diff --git a/internal/llm/claude_stream_driver.go b/internal/llm/claude_stream_driver.go
index 9817a09..220dde4 100644
--- a/internal/llm/claude_stream_driver.go
+++ b/internal/llm/claude_stream_driver.go
@@ -106,8 +106,7 @@ func (d *claudeStreamDriver) Close() error {
 			_ = stdin.Close()
 		}
 		if cmd != nil && cmd.Process != nil {
-			_ = cmd.Process.Kill()
-			err = cmd.Wait()
+			err = shared.WaitOrKill(cmd)
 		}
 		close(d.events)
 	})
@@ -159,8 +158,7 @@ func (d *claudeStreamDriver) ensureStarted(ctx context.Context, req RunRequest)
 	if d.closed {
 		d.mu.Unlock()
 		_ = stdin.Close()
-		_ = cmd.Process.Kill()
-		_ = cmd.Wait()
+		_ = shared.WaitOrKill(cmd)
 		return ErrInteractiveClosed
 	}
 	d.cmd = cmd
diff --git a/internal/llm/internal/shared/shared.go b/internal/llm/internal/shared/shared.go
index effc575..03efb78 100644
--- a/internal/llm/internal/shared/shared.go
+++ b/internal/llm/internal/shared/shared.go
@@ -1,7 +1,11 @@
-// Package shared provides scanner buffer constants used across LLM providers.
+// Package shared provides utilities and constants used across LLM providers.
 package shared
 
-import "time"
+import (
+	"os/exec"
+	"syscall"
+	"time"
+)
 
 // Default scanner buffer and token size constants used across providers.
 const (
@@ -12,3 +16,37 @@ const (
 
 // AuthCheckTimeout is the default timeout for CLI login/auth status checks.
 const AuthCheckTimeout = 15 * time.Second
+
+var (
+	// SubprocessGracePeriod is how long to wait for a subprocess to exit
+	// naturally after its stdin is closed before escalating to SIGTERM.
+	SubprocessGracePeriod = 10 * time.Second
+	// SubprocessTermGracePeriod is how long to wait after SIGTERM before
+	// escalating to SIGKILL.
+	SubprocessTermGracePeriod = 10 * time.Second
+)
+
+// WaitOrKill closes the subprocess gracefully: wait for natural exit after
+// stdin close, then SIGTERM, then SIGKILL as last resort.
+func WaitOrKill(cmd *exec.Cmd) error {
+	done := make(chan error, 1)
+	go func() {
+		done <- cmd.Wait()
+	}()
+	select {
+	case err := <-done:
+		return err
+	case <-time.After(SubprocessGracePeriod):
+	}
+	if err := cmd.Process.Signal(syscall.SIGTERM); err != nil {
+		_ = cmd.Process.Kill()
+		return <-done
+	}
+	select {
+	case err := <-done:
+		return err
+	case <-time.After(SubprocessTermGracePeriod):
+	}
+	_ = cmd.Process.Kill()
+	return <-done
+}
diff --git a/internal/llm/internal/shared/shared_test.go b/internal/llm/internal/shared/shared_test.go
new file mode 100644
index 0000000..e0059c4
--- /dev/null
+++ b/internal/llm/internal/shared/shared_test.go
@@ -0,0 +1,130 @@
+package shared
+
+import (
+	"os/exec"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestWaitOrKill_NormalExit(t *testing.T) {
+	cmd := exec.Command("true")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	if err := WaitOrKill(cmd); err != nil {
+		t.Fatalf("expected nil for exit 0, got %v", err)
+	}
+}
+
+func TestWaitOrKill_NonZeroExit(t *testing.T) {
+	cmd := exec.Command("sh", "-c", "exit 42")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+	err := WaitOrKill(cmd)
+	if err == nil {
+		t.Fatal("expected non-nil error for exit 42")
+	}
+	exitErr, ok := err.(*exec.ExitError)
+	if !ok {
+		t.Fatalf("expected *exec.ExitError, got %T: %v", err, err)
+	}
+	if status := exitErr.Sys().(syscall.WaitStatus); status.ExitStatus() != 42 {
+		t.Fatalf("expected exit code 42, got %d", status.ExitStatus())
+	}
+}
+
+func TestWaitOrKill_AlreadyExited(t *testing.T) {
+	cmd := exec.Command("true")
+	if err := cmd.Run(); err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	// WaitOrKill on already-waited process should return an error
+	// because cmd.Wait() can only be called once.
+	err := WaitOrKill(cmd)
+	if err == nil {
+		t.Fatal("expected error for already-waited process")
+	}
+}
+
+func TestWaitOrKill_SIGTERM_Escalation(t *testing.T) {
+	// Restore original durations after test.
+	oldGrace := SubprocessGracePeriod
+	oldTerm := SubprocessTermGracePeriod
+	SubprocessGracePeriod = 100 * time.Millisecond
+	SubprocessTermGracePeriod = 100 * time.Millisecond
+	defer func() {
+		SubprocessGracePeriod = oldGrace
+		SubprocessTermGracePeriod = oldTerm
+	}()
+
+	// Start a process that ignores SIGTERM.
+	// We use a shell script that traps SIGTERM and sleeps.
+	cmd := exec.Command("sh", "-c", "trap '' TERM; sleep 60")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+
+	start := time.Now()
+	err := WaitOrKill(cmd)
+	elapsed := time.Since(start)
+
+	if err == nil {
+		t.Fatal("expected non-nil error from killed process")
+	}
+
+	// Should have been killed after both grace periods expire
+	// (wait 100ms + SIGTERM 100ms ≈ 200ms, then SIGKILL).
+	// Allow some slack for scheduling.
+	if elapsed < 150*time.Millisecond {
+		t.Fatalf("expected at least ~200ms before kill, took %v", elapsed)
+	}
+	if elapsed > 2*time.Second {
+		t.Fatalf("kill took too long: %v", elapsed)
+	}
+
+	exitErr, ok := err.(*exec.ExitError)
+	if !ok {
+		t.Fatalf("expected *exec.ExitError, got %T: %v", err, err)
+	}
+	status := exitErr.Sys().(syscall.WaitStatus)
+	if !status.Signaled() {
+		t.Fatalf("expected process killed by signal, got status %v", status)
+	}
+}
+
+func TestWaitOrKill_SIGTERM_Accepted(t *testing.T) {
+	oldGrace := SubprocessGracePeriod
+	oldTerm := SubprocessTermGracePeriod
+	SubprocessGracePeriod = 100 * time.Millisecond
+	SubprocessTermGracePeriod = 100 * time.Millisecond
+	defer func() {
+		SubprocessGracePeriod = oldGrace
+		SubprocessTermGracePeriod = oldTerm
+	}()
+
+	// Start a process that accepts SIGTERM (the default).
+	cmd := exec.Command("sleep", "60")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start: %v", err)
+	}
+
+	err := WaitOrKill(cmd)
+	if err == nil {
+		t.Fatal("expected non-nil error from signaled process")
+	}
+
+	exitErr, ok := err.(*exec.ExitError)
+	if !ok {
+		t.Fatalf("expected *exec.ExitError, got %T: %v", err, err)
+	}
+	status := exitErr.Sys().(syscall.WaitStatus)
+	if !status.Signaled() {
+		t.Fatalf("expected process killed by signal, got status %v", status)
+	}
+	// SIGTERM (15) is the expected signal.
+	if status.Signal() != syscall.SIGTERM {
+		t.Fatalf("expected SIGTERM (15), got signal %d", status.Signal())
+	}
+}
diff --git a/internal/llm/jsonrpc_line_client.go b/internal/llm/jsonrpc_line_client.go
index c6a97aa..0749e4f 100644
--- a/internal/llm/jsonrpc_line_client.go
+++ b/internal/llm/jsonrpc_line_client.go
@@ -176,9 +176,9 @@ func (c *lineRPCClient) Close() error {
 	}
 	_ = c.stdin.Close()
 	if c.cmd.Process != nil {
-		_ = c.cmd.Process.Kill()
+		return shared.WaitOrKill(c.cmd)
 	}
-	return c.cmd.Wait()
+	return nil
 }
 
