8 files changed, 206 insertions, 48 deletions
diff --git a/internal/appconfig/app_feature_sections.go b/internal/appconfig/app_feature_sections.go
new file mode 100644
index 0000000..2513946
--- /dev/null
+++ b/internal/appconfig/app_feature_sections.go
@@ -0,0 +1,40 @@
+package appconfig
+
+import "slices"
+
+// This file provides fine-grained, read-only accessors for the individual
+// feature subsystems embedded in FeatureConfig. They let a consumer depend on
+// just the subsystem config it needs (e.g. the MCP server only needs MCPConfig)
+// instead of receiving the whole App God-struct. Each accessor returns a deep
+// copy so callers cannot mutate App's internal slices.
+
+// IgnoreSection returns a copy of the gitignore-aware filtering settings.
+func (a *App) IgnoreSection() IgnoreConfig {
+	c := a.IgnoreConfig
+	c.IgnoreExtraPatterns = slices.Clone(a.IgnoreExtraPatterns)
+	return c
+}
+
+// StatsSection returns the usage statistics settings.
+func (a *App) StatsSection() StatsConfig {
+	return a.StatsConfig
+}
+
+// TmuxEditSection returns a copy of the tmux popup editor settings.
+func (a *App) TmuxEditSection() TmuxEditConfig {
+	c := a.TmuxEditConfig
+	c.TmuxEditAgents = append([]TmuxEditAgentCfg{}, a.TmuxEditAgents...)
+	return c
+}
+
+// TmuxActionSection returns a copy of the tmux action menu settings.
+func (a *App) TmuxActionSection() TmuxActionConfig {
+	c := a.TmuxActionConfig
+	c.TmuxActionMenu = append([]TmuxActionMenuEntry{}, a.TmuxActionMenu...)
+	return c
+}
+
+// MCPSection returns the Model Context Protocol server settings.
+func (a *App) MCPSection() MCPConfig {
+	return a.MCPConfig
+}
diff --git a/internal/appconfig/app_feature_sections_test.go b/internal/appconfig/app_feature_sections_test.go
new file mode 100644
index 0000000..1f9ac2d
--- /dev/null
+++ b/internal/appconfig/app_feature_sections_test.go
@@ -0,0 +1,68 @@
+package appconfig
+
+import (
+	"reflect"
+	"testing"
+)
+
+// buildFeatureApp returns an App whose FeatureConfig subsystems are all
+// populated, used to verify the fine-grained section accessors.
+func buildFeatureApp() App {
+	cfg := App{}
+	cfg.ApplyFeatureSection(testFeatureConfig())
+	return cfg
+}
+
+func TestIgnoreSectionCopiesAndReads(t *testing.T) {
+	cfg := buildFeatureApp()
+	got := cfg.IgnoreSection()
+	if !reflect.DeepEqual(got.IgnoreExtraPatterns, []string{"vendor/**", "tmp/**"}) {
+		t.Fatalf("IgnoreExtraPatterns = %v", got.IgnoreExtraPatterns)
+	}
+	// Mutating the returned copy must not affect the source App.
