diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 8c6ab7dc..d95e12a0 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -1,6 +1,28 @@
 CHANGELOG - towerops-web
 ========================
 
+2026-02-12 - fix: sync modal state to URL for browser back/forward navigation
+  - Files: lib/towerops_web/live/user_settings_live.ex, lib/towerops_web/live/agent_live/index.ex
+    Fixed browser back/forward button navigation by syncing modal state to URL parameters.
+    Implemented idiomatic Phoenix LiveView pattern using push_patch/2 and handle_params/3.
+
+    **UserSettingsLive (6 modals):**
+    - add_token, token_created, revoke_all, add_device, device_qr, recovery_codes
+    - Updated handle_params/3 to read ?modal= param and set all modal states
+    - Added build_settings_path/2 helper to preserve tab and page params
+    - Updated all show/close handlers to use push_patch instead of assign
+
+    **AgentLive.Index (1 modal):**
+    - setup modal (displays agent token after creation)
+    - Updated handle_params/3 to read ?modal=setup param
+    - Updated show_setup and close_token_modal handlers to use push_patch
+
+    **Result:** Browser back button now closes modals without navigating away from page.
+    URLs are bookmarkable and restore exact modal state. Tab and pagination state preserved.
+
+    **Documentation:** Updated CLAUDE.md with comprehensive browser navigation patterns.
+    Created design document: docs/plans/2026-02-12-browser-navigation-fix-design.md
+
 2026-02-12 - feat: add comprehensive MikroTik wireless sensor discovery (11 sensor types across 4 MIB tables)
   - Files: lib/towerops/snmp/profiles/vendors/mikrotik.ex (enhanced)
     Implemented TIER 4 LARGE priority wireless sensor discovery for MikroTik RouterOS devices.