diff --git a/src/panels/change_notifier.zig b/src/panels/change_notifier.zig
new file mode 100644
index 0000000..6f0894e
--- /dev/null
+++ b/src/panels/change_notifier.zig
@@ -0,0 +1,408 @@
+//! ChangeNotifier - Observer pattern for panel communication
+//!
+//! Provides:
+//! - Observer registration by entity type
+//! - Notification of data changes
+//! - Decoupled panel-to-panel communication
+//!
+//! Panels subscribe to entity types they care about and receive
+//! notifications when data changes, without knowing about other panels.
+//!
+//! NOTE: This is NOT a data store. For application-specific data management
+//! (BD access, caching, etc.), create a separate DataManager in your app.
+
+const std = @import("std");
+
+// =============================================================================
+// Types
+// =============================================================================
+
+/// Change type
+pub const ChangeType = enum {
+    /// Entity created
+    create,
+    /// Entity updated
+    update,
+    /// Entity deleted
+    delete,
+    /// Selection changed
+    select,
+    /// Refresh requested
+    refresh,
+};
+
+/// Data change event
+pub const DataChange = struct {
+    /// Entity type (e.g., "Customer", "Document")
+    entity_type: []const u8,
+    /// Type of change
+    change_type: ChangeType,
+    /// Changed data (opaque pointer to entity)
+    data: ?*anyopaque = null,
+    /// Entity ID (if applicable)
+    entity_id: ?u64 = null,
+    /// Source panel ID (to avoid self-notification)
+    source_panel: ?[]const u8 = null,
+};
+
+/// Observer callback signature
+pub const ObserverCallback = *const fn (change: DataChange, context: ?*anyopaque) void;
+
+/// Observer entry
+pub const Observer = struct {
+    /// Callback function
+    callback: ObserverCallback,
+    /// User context
+    context: ?*anyopaque = null,
+    /// Observer ID (for removal)
+    id: []const u8 = "",
+};
+
+// =============================================================================
+// Data Manager
+// =============================================================================
+
+/// Maximum observers per entity type
+pub const MAX_OBSERVERS_PER_TYPE = 32;
+/// Maximum entity types
+pub const MAX_ENTITY_TYPES = 64;
+
+/// ChangeNotifier - central hub for change notifications between panels
+pub const ChangeNotifier = struct {
+    /// Observers by entity type (simple array-based for now)
+    entity_types: [MAX_ENTITY_TYPES]?[]const u8 = [_]?[]const u8{null} ** MAX_ENTITY_TYPES,
+    observers: [MAX_ENTITY_TYPES][MAX_OBSERVERS_PER_TYPE]?Observer = [_][MAX_OBSERVERS_PER_TYPE]?Observer{[_]?Observer{null} ** MAX_OBSERVERS_PER_TYPE} ** MAX_ENTITY_TYPES,
+    observer_counts: [MAX_ENTITY_TYPES]usize = [_]usize{0} ** MAX_ENTITY_TYPES,
+    entity_type_count: usize = 0,
+
+    /// Global observers (receive all changes)
+    global_observers: [MAX_OBSERVERS_PER_TYPE]?Observer = [_]?Observer{null} ** MAX_OBSERVERS_PER_TYPE,
+    global_observer_count: usize = 0,
+
+    const Self = @This();
+
+    /// Initialize data manager
+    pub fn init() Self {
+        return Self{};
+    }
+
+    /// Find entity type index (or create new)
+    fn findOrCreateEntityType(self: *Self, entity_type: []const u8) ?usize {
+        // Search existing
+        for (0..self.entity_type_count) |i| {
+            if (self.entity_types[i]) |et| {
+                if (std.mem.eql(u8, et, entity_type)) {
+                    return i;
+                }
+            }
+        }
+
+        // Create new
+        if (self.entity_type_count < MAX_ENTITY_TYPES) {
+            const idx = self.entity_type_count;
+            self.entity_types[idx] = entity_type;
+            self.entity_type_count += 1;
+            return idx;
+        }
+
+        return null;
+    }
+
+    /// Find entity type index
+    fn findEntityType(self: Self, entity_type: []const u8) ?usize {
+        for (0..self.entity_type_count) |i| {
+            if (self.entity_types[i]) |et| {
+                if (std.mem.eql(u8, et, entity_type)) {
+                    return i;
+                }
+            }
+        }
+        return null;
+    }
+
+    /// Add observer for specific entity type
+    pub fn addObserver(self: *Self, entity_type: []const u8, observer: Observer) bool {
+        const idx = self.findOrCreateEntityType(entity_type) orelse return false;
+
+        if (self.observer_counts[idx] >= MAX_OBSERVERS_PER_TYPE) {
+            return false;
+        }
+
+        self.observers[idx][self.observer_counts[idx]] = observer;
+        self.observer_counts[idx] += 1;
+        return true;
