diff --git a/packages/claude-code-plugin/hooks/lib/hook_timer.py b/packages/claude-code-plugin/hooks/lib/hook_timer.py
new file mode 100644
index 00000000..0d28c0c9
--- /dev/null
+++ b/packages/claude-code-plugin/hooks/lib/hook_timer.py
@@ -0,0 +1,86 @@
+"""Adaptive hook timeout tracking (#945).
+
+Tracks hook execution time and provides statistics and warnings
+for hooks approaching their timeout threshold.
+"""
+import time
+from typing import Dict, List
+
+
+class HookTimer:
+    """Track hook execution times and provide performance statistics."""
+
+    def __init__(self) -> None:
+        self._active: Dict[str, float] = {}
+        self._timings: Dict[str, List[float]] = {}
+
+    def start(self, hook_name: str) -> None:
+        """Start timing a hook execution.
+
+        Args:
+            hook_name: Name of the hook being timed.
+        """
+        self._active[hook_name] = time.monotonic()
+
+    def stop(self, hook_name: str) -> float:
+        """Stop timing a hook and record the duration.
+
+        Args:
+            hook_name: Name of the hook to stop timing.
+
+        Returns:
+            Elapsed time in milliseconds.
+
+        Raises:
+            ValueError: If no active timer exists for the hook.
+        """
+        if hook_name not in self._active:
+            raise ValueError(f"No active timer for hook: {hook_name}")
+        elapsed_ms = (time.monotonic() - self._active.pop(hook_name)) * 1000
+        if hook_name not in self._timings:
+            self._timings[hook_name] = []
+        self._timings[hook_name].append(elapsed_ms)
+        return elapsed_ms
+
+    def get_stats(self) -> Dict[str, Dict[str, float]]:
+        """Compute statistics for all tracked hooks.
+
+        Returns:
+            Dict mapping hook_name to {count, avg_ms, p95_ms, max_ms}.
+        """
+        result: Dict[str, Dict[str, float]] = {}
+        for hook_name, timings in self._timings.items():
+            sorted_t = sorted(timings)
+            count = len(sorted_t)
+            avg_ms = sum(sorted_t) / count
+            p95_idx = int(count * 0.95)
+            if p95_idx >= count:
+                p95_idx = count - 1
+            result[hook_name] = {
+                "count": count,
+                "avg_ms": round(avg_ms, 2),
+                "p95_ms": round(sorted_t[p95_idx], 2),
+                "max_ms": round(sorted_t[-1], 2),
+            }
+        return result
+
+    def get_warnings(self, timeout_ms: int = 10000) -> List[str]:
+        """Return warnings for hooks using >=80% of their timeout.
+
+        Args:
+            timeout_ms: Hook timeout in milliseconds (default 10000).
+
+        Returns:
+            List of warning strings for slow hooks.
+        """
+        threshold = timeout_ms * 0.8
+        warnings: List[str] = []
+        for hook_name, timings in self._timings.items():
+            max_time = max(timings)
+            if max_time >= threshold:
+                pct = max_time / timeout_ms * 100
+                warnings.append(
+                    f"Hook '{hook_name}' used {max_time:.0f}ms "
+                    f"of {timeout_ms}ms timeout ({pct:.0f}%)"
+                )
+        return warnings
diff --git a/packages/claude-code-plugin/hooks/lib/stats.py b/packages/claude-code-plugin/hooks/lib/stats.py
index 199c96d3..30717dbe 100644
--- a/packages/claude-code-plugin/hooks/lib/stats.py
+++ b/packages/claude-code-plugin/hooks/lib/stats.py
@@ -6,7 +6,7 @@
 import json
 import os
 import time
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional
 
 try:
     import fcntl
@@ -52,12 +52,26 @@ def __init__(self, session_id: str, data_dir: Optional[str] = None, flush_interv
                 "tool_count": 0,
                 "error_count": 0,
                 "tool_names": {},
+                "hook_timings": {},
             })
 
