diff --git a/alkstore-mem/src/fuzz_surface_tests.rs b/alkstore-mem/src/fuzz_surface_tests.rs
new file mode 100644
index 0000000..438ebe7
--- /dev/null
+++ b/alkstore-mem/src/fuzz_surface_tests.rs
@@ -0,0 +1,5 @@
+#[test]
+fn doc_hidden_reexports_reach_the_crate_root() {
+    assert_eq!(crate::parse_every_interval("@every 5s").unwrap(), 5);
+    assert_eq!(crate::skip_forward(0, 20, 5), 25);
+}
diff --git a/alkstore-mem/src/lib.rs b/alkstore-mem/src/lib.rs
index 63841ec..93d5ab9 100644
--- a/alkstore-mem/src/lib.rs
+++ b/alkstore-mem/src/lib.rs
@@ -51,4 +51,18 @@ mod tx;
 mod validation;
 mod wakes;
 
+#[cfg(test)]
+mod fuzz_surface_tests;
+
 pub use store::MemStore;
+
+/// Fuzz/test-only surface: the mem engine's `@every` parser — not
+/// contract surface, not consumer API, no stability guarantee.
+#[doc(hidden)]
+pub use scheduler::parse_every_interval;
+
+/// Fuzz/test-only surface: the mem engine's schedule skip-forward
+/// arithmetic — not contract surface, not consumer API, no stability
+/// guarantee.
+#[doc(hidden)]
+pub use scheduler::skip_forward;
diff --git a/alkstore-mem/src/scheduler.rs b/alkstore-mem/src/scheduler.rs
index 7c53a65..c74ffa9 100644
--- a/alkstore-mem/src/scheduler.rs
+++ b/alkstore-mem/src/scheduler.rs
@@ -87,7 +87,7 @@ fn leader_owner() -> String {
 /// parser (third owner per ADR-012 §2; the grammar is small and
 /// pinned). Everything else — 5-field cron, seconds-field cron —
 /// rejects as `InvalidSpec`.
-pub(crate) fn parse_every_interval(spec: &str) -> Result<i64> {
+pub fn parse_every_interval(spec: &str) -> Result<i64> {
     let Some(body) = spec.strip_prefix("@every ") else {
         return Err(invalid_spec(spec));
     };
@@ -251,7 +251,7 @@ fn fire_due(sched: &mut ScheduleState, queues: &mut QueueState, state: &State, n
 /// The bounded catch-up's skip-forward: land the next boundary strictly
 /// in the future, grid-aligned (the schedule row's advance makes the
 /// gap inspectable).
-fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
+pub fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
     let gap = (now - next_fire_at) as i128;
     let interval = interval as i128;
     let next = (next_fire_at as i128) + (gap / interval + 1) * interval;
diff --git a/alkstore-postgres/src/fuzz_surface_tests.rs b/alkstore-postgres/src/fuzz_surface_tests.rs
new file mode 100644
index 0000000..438ebe7
--- /dev/null
+++ b/alkstore-postgres/src/fuzz_surface_tests.rs
@@ -0,0 +1,5 @@
+#[test]
+fn doc_hidden_reexports_reach_the_crate_root() {
+    assert_eq!(crate::parse_every_interval("@every 5s").unwrap(), 5);
+    assert_eq!(crate::skip_forward(0, 20, 5), 25);
+}
diff --git a/alkstore-postgres/src/lib.rs b/alkstore-postgres/src/lib.rs
index 4166395..4048b89 100644
--- a/alkstore-postgres/src/lib.rs
+++ b/alkstore-postgres/src/lib.rs
@@ -48,6 +48,9 @@ mod store;
 mod stream;
 mod tx;
 
