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GPT-OSS

GPT-OSS is one of the first non-Gemma families treated as a first-class capability-system consumer.

Why GPT-OSS Is Special​

GPT-OSS needs more than coarse thinking metadata.

The runtime needs to know:

  • that tool calling is expected
  • that GPT-OSS output uses a family-specific tool-call parsing flow
  • that the tokenizer and runtime should agree on the GPT-OSS tool format

Current Capability Declarations​

The built-in GPT-OSS cards now declare:

  • reasoning support with a default effort of medium
  • non-toggleable reasoning semantics
  • tool-calling support
  • GPT-OSS tool-call format
  • GPT-OSS output parser selection
  • builtin browser tools:
    • web_search
    • open_url
    • extract_page

That moves GPT-OSS support out of “only infer it from the model id” territory and into the same declarative-plus-resolved model that Gemma 4 uses.

Current Gaps​

Current GPT-OSS support is intentionally narrow:

  • Harmony parsing stays GPT-OSS-specific
  • reasoning effort is explicit, but a true “thinking off” mode is not promised
  • browsing is static fetch + extraction, not browser automation
  • the dashboard executes GPT-OSS browser tool calls and feeds the result back into the conversation loop

Why This Matters​

GPT-OSS is the proof that the capability system is not just a Gemma 4 special case. It shows that model-card-backed runtime behavior can cleanly cover a second specialized family with different parser, reasoning, and tool semantics without changing generic-model behavior.

On both engines​

GPT-OSS harmony parsing works on the MLX engine (token level) and on the llama.cpp engine (string level). llama.cpp hands back already-detokenized text, so the runner reparses the harmony channel markers from strings into a separate reasoning channel, with a dependency-free parser that runs on non-Mac GPU nodes. The same approach covers plain <think>-delimited reasoning models, so a reasoning model's chain-of-thought lands in reasoning_content and the answer stays clean regardless of which engine serves it.