Live context reduction already runs on ContextCompressionMiddleware + MessageTrimMiddleware + tinyagents/summarize.rs; microcompact and cache-align live as TinyAgents middlewares. This workstream deletes the superseded originals and adopts the crate cache layer.

Current status (2026-07-02): the legacy reducers are gone. context/ is 1237 lines total, including 1051 lines across prompt assembly (prompt.rs, channels_prompt.rs), session-memory bookkeeping (session_memory.rs), and stats/config state (manager.rs, stats.rs). The inert legacy compaction-breaker stats have also been removed. Those files remain product-owned; cache correctness work now targets TinyAgents middleware and crate cache events.

Target SDK surface: ResponseCache/InMemoryResponseCache + cache_key, CachePolicy { response_cache_enabled, protect_prompt_prefix }, PromptCacheLayout + PromptCacheGuardMiddleware + CacheLayoutEvent, AgentEvent::{CacheHit, CacheMiss, Compressed}, SummaryRecord, ModelRequest::cache_segments(Vec<PromptSegment>).

Steps:

01-delete-legacy-context.md — remove dead reducers, consolidate stats.
02-cache-layer.md — response cache + prompt-prefix protection.

Done when: context/ contains only OpenHuman-specific state (prompt assembly inputs, session-memory bookkeeping, stats projection) and cache correctness is asserted by crate events, not warn-logs.

Keep (product): context/manager.rs prompt-assembly surface, session_memory.rs, channels_prompt.rs, context/stats for the UI utilisation footer.