+#[cfg(test)]
+mod fuzz_surface_tests;
+
 pub use opts::{DEFAULT_MAX_SIZE, PgOpts};
 pub use schema::{
     BootstrapError, BootstrapResult, DEFAULT_SCHEMA, QualifiedTable, bootstrap, quote_identifier,
@@ -55,3 +58,14 @@ pub use schema::{
 };
 pub use store::{PgStore, open};
 pub use tx::PgTxHandle;
+
+/// Fuzz/test-only surface: the pg engine's `@every` parser — not
+/// contract surface, not consumer API, no stability guarantee.
+#[doc(hidden)]
+pub use scheduler::parse_every_interval;
+
+/// Fuzz/test-only surface: the pg engine's schedule skip-forward
+/// arithmetic — not contract surface, not consumer API, no stability
+/// guarantee.
+#[doc(hidden)]
+pub use scheduler::skip_forward;
diff --git a/alkstore-postgres/src/scheduler.rs b/alkstore-postgres/src/scheduler.rs
index 153d36d..382375f 100644
--- a/alkstore-postgres/src/scheduler.rs
+++ b/alkstore-postgres/src/scheduler.rs
@@ -221,7 +221,7 @@ fn invalid_spec(spec: &str) -> Error {
 /// with `n` a positive integer and unit in `s|m|h|d`. Everything else
 /// (cron strings, bare `every 5s`, floats, unknown units) rejects.
 /// Returns the interval in seconds.
-pub(crate) fn parse_every_interval(spec: &str) -> Result<i64> {
+pub fn parse_every_interval(spec: &str) -> Result<i64> {
     let reject = || invalid_spec(spec);
     let body = spec.strip_prefix("@every ").ok_or_else(reject)?;
     if body.is_empty() {
@@ -261,7 +261,7 @@ fn next_every_boundary(spec: &str, after: i64) -> Result<i64> {
 /// `next + (gap / interval + 1) * interval` — strictly beyond `now`
 /// (the skipped boundaries never enqueue). 128-bit intermediates keep
 /// the arithmetic saturation-safe; the result clamps at `i64::MAX`.
-fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
+pub fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
     let gap = (now - next_fire_at) as i128;
     let interval = interval.max(1) as i128;
     let next = (next_fire_at as i128) + (gap / interval + 1) * interval;
diff --git a/alkstore-sqlite/src/fuzz_surface_tests.rs b/alkstore-sqlite/src/fuzz_surface_tests.rs
new file mode 100644
index 0000000..438ebe7
--- /dev/null
+++ b/alkstore-sqlite/src/fuzz_surface_tests.rs
@@ -0,0 +1,5 @@
+#[test]
+fn doc_hidden_reexports_reach_the_crate_root() {
+    assert_eq!(crate::parse_every_interval("@every 5s").unwrap(), 5);
+    assert_eq!(crate::skip_forward(0, 20, 5), 25);
+}
diff --git a/alkstore-sqlite/src/lib.rs b/alkstore-sqlite/src/lib.rs
index f288ef4..2d26cd4 100644
--- a/alkstore-sqlite/src/lib.rs
+++ b/alkstore-sqlite/src/lib.rs
@@ -36,6 +36,20 @@ mod stream;
 mod substrate;
 mod tx;
 