         # In-memory accumulator — deltas since last flush
         self._mem_tool_count = 0
         self._mem_error_count = 0
         self._mem_tool_names: Dict[str, int] = {}
+        self._mem_hook_timings: Dict[str, List[float]] = {}
+
+    def record_hook_timing(self, hook_name: str, elapsed_ms: float) -> None:
+        """Record a hook execution timing in memory.
+
+        Args:
+            hook_name: Name of the hook (e.g. 'PreToolUse').
+            elapsed_ms: Elapsed time in milliseconds.
+        """
+        if hook_name not in self._mem_hook_timings:
+            self._mem_hook_timings[hook_name] = []
+        self._mem_hook_timings[hook_name].append(elapsed_ms)
+        self._pending_count += 1
 
     def record_tool_call(self, tool_name: str, success: bool = True) -> None:
         """Record a tool call in memory. Flushes to disk every flush_interval calls.
@@ -86,11 +100,19 @@ def flush(self) -> None:
         for name, count in self._mem_tool_names.items():
             tool_names[name] = tool_names.get(name, 0) + count
         data["tool_names"] = tool_names
+        # Merge hook timings
+        hook_timings = data.get("hook_timings", {})
+        for name, times in self._mem_hook_timings.items():
+            if name not in hook_timings:
+                hook_timings[name] = []
+            hook_timings[name].extend(times)
+        data["hook_timings"] = hook_timings
         self._locked_write(data)
         # Reset in-memory accumulators
         self._mem_tool_count = 0
         self._mem_error_count = 0
         self._mem_tool_names = {}
+        self._mem_hook_timings = {}
         self._pending_count = 0
 
     def _merged_data(self) -> Dict[str, Any]:
@@ -102,6 +124,13 @@ def _merged_data(self) -> Dict[str, Any]:
         for name, count in self._mem_tool_names.items():
             tool_names[name] = tool_names.get(name, 0) + count
         data["tool_names"] = tool_names
+        # Merge hook timings
+        hook_timings = dict(data.get("hook_timings", {}))
+        for name, times in self._mem_hook_timings.items():
+            if name not in hook_timings:
+                hook_timings[name] = []
+            hook_timings[name] = hook_timings[name] + times
+        data["hook_timings"] = hook_timings
         return data
 
     def format_summary(self) -> str:
@@ -123,7 +152,18 @@ def format_summary(self) -> str:
         sorted_tools = sorted(tool_names.items(), key=lambda x: x[1], reverse=True)
         tools_str = " ".join(f"{name}:{count}" for name, count in sorted_tools[:5])
 
-        return f"[CB] {minutes}m | {tool_count} tools | {error_count} {error_word} | {tools_str}"
+        summary = f"[CB] {minutes}m | {tool_count} tools | {error_count} {error_word} | {tools_str}"
+
+        # Append hook timing report if any timings exist
+        hook_timings = data.get("hook_timings", {})
+        if hook_timings:
+            timing_parts = []
+            for name, timings in sorted(hook_timings.items()):
+                avg = sum(timings) / len(timings)
+                timing_parts.append(f"{name}:{avg:.0f}ms")
+            summary += f" | \u23f1 {' '.join(timing_parts)}"
+
+        return summary
 
     def finalize(self) -> Dict[str, Any]:
         """Finalize session stats, return data, and cleanup file.
@@ -136,6 +176,23 @@ def finalize(self) -> Dict[str, Any]:
         duration = time.time() - data.get("started_at", time.time())
         data["duration_seconds"] = duration
 
+        # Compute hook timing statistics
+        hook_timings = data.get("hook_timings", {})
+        if hook_timings:
+            hook_timing_stats: Dict[str, Any] = {}
+            for name, timings in hook_timings.items():
+                sorted_t = sorted(timings)
+                count = len(sorted_t)
+                avg_ms = sum(sorted_t) / count
+                p95_idx = min(int(count * 0.95), count - 1)
+                hook_timing_stats[name] = {
+                    "count": count,
+                    "avg_ms": round(avg_ms, 2),
+                    "p95_ms": round(sorted_t[p95_idx], 2),
+                    "max_ms": round(sorted_t[-1], 2),
+                }
+            data["hook_timing_stats"] = hook_timing_stats
+
         # Cleanup stats file
         try:
             os.remove(self.stats_file)
@@ -190,6 +247,7 @@ def _locked_read(self) -> Dict[str, Any]:
                 "tool_count": 0,
                 "error_count": 0,
                 "tool_names": {},
+                "hook_timings": {},
             }
 
