diff --git a/services/api/src/db/cursor-helpers.ts b/services/api/src/db/cursor-helpers.ts
index b981c847..6510279e 100644
--- a/services/api/src/db/cursor-helpers.ts
+++ b/services/api/src/db/cursor-helpers.ts
@@ -1,3 +1,5 @@
+import type postgres from "postgres"
+import type { Queryable } from "./client.js"
 
 export const CURSOR_UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i
 
@@ -10,6 +12,10 @@ export interface TimeCursor {
   id: string
 }
 
+export interface DecodedTimeCursor extends TimeCursor {
+  instant: string
+}
+
 export const MIN_UUID = "00000000-0000-0000-0000-000000000000"
 export const MAX_UUID = "ffffffff-ffff-ffff-ffff-ffffffffffff"
 
@@ -19,37 +25,48 @@ export const CURSOR_ISO_RE =
 export const CURSOR_MIN_MS = Date.UTC(1970, 0, 1)
 export const CURSOR_MAX_MS = Date.UTC(2100, 0, 1)
 
-function parseCursorInstant(iso: string): Date | null {
+const CURSOR_FRACTION_RE = /\.(\d{1,6})/
+
+function parseCursorInstant(iso: string): { at: Date; instant: string } | null {
   if (!CURSOR_ISO_RE.test(iso)) return null
   const at = new Date(iso)
   const ms = at.getTime()
   if (!Number.isFinite(ms) || ms < CURSOR_MIN_MS || ms > CURSOR_MAX_MS) return null
-  return at
+  const micros = (CURSOR_FRACTION_RE.exec(iso)?.[1] ?? "").padEnd(6, "0").slice(3)
+  return { at, instant: at.toISOString().replace(/Z$/, `${micros}Z`) }
 }
 
 export function parseTimeCursor(
   cursor: string | null | undefined,
   opts?: { requireUuid?: boolean; direction?: "asc" | "desc" },
-): TimeCursor | null {
+): DecodedTimeCursor | null {
   if (cursor === null || cursor === undefined || cursor === "") return null
   const requireUuid = opts?.requireUuid ?? true
   const idx = cursor.indexOf("|")
   if (idx === 0) return null
   if (idx < 0) {
-    const at = parseCursorInstant(cursor)
-    if (at === null) return null
-    return { at, id: opts?.direction === "asc" ? MIN_UUID : MAX_UUID }
+    const parsed = parseCursorInstant(cursor)
+    if (parsed === null) return null
+    return { ...parsed, id: opts?.direction === "asc" ? MIN_UUID : MAX_UUID }
   }
   const id = cursor.slice(idx + 1)
-  const at = parseCursorInstant(cursor.slice(0, idx))
-  if (at === null) return null
+  const parsed = parseCursorInstant(cursor.slice(0, idx))
+  if (parsed === null) return null
   if (requireUuid && !CURSOR_UUID_RE.test(id)) return null
   if (id.length === 0) return null
-  return { at, id }
+  return { ...parsed, id }
+}
+
+export function encodeTimeCursor(c: { at: Date | string; id: string }): string {
+  return `${typeof c.at === "string" ? c.at : c.at.toISOString()}|${c.id}`
+}
+
+export function cursorInstantSql(sql: Queryable, column: postgres.Fragment): postgres.Fragment {
+  return sql`to_char(${column} AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS.US"Z"')`
 }
 
-export function encodeTimeCursor(c: TimeCursor): string {
-  return `${c.at.toISOString()}|${c.id}`
+export function cursorAtSql(sql: Queryable, cursor: { instant: string }): postgres.Fragment {
+  return sql`${cursor.instant}::text::timestamptz`
 }
 
 export interface NameCursor {
diff --git a/services/api/src/services/admin/inbound-repository.drizzle.ts b/services/api/src/services/admin/inbound-repository.drizzle.ts
index 671f6165..502f6cdf 100644
--- a/services/api/src/services/admin/inbound-repository.drizzle.ts
+++ b/services/api/src/services/admin/inbound-repository.drizzle.ts
@@ -1,5 +1,6 @@
 
