diff --git a/docs/react-hooks.md b/docs/react-hooks.md
index 2d67266..b83adf5 100644
--- a/docs/react-hooks.md
+++ b/docs/react-hooks.md
@@ -267,6 +267,63 @@ also exposes `refetch()` and `reset()`.
 
 ---
 
+## useStreamCountdown
+
+Live countdown to a cliff, cancellation, or completion deadline. The hook
+ticks once per second, so a vesting or payroll card can render the remaining
+time without wiring up its own timer.
+
+`targetTimestamp` and the optional `startTimestamp` are Unix timestamps in
+**seconds** (the same unit as `StreamInfo.startTime` / `StreamInfo.endTime`),
+not milliseconds.
+
+```tsx
+import { useStreamCountdown } from '@streamfi/react';
+
+function CliffCountdown({ stream }) {
+  const { days, hours, minutes, seconds, isPast, progressFraction } =
+    useStreamCountdown(stream.endTime, stream.startTime);
+
+  if (isPast) return <p>Stream complete — everything has unlocked.</p>;
+
+  return (
+    <div>
+      <p>
+        {days}d {hours}h {minutes}m {seconds}s remaining
+      </p>
+      {progressFraction !== null && (
+        <progress value={progressFraction} max={1} />
+      )}
+    </div>
+  );
+}
+```
+
+### Return Type
+
+```ts
+interface UseStreamCountdownResult {
+  days: number;
+  hours: number;
+  minutes: number;
+  seconds: number;
+  isPast: boolean;
+  progressFraction: number | null;
+}
+```
+
+### Parameters
+
+- `targetTimestamp`: The deadline to count down to, in Unix seconds. Pass
+  `null` or `undefined` to render a zeroed, not-yet-started state (handy
+  while a stream is still loading).
+- `startTimestamp` (optional): The start of the window, in Unix seconds.
+  Supplying it adds `progressFraction` — the elapsed share of the window,
+  clamped to `0`-`1`. Without it `progressFraction` is `null`, since a
+  deadline alone cannot define a range.
+
+---
+
 ## Error Handling
 
