Antigravity-preview-09-2026 background interaction returns 404 immediately after successful creation

Gemini API
1

Background interactions created with antigravity-preview-09-2026 cannot be retrieved.

The initial POST succeeds with HTTP 200 and returns:

  • status: in_progress
  • a valid interaction ID
  • an environment_id
  • agent: antigravity-preview-09-2026

However, GET /v1beta/interactions/{interaction_id} returns:

HTTP 404
{
“error”: {
“message”: “Requested entity was not found.”,
“code”: “not_found”
}
}

The equivalent request works successfully with antigravity-preview-05-2026.

Synchronous execution with antigravity-preview-09-2026 also works. The failure is isolated to 09-2026 background execution/retrieval.

Reproduction request:

POST https://generativelanguage.googleapis.com/v1beta/interactions

{
“agent”: “antigravity-preview-09-2026”,
“background”: true,
“environment”: “remote”,
“agent_config”: {
“type”: “antigravity”
},
“input”: “Search the web and briefly identify the official website and physical offices of d3t Ltd. Cite sources.”
}

Wait 10 seconds, then:

GET https://generativelanguage.googleapis.com/v1beta/interactions/{interaction_id}

Result:
404 not_found

Controls tested:

  1. antigravity-preview-09-2026 with Api-Revision on POST and GET:
    Failed with 404.

  2. antigravity-preview-09-2026 with Api-Revision only on POST:
    Failed with 404.

  3. antigravity-preview-09-2026 without Api-Revision on either request:
    Failed with 404.

  4. Explicit store: true:
    Failed with 404.

  5. Implicit storage:
    Failed with 404.

  6. Underlying model explicitly set to gemini-3.7-flash:
    Failed with 404.

  7. Same background workflow using antigravity-preview-05-2026:
    Completed successfully.

  8. antigravity-preview-09-2026 in synchronous mode:
    Completed successfully.

Expected behavior:
GET should return an interaction with status in_progress, completed, or failed, as documented.

Actual behavior:
The newly created interaction becomes unavailable and GET returns 404.

Environment:

  • Gemini Developer API
  • REST Interactions API v1beta
  • Remote environment
  • n8n HTTP Request node
  • Reproduced consistently on September 18, 2026
  • API key tier: standard/free-tier key