dsh-dcp
Deterministic context-compaction backend for dsh (DeepSeek Harness): context compaction without an LLM call, works out of the box.
> 简体中文 · English
Why
dsh compacts conversation context by default with compaction-basic, which asks an LLM to re-summarize older messages on every compaction — costly, slow, and non-deterministic. dsh-dcp is a pure-code port of the ideas behind opencode-dcp (dedup, error cleanup, "technical summary instead of prose"):
- Zero LLM calls: compaction itself costs no extra tokens
- Deterministic: identical input always yields identical output
- CJK-friendly: verbatim user text / paths / commands / errors, priced at
real CJK density
- Inherits all official safety: triggers, retained tail, transaction
locks, tool-pairing — dsh's own machinery, only the summarizer is replaced
Effects
vs. the official compaction-basic
| compaction-basic | dsh-dcp | |
|---|---|---|
| Summarization | LLM rewrite per compaction | deterministic code extraction |
| LLM calls per compaction | 1 | 0 |
| Determinism | may differ run to run | identical input → identical output |
| Summary content | semantic | verbatim hard facts (paths/commands/errors/todos/user text) |
| Chinese | model re-transcribes | kept verbatim + CJK-aware pricing |
| Triggers/retention/overflow/safety | official | inherited, identical |
| Checkpoint format | official | compatible (mutually mergeable) |
It also borrows the dedup / error-purge / /dcp / technical-summary ideas from opencode-dcp, re-implemented against dsh's compaction seam — that one serves opencode, this one serves dsh.
CJK adaptation
Content is kept verbatim (no re-transcription into English); tokens are priced at real CJK density (~2 chars/token for Chinese/Japanese/Korean/full-width) instead of the host's flat 4 chars/token that underestimates Chinese — so CJK sessions get a budget that reflects real cost, and checkpoints stay information-dense.
Real dsh session
~80k tokens of history → ~700-token checkpoint (~100x), zero LLM calls; cache-hit rate is barely affected (any backend pays one "cold request" right after a compaction).
A checkpoint produced on a real session (Chinese content kept verbatim):
## Primary Request and Intent
- 帮我把登录页的重定向 bug 修掉
## Files and Code
- /app/src/auth/login.ts — W×1 R×1
## Errors and Fixes
- bash: FAIL src/auth.test.ts
## Pending Jobs
- add regression test
## Critical Context
- dsh-dcp 确定性压缩了 12 条消息 / 8 次工具调用（未调用 LLM 摘要）Not in scope
- No semantic summarization: it preserves facts that appeared, it does not
"understand" code. Need deep semantic checkpoints? Stick with the official compaction-basic
- Things dsh already does, deliberately not re-implemented:
- tool-result pruning (compaction-tool-result-pruner, deterministic by size) - trigger policy, retained tail, overflow recovery (inherited from official; this plugin only adds the round-interval trigger, see below) - /compact command, UI checkpoint cards (shipped with dsh)
Install
Recommended: pair it with our dsh-tui-pi (the TUI already depends on dsh-dcp):
npm i @aiwayds/dsh-tui-pi
dsh plugin add @aiwayds/dsh-dcp # activates dcp; the bundle auto-mountsStandalone:
npm i @aiwayds/dsh-dcp
npx dsh-dcp-setup # safe: date-stamped backup → append-only → idempotent checks> dsh-dcp plugs into dsh's compaction seam and only affects profiles that > mount it. The web profile does not bundle the TUI, so it keeps the official > backend and is unaffected.
/dcp command
| Command | Effect |
|---|---|
/dcp | status: config, compaction count, tokens saved |
/dcp compact | compact now (zero LLM) |
/dcp set <k> <v> | adjust a knob for this session, with a persist hint |
Settable: dedup, purgeErrors, maxItems, maxItemChars, maxSummaryTokens, language, tokenEstimate, thresholdRatio, roundInterval, notice.
The /dcp status also lists every session that has compacted (subagents included): per-session: session-1 (2 compactions, ~444 tokens), child (1 compaction, ~22 tokens). Compactions count per session; disposed sessions (one-shot subagents included) fall out of the overview automatically, and the list is capped at the first 10 sessions (+N more for the rest) so the status stays one line.
Triggers
| Trigger | When | Notes |
|---|---|---|
| Pressure | before every step | tokens ≥ thresholdRatio (inherited upstream default 0.8; this plugin's bundle mounts 0.7 — see config table) × context window |
| Overflow recovery | on a provider context-window error | inherited |
| Round interval | every roundInterval assistant messages | added by this plugin; one round = one LLM roundtrip (each tool-iteration response counts, so one-shot subagents trigger too). Default 50: first compaction after message 50, then every 50 more (100, 150, …); any compaction (pressure included) restarts the clock. Fires at the first idle boundary after the count is reached (below the pressure threshold too). 0 disables; requires the default auto: true |
| Manual | /dcp compact, /compact | anytime |
- Subagents are covered: in-process subagents (including continuable and one-shot children) dispatch through the same events, so pressure/overflow/round triggers count and fire per child session independently. The round trigger counts assistant messages, so a one-shot subagent whose whole run is a single turn (many tool iterations) triggers too.
- Visibility: after every trigger event a one-line notice row (
dcp: compacted N history items (~X tokens, trigger)) is appended to the session; frontends render it as a collapsed row. Note the row also rides the model request context (~15–25 tokens per compaction), and it is on by default since 0.4.0 — disable withnotice: false./dcpstats count every committed region (a pressure retry loop may commit several).
Configuration
All optional, defaults work out of the box:
| Key | Default | Meaning |
|---|---|---|
thresholdRatio | 0.8 | pressure trigger (inherited upstream compaction-basic default 0.8; this plugin's bundle patch mounts 0.7, recommended for CJK-heavy sessions) |
roundInterval | 50 | compact every N assistant messages (one LLM roundtrip) (0 disables). Default 50: 50, 100, 150… — the clock restarts after every compaction |
notice | true | append the one-line compaction notice to the session |
language | zh | summary language; zh also enables Chinese error/"待办：" detection |
tokenEstimate | cjk | CJK (zh/ja/ko/full-width) at ~2 chars/token; ascii matches the host |
dedup | true | annotate repeated tool calls |
purgeErrors | true | collapse stale errors into one note |
maxItems / maxItemChars | 10 / 200 | summary density |
maxSummaryTokens | 2048 | summary token budget |
> Upgrade note (0.5.0): the roundInterval counter switched from completed turns to assistant messages — the same value now triggers more often (a single turn usually contains several assistant messages).
Design reference
- Opencode-DCP/opencode-dynamic-context-pruning
- dsh official compaction seam:
docs/subsystems/compaction.md(deepseek-harness)
Development
npm install && npm test # 65 tests: extractor/compaction/command/config/triggers/setupLicense
MIT