diff --git a/CHANGELOG.md b/CHANGELOG.md
index bd9a1a7ee..6c53b6a09 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,23 @@
 
 ## [Unreleased]
 
+## [1.28.46] — 2026-07-16 — Server performance on large instances
+
+Performance work for accounts with a lot of history, none of it changing what
+any number means:
+
+- Insight generation computed its 30-day comparison averages by pulling every
+  matching row of the last 400 days into memory and averaging in code. It now
+  asks the database for the averages directly — the same figures, without
+  materialising the rows. (Sleep keeps its per-night reconstruction path.)
+- The background scans that run at worker startup used an in-memory
+  de-duplication over full-table reads. They now de-duplicate in the database
+  and are backed by partial indexes (migration 0243, additive), so startup on a
+  large instance no longer does full scans.
+- The coach chat re-rendered every message on every streamed token; now only
+  the message being streamed re-renders.
+- The doctor-report mood read no longer pulls fields it doesn't use.
+
 ## [1.28.45] — 2026-07-16 — Doctor report + privacy fixes
 
 - Sleep now actually appears in the doctor-report PDF. The sleep section was
diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index 5b2e5dfaf..54273c02b 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -1,7 +1,7 @@
 openapi: 3.1.0
 info:
   title: HealthLog API
-  version: 1.28.45
+  version: 1.28.46
   description: >-
     Self-hosted personal-health-tracking PWA — public API surface for the iOS native client and external ingest.
 
diff --git a/package.json b/package.json
index 9f9fc92ce..644912f88 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "healthlog",
-  "version": "1.28.45",
+  "version": "1.28.46",
   "description": "Self-hosted personal-health-tracking PWA with Withings integration, AI insights, and doctor-report PDF export.",
   "license": "PolyForm-Noncommercial-1.0.0",
   "homepage": "https://healthlog.dev",
diff --git a/prisma/migrations/0243_perf_boot_discovery_partial_indexes/migration.sql b/prisma/migrations/0243_perf_boot_discovery_partial_indexes/migration.sql
new file mode 100644
index 000000000..f01cf178c
--- /dev/null
+++ b/prisma/migrations/0243_perf_boot_discovery_partial_indexes/migration.sql
@@ -0,0 +1,54 @@
+-- v1.28.46 perf (H4) — partial indexes for the boot-time converging-backfill
+-- discovery scans. Each discovery now runs a DB-level `SELECT DISTINCT user_id`
+-- over a growth table filtered by a "still-un-migrated" predicate; without an
+-- index that is a full filtered-partition scan at worker boot (the boot-storm
+-- class on a heavy tenant). Each index below is PARTIAL on exactly the
+-- discovery predicate, so the scan is index-only and shrinks to nothing as the
+-- one-time backfill converges (a migrated row drops out of the predicate).
+--
+-- Additive-only: every statement is `CREATE INDEX IF NOT EXISTS`, no table
+-- rewrite, no data change. NON-CONCURRENT on purpose — Prisma Migrate wraps a
+-- migration file in a transaction and `CREATE INDEX CONCURRENTLY` cannot run in
+-- one; these build at boot (docker-entrypoint runs `migrate deploy` BEFORE the
+-- app serves traffic), so the brief build lock lands in the pre-traffic window.
+-- Partial predicates match the write-side note convention (partial indexes are
+-- raw-SQL-only here; Prisma cannot express a partial predicate — see the 0087 /
+-- 0108 / 0183 precedents documented in schema.prisma).
+
+-- note-encryption-backfill: measurements (densest table) + mood_entries.
+CREATE INDEX IF NOT EXISTS "measurements_note_backfill_idx"
+  ON "measurements" ("user_id")
+  WHERE "notes" IS NOT NULL AND "notes_encrypted" IS NULL;
+
+CREATE INDEX IF NOT EXISTS "mood_entries_note_backfill_idx"
+  ON "mood_entries" ("user_id")
+  WHERE "note" IS NOT NULL AND "note_encrypted" IS NULL;
+
+-- med-notes-encryption-backfill: side-effects, inventory items, dose-changes.
+-- Dose-changes carry no user_id; the discovery joins to medications on
+-- medication_id, so the partial index leads with that join key.
+CREATE INDEX IF NOT EXISTS "medication_side_effects_note_backfill_idx"
+  ON "medication_side_effects" ("user_id")
+  WHERE "notes" IS NOT NULL AND "notes_encrypted" IS NULL;
+
+CREATE INDEX IF NOT EXISTS "medication_inventory_items_note_backfill_idx"
+  ON "medication_inventory_items" ("user_id")
+  WHERE "notes" IS NOT NULL AND "notes_encrypted" IS NULL;
+
+CREATE INDEX IF NOT EXISTS "medication_dose_changes_note_backfill_idx"
+  ON "medication_dose_changes" ("medication_id")
+  WHERE "note" IS NOT NULL AND "note_encrypted" IS NULL;
+
+-- lab-biomarker-backfill: unlinked live lab results.
+CREATE INDEX IF NOT EXISTS "lab_results_biomarker_backfill_idx"
+  ON "lab_results" ("user_id")
+  WHERE "deleted_at" IS NULL AND "biomarker_id" IS NULL;
+
+-- document-thumbnail-backfill: live thumbnailable documents. The thumbnail
+-- absence lives on the `document_thumbnails` side table (a cross-table
+-- anti-join, not indexable here); this partial index bounds the document-side
+-- scan on `(user_id, mime_type)` for live rows, and the anti-join rides
+-- `document_thumbnails.document_id` (already UNIQUE via the 1:1 relation).
+CREATE INDEX IF NOT EXISTS "inbound_documents_thumbnail_backfill_idx"
+  ON "inbound_documents" ("user_id", "mime_type")
+  WHERE "deleted_at" IS NULL;
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 80848d888..39c642f81 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -1707,6 +1707,11 @@ model Measurement {
   // and series reads for every type NOT covered by the two partials above
   // and removes the `deleted_at` heap re-check. Same Prisma-can't-express-a-
   // partial-predicate reason it is omitted here.
+  // `measurements_note_backfill_idx` is a partial index over `(user_id)
+  // WHERE notes IS NOT NULL AND notes_encrypted IS NULL` — see migration 0243
+  // (v1.28.46 H4). It makes the note-encryption boot-discovery `SELECT DISTINCT
+  // user_id` an index-only scan that converges to empty. Same partial-predicate
+  // reason it is omitted here.
   @@map("measurements")
 }
 
@@ -2719,6 +2724,11 @@ model MedicationDoseChange {
   medication Medication @relation(fields: [medicationId], references: [id], onDelete: Cascade)
 
   @@index([medicationId, effectiveFrom])
+  // `medication_dose_changes_note_backfill_idx` is a partial index over
+  // `(medication_id) WHERE note IS NOT NULL AND note_encrypted IS NULL` — see
+  // migration 0243 (v1.28.46 H4). The med-notes boot-discovery joins dose-
+  // changes to medications on medication_id to reach the owner; the index
+  // leads with that join key. Raw SQL only (partial predicate).
   @@map("medication_dose_changes")
 }
 
@@ -2817,6 +2827,10 @@ model MedicationInventoryItem {
 
   @@index([userId, medicationId, state])
   @@index([userId, expiresAt])
+  // `medication_inventory_items_note_backfill_idx` is a partial index over
+  // `(user_id) WHERE notes IS NOT NULL AND notes_encrypted IS NULL` — see
+  // migration 0243 (v1.28.46 H4) for the med-notes boot-discovery scan. Raw
+  // SQL only (partial predicate not expressible in Prisma).
   @@map("medication_inventory_items")
 }
 
