diff --git a/src/hooks/useAckClaims.test.ts b/src/hooks/useAckClaims.test.ts
new file mode 100644
index 0000000..235b3f7
--- /dev/null
+++ b/src/hooks/useAckClaims.test.ts
@@ -0,0 +1,188 @@
+// @vitest-environment happy-dom
+// React Query's internal state updates need an `act`-aware environment
+// or it logs noisy warnings. Mirror the useClaimDetail /
+// useClaimAcks / useTailStream test convention.
+(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+
+import React, { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { useAckClaims } from "./useAckClaims";
+import { api } from "@/lib/api";
+
+// Module-level mock: vitest hoists `vi.mock` above imports. We mock the
+// single `api.listAckClaims` method the hook calls.
+vi.mock("@/lib/api", () => ({
+  api: {
+    listAckClaims: vi.fn(),
+  },
+}));
+
+/** Minimal `renderHook` shim — same pattern as `useClaimAcks.test.ts`. */
+function renderHook<TResult>(
+  useCallback: () => TResult
+): {
+  result: { current: TResult | undefined };
+  unmount: () => void;
+} {
+  const result: { current: TResult | undefined } = { current: undefined };
+  const container = document.createElement("div");
+  document.body.appendChild(container);
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+
+  function Probe() {
+    result.current = useCallback();
+    return null;
+  }
+
+  const root: Root = createRoot(container);
+  act(() => {
+    root.render(
+      React.createElement(QueryClientProvider, { client: qc }, React.createElement(Probe))
+    );
+  });
+
+  return {
+    result,
+    unmount: () => {
+      act(() => root.unmount());
+      container.remove();
+    },
+  };
+}
+
+/** Poll the result until `predicate` is true or we time out. */
+async function waitForState(
+  predicate: () => boolean,
+  timeoutMs = 1000
+): Promise<void> {
+  const start = Date.now();
+  while (!predicate()) {
+    if (Date.now() - start > timeoutMs) {
+      throw new Error(
+        `waitForState: predicate did not hold within ${timeoutMs}ms`,
+      );
+    }
+    await act(async () => {
+      await Promise.resolve();
+    });
+  }
+}
+
+/** Sample fixture — one 999 with two AK2 set-responses, both auto-linked
+ * to the same claim. Mirrors the camelCase `ClaimAck` shape (the api
+ * layer's `mapClaimAck` does the snake_case→camelCase conversion). */
+const SAMPLE_ROWS = [
+  {
+    id: 11,
+    claimId: "CLM-1",
+    batchId: null,
+    ackId: 99,
+    ackKind: "999" as const,
+    ak2Index: 0,
+    setControlNumber: "991102989",
+    setAcceptRejectCode: "A",
+    linkedAt: "2026-07-02T12:00:00Z",
+    linkedBy: "auto" as const,
+    claimState: "received",
+  },
+  {
+    id: 12,
+    claimId: "CLM-1",
+    batchId: null,
+    ackId: 99,
+    ackKind: "999" as const,
+    ak2Index: 1,
+    setControlNumber: "991102990",
+    setAcceptRejectCode: "R",
+    linkedAt: "2026-07-02T12:00:01Z",
+    linkedBy: "auto" as const,
+    claimState: "received",
+  },
+];
+
+describe("useAckClaims", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("test_returns_idle_state_and_does_not_fetch_when_ackId_is_null", () => {
+    // Drawer closed → no network call, no loading, no error. The hook
+    // must short-circuit BEFORE the queryFn is ever invoked so a
+    // closed drawer is free.
+    const { result, unmount } = renderHook(() => useAckClaims("999", null));
+
+    expect(result.current).toBeDefined();
+    expect(result.current?.data).toBeNull();
+    expect(result.current?.isLoading).toBe(false);
+    expect(result.current?.isError).toBe(false);
+    expect(result.current?.error).toBeNull();
+    expect(typeof result.current?.refetch).toBe("function");
+    expect(api.listAckClaims).not.toHaveBeenCalled();
+
+    unmount();
+  });
+
+  it("test_returns_idle_state_and_does_not_fetch_when_kind_is_null", () => {
+    // Defensive — the hook accepts `kind: ClaimAckKind | null` and
+    // short-circuits when it's null (mirrors the ackId null check).
