# agent-compact

English · [简体中文](README.zh-CN.md)

Context compression for [DeepSeek Harness](https://github.com/deepseek-ai/deepseek-harness): lets the **agent autonomously call** `context_compact` to compress a span of the conversation it chooses — the finished, no-longer-needed middle — and replace it with a checkpoint the agent writes itself.

## Why

Compaction is normally a full-context sweep: the official engine only ever compresses from the start of the conversation, so the opening's task plan and direction are **partially lost along with the compressed information**. `context_compact` compresses **only the span the agent selects** — a finished step, a debugged log exchange, an off-track discussion — while the important opening and the recent context stay intact. Span compaction keeps **information loss from compaction as small as possible** — like human memory, the middle is not compressed indiscriminately: what can be summarized is consolidated into a checkpoint, and important details stay word-for-word — the agent decides what is truly dead, and only that gets condensed.

Typical moments to use it:

- a task step is done — compress it, keep the remaining steps and the active instruction live;
- a bug hunt or a wrong research direction is over — compress that exchange into a short "what went wrong / root cause / fix" note;
- the opening requirements are stale — compress the start and restate the current intent.

## What it does

- The agent picks the span via `startAnchor` / `endAnchor` (unique-prefix matching, CJK punctuation-width tolerant) and passes a **required** `summary` — the Markdown checkpoint it wrote itself.
- The raw span is archived to the spill store first (`~/.dsh/spill/session-<hash>/<hex>-<seq>.txt`, sequential naming, restart-safe); the path is echoed in the shadow message so the model can read the raw text back.
- The host engine runs the stock transaction — boundary validation, tool-pair balance, surface replacement — with **no separate LLM summarizer request**.

The tool call itself happens inside the agent's normal turn and is billed like any other turn; what is avoided is only the *extra* summarizer request the official engine would make for the same span.

## Install

```sh
# from a published registry package
dsh plugin --profile web add @mimichunterz/agent-compact

# or from a local checkout
dsh plugin --profile web add ./agent-compact
```

`dsh plugin` forwards to pnpm in the profile directory and appends the bundle to `dsh.profile.bundles` (see the official [publish guide](https://github.com/deepseek-ai/deepseek-harness/blob/master/docs/user/develop/basic/publish.md)). **Restart the profile** — every session then sees the `context_compact` tool.

The bundle's own `cordis.patch.yml` pins the spill archive root to `~/.dsh/spill` (deployments can override it again through the profile's `cordis.patch.yml`).

## Uninstall

```sh
dsh plugin --profile web remove @mimichunterz/agent-compact
```

`dsh plugin remove` forwards to `pnpm remove` in the profile directory: it uninstalls the package and reconciles the bundle out of `dsh.profile.bundles`. **Restart the profile** — every session then stops seeing the `context_compact` tool. The same package name works whether you installed from the registry or from a local checkout.

If the plugin was additionally mounted through a row in the profile's `cordis.patch.yml` (dev mode), remove that row too, otherwise the patch re-mounts it on the next boot.

## Configuration

| field | default | meaning |
|---|---|---|
| `autoArchive` | `true` | `context_compact` saves the full raw span to a spill artifact before replacing it |

Pass through the inserted row in the profile's `cordis.patch.yml` or a bundle patch.

## How it works

- **Agent-written checkpoint**: `summary` is mandatory, so the tool path always uses the checkpoint the agent wrote. `patchEngine()` (see `src/optimizer.ts`) wraps the engine's `summarize()`: when an `_externalSummary` is present (one-shot, keyed per session id), it returns that text directly; only when none is present does it forward to the stock implementation — a branch that serves the automatic compaction path and keeps official behavior intact.
- **Anchor matching** (`src/normalize.ts`): `normText` collapses whitespace and maps CJK full-width punctuation to half-width (，→, etc.), applied to both anchors and node text. Matching keeps **unique-prefix** semantics: zero hits → "not found" with closest-node hints; more than one hit → "AMBIGUOUS".
- **Restart-safe sequential archives**: the next number is derived by scanning the session's spill directory (`max+1`) — gap-free; the backend's random hex prefix makes filename collisions impossible.
- **Paired cleanup**: the tool-call message (carrying the full `summary` argument) and its tool/result are each replaced by one tiny shadow message, so the checkpoint text never appears twice on the surface (skipped when the message holds more than one tool call).

## Compatibility

- Built and verified against DeepSeek Harness `0.1.0-rc.6` (`@deepseek-ai/dsh-compaction-basic@0.1.0-rc.6`).
- Only **one compaction per session at a time** (the engine transaction is serialized); anchors re-resolve on every call, so later compactions never go stale after earlier checkpoints replaced old nodes.
- With a local spill backend the root is fixed; other backends degrade gracefully (no `root` field → in-memory counter), and compaction itself is unaffected.

## License

MIT. The patch derives from `@deepseek-ai/dsh-compaction-basic` and related DeepSeek Harness packages (MIT, Copyright DeepSeek) — see [`LICENSE`](LICENSE).