{"version":"2.1.265","anchor":"precomputed-conversation-compaction-rehydration-gated-off","canonical_anchor":"resume-session-dialog-can-show-instant-summary-resume-when","heading":"Resuming a session can reuse a precomputed compaction summary instead of recompacting","tier":"notice","area":"Compaction","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.265\/e\/precomputed-conversation-compaction-rehydration-gated-off","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.265","markdown":"### Resuming a session can reuse a precomputed compaction summary instead of recompacting\n\nSession resume can now skip recomputing a conversation summary by reusing one precomputed ahead of time (feature-gated)\n\n**What**\n\n- A new path lets the agent loop reuse a previously precomputed compaction summary, built ahead of time and cached by session id, model, and boundary, instead of running compaction fresh.\n\n- The cached summary is validated before use: its age, model match, and token growth are checked, with rejection reasons including `session_mismatch`, `model_mismatch`, `bad_timestamp`, `too_old`, `grew_too_much`, `shrank_too_much`, and `preserve_uuid_missing`. A successful reuse emits `tengu_precomputed_compact_rehydrated`.\n\n- The session-resume warning dialog now shows a \"Resume from summary (instant, recommended)\" label instead of the usual \"Resume from summary (recommended)\" when a precomputed summary is available (`hasPrecomputedSummary`).\n\n- The resume flow, gated by `tengu_gleaming_fair_reuse` (extending `tengu_gleaming_fair`), can skip recomputation entirely, or detect that a precomputed summary has gone stale.\n\n**Why** Recomputing a full conversation summary on every resume is slow; reusing a precomputed one when it's still valid should make resuming a session noticeably faster. The feature is currently gated off.\n\n- Flag `tengu_sepia_moth`: Not enough to say (read for one account on one subscription tier against v2.1.265; this account: no value returned, anonymous baseline: off, compiled default: off)\n- Flag `tengu_amber_packet`: Not enough to say (read for one account on one subscription tier against v2.1.265; this account: no value returned, anonymous baseline: off, compiled default: off)\n- Area: Compaction\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 3\/5\n- Present in the build but not switched on"}