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Streaming lets your UI render tokens as they are generated instead of waiting for a full response.

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Supported endpoints

  • POST /v1/responses
  • POST /v1/chat/completions
  • POST /v1/messages

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Enable streaming

Set stream: true in the request body. 
curl https://api.phaseo.app/v1/responses \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-5-nano",
    "input": "Write a short greeting.",
    "stream": true
  }'

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SSE frame shape

Streams are returned as SSE frames: 
data: {"id":"resp_...","status":"in_progress",...}
data: {"type":"response.output_text.delta","delta":"Hello"}
data: {"type":"response.completed",...}
data: [DONE]

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Error handling during streams

  • If a request fails before streaming starts, you receive a normal JSON error response.
  • If a request fails after partial output, treat the stream as incomplete and surface a retry path in your UI.
  • Always log generation_id (when present) for support and correlation.

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Cancellation

Use cancellation controls (AbortController in JS, request timeout in backend workers) so abandoned streams do not consume unnecessary capacity.

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Known limitation

At the current gateway request-validation layer, stream: true with tool-calling is rejected. Use non-streaming for tool-calling loops.
Last modified on April 21, 2026