v0.37.8

Two harness and model pairs are no longer offered

On the hosted service, two agent harness and model pairs failed in deck conversations that switched models partway:

• fast-agent with Gemini 4 Argon, on Google's own API, after another model's turn left an image in the conversation. Argon made one tool call and then gave an empty answer, or said what it would do and made no tool call.
• Docker Agent with Grok 4.20, asked to restyle a deck another model had made. It said the deck was restyled and made no tool call.

Both pairs are no longer offered, here and on the hosted service. fast-agent keeps the rest of the Gemini family, and Docker Agent keeps the other Grok models. The support matrix and its notes are updated to match.

A Gemini thought signature is also known by the signature itself

HarnessRouter tracks which model made each Gemini tool call's signature, so that a later Gemini model gets Google's placeholder instead of another model's signature. It tracked this by the call's id only. A harness that replayed a call under an id of its own, while keeping Google's signature on it, would have slipped past the check. HarnessRouter now also recognises the signature itself, and keeps only a digest of it. None of the agent harnesses we tested replays calls this way today. This guards against one that does.

Full Changelog: v0.37.7...v0.37.8