`systemBlocks`

setting never mined JSON

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.

Hooks calling $.model.complete can now pass promptBlocks and systemBlocks and mark blocks with cache: true for prompt caching

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.292.

First seen — never in a mined build

Last seen — never in a mined build

Builds0 / 138on this box, as of v2.1.295

Written about v2.1.292 first named in a changelog, 6 Oct 2026

In the changelogs

Releases whose published page names systemBlocks.

v2.1.292 6 Oct 2026
Hooks can use prompt caching when calling the model
Hooks calling $.model.complete can now pass promptBlocks and systemBlocks and mark blocks with cache: true for prompt caching

named in this entry, found in this entry's text

First cited

The earliest release whose published evidence quoted systemBlocks was v2.1.292, 6 Oct 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.

ReleaseDateThe span that was quoted

v2.1.2926 Oct 2026takes promptBlocks and systemBlocks that are lists of blocks, each { text } and at most `cache: true`

Presence across releases

The 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.