@@ -2876,6 +2890,10 @@ model MedicationSideEffect {
 
   @@index([userId, medicationId, occurredAt])
   @@index([userId, occurredAt])
+  // `medication_side_effects_note_backfill_idx` is a partial index over
+  // `(user_id) WHERE notes IS NOT NULL AND notes_encrypted IS NULL` — see
+  // migration 0243 (v1.28.46 H4) for the med-notes boot-discovery scan. Raw
+  // SQL only (partial predicate not expressible in Prisma).
   @@map("medication_side_effects")
 }
 
@@ -3539,6 +3557,10 @@ model MoodEntry {
   // v1.7.0 sync — keyset support for the `/api/sync/changes` mood feed
   // (`where userId` ordered by `(updatedAt asc, id asc)`).
   @@index([userId, updatedAt, id])
+  // `mood_entries_note_backfill_idx` is a partial index over `(user_id)
+  // WHERE note IS NOT NULL AND note_encrypted IS NULL` — see migration 0243
+  // (v1.28.46 H4), serving the note-encryption boot-discovery scan. Raw SQL
+  // only (partial predicate not expressible in Prisma).
   @@map("mood_entries")
 }
 
@@ -4373,6 +4395,10 @@ model LabResult {
   @@index([userId, analyte, takenAt])
   @@index([userId, deletedAt])
   @@index([biomarkerId])
+  // `lab_results_biomarker_backfill_idx` is a partial index over `(user_id)
+  // WHERE deleted_at IS NULL AND biomarker_id IS NULL` — see migration 0243
+  // (v1.28.46 H4), serving the lab-biomarker boot-discovery `SELECT DISTINCT
+  // user_id`. Raw SQL only (partial predicate not expressible in Prisma).
   @@map("lab_results")
 }
 
@@ -6055,6 +6081,11 @@ model InboundDocument {
   // a superset of the plain `(userId, deletedAt)` index, which is therefore
   // redundant for read planning and dropped.
   @@index([userId, deletedAt, documentDate])
+  // `inbound_documents_thumbnail_backfill_idx` is a partial index over
+  // `(user_id, mime_type) WHERE deleted_at IS NULL` — see migration 0243
+  // (v1.28.46 H4). It bounds the document-side scan of the thumbnail
+  // boot-discovery (which anti-joins document_thumbnails for the missing
+  // preview). Raw SQL only (partial predicate not expressible in Prisma).
   @@map("inbound_documents")
 }
 
diff --git a/public/sw.js b/public/sw.js
index f0792acaf..0870cf826 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -36,7 +36,7 @@ try {
 // v1.4.38.4 → v1.4.42. Do not hand-edit; bump `package.json` and rebuild.
 const CACHE_VERSION =
   (typeof self !== "undefined" && self.__APP_VERSION__) ||
-  /* @sw-version-fallback */ "v1.28.45";
+  /* @sw-version-fallback */ "v1.28.46";
 const STATIC_CACHE = `healthlog-static-${CACHE_VERSION}`;
 const PAGE_CACHE = `healthlog-pages-${CACHE_VERSION}`;
 // v1.18.6 — read-only data cache for a curated allowlist of safe GET `/api/*`
diff --git a/src/components/insights/coach-panel/__tests__/chat-bubble-memo.test.tsx b/src/components/insights/coach-panel/__tests__/chat-bubble-memo.test.tsx
new file mode 100644
index 000000000..da9e67e2e
--- /dev/null
+++ b/src/components/insights/coach-panel/__tests__/chat-bubble-memo.test.tsx
@@ -0,0 +1,89 @@
+/**
+ * v1.28.46 perf (M3) — ChatBubble is wrapped in React.memo so a streamed
+ * token (which grows the live turn's content and re-runs the thread's
+ * messages.map) does not re-render every settled bubble. These tests pin the
+ * memo comparator contract:
+ *   - a per-render `onRegenerate` closure identity change alone does NOT force
+ *     a re-render (the thread rebuilds that closure every render),
+ *   - a `content` or `streaming` change DOES,
+ *   - every other render-affecting prop is compared,
+ * and that the exported component is actually memoized.
+ */
+import { describe, it, expect } from "vitest";
+
+// Importing the module pulls the bubble's hook deps; stub them so the import
+// is side-effect free (mirrors the sibling coach-charts harness).
+import { vi } from "vitest";
+vi.mock("@/hooks/use-auth", () => ({
+  useAuth: () => ({ user: null, isAuthenticated: true, isLoading: false }),
+}));
+vi.mock("@tanstack/react-query", () => ({
+  useQuery: () => ({ data: undefined }),
+  useMutation: () => ({ mutate: vi.fn(), isPending: false, isError: false }),
+}));
+
+import { ChatBubble, areChatBubblePropsEqual } from "../chat-bubble";
+
+type Props = Parameters<typeof areChatBubblePropsEqual>[0];
+
+function baseProps(overrides: Partial<Props> = {}): Props {
+  return {
+    role: "assistant",
+    content: "hello",
+    metricSource: null,
+    providerType: "openai",
+    messageId: "m1",
+    createdAt: "2026-01-01T00:00:00.000Z",
+    ...overrides,
+  };
+}
+
+describe("areChatBubblePropsEqual", () => {
+  it("treats a fresh onRegenerate closure as equal (skips re-render)", () => {
+    const prev = baseProps({ onRegenerate: () => {} });
+    const next = baseProps({ onRegenerate: () => {} });
+    expect(areChatBubblePropsEqual(prev, next)).toBe(true);
+  });
+
+  it("re-renders when the streamed content changes", () => {
+    const prev = baseProps({ content: "hel", streaming: true });
+    const next = baseProps({ content: "hell", streaming: true });
+    expect(areChatBubblePropsEqual(prev, next)).toBe(false);
+  });
+
+  it("re-renders when the streaming flag flips", () => {
+    const prev = baseProps({ content: "done", streaming: true });
+    const next = baseProps({ content: "done", streaming: false });
+    expect(areChatBubblePropsEqual(prev, next)).toBe(false);
+  });
+
+  it("re-renders when onRegenerate presence changes (undefined -> defined)", () => {
+    const prev = baseProps({ onRegenerate: undefined });
+    const next = baseProps({ onRegenerate: () => {} });
+    expect(areChatBubblePropsEqual(prev, next)).toBe(false);
+  });
+
+  it("re-renders when a grounding / identity prop changes by reference", () => {
+    const prev = baseProps({ metricSource: null });
+    const next = baseProps({ metricSource: { metrics: ["weight"] } as never });
+    expect(areChatBubblePropsEqual(prev, next)).toBe(false);
+
+    expect(
+      areChatBubblePropsEqual(
+        baseProps({ messageId: "m1" }),
+        baseProps({ messageId: "m2" }),
+      ),
+    ).toBe(false);
+  });
+
+  it("is stable for identical settled props", () => {
+    expect(areChatBubblePropsEqual(baseProps(), baseProps())).toBe(true);
+  });
+});
+
+describe("ChatBubble memoization", () => {
+  it("is wrapped in React.memo", () => {
+    const typeTag = (ChatBubble as unknown as { $$typeof?: symbol }).$$typeof;
+    expect(String(typeTag)).toContain("memo");
+  });
+});
diff --git a/src/components/insights/coach-panel/chat-bubble.tsx b/src/components/insights/coach-panel/chat-bubble.tsx
index 49f3d7dd7..9d821ceae 100644
--- a/src/components/insights/coach-panel/chat-bubble.tsx
+++ b/src/components/insights/coach-panel/chat-bubble.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { useCallback, useEffect, useId, useRef, useState } from "react";
+import { memo, useCallback, useEffect, useId, useRef, useState } from "react";
 import Link from "next/link";
 import { useMutation } from "@tanstack/react-query";
 import { toast } from "sonner";
@@ -409,7 +409,49 @@ interface ChatBubbleProps {
   onRegenerate?: () => void;
 }
 