+	got.IgnoreExtraPatterns[0] = "mutated"
+	if cfg.IgnoreExtraPatterns[0] == "mutated" {
+		t.Fatal("IgnoreSection did not return a defensive copy")
+	}
+}
+
+func TestStatsSectionReads(t *testing.T) {
+	cfg := buildFeatureApp()
+	if got := cfg.StatsSection(); got.StatsWindowMinutes != 15 {
+		t.Fatalf("StatsWindowMinutes = %d, want 15", got.StatsWindowMinutes)
+	}
+}
+
+func TestTmuxEditSectionCopies(t *testing.T) {
+	cfg := buildFeatureApp()
+	got := cfg.TmuxEditSection()
+	if got.TmuxEditDefaultAgent != "codex" || len(got.TmuxEditAgents) != 1 {
+		t.Fatalf("unexpected tmux edit section: %+v", got)
+	}
+	got.TmuxEditAgents[0].Name = "mutated"
+	if cfg.TmuxEditAgents[0].Name == "mutated" {
+		t.Fatal("TmuxEditSection did not return a defensive copy")
+	}
+}
+
+func TestTmuxActionSectionCopies(t *testing.T) {
+	cfg := App{}
+	cfg.TmuxActionMenu = []TmuxActionMenuEntry{{Kind: "rewrite"}}
+	got := cfg.TmuxActionSection()
+	if len(got.TmuxActionMenu) != 1 || got.TmuxActionMenu[0].Kind != "rewrite" {
+		t.Fatalf("unexpected tmux action section: %+v", got)
+	}
+	got.TmuxActionMenu[0].Kind = "mutated"
+	if cfg.TmuxActionMenu[0].Kind == "mutated" {
+		t.Fatal("TmuxActionSection did not return a defensive copy")
+	}
+}
+
+func TestMCPSectionReads(t *testing.T) {
+	cfg := buildFeatureApp()
+	got := cfg.MCPSection()
+	if got.MCPPromptsDir != ".hexai/prompts" || !got.MCPSlashCommandSync ||
+		got.MCPSlashCommandDir != ".hexai/slash" {
+		t.Fatalf("unexpected MCP section: %+v", got)
+	}
+}
diff --git a/internal/appconfig/app_sections.go b/internal/appconfig/app_sections.go
index 05b3171..5919db1 100644
--- a/internal/appconfig/app_sections.go
+++ b/internal/appconfig/app_sections.go
@@ -102,26 +102,18 @@ type PromptConfig struct {
 	TmuxCustomMenuHotkey string         `json:"-"`
 }
 
-// FeatureConfig contains non-LLM feature toggles/integration settings.
-// It is embedded in App; fields use json:"-" since features are not exposed via JSON.
+// FeatureConfig groups the non-LLM feature subsystems. Rather than a flat
+// grab-bag, it now embeds one cohesive struct per subsystem (see
+// feature_sections.go). Embedding keeps field promotion intact so existing flat
+// access (e.g. cfg.MCPPromptsDir) and the JSON shape are unchanged; the split
+// just makes the subsystem boundaries explicit and lets callers depend on a
+// single subsystem via the App.*Section accessors.
 type FeatureConfig struct {
-	// Stats
-	StatsWindowMinutes int `json:"-"`
-	// Ignore: gitignore-aware file filtering for LSP
-	IgnoreGitignore     *bool    `json:"-"`
-	IgnoreExtraPatterns []string `json:"-"`
-	IgnoreLSPNotify     *bool    `json:"-"`
-	// TmuxEdit: popup editor settings for hexai-tmux-edit
-	TmuxEditPopupWidth   string             `json:"-"`
-	TmuxEditPopupHeight  string             `json:"-"`
-	TmuxEditDefaultAgent string             `json:"-"`
-	TmuxEditAgents       []TmuxEditAgentCfg `json:"-"`
-	// TmuxAction: configurable main menu for hexai-tmux-action
-	TmuxActionMenu []TmuxActionMenuEntry `json:"-"`
-	// MCP: Model Context Protocol server settings
-	MCPPromptsDir       string `json:"-"` // Directory for prompt storage
-	MCPSlashCommandSync bool   `json:"-"` // Enable slash command sync
-	MCPSlashCommandDir  string `json:"-"` // Directory for slash command files
+	StatsConfig      // usage statistics window
+	IgnoreConfig     // gitignore-aware file filtering for LSP
+	TmuxEditConfig   // popup editor settings for hexai-tmux-edit
+	TmuxActionConfig // configurable main menu for hexai-tmux-action
+	MCPConfig        // Model Context Protocol server settings
 }
 
 // AppSections is the focused split of App into subsystem-specific config groups.