+    }
+
+    /// Add global observer (receives all changes)
+    pub fn addGlobalObserver(self: *Self, observer: Observer) bool {
+        if (self.global_observer_count >= MAX_OBSERVERS_PER_TYPE) {
+            return false;
+        }
+
+        self.global_observers[self.global_observer_count] = observer;
+        self.global_observer_count += 1;
+        return true;
+    }
+
+    /// Remove observer by ID
+    pub fn removeObserver(self: *Self, entity_type: []const u8, observer_id: []const u8) bool {
+        const idx = self.findEntityType(entity_type) orelse return false;
+
+        for (0..self.observer_counts[idx]) |i| {
+            if (self.observers[idx][i]) |obs| {
+                if (std.mem.eql(u8, obs.id, observer_id)) {
+                    // Shift remaining observers
+                    var j = i;
+                    while (j < self.observer_counts[idx] - 1) : (j += 1) {
+                        self.observers[idx][j] = self.observers[idx][j + 1];
+                    }
+                    self.observers[idx][self.observer_counts[idx] - 1] = null;
+                    self.observer_counts[idx] -= 1;
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    /// Remove global observer by ID
+    pub fn removeGlobalObserver(self: *Self, observer_id: []const u8) bool {
+        for (0..self.global_observer_count) |i| {
+            if (self.global_observers[i]) |obs| {
+                if (std.mem.eql(u8, obs.id, observer_id)) {
+                    // Shift remaining
+                    var j = i;
+                    while (j < self.global_observer_count - 1) : (j += 1) {
+                        self.global_observers[j] = self.global_observers[j + 1];
+                    }
+                    self.global_observers[self.global_observer_count - 1] = null;
+                    self.global_observer_count -= 1;
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    /// Notify observers of a change
+    pub fn notifyChange(self: *Self, change: DataChange) void {
+        // Notify type-specific observers
+        if (self.findEntityType(change.entity_type)) |idx| {
+            for (0..self.observer_counts[idx]) |i| {
+                if (self.observers[idx][i]) |obs| {
+                    // Skip if this is the source panel
+                    if (change.source_panel) |source| {
+                        if (obs.id.len > 0 and std.mem.eql(u8, obs.id, source)) {
+                            continue;
+                        }
+                    }
+                    obs.callback(change, obs.context);
+                }
+            }
+        }
+
+        // Notify global observers
+        for (0..self.global_observer_count) |i| {
+            if (self.global_observers[i]) |obs| {
+                if (change.source_panel) |source| {
+                    if (obs.id.len > 0 and std.mem.eql(u8, obs.id, source)) {
+                        continue;
+                    }
+                }
+                obs.callback(change, obs.context);
+            }
+        }
+    }
+
+    /// Convenience: notify entity update
+    pub fn notifyUpdate(self: *Self, entity_type: []const u8, data: ?*anyopaque) void {
+        self.notifyChange(.{
+            .entity_type = entity_type,
+            .change_type = .update,
+            .data = data,
+        });
+    }
+
+    /// Convenience: notify entity selection
+    pub fn notifySelect(self: *Self, entity_type: []const u8, data: ?*anyopaque) void {
+        self.notifyChange(.{
+            .entity_type = entity_type,
+            .change_type = .select,
+            .data = data,
+        });
+    }
+
+    /// Convenience: notify entity create
+    pub fn notifyCreate(self: *Self, entity_type: []const u8, data: ?*anyopaque) void {
+        self.notifyChange(.{
+            .entity_type = entity_type,
+            .change_type = .create,
+            .data = data,
+        });
+    }
+
+    /// Convenience: notify entity delete
+    pub fn notifyDelete(self: *Self, entity_type: []const u8, entity_id: u64) void {
+        self.notifyChange(.{
+            .entity_type = entity_type,
+            .change_type = .delete,
+            .entity_id = entity_id,
+        });
+    }
+
+    /// Convenience: request refresh
+    pub fn notifyRefresh(self: *Self, entity_type: []const u8) void {
+        self.notifyChange(.{
+            .entity_type = entity_type,
+            .change_type = .refresh,
+        });
+    }
+
+    /// Get observer count for entity type
+    pub fn getObserverCount(self: Self, entity_type: []const u8) usize {
+        if (self.findEntityType(entity_type)) |idx| {