-export function ChatBubble({
+/**
+ * v1.28.46 perf (M3) — memo comparator for `ChatBubble`. The Coach thread
+ * re-renders on every streamed token (the live turn's content grows), which
+ * re-runs `messages.map` and re-creates every persisted bubble. Without memo
+ * each settled bubble re-runs `selectCoachChartTokens` + provenance work per
+ * token; on a long thread that is tokens × messages renders and drops frames.
+ *
+ * Every prop that changes the bubble's output is compared by value/reference.
+ * The ONE prop that is not stable across renders is `onRegenerate`: the thread
+ * builds a fresh `() => onRegenerate(precedingUserContent)` closure per render
+ * for each assistant message (message-thread.tsx), so a naive shallow memo
+ * would never skip. Its identity does not affect rendering (the closure is only
+ * invoked on click, and captures the same preceding user text on a settled
+ * thread), so it is compared by PRESENCE, not identity. Result: only the
+ * streaming bubble (whose `content`/`streaming` actually change) re-renders.
+ *
+ * Exported so the contract is unit-testable without standing up the thread.
+ */
+export function areChatBubblePropsEqual(
+  prev: ChatBubbleProps,
+  next: ChatBubbleProps,
+): boolean {
+  return (
+    prev.role === next.role &&
+    prev.content === next.content &&
+    prev.streaming === next.streaming &&
+    prev.inProgress === next.inProgress &&
+    prev.errorCode === next.errorCode &&
+    prev.providerType === next.providerType &&
+    prev.messageId === next.messageId &&
+    prev.tokensUsed === next.tokensUsed &&
+    prev.model === next.model &&
+    prev.createdAt === next.createdAt &&
+    prev.metricSource === next.metricSource &&
+    prev.suggestion === next.suggestion &&
+    prev.suggestedAction === next.suggestedAction &&
+    prev.usage === next.usage &&
+    // onRegenerate is a per-render closure — compare only whether it is present.
+    (prev.onRegenerate === undefined) === (next.onRegenerate === undefined)
+  );
+}
+
+function ChatBubbleImpl({
   role,
   content,
   metricSource,
@@ -809,6 +851,15 @@ export function ChatBubble({
   );
 }
 
+/**
+ * v1.28.46 perf (M3) — memoized bubble. Skips re-render for every settled
+ * bubble while the streaming turn grows token-by-token; the streaming bubble
+ * (changed `content`/`streaming`) is the only one that re-renders. `displayName`
+ * is set so the name survives the memo wrapper in React DevTools.
+ */
+export const ChatBubble = memo(ChatBubbleImpl, areChatBubblePropsEqual);
+ChatBubble.displayName = "ChatBubble";
+
 /**
  * v1.16.8 — per-message remember control under the user bubble.
  *
diff --git a/src/lib/doctor-report-data.ts b/src/lib/doctor-report-data.ts
index 8f7e0d904..2cf72fdfc 100644
--- a/src/lib/doctor-report-data.ts
+++ b/src/lib/doctor-report-data.ts
@@ -256,6 +256,13 @@ export async function collectDoctorReportData(
               moodLoggedAt: { gte: start, lte: end },
             },
             orderBy: { moodLoggedAt: "asc" },
+            // v1.28.46 perf (H1) — narrow select. The collector reads exactly
+            // two fields off each mood row: `score` (the mood summary /
+            // distribution) and `tags` (GLP-1 side-effect tag counts). The
+            // full-width read pulled every column — including the encrypted
+            // `noteEncrypted` Bytes and the plaintext `note` free text — across
+            // the whole report window, none of which the report ever touches.
+            select: { score: true, tags: true },
           })
         : Promise.resolve([]),
       prisma.user.findUnique({
diff --git a/src/lib/insights/__tests__/comparison-snapshot-window.test.ts b/src/lib/insights/__tests__/comparison-snapshot-window.test.ts
index 22d52888b..17411e666 100644
--- a/src/lib/insights/__tests__/comparison-snapshot-window.test.ts
+++ b/src/lib/insights/__tests__/comparison-snapshot-window.test.ts
@@ -1,23 +1,28 @@
 /**
- * v1.20.1 perf — the comparison-snapshot builder must bound its
- * per-type measurement read to a ~400-day window instead of scanning a
- * user's entire history. The snapshot only feeds summarize()'s avg30 /
- * avg30LastMonth / avg30LastYear, and the widest of those reaches into
- * the [365, 395)-day window, so nothing older than 395 days can change a
- * result. These tests pin that:
- *   - every measurement read carries a `measuredAt.gte` lower bound,
- *   - the bound sits at ~400 days (5-day floor over the 395-day reach),
- *   - the three averages are unaffected for in-window data.
+ * v1.20.1 perf — the comparison-snapshot builder must bound its per-type
+ * measurement read instead of scanning a user's entire history. v1.28.46
+ * perf — it now computes the two means it actually reads (avg30 + one
+ * baseline mean) as DB-side AVG aggregates over the exact windows, instead
+ * of pulling every raw row into JS and averaging there. The snapshot only
+ * feeds summarize()'s avg30 / avg30LastMonth / avg30LastYear, and only two
+ * of those are read per call.
  *
- * The read fans out over all seven snapshot types on the page-blocking
- * POST /api/insights/generate path AND the nightly pregenerate cron, so
- * an unbounded scan is tens of thousands of rows per type on multi-year
- * accounts.
+ * These tests pin:
+ *   - non-sleep types compute via `measurement.aggregate({ _avg })`, never a
+ *     raw row read, over the exact half-open windows summarize() uses,
+ *   - SLEEP_DURATION stays on the raw ~400-day findMany path (per-night
+ *     reconstruction cannot be a bare SQL AVG),
+ *   - OUTPUT-EQUIVALENCE: the aggregate path produces byte-identical
+ *     currentAvg / baselineAvg / delta / deltaPercent to the previous
+ *     raw-findMany-then-summarize() implementation, for a fixture dataset.
  */
 import { describe, it, expect, vi, beforeEach } from "vitest";
 
+import { summarize, type DataPoint } from "@/lib/analytics/trends";
+
 const findUnique = vi.fn();
 const measurementFindMany = vi.fn();
+const measurementAggregate = vi.fn();
 
 vi.mock("@/lib/db", () => ({
   prisma: {
@@ -26,10 +31,11 @@ vi.mock("@/lib/db", () => ({
     },
     measurement: {
       findMany: (...a: unknown[]) => measurementFindMany(...a),
+      aggregate: (...a: unknown[]) => measurementAggregate(...a),
     },
   },
 }));
-// SLEEP_DURATION branch helpers — the test never exercises the sleep
+// SLEEP_DURATION branch helpers — most tests never exercise the sleep
 // reconstruction maths, but the builder imports these unconditionally.
 vi.mock("@/lib/tz/resolver", () => ({
   resolveUserTimezone: vi.fn(async () => "Europe/Berlin"),
@@ -42,13 +48,31 @@ import { buildComparisonSnapshotForUser } from "../comprehensive-generate";
 
 const DAY = 86_400_000;
 
