diff --git a/docs/CONFIGURATION.md b/docs/CONFIGURATION.md
index a0e3329..1fe859f 100644
--- a/docs/CONFIGURATION.md
+++ b/docs/CONFIGURATION.md
@@ -71,6 +71,57 @@ borders {
 
 Colors are specified in `0xRRGGBB` or `0xRRGGBBAA` hex format.
 
+## Window Rules
+
+Window rules let you set certain properties on windows when they first appear,
+based on their `app_id` and/or `title`. Crucially, you can override them any time after
+that, it's only when the window is first created. Rules are placed inside a `window_rules` block:
+
+```kdl
+window_rules {
+    // Float Firefox picture-in-picture windows
+    float app_id="firefox" title="Picture-in-Picture"
+    // Float any window with "Preferences" in the title
+    float title="*Preferences*"
+    // Keep mpv windows tiled
+    no_float app_id="mpv"
+    // Send Slack to tag 3 (1<<2 = 0x0004)
+    tags 0x0004 app_id="Slack"
+}
+```
+
+### Rule Types
+
+| Rule       | Argument         | Description                              |
+|------------|------------------|------------------------------------------|
+| `float`    |                  | Make matching windows float              |
+| `no_float` |                  | Keep matching windows tiled              |
+| `tags`     | u32 (bitmask)    | Assign matching windows to specific tags |
+
+### Matching
+
+Each rule can have an `app_id=` and/or `title=` property. Both support glob patterns:
+
+| Pattern       | Matches                        |
+|---------------|--------------------------------|
+| `"foo"`       | Exact match only               |
+| `"foo*"`      | Starts with "foo"              |
+| `"*foo"`      | Ends with "foo"                |
+| `"*foo*"`     | Contains "foo"                 |
+| `"*"`         | Everything                     |
+
+A rule with no `app_id=` or `title=` property matches all windows. If both are
+specified, both must match.
+
+### Evaluation
+
+Rules are evaluated top-to-bottom. Each matching rule applies only the properties it
+specifies, so multiple rules can contribute different properties to the same window.
+For the same property, later rules override earlier ones.
+
+Rules are applied once during window initialization. Title changes after initialization
+do not re-trigger rules.
+
 ## Bar
 
 The bar is an optional widget that shows the time on your screen. Right now, that's it.
diff --git a/docs/TODO.md b/docs/TODO.md
index e9ef37c..531002e 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -2,7 +2,8 @@
 
 These are in rough order of my priority, though no promises I do them in this order.
 
-- [ ] Support window rules (float/tags/SSD by app-id/title)
+- [ ] Move orphan handling out of .output and .seat events; into manage()
+- [ ] Add focused window title to bar
 - [ ] Support overriding config location
 - [ ] Support configuring primary vs secondary stack side
 - [ ] Support switch handling (e.g. lid close)
@@ -31,3 +32,5 @@ These are in rough order of my priority, though no promises I do them in this or
 - [x] Add options to the tag overlay
 - [x] Add options to the bar
 - [x] Make a Rect struct to combine x, y, width, and height
+- [x] Support window rules (float/tags by app-id/title)
+- [x] Fix resizing size when you pop a window out, basically, it start with its current size but then when you try resize it goes to 75%
diff --git a/examples/config.kdl b/examples/config.kdl
index 9be9915..63e09e6 100644
--- a/examples/config.kdl
+++ b/examples/config.kdl
@@ -18,11 +18,11 @@ borders {
     color_focused "0x89b4fa"
     color_unfocused "0x1e1e2e"
 }
-// Bar widget - shows the time
+// Bar widget; shows the time
 bar {
     position top
 }
-// Tag overlay widget - shown briefly when switching tags
+// Tag overlay widget; shown briefly when switching tags
 // Remove this block to disable the overlay entirely
 tag_overlay {
     tag_amount 10
@@ -35,6 +35,18 @@ tag_overlay {
     square_inactive_border_color "0x6c7086"
     square_inactive_occupied_color "0xcdd6f4"
 }
+// Window rules; applied once when a window first appears
+// Rules are evaluated top-to-bottom; later rules override earlier ones
+window_rules {
+    // Float Firefox picture-in-picture windows
+    float app_id="firefox" title="Picture-in-Picture"
+    // Float any window with "Preferences" in the title
+    float title="*Preferences*"
+    // Keep mpv windows tiled
+    no_float app_id="mpv"
+    // Send Slack to tag 3 (1<<2 = 0x0004)
+    tags 0x0004 app_id="Slack"
+}
 keybinds {
     // Swap a window
     spawn Mod4 T foot
diff --git a/src/Config.zig b/src/Config.zig
index 29e0669..2f5ac81 100644
--- a/src/Config.zig
+++ b/src/Config.zig
@@ -42,10 +42,13 @@ tag_binds: std.ArrayList(Keybind) = .{},
 keybinds: keybind.Map = .{},
 pointer_binds: std.ArrayList(PointerBind) = .{},
 input_configs: std.ArrayList(InputConfig) = .{},
+window_rules: std.ArrayList(WindowRule) = .{},
 
