diff --git a/src/components/BatchDiffView.tsx b/src/components/BatchDiffView.tsx
index a7b3311..df0f3c6 100644
--- a/src/components/BatchDiffView.tsx
+++ b/src/components/BatchDiffView.tsx
@@ -5,6 +5,7 @@ import {
   Plus,
   type LucideIcon,
 } from "lucide-react";
+import { useNavigate } from "react-router-dom";
 import { Badge } from "@/components/ui/badge";
 import { Skeleton } from "@/components/ui/skeleton";
 import {
@@ -15,6 +16,7 @@ import {
   TableHeader,
   TableRow,
 } from "@/components/ui/table";
+import { DrillableCell } from "@/components/drill/DrillableCell";
 import { fmt } from "@/lib/format";
 import { cn } from "@/lib/utils";
 import type {
@@ -263,13 +265,28 @@ function RowIndicator({
 // ---------------------------------------------------------------------------
 
 function ClaimIdCell({ id }: { id: string }) {
+  // SP21 Phase 5 Task 5.6: each claim id is drillable to
+  // /claims?claim=ID so the operator can jump straight from a
+  // "Removed from A" or "Changed" row into the ClaimDrawer.
+  // DrillableCell handles e.stopPropagation internally — important
+  // if these rows ever get a row-level onClick. For removed claims
+  // that no longer exist in the DB, the ClaimDrawer's 404 state
+  // takes over (verified in Phase 2 testing).
+  const navigate = useNavigate();
   return (
-    <span
-      className="font-mono text-[12px] tracking-tight"
-      data-testid="diff-claim-id"
+    <DrillableCell
+      onClick={() =>
+        navigate(`/claims?claim=${encodeURIComponent(id)}`)
+      }
+      ariaLabel={`View claim ${id} in detail`}
     >
-      {id}
-    </span>
+      <span
+        className="font-mono text-[12px] tracking-tight"
+        data-testid="diff-claim-id"
+      >
+        {id}
+      </span>
+    </DrillableCell>
   );
 }
 
