Cloud API streaming drops nearai_fusion metadata from Fusion SSE events

Summary

Prod Cloud API forwards Fusion non-streaming responses correctly, including nearai_fusion metadata, but streaming Fusion responses lose the nearai_fusion metadata event. The stream still returns content, [DONE], and aggregate usage, so the issue appears limited to forwarding/preserving the extra top-level Fusion metadata in SSE events.

Direct proxy streaming includes nearai_fusion; prod Cloud API streaming currently does not.

Environment

• Cloud API: https://cloud-api.near.ai
• Direct GLM proxy: https://glm-5-2.completions.near.ai
• Outer/synthesis model: z-ai/glm-5.2
• Judge model: z-ai/glm-5.2
• Panel model: deepseek-ai/DeepSeek-V4-Flash
• Fusion tool type: nearai:fusion
• Web tool: web_context_search

No real API token is included in this issue. Use a disposable test token in $TOKEN.

Expected

For streaming Fusion responses through Cloud API, the terminal Fusion metadata event should preserve the proxy's nearai_fusion object, matching the direct proxy streaming behavior and the existing infra test expectation.

Expected terminal metadata shape includes:

{
  "usage": {
    "prompt_tokens": 4805,
    "completion_tokens": 355,
    "total_tokens": 5160
  },
  "nearai_fusion": {
    "status": "invoked",
    "panel": [{"status": "ok", "web_tool_calls": 1}],
    "judge": {"status": "ok"},
    "aggregate_usage": {
      "prompt_tokens": 4805,
      "completion_tokens": 355,
      "total_tokens": 5160
    }
  }
}

Actual

Through prod Cloud API streaming:

• HTTP 200
• SSE stream completes with [DONE]
• Final content is correct
• Aggregate usage is present
• nearai_fusion is missing from all stream events

Observed parsed summary:

{
  "chunks": 4,
  "done": true,
  "content": "near.org",
  "usage": {
    "prompt_tokens": 4805,
    "completion_tokens": 355,
    "total_tokens": 5160
  },
  "fusion_status": null,
  "panel_statuses": null,
  "panel_web_tool_calls": null,
  "judge_status": null,
  "aggregate_usage": null,
  "errors": []
}

Raw tail of a Cloud API stream for a simpler Fusion request shows only the usage event before [DONE]:

data: {"id":"99c85d7ba95c47b79149e84bcf2b7d49","object":"chat.completion.chunk","created":1781804308,"model":"z-ai/glm-5.2","choices":[{"index":0,"delta":{"role":"assistant"}}],"usage":null}

data: {"id":"99c85d7ba95c47b79149e84bcf2b7d49","object":"chat.completion.chunk","created":1781804308,"model":"z-ai/glm-5.2","choices":[{"index":0,"delta":{"content":"stream-inspect-ok"}}],"usage":null}

data: {"id":"99c85d7ba95c47b79149e84bcf2b7d49","object":"chat.completion.chunk","created":1781804308,"model":"z-ai/glm-5.2","choices":[{"index":0,"delta":{},"finish_reason":"stop"}],"usage":null}

data: {"id":"99c85d7ba95c47b79149e84bcf2b7d49","object":"chat.completion.chunk","created":1781804308,"model":"z-ai/glm-5.2","choices":[],"usage":{"prompt_tokens":362,"completion_tokens":409,"total_tokens":771}}

data: [DONE]

Non-Streaming Control Passes

The same setup through prod Cloud API in non-streaming mode returns full Fusion metadata.

Repro:

curl --max-time 120 -sS \
  https://cloud-api.near.ai/v1/chat/completions \
  -H "Authorization: Bearer $TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{
    "model":"z-ai/glm-5.2",
    "messages":[{
      "role":"user",
      "content":"Use web_context_search if available, then answer with exactly the official NEAR Protocol website domain and no extra words."
    }],
    "tools":[
      {
        "type":"nearai:fusion",
        "analysis_models":["deepseek-ai/DeepSeek-V4-Flash"],
        "model":"z-ai/glm-5.2",
        "max_tool_calls":1,
        "max_completion_tokens":768,
        "temperature":0
      },
      {"type":"web_context_search"}
    ],
    "tool_choice":"required",
    "max_completion_tokens":768,
    "temperature":0,
    "stream":false
  }' | jq '{content: .choices[0].message.content, fusion_status: .nearai_fusion.status, panel: .nearai_fusion.panel, judge: .nearai_fusion.judge, usage, aggregate_usage: .nearai_fusion.aggregate_usage}'

Observed summary:

{
  "content": "near.org",
  "fusion_status": "invoked",
  "panel": [{
    "domain": "dsv4-flash.completions.near.ai",
    "model": "deepseek-ai/DeepSeek-V4-Flash",
    "status": "ok",
    "web_tool_calls": 1,
    "verifiable": true
  }],
  "judge": {
    "domain": "glm-5-2.completions.near.ai",
    "model": "z-ai/glm-5.2",
    "status": "ok",
    "verifiable": true
  },
  "usage": {
    "completion_tokens": 362,
    "prompt_tokens": 4799,
    "total_tokens": 5161
  },
  "aggregate_usage": {
    "completion_tokens": 362,
    "prompt_tokens": 4799,
    "total_tokens": 5161
  }
}

Streaming Repro Through Cloud API

curl --max-time 120 -sS -N \
  https://cloud-api.near.ai/v1/chat/completions \
  -H "Authorization: Bearer $TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{
    "model":"z-ai/glm-5.2",
    "messages":[{
      "role":"user",
      "content":"Use web_context_search if available, then answer with exactly the official NEAR Protocol website domain and no extra words."
    }],
    "tools":[
      {
        "type":"nearai:fusion",
        "analysis_models":["deepseek-ai/DeepSeek-V4-Flash"],
        "model":"z-ai/glm-5.2",
        "max_tool_calls":1,
        "max_completion_tokens":768,
        "temperature":0
      },
      {"type":"web_context_search"}
    ],
    "tool_choice":"required",
    "max_completion_tokens":768,
    "temperature":0,
    "stream":true,
    "stream_options":{"include_usage":true}
  }'

Parse the SSE events and check whether any event has a top-level nearai_fusion key. Current prod result: none do.

Existing Test Expectation

infra-tests/tests/test_fusion.py already expects streaming Fusion metadata through Cloud API:

fusion_event = next((event for event in events if event.get("nearai_fusion")), None)
assert fusion_event is not None, f"missing streaming Fusion metadata event: {events[-3:]}"
assert fusion_event.get("usage"), f"Fusion metadata event missing usage: {fusion_event}"
_assert_fusion_metadata(fusion_event)

This production behavior would fail that assertion.

Notes / Likely Area

Inference-proxy direct streaming emits Fusion metadata, and Cloud API non-streaming preserves it. The likely issue is in Cloud API's streaming passthrough/reassembly path: it preserves standard SSE fields and aggregate usage, but drops unknown top-level fields such as nearai_fusion from the terminal event.

Cloud API should remain a passthrough for Fusion semantics; it does not need to understand Fusion, but it should preserve unknown top-level JSON fields in streamed SSE events.

Start with infra-tests/tests/test_fusion.py and run the existing streaming Fusion test to reproduce the missing metadata event. Then trace the Cloud API streaming passthrough or reassembly path described in the issue. Done means streamed events preserve the proxy's top-level nearai_fusion object and the existing metadata assertions pass.