+/**
+ * Faithful in-memory stand-in for Postgres `AVG(value)` over a measured-at
+ * window: same half-open bounds Prisma would translate, same sum/count as the
+ * DB. Returns null on an empty slice (matching `_avg.value === null`).
+ */
+function avgWindow(
+  rows: { measuredAt: Date; value: number }[],
+  bounds: { gt?: Date; gte?: Date; lte?: Date; lt?: Date },
+): number | null {
+  const slice = rows.filter((r) => {
+    const t = r.measuredAt.getTime();
+    if (bounds.gt && !(t > bounds.gt.getTime())) return false;
+    if (bounds.gte && !(t >= bounds.gte.getTime())) return false;
+    if (bounds.lte && !(t <= bounds.lte.getTime())) return false;
+    if (bounds.lt && !(t < bounds.lt.getTime())) return false;
+    return true;
+  });
+  if (slice.length === 0) return null;
+  return slice.reduce((s, r) => s + r.value, 0) / slice.length;
+}
+
 beforeEach(() => {
   vi.clearAllMocks();
-  // Comparison toggle ON → the builder runs its per-type reads. The
-  // baseline value drives which prior-period mean the snapshot reports.
-  // `resolveDashboardLayout` only honours `comparisonBaseline` on a blob
-  // that carries a numeric `version` + a `widgets` array; otherwise it
-  // clamps to "none".
+  // Comparison toggle ON → the builder runs its per-type reads. The baseline
+  // value drives which prior-period mean the snapshot reports.
   findUnique.mockResolvedValue({
     dashboardWidgetsJson: {
       version: 1,
@@ -56,49 +80,14 @@ beforeEach(() => {
       comparisonBaseline: "lastYear",
     },
   });
-  // No measurements by default; individual tests override per call.
+  // No sleep rows by default; the raw findMany path only serves SLEEP_DURATION.
   measurementFindMany.mockResolvedValue([]);
+  // No measurements by default; individual tests override per call.
+  measurementAggregate.mockResolvedValue({ _avg: { value: null } });
 });
 
-describe("buildComparisonSnapshotForUser — bounded read window", () => {
-  it("bounds every measurement read with a ~400-day measuredAt.gte floor", async () => {
-    const before = Date.now();
-    await buildComparisonSnapshotForUser("u1");
-    const after = Date.now();
-
-    // One findMany per snapshot type (sleep takes a different select but
-    // the same where shape). Every call must carry the lower bound.
-    expect(measurementFindMany).toHaveBeenCalled();
-    for (const call of measurementFindMany.mock.calls) {
-      const where = (call[0] as { where: Record<string, unknown> }).where;
-      expect(where).toMatchObject({ userId: "u1", deletedAt: null });
-      const measuredAt = where.measuredAt as { gte: Date };
-      expect(measuredAt).toBeDefined();
-      expect(measuredAt.gte).toBeInstanceOf(Date);
-
-      // The floor is anchored on Date.now() - 400 days, read inside the call.
-      // Since before <= snapshotNow <= after, the floor brackets exactly to
-      // [before - 400d, after - 400d] — no tick-timing slack assumptions.
-      const gteMs = measuredAt.gte.getTime();
-      expect(gteMs).toBeGreaterThanOrEqual(before - 400 * DAY);
-      expect(gteMs).toBeLessThanOrEqual(after - 400 * DAY);
-    }
-  });
-
-  it("keeps the floor strictly older than the 395-day reach of avg30LastYear", async () => {
-    const now = Date.now();
-    await buildComparisonSnapshotForUser("u1");
-
-    // avg30LastYear reads points with age < 395 days. The bound must sit
-    // at least 5 days older so it never clips that window.
-    for (const call of measurementFindMany.mock.calls) {
-      const where = (call[0] as { where: { measuredAt: { gte: Date } } }).where;
-      const ageDays = (now - where.measuredAt.gte.getTime()) / DAY;
-      expect(ageDays).toBeGreaterThanOrEqual(395);
-    }
-  });
-
-  it("computes avg30 / avg30LastMonth / avg30LastYear unchanged for in-window data", async () => {
+describe("buildComparisonSnapshotForUser — aggregate windows", () => {
+  it("computes non-sleep means via aggregate with the exact half-open windows", async () => {
     findUnique.mockResolvedValue({
       dashboardWidgetsJson: {
         version: 1,
@@ -106,30 +95,159 @@ describe("buildComparisonSnapshotForUser — bounded read window", () => {
         comparisonBaseline: "lastMonth",
       },
     });
+    const before = Date.now();
+    await buildComparisonSnapshotForUser("u1");
+    const after = Date.now();
 
+    // Every non-sleep type issues exactly two aggregate reads (current +
+    // baseline). None issues a raw non-sleep findMany.
+    expect(measurementAggregate).toHaveBeenCalled();
+    const currentCalls: { gt: Date }[] = [];
+    const baselineCalls: { gt: Date; lte: Date }[] = [];
+    for (const call of measurementAggregate.mock.calls) {
+      const where = (call[0] as { where: Record<string, unknown> }).where;
+      expect(where).toMatchObject({ userId: "u1", deletedAt: null });
+      const measuredAt = where.measuredAt as {
+        gt: Date;
+        lte?: Date;
+      };
+      expect(measuredAt.gt).toBeInstanceOf(Date);
+      if (measuredAt.lte)
+        baselineCalls.push(measuredAt as { gt: Date; lte: Date });
+      else currentCalls.push(measuredAt as { gt: Date });
+    }
+    // current window: measuredAt > now - 30d (no upper bound).
+    for (const w of currentCalls) {
+      const gtMs = w.gt.getTime();
+      expect(gtMs).toBeGreaterThanOrEqual(before - 30 * DAY);
+      expect(gtMs).toBeLessThanOrEqual(after - 30 * DAY);
+    }
+    // lastMonth baseline window: (now - 60d, now - 30d].
+    for (const w of baselineCalls) {
+      const gtMs = w.gt.getTime();
+      const lteMs = w.lte.getTime();
+      expect(gtMs).toBeGreaterThanOrEqual(before - 60 * DAY);
+      expect(gtMs).toBeLessThanOrEqual(after - 60 * DAY);
+      expect(lteMs).toBeGreaterThanOrEqual(before - 30 * DAY);
+      expect(lteMs).toBeLessThanOrEqual(after - 30 * DAY);
+    }
+    // Six non-sleep types × 2 windows = 12 aggregate reads; no raw non-sleep read.
+    expect(currentCalls.length).toBe(6);
+    expect(baselineCalls.length).toBe(6);
+  });
+
+  it("reads SLEEP_DURATION through the raw ~400-day findMany, never aggregate", async () => {
+    await buildComparisonSnapshotForUser("u1");
+    // Exactly one findMany — the SLEEP_DURATION branch — and it carries a
+    // ~400-day measuredAt.gte floor.
+    expect(measurementFindMany).toHaveBeenCalledTimes(1);
     const now = Date.now();
-    // WEIGHT is the first non-sleep type. Seed three points, one in each
-    // of the avg30 (current), avg30LastMonth ([30,60)) windows — all well
-    // inside the 400-day floor.
-    measurementFindMany.mockImplementation(
-      async (args: { where: { type: string } }) => {
-        if (args.where.type !== "WEIGHT") return [];
-        return [
-          { measuredAt: new Date(now - 5 * DAY), value: 80 }, // current
-          { measuredAt: new Date(now - 45 * DAY), value: 84 }, // lastMonth
-        ];
+    const where = (
+      measurementFindMany.mock.calls[0][0] as {
+        where: { type: string; measuredAt: { gte: Date } };
+      }
+    ).where;
+    expect(where.type).toBe("SLEEP_DURATION");
+    const ageDays = (now - where.measuredAt.gte.getTime()) / DAY;
+    expect(ageDays).toBeGreaterThanOrEqual(395);
+  });
+
+  it("baseline=lastYear uses the [365, 395)-day window (measuredAt > now-395d && <= now-365d)", async () => {
+    const before = Date.now();
+    await buildComparisonSnapshotForUser("u1"); // default baseline = lastYear
+    const after = Date.now();
+    const baselineCalls = measurementAggregate.mock.calls
+      .map(
+        (c) =>
+          (c[0] as { where: { measuredAt: { gt: Date; lte?: Date } } }).where
+            .measuredAt,
+      )
+      .filter((m): m is { gt: Date; lte: Date } => m.lte != null);
+    expect(baselineCalls.length).toBe(6);
+    for (const w of baselineCalls) {
+      const gtMs = w.gt.getTime();
+      const lteMs = w.lte.getTime();
+      expect(gtMs).toBeGreaterThanOrEqual(before - 395 * DAY);
+      expect(gtMs).toBeLessThanOrEqual(after - 395 * DAY);
+      expect(lteMs).toBeGreaterThanOrEqual(before - 365 * DAY);
+      expect(lteMs).toBeLessThanOrEqual(after - 365 * DAY);
+    }
+  });
+});
+
+describe("buildComparisonSnapshotForUser — output-equivalence to the raw-average path", () => {
+  it("emits identical metrics to findMany-then-summarize() for a fixture (lastMonth)", async () => {
+    findUnique.mockResolvedValue({
+      dashboardWidgetsJson: {
+        version: 1,
+        widgets: [],
+        comparisonBaseline: "lastMonth",
+      },
+    });
+    const now = Date.now();
+    // A WEIGHT fixture with several rows spread across the current [0,30),
+    // lastMonth [30,60), and out-of-window regions — the kind of skew where a
+    // wrong window boundary or rounding step would diverge.
+    const weightRows: { measuredAt: Date; value: number }[] = [
+      { measuredAt: new Date(now - 2 * DAY), value: 80.4 },
+      { measuredAt: new Date(now - 9 * DAY), value: 81.1 },
+      { measuredAt: new Date(now - 21 * DAY), value: 79.9 },
+      { measuredAt: new Date(now - 33 * DAY), value: 84.2 },
+      { measuredAt: new Date(now - 48 * DAY), value: 83.3 },
+      { measuredAt: new Date(now - 59 * DAY), value: 85.0 },
+      // out-of-window (older than lastMonth) — must not influence either mean.
+      { measuredAt: new Date(now - 120 * DAY), value: 99.0 },
+    ];
+
+    // The aggregate mock is the "database": it applies the builder's window
+    // and averages the fixture rows.
+    measurementAggregate.mockImplementation(
+      async (args: {
+        where: { type: string; measuredAt: { gt?: Date; lte?: Date } };
+      }) => {
+        if (args.where.type !== "WEIGHT") return { _avg: { value: null } };
+        return {
+          _avg: { value: avgWindow(weightRows, args.where.measuredAt) },
+        };
       },
     );
 
