gpt-oss (harmony) ships BUILT-IN tools named python/browser, invoked
with the raw body as the argument (to=python + bare source), while
custom functions use to=functions.NAME + JSON. Exposing our own tools
under those names makes the model answer with the built-in convention:
it emits raw code, the server parses it as JSON, and the request dies
with 'error parsing tool call: raw=import sys, ...'. In streaming mode
Ollama does not report it at all — it truncates the stream, so the turn
arrives as an empty response and the agent loop reads it as a model
stall. bash collides the same way in practice.
Measured on gpt-oss:20b via Ollama /v1, fixed agentic prompt, 12 runs
per arm: python+bash as-is 2/12, python renamed 10/12, both renamed
12/12. 74 HTTP 500s were logged server-side during investigation with
zero surfaced to the client.
Rename the colliding tools on the outbound payload and map the names
back on responses. Transport-only and gated on gpt-oss: every other
model's schemas pass through untouched (asserted in tests).
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>
