dsh-negative-ledger

A negative-knowledge ledger for coding agents. It records only disproven paths — failed commands, missing files, rejected approaches, unavailable APIs — together with the evidence behind each conclusion and the conditions under which a retry becomes legitimate. When the evidence changes, the conclusion is invalidated automatically.

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What it is not

• Not memory: no positive knowledge, no semantic recall.
• Not a cache: it stores conclusions, not tool results.
• Not a bug regression tracker: it covers any tool call and file read, not just fix attempts.

The core loop

1. A tool call fails (non-zero exit, FS_NOT_FOUND, …) → a negative fact is recorded with outcome witnesses (exit code, error code) and precondition witnesses (file state from DSH's fs/observed).
2. The next identical attempt matches the fact's fingerprint (normalized command + cwd, or file path).
3. While every precondition witness is unchanged, the attempt is warned (warn mode) or denied (block mode).
4. Any precondition change marks the fact stale — the reminder is withdrawn and the retry is allowed. A successful retry marks it resolved.

The differentiation: a DSH-native, evidence-bound persistent negative-memory gate — failure conclusions activate and revoke themselves with the environmental evidence, and stay transactionally consistent across concurrent agents.

Quick start — one-command install

dsh plugin --profile <name> add @akslcw/dsh-negative-ledger

Installs the package and activates its bundle layer: the shipped cordis.patch.yml (declared by the dsh.bundle manifest) mounts the ledger policy with production defaults — sqlite backend, warn mode, .ledger directory, default TTLs. Verify without booting, then boot:

dsh --profile <name> --dump-config   # the "@akslcw/dsh-negative-ledger" layer and its negative-ledger row
dsh --profile <name>                 # boot

Remove: dsh plugin --profile <name> remove @akslcw/dsh-negative-ledger. A clean-environment end-to-end smoke (add → layer → headless warn + sqlite ledger → remove → profile still boots) is powershell -File smoke/plugin-add-smoke.ps1.

pnpm 11 note: pnpm ≥11 turns "ignored build scripts" into a hard error and fails the add with ERR_PNPM_IGNORED_BUILDS: better-sqlite3. better-sqlite3 ships official prebuilds, so the ignored script is harmless — no compilation happens. In the profile directory run pnpm config set --location project strict-dep-builds false, then re-run the add. (Allowing the build instead would compile better-sqlite3 from source and require a C++ toolchain.)

In-checkout hacking (engine and CLI only, no DSH composition):

node src/cli.ts --dir .ledger stats
node demos/run-demos.ts      # S1 command dedup, S2 missing-file dedup, S3 evidence-change invalidation
node smoke/real-mount.ts     # real-mount smoke inside a deepseek-harness checkout

Requires Node ^22.19.0 || >=24.0.0 (aligned with the official DSH engines range).

CLI

node src/cli.ts [--dir <path>] [--backend sqlite|jsonl] <list | show <id> | stale | stats>

The backend flag wins; otherwise the directory is auto-detected (ledger.db → sqlite, ledger.jsonl → jsonl); with neither present the primary sqlite backend is used.

Engine API

Two store backends sit behind one LedgerStore seam: the default transactional SQLite store (SqliteLedgerStore: WAL, revision-based optimistic concurrency, operation receipts, retry leases, JSONL import) and the legacy single-process JSONL store (JsonlLedgerStore).

• getFact(scope, kind, fingerprint) / queryFacts(filter) — current facts with revision and active-lease summaries.
• commitAttemptDecision(request) — the only decision entry: deny / observe-warn / verify-retry (allow and stale-allow both compete for a lease); revision conflicts re-read and re-decide.
• recordFact(input, meta) — records a disproven path; repeats append versions on the same id; idempotent by operation receipt and (fact, toolCallId, operation_kind).
• transitionFacts(batch, meta) — batched, all-or-nothing state transitions (one FS observation can invalidate many facts).
• settleLease(settlement) — the lease holder's retry outcome: succeeded → resolved, failed → new evidence version, released → fact untouched.
• summarize(scope?) — three honest counters: duplicateFailuresObserved, warningsEmitted, callsDenied. No token estimates — trajectory replay/A-B diffing owns that number.

DSH integration

Compatibility: tested with @deepseek-ai/dsh-tools 0.1.1-rc.2. The package declares >=0.1.1-rc.2 <0.2.0 as an optional peer range, so it documents the supported DSH event surface without installing a second DSH runtime.

The bundle layer shipped in the package is exactly:

- id: negative-ledger
  name: '@akslcw/dsh-negative-ledger'

Override the row by id in a later layer (your profile's cordis.patch.yml) — a patch replaces the whole config, so restate every key you change:

- id: negative-ledger
  name: '@akslcw/dsh-negative-ledger'
  config:
    backend: sqlite       # sqlite (default, transactional) | jsonl (legacy single-process)
    mode: block           # off | warn | block (default warn)
    dir: .ledger          # ledger directory (default .ledger)
    commandRetryAfterMs: 300000   # TTL on auto-recorded command facts
    commandTools: [bash, pwsh]   # recorded as command_failed
    readTools: [read]            # recorded as file_missing

• The store connection and the background invalidation queue are owned by the plugin fiber: disposal drains the queue and closes the store (HMR-safe).

