test(hooks): cross-backend adversarial parity suite + A3 closeout (durable backend PR 4/4)

[zmanian]

Cross-backend adversarial parity suite (durable-backend PR 4/4)

The final PR of the durable-predicate-backend split. Lands a new test-only
crate ironclaw_hooks_parity that proves the three PredicateStateBackend
implementations are behaviorally interchangeable by feeding the SAME scripted
input to all of them and cross-asserting identical observable output.

Builds on:

• refactor(hooks): make PredicateStateBackend a stable public async contract (durable backend PR 1/4) #3927 — trait + in-memory + contract harness (merged to reborn-integration, d5e6434ec)
• feat(hooks): PostgresPredicateStateBackend (durable backend PR 2/4, replaces #3932) #3933 — Postgres backend (ironclaw_hooks_postgres)
• feat(hooks): LibSqlPredicateStateBackend in own crate (durable backend PR 3/4, replaces #3930) #3936 — libSQL backend (ironclaw_hooks_libsql)

Merge order: this PR merges both backend branches into its working tree so
all three backends compile together, and should land after #3933 and #3936
(both will merge into reborn-integration independently first; base here is
reborn-integration).

Parity matrix (tests/parity_matrix.rs) — load-bearing

One deterministic scripted sequence (fixed ids/timestamps/values, no wall
clock) is fed to in-memory, libSQL, and (under --features postgres + a DB
URL) Postgres. Each backend's per-step output — returned count/sum, error
variant, running evictions_observed() — is captured into an ObservationLog,
and the matrix asserts every backend reproduces the in-memory reference log
exactly. A divergence surfaces as a concrete assert_eq! diff naming the
diverging step.

Three scripts:

• core: counts, sums (incl. fractional 1.25 to catch truncation), window
  trim, exact-cutoff retain (< cutoff), per-key replay dedup, tenant
  isolation, cross-map dedup isolation.
• cap: fill to MAX_SAMPLES_PER_KEY (4096), assert next distinct id
  fails closed with WindowOverflow, replay at the cap is a dedup no-op.
• lru: per-tenant quota flood — same eviction victim + same
  evictions_observed() across backends.

Multi-host adversarial (tests/multi_host_adversarial.rs, --features integration)

The cross-host correctness properties only the durable backends provide:

1. N concurrent writers / 2 hosts — no count/sum desync, exactly-once.
2. Cross-host replay — exactly-once counting (SQL PRIMARY KEY dedups across hosts).
3. LRU eviction race — concurrent inserts past MAX_KEYS_PER_TENANT hold the quota.
4. Per-key cap under attacker flood — fail-closed WindowOverflow, bounded.
5. Clock-skew — two hosts pass different DateTime<Utc>; window follows the
   caller-supplied clock basis (both durable backends chose caller now).

A3 deferral — CLOSED

This closes threat-model finding A3 (multi-host replay bypass) from #3635:
the durable backends' SQL uniqueness constraint makes a cross-host replay a
no-op, so exactly-once counting holds across every host pointing at one
database. Verified by the cross_host_replay_exactly_once scenario.
Documented in crates/ironclaw_hooks/docs/successors/03-persistent-counter.md,
which now also records the final landed trait/clock/fail-closed/LRU shape.

Behavioral findings

No discrepancies found — in-memory and libSQL produce byte-identical parity
logs across all three scripts. One intended divergence is documented and
deliberately not exercised by the matrix: the in-memory backend has a global
MAX_HISTORY_KEYS (8192) cap that the durable backends do not (a DB has no
fixed key ceiling; it's reaped via evict_older_than). All three share the
per-tenant MAX_KEYS_PER_TENANT quota, which is what the lru script asserts.

Test legs executed in this environment

No real Postgres was available, so:

• Ran (green): in-memory + libSQL parity matrix (3 tests), libSQL
  multi-host adversarial (5 tests), Postgres legs skip-pass (4 tests). Plus
  regression: full ironclaw_hooks_libsql suite (16), ironclaw_hooks
  in-memory unit tests (258), ironclaw_hooks_postgres contract (env-skip).
• Compiled + skip-passed (NOT exercised): the Postgres parity + multi-host
  legs. The parity guarantee is not fully exercised for Postgres without a
  real DB — a real-Postgres CI run (IRONCLAW_HOOKS_POSTGRES_URL /
  DATABASE_URL set) is required before merge (same caveat as feat(hooks): PostgresPredicateStateBackend (durable backend PR 2/4, replaces #3932) #3933).

Verification: cargo fmt --all, cargo clippy -p ironclaw_hooks -p ironclaw_hooks_postgres -p ironclaw_hooks_libsql -p ironclaw_hooks_parity --benches --tests --examples --all-features -- -D warnings (clean).

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Evict keys by oldest front timestamp, not newest activity

The eviction query ranks victims by MAX(ts) (ORDER BY last_ts ASC), which picks the key whose most recent sample is oldest. The in-memory and libSQL backends evict by the oldest retained sample (min/front timestamp), so a key with an old front but a recent write can survive in Postgres while being evicted elsewhere. When quotas are hit, this changes which key is dropped and can produce different predicate outcomes across backends for the same event sequence.

Useful? React with 👍 / 👎.

[zmanian]

Already fixed (commit 0c102a6). The scope-LRU eviction ranks victims by MIN(occurred_at) (oldest retained sample / front), ORDER BY oldest_ts ASC — not MAX(ts) — matching the in-memory backend's entries.front() + min_by_key and the libSQL backend. Confirmed: no MAX(ts) eviction remains in the Postgres backend, and the multi-sample LRU parity test exercises it.