     def _locked_write(self, data: Dict[str, Any]) -> None:
diff --git a/packages/claude-code-plugin/tests/test_hook_timer.py b/packages/claude-code-plugin/tests/test_hook_timer.py
new file mode 100644
index 00000000..a0440889
--- /dev/null
+++ b/packages/claude-code-plugin/tests/test_hook_timer.py
@@ -0,0 +1,117 @@
+"""Tests for HookTimer — adaptive hook timeout tracking (#945)."""
+import os
+import sys
+import time
+
+import pytest
+
+# Ensure hooks/lib is on path
+_tests_dir = os.path.dirname(os.path.abspath(__file__))
+_lib_dir = os.path.join(os.path.dirname(_tests_dir), "hooks", "lib")
+if _lib_dir not in sys.path:
+    sys.path.insert(0, _lib_dir)
+
+from hook_timer import HookTimer
+
+
+@pytest.fixture
+def timer():
+    return HookTimer()
+
+
+class TestStartStop:
+    """Test basic start/stop timing functionality."""
+
+    def test_start_stop_returns_elapsed_ms(self, timer):
+        """stop() should return elapsed time in milliseconds."""
+        timer.start("my_hook")
+        time.sleep(0.05)
+        elapsed = timer.stop("my_hook")
+        assert elapsed >= 40  # at least ~40ms (sleep 50ms with tolerance)
+        assert elapsed < 200  # not unreasonably long
+
+    def test_stop_without_start_raises(self, timer):
+        """stop() without matching start() should raise ValueError."""
+        with pytest.raises(ValueError, match="No active timer"):
+            timer.stop("nonexistent_hook")
+
+    def test_multiple_hooks_tracked_independently(self, timer):
+        """Different hooks should track independently."""
+        timer.start("hook_a")
+        time.sleep(0.02)
+        timer.start("hook_b")
+        time.sleep(0.02)
+        elapsed_a = timer.stop("hook_a")
+        elapsed_b = timer.stop("hook_b")
+        # hook_a ran longer than hook_b
+        assert elapsed_a > elapsed_b
+
+    def test_same_hook_multiple_times(self, timer):
+        """Same hook can be started/stopped multiple times, recording each."""
+        timer.start("hook_a")
+        timer.stop("hook_a")
+        timer.start("hook_a")
+        timer.stop("hook_a")
+        stats = timer.get_stats()
+        assert stats["hook_a"]["count"] == 2
+
+
+class TestGetStats:
+    """Test statistics calculation."""
+
+    def test_empty_stats(self, timer):
+        """get_stats() on fresh timer returns empty dict."""
+        assert timer.get_stats() == {}
+
+    def test_stats_count_and_avg(self, timer):
+        """get_stats() should compute count and avg_ms correctly."""
+        # Inject known timings for deterministic tests
+        timer._timings["hook_a"] = [100.0, 200.0, 300.0]
+        stats = timer.get_stats()
+        assert stats["hook_a"]["count"] == 3
+        assert stats["hook_a"]["avg_ms"] == pytest.approx(200.0, abs=0.01)
+
+    def test_stats_p95(self, timer):
+        """get_stats() should compute p95_ms correctly."""
+        # 20 values: 10, 20, ..., 200
+        timer._timings["hook_a"] = [float(i * 10) for i in range(1, 21)]
+        stats = timer.get_stats()
+        # p95 of 20 items: index 19 (0.95*20=19) -> value 200
+        assert stats["hook_a"]["p95_ms"] == pytest.approx(200.0, abs=0.01)
+
+    def test_stats_max(self, timer):
+        """get_stats() should compute max_ms correctly."""
+        timer._timings["hook_a"] = [10.0, 50.0, 30.0, 999.0, 20.0]
+        stats = timer.get_stats()
+        assert stats["hook_a"]["max_ms"] == pytest.approx(999.0, abs=0.01)
+
+
+class TestGetWarnings:
+    """Test timeout warning detection."""
+
+    def test_no_warnings_when_fast(self, timer):
+        """Hooks well under timeout should produce no warnings."""
+        timer._timings["fast_hook"] = [100.0, 200.0, 300.0]
+        warnings = timer.get_warnings(timeout_ms=10000)
+        assert warnings == []
+
+    def test_warning_at_80_percent(self, timer):
+        """Hook using >=80% of timeout should produce a warning."""
+        # 80% of 10000 = 8000
+        timer._timings["slow_hook"] = [8000.0]
+        warnings = timer.get_warnings(timeout_ms=10000)
+        assert len(warnings) == 1
+        assert "slow_hook" in warnings[0]
+
+    def test_warning_with_custom_timeout(self, timer):
+        """get_warnings() should respect custom timeout_ms."""
+        timer._timings["hook_a"] = [500.0]
+        # 80% of 600 = 480, so 500 >= 480 -> warning
+        warnings = timer.get_warnings(timeout_ms=600)
+        assert len(warnings) == 1
+
+    def test_no_warning_just_below_threshold(self, timer):
+        """Hook just below 80% threshold should NOT warn."""
+        timer._timings["hook_a"] = [7999.0]
+        warnings = timer.get_warnings(timeout_ms=10000)
+        assert warnings == []
diff --git a/packages/claude-code-plugin/tests/test_stats.py b/packages/claude-code-plugin/tests/test_stats.py
index 925350af..40756240 100644
--- a/packages/claude-code-plugin/tests/test_stats.py
+++ b/packages/claude-code-plugin/tests/test_stats.py
@@ -195,6 +195,49 @@ def test_format_summary_uses_memory_data(self, data_dir):
         assert "Bash:2" in summary
 
