Sleep-Time Compute

• Entity ID: ent-20260410-1925d34d7e64
• Type: concept
• Scope: shared
• Status: active

Description

The UC Berkeley paper "Sleep-time Compute for LLMs" (arXiv:2504.13171, April 2025) demonstrated that LLMs can pre-compute inferences during user idle time, reducing test-time compute by approximately 5x at equal accuracy. The core insight is that models can do useful work between user interactions, amortizing expensive reasoning across idle periods.

Claude Code's auto-dream system implements sleep-time compute but inverts the direction: where the paper's approach pre-computes answers to predicted future queries, auto-dream consolidates past memory -- merging, pruning, and reorganizing the accumulated knowledge from prior sessions so that future sessions boot faster and with higher-quality context. The paper looks forward; auto-dream looks backward.

The paper's key finding that consolidation requires sufficient accumulated data maps directly to auto-dream's minSessions: 5 threshold -- the system does not trigger consolidation until at least 5 sessions have accumulated since the last dream, ensuring there is enough signal to justify the compute cost.

Key claims

• Sleep-time compute reduces test-time compute by ~5x at equal accuracy by pre-computing during idle periods (paper finding).
• Auto-dream inverts the direction: consolidates past memory instead of predicting future queries. Both exploit the same idle-time window.
• The minSessions: 5 gate mirrors the paper's finding that consolidation needs sufficient accumulated data to be worthwhile.
• Auto-dream runs as a forked subagent via runForkedAgent() -- a background process that shares the parent's prompt cache but has isolated mutable state, read-only Bash access, and write access restricted to the memory directory.
• The four-gate trigger system (time >= 24h, sessions >= 5, scan throttle >= 10min, filesystem lock) is ordered by computational cost, cheapest first, so most invocations bail early with minimal overhead (one stat call per turn when enabled).
• The consolidation prompt instructs the agent through four phases: Orient (read memory index), Gather Signal (grep transcripts narrowly), Consolidate (merge/deduplicate/correct), and Prune & Index (keep MEMORY.md under 200 lines / 25KB).
• The feature is gated behind tengu_onyx_plover (GrowthBook) with a user-level override via autoDreamEnabled in settings.json. Also gated off in KAIROS mode (which uses its own disk-skill dream), remote mode, and when auto-memory is disabled.
• On failure, the consolidation lock's mtime is rolled back to its pre-acquire value so the time gate passes again on the next eligible turn; the 10-minute scan throttle acts as a natural backoff.
• The dream task is surfaced in the UI via the existing task registry (footer pill + Shift+Down dialog) through DreamTask.ts, which tracks phases (starting -> updating), files touched, and assistant turns for live progress display.

Relations

• implements auto-dream -- auto-dream is Claude Code's concrete implementation of the sleep-time compute concept
• depends-on consolidation-lock -- the .consolidate-lock file whose mtime serves as lastConsolidatedAt and whose body holds the locker's PID
• depends-on forked-agent-pattern -- the runForkedAgent() primitive that provides cache sharing, isolated state, and usage tracking
• uses four-phase-consolidation-prompt -- the buildConsolidationPrompt() output that structures the dream agent's work
• related-to auto-memory -- auto-dream consolidates what auto-memory (extractMemories) writes; the two share createAutoMemCanUseTool() for sandboxed memory-directory writes
• related-to kairos -- KAIROS mode disables auto-dream's in-place rewrites (its sessions are perpetual); instead KAIROS writes append-only daily logs that auto-dream later distills

Sources

• arXiv:2504.13171 -- "Sleep-time Compute for LLMs" (UC Berkeley, April 2025)
• src/services/autoDream/autoDream.ts -- main scheduling logic, gate checks, forked agent orchestration
• src/services/autoDream/config.ts -- isAutoDreamEnabled() with GrowthBook + settings.json resolution
• src/services/autoDream/consolidationLock.ts -- lock file mechanics, mtime-as-timestamp, PID-based conflict detection
• src/services/autoDream/consolidationPrompt.ts -- buildConsolidationPrompt() with four-phase structure
• src/tasks/DreamTask/DreamTask.ts -- UI task registration, progress tracking, kill/rollback handling
• src/query/stopHooks.ts -- integration point: executeAutoDream() fires after each main-thread turn in non-bare mode
• src/utils/backgroundHousekeeping.ts -- initAutoDream() called at startup alongside extractMemories and MagicDocs