diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d9048470..aaf417289 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,34 @@
 # Changelog
 
+## [1.4.38.6] — 2026-05-18 — Boot-backfill discovery SQL fix
+
+The v1.4.38.5 discovery rewrite filtered the LEFT JOIN with
+`WHERE r."id" IS NULL` — but `measurement_rollups` has a composite
+primary key `(user_id, type, granularity, bucket_start)` and no
+surrogate `id` column. Postgres rejected the query with
+`column r.id does not exist` (SQL state 42703), the worker boot
+swallowed the error per the helper's best-effort contract, and the
+queue stayed empty. Net effect: v1.4.38.5 deployed cleanly but
+delivered none of its promised fast-path recovery.
+
+### Fixed
+
+- **Boot-backfill discovery now filters on `r."bucket_start" IS NULL`**
+  — any column from the right side of the LEFT JOIN serves as the
+  "no matching row" sentinel; `bucket_start` is part of the composite
+  primary key so the planner already touches the column. Verified
+  against the live schema: `42703` no longer raised on worker boot,
+  and the discovery query returns the expected per-type-missing
+  candidate set.
+
+### Operator notes
+
+- No new migration. No env-var change.
+- On first boot after deploy the rollup-full-backfill queue picks
+  up users with any missing type-coverage and folds them. Power-
+  user accounts may see one slow `/api/analytics` cold-mount before
+  the next request lands on the restored fast path.
+
 ## [1.4.38.5] — 2026-05-18 — Analytics fast-path restored on long-running accounts
 
 Hotfix on top of v1.4.38.4. `/api/analytics` and the dashboard
diff --git a/package.json b/package.json
index 446fdfdfe..45536d17b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.4.38.5",
+  "version": "1.4.38.6",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "AGPL-3.0-only",
   "homepage": "https://healthlog.dev",
diff --git a/src/lib/measurements/rollups.ts b/src/lib/measurements/rollups.ts
index f704335a9..897ce2f21 100644
--- a/src/lib/measurements/rollups.ts
+++ b/src/lib/measurements/rollups.ts
@@ -736,10 +736,11 @@ export async function enqueueBootTimeRollupBackfill(): Promise<{
     // planner uses the `(user_id, type, measured_at)` index path; the
     // LEFT JOIN onto `measurement_rollups` uses the
     // `(user_id, type, granularity, bucket_start)` composite primary
-    // key. `r."id" IS NULL` filters the unmatched partitions. A user
-    // surfaces here when ANY type is missing — including the brand-
-    // new-type case that v1.4.35.1's zero-rollup-only shape silently
-    // stranded.
+    // key. `measurement_rollups` has no surrogate `id` column —
+    // `r."bucket_start" IS NULL` (any column from the right side of
+    // the LEFT JOIN) marks the unmatched partitions. A user surfaces
+    // here when ANY type is missing — including the brand-new-type
+    // case that v1.4.35.1's zero-rollup-only shape silently stranded.
     const users = await prisma.$queryRaw<Array<{ id: string }>>`
       SELECT DISTINCT mt."user_id" AS id
       FROM (
@@ -750,7 +751,7 @@ export async function enqueueBootTimeRollupBackfill(): Promise<{
         ON  r."user_id"     = mt."user_id"
         AND r."type"        = mt."type"
         AND r."granularity" = 'DAY'
-      WHERE r."id" IS NULL
+      WHERE r."bucket_start" IS NULL
     `;
 
     if (users.length === 0) {