DiffusionGemma serves via the visual runner, which streams per-step
canvas frames so the answer resolves live in the bubble. The agentic
tool loop (generate_chat_completion_with_tools) does not forward those
frames, so whenever a tool pill (Search/Code) was on the live canvas
silently vanished while text still streamed. DiffusionGemma is not a
tool-calling target anyway, so report supports_tools=False for it: the
chat always takes the frame-forwarding path, and the Search/Code pills
disable themselves (a local model has no builtin web search either).
Also turn the artifacts canvas on by default for DiffusionGemma so a
full-HTML answer (e.g. a playable game) renders as an interactive
sandboxed card without the user flipping the global artifacts toggle.
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