 func (c *lineRPCClient) write(payload any) error {
diff --git a/internal/llm/opencode_appserver_driver.go b/internal/llm/opencode_appserver_driver.go
index f03cf94..20113dd 100644
--- a/internal/llm/opencode_appserver_driver.go
+++ b/internal/llm/opencode_appserver_driver.go
@@ -117,8 +117,7 @@ func (d *openCodeAppServerDriver) Close() error {
 		d.eventCancel = nil
 		d.mu.Unlock()
 		if cmd != nil && cmd.Process != nil {
-			_ = cmd.Process.Kill()
-			err = cmd.Wait()
+			err = shared.WaitOrKill(cmd)
 		}
 		if cancelEvents != nil {
 			cancelEvents()
@@ -176,15 +175,13 @@ func (d *openCodeAppServerDriver) ensureServer(ctx context.Context, req RunReque
 	select {
 	case serverURL := <-urlCh:
 		if serverURL == "" {
-			_ = cmd.Process.Kill()
-			_ = cmd.Wait()
+			_ = shared.WaitOrKill(cmd)
 			return fmt.Errorf("opencode serve exited before reporting URL: %s", strings.TrimSpace(d.stderr.String()))
 		}
 		d.mu.Lock()
 		if d.closed {
 			d.mu.Unlock()
-			_ = cmd.Process.Kill()
-			_ = cmd.Wait()
+			_ = shared.WaitOrKill(cmd)
 			return ErrInteractiveClosed
 		}
 		d.cmd = cmd
@@ -193,8 +190,7 @@ func (d *openCodeAppServerDriver) ensureServer(ctx context.Context, req RunReque
 		d.ensureEventStream()
 		return nil
 	case <-ctx.Done():
-		_ = cmd.Process.Kill()
-		_ = cmd.Wait()
+		_ = shared.WaitOrKill(cmd)
 		return ctx.Err()
 	}
 }
@@ -698,7 +694,6 @@ func (d *openCodeAppServerDriver) hasOpenCodeAssistantText() bool {
 
 func (d *openCodeAppServerDriver) resetServerForNextRequest() {
 	d.mu.Lock()
-	defer d.mu.Unlock()
 	d.baseURL = ""
 	d.sessionID = ""
 	d.activeID = ""
@@ -709,11 +704,13 @@ func (d *openCodeAppServerDriver) resetServerForNextRequest() {
 		d.eventCancel()
 		d.eventCancel = nil
 	}
-	if d.cmd != nil && d.cmd.Process != nil {
-		_ = d.cmd.Process.Kill()
-		_ = d.cmd.Wait()
-	}
+	cmd := d.cmd
 	d.cmd = nil
+	d.mu.Unlock()
+
+	if cmd != nil && cmd.Process != nil {
+		_ = shared.WaitOrKill(cmd)
+	}
 }
 
 func (d *openCodeAppServerDriver) emit(event TurnEvent) {