Claude Code v2.1.91 · 2 Apr 2026
Write Tool Append Mode [Gradual Rollout]
Entry Kind: in v2.1.91, 02 Apr 26
In Development Section of the release
What
The Write tool gains a mode 'overwrite' (default) and 'append ' options, allowing content to be added to the end of a file without rewriting it.
Details
New mode parameter on the Write tool schema Description: "Use 'append' to add content to the end of an existing file instead of rewriting the full content — e.g. for logs, accumulating output, or adding entries" Instruction: "Do NOT re-send the existing file contents" when appending Evidence
Write append mode (gated by tengu_maple_forge_w8k "mode:'append '")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
See this entry in the whole of v2.1.91 →
Names in this entry
setting mode Programs driving Claude Code through the SDK now see more detail about background work and turn context.
setting append Transcript writing can be redirected to a different storage layer, but nothing turns that on here.
flag tengu_maple_forge_w8k
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Related
Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.
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Redundant File Re-Read Prevention [Gradual Rollout]
In v2.1.91 In Development release-page order
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Edit After Write Without Read [Gradual Rollout]
