fix(hooks): enter-plan stays silent when monocle engine is unreachable

Previously enter-plan always emitted a "Monocle is running for this
session..." PreToolUse context even when client.Connect failed,
which misled Claude in repos where the user never launched monocle.
It now exits 0 with no stdout when the engine is down, matching the
other three hooks (exit-plan, mark-activity, on-stop) and deferring
to Claude's native plan-mode flow.

Author: josephschmitt

cmd/monocle/hooks.go

@@ -263,23 +263,23 @@ func (cmd *EnterPlanHookCmd) runClaude(in hookInput) error {
 		return nil
 	}
 
-	// Start with the base context. If the engine is reachable, layer on any
-	// pending reviewer state. Timeout here is strict because the PreToolUse
-	// hook runs with a 5-second timeout.
-	context := "Monocle is running for this session. When you submit a plan via ExitPlanMode, it will be sent to a human reviewer who can approve or request changes — the approval flow is automatic, you do not need to run any review commands yourself."
-
+	// If the engine isn't reachable, stay out of Claude's way — the user
+	// isn't running monocle and doesn't want plan-mode injection.
 	c, err := client.Connect(socketPath)
-	if err == nil {
-		resp, err := c.Request(
-			&protocol.GetReviewStatusMsg{Type: protocol.TypeGetReviewStatus},
-			2*time.Second,
-		)
-		c.Close()
-		if err == nil {
-			if status, ok := resp.(*protocol.GetReviewStatusResponse); ok {
-				if status.Status == "pending" || status.CommentCount > 0 {
-					context += fmt.Sprintf(" There are %d unaddressed reviewer comment(s) — read them before finalizing the plan.", status.CommentCount)
-				}
+	if err != nil {
+		return nil
+	}
+	resp, reqErr := c.Request(
+		&protocol.GetReviewStatusMsg{Type: protocol.TypeGetReviewStatus},
+		2*time.Second,
+	)
+	c.Close()
+
+	context := "Monocle is running for this session. When you submit a plan via ExitPlanMode, it will be sent to a human reviewer who can approve or request changes — the approval flow is automatic, you do not need to run any review commands yourself."
+	if reqErr == nil {
+		if status, ok := resp.(*protocol.GetReviewStatusResponse); ok {
+			if status.Status == "pending" || status.CommentCount > 0 {
+				context += fmt.Sprintf(" There are %d unaddressed reviewer comment(s) — read them before finalizing the plan.", status.CommentCount)
 			}
 		}
 	}

cmd/monocle/hooks_test.go

@@ -3,6 +3,9 @@ package main
 import (
 	"bytes"
 	"encoding/json"
+	"io"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -152,6 +155,57 @@ func TestEmitClaudeStopBlock_FallbackReasonWhenEmpty(t *testing.T) {
 	}
 }
 
+// captureStdout runs fn with os.Stdout redirected to an in-memory buffer
+// and returns what fn wrote. Used to assert hooks stay silent when the
+// monocle engine isn't running.
+func captureStdout(t *testing.T, fn func()) string {
+	t.Helper()
+	orig := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	os.Stdout = w
+	done := make(chan []byte, 1)
+	go func() {
+		b, _ := io.ReadAll(r)
+		done <- b
+	}()
+	fn()
+	w.Close()
+	os.Stdout = orig
+	return string(<-done)
+}
+
+// TestEnterPlanHook_SilentWhenEngineDown verifies that the enter-plan hook
+// exits 0 with no stdout when monocle isn't running. Without the quiet
+// exit Claude would see "Monocle is running for this session..." even in
+// repos where the user never launched monocle.
+func TestEnterPlanHook_SilentWhenEngineDown(t *testing.T) {
+	// Use a workdir whose derived socket cannot exist.
+	tmp := t.TempDir()
+	cmd := &EnterPlanHookCmd{
+		WorkDirFlag: WorkDirFlag{WorkDir: tmp},
+		Agent:       "claude",
+		Socket:      filepath.Join(tmp, "definitely-not-running.sock"),
+	}
+
+	stdin := strings.NewReader(`{"session_id":"s","cwd":"` + tmp + `","tool_name":"ExitPlanMode","tool_input":{"plan":"# x"}}`)
+	in, err := decodeHookInput(stdin)
+	if err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+
+	out := captureStdout(t, func() {
+		if err := cmd.runClaude(in); err != nil {
+			t.Errorf("runClaude returned error (should degrade silently): %v", err)
+		}
+	})
+	if strings.TrimSpace(out) != "" {
+		t.Errorf("expected empty stdout when engine down, got: %q", out)
+	}
+}
+
 func TestFirstHeading(t *testing.T) {
 	cases := map[string]string{
 		"# Title\nbody":    "Title",