+    const { result, unmount } = renderHook(() => useAckClaims(null, 42));
+
+    expect(result.current?.data).toBeNull();
+    expect(result.current?.isLoading).toBe(false);
+    expect(api.listAckClaims).not.toHaveBeenCalled();
+
+    unmount();
+  });
+
+  it("test_fetches_and_returns_claim_ack_rows_for_a_valid_ack", async () => {
+    (api.listAckClaims as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      SAMPLE_ROWS,
+    );
+
+    const { result, unmount } = renderHook(() => useAckClaims("999", 99));
+
+    await waitForState(
+      () => result.current?.data !== null && result.current?.data !== undefined,
+    );
+
+    // The hook must have invoked the API exactly once with the kind+id.
+    expect(api.listAckClaims).toHaveBeenCalledTimes(1);
+    expect(api.listAckClaims).toHaveBeenCalledWith("999", 99);
+
+    const data = result.current?.data;
+    expect(data).not.toBeNull();
+    expect(data).toHaveLength(2);
+    // Both rows belong to the same ack (per-AK2 granularity for 999).
+    expect(data?.[0]?.ackId).toBe(99);
+    expect(data?.[0]?.ackKind).toBe("999");
+    expect(data?.[0]?.ak2Index).toBe(0);
+    expect(data?.[1]?.ak2Index).toBe(1);
+
+    // isLoading must flip false once the fetch resolves.
+    expect(result.current?.isLoading).toBe(false);
+    expect(result.current?.isError).toBe(false);
+
+    unmount();
+  });
+
+  it("test_returns_empty_array_when_ack_has_no_claim_links", async () => {
+    (api.listAckClaims as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      [],
+    );
+
+    const { result, unmount } = renderHook(() => useAckClaims("999", 77));
+
+    await waitForState(
+      () => result.current?.data !== null && result.current?.data !== undefined,
+    );
+
+    // Empty list must be surfaced as [] (NOT null), so the AckDrawer
+    // panel can render its "Link to claim…" dropdown without a null
+    // check.
+    expect(result.current?.data).toEqual([]);
+
+    unmount();
+  });
+});
\ No newline at end of file
diff --git a/src/hooks/useAckClaims.ts b/src/hooks/useAckClaims.ts
new file mode 100644
index 0000000..a3bb788
--- /dev/null
+++ b/src/hooks/useAckClaims.ts
@@ -0,0 +1,80 @@
+import { useQuery } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { ClaimAck, ClaimAckKind } from "@/types";
+
+/**
+ * Per-ack claims query (AckDrawer · SP28 §5.2).
+ *
+ * Lists every `claim_acks` row for the given ack. For 999/277CA,
+ * one entry per AK2 / ClaimStatus (D1 per-AK2 granularity). For
+ * TA1, one entry per envelope linked to the originating `Batch`.
+ * Drives the new `<MatchedClaim />` panel inside `AckDrawer`.
+ *
+ * Returns `{ data, isLoading, isError, error, refetch }`:
+ *  - `ackId === null` (drawer closed): the query is disabled and the
+ *    hook short-circuits to the empty drawer state `{ data: null, ... }`
+ *    so a closed drawer doesn't burn a network request or a TanStack
+ *    cache slot. The `AckDrawer` panel guards the `data ?? []` access
+ *    on this and renders the "Link to claim…" dropdown when the list
+ *    is empty.
+ *  - `kind` and `ackId` set: fetches
+ *    `GET /api/acks/{kind}/{ack_id}/claims` via `api.listAckClaims`.
+ *    Cached 30 s — the link rows don't change once created (only
+ *    manual-match / unlink mutate them, and those fire
+ *    `claim_ack_written` / `claim_ack_dropped` events that the
+ *    live-tail subscription delivers via `useTailStream("claim-acks")`).