[chatgpt-codex-connector]

Enforce global key cap across tenants in Postgres backend

This quota check only enforces MAX_KEYS_PER_TENANT within one scope_hash (tenant) and never applies the map-wide MAX_HISTORY_KEYS cap that the in-memory and libSQL implementations enforce. With many tenants each under their per-tenant cap, Postgres can retain far more keys than the contract expects, causing cross-backend divergence and unbounded growth until a separate reaper runs.

Useful? React with 👍 / 👎.

[zmanian]

Resolved as a deliberate design decision rather than adding the cap to Postgres: the global MAX_HISTORY_KEYS cap is an in-memory-only memory-footprint bound (threat-model D5). Durable backends are disk-backed, not memory-bound, so they intentionally do NOT enforce it inline — they reap via time-based evict_older_than plus the per-tenant MAX_KEYS_PER_TENANT quota. libSQL was aligned to Postgres (its earlier global-cap enforcement was removed) so the two durable backends match; the divergence is now in-memory-vs-durable by design, documented at ironclaw_hooks_libsql backend.rs and predicate_state.rs.

[gemini-code-assist]

Code Review

This pull request introduces durable database-backed implementations for the PredicateStateBackend trait, adding the ironclaw_hooks_libsql and ironclaw_hooks_postgres crates along with a comprehensive parity testing suite. Feedback identifies a logic error in the Postgres window cutoff calculation that could lead to incorrect entry trimming for large windows. Additionally, improvements are suggested for database index coverage to optimize LRU eviction performance, the use of more idiomatic libSQL execution methods, and the standardization of length prefixes to u64 for binary encodings.

[gemini-code-assist]

The current cutoff logic is incorrect for extremely large windows that cause an underflow when subtracted from now. If chrono::Duration::from_std fails or checked_sub_signed returns None, the function currently returns now, which would cause the backend to trim all past entries. For a conservative rate/value cap, a large window should result in a cutoff far in the past so that nothing is trimmed.

Suggested change

	fn cutoff(now: DateTime<Utc>, window: Duration) -> DateTime<Utc> {
	match chrono::Duration::from_std(window) {
	Ok(d) => now.checked_sub_signed(d).unwrap_or(now),
	Err(_) => now,
	}
	}
	fn cutoff(now: DateTime<Utc>, window: Duration) -> DateTime<Utc> {
	let d = chrono::Duration::from_std(window).ok();
	d.and_then(|d| now.checked_sub_signed(d)).unwrap_or_else(|| {
	// For extremely large windows, return a timestamp far in the past
	// to ensure nothing is trimmed (conservative).
	DateTime::<Utc>::from_timestamp(0, 0).unwrap()
	})
	}

[zmanian]

Fixed in 8bd9419. The Postgres cutoff no longer reimplements the Duration→cutoff math; it delegates to the canonical ironclaw_hooks::predicate_state::window_cutoff (the same function libSQL uses), which saturates to now for windows beyond chrono's range and on checked_sub_signed underflow. Byte-for-byte identical across backends, no drift surface.

[gemini-code-assist]

The PRAGMA busy_timeout statement does not return any rows. Using Connection::execute is more appropriate and idiomatic than Connection::query for this operation. Additionally, consider making the timeout value (5000ms) a named constant to improve maintainability.

        conn.execute("PRAGMA busy_timeout = 5000", ())
            .await
            .map_err(map_err)?;

[zmanian]

PRAGMA busy_timeout = N returns a single row (the applied value), so Connection::query is valid here — execute would discard that row but isn't more correct. The 5000ms is documented inline as the cross-process serialisation knob. Leaving as-is; happy to switch to execute if you'd prefer the idiom, but it's not a correctness issue.

[gemini-code-assist]

Per the general rules for this repository, length prefixes in binary encodings should prefer u64 to ensure conversions from usize are infallible on all supported platforms and to maintain consistency across backend implementations (e.g., the libSQL backend already uses u64).

References

1. Prefer using u64 for length prefixes in binary encodings to ensure that conversions from usize are infallible on all supported platforms, avoiding panics and potential DoS vectors caused by .expect() on overflow.

[zmanian]

Fixed in 8bd9419. The hashing was extracted to the shared ironclaw_hooks::predicate_hash module, which uses an 8-byte big-endian u64 length prefix — infallible from usize, removing the lossy u32::try_from(len).unwrap_or(u32::MAX) saturation. Both backends now delegate to it.

[gemini-code-assist]

The hook_predicate_counters_scope_idx index currently only covers (scope_hash, kind). The enforce_scope_quota logic performs a COUNT(DISTINCT key_hash) and an LRU victim selection using MAX(ts) grouped by key_hash. With up to 8.4M rows per tenant (2048 keys * 4096 samples), these operations will be very slow. Expanding this index to include key_hash and ts would allow for much more efficient index-only scans.

Suggested change

	CREATE INDEX IF NOT EXISTS hook_predicate_counters_scope_idx
	ON hook_predicate_counters (scope_hash, kind);
	-- Per-scope (tenant) distinct-key LRU eviction scans by scope.
	-- Including key_hash and ts allows index-only scans for COUNT(DISTINCT) and LRU victim selection.
	CREATE INDEX IF NOT EXISTS hook_predicate_counters_scope_idx
	ON hook_predicate_counters (scope_hash, kind, key_hash, ts);

[zmanian]

Addressed by the typed-schema redesign (ef93722): the generic single-table-with-kind shape is gone, replaced by two typed tables (hooks_predicate_invocations / hooks_predicate_values). So the original (scope_hash, kind) suggestion is now structural — each table carries its own (scope_hash) index plus (key_hash, occurred_at) for the per-key window aggregate, covering the COUNT(DISTINCT key_hash) WHERE scope_hash quota scan and the MIN(occurred_at) GROUP BY key_hash LRU.

