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dsh-smart-compact

A custom CompactionEngine backend for the
DeepSeek Harness: configurable threshold prompting, a mandatory
auto-compaction safety net at the limit, DCP-style dedup / purge
suggestions, a fully configurable summary prompt, and a /compact command
that keeps the original engine-driven behavior.

Why the name? The strategy families — deduplication of repeated tool
outputs, purging errored calls, a model-driven compress tool and nudges —
are inspired by DCP (Dynamic Context Pruning), the opencode-dcp
approach to keeping long sessions cheap. The mechanism is different:
opencode-dcp prunes only the outbound LLM payload without touching session
history, while this engine lives on the DSH CompactionEngine seam and
writes standard durable compaction brackets into the session log (zero
external state, originals never deleted). "smart-compact" names the
mechanism; the DCP lineage lives in the strategy module (dcp.ts) and the
dcp_status tool.

Zero external state. No kernel, no ledger files, no database, no
in-memory state that must stay in sync with the log. Every compression is a
standard durable bracket in the append-only session log:

compaction/start  →  compaction/summary  →  user/message (surface replace)  →  compaction/end

Original events are never deleted; block information is rebuilt from the
log on demand (rebuildBlockLedger), so a crash, restart, or resumed session
always sees a consistent picture.

Mount

One compaction backend per realm — disable the stock compaction-basic row
and add this one to your composition (e.g. ~/.dsh/profiles/web/cordis.patch.yml):

- id: compaction-smart
  name: 'dsh-smart-compact'
  config:
    thresholdRatio: 0.5
    mandatoryRatio: 0.9
    summarizationMaxTokens: 8192
    preserveRecent: 5
    dedupEnabled: true
    purgeErroredTurns: 4
    summaryPrompt: |
      Write ONE dense technical summary of the content below.
      Preserve exact paths, commands, error strings, identifiers,
      decisions and pending work; discard spent detail.
      {content}

The package registers itself as ctx.compaction. Restart dsh web after a
composition change (the web profile runs without HMR).

Configuration

Behavior

• Threshold prompting — a short advisory nudge is injected once the
  surface usage crosses thresholdRatio. The system prompt section explains
  the compress tool (range/message modes) and points at dcp_status.
• Mandatory auto-compaction — when usage reaches mandatoryRatio (or the
  provider confirms context-overflow), the engine auto-compacts the largest
  compressible span with an engine-written summary. This is a hard safety
  net, gated once per turn.
• /compact — engine-driven LLM summary of the largest compressible span,
  serialized against driver turns via runMaintenance; failures surface as
  classified ManualCompactionErrors (busy, cancelled, changed,
  summary, commit).
• DCP-inspired suggestions — dcp_status reports dedup (repeated tool
  outputs) and purge (errored turns) candidates plus the current pressure and
  compressible ranges.
• Safety — direct paths refuse to shadow compaction checkpoints or the
  latest user message; configured protected tools and (optionally) every user
  message are never compressed; tool-call/result pairs stay balanced; the
  durable compaction/start lock is opened before summarization and always
  released (success or recorded failure).

Development

npm install
npm run typecheck
npm test        # node --import tsx --test tests/*.test.ts
npm run build

License

MIT