The server-sent model mix recipe can be awaited at startup and reused from cache

What

Anthropic's server can send a model mix recipe. The recipe names a lead model for the main conversation and a worker model for subagents, which are helpers Claude starts to work on part of a task. Two changes affect how that recipe is obtained.

• A new step can make Claude Code wait for a served recipe before sending its first request. It runs only when the lead and worker models match and neither CLAUDE_CODE_SUBAGENT_MODEL nor CLAUDE_CODE_SUBAGENT_MODEL_FORCE is set. It is controlled by the remote switch tengu_zesty_horizon_wait, which defaults to on.
• When the downloaded client data has no tengu_zesty_horizon entry, Claude Code can now fall back to a cached recipe it was served before (servedMixRecipe). Before, it simply had no recipe.
• The fallback is used only when the account epoch matches and the run is neither non-interactive nor an SDK run. The cached recipe's lead model must also equal the model it was served for.
• Each recipe is tagged with its source, either "served" or "document".

Nothing has been read about the tengu_zesty_horizon_wait or tengu_zesty_horizon switches.

Why

The model mix no longer disappears when the downloaded data happens to leave it out. Startup may pause briefly while the recipe is fetched, but only when you have not chosen subagent models yourself.