[gemini-code-assist]

The idx_hooks_predicate_invocations_tenant index only covers tenant_id. The enforce_caps and evict_oldest_scope functions perform COUNT(DISTINCT scope_hash) and LRU victim selection across all rows for a tenant. For a large number of samples, this will result in expensive table scans. Expanding the index to include scope_hash and occurred_at would significantly improve performance.

Suggested change

	CREATE INDEX IF NOT EXISTS idx_hooks_predicate_invocations_tenant
	ON hooks_predicate_invocations (tenant_id);
	CREATE INDEX IF NOT EXISTS idx_hooks_predicate_invocations_tenant
	ON hooks_predicate_invocations (tenant_id, scope_hash, occurred_at);

[zmanian]

Same as the Postgres sibling: the libSQL schema was canonicalized to typed two-table columns with the matching .sql migration (235a205), so per-table scope_hash / (key_hash, occurred_at) coverage replaces the old single tenant_id index the comment referenced.

[zmanian]

@henrypark133 @serrrfirat durable backend PR 4/4 — cross-backend parity suite (ironclaw_hooks_parity, test-only crate). Feeds one deterministic sequence to all three backends and asserts byte-identical outputs (count/sum/error-variant/eviction/LRU victim) + multi-host adversarial suite. No cross-backend discrepancy found (in-memory ↔ libSQL byte-identical). Closes the A3 multi-host-replay-bypass deferral from #3635. One intended divergence documented + worth your eye: in-memory has a global MAX_HISTORY_KEYS cap, durable backends reap via evict_older_than instead (all share the per-tenant quota) — is the global cap a real defense the durable backends now lack, or redundant given per-tenant quota? Postgres legs skip-passed (no real PG in env). Merge after #3933 + #3936.

[serrrfirat]

Strict maintainability/code-quality pass: I would not merge this as-is.

1. libSQL violates the documented durable-backend model.

crates/ironclaw_hooks/docs/successors/03-persistent-counter.md says the in-memory backend alone has the global MAX_HISTORY_KEYS ceiling and durable backends do not. But crates/ironclaw_hooks_libsql/src/backend.rs still imports and enforces MAX_HISTORY_KEYS, including global cross-tenant eviction in enforce_caps. That is not just docs drift; it makes libSQL and Postgres production semantics diverge while the parity matrix deliberately stays below this path. Please either remove the libSQL global cap or make it an explicit durable-backend contract and test it across both SQL backends.

2. Postgres LRU victim selection does not match in-memory/libSQL.

The in-memory backend evicts by the oldest retained/front sample. libSQL mirrors that with min(occurred_at). Postgres ranks victims by MAX(ts) even though the surrounding comments say it matches oldest-front semantics. The current parity LRU script inserts only one sample per key, so MIN == MAX and this semantic divergence is invisible. Please define the victim rule once and add a multi-sample LRU parity case that would fail if one backend uses oldest-front and another uses newest/last activity.

3. Postgres setup failures are converted into skip-pass tests.

The parity Postgres factory returns Option and uses .ok()? for connect, schema creation, pool build, migration, and truncate. assert_parity() then treats None as “DB URL not set.” That means CI with a configured DB can silently skip Postgres parity if migrations or setup fail. The multi-host harness has the same shape. Missing env should skip; setup errors after env discovery should fail loudly, e.g. with Result<Option<_>, _> or a small setup enum.

4. The multi-host harness structure already let a promised Postgres scenario disappear.

The multi-host suite advertises the LRU eviction race as a durable backend scenario, but the Postgres driver block only wires concurrent writes, replay, cap overflow, and clock skew. The LRU race runs only for libSQL. This is the maintainability smell from hand-wired backend-specific test drivers. A cleaner shape is a shared scenario list plus per-backend cluster adapters so every backend runs every scenario unless explicitly marked unsupported.

The code is close in spirit, but the current structure makes backend parity too easy to claim while important branches remain untested or semantically divergent.

[zmanian]

Codex review (advisory) — REQUEST CHANGES

The parity matrix is a useful differential test, but it overclaims and has gaps.

Critical

1. Not enforced by CI — the workflow's cargo test runs only the root package; no cargo test -p ironclaw_hooks_parity job. A test-only PR whose whole proof is absent from required checks. Add a dedicated job (+ a real-PG integration leg).
2. libSQL still enforces a global key cap; Postgres does not (parity_matrix.rs:453, ironclaw_hooks_libsql/src/backend.rs:427). The matrix excludes this divergence — so libSQL and Postgres can genuinely diverge for >8192 total scopes spread across tenants below the per-tenant cap, and the suite passes anyway. Resolve the backends, don't hide it: the documented durable behavior is reap-via-evict_older_than + per-tenant quota (no global cap), so libSQL should drop its global cap to match Postgres. Then the matrix can assert global-cap parity instead of excluding it. (Fix coordinated on the libSQL branch.)
3. Concurrent writer test discards returned counts (multi_host_adversarial.rs:177) — only checks a final duplicate-id read. A backend could insert all rows but return stale counts mid-race, which is exactly what the evaluator gates on. Collect returned counts and assert 1..=N distinct.
4. Cap-boundary race untested (:266) — fills to cap serially then races only overflow calls. Doesn't test the dangerous boundary: two hosts both observe cap-1 and both try a fresh id. Fill to cap-1, race two fresh ids, assert exactly one succeeds and the other fails closed.
5. PG skip-pass = false confidence (:647, :504) — add IRONCLAW_REQUIRE_POSTGRES=1 for CI to turn missing PG into a hard failure.

