maskDuplicates
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.
You can mask secrets in credential files so sandboxed commands see placeholders while real values are swapped in on egress.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.221.
In the changelogs
3Releases whose published page names maskDuplicates.
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v2.1.268
Sandbox-runtime credential masking gains JWT decoding, claim-level masking, and duplicate-value scrubbing
Sandbox credential masking adds JWT decoding, per-claim masking, and scrubbing of duplicate secret values
found in this entry's text
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v2.1.221
sandbox.credentials.files gains a
maskmode with regex extractionYou can mask secrets in credential files so sandboxed commands see placeholders while real values are swapped in on egress.
named in this entry, found in this entry's text
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v2.1.199
Credential Masking: Regex Extract Patterns
found in this entry's text
First cited
1The earliest release whose published evidence quoted maskDuplicates was v2.1.199, 2 Jul 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.