What
If the API refuses a compaction request and offers a fallback model, compaction now aborts the refused stream and retries on an allowed fallback instead of failing. When your model policy leaves no usable fallback, compaction stops with a message naming the model and pointing at /model.
Details
- When the API supplies one, a usage-credit code is minted for the fallback model.
- The retry is recorded as
tengu_refusal_fallback_triggeredwith a query source of "compact". - Example failure text: "Compaction unavailable: your model policy only allows Fable 5, which requires usage credits · /model to set it up".
Evidence
Compaction unavailable: your model policy only allows Fable 5, which requires usage credits \xB7 /model to set it up
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundle/model
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up /model, on All settings.
Cap the [effort level](/docs/en/model-config#adjust-effort-level) a session can use, leaving lower levels available. Any higher level runs at the cap instead, including one from `/effort`, the `/model` picker, `--effort`, [`CLAUDE_CODE_EFF…settings-reference see the edit
Added since
A small documentation edit on Agent SDK reference - TypeScript touched a line naming /model after this was published.
`effortLevel` accepts an [effort level](/docs/en/model-config#adjust-effort-level) name. It also accepts `"ultracode"`, which requests `xhigh` effort with [ultracode](/docs/en/workflows#let-claude-decide-with-ultracode) on. `applyFlagSetti…agent-sdk/typescript see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
A small documentation edit on Agent SDK reference - TypeScript touched a line naming /model after this was published.