diff --git a/src/pages/Reconciliation.test.tsx b/src/pages/Reconciliation.test.tsx
index 39b88e4..0c6e12a 100644
--- a/src/pages/Reconciliation.test.tsx
+++ b/src/pages/Reconciliation.test.tsx
@@ -19,6 +19,7 @@ vi.mock("@/lib/api", () => ({
     listUnmatched: vi.fn(),
     matchRemit: vi.fn(),
     unmatchClaim: vi.fn(),
+    getRemittance: vi.fn(),
   },
   ApiError: class ApiError extends Error {
     constructor(public status: number, message: string) {
@@ -86,6 +87,73 @@ async function waitForText(
 describe("ReconciliationPage", () => {
   beforeEach(() => {
     vi.clearAllMocks();
+    // Default for the per-remit detail fetch — the drawer fetches
+    // this whenever `?remit=` is in the URL. Return a never-resolving
+    // promise so the drawer stays in the loading state; the smoke
+    // test only asserts the drawer mounts.
+    (
+      api.getRemittance as unknown as ReturnType<typeof vi.fn>
+    ).mockReturnValue(new Promise(() => {}));
+  });
+
+  it("SP21 Task 4.6: deep-link ?remit=ID opens the RemitDrawer on mount", async () => {
+    // Non-empty unmatched payload so the page renders the two-column
+    // matching surface (the "Pair them." branch). The pre-existing
+    // empty-state branch has a flaky happy-dom/race that's unrelated
+    // to Phase 4 — using non-empty data sidesteps that bug and still
+    // proves the deep-link → drawer mount works. We pre-set
+    // `window.location` (which `useRemitDrawerUrlState` reads on
+    // mount) so `?remit=REM-7` resolves to a truthy `remitId`.
+    (
+      api.listUnmatched as unknown as ReturnType<typeof vi.fn>
+    ).mockResolvedValue({
+      claims: [
+        {
+          id: "CLM-1",
+          patientName: "Patient A",
+          billedAmount: 100,
+          providerNpi: "1234567890",
+          serviceDate: "2026-06-01",
+          payerId: "P1",
+          state: "submitted",
+        },
+      ],
+      remittances: [
+        {
+          id: "REM-7",
+          payerClaimControlNumber: "PCN-A",
+          status: "received",
+          paidAmount: 100,
+          adjustmentAmount: 0,
+          receivedDate: "2026-06-01",
+          isReversal: false,
+          totalCharge: 100,
+          serviceDate: "2026-06-01",
+          batchId: "b1",
+        },
+      ],
+    });
+    (window as unknown as { happyDOM: { setURL: (u: string) => void } })
+      .happyDOM.setURL("http://localhost/reconciliation?remit=REM-7");
+
+    const { unmount } = renderIntoContainer(
+      React.createElement(ReconciliationPage),
+    );
+
+    // Wait for the loaded two-column view (the "Pair them." headline
+    // is the clearest signal that listUnmatched has resolved and the
+    // page is past the loading + empty branches), then assert the
+    // drawer is mounted.
+    await waitForText("Pair them.");
+    expect(
+      document.body.querySelector('[data-testid="remit-drawer"]'),
+    ).not.toBeNull();
+
+    unmount();
+
+    // Reset URL so the next test sees a clean /reconciliation URL.
+    (window as unknown as { happyDOM: { setURL: (u: string) => void } })
+      .happyDOM.setURL("http://localhost/reconciliation");
   });
 
   it("renders both columns with unmatched rows when api returns data", async () => {
diff --git a/src/pages/Reconciliation.tsx b/src/pages/Reconciliation.tsx
index 6139d55..a47d062 100644
--- a/src/pages/Reconciliation.tsx
+++ b/src/pages/Reconciliation.tsx
@@ -11,6 +11,9 @@ import { ApiError } from "@/lib/api";
 import { Skeleton } from "@/components/ui/skeleton";
 import { ErrorState } from "@/components/ui/error-state";
 import { Button } from "@/components/ui/button";
+import { RemitDrawer } from "@/components/RemitDrawer";
+import { DrillableCell } from "@/components/drill/DrillableCell";
+import { useRemitDrawerUrlState } from "@/hooks/useRemitDrawerUrlState";
 import { cn } from "@/lib/utils";
 
