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Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.252 ·

Incremental CLAUDE.md / tool-description context diffing ('instructions' attachments)

Claude Code now only re-sends changed CLAUDE.md/instruction files instead of the whole block each turn, saving tokens.

TierYou'll noticehow much it should matter to you
Useful3my rating, 1 to 5
Signal3worth watching, 1 to 5
AreaContext Managementwhat it touches
KindImprovementsin v2.1.252,
You'll notice

Claude Code now only re-sends changed CLAUDE.md/instruction files instead of the whole block each turn, saving tokens.

New machinery (RTt, PTt, dEt, pEt, yjt) diffs the currently-announced set of CLAUDE.md/instruction files against what was last sent, emitting a smaller 'instructions' attachment describing only what changed plus a list of removed files, instead of re-sending the full instructions block every turn. Messages include lines like 'Instruction files were re-read ...; these differ from their earlier copies' and 'Instructions no longer present: ...'.

A companion 'prompt_snapshot' attachment type records the exact system prompt and tool descriptions sent, reused via Use()/BUn() so unchanged tool descriptions don't need to be recomputed or re-sent (recordedDescription passed into dA/oie).

Read from
Feature flag
tengu_carved_slate Off in both readings

The flag server returned off for the account this site reads and for the anonymous baseline. A reading of off cannot rule out a rollout these two readings sit outside of.

This account: off · anonymous baseline: off · compiled default in v2.1.252: not a boolean we can read

Read once, for one account on one subscription tier, against v2.1.252. It isn't a statement about your account. What a flag value here can and cannot tell you

What has happened since
Flag reading moved The flag server now returns on for tengu_carved_slate, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns nothing at all, having stopped carrying it for tengu_carved_slate, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.

See this across every release →

See this entry in the whole of v2.1.252 →

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