Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.198 Home All releases olderv2.1.197 v2.1.199newer

Precomputed Conversation Compaction Persistence [Gradual Rollout]

Feature flag
tengu_amber_packet 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 v2.1.198: on

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.198. It isn't a statement about your account. What a flag value here can and cannot tell you

What

Conversation compaction results are now pre-computed and persisted to a .precompact.json sidecar file, enabling instant compact rehydration when a session restarts.

Details
  • Feature-gated by tengu_amber_packet; not universally enabled yet
  • Pre-compact file is written to the session directory alongside the transcript
  • At session start, if a valid .precompact.json is found and passes age/model/token-drift checks, the compaction result is reused without re-running the LLM summary
  • Invalidation conditions: model changed, too old, transcript grew or shrank too much, boundary UUID missing
  • Log messages: "precomputed compact: rehydrated", "precomputed compact: persisted", "precomputed compact: rehydrate rejected (<reason>)"
Evidence

File constant (search for ".precompact.json") and feature flag (search for tengu_amber_packet)

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

See this entry in the whole of v2.1.198 →