diff --git a/internal/appconfig/app_sections_test.go b/internal/appconfig/app_sections_test.go
index e26d3f3..bcd1cbe 100644
--- a/internal/appconfig/app_sections_test.go
+++ b/internal/appconfig/app_sections_test.go
@@ -169,28 +169,34 @@ func testPromptConfig() PromptConfig {
 
 func testFeatureConfig() FeatureConfig {
 	return FeatureConfig{
-		StatsWindowMinutes:   15,
-		IgnoreGitignore:      sectionBoolPtr(true),
-		IgnoreExtraPatterns:  []string{"vendor/**", "tmp/**"},
-		IgnoreLSPNotify:      sectionBoolPtr(false),
-		TmuxEditPopupWidth:   "80%",
-		TmuxEditPopupHeight:  "75%",
-		TmuxEditDefaultAgent: "codex",
-		TmuxEditAgents: []TmuxEditAgentCfg{{
-			Name:           "codex",
-			DisplayName:    "Codex",
-			DetectPattern:  "(?i)codex",
-			SectionPattern: "section",
-			PromptPattern:  "prompt",
-			StripPatterns:  []string{"x", "y"},
-			ClearFirst:     sectionBoolPtr(true),
-			ClearKeys:      "C-u",
-			NewlineKeys:    "S-Enter",
-			SubmitKeys:     "Enter",
-		}},
-		MCPPromptsDir:       ".hexai/prompts",
-		MCPSlashCommandSync: true,
-		MCPSlashCommandDir:  ".hexai/slash",
+		StatsConfig: StatsConfig{StatsWindowMinutes: 15},
+		IgnoreConfig: IgnoreConfig{
+			IgnoreGitignore:     sectionBoolPtr(true),
+			IgnoreExtraPatterns: []string{"vendor/**", "tmp/**"},
+			IgnoreLSPNotify:     sectionBoolPtr(false),
+		},
+		TmuxEditConfig: TmuxEditConfig{
+			TmuxEditPopupWidth:   "80%",
+			TmuxEditPopupHeight:  "75%",
+			TmuxEditDefaultAgent: "codex",
+			TmuxEditAgents: []TmuxEditAgentCfg{{
+				Name:           "codex",
+				DisplayName:    "Codex",
+				DetectPattern:  "(?i)codex",
+				SectionPattern: "section",
+				PromptPattern:  "prompt",
+				StripPatterns:  []string{"x", "y"},
+				ClearFirst:     sectionBoolPtr(true),
+				ClearKeys:      "C-u",
+				NewlineKeys:    "S-Enter",
+				SubmitKeys:     "Enter",
+			}},
+		},
+		MCPConfig: MCPConfig{
+			MCPPromptsDir:       ".hexai/prompts",
+			MCPSlashCommandSync: true,
+			MCPSlashCommandDir:  ".hexai/slash",
+		},
 	}
 }
 
diff --git a/internal/appconfig/config_features_test.go b/internal/appconfig/config_features_test.go
index 77beb07..2b8c769 100644
--- a/internal/appconfig/config_features_test.go
+++ b/internal/appconfig/config_features_test.go
@@ -183,13 +183,13 @@ func TestTmuxEditConfig_Merge(t *testing.T) {
 	clearHexaiEnv(t)
 	a := newDefaultConfig()
 	b := App{
-		FeatureConfig: FeatureConfig{
+		FeatureConfig: FeatureConfig{TmuxEditConfig: TmuxEditConfig{
 			TmuxEditPopupWidth:   "70%",
 			TmuxEditDefaultAgent: "amp",
 			TmuxEditAgents: []TmuxEditAgentCfg{
 				{Name: "amp", DisplayName: "Amp"},
 			},
-		},
+		}},
 	}
 	a.mergeWith(&b)
 	if a.TmuxEditPopupWidth != "70%" {
diff --git a/internal/appconfig/config_load.go b/internal/appconfig/config_load.go
index 1e4c6b7..ccbf49f 100644
--- a/internal/appconfig/config_load.go
+++ b/internal/appconfig/config_load.go
@@ -388,11 +388,11 @@ func applyIgnoreSection(fc *fileConfig, out *App) {
 	if fc.Ignore.Gitignore == nil && len(fc.Ignore.ExtraPatterns) == 0 && fc.Ignore.LSPNotifyIgnored == nil {
 		return
 	}
-	tmp := App{FeatureConfig: FeatureConfig{
+	tmp := App{FeatureConfig: FeatureConfig{IgnoreConfig: IgnoreConfig{
 		IgnoreGitignore:     fc.Ignore.Gitignore,
 		IgnoreExtraPatterns: fc.Ignore.ExtraPatterns,