+ *  - On 404: the hook's retry predicate short-circuits (no retries)
+ *    so the drawer's not-found state appears immediately rather than
+ *    being masked by three back-to-back retry attempts.
+ *
+ * The live-tail subscription (`useTailStream("claim-acks")` +
+ * `useMergedTail("claim-acks", data ?? [], (link) => link.ackId === ackId)`)
+ * is mounted by the `AckDrawer` itself (per
+ * `cyclone-frontend-page` convention #3 — subscription on the page,
+ * not in the hook).
+ */
+export function useAckClaims(
+  kind: ClaimAckKind | null,
+  ackId: number | null,
+): {
+  data: ClaimAck[] | null;
+  isLoading: boolean;
+  isError: boolean;
+  error: Error | null;
+  refetch: () => void;
+} {
+  const q = useQuery<ClaimAck[]>({
+    queryKey: ["ack-claims", kind, ackId],
+    queryFn: () => api.listAckClaims(kind as ClaimAckKind, ackId as number),
+    enabled: kind !== null && ackId !== null,
+    staleTime: 30 * 1000,
+    retry: (failureCount, error) => {
+      // Don't retry 404 — same posture as the other detail hooks.
+      if (error instanceof Error && "status" in error) {
+        const status = (error as { status?: unknown }).status;
+        if (status === 404) return false;
+      }
+      return failureCount < 3;
+    },
+  });
+
+  if (kind === null || ackId === null) {
+    return {
+      data: null,
+      isLoading: false,
+      isError: false,
+      error: null,
+      refetch: () => {},
+    };
+  }
+
+  return {
+    data: q.data ?? null,
+    isLoading: q.isLoading,
+    isError: q.isError,
+    error: q.error,
+    refetch: () => {
+      void q.refetch();
+    },
+  };
+}
\ No newline at end of file
diff --git a/src/hooks/useClaimAcks.test.ts b/src/hooks/useClaimAcks.test.ts
new file mode 100644
index 0000000..a03395a
--- /dev/null
+++ b/src/hooks/useClaimAcks.test.ts
@@ -0,0 +1,176 @@
+// @vitest-environment happy-dom
+// React Query's internal state updates need an `act`-aware environment
+// or it logs noisy warnings. Mirror the useClaimDetail /
+// useReconciliation / useTailStream test convention.
+(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+
+import React, { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { describe, expect, it, vi, beforeEach } from "vitest";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { useClaimAcks } from "./useClaimAcks";
+import { api } from "@/lib/api";
+
+// Module-level mock: vitest hoists `vi.mock` above imports. We mock the
+// single `api.listClaimAcks` method the hook calls.
+vi.mock("@/lib/api", () => ({
+  api: {
+    listClaimAcks: vi.fn(),
+  },
+}));
+
+/** Minimal `renderHook` shim — same pattern as `useClaimDetail.test.ts`. */
+function renderHook<TResult>(
+  useCallback: () => TResult
+): {
+  result: { current: TResult | undefined };
+  unmount: () => void;
+} {
+  const result: { current: TResult | undefined } = { current: undefined };
+  const container = document.createElement("div");
+  document.body.appendChild(container);
+  const qc = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+
+  function Probe() {
+    result.current = useCallback();
+    return null;
+  }
+
+  const root: Root = createRoot(container);
+  act(() => {
+    root.render(
+      React.createElement(QueryClientProvider, { client: qc }, React.createElement(Probe))
+    );
+  });
+
+  return {
+    result,
+    unmount: () => {
+      act(() => root.unmount());
+      container.remove();
+    },
+  };
+}
+
+/** Poll the result until `predicate` is true or we time out. */
+async function waitForState(
+  predicate: () => boolean,
+  timeoutMs = 1000
+): Promise<void> {
+  const start = Date.now();
+  while (!predicate()) {
+    if (Date.now() - start > timeoutMs) {
+      throw new Error(
+        `waitForState: predicate did not hold within ${timeoutMs}ms`,
+      );
+    }