 // Re-exports
 pub const Keybind = keybind.Keybind;
 pub const PointerBind = pointer_bind.PointerBind;
+pub const WindowRule = window_rule.Rule;
+pub const WindowRuleAction = window_rule.Action;
 
 pub const AttachMode = enum {
     top,
@@ -66,6 +69,7 @@ const NodeName = enum {
     keybinds,
     pointer_binds,
     tag_overlay,
+    window_rules,
 };
 
 pub fn create() !*Config {
@@ -103,6 +107,11 @@ pub fn create() !*Config {
                 if (ic.name) |name| utils.gpa.free(name);
             }
             config.input_configs.clearAndFree(utils.gpa);
+            for (config.window_rules.items) |rule| {
+                if (rule.app_id_glob) |app_id_glob| utils.gpa.free(app_id_glob);
+                if (rule.title_glob) |title_glob| utils.gpa.free(title_glob);
+            }
+            config.window_rules.clearAndFree(utils.gpa);
             if (config.bar_config) |bc| {
                 if (bc.fonts) |fonts| utils.gpa.free(fonts);
             }
@@ -133,6 +142,11 @@ pub fn destroy(config: *Config) void {
         if (ic.name) |name| utils.gpa.free(name);
     }
     config.input_configs.deinit(utils.gpa);
+    for (config.window_rules.items) |rule| {
+        if (rule.app_id_glob) |app_id_glob| utils.gpa.free(app_id_glob);
+        if (rule.title_glob) |title_glob| utils.gpa.free(title_glob);
+    }
+    config.window_rules.deinit(utils.gpa);
     if (config.bar_config) |bc| {
         if (bc.fonts) |fonts| utils.gpa.free(fonts);
     }
@@ -210,7 +224,7 @@ fn load(config: *Config, reader: *Io.Reader) !void {
                             if (helpers.boolFromKdlStr(focus_follows_pointer_str)) |focus_follows_pointer| {
                                 config.focus_follows_pointer = focus_follows_pointer;
                                 logDebugSettingNode(name, focus_follows_pointer_str);
-                            } else {
+                            } else |_| {
                                 logWarnInvalidNodeArg(name, focus_follows_pointer_str);
                                 continue;
                             }
@@ -220,7 +234,7 @@ fn load(config: *Config, reader: *Io.Reader) !void {
                             if (helpers.boolFromKdlStr(pointer_warp_on_focus_change_str)) |pointer_warp_on_focus_change| {
                                 config.pointer_warp_on_focus_change = pointer_warp_on_focus_change;
                                 logDebugSettingNode(name, pointer_warp_on_focus_change_str);
-                            } else {
+                            } else |_| {
                                 logWarnInvalidNodeArg(name, pointer_warp_on_focus_change_str);
                                 continue;
                             }
@@ -238,8 +252,6 @@ fn load(config: *Config, reader: *Io.Reader) !void {
                             };
                             logDebugSettingNode(name, path_str);
                         },
-                        .bar => next_child_block = .bar,
-                        .borders => next_child_block = .borders,
                         .input => {
                             pending_input_name = if (node.prop(&parser, "name")) |n|
                                 try utils.gpa.dupe(u8, utils.stripQuotes(n))
@@ -247,15 +259,13 @@ fn load(config: *Config, reader: *Io.Reader) !void {
                                 null;
                             next_child_block = .input;
                         },
-                        .keybinds => {
-                            next_child_block = .keybinds;
-                        },
-                        .pointer_binds => {
-                            next_child_block = .pointer_binds;
-                        },
-                        .tag_overlay => {
-                            next_child_block = .tag_overlay;
-                        },
+                        inline .bar,
+                        .borders,
+                        .keybinds,
+                        .pointer_binds,
+                        .tag_overlay,
+                        .window_rules,
+                        => |n| next_child_block = n,
                     }
                 } else {
                     helpers.logWarnInvalidNode(node.name);
@@ -273,6 +283,7 @@ fn load(config: *Config, reader: *Io.Reader) !void {
                             pending_input_name = null; // ownership transferred
                         },
                         .tag_overlay => try TagOverlayConfig.load(config, &parser, hostname),
+                        .window_rules => try window_rule.load(config, &parser, hostname),
                         else => {
                             // Nothing else should ever be marked as a next_child_block
                             unreachable;
@@ -322,6 +333,7 @@ const border = @import("config/border.zig");
 const helpers = @import("config/helpers.zig");
 const keybind = @import("config/keybind.zig");
 const pointer_bind = @import("config/pointer_bind.zig");
+const window_rule = @import("config/window_rule.zig");
 const BarConfig = @import("config/BarConfig.zig");
 const InputConfig = @import("config/InputConfig.zig");
 const TagOverlayConfig = @import("config/TagOverlayConfig.zig");
diff --git a/src/Output.zig b/src/Output.zig
index ec65420..c07e682 100644
--- a/src/Output.zig
+++ b/src/Output.zig
@@ -576,8 +576,11 @@ pub fn manage(output: *Output) void {
         }
     }
 