diff --git a/src/pages/BatchDiff.test.tsx b/src/pages/BatchDiff.test.tsx
index c58c612..8829605 100644
--- a/src/pages/BatchDiff.test.tsx
+++ b/src/pages/BatchDiff.test.tsx
@@ -481,8 +481,184 @@ describe("BatchDiff page", () => {
     ).toContain("pick a batch");
     unmount();
   });
+
+  it("SP21 Task 5.6: clicking an added-claim id navigates to /claims?claim=ID", async () => {
+    // Each ClaimIdCell wraps its id text with DrillableCell, whose
+    // onClick navigates to /claims?claim=ID. The MemoryRouter gives
+    // us a router context so the navigation completes; we observe
+    // it via the rendered pathname on a LocationTracker spy.
+    (api.listBatches as unknown as ReturnType<typeof vi.fn>).mockResolvedValue([
+      BATCH_A, BATCH_B,
+    ]);
+    (api.getBatchDiff as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      makeDiffPayload(),
+    );
+
+    const captured: { pathname: string; search: string } = {
+      pathname: "/batch-diff",
+      search: "",
+    };
+    const Tracker = () => {
+      const loc = useLocationSafe();
+      React.useEffect(() => {
+        captured.pathname = loc.pathname;
+        captured.search = loc.search;
+      }, [loc.pathname, loc.search]);
+      return null;
+    };
+
+    const { unmount } = renderIntoContainer(
+      <>
+        <Tracker />
+        <BatchDiff />
+      </>,
+      [`/batch-diff?a=${BATCH_A.id}&b=${BATCH_B.id}`],
+    );
+
+    await waitFor(
+      () => !!document.querySelector('[data-testid="diff-added-row-CLM-3"]'),
+      "added row rendered",
+    );
+
+    const cell = document.querySelector(
+      '[data-testid="diff-added-row-CLM-3"] [data-testid="diff-claim-id"]',
+    );
+    expect(cell).not.toBeNull();
+    // DrillableCell wraps the id text in its own <button>; click the
+    // nearest button ancestor so the drillable onClick fires.
+    const drillBtn =
+      (cell?.closest("button") as HTMLButtonElement | null) ?? null;
+    expect(drillBtn).not.toBeNull();
+    await act(async () => {
+      drillBtn!.click();
+      await Promise.resolve();
+    });
+
+    await waitFor(
+      () => captured.pathname === "/claims" && captured.search === "?claim=CLM-3",
+      "navigation to /claims?claim=CLM-3",
+    );
+    unmount();
+  });
+
+  it("SP21 Task 5.6: clicking a removed-claim id still navigates (ClaimDrawer handles 404)", async () => {
+    // The diff can list claim ids that no longer exist in the DB
+    // (Removed from A means "was in A, not in B" — the claim may
+    // still exist or may have been purged). Either way, clicking
+    // the id drills to /claims?claim=ID; the ClaimDrawer's 404
+    // state (Phase 2) handles the missing-claim case. This test
+    // only verifies the click path, not the drawer's 404 surface.
+    (api.listBatches as unknown as ReturnType<typeof vi.fn>).mockResolvedValue([
+      BATCH_A, BATCH_B,
+    ]);
+    (api.getBatchDiff as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      makeDiffPayload(),
+    );
+
+    const captured: { pathname: string; search: string } = {
+      pathname: "/batch-diff",
+      search: "",
+    };
+    const Tracker = () => {
+      const loc = useLocationSafe();
+      React.useEffect(() => {
+        captured.pathname = loc.pathname;
+        captured.search = loc.search;
+      }, [loc.pathname, loc.search]);
+      return null;
+    };
+
+    const { unmount } = renderIntoContainer(
+      <>
+        <Tracker />
+        <BatchDiff />
+      </>,
+      [`/batch-diff?a=${BATCH_A.id}&b=${BATCH_B.id}`],
+    );
+
+    await waitFor(
+      () => !!document.querySelector('[data-testid="diff-removed-row-CLM-2"]'),
+      "removed row rendered",
+    );
+
+    const cell = document.querySelector(
+      '[data-testid="diff-removed-row-CLM-2"] [data-testid="diff-claim-id"]',
+    );
+    const drillBtn =
+      (cell?.closest("button") as HTMLButtonElement | null) ?? null;
+    expect(drillBtn).not.toBeNull();
+    await act(async () => {
+      drillBtn!.click();
+      await Promise.resolve();
+    });
+
+    await waitFor(
+      () => captured.pathname === "/claims" && captured.search === "?claim=CLM-2",
+      "navigation to /claims?claim=CLM-2",
+    );
+    unmount();
+  });
+
+  it("SP21 Task 5.6: clicking a changed-claim id navigates to /claims?claim=ID", async () => {
+    // The Changed row uses the A-side id (per existing test
+    // assertions). Drill should fire on that id.
+    (api.listBatches as unknown as ReturnType<typeof vi.fn>).mockResolvedValue([
+      BATCH_A, BATCH_B,
+    ]);
+    (api.getBatchDiff as unknown as ReturnType<typeof vi.fn>).mockResolvedValue(
+      makeDiffPayload(),
+    );
+
+    const captured: { pathname: string; search: string } = {
+      pathname: "/batch-diff",
+      search: "",
+    };
+    const Tracker = () => {
+      const loc = useLocationSafe();
+      React.useEffect(() => {
+        captured.pathname = loc.pathname;
+        captured.search = loc.search;
+      }, [loc.pathname, loc.search]);
+      return null;
+    };
+
+    const { unmount } = renderIntoContainer(
+      <>
+        <Tracker />
+        <BatchDiff />
+      </>,
+      [`/batch-diff?a=${BATCH_A.id}&b=${BATCH_B.id}`],
+    );
+
+    await waitFor(
+      () => !!document.querySelector('[data-testid="diff-changed-row-CLM-1"]'),
+      "changed row rendered",
+    );
+
+    const cell = document.querySelector(
+      '[data-testid="diff-changed-row-CLM-1"] [data-testid="diff-claim-id"]',
+    );
+    const drillBtn =
+      (cell?.closest("button") as HTMLButtonElement | null) ?? null;
+    expect(drillBtn).not.toBeNull();
+    await act(async () => {
+      drillBtn!.click();
+      await Promise.resolve();
+    });
+
+    await waitFor(
+      () => captured.pathname === "/claims" && captured.search === "?claim=CLM-1",
+      "navigation to /claims?claim=CLM-1",
+    );
+    unmount();
+  });
 });
 
+// SP21 Phase 5 Task 5.6: react-router-dom's `useLocation` hook, used
+// by the LocationTracker test helper below. Aliased to keep the import
+// block tidy alongside React + the page import.
+import { useLocation as useLocationSafe } from "react-router-dom";
+
 // Keep `ApiError` referenced so the import isn't tree-shaken by
 // vitest's transformer when the mock factory above is hoisted.
 void ApiError;