+            return self.observer_counts[idx];
+        }
+        return 0;
+    }
+
+    /// Check if has observers for entity type
+    pub fn hasObservers(self: Self, entity_type: []const u8) bool {
+        return self.getObserverCount(entity_type) > 0;
+    }
+};
+
+// =============================================================================
+// Global ChangeNotifier Instance
+// =============================================================================
+
+/// Global change notifier instance
+var global_notifier: ?*ChangeNotifier = null;
+
+/// Get or create global change notifier
+pub fn getChangeNotifier() *ChangeNotifier {
+    if (global_notifier) |n| {
+        return n;
+    }
+    // Note: In real usage, this should be properly allocated
+    // For now, using a static instance
+    const S = struct {
+        var instance: ChangeNotifier = ChangeNotifier.init();
+    };
+    global_notifier = &S.instance;
+    return &S.instance;
+}
+
+/// Set global change notifier
+pub fn setChangeNotifier(n: *ChangeNotifier) void {
+    global_notifier = n;
+}
+
+// =============================================================================
+// Tests
+// =============================================================================
+
+test "ChangeNotifier basic" {
+    var dm = ChangeNotifier.init();
+
+    var received_count: usize = 0;
+
+    const callback = struct {
+        fn cb(change: DataChange, context: ?*anyopaque) void {
+            _ = change;
+            if (context) |ctx| {
+                const count: *usize = @ptrCast(@alignCast(ctx));
+                count.* += 1;
+            }
+        }
+    }.cb;
+
+    // Add observer
+    try std.testing.expect(dm.addObserver("Customer", .{
+        .callback = callback,
+        .context = &received_count,
+        .id = "test_observer",
+    }));
+
+    try std.testing.expectEqual(@as(usize, 1), dm.getObserverCount("Customer"));
+
+    // Notify
+    dm.notifyUpdate("Customer", null);
+    try std.testing.expectEqual(@as(usize, 1), received_count);
+
+    // Different entity type - no notification
+    dm.notifyUpdate("Product", null);
+    try std.testing.expectEqual(@as(usize, 1), received_count);
+
+    // Remove observer
+    try std.testing.expect(dm.removeObserver("Customer", "test_observer"));
+    try std.testing.expectEqual(@as(usize, 0), dm.getObserverCount("Customer"));
+}
+
+test "ChangeNotifier global observer" {
+    var dm = ChangeNotifier.init();
+
+    var received_count: usize = 0;
+
+    const callback = struct {
+        fn cb(change: DataChange, context: ?*anyopaque) void {
+            _ = change;
+            if (context) |ctx| {
+                const count: *usize = @ptrCast(@alignCast(ctx));
+                count.* += 1;
+            }
+        }
+    }.cb;
+
+    // Add global observer
+    try std.testing.expect(dm.addGlobalObserver(.{
+        .callback = callback,
+        .context = &received_count,
+        .id = "global",
+    }));
+
+    // Should receive all notifications
+    dm.notifyUpdate("Customer", null);
+    dm.notifyUpdate("Product", null);
+    dm.notifyUpdate("Order", null);
+
+    try std.testing.expectEqual(@as(usize, 3), received_count);
+}
+
+test "ChangeNotifier source panel skip" {
+    var dm = ChangeNotifier.init();
+
+    var received_count: usize = 0;
+
+    const callback = struct {
+        fn cb(change: DataChange, context: ?*anyopaque) void {
+            _ = change;
+            if (context) |ctx| {
+                const count: *usize = @ptrCast(@alignCast(ctx));
+                count.* += 1;
+            }
+        }
+    }.cb;
+
+    _ = dm.addObserver("Customer", .{
+        .callback = callback,
+        .context = &received_count,
+        .id = "panel_a",
+    });
+
+    _ = dm.addObserver("Customer", .{
+        .callback = callback,
+        .context = &received_count,
+        .id = "panel_b",
+    });
+
+    // Notify with source - should skip panel_a
+    dm.notifyChange(.{
+        .entity_type = "Customer",
+        .change_type = .update,
+        .source_panel = "panel_a",
+    });
+
+    // Only panel_b should receive
+    try std.testing.expectEqual(@as(usize, 1), received_count);
+}
diff --git a/src/panels/panel.zig b/src/panels/panel.zig
index 4fd2e20..31a3283 100644
--- a/src/panels/panel.zig
+++ b/src/panels/panel.zig
@@ -4,7 +4,7 @@
 //! - Each panel is autonomous (owns state, UI, logic)
 //! - Panels are reusable across windows
 //! - Windows compose panels (not inheritance)
-//! - Communication via DataManager (observer pattern)
+//! - Communication via ChangeNotifier (observer pattern)
 