 import type { Sql } from "../../db/client.js"
+import { cursorAtSql, cursorInstantSql } from "../../db/cursor-helpers.js"
 import { clampLimit, decodeCursor, encodeCursor } from "./pagination.js"
 import { likeContains } from "./like.js"
 import { writeAudit } from "./audit.js"
@@ -142,7 +143,7 @@ export function makeDrizzleInboundRepository(sql: Sql): InboundRepository {
       const anchor = decodeCursor(query.cursor, true)
       const cursorFilter =
         anchor !== null
-          ? sql`AND (received_at, id) < (${anchor.createdAt}, ${anchor.id}::uuid)`
+          ? sql`AND (received_at, id) < (${cursorAtSql(sql, anchor)}, ${anchor.id}::uuid)`
           : sql``
       const statusFilter =
         query.status === "unread"
@@ -161,11 +162,12 @@ export function makeDrizzleInboundRepository(sql: Sql): InboundRepository {
               return sql`AND (from_addr ILIKE ${like} ESCAPE '\\' OR subject ILIKE ${like} ESCAPE '\\' OR recipient ILIKE ${like} ESCAPE '\\')`
             })()
           : sql``
-      const rows = await sql<InboundListRowSelect[]>`
+      const rows = await sql<(InboundListRowSelect & { cursor_at: string })[]>`
         SELECT id, from_addr, recipient, subject,
                left(body_text, ${PREVIEW_SOURCE_CHARS}) AS preview_text,
                left(body_html, ${HTML_PREVIEW_SOURCE_CHARS}) AS preview_html,
                has_attachments, status, received_at,
+               ${cursorInstantSql(sql, sql`received_at`)} AS cursor_at,
                headers->>${INBOUND_AUTH_VERDICT_HEADER}::text AS auth_verdict
         FROM inbound_emails
         WHERE true
@@ -181,7 +183,7 @@ export function makeDrizzleInboundRepository(sql: Sql): InboundRepository {
       const items = page.map(toListItem)
       const last = page[page.length - 1]
       const nextCursor =
-        hasMore && last ? encodeCursor({ createdAt: last.received_at, id: last.id }) : null
+        hasMore && last ? encodeCursor({ createdAt: last.cursor_at, id: last.id }) : null
       return { items, nextCursor }
     },
 
diff --git a/services/api/src/services/admin/inbox-feed-repository.drizzle.ts b/services/api/src/services/admin/inbox-feed-repository.drizzle.ts
index b4c3ba60..ff7cc7e8 100644
--- a/services/api/src/services/admin/inbox-feed-repository.drizzle.ts
+++ b/services/api/src/services/admin/inbox-feed-repository.drizzle.ts
@@ -1,4 +1,5 @@
 import type { Sql } from "../../db/client.js"
+import { cursorAtSql, cursorInstantSql } from "../../db/cursor-helpers.js"
 import { clampLimit, decodeCursor, encodeCursor } from "./pagination.js"
 import { HTML_PREVIEW_SOURCE_CHARS, PREVIEW_SOURCE_CHARS, toPreview } from "./mail-preview.js"
 import { normalizeAuthVerdict, replyPublication } from "./mail-mappers.js"
@@ -37,12 +38,14 @@ export const INBOX_FEED_REPLY_FILTERS: ReadonlySet<InboxFeedFilter> = new Set([
 export interface InboxFeedEmailRow extends Omit<InboundListRowSelect, "received_at"> {
   source: "email"
   ts: Date
+  cursor_at: string
 }
 
 export interface InboxFeedReplyRow {
   source: "reply"
   id: string
   ts: Date
+  cursor_at: string
   from_addr: string | null
   subject: string | null
   preview_text: string | null
@@ -92,7 +95,7 @@ export function toInboxFeedPage(rows: readonly InboxFeedRow[], limit: number): I
   const hasMore = rows.length > limit && last !== undefined
   return {
     items: page.map(toInboxFeedItem),
-    nextCursor: hasMore ? encodeCursor({ createdAt: last.ts, id: last.id }) : null,
+    nextCursor: hasMore ? encodeCursor({ createdAt: last.cursor_at, id: last.id }) : null,
   }
 }
 
