fix(sync): pre-landing review fixes — monotonic clock seed, scoped CHECK guard

Adversarial (codex) review of the implementation diff caught three:

- P1 (correctness): the fresh-schema setval was not monotonic. initSchema
  replays the schema blob, and the unconditional setval(MAX(generation))
  could move page_generation_clock_seq.last_value BACKWARD on an
  already-upgraded brain, letting a stored query_cache bookmark serve stale
  rows. Seed via GREATEST over the sequence's OWN last_value (+ old table
  value + MAX(generation)) in all 3 fresh schemas and migration v118, so a
  replay is idempotent — mirrors the old table's ON CONFLICT DO NOTHING.
  Pinned by a new monotonic regression test.
- P2: v119's CHECK-exists guard keyed on conname only (not globally unique).
  Scope it to conrelid = 'op_checkpoints'::regclass.
- P3: in-progress note ran into the prior sentence in fail/warn doctor
  messages; separate it with '. '.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/commands/doctor.ts

@@ -3531,7 +3531,7 @@ export async function checkSyncFreshness(
     const details = { unchanged_count, synced_recently_count, stale_count };
     // BUG 4: append in-progress context when any source is actively syncing.
     // Empty otherwise, so steady-state messages are byte-for-byte unchanged.
-    const inProgressNote = inProgress.length ? ` ${inProgress.join('; ')}.` : '';
+    const inProgressNote = inProgress.length ? `. ${inProgress.join('; ')}` : '';
 
     if (hasFailures) {
       return {

src/core/migrate.ts

@@ -5306,6 +5306,7 @@ export const MIGRATIONS: Migration[] = [
 
       SELECT setval('page_generation_clock_seq', GREATEST(
         1,
+        COALESCE((SELECT last_value FROM page_generation_clock_seq), 0),
         COALESCE((SELECT value FROM page_generation_clock WHERE id = 1), 0),
         COALESCE((SELECT MAX(generation) FROM pages), 0)
       ));
@@ -5355,7 +5356,9 @@ export const MIGRATIONS: Migration[] = [
       DO $$
       BEGIN
         IF NOT EXISTS (
-          SELECT 1 FROM pg_constraint WHERE conname = 'op_checkpoints_completed_keys_array'
+          SELECT 1 FROM pg_constraint
+           WHERE conname = 'op_checkpoints_completed_keys_array'
+             AND conrelid = 'op_checkpoints'::regclass
         ) THEN
           ALTER TABLE op_checkpoints
             ADD CONSTRAINT op_checkpoints_completed_keys_array

src/core/pglite-schema.ts

@@ -169,8 +169,15 @@ INSERT INTO page_generation_clock (id, value)
 -- the first write strictly exceeds the seed; floor 1 (sequence MINVALUE).
 -- Layer-1 reads last_value. Table + trigger names retained.
 CREATE SEQUENCE IF NOT EXISTS page_generation_clock_seq;
-SELECT setval('page_generation_clock_seq',
-  GREATEST(1, COALESCE((SELECT MAX(generation) FROM pages), 0)));
+-- Monotonic seed: GREATEST over the sequence's OWN last_value too, so replaying
+-- this blob on an already-upgraded brain (initSchema is re-runnable) can never
+-- move last_value BACKWARD below a stored query_cache bookmark.
+SELECT setval('page_generation_clock_seq', GREATEST(
+  1,
+  COALESCE((SELECT last_value FROM page_generation_clock_seq), 0),
+  COALESCE((SELECT value FROM page_generation_clock WHERE id = 1), 0),
+  COALESCE((SELECT MAX(generation) FROM pages), 0)
+));
 
 CREATE OR REPLACE FUNCTION bump_page_generation_clock_fn() RETURNS trigger AS $func$
 BEGIN

src/core/schema-embedded.ts

@@ -233,8 +233,16 @@ INSERT INTO page_generation_clock (id, value)
 -- first write strictly exceeds the seed; floor 1 (sequence MINVALUE). Layer-1
 -- reads last_value. The table + trigger names are retained.
 CREATE SEQUENCE IF NOT EXISTS page_generation_clock_seq;
-SELECT setval('page_generation_clock_seq',
-  GREATEST(1, COALESCE((SELECT MAX(generation) FROM pages), 0)));
+-- Monotonic seed: GREATEST over the sequence's OWN last_value too, so replaying
+-- this blob on an already-upgraded brain (initSchema is re-runnable) can never
+-- move last_value BACKWARD below a stored query_cache bookmark (which would let
+-- Layer 1 serve stale rows). Mirrors the old table's ON CONFLICT DO NOTHING.
+SELECT setval('page_generation_clock_seq', GREATEST(
+  1,
+  COALESCE((SELECT last_value FROM page_generation_clock_seq), 0),
+  COALESCE((SELECT value FROM page_generation_clock WHERE id = 1), 0),
+  COALESCE((SELECT MAX(generation) FROM pages), 0)
+));
 
 CREATE OR REPLACE FUNCTION bump_page_generation_clock_fn() RETURNS trigger AS \$func\$
 BEGIN

src/schema.sql

@@ -229,8 +229,16 @@ INSERT INTO page_generation_clock (id, value)
 -- first write strictly exceeds the seed; floor 1 (sequence MINVALUE). Layer-1
 -- reads last_value. The table + trigger names are retained.
 CREATE SEQUENCE IF NOT EXISTS page_generation_clock_seq;
-SELECT setval('page_generation_clock_seq',
-  GREATEST(1, COALESCE((SELECT MAX(generation) FROM pages), 0)));
+-- Monotonic seed: GREATEST over the sequence's OWN last_value too, so replaying
+-- this blob on an already-upgraded brain (initSchema is re-runnable) can never
+-- move last_value BACKWARD below a stored query_cache bookmark (which would let
+-- Layer 1 serve stale rows). Mirrors the old table's ON CONFLICT DO NOTHING.
+SELECT setval('page_generation_clock_seq', GREATEST(
+  1,
+  COALESCE((SELECT last_value FROM page_generation_clock_seq), 0),
+  COALESCE((SELECT value FROM page_generation_clock WHERE id = 1), 0),
+  COALESCE((SELECT MAX(generation) FROM pages), 0)
+));
 
 CREATE OR REPLACE FUNCTION bump_page_generation_clock_fn() RETURNS trigger AS $func$
 BEGIN

test/page-generation-counter.test.ts

@@ -295,4 +295,21 @@ describe('v0.42.x sequence-backed clock (BUG 1: contention removal)', () => {
     expect(Number(n3[0].v)).toBe(101);
     await engine.executeRaw(`DROP SEQUENCE test_probe_seq`);
   });
+
+  test('re-seeding is monotonic: the GREATEST guard never moves last_value backward', async () => {
+    // Regression for the codex P1: initSchema replays the schema blob, whose
+    // setval must NOT reset the clock below its current value — a backward move
+    // would let a stored query_cache bookmark serve stale rows. Push the
+    // sequence high, then run the EXACT monotonic seed the blob + v118 use.
+    await engine.executeRaw(`SELECT setval('page_generation_clock_seq', 999999)`);
+    await engine.executeRaw(
+      `SELECT setval('page_generation_clock_seq', GREATEST(
+         1,
+         COALESCE((SELECT last_value FROM page_generation_clock_seq), 0),
+         COALESCE((SELECT value FROM page_generation_clock WHERE id = 1), 0),
+         COALESCE((SELECT MAX(generation) FROM pages), 0)
+       ))`,
+    );
+    expect(await clockValue()).toBeGreaterThanOrEqual(999999);
+  });
 });