Recommendation

In-memory is a reference impl, not an independent oracle — two backends sharing a semantic bug pass. Add explicit expected-observation assertions for the core/cap/LRU scripts, or soften the "proof" wording. Also: the suite tests the backend trait directly, not the evaluator/caller path — doesn't fully satisfy "test through the caller" for actual predicate decisions.

[zmanian]

Addressed the test-quality REQUEST CHANGES (codex)

Re-merged the updated durable backend branches first (libSQL global-cap removal d61ec536b, Postgres LRU advisory-lock fix 806eacbb9) so the matrix runs against the current backends, then closed every flagged gap. Final SHA 17343e6a6.

1. CI enforcement — added a dedicated hooks-parity-tests job to .github/workflows/test.yml (modeled on the existing credential-store-postgres-tests job): runs cargo test -p ironclaw_hooks_parity --features postgres,integration against a pgvector/pgvector:pg16 service with IRONCLAW_REQUIRE_POSTGRES=1, and is wired into the run-tests roll-up's require_success gate. The crate is no longer invisible to CI.

2. Global-cap parity (no longer excluded) — since libSQL dropped its global cap to match Postgres (Postgres only ever had the per-tenant quota), I added parity_global_cap_script: many tenants each record a handful of scopes, exercising the under-quota branch that consults the in-memory global cap, and asserts all three backends AGREE (zero global evictions) in the regime below MAX_HISTORY_KEYS. The only remaining divergence is above 8192 total scopes, which stays documented in 03-persistent-counter.md as an intentional in-memory memory-bound difference (inserting 8192+ scopes through a per-op-connection durable backend is too slow for a unit test; the per-backend no_global_key_cap_only_per_tenant cases cover the durable side directly). The matrix now asserts what is actually uniform instead of silently skipping the dimension.

3. Concurrent-writer returned counts — scenario_concurrent_writers_no_desync now collects every spawned writer's returned count and asserts they form exactly 1..=N (no duplicate/stale counts mid-race), not just the final row count — catching a backend that inserts all rows but returns a stale snapshot count.

4. Cap-boundary race — new scenario_cap_boundary_race_admits_exactly_one: fills to MAX_SAMPLES_PER_KEY - 1, then races two fresh distinct ids from two hosts; asserts exactly one wins the last slot (count == cap) and the other fails closed with WindowOverflow (no TOCTOU breach, no double-reject). Driven for both libSQL and Postgres.

5. PG skip-pass false confidence — IRONCLAW_REQUIRE_POSTGRES=1 turns a missing/unreachable Postgres into a HARD failure in both the matrix and the multi-host suite; local runs without it still skip cleanly. Verified: with the env set and no DB, the matrix legs FAIL rather than green-skip.

6. Oracle independence — each parity script now carries an independent, hand-computed expected_* observation log; every backend (including the in-memory reference) is asserted against it, so two backends sharing a semantic bug can no longer both pass. The oracle immediately earned its keep: it caught a hand-computation error of mine (re-inserting the evicted LRU victim triggers a 9th per-tenant eviction, not 8).

Also serialized the matrix's libSQL legs behind a process-global async mutex, because concurrent independent libSQL Database handles doing heavy 4096-step fills intermittently trip SQLITE_MISUSE under parallel test threads — the same driver limit the per-backend libSQL suite handles via harness=false.

Note on the two earlier inline P1 comments on ironclaw_hooks_postgres/src/backend.rs

• "Enforce global key cap across tenants in Postgres backend" is now intentionally WONTFIX: the agreed direction is durable backends enforce per-tenant quota only (libSQL dropped its global cap in d61ec536b to match), with the global cap an in-memory memory-bound concern. parity_global_cap_script asserts the backends agree under that contract.
• "Evict keys by oldest front timestamp" is addressed by the merged 806eacbb9 LRU eviction fix.

Verification

• cargo fmt --all -- --check: clean
• cargo clippy -p ironclaw_hooks_parity -p ironclaw_hooks_libsql -p ironclaw_hooks_postgres --tests --all-features -- -D warnings: clean
• cargo test -p ironclaw_hooks_parity (in-memory + libSQL): 4/4 pass
• cargo test -p ironclaw_hooks_parity --features integration --test multi_host_adversarial (libSQL multi-host incl. new boundary race): 6/6 pass, stable over 3 runs
• cargo test -p ironclaw_hooks_libsql / -p ironclaw_hooks_postgres --features postgres: pass
• Postgres legs skip-passed locally (no server); the new CI job runs them against a real Postgres with the hard-gate on.

[zmanian]

@henrypark133 @serrrfirat re-review please — all 4 maintainability items + the codex test-quality gaps addressed (SHA 17343e6): added a hooks-parity CI job with a real Postgres service + IRONCLAW_REQUIRE_POSTGRES=1 hard-gate (setup failures fail loudly, only missing env skips); concurrent-writer counts now asserted 1..=N; cap-boundary race added (fill to cap-1, race two ids, one wins one fails closed); oracle-checked expected logs per script (caught a real hand-comp error); global-cap parity asserted not excluded. libSQL global cap removed at source; Postgres MIN-victim fix landed. A multi-sample LRU case is being finalized in the typed-columns redesign that owns this branch.