-    // Calculate layout before managing windows
-    output.calculatePrimaryStackLayout();
+    // Calculate layout before managing windows, but only if output dimensions are initialized
+    if (output.usable_geometry.width > 0 and output.usable_geometry.height > 0) {
+        output.calculateLayout();
+    }
+
     var it = output.windows.iterator(.forward);
     while (it.next()) |window| {
         window.manage();
@@ -611,12 +614,17 @@ pub fn render(output: *Output) void {
 /// Calculate primary/stack layout positions for all windows.
 /// - Single window: maximized
 /// - Multiple windows: stack (45% left, vertically tiled), primary (55% right)
-fn calculatePrimaryStackLayout(output: *Output) void {
+fn calculateLayout(output: *Output) void {
+    // Shouldn't be called if height/width are not positive
+    assert(output.geometry.width > 0 and output.geometry.height > 0);
     // Get a list of active windows
     var active_list: DoublyLinkedList = .{};
     var active_count: u31 = 0;
     var it = output.windows.iterator(.forward);
     while (it.next()) |window| {
+        // Initialize new windows before checking tags/float so that
+        // window rules are reflected in the first frame's layout.
+        window.initialize();
         if (output.tags & window.tags != 0x0000) {
             // Floating windows should be shown but not included in this layout generation
             const will_float = window.pending_manage.floating orelse window.floating;
@@ -711,8 +719,14 @@ fn calculatePrimaryStackLayout(output: *Output) void {
         }
 
         // Make space for borders
-        window.pending_manage.dimensions.?.height -= 2 * border_width;
-        window.pending_manage.dimensions.?.width -= 2 * border_width;
+        if (window.pending_manage.dimensions.?.height > 2 * border_width and
+            window.pending_manage.dimensions.?.width > 2 * border_width)
+        {
+            window.pending_manage.dimensions.?.height -= 2 * border_width;
+            window.pending_manage.dimensions.?.width -= 2 * border_width;
+        } else {
+            log.warn("Can't add borders to some window; {s}'s dimensions are too small.", .{output.name orelse "some output"});
+        }
         window.pending_render.position.?.x += border_width;
         window.pending_render.position.?.y += border_width;
     }
diff --git a/src/Window.zig b/src/Window.zig
index ed55093..a21004e 100644
--- a/src/Window.zig
+++ b/src/Window.zig
@@ -9,6 +9,10 @@ context: *Context,
 river_window_v1: *river.WindowV1,
 river_node_v1: *river.NodeV1,
 
+app_id: ?[]const u8 = null,
+title: ?[]const u8 = null,
+parent: ?*river.WindowV1 = null,
+
 rect: utils.Rect = .{},
 
 fullscreen: bool = false,
@@ -19,6 +23,7 @@ output: ?*Output,
 
 floating: bool = false,
 floating_rect: utils.Rect = .{},
+dimensions_hint: DimensionsHint = .{},
 
 initialized: bool = false,
 
@@ -61,6 +66,29 @@ pub const PendingRender = struct {
     show: ?bool = null,
 };
 
+pub const DimensionsHint = struct {
+    min_width: u31 = 0,
+    min_height: u31 = 0,
+    max_width: u31 = 0,
+    max_height: u31 = 0,
+
+    fn clampWidth(hint: DimensionsHint, width: u31) u31 {
+        return math.clamp(
+            width,
+            if (hint.min_width != 0) hint.min_width else 1,
+            if (hint.max_width != 0) hint.max_width else math.maxInt(u31),
+        );
+    }
+
+    fn clampHeight(hint: DimensionsHint, height: u31) u31 {
+        return math.clamp(
+            height,
+            if (hint.min_height != 0) hint.min_height else 1,
+            if (hint.max_height != 0) hint.max_height else math.maxInt(u31),
+        );
+    }
+};
+
 pub fn create(context: *Context, river_window_v1: *river.WindowV1, output: ?*Output) !*Window {
     var window = try utils.gpa.create(Window);
     errdefer utils.gpa.destroy(window);
@@ -80,8 +108,11 @@ pub fn create(context: *Context, river_window_v1: *river.WindowV1, output: ?*Out
 }
 