 
+class TestHookTimingIntegration:
+    """Tests for hook timing integration in SessionStats (#945)."""
+
+    def test_hook_timings_field_initialized(self, stats):
+        """SessionStats should have hook_timings field in stored data."""
+        data = stats._locked_read()
+        assert "hook_timings" in data
+        assert data["hook_timings"] == {}
+
+    def test_record_hook_timing_stores_data(self, stats):
+        """record_hook_timing() should store timing in hook_timings."""
+        stats.record_hook_timing("PreToolUse", 150.0)
+        stats.record_hook_timing("PreToolUse", 200.0)
+        stats.record_hook_timing("PostToolUse", 50.0)
+        stats.flush()
+        data = stats._locked_read()
+        assert data["hook_timings"]["PreToolUse"] == [150.0, 200.0]
+        assert data["hook_timings"]["PostToolUse"] == [50.0]
+
+    def test_finalize_includes_hook_timing_stats(self, stats):
+        """finalize() should include computed hook timing statistics."""
+        stats.record_hook_timing("PreToolUse", 100.0)
+        stats.record_hook_timing("PreToolUse", 200.0)
+        stats.record_hook_timing("PreToolUse", 300.0)
+        result = stats.finalize()
+        assert "hook_timing_stats" in result
+        ht = result["hook_timing_stats"]["PreToolUse"]
+        assert ht["count"] == 3
+        assert ht["avg_ms"] == pytest.approx(200.0, abs=0.01)
+        assert ht["max_ms"] == pytest.approx(300.0, abs=0.01)
+
+    def test_format_summary_includes_timing_report(self, stats):
+        """format_summary() should include hook timing info when present."""
+        stats.record_hook_timing("PreToolUse", 8500.0)
+        summary = stats.format_summary()
+        assert "PreToolUse" in summary
+
+    def test_format_summary_no_timing_when_empty(self, stats):
+        """format_summary() should not include timing section when no timings."""
+        summary = stats.format_summary()
+        assert "⏱" not in summary
+
+
 class TestCleanup:
     def test_cleanup_stale_removes_old_files(self, data_dir):
         # Create a stale file