     const snapshot = await buildComparisonSnapshotForUser("u1");
-    expect(snapshot).not.toBeNull();
     const weight = snapshot!.metrics.find((m) => m.type === "weight");
     expect(weight).toBeDefined();
-    // avg30 over the single current point.
-    expect(weight!.currentAvg).toBe(80);
-    // lastMonth baseline over the single [30,60) point.
-    expect(weight!.baselineAvg).toBe(84);
-    expect(weight!.delta).toBe(-4);
+
+    // Reference: the PREVIOUS implementation — read the whole 400-day window
+    // then summarize() in JS.
+    const points: DataPoint[] = weightRows
+      .filter((r) => r.measuredAt.getTime() >= now - 400 * DAY)
+      .map((r) => ({ date: r.measuredAt, value: r.value }));
+    const summary = summarize(points);
+    const expectedCurrent = summary.avg30 ?? null;
+    const expectedBaseline = summary.avg30LastMonth ?? null;
+    const expectedDelta =
+      expectedCurrent !== null && expectedBaseline !== null
+        ? Math.round((expectedCurrent - expectedBaseline) * 100) / 100
+        : null;
+    const expectedDeltaPercent =
+      expectedDelta !== null &&
+      expectedBaseline !== null &&
+      expectedBaseline !== 0
+        ? Math.round((expectedDelta / Math.abs(expectedBaseline)) * 100 * 10) /
+          10
+        : null;
+
+    expect(weight!.currentAvg).toBe(expectedCurrent);
+    expect(weight!.baselineAvg).toBe(expectedBaseline);
+    expect(weight!.delta).toBe(expectedDelta);
+    expect(weight!.deltaPercent).toBe(expectedDeltaPercent);
+  });
+
+  it("drops a metric with no data in either window (parity with the old filter)", async () => {
+    // Default aggregate mock returns null for every window → every non-sleep
+    // metric is null/null and filtered out; sleep has no rows too.
+    const snapshot = await buildComparisonSnapshotForUser("u1");
+    expect(snapshot).not.toBeNull();
+    expect(snapshot!.metrics).toEqual([]);
   });
 
