Matrix: avoid stale verification SAS reuse

extensions/matrix/src/matrix/monitor/events.test.ts

@@ -28,6 +28,9 @@ function createHarness(params?: {
     otherUserId: string;
     updatedAt?: string;
     completed?: boolean;
+    pending?: boolean;
+    phase?: number;
+    phaseName?: string;
     sas?: {
       decimal?: [number, number, number];
       emoji?: Array<[string, string]>;
@@ -319,6 +322,117 @@ describe("registerMatrixMonitorEvents verification routing", () => {
     expect(sasBodies).toHaveLength(1);
   });
 
+  it("ignores cancelled verification flows when DM fallback resolves SAS notices", async () => {
+    const { sendMessage, roomEventListener } = createHarness({
+      joinedMembersByRoom: {
+        "!dm:example.org": ["@alice:example.org", "@bot:example.org"],
+      },
+      verifications: [
+        {
+          id: "verification-old-cancelled",
+          transactionId: "$old-flow",
+          otherUserId: "@alice:example.org",
+          updatedAt: new Date("2026-02-25T21:42:54.000Z").toISOString(),
+          phaseName: "cancelled",
+          phase: 4,
+          pending: false,
+          sas: {
+            decimal: [1111, 2222, 3333],
+            emoji: [
+              ["🚀", "Rocket"],
+              ["🦋", "Butterfly"],
+              ["📕", "Book"],
+            ],
+          },
+        },
+        {
+          id: "verification-new-active",
+          transactionId: "$different-flow-id",
+          otherUserId: "@alice:example.org",
+          updatedAt: new Date("2026-02-25T21:43:54.000Z").toISOString(),
+          phaseName: "started",
+          phase: 3,
+          pending: true,
+          sas: {
+            decimal: [6158, 1986, 3513],
+            emoji: [
+              ["🎁", "Gift"],
+              ["🌍", "Globe"],
+              ["🐴", "Horse"],
+            ],
+          },
+        },
+      ],
+    });
+
+    roomEventListener("!dm:example.org", {
+      event_id: "$start-active",
+      sender: "@alice:example.org",
+      type: "m.key.verification.start",
+      origin_server_ts: Date.now(),
+      content: {
+        "m.relates_to": { event_id: "$req-active" },
+      },
+    });
+
+    await vi.waitFor(() => {
+      const bodies = (sendMessage.mock.calls as unknown[][]).map((call) =>
+        String((call[1] as { body?: string } | undefined)?.body ?? ""),
+      );
+      expect(bodies.some((body) => body.includes("SAS decimal: 6158 1986 3513"))).toBe(true);
+    });
+    const bodies = (sendMessage.mock.calls as unknown[][]).map((call) =>
+      String((call[1] as { body?: string } | undefined)?.body ?? ""),
+    );
+    expect(bodies.some((body) => body.includes("SAS decimal: 1111 2222 3333"))).toBe(false);
+  });
+
+  it("does not emit SAS notices for cancelled verification events", async () => {
+    const { sendMessage, roomEventListener } = createHarness({
+      joinedMembersByRoom: {
+        "!dm:example.org": ["@alice:example.org", "@bot:example.org"],
+      },
+      verifications: [
+        {
+          id: "verification-cancelled",
+          transactionId: "$req-cancelled",
+          otherUserId: "@alice:example.org",
+          updatedAt: new Date("2026-02-25T21:42:54.000Z").toISOString(),
+          phaseName: "cancelled",
+          phase: 4,
+          pending: false,
+          sas: {
+            decimal: [1111, 2222, 3333],
+            emoji: [
+              ["🚀", "Rocket"],
+              ["🦋", "Butterfly"],
+              ["📕", "Book"],
+            ],
+          },
+        },
+      ],
+    });
+
+    roomEventListener("!dm:example.org", {
+      event_id: "$cancelled-1",
+      sender: "@alice:example.org",
+      type: "m.key.verification.cancel",
+      origin_server_ts: Date.now(),
+      content: {
+        code: "m.mismatched_sas",
+        reason: "The SAS did not match.",
+        "m.relates_to": { event_id: "$req-cancelled" },
+      },
+    });
+
+    await vi.waitFor(() => {
+      expect(sendMessage).toHaveBeenCalledTimes(1);
+    });
+    const body = getSentNoticeBody(sendMessage, 0);
+    expect(body).toContain("Matrix verification cancelled by @alice:example.org");
+    expect(body).not.toContain("SAS decimal:");
+  });
+
   it("warns once when encrypted events arrive without Matrix encryption enabled", () => {
     const { logger, roomEventListener } = createHarness({
       authEncryption: false,

extensions/matrix/src/matrix/monitor/verification-events.ts

@@ -18,6 +18,9 @@ type MatrixVerificationSummaryLike = {
   otherUserId: string;
   updatedAt?: string;
   completed?: boolean;
+  pending?: boolean;
+  phase?: number;
+  phaseName?: string;
   sas?: {
     decimal?: [number, number, number];
     emoji?: Array<[string, string]>;
@@ -162,6 +165,19 @@ function resolveSummaryRecency(summary: MatrixVerificationSummaryLike): number {
   return Number.isFinite(ts) ? ts : 0;
 }
 
+function isActiveVerificationSummary(summary: MatrixVerificationSummaryLike): boolean {
+  if (summary.completed === true) {
+    return false;
+  }
+  if (summary.phaseName === "cancelled" || summary.phaseName === "done") {
+    return false;
+  }
+  if (typeof summary.phase === "number" && summary.phase >= 4) {
+    return false;
+  }
+  return true;
+}
+
 async function resolveVerificationSummaryForSignal(
   client: MatrixClient,
   params: {
@@ -203,10 +219,10 @@ async function resolveVerificationSummaryForSignal(
   }
 
   // Fallback for DM flows where transaction IDs do not match room event IDs consistently.
-  const byUser = list
-    .filter((entry) => entry.otherUserId === params.senderId && entry.completed !== true)
-    .sort((a, b) => resolveSummaryRecency(b) - resolveSummaryRecency(a))[0];
-  return byUser ?? null;
+  const activeByUser = list
+    .filter((entry) => entry.otherUserId === params.senderId && isActiveVerificationSummary(entry))
+    .sort((a, b) => resolveSummaryRecency(b) - resolveSummaryRecency(a));
+  return activeByUser.length === 1 ? (activeByUser[0] ?? null) : null;
 }
 
 function trackBounded(set: Set<string>, value: string): boolean {
@@ -288,7 +304,10 @@ export function createMatrixVerificationEventRouter(params: {
         senderId,
         flowId,
       }).catch(() => null);
-      const sasNotice = summary ? formatVerificationSasNotice(summary) : null;
+      const sasNotice =
+        summary && isActiveVerificationSummary(summary)
+          ? formatVerificationSasNotice(summary)
+          : null;
 
       const notices: string[] = [];
       if (stageNotice) {