+#[cfg(test)]
+mod fuzz_surface_tests;
+
 pub use opts::{DEFAULT_MAX_READERS, SqliteOpts};
 pub use store::{SqliteStore, open};
 pub use tx::SqliteTxHandle;
+
+/// Fuzz/test-only surface: the substrate's `@every` parser — not
+/// contract surface, not consumer API, no stability guarantee.
+#[doc(hidden)]
+pub use substrate::parse_every_interval;
+
+/// Fuzz/test-only surface: the substrate's schedule skip-forward
+/// arithmetic — not contract surface, not consumer API, no stability
+/// guarantee.
+#[doc(hidden)]
+pub use substrate::skip_forward;
diff --git a/alkstore-sqlite/src/substrate/PROVENANCE.md b/alkstore-sqlite/src/substrate/PROVENANCE.md
index 4d76f34..c1db409 100644
--- a/alkstore-sqlite/src/substrate/PROVENANCE.md
+++ b/alkstore-sqlite/src/substrate/PROVENANCE.md
@@ -129,6 +129,7 @@ Cherry-picks: empty at scaffold, append-only forever.
 | D-34 | drop | `queue_next_claim_at` cut (the queue's earliest-wake deadline query): upstream exposed it as a `honker_queue_next_claim_at` scalar registration for external poll-loop drivers and its leader loop used it to compute the sleep horizon; this fork's leader loop computes the boundary out of `scheduler_tick` + `scheduler_soonest` inside the tick transaction (the engine's scheduler.rs) and exposes no substrate-side next-wake function — the v1 scheduler surface has no consumer-inventory row for one | `queue_ops.rs` (function + its substrate test `queue_next_claim_at_reports_the_earliest_wake`) | ADR-009 (the v1 scheduler collapse: register/tick/soonest/unregister only — D-21's surface rule; no wake-time query on the v1 surface); ADR-012 §2 (the substrate exposes what the engine calls, and the engine never calls this); wave-3 lint-removal obligation — cut, not suppressed | ours |
 | D-35 | drop | `Writer::try_acquire` cut (the non-blocking writer-slot try): upstream's embedding harness used it for try-shaped entry points its surface exposed; this engine's seam always blocks (`acquire`) — the writer-slot lease is a *parks-the-writer* lease by design (ADR-007's honest model), so a try-shaped acquire would contradict the posture rather than extend it. The probe tests driving it re-express their properties through `acquire`/`release`/`close` (the engine-reachable surface); the engine-level lease tests (`tx_tests`' lease/parking suite) pin the observable posture end-to-end | `schema.rs` (`Writer::try_acquire` + the three `writer_reader_tests` call sites) | ADR-007 (the caller-held-lease seam: `begin_tx` parks a concurrent writer — no try-shaped begin exists on the contract surface); ADR-012 §2 (nothing on the engine side reaches a try-acquire); wave-3 lint-removal obligation — cut, not suppressed | ours |
 | D-36 | drop | `UpdateWatcher::spawn` and `SharedUpdateWatcher::new` cut (the default-cadence convenience constructors): upstream's embedding harnesses opened watchers without explicit config; this engine's single open path always constructs a `WatcherConfig` — from `SqliteOpts` (ADR-023 §4's `poll_interval` knob, `None` = the 1 ms default) — and passes it through `*_with_config`; a config-less twin would re-create two open postures (the mixed-flag inconsistency D-29 resolved at the URI layer). `WatcherConfig::default()` remains the default's single owner; the tests driving the cut constructors now build the config explicitly, pinning the same behavior | `watcher.rs` (both constructors + five watcher-test call sites) | ADR-023 §4 (the cadence knob rides the engine's opts — one open posture carries config); ADR-012 §2 (one construction path the engine reviews); wave-3 lint-removal obligation — cut, not suppressed | ours |
+| D-37 | re-derivation | visibility-only widening on the re-derived `@every` surface: `parse_every_interval` (`pub(crate)` → `pub`) and `skip_forward` (module-private → `pub`) in `queue_ops.rs`, plus this subtree's facade re-export (`mod.rs`: `pub use queue_ops::{parse_every_interval, skip_forward}`), so the engine crate root can `#[doc(hidden)] pub use` both as the wave-7 fuzzing differential target's drive surface (`fuzz-parser-exposure`, target `every_parse`). Zero logic change, zero signature change, zero name change; `mod substrate` stays private, so containment holds — nothing leaves the crate except the doc-hidden root re-exports. A `pub use` re-export mechanically requires item-level `pub` (E0364/E0603), which is why the facade line is in `mod.rs`; the module doc's "nothing re-exported" boundary sentence was amended in the same commit to name this sole exception | `queue_ops.rs` (two visibility keywords); `mod.rs` (facade re-export line + boundary-doc exception sentence) | ADR-012 §3 (fidelity governs the ported honker body — `watcher.rs`/`schema.rs`/`ops.rs` untouched; `queue_ops.rs` is the re-derived half, owned contract-v1 code, so a visibility-only delta is legitimate); docs/research/fuzzing.md §3.2 (option (b): the `#[doc(hidden)]` narrow exposure); ADR-017 §3 (doc-hidden test surface, no stability guarantee — the `Job::from_row` precedent) | ours |
 