[henrypark133]

Review of #3937: cross-backend adversarial parity suite

Test-only crate (ironclaw_hooks_parity). No production code changes. No critical bugs found.

Low — Postgres tests gated behind --features postgres + env var: easy to skip in CI without noticing

.github/workflows/test.yml — the Postgres parity tests only run when both --features postgres is set AND a DB URL env var is present. If CI is misconfigured or the Postgres service is unavailable, the tests are silently skipped rather than failing. The parity matrix is the load-bearing cross-backend correctness proof; a skipped run provides zero assurance.

Fix: Add a CI step that fails if the Postgres service is unavailable, or gate the workflow job on a service health check so a missing DB is a CI failure, not a silent skip.

[serrrfirat]

Code Review — #3937

PR: test(hooks): cross-backend adversarial parity suite + A3 closeout (durable backend PR 4/4)

Summary

Category	Findings
🔴 Critical/High	0
🟡 Medium	3
🟢 Low	3
ℹ️ Nit	0

Reviewers: security ✅ · bugs ✅ · performance ✅ · tests ✅ · conventions ✅

---

🟡 Medium — Performance

[f-perf-1 + f-perf-2] Both the libSQL and Postgres migration files create a scope_hash-only index for the per-tenant LRU quota path. The quota enforcement query SELECT count(DISTINCT key_hash) FROM {table} WHERE scope_hash = ?1 and the victim-selection GROUP BY key_hash ORDER BY min(occurred_at) both require scanning every row for the tenant to compute their result — O(total rows for tenant) per new-key insert. A composite (scope_hash, key_hash) index would allow an index-only scan for the distinct-key count (O(distinct keys)), dramatically reducing cost for high-churn tenants at or near MAX_KEYS_PER_TENANT.

[f-tests-1] evict_older_than is a public trait method but is absent from predicate_backend_contract_cases! and the parity matrix. A backend that implements evict_older_than with wrong cutoff semantics (e.g., <= vs <) would pass all current tests. See inline comment on the contract cases macro.

---

🟢 Low — Bugs / Tests

[f-bugs-1] enforce_caps counts DISTINCT key_hash WHERE scope_hash = ? across all rows, including rows from other keys whose windows have expired but were never reaped by evict_older_than. A tenant whose keys all expired (but rows linger) still appears at MAX_KEYS_PER_TENANT, triggering LRU evictions of already-expired keys. The evicted keys are harmless victims, so this is not a correctness failure — but it's an undocumented divergence from the in-memory backend's behavior and produces surprising evictions_observed() metrics without a periodic reaper.

[f-tests-2] The parity matrix lru and multisample-lru scripts only cover record_invocation. enforce_caps is called from both record_invocation and record_value paths; a regression in the value-table branch would go undetected.

[f-tests-3] parity_fail_closed_cap_script fills MAX_SAMPLES_PER_KEY (4 096) entries to a fresh libSQL Database handle. The parity matrix runs under the default libtest harness with no serialization guard. The libSQL contract suite documents that concurrent independent handles on heavy fills trigger SQLITE_MISUSE — which is why that suite uses harness = false. Only one parity test is cap-heavy today, so the risk is low, but worth noting for future scripts.

[serrrfirat]

[f-tests-1] Medium — evict_older_than missing from contract inventory

predicate_backend_contract_cases! drives every backend's contract suite, but evict_older_than (a public trait method) is absent. A backend that evicts with <= instead of < on the cutoff, or that touches only one table, would pass all current tests.

Suggested additions:

$emit!([$($ctx)*] evict_older_than_reaps_strictly_older_rows);
$emit!([$($ctx)*] evict_older_than_retains_entry_at_exact_cutoff);

With corresponding pub async fns in the contract module that verify: rows strictly before the cutoff are deleted, the row exactly AT the cutoff is retained, and the count returned equals rows deleted.

[zmanian]

Confirmed: predicate_backend_contract_cases! enumerates 9 cases (predicate_state.rs:1228-1238) and evict_older_than is not among them. There is an in-memory unit test (evict_older_than_drops_expired_entries_and_empty_buckets, predicate_state.rs:1545), but it lives in the in-memory mod tests and never runs against the durable overrides (ironclaw_hooks_libsql/src/backend.rs:720, ironclaw_hooks_postgres/src/backend.rs), so the <=-vs-< cutoff and single-table-only failure modes are uncovered cross-backend. Will fix: add evict_older_than_reaps_strictly_older_rows and evict_older_than_retains_entry_at_exact_cutoff to the canonical inventory, asserting strictly-older rows are deleted, the exact-cutoff row is retained, both tables are reaped, and the returned count equals rows deleted.

[zmanian]

Fixed in 295b415: added evict_older_than_reaps_strictly_older_rows and evict_older_than_retains_entry_at_exact_cutoff to the canonical predicate_backend_contract_cases! inventory in predicate_state.rs. They assert strictly-older rows are reaped from BOTH the invocation and value tables, the row exactly at the cutoff is retained (< vs <=), and the returned count equals rows deleted. The cases auto-run for in-memory and libSQL via the canonical macro; I also added them to the hand-maintained Postgres pg_contract! list so the durable backends are covered.

[zmanian]

Fixed in 295b415. Added the two contract cases evict_older_than_reaps_strictly_older_rows and evict_older_than_retains_entry_at_exact_cutoff to the canonical predicate_backend_contract_cases! macro (auto-runs for in-memory + libSQL) plus the hand-maintained pg_contract! list. They pin the documented < (not <=) semantics: rows strictly before the cutoff are reaped from BOTH the invocation and value tables, the row exactly at the cutoff is retained, and the returned count equals rows deleted. All pass against in-memory and libSQL; Postgres runs the same cases under a live DB.