 Each hook exposes an `error` field that captures:
diff --git a/packages/react/src/__tests__/useStreamCountdown.test.tsx b/packages/react/src/__tests__/useStreamCountdown.test.tsx
new file mode 100644
index 0000000..3e45f15
--- /dev/null
+++ b/packages/react/src/__tests__/useStreamCountdown.test.tsx
@@ -0,0 +1,177 @@
+import { act, renderHook } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { useStreamCountdown } from '../hooks/useStreamCountdown.js';
+
+const BASE_MS = Date.UTC(2026, 0, 1, 0, 0, 0); // 2026-01-01T00:00:00Z
+const BASE_SEC = Math.floor(BASE_MS / 1000);
+
+describe('useStreamCountdown', () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date(BASE_MS));
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it('splits the remaining time into days, hours, minutes and seconds', () => {
+    const target = BASE_SEC + 86_400 + 2 * 3_600 + 3 * 60 + 4;
+
+    const { result } = renderHook(() => useStreamCountdown(target));
+
+    expect(result.current).toEqual({
+      days: 1,
+      hours: 2,
+      minutes: 3,
+      seconds: 4,
+      isPast: false,
+      progressFraction: null,
+    });
+  });
+
+  it('auto-ticks once per second', () => {
+    const target = BASE_SEC + 5;
+    const { result } = renderHook(() => useStreamCountdown(target));
+
+    expect(result.current.seconds).toBe(5);
+
+    act(() => {
+      vi.advanceTimersByTime(1_000);
+    });
+    expect(result.current.seconds).toBe(4);
+
+    act(() => {
+      vi.advanceTimersByTime(2_000);
+    });
+    expect(result.current.seconds).toBe(2);
+  });
+
+  it('reports isPast once the target is reached and clamps at zero', () => {
+    const target = BASE_SEC + 1;
+    const { result } = renderHook(() => useStreamCountdown(target));
+
+    expect(result.current.isPast).toBe(false);
+
+    act(() => {
+      vi.advanceTimersByTime(5_000);
+    });
+
+    expect(result.current.isPast).toBe(true);
+    expect(result.current).toMatchObject({ days: 0, hours: 0, minutes: 0, seconds: 0 });
+  });
+
+  it('derives progressFraction from the start/end window', () => {
+    const start = BASE_SEC;
+    const target = BASE_SEC + 100;
+    const { result } = renderHook(() => useStreamCountdown(target, start));
+
+    expect(result.current.progressFraction).toBe(0);
+
+    act(() => {
+      vi.advanceTimersByTime(50_000);
+    });
+    expect(result.current.progressFraction).toBe(0.5);
+
+    act(() => {
+      vi.advanceTimersByTime(50_000);
+    });
+    expect(result.current.progressFraction).toBe(1);
+  });
+
+  it('clamps progressFraction to 0 before the window starts', () => {
+    const { result } = renderHook(() =>
+      useStreamCountdown(BASE_SEC + 150, BASE_SEC + 50),
+    );
+
+    expect(result.current.progressFraction).toBe(0);
+    expect(result.current.isPast).toBe(false);
+  });
+
+  it('treats a zero-length window as complete only once past', () => {
+    const target = BASE_SEC + 10;
+    const { result } = renderHook(() => useStreamCountdown(target, target));
+
+    expect(result.current.progressFraction).toBe(0);
+    expect(result.current.isPast).toBe(false);
+
+    act(() => {
+      vi.advanceTimersByTime(10_000);
+    });
+
+    expect(result.current.progressFraction).toBe(1);
+    expect(result.current.isPast).toBe(true);
+  });
+
+  it('returns a zeroed, not-started result when the target is missing', () => {
+    const { result } = renderHook(() => useStreamCountdown(null, BASE_SEC));
+
+    expect(result.current).toEqual({
+      days: 0,
+      hours: 0,
+      minutes: 0,
+      seconds: 0,
+      isPast: false,
+      progressFraction: null,
+    });
+  });
+
+  it('treats non-finite targets as missing', () => {
+    const { result } = renderHook(() => useStreamCountdown(Number.NaN, BASE_SEC));
+
+    expect(result.current.isPast).toBe(false);
+    expect(result.current.progressFraction).toBeNull();
+  });
+
+  it('ignores a non-finite start timestamp for progressFraction', () => {
+    const { result } = renderHook(() =>
+      useStreamCountdown(BASE_SEC + 60, Number.POSITIVE_INFINITY),
+    );
+
+    expect(result.current.progressFraction).toBeNull();
+  });
+
+  it('re-syncs when the target changes', () => {
+    const { result, rerender } = renderHook(
+      ({ target }: { target: number }) => useStreamCountdown(target),
+      { initialProps: { target: BASE_SEC + 10 } },
+    );
+
+    expect(result.current.seconds).toBe(10);
+
+    rerender({ target: BASE_SEC + 3 });
+    expect(result.current.seconds).toBe(3);
+  });
+
+  it('clears its interval on unmount', () => {
+    const { unmount } = renderHook(() => useStreamCountdown(BASE_SEC + 60));
+    expect(vi.getTimerCount()).toBeGreaterThan(0);
+
+    unmount();
+    expect(vi.getTimerCount()).toBe(0);
+  });
+
+  it('decomposes long durations into whole units', () => {
+    const target = BASE_SEC + 2 * 86_400 + 5 * 3_600 + 59 * 60 + 59;
+    const { result } = renderHook(() => useStreamCountdown(target));
+
+    expect(result.current).toMatchObject({
+      days: 2,
+      hours: 5,
+      minutes: 59,
+      seconds: 59,
+    });
+  });
+
+  it('flags isPast exactly at the target', () => {
+    const target = BASE_SEC + 1;
+    const { result } = renderHook(() => useStreamCountdown(target));
+
+    act(() => {
+      vi.advanceTimersByTime(1_000);
+    });
+
+    expect(result.current.isPast).toBe(true);
+    expect(result.current.progressFraction).toBeNull();
+  });
+});
diff --git a/packages/react/src/hooks/useCircuitState.ts b/packages/react/src/hooks/useCircuitState.ts
index c98db3a..80fc24c 100644
--- a/packages/react/src/hooks/useCircuitState.ts
+++ b/packages/react/src/hooks/useCircuitState.ts
@@ -4,7 +4,7 @@ import {
   onCircuitChange,
   resetCircuit,
   type CircuitStatus,
-} from '../../src/rpc-circuit-state.js';
+} from '../../../../src/rpc-circuit-state.js';
 