   it("returns null without reading measurements when the comparison toggle is off", async () => {
@@ -142,6 +260,7 @@ describe("buildComparisonSnapshotForUser — bounded read window", () => {
     });
     const snapshot = await buildComparisonSnapshotForUser("u1");
     expect(snapshot).toBeNull();
+    expect(measurementAggregate).not.toHaveBeenCalled();
     expect(measurementFindMany).not.toHaveBeenCalled();
   });
 });
diff --git a/src/lib/insights/comprehensive-generate.ts b/src/lib/insights/comprehensive-generate.ts
index 238fe1ed0..61e1d33ea 100644
--- a/src/lib/insights/comprehensive-generate.ts
+++ b/src/lib/insights/comprehensive-generate.ts
@@ -18,6 +18,7 @@
  * NO synchronous request lifecycle: the cron path runs entirely on
  * pg-boss, never inside an HTTP handler.
  */
+import pLimit from "p-limit";
 import { prisma } from "@/lib/db";
 import {
   extractFeatures,
@@ -313,91 +314,127 @@ export async function buildComparisonSnapshotForUser(
     ACTIVITY_STEPS: "",
   };
   const types = Object.keys(typeToSnapshotKey) as MeasurementType[];
-  // The snapshot only feeds summarize()'s avg30 / avg30LastMonth /
-  // avg30LastYear. The widest of those reaches back into the [365, 395)-day
-  // window (ageMs < 395 * DAY in meanOfWindow), so nothing older than 395
-  // days can change a result. Bound the read at 400 days — a 5-day floor over
-  // the strict-less-than boundary — instead of scanning the full history,
-  // which on multi-year accounts is tens of thousands of rows per type on the
-  // page-blocking generate path and the nightly pregenerate cron.
-  const sinceMeasuredAt = new Date(Date.now() - 400 * 86_400_000);
+
+  // The snapshot only ever reads two of summarize()'s means per call: avg30
+  // (the "current" 30-day mean) and exactly ONE baseline mean — avg30LastMonth
+  // (window [30, 60) days ago) or avg30LastYear (window [365, 395) days ago),
+  // chosen by `baseline`. Rather than pull every raw row across a 400-day
+  // window into JS and average there (tens of thousands of rows per dense type
+  // on the page-blocking generate path AND the nightly pregenerate cron),
+  // compute each mean as a DB-side AVG over the exact window the JS reducer
+  // covered. The 2-dp rounding and the half-open window bounds are matched to
+  // summarize()/meanOfWindow() byte-for-byte, so the emitted metrics are
+  // numerically identical to the previous raw-scan implementation.
+  //
+  // SLEEP_DURATION stays on the raw path: it is stored ONE ROW PER STAGE per
+  // night, so a bare SQL AVG would blend per-stage rows and double-count a
+  // bare ASLEEP aggregate against its granular twin. Only the per-night dedup
+  // reconstruction yields a meaningful nightly TIME-ASLEEP total.
+  //
+  // Anchor every window on ONE clock read so the aggregate reads and the sleep
+  // reconstruction share an identical "now" (summarize() reads the clock once
+  // too). Bounds mirror summarize(): avg30 keeps `now - measuredAt < 30d`
+  // (measuredAt > now-30d, no upper bound); meanOfWindow(a,b) keeps
+  // `a*DAY <= age < b*DAY` (measuredAt > now-b AND measuredAt <= now-a).
+  const nowMs = Date.now();
+  const DAY = 86_400_000;
+  const currentWhere: { gt: Date } = { gt: new Date(nowMs - 30 * DAY) };
+  const baselineWhere: { gt: Date; lte: Date } =
+    baseline === "lastMonth"
+      ? { gt: new Date(nowMs - 60 * DAY), lte: new Date(nowMs - 30 * DAY) }
+      : { gt: new Date(nowMs - 395 * DAY), lte: new Date(nowMs - 365 * DAY) };
+
+  // Rounded (2 dp) DB-side mean of `value` over one measured-at window, or null
+  // when the window holds no live rows — matching summarize()'s avg30 /
+  // meanOfWindow exactly (both round with Math.round(x * 100) / 100 and return
+  // null on an empty slice).
+  const avgOverWindow = async (
+    type: MeasurementType,
+    measuredAt: { gt: Date; lte?: Date },
+  ): Promise<number | null> => {
+    const agg = await prisma.measurement.aggregate({
+      where: { userId, type, deletedAt: null, measuredAt },
+      _avg: { value: true },
+    });
+    const avg = agg._avg.value;
+    return avg === null ? null : Math.round(avg * 100) / 100;
+  };
+
+  // Sleep still needs the raw 400-day window for the per-night reconstruction;
+  // the widest baseline mean reaches into [365, 395) days, so a 5-day floor
+  // over that boundary is the smallest safe bound.
+  const sleepSinceMeasuredAt = new Date(nowMs - 400 * DAY);
+
+  // Cap the type fan-out so a multi-metric account cannot open one DB
+  // connection per type at once (mirrors the pLimit(4) discipline in
+  // series-batch/route.ts).
+  const limit = pLimit(4);
+
   const rows = await Promise.all(
-    types.map(async (type) => {
-      // SLEEP_DURATION is stored ONE ROW PER STAGE per night; summarising the
-      // raw stage rows mislabels a per-stage average as a night total (and
-      // double-counts a bare ASLEEP aggregate against its granular twin). Route
-      // the comparison through the per-night dedup reconstruction so the
-      // current/baseline averages are per-night TIME-ASLEEP totals in minutes.
-      let dataPoints: DataPoint[];
-      if (type === "SLEEP_DURATION") {
-        const [sleepRows, sleepTz, sleepPriority] = await Promise.all([
-          prisma.measurement.findMany({
-            where: {
-              userId,
-              type,
-              deletedAt: null,
-              measuredAt: { gte: sinceMeasuredAt },
-            },
-            orderBy: { measuredAt: "asc" },
-            select: {
-              measuredAt: true,
-              value: true,
-              sleepStage: true,
-              source: true,
-              // Writer-level collapse: two HealthKit apps behind one
-              // source (watch stages vs phone in-bed) must not blend.
-              deviceType: true,
-            },
-          }),
-          resolveUserTimezone(userId),
-          loadUserSourcePriority(userId),
-        ]);
-        dataPoints = reconstructSleepNights(
-          sleepRows as SleepStageRow[],
-          sleepTz,
-          sleepPriority,
-        )
-          .filter((n) => n.asleepMinutes > 0)
-          .map((n) => ({ date: n.measuredAt, value: n.asleepMinutes }));
-      } else {
-        const measurements = await prisma.measurement.findMany({
-          where: {
-            userId,
-            type,
-            deletedAt: null,
-            measuredAt: { gte: sinceMeasuredAt },
-          },
-          orderBy: { measuredAt: "asc" },
-          select: { measuredAt: true, value: true },
-        });
-        dataPoints = measurements.map((m): DataPoint => ({
-          date: m.measuredAt,
-          value: m.value,
-        }));
-      }
-      const summary = summarize(dataPoints);
-      const baselineAvg =
-        baseline === "lastMonth"
-          ? (summary.avg30LastMonth ?? null)
-          : (summary.avg30LastYear ?? null);
-      const currentAvg = summary.avg30 ?? null;
-      const delta =
-        currentAvg !== null && baselineAvg !== null
-          ? Math.round((currentAvg - baselineAvg) * 100) / 100
-          : null;
-      const deltaPercent =
-        delta !== null && baselineAvg !== null && baselineAvg !== 0
-          ? Math.round((delta / Math.abs(baselineAvg)) * 100 * 10) / 10
-          : null;
-      return {
-        type: typeToSnapshotKey[type] ?? type,
-        currentAvg,
-        baselineAvg,
-        delta,
-        deltaPercent,
-        unit: typeUnits[type] ?? "",
-      };
-    }),
+    types.map((type) =>
+      limit(async () => {
+        let currentAvg: number | null;
+        let baselineAvg: number | null;
+        if (type === "SLEEP_DURATION") {
+          const [sleepRows, sleepTz, sleepPriority] = await Promise.all([
+            prisma.measurement.findMany({
+              where: {
+                userId,
+                type,
+                deletedAt: null,
+                measuredAt: { gte: sleepSinceMeasuredAt },
+              },
+              orderBy: { measuredAt: "asc" },
+              select: {
+                measuredAt: true,
+                value: true,
+                sleepStage: true,
+                source: true,
+                // Writer-level collapse: two HealthKit apps behind one
+                // source (watch stages vs phone in-bed) must not blend.
+                deviceType: true,
+              },
+            }),
+            resolveUserTimezone(userId),
+            loadUserSourcePriority(userId),
+          ]);
+          const dataPoints: DataPoint[] = reconstructSleepNights(
+            sleepRows as SleepStageRow[],
+            sleepTz,
+            sleepPriority,
+          )
+            .filter((n) => n.asleepMinutes > 0)
+            .map((n) => ({ date: n.measuredAt, value: n.asleepMinutes }));
+          const summary = summarize(dataPoints);
+          currentAvg = summary.avg30 ?? null;
+          baselineAvg =
+            baseline === "lastMonth"
+              ? (summary.avg30LastMonth ?? null)
+              : (summary.avg30LastYear ?? null);
+        } else {
+          [currentAvg, baselineAvg] = await Promise.all([
+            avgOverWindow(type, currentWhere),
+            avgOverWindow(type, baselineWhere),
+          ]);
+        }
+        const delta =
+          currentAvg !== null && baselineAvg !== null
+            ? Math.round((currentAvg - baselineAvg) * 100) / 100
+            : null;
+        const deltaPercent =
+          delta !== null && baselineAvg !== null && baselineAvg !== 0
+            ? Math.round((delta / Math.abs(baselineAvg)) * 100 * 10) / 10
+            : null;
+        return {
+          type: typeToSnapshotKey[type] ?? type,
+          currentAvg,
+          baselineAvg,
+          delta,
+          deltaPercent,
+          unit: typeUnits[type] ?? "",
+        };
+      }),
+    ),
   );
 
   const metrics = rows.filter(
diff --git a/src/lib/jobs/document-thumbnail-backfill.ts b/src/lib/jobs/document-thumbnail-backfill.ts
index 0b80f25ef..cc30f88b2 100644
--- a/src/lib/jobs/document-thumbnail-backfill.ts
+++ b/src/lib/jobs/document-thumbnail-backfill.ts
@@ -18,6 +18,7 @@
  * The queue MUST be registered in the maintenance registrar
  * (`src/lib/jobs/reminder/register-maintenance.ts`) so pg-boss provisions it.
  */
+import { Prisma } from "@/generated/prisma/client";
 import { prisma } from "@/lib/db";
 import { nativeCanvasSupported } from "@/lib/documents/native-canvas-support";
 import { getGlobalBoss } from "@/lib/jobs/boss-instance";
@@ -112,19 +113,22 @@ export async function enqueueBootTimeThumbnailBackfill(): Promise<{
   // would only churn the queue — every generation no-ops behind the gate.
   if (!nativeCanvasSupported()) return { enqueued: 0 };
 