+    await act(async () => {
+      await Promise.resolve();
+    });
+  }
+}
+
+/** Sample fixture matching the camelCase `ClaimAck` shape (the api
+ * layer's `mapClaimAck` does the snake_case→camelCase conversion, so
+ * the mock returns the post-conversion shape directly). */
+const SAMPLE_ROWS = [
+  {
+    id: 1,
+    claimId: "CLM-1",
+    batchId: null,
+    ackId: 99,
+    ackKind: "999" as const,
+    ak2Index: 0,
+    setControlNumber: "991102989",
+    setAcceptRejectCode: "A",
+    linkedAt: "2026-07-02T12:00:00Z",
+    linkedBy: "auto" as const,
+    claimState: "received",
+  },
+  {
+    id: 2,
+    claimId: "CLM-1",
+    batchId: null,
+    ackId: 99,
+    ackKind: "999" as const,
+    ak2Index: 1,
+    setControlNumber: "991102990",
+    setAcceptRejectCode: "R",
+    linkedAt: "2026-07-02T12:00:01Z",
+    linkedBy: "auto" as const,
+    claimState: "received",
+  },
+];
+
+describe("useClaimAcks", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("test_returns_idle_state_and_does_not_fetch_when_claimId_is_null", () => {
+    // Drawer closed → no network call, no loading, no error. The hook
+    // must short-circuit BEFORE the queryFn is ever invoked so a
+    // closed drawer is free.
+    const { result, unmount } = renderHook(() => useClaimAcks(null));
+
+    expect(result.current).toBeDefined();
+    expect(result.current?.data).toBeNull();
+    expect(result.current?.isLoading).toBe(false);
+    expect(result.current?.isError).toBe(false);
+    expect(result.current?.error).toBeNull();
+    expect(typeof result.current?.refetch).toBe("function");
+    expect(api.listClaimAcks).not.toHaveBeenCalled();
+
+    unmount();
+  });
+
+  it("test_fetches_and_returns_claim_ack_rows_for_a_valid_claim_id", async () => {
+    (api.listClaimAcks as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      SAMPLE_ROWS,
+    );
+
+    const { result, unmount } = renderHook(() => useClaimAcks("CLM-1"));
+
+    await waitForState(
+      () => result.current?.data !== null && result.current?.data !== undefined,
+    );
+
+    // The hook must have invoked the API exactly once with the claim id.
+    expect(api.listClaimAcks).toHaveBeenCalledTimes(1);
+    expect(api.listClaimAcks).toHaveBeenCalledWith("CLM-1");
+
+    const data = result.current?.data;
+    expect(data).not.toBeNull();
+    expect(data).toHaveLength(2);
+    // Both rows belong to the same claim (per-AK2 granularity for 999).
+    expect(data?.[0]?.claimId).toBe("CLM-1");
+    expect(data?.[0]?.ackKind).toBe("999");
+    expect(data?.[0]?.setAcceptRejectCode).toBe("A");
+    expect(data?.[1]?.setAcceptRejectCode).toBe("R");
+    expect(data?.[1]?.ak2Index).toBe(1);
+
+    // isLoading must flip false once the fetch resolves.
+    expect(result.current?.isLoading).toBe(false);
+    expect(result.current?.isError).toBe(false);
+
+    unmount();
+  });
+
+  it("test_returns_empty_array_when_claim_has_no_acks", async () => {
+    (api.listClaimAcks as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      [],
+    );
+
+    const { result, unmount } = renderHook(() => useClaimAcks("CLM-empty"));
+
+    await waitForState(
+      () => result.current?.data !== null && result.current?.data !== undefined,
+    );
+
+    // Empty list must be surfaced as [] (NOT null), so the ClaimDrawer
+    // panel can render its <EmptyState /> without a null check.
+    expect(result.current?.data).toEqual([]);
+
+    unmount();
+  });
+});
\ No newline at end of file
diff --git a/src/hooks/useClaimAcks.ts b/src/hooks/useClaimAcks.ts
new file mode 100644
index 0000000..29c27fe
--- /dev/null
+++ b/src/hooks/useClaimAcks.ts
@@ -0,0 +1,77 @@
+import { useQuery } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { ClaimAck } from "@/types";
+
+/**
+ * Per-claim acknowledgments query (ClaimDrawer · SP28 §5.1).
