thinkingConfig
A Claude Code settings key, read out of the shipped bundle. It was in the build from v2.1.315 and was gone by v2.1.317.
Internal helper requests no longer fail from asking for high effort with thinking off.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.221.
In the changelogs
6Releases whose published page names thinkingConfig.
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v2.1.273
Headless/SDK session init now threads a handoff relay marker
Headless and SDK session setup now carries an internal handoff relay marker
found in this entry's text
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v2.1.269
Session/tool-use context object grows a large set of new accessors
The internal per-session context object gained many new fields covering effort, hooks, tools, and skills
found in this entry's text
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v2.1.238
More internal model calls marked as machine-driven
Behind-the-scenes classifier calls for artifact reactions are now tagged as machine calls, not your turns.
found in this entry's text
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v2.1.221
Output effort clamped when thinking is mechanically disabled
Internal helper requests no longer fail from asking for high effort with thinking off.
found in this entry's text
- v2.1.218
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v2.1.165
Extended Thinking Support in Conversation Summarizer
found in this entry's text
First cited
2The earliest release whose published evidence quoted thinkingConfig was v2.1.165, 5 Jun 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
2Build by build
7One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the settings key does. All settings keys.