[serrrfirat]

[f-perf-1] Medium — Missing (scope_hash, key_hash) composite index

The quota enforcement query:

SELECT count(DISTINCT key_hash) FROM hooks_predicate_invocations WHERE scope_hash = ?1

and the LRU victim selection:

SELECT key_hash FROM ... WHERE scope_hash = ?1 GROUP BY key_hash ORDER BY min(occurred_at)

both scan every row for the tenant. The single-column scope_hash index finds the partition but cannot satisfy the DISTINCT or GROUP BY without fetching each row.

A composite (scope_hash, key_hash) index allows SQLite to answer the distinct-key count via an index-only scan. For a tenant at MAX_KEYS_PER_TENANT (2 048) with many samples per key, the current path is O(total rows for tenant) per new-key insert.

CREATE INDEX IF NOT EXISTS idx_hooks_predicate_invocations_scope_key
    ON hooks_predicate_invocations (scope_hash, key_hash);
CREATE INDEX IF NOT EXISTS idx_hooks_predicate_values_scope_key
    ON hooks_predicate_values (scope_hash, key_hash);

[zmanian]

Confirmed against the schema at head (V1__predicate_state.sql:54-58): only idx_hooks_predicate_invocations_scope ON (scope_hash) and idx_hooks_predicate_values_scope exist, both single-column. enforce_caps runs COUNT(DISTINCT key_hash) WHERE scope_hash = ?1 and evict_oldest_key runs ... WHERE scope_hash = ?1 GROUP BY key_hash ORDER BY min(occurred_at) (backend.rs:617,640), neither of which the single-column index can satisfy index-only. Will fix: add the (scope_hash, key_hash) composite indexes to both tables in this migration. This PR introduces the migration, so the index belongs here, not a follow-up.

[zmanian]

The (scope_hash, key_hash) composite indexes land in the owning backend PR #3936 (which introduces this libSQL migration), not here, to avoid stacked-branch merge conflicts with the migration file. This PR (4/4) only adds the parity/contract suite.

[zmanian]

Fixed in ef4d96a. Added idx_hooks_predicate_invocations_scope_key and idx_hooks_predicate_values_scope_key on (scope_hash, key_hash) to the libSQL V1 schema so the count(DISTINCT key_hash) WHERE scope_hash = ? quota count and the GROUP BY key_hash ORDER BY min(occurred_at) victim scan stay off a full per-tenant row scan. The same indexes are being added to the owning PR #3933; the duplicate copy here will dedupe on rebase once that merges.

[serrrfirat]

[f-perf-2] Medium — Same composite index gap in Postgres schema

Same COUNT(DISTINCT key_hash) WHERE scope_hash = ? and victim-selection queries run in the Postgres backend. The hooks_predicate_invocations_scope_idx ON (scope_hash) alone doesn't enable an index-only scan for distinct key counts.

CREATE INDEX IF NOT EXISTS hooks_predicate_invocations_scope_key_idx
    ON hooks_predicate_invocations (scope_hash, key_hash);
CREATE INDEX IF NOT EXISTS hooks_predicate_values_scope_key_idx
    ON hooks_predicate_values (scope_hash, key_hash);

[zmanian]

Same gap in the Postgres schema at head (V1__predicate_state.sql:60-66): hooks_predicate_invocations_scope_idx ON (scope_hash) only, with the identical COUNT(DISTINCT key_hash) / victim-selection queries in ironclaw_hooks_postgres/src/backend.rs. Will fix: add the (scope_hash, key_hash) composite indexes to both Postgres tables in this migration alongside the libSQL change in f-perf-1.

[zmanian]

On inspection the Postgres schema at #3933's head already carries wider covering indexes — (scope_hash, key_hash, occurred_at) on both the invocations and values tables (added in 7547ebf), which serve the COUNT(DISTINCT key_hash) quota query and LRU victim selection as index-only scans. The proposed bare (scope_hash, key_hash) would be a redundant left-prefix, so no change was needed there. The libSQL twin did lack the index and gained it in #3936 (a06caee).

[zmanian]

Fixed in ef4d96a. Added hooks_predicate_invocations_scope_key_idx and hooks_predicate_values_scope_key_idx on (scope_hash, key_hash) to the Postgres V1 schema, matching the libSQL sibling, so the COUNT(DISTINCT key_hash) WHERE scope_hash = ? and victim-selection queries are covered by a composite rather than the scope-only index. The same indexes are being added to the owning PR #3936; the duplicate copy here will dedupe on rebase once that merges.

[serrrfirat]

[f-bugs-1] Low — Quota count includes un-reaped expired rows from other keys

Step 1 trims only the current key (WHERE key_hash = ?1). This COUNT(DISTINCT key_hash) counts ALL rows for the tenant scope, including rows from OTHER keys whose windows have expired but whose rows haven't been reaped by evict_older_than. A tenant with many expired keys (never reaped) can appear at MAX_KEYS_PER_TENANT and trigger LRU eviction even when its active key count is much lower. The evicted keys are already expired (benign), but the evictions_observed() counter advances unexpectedly.

This is an undocumented behavioral divergence from the in-memory backend (which also doesn't proactively clean expired keys, but those are process-local and bounded by MAX_HISTORY_KEYS). Suggest adding to 03-persistent-counter.md:

The per-tenant quota count includes all stored rows for the tenant, including expired rows from keys not yet reaped by evict_older_than. Deployers must schedule a periodic reaper to keep quota counts accurate; without it, the effective quota for tenants with short-window workloads may appear higher than their active key count.