-  // Distinct users with at least one thumbnailable, not-yet-thumbnailed doc.
-  const rows = await prisma.inboundDocument.findMany({
-    where: {
-      deletedAt: null,
-      mimeType: { in: [...THUMBNAILABLE_MIMES] },
-      thumbnail: { is: null },
-    },
-    select: { userId: true },
-    distinct: ["userId"],
-  });
+  // v1.28.46 perf (H4) — DB-level SELECT DISTINCT with an anti-join to the
+  // thumbnail side table, not Prisma `distinct` (which fetches every matching
+  // row then de-dupes in JS at boot). The migration-0243 partial index over
+  // `(user_id, mime_type) WHERE deleted_at IS NULL` bounds the document-side
+  // scan; `document_thumbnails.document_id` is already UNIQUE (the 1:1
+  // relation) so the `t.id IS NULL` anti-join is index-driven.
+  const rows = await prisma.$queryRaw<{ user_id: string }[]>`
+    SELECT DISTINCT d.user_id AS user_id
+    FROM inbound_documents d
+    LEFT JOIN document_thumbnails t ON t.document_id = d.id
+    WHERE d.deleted_at IS NULL
+      AND d.mime_type IN (${Prisma.join([...THUMBNAILABLE_MIMES])})
+      AND t.id IS NULL`;
 
   let enqueued = 0;
-  for (const { userId } of rows) {
+  for (const { user_id: userId } of rows) {
     const payload: ThumbnailBackfillPayload = {
       userId,
       enqueuedAt: new Date().toISOString(),
diff --git a/src/lib/jobs/lab-biomarker-backfill.ts b/src/lib/jobs/lab-biomarker-backfill.ts
index a9cd8d6bb..6c8ca5c7b 100644
--- a/src/lib/jobs/lab-biomarker-backfill.ts
+++ b/src/lib/jobs/lab-biomarker-backfill.ts
@@ -180,11 +180,14 @@ export async function enqueueBootTimeLabBiomarkerBackfill(): Promise<{
   }
 
   try {
-    const rows = await prisma.labResult.findMany({
-      where: { deletedAt: null, biomarkerId: null },
-      select: { userId: true },
-      distinct: ["userId"],
-    });
+    // v1.28.46 perf (H4) — DB-level SELECT DISTINCT, not Prisma `distinct`
+    // (which fetches every matching row then de-dupes in JS at boot). The
+    // migration-0243 partial index over `(user_id) WHERE deleted_at IS NULL
+    // AND biomarker_id IS NULL` makes this an index-only scan that converges
+    // to empty as rows are linked.
+    const rows = await prisma.$queryRaw<{ user_id: string }[]>`
+      SELECT DISTINCT user_id FROM lab_results
+      WHERE deleted_at IS NULL AND biomarker_id IS NULL`;
 
     if (rows.length === 0) {
       return { enqueued: 0, skipped: 0, error: null };
@@ -192,7 +195,7 @@ export async function enqueueBootTimeLabBiomarkerBackfill(): Promise<{
 
     let enqueued = 0;
     let skipped = 0;
-    for (const { userId } of rows) {
+    for (const { user_id: userId } of rows) {
       const payload: LabBiomarkerBackfillPayload = {
         userId,
         enqueuedAt: new Date().toISOString(),
diff --git a/src/lib/jobs/med-notes-encryption-backfill.ts b/src/lib/jobs/med-notes-encryption-backfill.ts
index 8e8bdb047..a6cd35e29 100644
--- a/src/lib/jobs/med-notes-encryption-backfill.ts
+++ b/src/lib/jobs/med-notes-encryption-backfill.ts
@@ -241,31 +241,30 @@ export async function enqueueBootTimeMedNotesEncryptionBackfill(): Promise<{
   }
 
   try {
-    const [sideEffectUsers, doseChangeRows, inventoryUsers] = await Promise.all(
-      [
-        prisma.medicationSideEffect.findMany({
-          where: { notes: { not: null }, notesEncrypted: null },
-          select: { userId: true },
-          distinct: ["userId"],
-        }),
-        // Dose-changes carry no userId — surface the parent medication's owner
-        // and dedupe in JS (distinct cannot span a relation field).
-        prisma.medicationDoseChange.findMany({
-          where: { note: { not: null }, noteEncrypted: null },
-          select: { medication: { select: { userId: true } } },
-        }),
-        prisma.medicationInventoryItem.findMany({
-          where: { notes: { not: null }, notesEncrypted: null },
-          select: { userId: true },
-          distinct: ["userId"],
-        }),
-      ],
-    );
+    // v1.28.46 perf (H4) — DB-level SELECT DISTINCT, not Prisma `distinct`
+    // (which fetches every matching row then de-dupes in JS at boot). Dose-
+    // changes carry no userId, so their owner comes through a join on the
+    // parent medication. The migration-0243 partial indexes match each
+    // predicate so the scans stay index-only and converge to empty.
+    const [sideEffectUsers, doseChangeUsers, inventoryUsers] =
+      await Promise.all([
+        prisma.$queryRaw<{ user_id: string }[]>`
+          SELECT DISTINCT user_id FROM medication_side_effects
+          WHERE notes IS NOT NULL AND notes_encrypted IS NULL`,
+        prisma.$queryRaw<{ user_id: string }[]>`
+          SELECT DISTINCT m.user_id AS user_id
+          FROM medication_dose_changes dc
+          JOIN medications m ON m.id = dc.medication_id
+          WHERE dc.note IS NOT NULL AND dc.note_encrypted IS NULL`,
+        prisma.$queryRaw<{ user_id: string }[]>`
+          SELECT DISTINCT user_id FROM medication_inventory_items
+          WHERE notes IS NOT NULL AND notes_encrypted IS NULL`,
+      ]);
 
     const userIds = new Set<string>();
-    for (const { userId } of sideEffectUsers) userIds.add(userId);
-    for (const { medication } of doseChangeRows) userIds.add(medication.userId);
-    for (const { userId } of inventoryUsers) userIds.add(userId);
+    for (const { user_id } of sideEffectUsers) userIds.add(user_id);
+    for (const { user_id } of doseChangeUsers) userIds.add(user_id);
+    for (const { user_id } of inventoryUsers) userIds.add(user_id);
 
     if (userIds.size === 0) {
       return { enqueued: 0, skipped: 0, error: null };
diff --git a/src/lib/jobs/note-encryption-backfill.ts b/src/lib/jobs/note-encryption-backfill.ts
index 04171bfbe..2b018862f 100644
--- a/src/lib/jobs/note-encryption-backfill.ts
+++ b/src/lib/jobs/note-encryption-backfill.ts
@@ -192,22 +192,25 @@ export async function enqueueBootTimeNoteEncryptionBackfill(
   }
 
   try {
+    // v1.28.46 perf (H4) — DB-level SELECT DISTINCT, not Prisma `distinct`.
+    // Prisma `distinct` fetches EVERY matching row then de-dupes in JS; on the
+    // densest table (`measurements`) that is a full un-migrated-partition scan
+    // materialised into the worker at boot. `SELECT DISTINCT user_id` de-dupes
+    // in Postgres and, with the migration-0243 partial indexes matching each
+    // predicate, becomes an index-only scan that shrinks to nothing as the
+    // backfill converges.
     const [measurementUsers, moodUsers] = await Promise.all([
-      prisma.measurement.findMany({
-        where: { notes: { not: null }, notesEncrypted: null },
-        select: { userId: true },
-        distinct: ["userId"],
-      }),
-      prisma.moodEntry.findMany({
-        where: { note: { not: null }, noteEncrypted: null },
-        select: { userId: true },
-        distinct: ["userId"],
-      }),
+      prisma.$queryRaw<{ user_id: string }[]>`
+        SELECT DISTINCT user_id FROM measurements
+        WHERE notes IS NOT NULL AND notes_encrypted IS NULL`,
+      prisma.$queryRaw<{ user_id: string }[]>`
+        SELECT DISTINCT user_id FROM mood_entries
+        WHERE note IS NOT NULL AND note_encrypted IS NULL`,
     ]);
 