+ *
+ * Lists every `claim_acks` row for the given claim (per-claim only —
+ * the backend filters out TA1 batch-level rows with
+ * `claim_id IS NULL`). Drives the new `<Acknowledgments />` panel
+ * inside `ClaimDrawer`.
+ *
+ * Returns `{ data, isLoading, isError, error, refetch }`:
+ *  - `claimId === null` (drawer closed): the query is disabled and the
+ *    hook short-circuits to `{ data: null, ... }` so a closed drawer
+ *    doesn't burn a network request or a TanStack cache slot. The
+ *    `ClaimDrawer` panel guards the `data ?? []` access on this.
+ *  - `claimId` is set: fetches
+ *    `GET /api/claims/{claim_id}/acks` via `api.listClaimAcks`.
+ *    Cached 30 s — the link rows don't change once created (only
+ *    manual-match / unlink mutate them, and those fire
+ *    `claim_ack_written` / `claim_ack_dropped` events that the
+ *    live-tail subscription delivers via `useTailStream("claim-acks")`).
+ *  - On 404: the hook's retry predicate short-circuits (no retries)
+ *    so the drawer's not-found state appears immediately rather than
+ *    being masked by three back-to-back retry attempts.
+ *
+ * The live-tail subscription (`useTailStream("claim-acks")` +
+ * `useMergedTail("claim-acks", data ?? [], (link) => link.claimId === claimId)`)
+ * is mounted by the `ClaimDrawer` itself (per
+ * `cyclone-frontend-page` convention #3 — subscription on the page,
+ * not in the hook).
+ */
+export function useClaimAcks(claimId: string | null): {
+  data: ClaimAck[] | null;
+  isLoading: boolean;
+  isError: boolean;
+  error: Error | null;
+  refetch: () => void;
+} {
+  const q = useQuery<ClaimAck[]>({
+    queryKey: ["claim-acks", claimId],
+    queryFn: () => api.listClaimAcks(claimId as string),
+    enabled: claimId !== null,
+    staleTime: 30 * 1000,
+    retry: (failureCount, error) => {
+      // Don't retry 404 — same posture as the other detail hooks. The
+      // drawer treats 404 as a distinct "claim doesn't exist" state
+      // and doesn't want retries masking it.
+      if (error instanceof Error && "status" in error) {
+        const status = (error as { status?: unknown }).status;
+        if (status === 404) return false;
+      }
+      return failureCount < 3;
+    },
+  });
+
+  if (claimId === null) {
+    return {
+      data: null,
+      isLoading: false,
+      isError: false,
+      error: null,
+      refetch: () => {},
+    };
+  }
+
+  return {
+    data: q.data ?? null,
+    isLoading: q.isLoading,
+    isError: q.isError,
+    error: q.error,
+    refetch: () => {
+      void q.refetch();
+    },
+  };
+}
\ No newline at end of file
diff --git a/src/lib/api.ts b/src/lib/api.ts
index 3bc94e6..8a55db9 100644
--- a/src/lib/api.ts
+++ b/src/lib/api.ts
@@ -25,6 +25,8 @@
 import type {
   Ack,
   BatchDiff,
+  ClaimAck,
+  ClaimAckKind,
   ClaimDetail,
   ClaimOutput,
   ClaimPayment,
@@ -855,6 +857,11 @@ interface RawAckRow {
   received_count: number;
   ack_code: "A" | "E" | "R" | "P";
   parsed_at: string;
+  /**
+   * SP28: distinct claim ids this 999 ack is linked to. Empty
+   * array when the auto-linker couldn't resolve (orphan).
