diff --git a/__tests__/signerStore.cancellation.test.ts b/__tests__/signerStore.cancellation.test.ts
new file mode 100644
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+++ b/__tests__/signerStore.cancellation.test.ts
@@ -0,0 +1,208 @@
+/**
+ * signerStore - payment cancellation vs. failure semantics (issue #250)
+ *
+ * Issue #250 ("Add mobile payment cancellation states") requires the signing
+ * flow to treat an intentional cancellation differently from a failure:
+ *   - cancellation is a distinct state, not an error;
+ *   - no error is surfaced for an intentional cancel;
+ *   - cancelled flows return safely and clear the pending transaction;
+ *   - a user-cancelled signer error stays distinguishable from a real failure.
+ *
+ * The existing suite (see __tests__/send.test.tsx) exercises the send-form and
+ * QR-scan cancel paths, but nothing asserts the signerStore state machine that
+ * backs the review -> handoff -> signing -> submitting flow. These tests cover
+ * that gap without changing any production behaviour.
+ */
+import { useSignerStore } from '../src/store/signerStore';
+import type {
+  SignerError,
+  SignerErrorType,
+  SigningResult,
+  TransactionReview,
+} from '../src/types/signer';
+
+const makeReview = (
+  overrides: Partial<TransactionReview> = {},
+): TransactionReview => ({
+  requestId: 'tx_test_0001',
+  sourcePublicKey: 'GSOURCE0000000000000000000000000000000000000000000000',
+  destinationPublicKey: 'GDEST00000000000000000000000000000000000000000000000',
+  destinationLabel: null,
+  amount: '12.5',
+  assetCode: 'XLM',
+  network: 'Testnet',
+  createdAt: '2026-01-01T00:00:00.000Z',
+  timeoutSeconds: 30,
+  ...overrides,
+});
+
+const makeResult = (
+  review: TransactionReview,
+  overrides: Partial<SigningResult> = {},
+): SigningResult => ({
+  hash: 'abcdef0123456789',
+  review,
+  signerType: 'local',
+  completedAt: '2026-01-01T00:00:05.000Z',
+  ...overrides,
+});
+
+const makeError = (
+  type: SignerErrorType,
+  message = 'something happened',
+): SignerError => ({ type, message });
+
+const store = () => useSignerStore.getState();
+
+beforeEach(() => {
+  store().reset();
+});
+
+describe('signerStore: cancellation is a distinct state from failure', () => {
+  it('cancelSigning moves to the "cancelled" phase, never "failed"', () => {
+    store().startReview(makeReview());
+    store().enterSigning();
+
+    store().cancelSigning();
+
+    expect(store().phase).toBe('cancelled');
+    expect(store().phase).not.toBe('failed');
+  });
+
+  it('failSigning moves to the "failed" phase, never "cancelled"', () => {
+    store().startReview(makeReview());
+    store().enterSigning();
+
+    store().failSigning(makeError('network_error'));
+
+    expect(store().phase).toBe('failed');
+    expect(store().phase).not.toBe('cancelled');
+  });
+});
+
+describe('signerStore: no error is surfaced for an intentional cancel', () => {
+  it('clears any prior error when cancelling', () => {
+    store().startReview(makeReview());
+    store().enterSigning();
+    store().failSigning(makeError('network_error'));
+    expect(store().error).not.toBeNull();
+
+    store().cancelSigning();
+
+    expect(store().phase).toBe('cancelled');
+    expect(store().error).toBeNull();
+  });
+
+  it('keeps the structured error when failing so the UI can show it', () => {
+    store().startReview(makeReview());
+    store().enterSigning();
+
+    const err = makeError('invalid_transaction', 'could not build transaction');
+    store().failSigning(err);
+
+    expect(store().error).toEqual(err);
+    expect(store().error?.message).toBe('could not build transaction');
+  });
+});
+
+describe('signerStore: cancelled flows return safely and clear state', () => {
+  it('clears the pending review and last result on cancel', () => {
+    const review = makeReview();
+    store().startReview(review);
+    store().enterSigning();
+    expect(store().currentReview).toEqual(review);
+
+    store().cancelSigning();
+
+    expect(store().currentReview).toBeNull();
+    expect(store().lastResult).toBeNull();
+  });
+
+  it('reset() returns from "cancelled" to a clean idle state', () => {
+    store().startReview(makeReview());
+    store().cancelSigning();
+    expect(store().phase).toBe('cancelled');
+
+    store().reset();
+
+    expect(store().phase).toBe('idle');
+    expect(store().currentReview).toBeNull();
+    expect(store().lastResult).toBeNull();
+    expect(store().error).toBeNull();
+  });
+});
+
+describe('signerStore: cancel is available at every pre-submission phase', () => {
+  const preSubmissionPhases: Array<[string, () => void]> = [
+    ['review', () => {}],
+    ['handoff', () => store().enterHandoff()],
+    ['signing', () => store().enterSigning()],
+  ];
+
+  it.each(preSubmissionPhases)(
+    'can cancel from the "%s" phase and land in "cancelled"',
+    (_label, advance) => {
+      store().startReview(makeReview());
+      advance();
+
+      store().cancelSigning();
+
+      expect(store().phase).toBe('cancelled');
+      expect(store().error).toBeNull();
+      expect(store().currentReview).toBeNull();
+    },
+  );
+});
+
+describe('signerStore: a user-cancelled signer error stays distinguishable from a real failure', () => {
+  it('both are "failed", but the error type separates a cancel from a network error', () => {
+    store().startReview(makeReview());
+    store().enterSigning();
+    store().failSigning(makeError('user_cancelled', 'User aborted signing'));
+    const cancelledLikeError = store().error;
+
+    store().reset();
+
+    store().startReview(makeReview());
+    store().enterSigning();
+    store().failSigning(makeError('network_error', 'Horizon submission failed'));
+    const realFailureError = store().error;
+
+    expect(cancelledLikeError?.type).toBe('user_cancelled');
+    expect(realFailureError?.type).toBe('network_error');
+    expect(cancelledLikeError?.type).not.toBe(realFailureError?.type);
+  });
+});
+
+describe('signerStore: re-entry after a cancellation starts fresh', () => {
+  it('startReview after cancel resets error/result and enters "review"', () => {
+    store().startReview(makeReview({ requestId: 'tx_first' }));
+    store().enterSigning();
+    store().cancelSigning();
+
+    const next = makeReview({ requestId: 'tx_second' });
+    store().startReview(next);
+
+    expect(store().phase).toBe('review');
+    expect(store().currentReview).toEqual(next);
+    expect(store().error).toBeNull();
+    expect(store().lastResult).toBeNull();
+  });
+
+  it('a successful sign after a prior cancel records the result cleanly', () => {
+    store().startReview(makeReview());
+    store().cancelSigning();
+
+    const review = makeReview({ requestId: 'tx_ok' });
+    store().startReview(review);
+    store().enterHandoff();
+    store().enterSigning();
+    store().enterSubmitting();
+    const result = makeResult(review);
+    store().completeSigning(result);
+
+    expect(store().phase).toBe('completed');
+    expect(store().lastResult).toEqual(result);
+    expect(store().error).toBeNull();
+  });
+});
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