 /**
@@ -26,6 +29,11 @@ import { cn } from "@/lib/utils";
  */
 export function ReconciliationPage() {
   const { unmatched, match } = useReconciliation();
+  // SP21 Phase 4 Task 4.6: drill into the RemitDrawer from the
+  // remits column. The hook reads `?remit=` from the URL so deep
+  // links land with the drawer open. Selection state stays local
+  // — the drill is a separate gesture from the match selection.
+  const { remitId, open, close } = useRemitDrawerUrlState();
   const [selectedClaim, setSelectedClaim] = useState<string | null>(null);
   const [selectedRemit, setSelectedRemit] = useState<string | null>(null);
 
@@ -735,11 +743,18 @@ export function ReconciliationPage() {
                 {remittances.map((r) => {
                   const active = selectedRemit === r.id;
                   return (
-                    <button
+                    <div
                       key={r.id}
-                      type="button"
-                      onClick={() => setSelectedRemit(r.id)}
+                      role="button"
+                      tabIndex={0}
                       aria-pressed={active}
+                      onClick={() => setSelectedRemit(r.id)}
+                      onKeyDown={(e) => {
+                        if (e.key === "Enter" || e.key === " ") {
+                          e.preventDefault();
+                          setSelectedRemit(r.id);
+                        }
+                      }}
                       className={cn(
                         "w-full text-left p-3.5 min-h-[44px] rounded-md border transition-colors",
                         active
@@ -751,7 +766,21 @@ export function ReconciliationPage() {
                         className="mono text-[13.5px] flex items-center gap-2"
                         style={{ color: "hsl(var(--surface-ink))" }}
                       >
-                        <span className="display">{r.payerClaimControlNumber}</span>
+                        {/* DrillableCell wraps the PCN text — clicking
+                            the text drills into the RemitDrawer; the
+                            surrounding div onClick (which selects the
+                            row for the match action) is suppressed
+                            because DrillableCell calls
+                            e.stopPropagation() in its onClick. The
+                            DrillableCell is its own <button>, so the
+                            outer row had to move off <button> to
+                            avoid invalid nested-button HTML. */}
+                        <DrillableCell
+                          onClick={() => open(r.id)}
+                          ariaLabel={`View remittance ${r.payerClaimControlNumber}`}
+                        >
+                          <span className="display">{r.payerClaimControlNumber}</span>
+                        </DrillableCell>
                         {r.isReversal ? (
                           <span
                             className="text-[10px] uppercase tracking-[0.18em] mono font-semibold"
@@ -768,7 +797,7 @@ export function ReconciliationPage() {
                         Status {r.status} · ${r.paidAmount.toFixed(2)} paid · $
                         {r.adjustmentAmount.toFixed(2)} adj
                       </div>
-                    </button>
+                    </div>
                   );
                 })}
               </PairColumn>
@@ -881,6 +910,22 @@ export function ReconciliationPage() {
           </span>
         </div>
       </div>
+
+      {/* SP21 Phase 4 Task 4.6: RemitDrawer mount. The remits column
+          drills into the parent remit via the PCN text (DrillableCell
+          + open). The drawer portals into document.body, so the
+          surrounding paper plane stays put while the drawer is open.
+          `remits` is empty (we don't keep a list of all remits on
+          this page), so j/k is a no-op while the drawer is open. */}
+      <RemitDrawer
+        remitId={remitId}
+        remits={[]}
+        onClose={close}
+        onNavigate={open}
+        onToggleHelp={() => {
+          // Reconciliation has no cheatsheet; `?` is a no-op here.
+        }}
+      />
     </div>
   );
 }