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Sweep 06 Nov 2026 · 01:32Z Build v2.1.319 537 read Stable v2.1.311 Latest v2.1.318 Next v2.1.319 Feeds RSS JSON llms.txt llms-full.txt Unofficial

Claude Code v2.1.261 ·

New telemetry: prefix-break diagnostics with sampled hashing

New sampled telemetry records detailed hashes around cache-prefix breaks.

Under the hood No documentation found Internal Changes
JSON All of v2.1.261
Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
Prompt CachingArea: what it touches
Internal ChangesKind: in v2.1.261,
Internal ChangesSection of the release

A new tengu_prefix_break_hashes telemetry event records detailed per-message-block hashes and diffs (types, roles, folded attachment info) around a cache-prefix break. It's gated by a sampling rate read from remote config, limited to first-party API usage, and excluded for HIPAA accounts.

Read from
Names in the bundletengu_prefix_break_hashes
What has happened since
Flag reading moved The flag server now returns 0.01 for tengu_iridescent_gem, 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 null for tengu_iridescent_gem, 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 0.01 for tengu_iridescent_gem, 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 null for tengu_iridescent_gem, 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 0.01 for tengu_iridescent_gem, 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 null for tengu_iridescent_gem, 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 0.01 for tengu_iridescent_gem, 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 null for tengu_iridescent_gem, 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.

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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_iridescent_gem

See this entry in the whole of v2.1.261 →

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