 		IgnoreLSPNotify:     fc.Ignore.LSPNotifyIgnored,
-	}}
+	}}}
 	out.mergeBasics(&tmp)
 }
 
diff --git a/internal/appconfig/config_types.go b/internal/appconfig/config_types.go
index 8d50f35..7069b21 100644
--- a/internal/appconfig/config_types.go
+++ b/internal/appconfig/config_types.go
@@ -106,10 +106,12 @@ func newDefaultConfig() App {
 		},
 		PromptConfig: defaultPromptConfig(),
 		FeatureConfig: FeatureConfig{
-			StatsWindowMinutes: 60,
+			StatsConfig: StatsConfig{StatsWindowMinutes: 60},
 			// Ignore: respect .gitignore by default, notify in LSP by default
-			IgnoreGitignore: boolPtr(true),
-			IgnoreLSPNotify: boolPtr(true),
+			IgnoreConfig: IgnoreConfig{
+				IgnoreGitignore: boolPtr(true),
+				IgnoreLSPNotify: boolPtr(true),
+			},
 		},
 	}
 }
diff --git a/internal/appconfig/feature_sections.go b/internal/appconfig/feature_sections.go
new file mode 100644
index 0000000..9216400
--- /dev/null
+++ b/internal/appconfig/feature_sections.go
@@ -0,0 +1,50 @@
+package appconfig
+
+// This file defines the cohesive per-subsystem config structs that make up
+// FeatureConfig. The old FeatureConfig was a grab-bag that mixed five unrelated
+// non-LLM subsystems (ignore filtering, stats, tmux popup editor, tmux action
+// menu, MCP server). Splitting them into named structs documents the seams
+// between subsystems and lets consumers depend on a single subsystem's config
+// (via the *Section accessors on App) instead of the whole App God-struct.
+//
+// Each struct is embedded into FeatureConfig, so Go field promotion keeps the
+// historical flat access (e.g. cfg.MCPPromptsDir) working for read sites across
+// the codebase. Only composite literals that set these leaf fields directly on
+// FeatureConfig had to move to the nested form.
+
+// IgnoreConfig controls gitignore-aware file filtering for the LSP server.
+// Files matching these patterns are skipped for completions and code actions.
+type IgnoreConfig struct {
+	// IgnoreGitignore enables respecting .gitignore entries (default true).
+	IgnoreGitignore *bool `json:"-"`
+	// IgnoreExtraPatterns are additional glob patterns to always ignore.
+	IgnoreExtraPatterns []string `json:"-"`
+	// IgnoreLSPNotify controls whether the LSP notifies when ignoring a file.
+	IgnoreLSPNotify *bool `json:"-"`
+}
+
+// StatsConfig holds settings for the usage statistics subsystem.
+type StatsConfig struct {
+	// StatsWindowMinutes is the rolling window (in minutes) used for stats.
+	StatsWindowMinutes int `json:"-"`
+}
+
+// TmuxEditConfig configures the tmux popup editor feature (hexai-tmux-edit).
+type TmuxEditConfig struct {
+	TmuxEditPopupWidth   string             `json:"-"`
+	TmuxEditPopupHeight  string             `json:"-"`
+	TmuxEditDefaultAgent string             `json:"-"`
+	TmuxEditAgents       []TmuxEditAgentCfg `json:"-"`
+}
+
+// TmuxActionConfig configures the main menu for hexai-tmux-action.
+type TmuxActionConfig struct {
+	TmuxActionMenu []TmuxActionMenuEntry `json:"-"`
+}
+
+// MCPConfig holds Model Context Protocol server settings.
+type MCPConfig struct {
+	MCPPromptsDir       string `json:"-"` // Directory for prompt storage
+	MCPSlashCommandSync bool   `json:"-"` // Enable slash command sync
+	MCPSlashCommandDir  string `json:"-"` // Directory for slash command files
+}