message_delta follows Streaming request with tool use. Fragment boundaries and counts are filled in. Signature placeholder is copied literally from the signature_delta example; empty thinking_delta follows the documented omitted display flow. The output_tokens_details.thinking_tokens breakdown follows thinking-steering.md (https://platform.claude.com/docs/en/build-with-claude/thinking-steering-and-cost#pricing); the thinking count of 8 is filled in, not measured. It appears only in the final message_delta usage.

Provenance

Value

Source

https://platform.claude.com/docs/en/build-with-claude/streaming#streaming-request-with-thinking

Notes

Documented shapes, not a recording. Message envelope and stop fields follow handling-stop-reasons; content blocks follow thinking/streaming and handle-tool-calls. Model changed to claude-sonnet-5-5; IDs and scenario text are filled in. Token counts are illustrative, filled in to include thinking within the requested output limit, not measured. ASSUMED composition: omitted thinking followed by a short text prefix at max_tokens; the docs do not show this exact small-budget response. Thinking is empty and the signature placeholder is copied literally from streaming#thinking-delta. SSE names, JSON shapes, field order and spaced text/thinking events follow streaming examples; the compact message_delta follows Streaming request with tool use. Fragment boundaries and counts are filled in. Signature placeholder is copied literally from the signature_delta example; empty thinking_delta follows the documented omitted display flow. The output_tokens_details.thinking_tokens breakdown follows thinking-steering.md (https://platform.claude.com/docs/en/build-with-claude/thinking-steering-and-cost#pricing); the thinking count of 8 is filled in, not measured. It appears only in the final message_delta usage.

Reproduce

wiretruth serve anthropic/truncation.text-stream

Plain-library snippet from the shim manifest.

AnthropicModel(model, provider=AnthropicProvider(base_url=WIRETRUTH_BASE_URL_ANTHROPIC, api_key=WIRETRUTH_API_KEY)); host root

Upstream

No matching upstream report.

History

Version	Grade
2.61.0	✓ PASS
2.56.0	✓ PASS