opencode-smart-compact

Smart compaction for OpenCode V2 — a port of Alper's pi-smart-compact ESV pipeline (Extract → Synthesize → Verify) to the V2 plugin API.

When OpenCode compacts a session, this plugin replaces the built-in summary with a verified one — or abstains and lets OpenCode's native compaction run unchanged (fail-closed).

What it does

On the compaction hook:

1. Prune — dedupe repeated read/search results within a mutation epoch, truncate oversized tool outputs.
2. Extract (deterministic, no LLM) — files modified/read/deleted, errors with retry/resolve tracking, constraints (EN + TR), decisions, open loops, session type, main goal.
3. Synthesize — one LLM call (single-pass) guided by the deterministic facts. If the call fails or returns malformed output, a deterministic fallback skeleton is assembled instead.
4. Verify — structural checks (required sections, path coverage, error evidence, semantic constraint/goal coverage, fabricated-file detection, consistency, unsupported high-risk claims like "all tests passed"), then deterministic repair rounds → one optional LLM patch → deterministic quality floor. A summary that still fails is never applied.
5. Yield gate — the summary must actually save tokens (default: ≥ 10% of the compacted window), otherwise abstain.

Abstention (small transcript < 5k tokens, verification rejection, yield rejection, timeout, any error) always leaves event.result unset, so the host's native compaction proceeds as if the plugin weren't there.

Install

Add the package to plugins in opencode.jsonc (project or global):

{
  "$schema": "https://opencode.ai/config.json",
  "plugins": ["opencode-smart-compact"]
}

Pin a version with "opencode-smart-compact@0.1.0". To use a local checkout instead, point plugins at its directory ("./path/to/opencode-smart-compact" or a file:// URL).

Configuration

Plugin options (via the plugins object form in opencode.jsonc) or env vars:

Option	Env	Default	Meaning
enabled	OPENCODE_SMART_COMPACT_ENABLED	true	Set 0/false to disable.
summaryModel	OPENCODE_SMART_COMPACT_MODEL	session model	"provider/model" for synthesis.
verifyModel	OPENCODE_SMART_COMPACT_VERIFY_MODEL	summary model	"provider/model" for the LLM patch.
minYield	OPENCODE_SMART_COMPACT_MIN_YIELD	0.1	Minimum relative token saving.
timeoutMs	OPENCODE_SMART_COMPACT_TIMEOUT_MS	120000	Pipeline timeout; abstain on expiry.

Tip: point summaryModel at a cheap model — the verify gate keeps quality honest regardless of which model wrote the draft.

MVP scope

Deliberately not ported (yet): the multi-pass Explore phase, smart_recall / smart_save_memory tools, and the TUI status layer. The V2 hook runs synchronously at compaction time, so Pi's handoff/pending-slot machinery was dropped by design.

Development

bun install
bun test
bun build src/index.ts --target=bun --outfile /dev/null   # syntax gate