summarize¶

Offload (LLM) — lossy, reversible

Compresses the middle of the trajectory into one LLM-written summary; the replaced span is stashed under a marker.

How it works¶

summarize compresses the middle of the trajectory into one LLM-written summary (ported from CE-Manager's ReSum-style summarizer). It restructures the message list to [msg0, <summary system message>, last-K]; the replaced span is stashed under a marker carried in the summary message, so expand restores the full earlier trajectory. This is the one component that changes the message count — apply.Body rebuilds the body keeping the retained messages byte-identical.

The summarizer is grounded in the current task (first user turn + recent turns are passed as "summarize toward this"), not a blind digest of the middle.

summarize calls a model chosen by model.source: incoming (default — reuse the proxied request's own model + key) or config (a dedicated cheap model set via CHEAP_MODEL* env / the gateway's CheapModel). When no model is available it degrades to a no-op.

Gating + reuse: a trigger (min_request_tokens, min_messages; legacy start_from_message folds into min_messages) gates the first summary so it fires only on a large/deep transcript. After that, the summary is checkpointed per session and reused verbatim (no model call, and byte-identical so the prefix stays KV-cache stable) until the un-summarized tail grows past resummarize_tokens, when the checkpoint rolls forward with a fresh summary. This is what stops it re-summarizing every turn.

Run it alone (its own preset) — it restructures the whole transcript.

Before → After¶

before:  [system, u1, tool, a1, tool, u2, … 30 turns …, uN-1, uN]
after:   [system, "=== History Summary === … <summary> … <<cg:…>>", uN-1, uN]

Lossiness¶

Lossy but reversible — the replaced span is stashed under the summary message's marker and recovered via context_guru_expand / GET /expand.

Configuration¶

Key	Default	Meaning
`summary_level`	`regular`	`concise` \| `regular` \| `highly_detailed`.
`keep_last`	3	Trailing messages kept verbatim.
`min_tokens`	500	Span floor — minimum middle size before summarizing.
`include_tool_calls`	`false`	`false` → tool outputs masked in the summarized trajectory.
`resummarize_tokens`	6000	Tail growth that triggers rolling the checkpoint forward.
`model.source`	`incoming`	LLM source: `incoming` (proxied model+key) or `config` (cheap model).
`trigger`	—	Gates the first summary: `min_request_tokens`, `min_messages`.

When it shines¶

Long agentic sessions where the bulk is stale middle context.

When it's inert¶

Transcript below trigger, span below min_tokens, or no model available (no-op).