Post Session Thread Item

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POST /revisions/:id/data/command (Command: post_session_thread_item)

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Request Body

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Response

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Errors

• invalid_thread_envelope — the alias does not exist or its value.type is not "thread".
• thread_item_too_large — the serialized item exceeds the server-side size cap.
• invalid_request_body — a content block has an unknown type, or a file block omits one of alias, name, content_type, or size; both are rejected by request-schema validation before the command runs.
• invalid_thread_item_content — a file block carries no file object at all, or its alias is outside the session-object alias grammar.
• too_many_files — the item contains more than 10 file content blocks.
• file_not_found — a file block references an alias that does not exist as a file object in the session.

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Example

{
  "command": "post_session_thread_item",
  "session_id": "sess_001",
  "alias": "onboarding_thread",
  "content": [
    { "type": "text", "text": "Hello, world." }
  ]
}

{
  "status": "success",
  "item": {
    "id": "itm_01H...",
    "session_id": "sess_001",
    "revision_id": "rev_001",
    "alias": "onboarding_thread",
    "created_at": "2026-05-22T22:00:00.000000Z",
    "user_id": "usr_001",
    "content": [
      { "type": "text", "text": "Hello, world." }
    ]
  }
}

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See also

• BlobHub Worker — thread items — how the worker structures content and metadata for agent emissions, and the 60 KiB truncation behavior.
• File session object — the object a file block’s alias must reference.
• Upload Session File — the only way to create a file object and obtain a valid alias for it.