additionalContext
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.
Prompt-expansion hooks can keep your original prompt text out of the block message.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.238.
In the changelogs
9Releases whose published page names additionalContext.
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v2.1.299
Hooks can return display details for a permission prompt
Hooks can now return
permissionDisplayin their output, next toadditionalContext, to supply details for a permission promptfound in this entry's text, named in this entry
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v2.1.292
Hook messages and added context are processed before reaching the model
Text from a hook's systemMessage and additionalContext now goes through an extra processing step before the model sees it
found in this entry's text
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v2.1.275
Large hook additionalContext entries can now be persisted to disk instead of truncated inline
Oversized hook context is now saved to a file instead of being cut off
found in this entry's text, named in this entry
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v2.1.251
New PreModelSwitch and PostModelSwitch hooks
New PreModelSwitch and PostModelSwitch hooks let you gate or annotate every model change.
named in this entry, found in this entry's text
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v2.1.238
Prompt-expansion hooks can hide the original prompt from a block message
Prompt-expansion hooks can keep your original prompt text out of the block message.
found in this entry's text
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v2.1.199
Hook additionalContext: Structured JSON Output
found in this entry's text
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v2.1.163
SubagentStop Hook Event
found in this entry's text
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v2.1.163
Stop Hook Output Schema with additionalContext
found in this entry's text
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v2.1.118
PostToolBatch Hook Event
found in this entry's text
First cited
3The earliest release whose published evidence quoted additionalContext was v2.1.163, 4 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
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.