 ### Cherry-picks
 
diff --git a/alkstore-sqlite/src/substrate/mod.rs b/alkstore-sqlite/src/substrate/mod.rs
index f4dbb8b..cb8226c 100644
--- a/alkstore-sqlite/src/substrate/mod.rs
+++ b/alkstore-sqlite/src/substrate/mod.rs
@@ -16,9 +16,12 @@
 //! returns primitives; the engine layer above resolves contract
 //! semantics into primitive arguments and maps substrate outcomes into
 //! the contract taxonomy. Nothing here is re-exported through the
-//! engine crate's public API. The fork point, every deliberate
-//! divergence, and any future cherry-pick are recorded in the
-//! provenance register (`PROVENANCE.md`, this directory; ADR-018).
+//! engine crate's public API — the sole exception (register D-37): the
+//! re-derived half's `@every` parser pair (`parse_every_interval`,
+//! `skip_forward`) is re-exported to the engine crate root as a
+//! `#[doc(hidden)]` fuzz/test-only surface. The fork point, every
+//! deliberate divergence, and any future cherry-pick are recorded in
+//! the provenance register (`PROVENANCE.md`, this directory; ADR-018).
 //!
 //! Fidelity posture (ADR-012 §3): where scope *keeps* upstream
 //! machinery, upstream's module structure and internal function names
@@ -59,9 +62,13 @@ pub(crate) use ops::{
 };
 pub(crate) use queue_ops::{
     FireOpts, Stamps, ack, ack_batch, cancel, claim_batch, enqueue, fail, get_job, heartbeat,
-    parse_every_interval, retry, scheduler_register, scheduler_soonest, scheduler_tick,
-    scheduler_unregister, sweep_expired,
+    retry, scheduler_register, scheduler_soonest, scheduler_tick, scheduler_unregister,
+    sweep_expired,
 };
+/// The doc-hidden fuzz/test re-exports' substrate-side facade (the
+/// engine's `lib.rs` republishes these under `#[doc(hidden)]`; register
+/// D-37).
+pub use queue_ops::{parse_every_interval, skip_forward};
 pub(crate) use schema::Error as SchemaError;
 pub(crate) use schema::open_conn_bootstrapped;
 pub(crate) use schema::{Readers, Writer};
diff --git a/alkstore-sqlite/src/substrate/queue_ops.rs b/alkstore-sqlite/src/substrate/queue_ops.rs
index e249784..687c733 100644
--- a/alkstore-sqlite/src/substrate/queue_ops.rs
+++ b/alkstore-sqlite/src/substrate/queue_ops.rs
@@ -487,7 +487,7 @@ fn now_unix(conn: &Connection) -> rusqlite::Result<i64> {
     conn.query_row("SELECT unixepoch()", [], |r| r.get(0))
 }
 
-pub(crate) fn parse_every_interval(spec: &str) -> Result<i64, String> {
+pub fn parse_every_interval(spec: &str) -> Result<i64, String> {
     let body = spec
         .strip_prefix("@every ")
         .ok_or_else(|| format!("unsupported spec {spec:?}; @every <n><unit> only"))?;
@@ -524,7 +524,7 @@ fn next_every_boundary(spec: &str, after: i64) -> Result<i64, String> {
         .ok_or_else(|| format!("next boundary overflows for {spec:?}"))
 }
 
-fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
+pub fn skip_forward(next_fire_at: i64, now: i64, interval: i64) -> i64 {
     let gap = (now - next_fire_at) as i128;
     let interval = interval as i128;
     let next = (next_fire_at as i128) + (gap / interval + 1) * interval;
diff --git a/tasks/fuzz-parser-exposure.md b/tasks/fuzz-parser-exposure.md
index 5954732..83abe2d 100644
--- a/tasks/fuzz-parser-exposure.md
+++ b/tasks/fuzz-parser-exposure.md
@@ -1,7 +1,7 @@
 ---
 id: fuzz-parser-exposure
 name: Parser exposure — `#[doc(hidden)]` narrow surface for the three `@every` parsers + boundary arithmetic
-status: pending
+status: completed
 depends_on: []
 scope: narrow
 risk: low
@@ -73,23 +73,26 @@ differential runs on the exposed functions.
 
 ## Acceptance Criteria
 
-- [ ] All three engines re-export their `parse_every_interval` and
+- [x] All three engines re-export their `parse_every_interval` and
       `skip_forward` from the crate root, `#[doc(hidden)]`, with the
       fuzz/test-only doc note
-- [ ] `alkstore-sqlite/src/substrate/**` diff is **visibility-only**:
+- [x] `alkstore-sqlite/src/substrate/**` diff is **visibility-only**:
       exactly the two keywords in `queue_ops.rs` (`parse_every_interval`
       → `pub`, `skip_forward` → `pub`); the lineage body
-      (`watcher.rs`, `connection.rs`, `ops.rs`, `schema.rs`, `mod.rs`)
-      untouched; a PROVENANCE.md delta entry records the change
-- [ ] pg/mem `scheduler.rs` diffs are visibility-only (two keywords
+      (`watcher.rs`, `connection.rs`, `ops.rs`, `schema.rs`) untouched;
+      a PROVENANCE.md delta entry records the change
+      *(amended at implementation, 2026-10-10 — `mod.rs` was in this
+      list, but a second mechanical constraint forced one facade line
+      there: see Notes. No lineage-body file was touched.)*
+- [x] pg/mem `scheduler.rs` diffs are visibility-only (two keywords
       each: parser → `pub`, `skip_forward` → `pub`) plus nothing else
-- [ ] The re-exports are reachable from an external crate (pinned by a
+- [x] The re-exports are reachable from an external crate (pinned by a
       compile-level test or the `fuzz-target-every-parse` build itself;
       record which)
-- [ ] No behavior change: workspace gates green (`cargo build`,
+- [x] No behavior change: workspace gates green (`cargo build`,
       `cargo test`, clippy `-D warnings`, fmt); the engines' own
       scheduler/parser test suites untouched and green
-- [ ] `cargo check --target wasm32-unknown-unknown -p alkstore-mem`
+- [x] `cargo check --target wasm32-unknown-unknown -p alkstore-mem`
       still clean (visibility widening is wasm-neutral, pinned anyway)
 
