feat: hook config schema with user+project merge ordering

internal/config/config.go

@@ -10,6 +10,29 @@ type Config struct {
 	RateLimits RateLimitSection  `toml:"rate_limits"`
 	Security   SecuritySection   `toml:"security"`
 	Session    SessionSection    `toml:"session"`
+	Hooks      []HookConfig      `toml:"hooks"`
+}
+
+// HookConfig is a single hook entry from TOML config.
+//
+// Example:
+//
+//	[[hooks]]
+//	name = "block-dangerous-bash"
+//	event = "pre_tool_use"
+//	type = "command"
+//	exec = "bash-safety-check.sh"
+//	tool_pattern = "bash*"
+//	timeout = "10s"
+//	fail_open = false
+type HookConfig struct {
+	Name        string `toml:"name"`
+	Event       string `toml:"event"`
+	Type        string `toml:"type"`
+	Exec        string `toml:"exec"`
+	Timeout     string `toml:"timeout"`
+	FailOpen    bool   `toml:"fail_open"`
+	ToolPattern string `toml:"tool_pattern"`
 }
 
 type SessionSection struct {

internal/config/config_test.go

@@ -180,6 +180,151 @@ func TestProjectRoot_Fallback(t *testing.T) {
 	}
 }
 
+func TestHookConfig_TOML_RoundTrip(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "config.toml")
+	os.WriteFile(path, []byte(`
+[[hooks]]
+name = "log-tools"
+event = "post_tool_use"
+type = "command"
+exec = "tee -a /tmp/tools.log"
+timeout = "5s"
+fail_open = true
+tool_pattern = "bash*"
+`), 0o644)
+
+	cfg := Defaults()
+	if err := loadTOML(&cfg, path); err != nil {
+		t.Fatalf("loadTOML: %v", err)
+	}
+	if len(cfg.Hooks) != 1 {
+		t.Fatalf("len(Hooks) = %d, want 1", len(cfg.Hooks))
+	}
+	h := cfg.Hooks[0]
+	if h.Name != "log-tools" {
+		t.Errorf("Name = %q", h.Name)
+	}
+	if h.Event != "post_tool_use" {
+		t.Errorf("Event = %q", h.Event)
+	}
+	if h.Type != "command" {
+		t.Errorf("Type = %q", h.Type)
+	}
+	if h.Exec != "tee -a /tmp/tools.log" {
+		t.Errorf("Exec = %q", h.Exec)
+	}
+	if h.Timeout != "5s" {
+		t.Errorf("Timeout = %q", h.Timeout)
+	}
+	if !h.FailOpen {
+		t.Error("FailOpen should be true")
+	}
+	if h.ToolPattern != "bash*" {
+		t.Errorf("ToolPattern = %q", h.ToolPattern)
+	}
+}
+
+func TestHookConfig_MergeOrder(t *testing.T) {
+	globalDir := t.TempDir()
+	gnomaDir := filepath.Join(globalDir, "gnoma")
+	os.MkdirAll(gnomaDir, 0o755)
+	os.WriteFile(filepath.Join(gnomaDir, "config.toml"), []byte(`
+[[hooks]]
+name = "global-hook"
+event = "pre_tool_use"
+type = "command"
+exec = "echo global"
+`), 0o644)
+
+	projectDir := t.TempDir()
+	pGnomaDir := filepath.Join(projectDir, ".gnoma")
+	os.MkdirAll(pGnomaDir, 0o755)
+	os.WriteFile(filepath.Join(pGnomaDir, "config.toml"), []byte(`
+[[hooks]]
+name = "project-hook"
+event = "post_tool_use"
+type = "command"
+exec = "echo project"
+`), 0o644)
+
+	t.Setenv("XDG_CONFIG_HOME", globalDir)
+	origDir, _ := os.Getwd()
+	os.Chdir(projectDir)
+	defer os.Chdir(origDir)
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(cfg.Hooks) != 2 {
+		t.Fatalf("len(Hooks) = %d, want 2", len(cfg.Hooks))
+	}
+	// global hook first
+	if cfg.Hooks[0].Name != "global-hook" {
+		t.Errorf("Hooks[0].Name = %q, want global-hook", cfg.Hooks[0].Name)
+	}
+	if cfg.Hooks[1].Name != "project-hook" {
+		t.Errorf("Hooks[1].Name = %q, want project-hook", cfg.Hooks[1].Name)
+	}
+}
+
+func TestHookConfig_ProjectOnly(t *testing.T) {
+	// No global hooks, project defines one.
+	projectDir := t.TempDir()
+	pGnomaDir := filepath.Join(projectDir, ".gnoma")
+	os.MkdirAll(pGnomaDir, 0o755)
+	os.WriteFile(filepath.Join(pGnomaDir, "config.toml"), []byte(`
+[[hooks]]
+name = "project-only"
+event = "stop"
+type = "command"
+exec = "echo done"
+`), 0o644)
+
+	emptyGlobalDir := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", emptyGlobalDir)
+	origDir, _ := os.Getwd()
+	os.Chdir(projectDir)
+	defer os.Chdir(origDir)
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(cfg.Hooks) != 1 || cfg.Hooks[0].Name != "project-only" {
+		t.Errorf("Hooks = %v, want [project-only]", cfg.Hooks)
+	}
+}
+
+func TestHookConfig_GlobalOnly(t *testing.T) {
+	// Global defines a hook, no project config.
+	globalDir := t.TempDir()
+	gnomaDir := filepath.Join(globalDir, "gnoma")
+	os.MkdirAll(gnomaDir, 0o755)
+	os.WriteFile(filepath.Join(gnomaDir, "config.toml"), []byte(`
+[[hooks]]
+name = "global-only"
+event = "session_start"
+type = "command"
+exec = "echo start"
+`), 0o644)
+
+	projectDir := t.TempDir() // no .gnoma dir
+	t.Setenv("XDG_CONFIG_HOME", globalDir)
+	origDir, _ := os.Getwd()
+	os.Chdir(projectDir)
+	defer os.Chdir(origDir)
+
+	cfg, err := Load()
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(cfg.Hooks) != 1 || cfg.Hooks[0].Name != "global-only" {
+		t.Errorf("Hooks = %v, want [global-only]", cfg.Hooks)
+	}
+}
+
 func TestLayeredLoad(t *testing.T) {
 	// Set up global config
 	globalDir := t.TempDir()

internal/config/load.go

@@ -23,12 +23,22 @@ func Load() (*Config, error) {
 	if err := loadTOML(&cfg, globalPath); err != nil && !os.IsNotExist(err) {
 		return nil, fmt.Errorf("loading global config %s: %w", globalPath, err)
 	}
+	// Deep copy global hooks before the project layer.
+	// toml.Decode may reuse the backing array, so a plain slice-header copy
+	// would alias into whatever the project decode writes.
+	// Also reset cfg.Hooks to nil so the project layer starts clean —
+	// if the project config is absent, cfg.Hooks stays nil and the append
+	// below just returns the global hooks unchanged.
+	globalHooks := append([]HookConfig(nil), cfg.Hooks...)
+	cfg.Hooks = nil
 
 	// Layer 2: Project config
 	projectPath := projectConfigPath()
 	if err := loadTOML(&cfg, projectPath); err != nil && !os.IsNotExist(err) {
 		return nil, fmt.Errorf("loading project config %s: %w", projectPath, err)
 	}
+	// User hooks run first, project hooks after.
+	cfg.Hooks = append(globalHooks, cfg.Hooks...)
 
 	// Layer 3: Environment variables
 	applyEnv(&cfg)