 export interface UseCircuitStateResult {
   /** Current circuit status for the given scope. */
diff --git a/packages/react/src/hooks/useStreamCountdown.ts b/packages/react/src/hooks/useStreamCountdown.ts
new file mode 100644
index 0000000..d474640
--- /dev/null
+++ b/packages/react/src/hooks/useStreamCountdown.ts
@@ -0,0 +1,111 @@
+import { useEffect, useMemo, useState } from 'react';
+
+const SECONDS_PER_MINUTE = 60;
+const SECONDS_PER_HOUR = 3_600;
+const SECONDS_PER_DAY = 86_400;
+
+export interface UseStreamCountdownResult {
+  /** Whole days remaining (0 once the target has passed). */
+  days: number;
+  /** Whole hours remaining within the day, 0-23. */
+  hours: number;
+  /** Whole minutes remaining within the hour, 0-59. */
+  minutes: number;
+  /** Whole seconds remaining within the minute, 0-59. */
+  seconds: number;
+  /** True once the current time is at or past `targetTimestamp`. */
+  isPast: boolean;
+  /**
+   * Fraction (0-1) of the window between `startTimestamp` and
+   * `targetTimestamp` that has elapsed, clamped to [0, 1].
+   *
+   * `null` when no `startTimestamp` is supplied (or when either timestamp is
+   * not a finite number), since a fraction needs both ends of the window.
+   */
+  progressFraction: number | null;
+}
+
+function currentUnixSeconds(): number {
+  return Math.floor(Date.now() / 1000);
+}
+
+function isFiniteTimestamp(value: number | null | undefined): value is number {
+  return value != null && Number.isFinite(value);
+}
+
+/**
+ * Live countdown to a cliff or cancellation/completion deadline.
+ *
+ * `targetTimestamp` and the optional `startTimestamp` are Unix timestamps in
+ * **seconds** (the same unit as `StreamInfo.startTime`/`endTime`), not
+ * milliseconds. The hook re-renders every second so a vesting or payroll card
+ * can render `{days}d {hours}h {minutes}m {seconds}s` without wiring up its
+ * own timer.
+ *
+ * Pass `startTimestamp` as well to also get `progressFraction`, the share of
+ * the window that has already elapsed. Without it `progressFraction` is
+ * `null`; a countdown does not have enough information to derive a fraction
+ * from the deadline alone.
+ *
+ * @example
+ * ```tsx
+ * const { days, hours, minutes, seconds, isPast, progressFraction } =
+ *   useStreamCountdown(stream.endTime, stream.startTime);
+ * ```
+ */
+export function useStreamCountdown(
+  targetTimestamp: number | null | undefined,
+  startTimestamp?: number | null,
+): UseStreamCountdownResult {
+  const [now, setNow] = useState(currentUnixSeconds);
+
+  const hasTarget = isFiniteTimestamp(targetTimestamp);
+
+  // Re-sync on mount and whenever the target changes, then tick once per
+  // second. `targetTimestamp` is intentionally a dependency: a changed
+  // deadline must not keep counting down against the old value.
+  useEffect(() => {
+    if (!hasTarget) return;
+
+    setNow(currentUnixSeconds());
+    const interval = setInterval(() => {
+      setNow(currentUnixSeconds());
+    }, 1_000);
+
+    return () => clearInterval(interval);
+  }, [hasTarget, targetTimestamp]);
+
+  return useMemo(() => {
+    if (!hasTarget) {
+      return {
+        days: 0,
+        hours: 0,
+        minutes: 0,
+        seconds: 0,
+        isPast: false,
+        progressFraction: null,
+      };
+    }
+
+    const remaining = Math.max(0, targetTimestamp - now);
+    const isPast = now >= targetTimestamp;
+
+    const days = Math.floor(remaining / SECONDS_PER_DAY);
+    const hours = Math.floor((remaining % SECONDS_PER_DAY) / SECONDS_PER_HOUR);
+    const minutes = Math.floor((remaining % SECONDS_PER_HOUR) / SECONDS_PER_MINUTE);
+    const seconds = remaining % SECONDS_PER_MINUTE;
+
+    let progressFraction: number | null = null;
+    if (isFiniteTimestamp(startTimestamp)) {
+      const span = targetTimestamp - startTimestamp;
+      progressFraction =
+        span <= 0
+          ? isPast
+            ? 1
+            : 0
+          : Math.min(1, Math.max(0, (now - startTimestamp) / span));
+    }
+
+    return { days, hours, minutes, seconds, isPast, progressFraction };
+  }, [hasTarget, targetTimestamp, startTimestamp, now]);
+}
diff --git a/packages/react/src/hooks/useTransactionHistory.ts b/packages/react/src/hooks/useTransactionHistory.ts
index 90f5e9d..8a6a345 100644
--- a/packages/react/src/hooks/useTransactionHistory.ts
+++ b/packages/react/src/hooks/useTransactionHistory.ts
@@ -13,7 +13,7 @@ import {
   selectVisibleTransactions,
   selectTotalPages,
   selectViewStatus,
-} from '../../src/dashboard/transaction-history.js';
+} from '../../../../src/dashboard/transaction-history.js';
 
 export interface UseTransactionHistoryOptions {
   /** Wallet address used to derive transaction direction. */
diff --git a/packages/react/src/index.ts b/packages/react/src/index.ts
index c088551..09a76ca 100644
--- a/packages/react/src/index.ts
+++ b/packages/react/src/index.ts
@@ -66,6 +66,8 @@ export { useTransactionHistory } from './hooks/useTransactionHistory.js';
 export type { UseTransactionHistoryResult, UseTransactionHistoryOptions } from './hooks/useTransactionHistory.js';
 export { useCircuitState } from './hooks/useCircuitState.js';
 export type { UseCircuitStateResult } from './hooks/useCircuitState.js';
+export { useStreamCountdown } from './hooks/useStreamCountdown.js';
+export type { UseStreamCountdownResult } from './hooks/useStreamCountdown.js';
 export { useTokenAllowance } from './hooks/useTokenAllowance.js';
 export type {
   ApproveTokenAllowanceFn,