harnessHead
A Claude Code settings key, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Background task output can carry an extra block of harness text ahead of the task's own output.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.246.
In the changelogs
3Releases whose published page names harnessHead.
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v2.1.269
New safety wrapper for artifact content surfaced via background task output
Background task output now gets a warning wrapper when it may contain untrusted artifact content
found in this entry's text
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v2.1.269
Remote-agent transcript views can now show a 'harnessHead' excerpt
Remote-agent transcript output can include a harnessHead excerpt built by a new helper
found in this entry's text
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v2.1.246
Background task output can start with a harness preamble
Background task output can carry an extra block of harness text ahead of the task's own output.
found in this entry's text
First cited
1The earliest release whose published evidence quoted harnessHead was v2.1.269, 11 Sep 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
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
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.