Sweep 19 Sep 2026 · 02:36Z Build v2.1.278 500 read Stable v2.1.267 Latest v2.1.278 Next v2.1.278 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.252 ·

New instructionFiles context channel behind carved-slate flag

Under an experimental mode, empty CLAUDE.md content is now sent as an explicit empty string to keep prompt caching stable.

TierUnder the hoodhow much it should matter to you
Useful1my rating, 1 to 5
Signal1worth watching, 1 to 5
AreaSystem Promptwhat it touches
KindInternal Changesin v2.1.252,
Group of 3 Under the hood

Under an experimental mode, empty CLAUDE.md content is now sent as an explicit empty string to keep prompt caching stable.

The per-session context builder now tracks a separate instructionFiles field alongside memoryFiles, via new userContextInstructionFiles state. This path only runs when the Ml() gate (checking CLAUDE_CODE_CARVED_SLATE or the tengu_carved_slate remote flag, default false) is enabled; otherwise it is short-circuited. The context refresh function that clears/rebuilds this cached user context now also takes a refreshReason argument (session_start, compaction, policy_refresh, directory_added, settings_sync, account_change), shown to the model via strings like "after the conversation was compacted" or "after the organization's managed settings changed".

When the same carved-slate gate is on and there is no CLAUDE.md content, the context block now explicitly emits claudeMd: "" instead of omitting the key, keeping the block structure stable, likely for prompt caching.

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 →