– UNSUPPORTED

tanstack-ai 1.4.0

truncation.structured-output · gemini

Requirements

Id	Level	Status	Evidence

Notes

On these models chat({ outputSchema }) requests a streamed response, even without tools, so it never sends the non-streamed request this fixture replays. (https://tanstack.com/ai/latest/docs/api/ai#usage-examples)

What the provider sent

Finish: length
Raw finish: MAX_TOKENS
Text: { "islands":
Tool calls: []
Usage: { "alternatives": {}, "cached_input": null, "input": 19, "output": 7, "raw": { "candidatesTokenCount": 7, "promptTokenCount": 19, "promptTokensDetails": [ { "modality": "TEXT", "tokenCount": 19 } ], "serviceTier": "standard", "totalTokenCount": 26 }, "reasoning": null, "total": 26 }
Stream completed: null
Error: null

Wire excerpt

status: 200
content-type: application/json; charset=UTF-8
body (json):
{
  "candidates": [
    {
      "content": {
        "parts": [
          {
            "text": "{\n  \"islands\":",
            "thoughtSignature": "EmAKXgFpFH0TRpy3JZL2qd/cDtQmrps9PxfnU8+ovCZz1iEJU700MutHK0ZD2fh0jH2jIqIzPwG+U7gpx2LlBGanxSVs64JLIvaxP9PYvF/lXUxs9Yud2C1/hs4Hi8FAvMg="
          }
        ],
        "role": "model"
      },
      "finishReason": "MAX_TOKENS",
      "index": 0
    }
  ],
  "usageMetadata": {
    "promptTokenCount": 19,
    "candidatesTokenCount": 7,
    "totalTokenCount": 26,
    "promptTokensDetails": [
      {
        "modality": "TEXT",
        "tokenCount": 19
      }
    ],
    "serviceTier": "standard"
  },
  "modelVersion": "gemini-3.5-flash-lite",
  "responseId": "lwTOap6OEvjljMcPvYSCgAU"
}

What the library reported

Outcome

unsupported

Finish

{
  "raw": null,
  "source": null,
  "surface": "absent",
  "value": null
}

Text

Value: null
Surface: absent

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

Error

null

Unsupported reason

On these models chat({ outputSchema }) requests a streamed response, even without tools, so it never sends the non-streamed request this fixture replays. https://tanstack.com/ai/latest/docs/api/ai#usage-examples

Full observation JSON

{
  "elapsed_ms": 1.2721239999999625,
  "error": null,
  "finish": {
    "raw": null,
    "source": null,
    "surface": "absent",
    "value": null
  },
  "format": "wiretruth.observation/v1",
  "library": {
    "api": "chat",
    "language": "javascript",
    "name": "tanstack-ai",
    "version": "1.4.0"
  },
  "notes": [],
  "outcome": "unsupported",
  "stream": {
    "chunks_seen": null,
    "completed": null,
    "used": false
  },
  "structured": {
    "attempted": false,
    "returned_as_success": false,
    "value": null
  },
  "text": {
    "surface": "absent",
    "value": null
  },
  "tool_calls": [],
  "unsupported_reason": "On these models chat({ outputSchema }) requests a streamed response, even without tools, so it never sends the non-streamed request this fixture replays. https://tanstack.com/ai/latest/docs/api/ai#usage-examples",
  "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

recorded gemini/truncation.structured-output

Provenance	Value
Recorded at	2026-10-13T10:14:47Z
Requested model	gemini-3.5-flash-lite
Returned model	gemini-3.5-flash-lite
CI run	https://github.com/kartsan03/wiretruth/actions/runs/38381941285

Reproduce

wiretruth serve gemini/truncation.structured-output

Plain-library snippet from the shim manifest.

createGeminiChat(model, apiKey, { baseURL: WIRETRUTH_BASE_URL_GEMINI }); SDK appends /v1beta/models/<model>:streamGenerateContent or :generateContent.

Upstream

No matching upstream report.

History

Version	Grade
1.4.0	– UNSUPPORTED
1.0.0	– UNSUPPORTED
0.71.0	– UNSUPPORTED