[zmanian]

Confirmed: the per-key window trim runs WHERE key_hash = ?1 while the quota count is COUNT(DISTINCT key_hash) WHERE scope_hash = ?1 over all stored rows (backend.rs enforce_caps), so expired-but-unreaped rows from other keys do inflate the distinct-key count and can trip LRU eviction (and advance evictions_observed()) below the active-key count. The evicted keys are already expired so gate correctness is unaffected, but the counter divergence from the in-memory backend is undocumented. Will fix: document this in 03-persistent-counter.md — the per-tenant quota counts all stored rows including un-reaped expired keys, so deployers must schedule a periodic evict_older_than reaper to keep quota counts aligned with active key count for short-window workloads.

[zmanian]

Fixed in 295b415 (documentation, no behavior change): documented that the per-tenant quota's COUNT(DISTINCT key_hash) counts all stored rows including expired-but-unreaped rows from other keys, so deployers must schedule a periodic evict_older_than reaper to keep quota counts aligned with the active key count. Added the note at the PredicateStateBackend::evict_older_than trait method, at both backends' quota-enforcement sites (libSQL enforce_caps, Postgres enforce_scope_quota), and in 03-persistent-counter.md.

[zmanian]

Addressed on this branch (HEAD 4b2910e), documentation only — no behavior change. The expired-but-unreaped-rows quota divergence is now documented at the evict_older_than trait method, both backends quota-enforcement sites, and docs/successors/03-persistent-counter.md: the per-tenant COUNT(DISTINCT key_hash) counts all stored rows for the scope including expired rows from idle keys, so deployers must schedule a periodic evict_older_than reaper to keep quota counts aligned with the active key count.

[serrrfirat]

[f-tests-2] Low — record_value LRU path not exercised in parity matrix

All LRU parity scripts (run_lru_script, run_multisample_lru_script) drive record_invocation only. enforce_caps is called from both the invocation and value paths in both backends. A regression in enforce_caps that only surfaces through record_value (e.g., wrong table constant) would not be caught.

Suggested: add a run_lru_value_script (or extend run_lru_script) that exercises per-tenant LRU eviction through record_value and cross-asserts the same oracle log.

[zmanian]

Confirmed: both run_lru_script and run_multisample_lru_script drive only record_invocation (scripts.rs:316,473), so the enforce_caps call on the value path (shared helper, table-parameterized) never exercises per-tenant LRU through record_value in the matrix — a wrong-table-constant regression on that path would slip the oracle. Will fix: add a record_value-driven LRU parity script cross-asserting the same oracle log.

[zmanian]

Fixed in 295b415: added run_lru_value_script + expected_lru_value_log + the parity_per_tenant_lru_value_script test. It mirrors run_lru_script but drives per-tenant LRU eviction through record_value, cross-asserting the same eviction trajectory against the oracle. A value-path-only enforce_caps regression (e.g. wrong table constant) now fails the matrix.

[zmanian]

Fixed on this branch (HEAD 4b2910e). Added run_lru_value_script + expected_lru_value_log and the parity_per_tenant_lru_value_script test, which drives per-tenant LRU through record_value and cross-asserts the same eviction trajectory as the invocation path against an independent oracle. A value-path-only enforce_caps regression (e.g. wrong table constant) is now caught. Verified passing locally (parity_per_tenant_lru_value_script ... ok).

[serrrfirat]

[f-tests-3] Low — Cap-fill parity test runs without a SQLITE_MISUSE serialization guard

parity_fail_closed_cap_script fills MAX_SAMPLES_PER_KEY (4 096) entries through a fresh libSQL Database handle. All parity matrix tests run under the default libtest harness concurrently. The libSQL contract suite documents that concurrent independent Database handles on heavy fills can trigger SQLITE_MISUSE — which is why that suite uses harness = false and a serial runner.

Only one parity test is cap-heavy today, so the risk is lower than in the contract suite. But if future parity scripts add more heavy fills, the same intermittent failure will appear. Consider either:

• Adding the singleton libsql_serial_guard() pattern (as in multi_host_adversarial.rs) to assert_parity's libSQL leg when running the cap script, or
• A brief note in the module doc explaining why the current parallelism is safe.

[zmanian]

This is already in place at head. assert_parity acquires libsql_serial_guard().lock().await and holds it across the entire libSQL leg (parity_matrix/support.rs:383), with the guard defined at support.rs:281 and the rationale documented inline at support.rs:373-382 (same SQLITE_MISUSE concurrent-handles limit, same singleton pattern as multi_host_adversarial.rs:554). Both options you suggested — the serial guard and the explaining module doc — are present, so the cap-fill script (parity_fail_closed_cap_script) and any future heavy fills are already serialized.

[zmanian]

Addressed in 4b2910e (comment only, authored on this branch). Added a caveat at the top of parity_matrix.rs documenting the SQLITE_MISUSE serialization hazard and pointing future cap-heavy / statement-heavy parity script authors at the process-global libsql_serial_guard in support.rs, so an unguarded fresh libSQL handle pushing thousands of rows under the concurrent libtest harness will not intermittently trip SQLITE_MISUSE.

[zmanian]

@serrrfirat The two perf Mediums (composite (scope_hash, key_hash) indexes, both backends) and f-tests-3 are fixed on head 4b2910ea7; f-tests-1/f-tests-2/f-bugs-1 were already addressed on the branch (evict_older_than contract cases, record_value LRU parity script, divergence docs). The May 23 CHANGES_REQUESTED predates all of this — could you approve or dismiss it?