     const userIds = new Set<string>();
-    for (const { userId } of measurementUsers) userIds.add(userId);
-    for (const { userId } of moodUsers) userIds.add(userId);
+    for (const { user_id } of measurementUsers) userIds.add(user_id);
+    for (const { user_id } of moodUsers) userIds.add(user_id);
 
     if (userIds.size === 0) {
       return { enqueued: 0, skipped: 0, error: null };
diff --git a/tests/integration/boot-discovery-scans.test.ts b/tests/integration/boot-discovery-scans.test.ts
new file mode 100644
index 000000000..5e05d967d
--- /dev/null
+++ b/tests/integration/boot-discovery-scans.test.ts
@@ -0,0 +1,182 @@
+/**
+ * v1.28.46 perf (H4) — the boot-time converging-backfill discovery scans now
+ * run a DB-level `SELECT DISTINCT user_id` (with a join / anti-join where the
+ * owner is not a direct column) instead of Prisma's in-memory `distinct`, and
+ * ride the migration-0243 partial indexes. This suite runs the REAL discovery
+ * functions against real Postgres to prove the raw SQL is correct (table +
+ * column names, the medication join, the thumbnail anti-join, the mime IN
+ * filter) and that each returns EXACTLY the set of users still holding
+ * un-migrated rows — no more, no fewer.
+ */
+import { beforeEach, describe, expect, it } from "vitest";
+
+import { setGlobalBoss } from "@/lib/jobs/boss-instance";
+import { nativeCanvasSupported } from "@/lib/documents/native-canvas-support";
+import { enqueueBootTimeNoteEncryptionBackfill } from "@/lib/jobs/note-encryption-backfill";
+import { enqueueBootTimeMedNotesEncryptionBackfill } from "@/lib/jobs/med-notes-encryption-backfill";
+import { enqueueBootTimeLabBiomarkerBackfill } from "@/lib/jobs/lab-biomarker-backfill";
+import { enqueueBootTimeThumbnailBackfill } from "@/lib/jobs/document-thumbnail-backfill";
+import { getPrismaClient, truncateAllTables } from "./setup";
+
+/**
+ * Minimal fake pg-boss that records which (queue, userId) pairs were sent.
+ * The discovery functions call `boss.send(queue, payload, opts)` and expect a
+ * truthy job id; capturing the payload's userId lets us assert the discovered
+ * set without a real queue.
+ */
+function makeCapturingBoss() {
+  const sent: { queue: string; userId: string }[] = [];
+  const boss = {
+    send: async (
+      queue: string,
+      payload: { userId?: string },
+      _opts?: unknown,
+    ) => {
+      if (payload.userId) sent.push({ queue, userId: payload.userId });
+      return `job-${sent.length}`;
+    },
+  };
+  return { boss, sent };
+}
+
+function usersFor(sent: { userId: string }[]): string[] {
+  return [...new Set(sent.map((s) => s.userId))].sort();
+}
+
+async function seedUser(id: string) {
+  await getPrismaClient().user.create({
+    data: {
+      id,
+      username: id,
+      email: `${id}@example.test`,
+      timezone: "Europe/Berlin",
+    },
+  });
+}
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+});
+
+describe("boot-discovery scans (real Postgres)", () => {
+  it("note-encryption discovery returns exactly the users with un-migrated notes", async () => {
+    const prisma = getPrismaClient();
+    await Promise.all([
+      seedUser("disc-a"),
+      seedUser("disc-b"),
+      seedUser("disc-c"),
+    ]);
+    // disc-a: a measurement with a legacy plaintext note (discoverable).
+    await prisma.measurement.create({
+      data: {
+        userId: "disc-a",
+        type: "WEIGHT",
+        value: 80,
+        unit: "kg",
+        measuredAt: new Date(),
+        notes: "legacy plaintext",
+      },
+    });
+    // disc-b: a mood entry with a legacy plaintext note (discoverable).
+    await prisma.moodEntry.create({
+      data: {
+        userId: "disc-b",
+        date: "2026-01-01",
+        mood: "GUT",
+        score: 4,
+        moodLoggedAt: new Date(),
+        note: "legacy plaintext mood note",
+      },
+    });
+    // disc-c: a measurement with NO note (must NOT be discovered).
+    await prisma.measurement.create({
+      data: {
+        userId: "disc-c",
+        type: "WEIGHT",
+        value: 70,
+        unit: "kg",
+        measuredAt: new Date(),
+      },
+    });
+
+    const { boss, sent } = makeCapturingBoss();
+    setGlobalBoss(boss as never);
+    const res = await enqueueBootTimeNoteEncryptionBackfill();
+    expect(res.error).toBeNull();
+    expect(usersFor(sent)).toEqual(["disc-a", "disc-b"]);
+  });
+
+  it("lab-biomarker discovery returns only users with unlinked live results", async () => {
+    const prisma = getPrismaClient();
+    await Promise.all([seedUser("lab-a"), seedUser("lab-b")]);
+    // lab-a: unlinked (biomarkerId null), live → discoverable.
+    await prisma.labResult.create({
+      data: {
+        userId: "lab-a",
+        analyte: "LDL",
+        unit: "mg/dL",
+        takenAt: new Date(),
+      },
+    });
+    // lab-b: unlinked but soft-deleted → excluded by `deleted_at IS NULL`.
+    await prisma.labResult.create({
+      data: {
+        userId: "lab-b",
+        analyte: "HbA1c",
+        unit: "%",
+        takenAt: new Date(),
+        deletedAt: new Date(),
+      },
+    });
+
+    const { boss, sent } = makeCapturingBoss();
+    setGlobalBoss(boss as never);
+    const res = await enqueueBootTimeLabBiomarkerBackfill();
+    expect(res.error).toBeNull();
+    expect(usersFor(sent)).toEqual(["lab-a"]);
+  });
+
+  it("med-notes discovery runs its join SQL cleanly (empty tables → no enqueues)", async () => {
+    // Exercises the three raw statements incl. the dose-changes → medications
+    // JOIN. Empty tables prove the SQL parses + executes against the real
+    // schema (a wrong column/join name would throw here).
+    const { boss, sent } = makeCapturingBoss();
+    setGlobalBoss(boss as never);
+    const res = await enqueueBootTimeMedNotesEncryptionBackfill();
+    expect(res.error).toBeNull();
+    expect(sent).toEqual([]);
+  });
+
+  it("thumbnail discovery applies the mime filter + thumbnail anti-join", async () => {
+    if (!nativeCanvasSupported()) {
+      // The gate returns before the query on a non-AVX2 host; the SQL is still
+      // covered by the other cases' schema, so skip the data assertion here.
+      return;
+    }
+    const prisma = getPrismaClient();
+    await Promise.all([seedUser("doc-a"), seedUser("doc-c")]);
+    // doc-a: a thumbnailable PDF with no thumbnail row → discoverable.
+    await prisma.inboundDocument.create({
+      data: {
+        userId: "doc-a",
+        mimeType: "application/pdf",
+        byteSize: 10,
+        contentEncrypted: Buffer.from("x"),
+      },
+    });
+    // doc-c: a non-thumbnailable text document → excluded by the mime IN filter.
+    await prisma.inboundDocument.create({
+      data: {
+        userId: "doc-c",
+        mimeType: "text/plain",
+        byteSize: 10,
+        contentEncrypted: Buffer.from("x"),
+      },
+    });
+
+    const { boss, sent } = makeCapturingBoss();
+    setGlobalBoss(boss as never);
+    await enqueueBootTimeThumbnailBackfill();
+    expect(usersFor(sent)).toEqual(["doc-a"]);
+  });
+});