Replace panic with graceful error returns in tmuxedit and mcp-server

Change initDebugLog() and defaultLogPath() to return errors instead of
panicking. Callers now handle errors gracefully with proper messages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

3 files changed, 24 insertions, 15 deletions

diff --git a/cmd/hexai-mcp-server/main.go b/cmd/hexai-mcp-server/main.go
index 1f52616..32817f3 100644
--- a/cmd/hexai-mcp-server/main.go
+++ b/cmd/hexai-mcp-server/main.go
@@ -56,7 +56,11 @@ type mcpOptions struct {
 func main() {
 	printDeprecationWarning()
 
-	defaultLog := defaultLogPath()
+	defaultLog, err := defaultLogPath()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
 	logPath := flag.String("log", defaultLog, "path to log file (optional)")
 	configPath := flag.String("config", "", "path to config file (optional)")
 	promptsDir := flag.String("prompts-dir", "", "path to prompts directory (optional)")
@@ -108,11 +112,11 @@ func run(opts mcpOptions, stdin io.Reader, stdout, stderr io.Writer) error {
 }
 
 // defaultLogPath returns the default MCP log file path in the state directory.
-// Panics if state directory cannot be created.
-func defaultLogPath() string {
+// Returns an error if the state directory cannot be created.
+func defaultLogPath() (string, error) {
 	stateDir, err := appconfig.StateDir()
 	if err != nil {
-		panic(fmt.Sprintf("cannot create state directory: %v", err))
+		return "", fmt.Errorf("cannot create state directory: %w", err)
 	}
-	return fmt.Sprintf("%s/hexai-mcp-server.log", stateDir)
+	return fmt.Sprintf("%s/hexai-mcp-server.log", stateDir), nil
 }
diff --git a/cmd/hexai-mcp-server/main_test.go b/cmd/hexai-mcp-server/main_test.go
index cf48954..76d0fca 100644
--- a/cmd/hexai-mcp-server/main_test.go
+++ b/cmd/hexai-mcp-server/main_test.go
@@ -41,7 +41,10 @@ func TestPrintDeprecationWarning(t *testing.T) {
 }
 
 func TestDefaultLogPath(t *testing.T) {
-	path := defaultLogPath()
+	path, err := defaultLogPath()
+	if err != nil {
+		t.Fatalf("defaultLogPath returned error: %v", err)
+	}
 	if path == "" {
 		t.Fatal("expected non-empty log path")
 	}
diff --git a/internal/tmuxedit/run.go b/internal/tmuxedit/run.go
index a156e5f..efa503b 100644
--- a/internal/tmuxedit/run.go
+++ b/internal/tmuxedit/run.go
@@ -111,23 +111,23 @@ func loadConfig(configPath string) appconfig.App {
 // debugLog is the debug logger. Set to a real logger via initDebugLog().
 var debugLog *log.Logger
 
-// initDebugLog creates a debug log file at /tmp/hexai-tmux-edit.log.
-// initDebugLog creates a debug log file in the state directory (~/.local/state/hexai/hexai-tmux-edit.log).
-// Falls back to /tmp if state directory cannot be created.
-// initDebugLog creates a debug log file in the state directory (~/.local/state/hexai/hexai-tmux-edit.log).
-// Panics if the state directory cannot be created.
-func initDebugLog() {
+// initDebugLog creates a debug log file in the state directory
+// (~/.local/state/hexai/hexai-tmux-edit.log). Returns an error if the
+// state directory cannot be resolved. Silently skips logging if the
+// log file itself cannot be opened.
+func initDebugLog() error {
 	stateDir, err := appconfig.StateDir()
 	if err != nil {
-		panic(fmt.Sprintf("cannot create state directory: %v", err))
+		return fmt.Errorf("cannot create state directory: %w", err)
 	}
 
 	logPath := filepath.Join(stateDir, "hexai-tmux-edit.log")
 	f, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o644)
 	if err != nil {
-		return
+		return nil
 	}
 	debugLog = log.New(f, "", log.LstdFlags|log.Lmicroseconds)
+	return nil
 }
 
 func dbg(format string, args ...any) {
@@ -140,7 +140,9 @@ func dbg(format string, args ...any) {
 // It resolves the agent (by name or auto-detect), extracts the current
 // prompt, opens the editor popup, then clears and sends the result.
 func runWithConfig(opts Options, cfg appconfig.App) error {
-	initDebugLog()
+	if err := initDebugLog(); err != nil {
+		return fmt.Errorf("init debug log: %w", err)
+	}
 	dbg("=== hexai-tmux-edit start ===")
 	dbg("opts: pane=%q agent=%q config=%q", opts.Pane, opts.Agent, opts.ConfigPath)