Adds tools, thinking blocks, code execution, and web search support to the safetensors / transformers and MLX inference backends in Studio, bringing them to parity with the GGUF path.
What ships
- safetensors / transformers agentic tool loop with cumulative-text state machine, tool-call XML parser, and template kwarg forwarding (tools / enable_thinking / reasoning_effort / preserve_thinking).
- MLX backend: same kwargs accepted on Apple Silicon; chat_template_info shipped through worker IPC; pills enable for Qwen / Qwen3 / Qwen3.5 / Gemma reasoning.
- Capability classifier (_detect_safetensors_features) gates supports_tools on actual parser-compatible emission markers (<tool_call> / <function=) so Llama-3 / Mistral / Gemma 4 do not advertise toggles the parser cannot honour.
- gpt-oss override stays: reasoning on, tools off (Harmony channel, not <tool_call> XML).
- CWE-209 hygiene: safetensors SSE error path emits a constant message and logs the trace server-side.
Validation
- 256 unit tests green (43 tool-loop, 11 capability advertise, 7 MLX backend, 5 main-added, 190 adjacent inference / anthropic / openai regression).
- Cross-OS staging CI green on ubuntu-latest / macos-14 / windows-latest plus a dedicated MLX cartesian probe against real unsloth/Qwen3.5-0.8B on macos-14 (CI 26098107440).
- Capability parity verified across Qwen3 / Qwen3.5 / Llama-3 / Mistral / Gemma / DeepSeek-R1 / gpt-oss (incl. BF16).
- Manual confirmation from Imagineer99 on Qwen3.5-2B: think + search + code exec working.
Closes the safetensors / MLX gap with the GGUF backend.
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