diff --git a/TODO.md b/TODO.md
index db1a1e9..16cd926 100644
--- a/TODO.md
+++ b/TODO.md
@@ -26,12 +26,11 @@ Create one shared behavior system for Activity Bar buttons, sidebar ownership, a
 ### B. Click behavior exceptions
 1. No known per-activity click behavior exceptions in `ActivityBar`.
    - Activity buttons now follow one shared posts-style switch/toggle pattern.
-2. Remaining coupling is in sidebar section navigation (`SettingsNav`/`TagsNav`) and is planned for unified section activation API migration.
+2. Sidebar section navigation (`SettingsNav`/`TagsNav`) now uses the shared section activation API.
 
 ### C. Sidebar content exceptions
-1. **Posts/Pages** sidebars are mounted in wrappers with `display: none` when inactive.
-2. **Media/Settings/Tags/Chat/Import/Git** sidebars are conditionally mounted.
-3. **SettingsNav/TagsNav** perform section scrolling and can auto-open corresponding tabs before scroll.
+1. Sidebars use global Variant B conditional mounting.
+2. `SettingsNav`/`TagsNav` section state is persisted for remount-safe UX.
 
 ### D. Editor content exceptions
 1. Editor is primarily tab-driven for tool views (`settings`, `tags`, `chat`, `import`, etc.).
@@ -39,8 +38,8 @@ Create one shared behavior system for Activity Bar buttons, sidebar ownership, a
 3. Some menu commands open tabs directly without harmonizing sidebar ownership.
 
 ### E. API shape exceptions
-1. Multiple places directly implement activity behavior logic instead of shared rules.
-2. Open-tab semantics for singleton activities are duplicated across components.
+1. Activity behavior logic is centralized via shared behavior + execution helpers.
+2. Open-tab semantics are centralized in shared tab policy helpers by tab kind.
 
 ---
 
@@ -221,9 +220,9 @@ Pure tab-policy helpers that decide:
 - [x] Reduce drift between keyboard/menu/toolbar interactions.
 
 ## Phase 6 — Cleanup + Exception Review
-- Reassess every exception in this file and decide keep/remove.
-- Remove dead paths and duplicate helpers.
-- Update tests and docs.
+- [x] Reassess every exception in this file and decide keep/remove.
+- [x] Remove dead paths and duplicate helpers.
+- [x] Update tests and docs.
 
 ---
 
@@ -261,4 +260,5 @@ Pure tab-policy helpers that decide:
 - [x] Phase 4 complete: introduced `editorRouting` registry/resolver and migrated `Editor` to declarative route->view rendering.
 - [x] Phase 5 complete: introduced shared activity action executor and reused it in `ActivityBar` and menu view handlers.
 - [x] Phase 5 complete: `menu:viewPosts` and `menu:viewMedia` now follow the same action pipeline as activity-bar clicks.
-- [ ] Next implementation slice: Phase 6 (cleanup + exception review).
+- [x] Phase 6 complete: removed unused activity behavior metadata/constants and refreshed the exception matrix to current architecture.
+- [ ] Next implementation slice: optional follow-up (further simplification/perf tuning only if new drift appears).
diff --git a/src/renderer/navigation/activityBehavior.ts b/src/renderer/navigation/activityBehavior.ts
index aaf2c06..6c22b50 100644
--- a/src/renderer/navigation/activityBehavior.ts
+++ b/src/renderer/navigation/activityBehavior.ts
@@ -17,7 +17,6 @@ interface ActivityConfig {
   id: ActivityId;
   view: SidebarView;
   labelKey: string;
-  placement: 'top' | 'bottom';
   activeStrategy: ActiveStrategy;
   clickStrategy: ClickStrategy;
 }
@@ -27,7 +26,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'posts',
     view: 'posts',
     labelKey: 'activity.posts',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -35,7 +33,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'pages',
     view: 'pages',
     labelKey: 'activity.pages',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -43,7 +40,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'media',
     view: 'media',
     labelKey: 'activity.media',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -51,7 +47,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'tags',
     view: 'tags',
     labelKey: 'activity.tags',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -59,7 +54,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'chat',
     view: 'chat',
     labelKey: 'activity.aiAssistant',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -67,7 +61,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'import',
     view: 'import',
     labelKey: 'activity.import',
-    placement: 'top',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -75,7 +68,6 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'git',
     view: 'git',
     labelKey: 'activity.sourceControl',
-    placement: 'bottom',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
@@ -83,15 +75,11 @@ const ACTIVITY_CONFIG: Record<ActivityId, ActivityConfig> = {
     id: 'settings',
     view: 'settings',
     labelKey: 'common.settings',
-    placement: 'bottom',
     activeStrategy: 'sidebar-owner',
     clickStrategy: 'sidebar-toggle',
   },
 };
 
-export const TOP_ACTIVITY_IDS: ActivityId[] = ['posts', 'pages', 'media', 'tags', 'chat', 'import'];
-export const BOTTOM_ACTIVITY_IDS: ActivityId[] = ['git', 'settings'];
-
 export function getActivityConfig(activityId: ActivityId): ActivityConfig {
   return ACTIVITY_CONFIG[activityId];
 }