+   */
+  linked_claim_ids?: string[];
 }
 
 function mapAck(row: RawAckRow): Ack {
@@ -866,6 +873,7 @@ function mapAck(row: RawAckRow): Ack {
     receivedCount: row.received_count,
     ackCode: row.ack_code,
     parsedAt: row.parsed_at,
+    linkedClaimIds: row.linked_claim_ids ?? [],
   };
 }
 
@@ -930,6 +938,11 @@ interface RawTa1Row {
   receiver_id: string | null;
   source_batch_id: string;
   parsed_at: string | null;
+  /**
+   * SP28: originating `Batch` ids this TA1 envelope is linked to.
+   * Empty array when the auto-linker couldn't resolve (orphan).
+   */
+  linked_claim_ids?: string[];
 }
 
 function mapTa1Ack(row: RawTa1Row): Ta1Ack {
@@ -944,6 +957,7 @@ function mapTa1Ack(row: RawTa1Row): Ta1Ack {
     receiverId: row.receiver_id,
     sourceBatchId: row.source_batch_id,
     parsedAt: row.parsed_at,
+    linkedClaimIds: row.linked_claim_ids ?? [],
   };
 }
 
@@ -969,6 +983,164 @@ async function listTa1Acks(
   };
 }
 
+// ---------------------------------------------------------------------------
+// SP28: claim↔ack link rows.
+// The `claim_acks` table is the durable record of which 999 / 277CA / TA1
+// acknowledged which claim (or, for TA1, which originating 837 `Batch`).
+// Three read endpoints (`listClaimAcks`, `listAckClaims`, `listAckOrphans`)
+// plus the manual-match + unmatch write endpoints. The wire shape mirrors
+// `to_ui_claim_ack` (backend/src/cyclone/store/ui.py) — camelCase keys,
+// ISO Z timestamps, numeric ids from the database row.
+// ---------------------------------------------------------------------------
+
+interface RawClaimAckRow {
+  id: number;
+  claim_id: string | null;
+  batch_id: string | null;
+  ack_id: number;
+  ack_kind: ClaimAckKind;
+  ak2_index: number | null;
+  set_control_number: string | null;
+  set_accept_reject_code: string | null;
+  linked_at: string;
+  linked_by: "auto" | "manual";
+  claim_state?: string;
+}
+
+function mapClaimAck(row: RawClaimAckRow): ClaimAck {
+  return {
+    id: row.id,
+    claimId: row.claim_id,
+    batchId: row.batch_id,
+    ackId: row.ack_id,
+    ackKind: row.ack_kind,
+    ak2Index: row.ak2_index,
+    setControlNumber: row.set_control_number,
+    setAcceptRejectCode: row.set_accept_reject_code,
+    linkedAt: row.linked_at,
+    linkedBy: row.linked_by,
+    claimState: row.claim_state,
+  };
+}
+
+/**
+ * `GET /api/claims/{claim_id}/acks` — list every `claim_acks` row
+ * for the given claim (per-claim only; TA1 batch-level rows with
+ * `claim_id IS NULL` are filtered out by the backend).
+ *
+ * Drives `ClaimDrawer`'s new `<Acknowledgments />` panel. Returns
+ * an array even on the empty case — the panel renders
+ * `<EmptyState />` when the list is empty (no live-tail data).
+ */
+async function listClaimAcks(claimId: string): Promise<ClaimAck[]> {
+  if (!isConfigured) throw notConfiguredError();
+  const body = await authedFetch<{ items: RawClaimAckRow[] }>(
+    `/api/claims/${encodeURIComponent(claimId)}/acks`,
+  );
+  return body.items.map(mapClaimAck);
+}
+
+/**
+ * `GET /api/acks/{kind}/{ack_id}/claims` — list every `claim_acks`
+ * row for the given ack. For 999/277CA, one entry per AK2 /
+ * ClaimStatus (D1 per-AK2 granularity). For TA1, one entry per
+ * envelope linked to the originating `Batch`.
+ *
+ * Drives `AckDrawer`'s new `<MatchedClaim />` panel. Returns an
+ * array; the panel renders the "Link to claim…" dropdown when the
+ * list is empty (no auto-link resolved).