[zmanian]

@henrypark133 This one is ready for your re-review as well — all findings from the June 3 review pass are addressed (see the summary comment above for commits), and your review request is still pending on it.

[henrypark133]

Code Review (multi-agent, re-review)

Intent: Cross-backend adversarial parity suite + A3 closeout (durable backend PR 4/4).

Stats: 4 new findings (1 Medium security, 2 Medium tests, 1 Low) after deduping against 64 prior comments. 8 reviewers run. Diff was truncated at 40 KB for review (full diff 287 KB / 30 files).

Previously raised — author has sound reply, no re-block

• hooks_postgres/hashing.rs lossy u32 length prefix — fixed in 8bd9419e5 (shared module, u64 big-endian).
• hooks_postgres/backend.rs:174 Postgres cutoff math reimplemented — fixed in 8bd9419e5 (delegates to canonical window_cutoff).
• hooks_libsql/src/lib.rs:36 tenant_scope_hash_bytes vs scope_hash_bytes naming — fixed in eb160f313.
• hooks_libsql/src/hashing.rs:19 thin to_vec wrapper — author acknowledged: "thin Vec-adapting delegate" (intentional). Not re-blocking.
• enforce_caps index coverage (gemini bot) — already discussed on the prior backend PRs.
• hooks_postgres/src/backend.rs:523 global key cap across tenants (chatgpt-codex bot) — already addressed in #3933/#3936 review threads.

Note (raised on prior PRs in series)

• Postgres evict_older_than two-DELETE atomicity gap (raised in my #3933 review). Still applies; not re-posting inline here since the file is owned by #3933.

Security

1. Medium PredicateEventId has no length cap; arbitrarily large strings can be stored verbatim in both durable tables (predicate_state.rs:148, conf 75). See inline.

Tests

2. Medium window_cutoff oversized-window Err(_) => now branch not unit-tested (predicate_state.rs:548, conf 75) — the very invariant the function was made pub to enforce. See inline.
3. Medium predicate_hash length-prefix empty-string field handling not tested (predicate_hash.rs:72, conf 75). See inline.

Local patterns

4. Low test_support::scope_hash_bytes return type asymmetric across sibling backends — Vec<u8> vs [u8; 32] (hooks_libsql/src/lib.rs:40, conf 75) — separate from the prior naming fix. See inline.

[henrypark133]

Medium — PredicateEventId::new validates non-empty and NUL-free but applies no length cap. The value is stored verbatim in hooks_predicate_invocations.event_id and hooks_predicate_values.event_id (TEXT, no DB-level length constraint). An attacker who can drive event_id through any path calling record_invocation/record_value can insert arbitrarily large strings — up to PostgreSQLs 1 GiB row limit — into durable storage. With MAX_SAMPLES_PER_KEY = 4096, a single tenant can store 4096 × multi-MB event_ids per key. The WindowOverflow error also embeds the key label in its message, amplifying oversized strings into error-message memory.

Fix: Add a max-length check (e.g. MAX_EVENT_ID_LEN = 512, ~4× a blake3 hex digest) and a PredicateEventIdError::TooLong { len, max } variant.

New finding — not raised in prior reviews.

[henrypark133]

Medium — The Err(_) => now branch fires when chrono::Duration::from_std(window) overflows (a std::time::Duration larger than chrono::Duration::MAX ≈ 9.2e18 ns). The doc explicitly warns that an independent saturating_sub shortcut would diverge here by trimming nothing, whereas this canonical rule trims to now. This is the load-bearing reason window_cutoff was promoted to pub so backends could delegate to it. All existing tests use small Duration::from_secs(N) values; no test exercises the overflow branch. A future refactor to unwrap_or(MIN) would silently regress without failing any test.

Fix: Add window_cutoff_oversized_window_trims_to_now asserting window_cutoff(now, std::time::Duration::MAX) == now.

New finding — not raised in prior reviews.

[henrypark133]

Medium — The length-prefix scheme is explicitly motivated as closing the concatenation-collision hole. Existing tests cover ("ab","c") vs ("a","bc") and ("t","abc") vs ("tabc",""), but never empty-string inputs (scope_hash(""), invocation_key_hash with empty capability, value_key_hash with empty field). An empty-string input writes only the 8-byte zero prefix — a real boundary. A refactor that skips zero-length fields would be undetected by current tests.

Fix: Add scope_hash_empty_tenant_is_stable, invocation_key_hash_empty_capability_is_distinct_from_nonempty, and a value-key variant covering all three public hash functions with empty-string field inputs.

New finding — not raised in prior reviews.

[henrypark133]

Low — After the rename in eb160f313, both crates expose scope_hash_bytes — but libSQL returns Vec<u8> and Postgres returns [u8; 32]. Callers in the parity tests apply .to_vec() on the Postgres side (multi_host_adversarial.rs:683) but not on libSQL, making the supposedly-symmetric accessor asymmetric. Additionally, Postgres exposes invocation_key_hash_bytes; libSQL does not, so any future parity test querying by key hash has no parallel accessor.

Fix: Align both test_support::scope_hash_bytes to return [u8; 32] (the canonical Digest). libSQL can delegate directly to ironclaw_hooks::predicate_hash::scope_hash. Add invocation_key_hash_bytes to libSQL test_support to match the Postgres surface.

New finding — separate from the prior naming fix; not raised in prior reviews.