The API for Claude models offers the beta value "updates" for progress updates between tool calls
Anthropic has added the beta value "updates" to the thinking.display parameter. It enables the models Claude Fable 5.1, Claude Mythos 5.1 and Claude Fable 5 to return short progress updates between tool calls, while the thinking field remains empty.
According to the release notes for the Claude platform, Anthropic has added a third value, called "updates", to the thinking.display parameter. It is currently in beta (designated thinking-display-updates-2026-08-18). The parameter previously offered other options for displaying the model's internal reasoning; the new value adds another way to work with this field.
When set to "updates", the thinking field in the response remains empty, just as it does when set to "omitted". The difference is that the models Claude Fable 5.1, Claude Mythos 5.1 and Claude Fable 5 return short updates on their progress between individual tool calls, as text, with at most one such block before each tool call.
The source does not provide further details, such as exact technical parameters or a timeline for ending the beta phase.
Why it matters
Developers of agent applications built on the API for Claude models can show users what the model is currently doing between steps involving tools without having to disclose the full content of its internal reasoning (thinking). This is particularly useful for multilevel agent tasks, where users previously saw no progress information when "omitted" was set.
Two audiences, two different impacts
What this means
For individuals
Developers working with the API for Claude models and tool calls can set thinking.display to "updates" to receive short progress updates between individual calls, instead of the previously empty thinking field.
For a business
Companies building agent products on the API for Claude models can show users progress updates between tool calls without revealing the full content of the model's internal reasoning.
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