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.

中文

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 Any precondition change marks the fact stale — the reminder is withdrawn and the retry is allowed.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

# engine only
node src/cli.ts --dir .ledger stats

# the three reproducible demos (S1 command dedup, S2 missing-file dedup,
# S3 evidence-change invalidation) with acceptance checks and a savings report
node demos/run-demos.ts

# real-mount smoke (run inside a deepseek-harness checkout with built libs):
# boots the actual agent spine + fs provider + read/write tools, drives a
# scripted model, and asserts the warning reaches the model's next request
node smoke/real-mount.ts

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

CLI

node src/cli.ts [--dir 
] [--backend sqlite|jsonl]  | 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.

Command	Output
list	Every fact: status, kind, id, claim
show	One fact as pretty JSON
stale	Facts invalidated by evidence change
stats	Honest interception counters (duplicate failures observed, warnings emitted, calls denied)

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

- id: negative-ledger
  name: dsh-negative-ledger
  config:
    backend: sqlite       # sqlite (default, transactional) | jsonl (legacy single-process)
    mode: warn            # 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.

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).