 ## References
@@ -112,8 +115,61 @@ differential runs on the exposed functions.
 
 ## Notes
 
-> To be filled by implementation agent
+Decisions of record the implementation made that the description didn't
+pin:
+
+- **Second mechanical amendment — `mod.rs` could not stay untouched.**
+  Widening `queue_ops.rs`'s two functions to `pub` is necessary but not
+  sufficient: `lib.rs` cannot name the path `substrate::queue_ops::…`
+  at all — `mod substrate` is private *to `substrate`'s subtree* for
+  `queue_ops` purposes, so a through-the-path re-export fails E0603,
+  and `skip_forward` had **no `mod.rs` export** whatsoever (it was not
+  in the `pub(crate) use` list). The only route is the facade: `mod.rs`
+  gained `pub use queue_ops::{parse_every_interval, skip_forward};`
+  (one line; `parse_every_interval` moved out of the `pub(crate)` list
+  into it — a duplicate binding would be E0252), compile-probed clean.
+  This remains visibility-only — zero logic, zero signatures, zero
+  names; lineage body (`watcher.rs`/`connection.rs`/`ops.rs`/
+  `schema.rs`) untouched; containment holds (`mod substrate` private).
+- **`mod.rs`'s boundary-doc sentence amended.** "Nothing here is
+  re-exported through the engine crate's public API" would have become
+  stale the moment the facade landed; the sentence now names this sole
+  exception inline, and the full story is registered as **PROVENANCE.md
+  D-37** (category `re-derivation`, per this task's amendment).
+- **Reachability pin (criterion 4): compile-level test.** Each engine
+  gained `src/fuzz_surface_tests.rs` (`#[cfg(test)]`, declared in
+  `lib.rs`) — `doc_hidden_reexports_reach_the_crate_root` drives both
+  re-exports through the crate-root path (one accept case + one
+  `skip_forward` assertion each). Compile of the `pub use` itself is
+  the E0364-class pin; the true external-crate consumption arrives with
+  `fuzz-target-every-parse`'s build (its `shared` crate path-depends on
+  all three engines). Neither engine's existing suite files were
+  touched — the pin is a separate module.
+- **Semver note (recorded per the description):** doc-hidden `pub`
+  items are still public API — removal is technically breaking; the
+  same commitment core's four `#[doc(hidden)]` constructors made,
+  bounded to a fuzz/test purpose.
 
 ## Summary
 
-> To be filled on completion
\ No newline at end of file
+Landed (2026-10-10): the `#[doc(hidden)]` narrow fuzz/test surface for
+the three engines — `parse_every_interval` + `skip_forward` re-exported
+from each crate root with the one-line fuzz/test-only doc note
+(`Job::from_row` doc-posture style).
+
+- **alkstore-sqlite**: `substrate/queue_ops.rs` two keywords widened to
+  `pub`; `substrate/mod.rs` gained the facade `pub use` line + the
+  boundary-doc exception sentence; `substrate/PROVENANCE.md` D-37
+  registered; `lib.rs` `#[doc(hidden)] pub use substrate::…` ×2.
+- **alkstore-postgres / alkstore-mem**: `scheduler.rs` two keywords
+  each widened to `pub`; `lib.rs` `#[doc(hidden)] pub use scheduler::…`
+  ×2. No provenance concern (engine-owned files).
+- **Reachability pins**: `src/fuzz_surface_tests.rs` ×3 — one test per
+  engine driving both crate-root re-exports.
+
+Verified: `cargo build` clean; `cargo test` green (all suites; the
+three new pins pass; no engine suite touched); `cargo clippy
+--all-targets -- -D warnings` clean; `cargo fmt --check` clean;
+`cargo check --target wasm32-unknown-unknown -p alkstore-mem` clean.
+Diff audited against the (twice-amended) criteria: engine
+`scheduler.rs`/`queue_ops.rs` diffs are visibility keywords only.
\ No newline at end of file