@@ -108,7 +111,7 @@ export function makeDrizzleInboxFeedRepository(sql: Sql): InboxFeedRepository {
       const before = (ts: SqlFragment, id: SqlFragment): SqlFragment =>
         anchor === null
           ? sql``
-          : sql`AND (${ts}, ${id}) < (${anchor.createdAt}, ${anchor.id}::uuid)`
+          : sql`AND (${ts}, ${id}) < (${cursorAtSql(sql, anchor)}, ${anchor.id}::uuid)`
 
       const branches: SqlFragment[] = []
       if (INBOX_FEED_EMAIL_FILTERS.has(filter)) {
@@ -162,7 +165,8 @@ export function makeDrizzleInboxFeedRepository(sql: Sql): InboxFeedRepository {
 
       const union = branches.reduce((acc, branch) => sql`${acc} UNION ALL ${branch}`)
       const rows = await sql<InboxFeedRow[]>`
-        SELECT * FROM (${union}) feed
+        SELECT feed.*, ${cursorInstantSql(sql, sql`feed.ts`)} AS cursor_at
+        FROM (${union}) feed
         ORDER BY ts DESC, id DESC
         LIMIT ${limit + 1}
       `
diff --git a/services/api/src/services/admin/inbox-feed-repository.memory.ts b/services/api/src/services/admin/inbox-feed-repository.memory.ts
index 3bf70bc9..89fbc036 100644
--- a/services/api/src/services/admin/inbox-feed-repository.memory.ts
+++ b/services/api/src/services/admin/inbox-feed-repository.memory.ts
@@ -46,6 +46,7 @@ export class InMemoryInboxFeedRepository implements InboxFeedRepository {
         source: "email",
         id: r.id,
         ts: r.receivedAt,
+        cursor_at: r.receivedAt.toISOString(),
         from_addr: r.fromAddr,
         recipient: r.recipient,
         subject: r.subject,
@@ -70,6 +71,7 @@ export class InMemoryInboxFeedRepository implements InboxFeedRepository {
         source: "reply",
         id: m.id,
         ts: m.createdAt,
+        cursor_at: m.createdAt.toISOString(),
         from_addr: m.fromAddr,
         subject: m.subject ?? t.subject,
         preview_text: m.body,
diff --git a/services/api/src/services/admin/pagination.ts b/services/api/src/services/admin/pagination.ts
index ba89d4dc..196d5fb4 100644
--- a/services/api/src/services/admin/pagination.ts
+++ b/services/api/src/services/admin/pagination.ts
@@ -22,8 +22,12 @@ export interface CursorAnchor {
   id: string
 }
 
+export interface DecodedCursorAnchor extends CursorAnchor {
+  instant: string
+}
+
 /** Encode a keyset anchor into the opaque "<iso>|<id>" cursor string. */
-export function encodeCursor(anchor: CursorAnchor): string {
+export function encodeCursor(anchor: { createdAt: Date | string; id: string }): string {
   return encodeTimeCursor({ at: anchor.createdAt, id: anchor.id })
 }
 
@@ -38,10 +42,10 @@ export function encodeCursor(anchor: CursorAnchor): string {
 export function decodeCursor(
   cursor: string | null | undefined,
   requireUuidId = false,
-): CursorAnchor | null {
+): DecodedCursorAnchor | null {
   const parsed = parseTimeCursor(cursor, { requireUuid: requireUuidId })
   if (parsed === null) return null
-  return { createdAt: parsed.at, id: parsed.id }
+  return { createdAt: parsed.at, id: parsed.id, instant: parsed.instant }
 }
 
 /**
diff --git a/services/api/test/integration/inbound-repository.test.ts b/services/api/test/integration/inbound-repository.test.ts
index d74c693a..c47a9b09 100644
--- a/services/api/test/integration/inbound-repository.test.ts
+++ b/services/api/test/integration/inbound-repository.test.ts
@@ -80,6 +80,25 @@ describe.skipIf(!pg)("inbound repository (integration: real schema)", () => {
     expect(onlySupport.items).toHaveLength(2)
   })
 
