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Claude Code v2.1.246 ·

Prompt and context experiment renamed to tengu_expressive_whistle, four other switches retired

A prompt-and-context experiment switch was renamed and four other switches disappeared entirely.

Under the hood Nothing to try yet In Development
JSON All of v2.1.246
Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
0Signal: worth watching, 1 to 5
InternalsArea: what it touches
In DevelopmentKind: in v2.1.246,
In DevelopmentSection of the release

The guarded prompt and context work now reads tengu_expressive_whistle, off by default, and four older switch names were removed.

What

A remotely controlled switch guarding unreleased prompt and context work now goes by tengu_expressive_whistle instead of tengu_saffron_anchor, keeping the same reader function behind the new name. It defaults to off when the server sends no value, and the code it guards returns immediately while off, so nothing changes for you in this build. Four unrelated switch names that existed in v2.1.245 are gone from this build along with the functions that read them, meaning whatever they controlled is now either permanently on or removed.

Details
  • tengu_saffron_anchor no longer appears anywhere in the build; only the new name is read.
  • With the switch unset or off, the guarded prompt and context path exits at once and takes no other action.
  • The four fully retired switches are tengu_prompt_cache_diagnostics, which guarded prompt-cache diagnostics, tengu_dazzling_floyd, which was read as a negated gate so that its absence enabled the behaviour, tengu_cobalt_plinth_reader_persist, and tengu_bg_retire_grace_bridged_min, which supplied a 480 minute grace period converted to milliseconds.
  • No user-facing setting, command-line flag or environment variable is attached to any of these; they are server-controlled experiment switches only.
Evidence

tengu_expressive_whistle, tengu_bg_retire_grace_bridged_min

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Read from
Feature flag
tengu_expressive_whistle Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.246: off

tengu_saffron_anchor On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.246: not a boolean we can read

tengu_prompt_cache_diagnostics On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.246: not a boolean we can read

tengu_dazzling_floyd Gate removed from the code

This release deleted the gate from the code while it was still reading on for the account this site reads, so the code path no longer asks a flag before running.

This account: on · anonymous baseline: on · compiled default in v2.1.246: not a boolean we can read

tengu_cobalt_plinth_reader_persist On for this account, and not off by default

The flag server returned on for the one account this site reads, and nothing in this release compiles it off by default. The compiled default is shown below, and says which it is when we cannot read one: a fifth of gates compile in a string or a number rather than on or off, and most published releases have no gate table behind them at all. No client can see what the server returns for your account.

This account: on · anonymous baseline: on · compiled default in v2.1.246: not a boolean we can read

Read once, for one account on one subscription tier, against v2.1.246. 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_cobalt_plinth_reader_persist, 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_cobalt_plinth_reader_persist, 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.
Gate removed from the code v2.1.246 removed the tengu_dazzling_floyd gate from the code while it was still reading on for the account this site reads. The code path no longer asks a flag before it runs.
Gate removed from the code v2.1.223 removed the tengu_dazzling_floyd gate from the code while it was still reading on for the account this site reads. The code path no longer asks a flag before it runs.

See this across every release →

How sure we are
One source agreesOne thing we can check says the same as this entry.
The name it cites is new in this buildNew in this build: tengu_expressive_whistle

See this entry in the whole of v2.1.246 →

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