+ */
+async function listAckClaims(
+  kind: ClaimAckKind,
+  ackId: number,
+): Promise<ClaimAck[]> {
+  if (!isConfigured) throw notConfiguredError();
+  const body = await authedFetch<{ items: RawClaimAckRow[] }>(
+    `/api/acks/${encodeURIComponent(kind)}/${encodeURIComponent(String(ackId))}/claims`,
+  );
+  return body.items.map(mapClaimAck);
+}
+
+/**
+ * `POST /api/acks/{kind}/{ack_id}/match-claim` — manual-match fallback
+ * (D5). Any logged-in user can run this (D9 differs explicitly from
+ * the admin-only remit-orphans posture — the metadata-only nature of
+ * an ack link doesn't warrant admin gating).
+ *
+ * Idempotent on the server: re-running with the same `claim_id`
+ * returns the existing row with HTTP 200. Returns 409 if the target
+ * claim is in a terminal state (REVERSED).
+ */
+async function matchAckToClaim(
+  kind: ClaimAckKind,
+  ackId: number,
+  claimId: string,
+): Promise<ClaimAck> {
+  if (!isConfigured) throw notConfiguredError();
+  const body = await authedFetch<RawClaimAckRow>(
+    `/api/acks/${encodeURIComponent(kind)}/${encodeURIComponent(String(ackId))}/match-claim`,
+    {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ claim_id: claimId }),
+    },
+  );
+  return mapClaimAck(body);
+}
+
+/**
+ * `DELETE /api/acks/{kind}/{ack_id}/match-claim/{claim_id}` — unlink.
+ * Removes the `claim_acks` row and publishes a `claim_ack_dropped`
+ * event; does NOT revert any `Claim.state` mutation the ack may
+ * have triggered (e.g. an `apply_999_rejections` flip to REJECTED
+ * stays — unlinking is metadata-only, per spec §D5/§D6).
+ */
+async function unmatchAck(
+  kind: ClaimAckKind,
+  ackId: number,
+  claimId: string,
+): Promise<void> {
+  if (!isConfigured) throw notConfiguredError();
+  await authedFetch<void>(
+    `/api/acks/${encodeURIComponent(kind)}/${encodeURIComponent(String(ackId))}/match-claim/${encodeURIComponent(claimId)}`,
+    { method: "DELETE" },
+  );
+}
+
+/**
+ * One row in the Inbox "Ack orphans" lane (D7). Mirrors the wire
+ * shape of `GET /api/inbox/ack-orphans?kind=…`. ``candidates`` is a
+ * top-3 list of relaxed PCN matches so the operator can decide
+ * whether to dismiss or manually link.
+ */
+export interface AckOrphanRow {
+  id: number;
+  kind: ClaimAckKind;
+  pcn: string;
+  sourceBatchId: string;
+  parsedAt: string;
+  candidates: Array<{
+    claimId: string;
+    score: number;
+    tier: "strong" | "weak" | "hidden";
+  }>;
+}
+
+/**
+ * `GET /api/inbox/ack-orphans?kind=…` — list acks that the
+ * auto-linker couldn't resolve to a claim. Powers the Inbox
+ * "Ack orphans" lane (mirrors the existing "Payer-rejected" lane
+ * shape; D7).
+ */
+async function listAckOrphans(kind: ClaimAckKind): Promise<AckOrphanRow[]> {
+  if (!isConfigured) throw notConfiguredError();
+  const body = await authedFetch<{
+    items: AckOrphanRow[];
+    total: number;
+  }>(`/api/inbox/ack-orphans${qs({ kind })}`);
+  return body.items;
+}
+
 /**
  * Download a ZIP of regenerated X12 837 files for a parsed batch.
  *
@@ -1064,5 +1236,10 @@ export const api = {
   listAcks,
   getAck,
   listTa1Acks,
+  listClaimAcks,
+  listAckClaims,
+  matchAckToClaim,
+  unmatchAck,
+  listAckOrphans,
   getDashboardKpis,
 };
diff --git a/src/types/index.ts b/src/types/index.ts
index 15b4e8c..7afc37a 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -537,6 +537,13 @@ export interface Ack {
    * round-trip to the detail endpoint.
