diff --git a/dotnet/src/Client.cs b/dotnet/src/Client.cs
index 74f1c66f..d29698dc 100644
--- a/dotnet/src/Client.cs
+++ b/dotnet/src/Client.cs
@@ -10,6 +10,7 @@
 using System.Data;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using System.Net.Sockets;
 using System.Text.Json;
 using System.Text.Json.Serialization;
@@ -210,21 +211,34 @@ async Task<Connection> StartCoreAsync(CancellationToken ct)
     /// </example>
     public async Task StopAsync()
     {
-        var errors = new List<Exception>();
+        var sessionsToDestroy = _sessions.Values.ToArray();
+        _sessions.Clear();
 
-        foreach (var session in _sessions.Values.ToArray())
+        var sessionTasks = sessionsToDestroy.Select(async session =>
         {
-            try
-            {
-                await session.DisposeAsync();
-            }
-            catch (Exception ex)
+            Exception? lastEx = null;
+            for (int attempt = 1; attempt <= 3; attempt++)
             {
-                errors.Add(new Exception($"Failed to destroy session {session.SessionId}: {ex.Message}", ex));
+                try
+                {
+                    await session.DisposeAsync();
+                    return null;
+                }
+                catch (Exception ex)
+                {
+                    lastEx = ex;
+                    if (attempt < 3)
+                    {
+                        // Exponential backoff: 100ms, 200ms
+                        await Task.Delay(100 * (1 << (attempt - 1)));
+                    }
+                }
             }
-        }
+            return new Exception($"Failed to destroy session {session.SessionId} after 3 attempts: {lastEx?.Message}", lastEx);
+        });
 
-        _sessions.Clear();
+        var results = await Task.WhenAll(sessionTasks);
+        var errors = results.Where(e => e != null).Cast<Exception>().ToList();
         await CleanupConnectionAsync(errors);
         _connectionTask = null;
 
diff --git a/go/client.go b/go/client.go
index 319c6588..7fcfe772 100644
--- a/go/client.go
+++ b/go/client.go
@@ -294,10 +294,34 @@ func (c *Client) Stop() error {
 	}
 	c.sessionsMux.Unlock()
 
+	var wg sync.WaitGroup
+	errChan := make(chan error, len(sessions))
+
 	for _, session := range sessions {
-		if err := session.Destroy(); err != nil {
-			errs = append(errs, fmt.Errorf("failed to destroy session %s: %w", session.SessionID, err))
-		}
+		wg.Add(1)
+		go func(s *Session) {
+			defer wg.Done()
+			var lastErr error
+			for attempt := 1; attempt <= 3; attempt++ {
+				if err := s.Destroy(); err != nil {
+					lastErr = err
+					if attempt < 3 {
+						// Exponential backoff: 100ms, 200ms
+						time.Sleep(time.Duration(100*(1<<(attempt-1))) * time.Millisecond)
+					}
+				} else {
+					return
+				}
+			}
+			errChan <- fmt.Errorf("failed to destroy session %s after 3 attempts: %w", s.SessionID, lastErr)
+		}(session)
+	}
+
+	wg.Wait()
+	close(errChan)
+
+	for err := range errChan {
+		errs = append(errs, err)
 	}
 
 	c.sessionsMux.Lock()
diff --git a/python/copilot/client.py b/python/copilot/client.py
index 85b72897..7e90e9fb 100644
--- a/python/copilot/client.py
+++ b/python/copilot/client.py
@@ -313,13 +313,30 @@ async def stop(self) -> list["StopError"]:
             sessions_to_destroy = list(self._sessions.values())
             self._sessions.clear()
 
-        for session in sessions_to_destroy:
-            try:
-                await session.destroy()
-            except Exception as e:
-                errors.append(
-                    StopError(message=f"Failed to destroy session {session.session_id}: {e}")
+        async def destroy_with_retry(session: CopilotSession) -> Optional[StopError]:
+            """Destroy a session with up to 3 attempts and exponential backoff."""
+            last_err: Optional[Exception] = None
+            for attempt in range(1, 4):
+                try:
+                    await session.destroy()
+                    return None
+                except Exception as e:
+                    last_err = e
+                    if attempt < 3:
+                        # Exponential backoff: 100ms, 200ms
+                        delay = 0.1 * (2 ** (attempt - 1))
+                        await asyncio.sleep(delay)
+
+            return StopError(
+                message=(
+                    f"Failed to destroy session {session.session_id} after 3 attempts: {last_err}"
                 )
+            )
+
+        # Destroy all active sessions in parallel with retry logic
+        if sessions_to_destroy:
+            results = await asyncio.gather(*(destroy_with_retry(s) for s in sessions_to_destroy))
+            errors.extend([r for r in results if r is not None])
 
         # Close client
         if self._client:
diff --git a/python/e2e/test_session.py b/python/e2e/test_session.py
index f2e545ed..96304739 100644
--- a/python/e2e/test_session.py
+++ b/python/e2e/test_session.py
@@ -198,7 +198,8 @@ async def test_should_list_sessions(self, ctx: E2ETestContext):
         await session2.send_and_wait({"prompt": "Say goodbye"})
 
         # Small delay to ensure session files are written to disk
-        await asyncio.sleep(0.2)
+        # Increased to 0.5s to avoid flakiness on slower environments (e.g. Windows CI)
+        await asyncio.sleep(0.5)
 
         # List sessions and verify they're included
         sessions = await ctx.client.list_sessions()
@@ -229,7 +230,8 @@ async def test_should_delete_session(self, ctx: E2ETestContext):
         session_id = session.session_id
 
         # Small delay to ensure session file is written to disk
-        await asyncio.sleep(0.2)
+        # Increased to 0.5s to avoid flakiness on slower environments (e.g. Windows CI)
+        await asyncio.sleep(0.5)
 
         # Verify session exists in the list
         sessions = await ctx.client.list_sessions()