[Feedback]: Every prompt results in `Error during ACP method session/prompt`

Start by reviewing the attached logs.zip and the ACP session/prompt request handling around the 1.0.15 update. Reproduce a prompt with the reported Poolside agent and vllm endpoint, then trace the malformed tool-call payload shown in the validation error. Done means prompts complete without the ACP method error and the request matches the endpoint's expected schema.

logs.zip

Feedback

Every prompt results in this error:

• Error during ACP method session/prompt
  ⎿ 400 Bad Request: 3 validation errors:
      {'type': 'missing', 'loc': ('body', 1, 'ChatCompletionMessageFunctionToolCallParam', 'function'), 'msg': 'Field required', 'input': {'id': '019fdcf3-e6aa-76e5-9b65-059d74ffa3c6',
    'type': 'function'}}
      {'type': 'missing', 'loc': ('body', 1, 'ChatCompletionMessageCustomToolCallParam', 'custom'), 'msg': 'Field required', 'input': {'id': '019fdcf3-e6aa-76e5-9b65-059d74ffa3c6',
    'type': 'function'}}
      {'type': 'literal_error', 'loc': ('body', 1, 'ChatCompletionMessageCustomToolCallParam', 'type'), 'msg': "Input should be 'custom'", 'input': 'function', 'ctx': {'expected':
    "'custom'"}}

      File "/atlas/.venv/lib/python3.12/site-packages/vllm/entrypoints/serve/utils/api_utils.py", line 40, in create_chat_completion
        POST /v1/chat/completions [{'type': 'missing', 'loc': ('body', 1, 'ChatCompletionMessageFunctionToolCallParam', 'function'), 'msg': 'Field required', 'input': {'id': '019fdcf3-
    e6aa-76e5-9b65-059d74ffa3c6', 'type': 'function'}}, {'type': 'missing', 'loc': ('body', 1, 'ChatCompletionMessageCustomToolCallParam', 'custom'), 'msg': 'Field required', 'input':
    {'id': '019fdcf3-e6aa-76e5-9b65-059d74ffa3c6', 'type': 'function'}}, {'type': 'literal_error', 'loc': ('body', 1, 'ChatCompletionMessageCustomToolCallParam', 'type'), 'msg': "Input
    should be 'custom'", 'input': 'function',

This started after updating to 1.0.15.

Session

• Pool version: 1.0.15
• OS/arch: darwin/arm64
• Session ID: 019fdcf3-b172-775a-bc42-793434e9d088
• Agent server: Poolside
• Agent command: /Users/dejanmircevski/.local/bin/pool
• Model: riemann1_turbo4
• Timestamp: 2026-08-07T18:05:07+02:00

Logs

Attach this zip before submitting:

/var/folders/17/pmk0k7k16b36zqcfvdwvtlhr0000gn/T/pool-logs/20260807-180507-019fdcf3-b172-775a-bc42-793434e9d088/logs.zip

Logs and trajectory contain full prompt and response text from the session. Review before submitting.