Tip: `thinking.display: "updates"` surfaces the progress lines a long agentic turn writes between tool calls

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Fable 5.1 writes short progress updates between tool calls, each arriving as its own thinking block immediately before the call, but under the default `thinking.display` of `omitted` those blocks come back empty and a long agentic turn looks silent to users. The new `display: "updates"` option (beta header `thinking-display-updates-2026-08-18`) returns the progress text while keeping reasoning hidden, so any thinking block with non-empty text is a status line you can render. Fable 5.1 writes fewer of these than Fable 5, especially at high effort, so ask explicitly for an opening line and periodic updates if your UI depends on narration.