tengu_prompt_cache_break
A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Cache diagnostics know when the baseline came from disk and skip misleading difference reports.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.232.
In the changelogs
4Releases whose published page names tengu_prompt_cache_break.
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v2.1.275
System-prompt "folded attachment" shape now tracked for cache-break diagnosis
Cache-break diagnostics now track the system prompt's folded attachment shape too
found in this entry's text, named in this entry
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v2.1.261
New prompt-cache-break diagnostics: msg0 shape tracking
New internal diagnostics track the first message's shape to diagnose cache breaks.
gate cited by this entry
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v2.1.232
Cache-break diagnostics note when the baseline was loaded from disk
Cache diagnostics know when the baseline came from disk and skip misleading difference reports.
gate cited by this entry, found in this entry's text
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v2.1.105
Prompt Cache Break Detection [In Development]
gate cited by this entry, found in this entry's text
Gate readings
0No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.
First cited
1The earliest release whose published evidence quoted tengu_prompt_cache_break was v2.1.105, 13 Apr 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 feature flag does. All feature flags.