• warn (default): attaches additionalContexts on tools/post-execute; never blocks, never rewrites tool results.

• block: denies at tools/pre-execute before dispatch. Denied calls still flow through post-execute and are recognized by the plugin's own denial prefix, so one attempt is never double-counted.

• Auto-recorded command facts carry a short after TTL (commandRetryAfterMs, default 5 minutes): block mode releases them automatically instead of locking a command forever on transient failures. never/manual are reserved for facts an explicit, trusted author recorded.

• off: disables recording and interception entirely.

• fs/observed events (present with version, or absent) map one-to-one onto file-state precondition witnesses; the emitting execution is correlated so a model-supplied path (scoped by the session cwd) and the backend's resolved displayPath witness the same fact; every observation change drives invalidation, so file hashing is never needed.

• Successful tool results resolve the fact through settlement or a lease-free transition — the reminder is withdrawn after a working retry.

• The ledger is shared across agents (subagents do not repeat the parent's failures); counters are transactional columns (sqlite) or append-only hit lines (jsonl).

Security posture:

• Claims never embed raw command text; model-facing previews are control-character-sanitized and length-capped. Raw commands stay in the ledger FILE (they are the fingerprint) — the file is written 0600 inside a 0700 directory.
• The ledger renders facts as quoted data, never as instructions.
• Single-writer JSONL applies to the legacy backend only; the sqlite backend is multi-process (WAL).

Boundary with repeat-tool-reminder: that guard nudges on byte-identical consecutive repeats within one session; the ledger is persistent, evidence-bound, and auto-invalidating across sessions.

Retry decisions and warning frequency

Without configured dependencies and a complete fresh pre-dispatch observation snapshot, command failures carry only outcomes and a cooldown. A repaired file then cannot unlock a command before TTL expiry in block mode. Messages now describe the recorded cooldown and distinguish missing preconditions from incomplete or matching current evidence. The conservative verdict for unknown evidence is unchanged.

warningRepeatAfterMs defaults to 60000; 0 disables suppression for text-only evaluation. Repeated advisories are limited per policy instance, session, and fact. Changed failure evidence, interval expiry, or an allowed verification permits another warning. The in-memory cache holds at most 256 entries per session; sessions remain independent and denial reasons are always returned.

Warnings no longer carry cumulative totals; use CLI stats. Suppressed repeats still increment duplicateFailuresObserved, while only attached repeat advisories increment warningsEmitted. No online cost improvement is claimed. See the development retry contract for validation and the P2 boundary.

Explicit command dependencies

Add trusted rules to the plugin config to permit verification after observed dependency changes:

commandEvidenceMaxAgeMs: 60000
commandDependencies:
  - tool: bash
    commandLine: npm test
    cwd: /workspace/my-project
    files:
      - /workspace/my-project/package.json
      - /workspace/my-project/test.config.js

Tool, full command text, and effective cwd must match exactly. Files are absolute DSH displayPath values; no globbing or shell dependency inference is performed. All dependencies need fs/observed observations before execution. A declaration is not an observation. Received observations older than commandEvidenceMaxAgeMs (default 60 seconds) are unknown; the policy falls back to TTL. No extra filesystem reads or hashing are performed.

Failure records use pre-dispatch evidence, never retroactively captured observations. A fresh changed dependency permits verification, while unrelated changes do not. Only successful execution resolves the fact. Another process or restarted policy needs its own observations. With no rules, existing command behavior is preserved.

Known limitations and deferred work

• Single-writer JSONL (legacy): backend: jsonl keeps the v0 single-process store for migrations and debugging; concurrent multi-process writers are unsupported there. The default backend: sqlite is the transactional WAL store with unique indexes, idempotent operation receipts, and crash recovery.
• Command fingerprints use the calling agent's session cwd; a sandbox-policy workspace-root override is not visible to the plugin. Raw command text is preserved (no whitespace collapsing) so semantically different shell programs never collide, but equivalent re-spellings do.
• A non-zero exit does not always disprove a path (e.g. grep exits 1 for "no match"); the short TTL and the warn-default posture bound the damage, but per-tool recording policy is deferred.
• v0 matches exact fingerprints only; no semantic similarity.
• approach_rejected and api_unavailable kinds exist in the model but are not wired to tools yet.
• Token savings are deliberately not estimated here; the trajectory lab (#4) owns A/B and replay diffs.
• Future seams: failed_attempts in subagent contract results (#1), active/stale projection into task checkpoints (#3), repeat-failure rates in trajectory regression (#4), fail-closed promotion of high-risk paths (#2).