diff --git a/pkg/tools/execute/execute_test.go b/pkg/tools/execute/execute_test.go
index f8d3d22..2b4a7a1 100644
--- a/pkg/tools/execute/execute_test.go
+++ b/pkg/tools/execute/execute_test.go
@@ -517,6 +517,25 @@ func TestRunReadBatch_WithLockDir(t *testing.T) {
 	}
 }
 
+func TestTimeoutZeroNoDeadline(t *testing.T) {
+	s := newServer(t)
+	ctx := context.Background()
+
+	// timeout=0 should not kill the process after 30s default.
+	// We verify by running a 2s sleep with timeout=0 and detaching it.
+	// If timeout were applied, it would use default 30s which is fine,
+	// but we confirm it doesn't fail with timeout=0.
+	done := make(chan string, 1)
+	go func() {
+		out, _ := s.Execute(ctx, "echo alive; sleep 1; echo done", "bash", 0, "default", true)
+		done <- out
+	}()
+	out := <-done
+	if !strings.Contains(out, "done") {
+		t.Errorf("expected 'done' in output, got: %q", out)
+	}
+}
+
 // ---- detach ----
 
 func TestDetach(t *testing.T) {
diff --git a/pkg/tools/execute/server.go b/pkg/tools/execute/server.go
index f4d2f79..5645197 100644
--- a/pkg/tools/execute/server.go
+++ b/pkg/tools/execute/server.go
@@ -191,7 +191,7 @@ Examples:
 							}
 						}
 					},
-					"timeout": {"type": "integer", "description": "Timeout in seconds per step (default: 30)."},
+					"timeout": {"type": "integer", "description": "Timeout in seconds per step (default: 30). Use 0 for no timeout."},
 					"sandbox": {"type": "string",  "description": "Sandbox name (default: default)."}
 				}
 			}`),
@@ -244,7 +244,7 @@ Examples:
 							}
 						}
 					},
-					"timeout": {"type": "integer", "description": "Timeout in seconds per call (default: 30)."},
+					"timeout": {"type": "integer", "description": "Timeout in seconds per call (default: 30). Use 0 for no timeout."},
 					"sandbox": {"type": "string",  "description": "Sandbox name (default: default)."}
 				}
 			}`),
@@ -301,7 +301,7 @@ Examples:
 							}
 						}
 					},
-					"timeout": {"type": "integer", "description": "Timeout in seconds per stage (default: 30)."},
+					"timeout": {"type": "integer", "description": "Timeout in seconds per stage (default: 30). Use 0 for no timeout."},
 					"sandbox": {"type": "string",  "description": "Sandbox name (default: default)."}
 				}
 			}`),
@@ -484,7 +484,7 @@ func (e *Server) Execute(ctx context.Context, code, language string, timeout int
 // executeWithStdin is like Execute but feeds stdinData to the command's stdin.
 // For languages where code is itself passed via stdin (ed, expect, bc), stdinData is ignored.
 func (e *Server) executeWithStdin(ctx context.Context, code, language string, timeout int, sandboxName string, trusted bool, stdinData string) (string, error) {
-	if timeout <= 0 {
+	if timeout < 0 {
 		timeout = 30
 	}
 
@@ -512,7 +512,13 @@ func (e *Server) executeWithStdin(ctx context.Context, code, language string, ti
 		workDir, _ = os.Getwd()
 	}
 
-	ctx, cancel := context.WithTimeout(ctx, time.Duration(timeout)*time.Second)
+	var cancel context.CancelFunc
+	if timeout > 0 {
+		ctx, cancel = context.WithTimeout(ctx, time.Duration(timeout)*time.Second)
+	} else {
+		// timeout=0 means no timeout (run indefinitely, e.g. for daemons)
+		ctx, cancel = context.WithCancel(ctx)
+	}
 	// NOTE: do NOT defer cancel() here — the detach path must avoid cancelling
 	// the context (which would kill the detached process via cmd.Cancel).
 	// Each exit path calls cancel() explicitly except detach.