 const std = @import("std");
 const Context = @import("../core/context.zig").Context;
diff --git a/src/panels/panels.zig b/src/panels/panels.zig
index a88f566..b3518b4 100644
--- a/src/panels/panels.zig
+++ b/src/panels/panels.zig
@@ -3,14 +3,14 @@
 //! This module provides:
 //! - AutonomousPanel: Self-contained UI component
 //! - Composite patterns: Vertical, Horizontal, Split, Tab, Grid
-//! - DataManager: Observer pattern for panel communication
+//! - ChangeNotifier: Observer pattern for panel communication
 //! - Detail: Components for detail/edit panels (state machine, semaphore, buttons)
 //!
 //! Architecture based on Simifactu's Lego Panels system:
 //! - Panels are autonomous (own state, UI, logic)
 //! - Panels are reusable across windows
 //! - Windows compose panels (not inheritance)
-//! - Communication via DataManager (observer pattern)
+//! - Communication via ChangeNotifier (observer pattern)
 
 const std = @import("std");
 
@@ -20,7 +20,7 @@ const std = @import("std");
 
 pub const panel = @import("panel.zig");
 pub const composite = @import("composite.zig");
-pub const data_manager = @import("data_manager.zig");
+pub const change_notifier = @import("change_notifier.zig");
 pub const detail = @import("detail/detail.zig");
 
 // =============================================================================
@@ -49,16 +49,16 @@ pub const TabState = composite.TabState;
 pub const GridComposite = composite.GridComposite;
 
 // =============================================================================
-// Data Manager types
+// ChangeNotifier types (for panel-to-panel communication)
 // =============================================================================
 
-pub const DataManager = data_manager.DataManager;
-pub const DataChange = data_manager.DataChange;
-pub const ChangeType = data_manager.ChangeType;
-pub const Observer = data_manager.Observer;
-pub const ObserverCallback = data_manager.ObserverCallback;
-pub const getDataManager = data_manager.getDataManager;
-pub const setDataManager = data_manager.setDataManager;
+pub const ChangeNotifier = change_notifier.ChangeNotifier;
+pub const DataChange = change_notifier.DataChange;
+pub const ChangeType = change_notifier.ChangeType;
+pub const Observer = change_notifier.Observer;
+pub const ObserverCallback = change_notifier.ObserverCallback;
+pub const getChangeNotifier = change_notifier.getChangeNotifier;
+pub const setChangeNotifier = change_notifier.setChangeNotifier;
 
 // =============================================================================
 // Detail Panel types (for edit/detail panels)