diff --git a/pkg/tools/shell.go b/pkg/tools/shell.go
index 713850f977..11a1d59da7 100644
--- a/pkg/tools/shell.go
+++ b/pkg/tools/shell.go
@@ -3,6 +3,7 @@ package tools
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -109,18 +110,43 @@ func (t *ExecTool) Execute(ctx context.Context, args map[string]interface{}) *To
 		cmd.Dir = cwd
 	}
 
+	prepareCommandForTermination(cmd)
+
 	var stdout, stderr bytes.Buffer
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr
 
-	err := cmd.Run()
+	if err := cmd.Start(); err != nil {
+		return ErrorResult(fmt.Sprintf("failed to start command: %v", err))
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- cmd.Wait()
+	}()
+
+	var err error
+	select {
+	case err = <-done:
+	case <-cmdCtx.Done():
+		_ = terminateProcessTree(cmd)
+		select {
+		case err = <-done:
+		case <-time.After(2 * time.Second):
+			if cmd.Process != nil {
+				_ = cmd.Process.Kill()
+			}
+			err = <-done
+		}
+	}
+
 	output := stdout.String()
 	if stderr.Len() > 0 {
 		output += "\nSTDERR:\n" + stderr.String()
 	}
 
 	if err != nil {
-		if cmdCtx.Err() == context.DeadlineExceeded {
+		if errors.Is(cmdCtx.Err(), context.DeadlineExceeded) {
 			msg := fmt.Sprintf("Command timed out after %v", t.timeout)
 			return &ToolResult{
 				ForLLM:  msg,
diff --git a/pkg/tools/shell_process_unix.go b/pkg/tools/shell_process_unix.go
new file mode 100644
index 0000000000..7b29a81bf7
--- /dev/null
+++ b/pkg/tools/shell_process_unix.go
@@ -0,0 +1,32 @@
+//go:build !windows
+
+package tools
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func prepareCommandForTermination(cmd *exec.Cmd) {
+	if cmd == nil {
+		return
+	}
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+}
+
+func terminateProcessTree(cmd *exec.Cmd) error {
+	if cmd == nil || cmd.Process == nil {
+		return nil
+	}
+
+	pid := cmd.Process.Pid
+	if pid <= 0 {
+		return nil
+	}
+
+	// Kill the entire process group spawned by the shell command.
+	_ = syscall.Kill(-pid, syscall.SIGKILL)
+	// Fallback kill on the shell process itself.
+	_ = cmd.Process.Kill()
+	return nil
+}
diff --git a/pkg/tools/shell_process_windows.go b/pkg/tools/shell_process_windows.go
new file mode 100644
index 0000000000..fe23b5c96f
--- /dev/null
+++ b/pkg/tools/shell_process_windows.go
@@ -0,0 +1,27 @@
+//go:build windows
+
+package tools
+
+import (
+	"os/exec"
+	"strconv"
+)
+
+func prepareCommandForTermination(cmd *exec.Cmd) {
+	// no-op on Windows
+}
+
+func terminateProcessTree(cmd *exec.Cmd) error {
+	if cmd == nil || cmd.Process == nil {
+		return nil
+	}
+
+	pid := cmd.Process.Pid
+	if pid <= 0 {
+		return nil
+	}
+
+	_ = exec.Command("taskkill", "/T", "/F", "/PID", strconv.Itoa(pid)).Run()
+	_ = cmd.Process.Kill()
+	return nil
+}
diff --git a/pkg/tools/shell_timeout_unix_test.go b/pkg/tools/shell_timeout_unix_test.go
new file mode 100644
index 0000000000..4c6388b9b0
--- /dev/null
+++ b/pkg/tools/shell_timeout_unix_test.go
@@ -0,0 +1,61 @@
+//go:build !windows
+
+package tools
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func processExists(pid int) bool {
+	if pid <= 0 {
+		return false
+	}
+	err := syscall.Kill(pid, 0)
+	return err == nil || err == syscall.EPERM
+}
+
+func TestShellTool_TimeoutKillsChildProcess(t *testing.T) {
+	tool := NewExecTool(t.TempDir(), false)
+	tool.SetTimeout(500 * time.Millisecond)
+
+	args := map[string]interface{}{
+		// Spawn a child process that would outlive the shell unless process-group kill is used.
+		"command": "sleep 60 & echo $! > child.pid; wait",
+	}
+
+	result := tool.Execute(context.Background(), args)
+	if !result.IsError {
+		t.Fatalf("expected timeout error, got success: %s", result.ForLLM)
+	}
+	if !strings.Contains(result.ForLLM, "timed out") {
+		t.Fatalf("expected timeout message, got: %s", result.ForLLM)
+	}
+
+	childPIDPath := filepath.Join(tool.workingDir, "child.pid")
+	data, err := os.ReadFile(childPIDPath)
+	if err != nil {
+		t.Fatalf("failed to read child pid file: %v", err)
+	}
+
+	childPID, err := strconv.Atoi(strings.TrimSpace(string(data)))
+	if err != nil {
+		t.Fatalf("failed to parse child pid: %v", err)
+	}
+
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if !processExists(childPID) {
+			return
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+
+	t.Fatalf("child process %d is still running after timeout", childPID)
+}