✓ PASS

vercel-ai 7.0.153

truncation.reasoning-only · gemini

Requirements

Id	Level	Status	Evidence
cause-is-truncation	MUST	SATISFIED	finish.value="length" (primary: result.finishReason); truth.finish="length"; error.category=null; structured.returned_as_success=false
text-reported	MUST	SATISFIED	text.value="" (primary); truth.text=null
usage-reported	SHOULD	SATISFIED	usage.output=28 (primary); truth.usage.output=28

What the provider sent

Finish: length
Raw finish: MAX_TOKENS
Text: null
Tool calls: []
Usage: { "alternatives": {}, "cached_input": null, "input": 44, "output": 28, "raw": { "promptTokenCount": 44, "promptTokensDetails": [ { "modality": "TEXT", "tokenCount": 44 } ], "serviceTier": "standard", "thoughtsTokenCount": 28, "totalTokenCount": 72 }, "reasoning": 28, "total": 72 }
Stream completed: null
Error: null

Wire excerpt

status: 200
content-type: application/json; charset=UTF-8
body (json):
{
  "candidates": [
    {
      "content": {},
      "finishReason": "MAX_TOKENS",
      "index": 0
    }
  ],
  "usageMetadata": {
    "promptTokenCount": 44,
    "totalTokenCount": 72,
    "promptTokensDetails": [
      {
        "modality": "TEXT",
        "tokenCount": 44
      }
    ],
    "thoughtsTokenCount": 28,
    "serviceTier": "standard"
  },
  "modelVersion": "gemini-3.5-flash-lite",
  "responseId": "qAXOar_qAaeVmtkPp5_qyQQ"
}

What the library reported

Outcome

returned

Finish

{
  "raw": "MAX_TOKENS",
  "source": "result.finishReason",
  "surface": "primary",
  "value": "length"
}

Text

Value
Surface: primary

Tool calls

[]

Usage

{
  "cached_input": 0,
  "input": 44,
  "output": 28,
  "reasoning": 28,
  "surface": {
    "cached_input": "primary",
    "input": "primary",
    "output": "primary",
    "reasoning": "primary",
    "total": "primary"
  },
  "total": 72
}

Stream

{
  "chunks_seen": null,
  "completed": null,
  "used": false
}

Error

null

Unsupported reason

null

Full observation JSON

{
  "elapsed_ms": 94.134323,
  "error": null,
  "finish": {
    "raw": "MAX_TOKENS",
    "source": "result.finishReason",
    "surface": "primary",
    "value": "length"
  },
  "format": "wiretruth.observation/v1",
  "library": {
    "api": "generateText",
    "language": "javascript",
    "name": "vercel-ai",
    "version": "7.0.153"
  },
  "notes": [],
  "outcome": "returned",
  "stream": {
    "chunks_seen": null,
    "completed": null,
    "used": false
  },
  "structured": {
    "attempted": false,
    "returned_as_success": false,
    "value": null
  },
  "text": {
    "surface": "primary",
    "value": ""
  },
  "tool_calls": [],
  "unsupported_reason": null,
  "usage": {
    "cached_input": 0,
    "input": 44,
    "output": 28,
    "reasoning": 28,
    "surface": {
      "cached_input": "primary",
      "input": "primary",
      "output": "primary",
      "reasoning": "primary",
      "total": "primary"
    },
    "total": 72
  }
}

Fixture

recorded gemini/truncation.reasoning-only

Provenance	Value
Recorded at	2026-10-13T10:19:19Z
Requested model	gemini-3.5-flash-lite
Returned model	gemini-3.5-flash-lite
CI run	https://github.com/kartsan03/wiretruth/actions/runs/38382529221
Notes	Recorded on gemini-3.5-flash-lite at thinkingLevel HIGH with maxOutputTokens 32, because gemini-3.8-flash answered HTTP 503 (high demand) on three attempts. Thoughts used 28 of the 32 tokens and the candidate has content {} with finishReason MAX_TOKENS: the output limit bounds thoughts and answer together.

Reproduce

wiretruth serve gemini/truncation.reasoning-only

Plain-library snippet from the shim manifest.

createGoogleGenerativeAI({ baseURL: WIRETRUTH_BASE_URL_GEMINI + '/v1beta', apiKey })(model)

Upstream

No matching upstream report.

History

Version	Grade
7.0.153	✓ PASS
7.0.146	✓ PASS
7.0.142	✓ PASS