+  it("pages rows that share a millisecond by their microseconds, skipping none", async () => {
+    for (const micros of ["123100", "123500", "123900"]) {
+      const { id } = await repo.insertIdempotent(insert({ messageId: `<us-${micros}@x>` }))
+      await h.sql`
+        UPDATE inbound_emails SET received_at = ${`2027-01-01T00:00:00.${micros}Z`}::text::timestamptz
+        WHERE id = ${id}
+      `
+    }
+    const walked: string[] = []
+    let cursor: string | undefined
+    do {
+      const page = await repo.list({ limit: 1, ...(cursor === undefined ? {} : { cursor }) })
+      walked.push(...page.items.map((i) => i.id))
+      cursor = page.nextCursor ?? undefined
+    } while (cursor !== undefined)
+    expect(walked).toEqual((await repo.list({})).items.map((i) => i.id))
+    expect(walked).toHaveLength(3)
+  })
+
   it("reads the stored auth verdict onto list rows and the detail", async () => {
     const headers = { "x-civfix-auth-verdict": "fail" }
     const r = await repo.insertIdempotent(insert({ messageId: "<verdict@x>", headers }))
diff --git a/services/api/test/integration/inbox-feed-repository.test.ts b/services/api/test/integration/inbox-feed-repository.test.ts
index 3313a26e..9135de7c 100644
--- a/services/api/test/integration/inbox-feed-repository.test.ts
+++ b/services/api/test/integration/inbox-feed-repository.test.ts
@@ -153,4 +153,24 @@ describe.skipIf(!pg)("inbox feed repository (integration: real schema)", () => {
     expect(all).toHaveLength(6)
     expect(all.slice(0, 2).sort().reverse()).toEqual(all.slice(0, 2))
   })
+
+  it("walks rows that share a millisecond by their microseconds, skipping none", async () => {
+    const s = await mailbox()
+    const microsecond = (micros: string) => `2027-01-01T00:00:00.${micros}Z`
+    await h.sql`UPDATE inbound_emails SET received_at = ${microsecond("123100")}::text::timestamptz`
+    await h.sql`
+      UPDATE mail_messages SET created_at = ${microsecond("123500")}::text::timestamptz
+      WHERE id IN (${s.withheld!}, ${s.published!})
+    `
+    const all = await ids({})
+    const walked: string[] = []
+    let cursor: string | null = null
+    do {
+      const page = await feed.list({ limit: 1, ...(cursor === null ? {} : { cursor }) })
+      walked.push(...page.items.map((i) => i.id))
+      cursor = page.nextCursor
+    } while (cursor !== null)
+    expect(walked).toEqual(all)
+    expect(all).toHaveLength(5)
+  })
 })
diff --git a/services/api/test/unit/admin-inbox-keyset.test.ts b/services/api/test/unit/admin-inbox-keyset.test.ts
new file mode 100644
index 00000000..8e754724
--- /dev/null
+++ b/services/api/test/unit/admin-inbox-keyset.test.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest"
+import type { Sql } from "../../src/db/client.js"
+import { makeFakeSql } from "../helpers/fake-sql.js"
+import { makeDrizzleInboundRepository } from "../../src/services/admin/inbound-repository.drizzle.js"
+import { makeDrizzleInboxFeedRepository } from "../../src/services/admin/inbox-feed-repository.drizzle.js"
+
+const A = "aaaaaaaa-0000-4000-8000-000000000001"
+const B = "aaaaaaaa-0000-4000-8000-000000000002"
+const TS = new Date("2027-01-01T00:00:00.123Z")
+const INSTANT = "2027-01-01T00:00:00.123456Z"
+
+const emailRow = (id: string) => ({
+  source: "email",
+  id,
+  ts: TS,
+  received_at: TS,
+  cursor_at: INSTANT,
+  from_addr: "resident@example.com",
+  recipient: "support@civfix.org",
+  subject: "Probe",
+  preview_text: "Hello",
+  preview_html: null,
+  has_attachments: false,
+  status: "unread",
+  auth_verdict: null,
+})
+
+const repos = {
+  "the inbox feed": (sql: Sql) => makeDrizzleInboxFeedRepository(sql),
+  "the unmatched inbox": (sql: Sql) => makeDrizzleInboundRepository(sql),
+}
+
+describe.each(Object.entries(repos))("%s keyset", (_name, make) => {
+  it("pages from the row's microsecond instant, not its millisecond Date", async () => {
+    const db = makeFakeSql([{ match: /inbound_emails/, rows: [emailRow(A), emailRow(B)] }])
+    const repo = make(db.sql as unknown as Sql)
+
+    const first = await repo.list({ limit: 1 })
+    expect(first.nextCursor).toBe(`${INSTANT}|${A}`)
+
+    await repo.list({ limit: 1, cursor: first.nextCursor! })
+    const next = db.statements.at(-1)!
+    expect(next.values).toContain(INSTANT)
+    expect(next.values).not.toContainEqual(TS)
+    expect(next.sql).toContain("?::text::timestamptz")
+  })
+})
diff --git a/services/api/test/unit/cursor-helpers.test.ts b/services/api/test/unit/cursor-helpers.test.ts
index 4e6c5df9..daae2d20 100644
--- a/services/api/test/unit/cursor-helpers.test.ts
+++ b/services/api/test/unit/cursor-helpers.test.ts
@@ -18,6 +18,7 @@ import {
 const UUID = "3f2504e0-4f89-11d3-9a0c-0305e82c3301"
 const UUID_2 = "9c858901-8a57-4791-81fe-4c455b099bc9"
 const ISO = "2026-07-24T12:34:56.789Z"
+const INSTANT = "2026-07-24T12:34:56.789000Z"
 