    */
   patientControlNumber?: string | null;
+  /**
+   * SP28: distinct claim ids this 999 ack is linked to. Populated by
+   * the backend list endpoint so the Acks page can show a "Claims"
+   * badge column without a per-row detail round-trip. Empty array
+   * means no auto-link resolved (orphan).
+   */
+  linkedClaimIds?: string[];
 }
 
 // ---------------------------------------------------------------------------
@@ -569,6 +576,62 @@ export interface Ta1Ack {
   receiverId: string | null;
   sourceBatchId: string;
   parsedAt: string | null;
+  /**
+   * SP28: originating `Batch` ids this TA1 envelope is linked to
+   * (per D4, TA1 is envelope-level so it links to `Batch` rather
+   * than `Claim`). Empty array means no auto-link resolved.
+   */
+  linkedClaimIds?: string[];
+}
+
+// ---------------------------------------------------------------------------
+// SP28: claim↔ack link rows.
+// Mirrors the `claim_acks` table (cyclone.db.ClaimAck) and the wire shape
+// of `GET /api/claims/{id}/acks` + `GET /api/acks/{kind}/{id}/claims`.
+// Per-AK2 granularity (D1): a single 999 with two AK2 set-responses
+// produces two ClaimAck rows. TA1 batch-level rows have `claimId === null`
+// — the `ClaimDrawer` panel filters those out; the `AckDrawer` panel
+// renders them with the originating Batch instead of a claim.
+// ---------------------------------------------------------------------------
+
+/**
+ * Discriminator for the ack flavor that produced a `ClaimAck` row.
+ *
+ * - `"999"` — per-AK2 set-response (one row per AK2 in the inbound 999).
+ * - `"277ca"` — per-`ClaimStatus` (one row per `STC` in the inbound 277CA).
+ * - `"ta1"` — envelope-level (one row per TA1, no per-claim granularity).
+ */
+export type ClaimAckKind = "999" | "277ca" | "ta1";
+
+/**
+ * One persisted claim↔ack link row, camelCased for the UI. The
+ * `claimId` is `null` for TA1 batch-level rows (D4) — the
+ * `ClaimDrawer` panel filters those out so the operator only sees
+ * per-claim acks; the `AckDrawer` panel renders them with the
+ * originating Batch instead.
+ *
+ * `claimState` is a derived join (the 999/277CA row carries the
+ * current `Claim.state` so the drawer can render the
+ * `ClaimStateBadge` inline without a second round-trip). For
+ * TA1 batch-level rows with `claimId === null`, this is `"n/a"`.
+ *
+ * `ak2Index` is populated only for `"999"` rows — 277CA and TA1
+ * don't have AK2 segments. `setControlNumber` is populated for
+ * 999/277CA rows (the value the upstream ack actually carried,
+ * regardless of which join path resolved the link — spec D10).
+ */
+export interface ClaimAck {
+  id: number;
+  claimId: string | null;
+  batchId: string | null;
+  ackId: number;
+  ackKind: ClaimAckKind;
+  ak2Index: number | null;
+  setControlNumber: string | null;
+  setAcceptRejectCode: string | null;
+  linkedAt: string;
+  linkedBy: "auto" | "manual";
+  claimState?: string;
 }
 
 // ---------------------------------------------------------------------------
@@ -710,6 +773,15 @@ export interface ClaimDetail {
    * composite.
    */
   lineReconciliation?: ClaimDetailLineReconciliation[];
+  /**
+   * SP28: compact form of the claim's `claim_acks` rows. Each entry
+   * has `ack_id`, `ack_kind`, `set_accept_reject_code`, `parsed_at`
+   * (no `claim_state` join — the drawer can use this for the
+   * initial panel render and rely on the live-tail for the full
+   * per-row payload via `useClaimAcks`). Empty array when the claim
+   * has no acks.
+   */
+  ackLinks?: ClaimAck[];
 }
 
 // ---------------------------------------------------------------------------