systemPrompt
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.
The non-interactive query path builds its context in one shared place, meant to behave identically.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.225.
In the changelogs
6Releases whose published page names systemPrompt.
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v2.1.260
hostPrompt field threaded through plugin/skill tool schema
A new hostPrompt field is now threaded through plugin/skill tool schema building.
found in this entry's text
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v2.1.259
New
proactivitycloud-session config fieldCloud sessions now treat a proactivity key as a supported passthrough option alongside systemPrompt and thinking.
found in this entry's text
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v2.1.248
Switching model over the SDK can also swap the system prompt
Over the SDK, set_model can also swap your custom system prompt from the next turn.
found in this entry's text
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v2.1.239
Two SDK fields drop their internal-only caveats
Two SDK fields dropped their internal-only caveats and now describe normal behaviour.
found in this entry's text
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v2.1.225
SDK query context construction was consolidated
The non-interactive query path builds its context in one shared place, meant to behave identically.
found in this entry's text
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v2.0.56
SDK Init Parameters for System Prompts and Agents
found in this entry's text
First cited
2The earliest release whose published evidence quoted systemPrompt was v2.1.248, 27 Aug 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
5One 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.