 describe("isUuid / CURSOR_UUID_RE", () => {
   it("accepts a canonical uuid in either case and rejects near-misses", () => {
@@ -53,10 +54,26 @@ describe("parseTimeCursor", () => {
     expect(parsed!.id).toBe(original.id)
   })
 
+  it("keeps the cursor's microseconds as the instant the database compares against", () => {
+    const parsed = parseTimeCursor(`2026-07-24T12:34:56.789123Z|${UUID}`)
+    expect(parsed?.at.toISOString()).toBe(ISO)
+    expect(parsed?.instant).toBe("2026-07-24T12:34:56.789123Z")
+    expect(parseTimeCursor(`2026-07-24T14:34:56.7+02:00|${UUID}`)?.instant).toBe(
+      "2026-07-24T12:34:56.700000Z",
+    )
+  })
+
+  it("encodes a database instant verbatim, so its microseconds survive the round trip", () => {
+    const encoded = encodeTimeCursor({ at: "2026-07-24T12:34:56.789123Z", id: UUID })
+    expect(encoded).toBe(`2026-07-24T12:34:56.789123Z|${UUID}`)
+    expect(parseTimeCursor(encoded)?.instant).toBe("2026-07-24T12:34:56.789123Z")
+  })
+
   it("anchors a legacy timestamp-only cursor with a DIRECTION-AWARE sentinel so no boundary row is skipped", () => {
-    expect(parseTimeCursor(ISO)).toEqual({ at: new Date(ISO), id: MAX_UUID })
-    expect(parseTimeCursor(ISO, { direction: "desc" })).toEqual({ at: new Date(ISO), id: MAX_UUID })
-    expect(parseTimeCursor(ISO, { direction: "asc" })).toEqual({ at: new Date(ISO), id: MIN_UUID })
+    const anchor = { at: new Date(ISO), instant: INSTANT }
+    expect(parseTimeCursor(ISO)).toEqual({ ...anchor, id: MAX_UUID })
+    expect(parseTimeCursor(ISO, { direction: "desc" })).toEqual({ ...anchor, id: MAX_UUID })
+    expect(parseTimeCursor(ISO, { direction: "asc" })).toEqual({ ...anchor, id: MIN_UUID })
     expect(isUuid(parseTimeCursor(ISO)!.id)).toBe(true)
     expect(isUuid(parseTimeCursor(ISO, { direction: "asc" })!.id)).toBe(true)
   })
@@ -86,7 +103,7 @@ describe("parseTimeCursor", () => {
 
   it("with requireUuid:false accepts a non-uuid id, but still rejects an EMPTY one", () => {
     const parsed = parseTimeCursor(`${ISO}|room-42`, { requireUuid: false })
-    expect(parsed).toEqual({ at: new Date(ISO), id: "room-42" })
+    expect(parsed).toEqual({ at: new Date(ISO), instant: INSTANT, id: "room-42" })
     expect(parseTimeCursor(`${ISO}|`, { requireUuid: false })).toBeNull()
     expect(parseTimeCursor("nope|room-42", { requireUuid: false })).toBeNull()
   })
@@ -232,7 +249,11 @@ describe("paginate", () => {
     const page = paginate(rows, 1, (r) => ({ at: r.at, id: r.id }))
     expect(page.items).toEqual([rows[0]])
     expect(page.nextCursor).toBe(`${ISO}|${UUID}`)
-    expect(parseTimeCursor(page.nextCursor)).toEqual({ at: new Date(ISO), id: UUID })
+    expect(parseTimeCursor(page.nextCursor)).toEqual({
+      at: new Date(ISO),
+      instant: INSTANT,
+      id: UUID,
+    })
   })
 
   it("falls back to `createdAt` when the anchor has no `at`", () => {