 pub fn destroy(window: *Window) void {
-    window.river_window_v1.destroy();
+    if (window.app_id) |app_id| utils.gpa.free(app_id);
+    if (window.title) |title| utils.gpa.free(title);
+
     window.river_node_v1.destroy();
+    window.river_window_v1.destroy();
 
     utils.gpa.destroy(window);
 }
@@ -111,22 +142,23 @@ fn windowListener(river_window_v1: *river.WindowV1, event: river.WindowV1.Event,
                         seat.pending_manage.pointer_resize_request = null;
                 }
             }
-            // If there's no output, we don't really care about focus and can skip this event
-            const output = if (window.output) |output| output else return;
-            var it = window.context.wm.seats.iterator(.forward);
-            while (it.next()) |seat| {
-                if (seat.focused_window == window) {
-                    // Find another window to focus and warp pointer there
-                    if (output.prevWindow(window)) |next_focus| {
-                        if (next_focus != window) {
-                            seat.pending_manage.window = .{ .window = next_focus };
-                            seat.pending_manage.should_warp_pointer = true;
+            if (window.output) |output| {
+                // Get a new window for the wm to focus
+                var it = window.context.wm.seats.iterator(.forward);
+                while (it.next()) |seat| {
+                    if (seat.focused_window == window) {
+                        // Find another window to focus and warp pointer there
+                        if (output.prevWindow(window)) |next_focus| {
+                            if (next_focus != window) {
+                                seat.pending_manage.window = .{ .window = next_focus };
+                                seat.pending_manage.should_warp_pointer = true;
+                            } else {
+                                // Only window in list - clear focus
+                                seat.pending_manage.window = .clear_focus;
+                            }
                         } else {
-                            // Only window in list - clear focus
                             seat.pending_manage.window = .clear_focus;
                         }
-                    } else {
-                        seat.pending_manage.window = .clear_focus;
                     }
                 }
             }
@@ -138,8 +170,39 @@ fn windowListener(river_window_v1: *river.WindowV1, event: river.WindowV1.Event,
             assert(ev.width > 0 and ev.height > 0);
             window.pending_manage.dimensions = .{ .width = @intCast(ev.width), .height = @intCast(ev.height) };
         },
-        .dimensions_hint => {
-            // TODO: Maybe could use this for floating windows
+        .dimensions_hint => |ev| {
+            window.dimensions_hint = .{
+                .min_width = @intCast(ev.min_width),
+                .min_height = @intCast(ev.min_height),
+                .max_width = @intCast(ev.max_width),
+                .max_height = @intCast(ev.max_height),
+            };
+        },
+        .app_id => |ev| {
+            if (window.app_id) |app_id| utils.gpa.free(app_id);
+            window.app_id = if (ev.app_id) |aid|
+                utils.gpa.dupe(u8, std.mem.span(aid)) catch @panic("Out of memory")
+            else
+                null;
+        },
+        .title => |ev| {
+            if (window.title) |title| utils.gpa.free(title);
+            window.title = if (ev.title) |t|
+                utils.gpa.dupe(u8, std.mem.span(t)) catch @panic("Out of memory")
+            else
+                null;
+        },
+        .parent => |ev| {
+            const parent = ev.parent orelse return;
+            window.parent = parent;
+
+            // Make window float on top of its parent
+            window.pending_manage.floating = true;
+            const parent_window: *Window = @ptrCast(@alignCast(parent.getUserData() orelse return));
+            window.pending_render.position = .{
+                .x = parent_window.rect.x + @divTrunc(parent_window.rect.width, 2),
+                .y = parent_window.rect.y + @divTrunc(parent_window.rect.height, 2),
+            };
         },
         else => |ev| {
             log.debug("unhandled event: {s}", .{@tagName(ev)});
@@ -147,25 +210,38 @@ fn windowListener(river_window_v1: *river.WindowV1, event: river.WindowV1.Event,
     }
 }
 
-pub fn manage(window: *Window) void {
-    const river_window_v1 = window.river_window_v1;
-    if (!window.initialized) {
-        // Only happens once per Window
+/// Apply one-time initialization for newly created windows.
+/// Called before calculatePrimaryStackLayout() so that tag and float
+/// rules are reflected in the first frame's layout.
+pub fn initialize(window: *Window) void {
+    if (window.initialized) {
         @branchHint(.unlikely);
-        window.initialized = true;
-
-        // TODO: We might want to think about paying attention to the decoration_hint event
-        //       If we do, this would need to move, I think?
-        river_window_v1.useSsd();
-
-        river_window_v1.setCapabilities(.{ .fullscreen = true, .maximize = true });
-        river_window_v1.setTiled(.{ .top = true, .bottom = true, .left = true, .right = true });
+        return;
     }
+    window.initialized = true;
 
+    const river_window_v1 = window.river_window_v1;
+
+    // TODO: We might want to think about paying attention to the decoration_hint event
+    //       If we do, this would need to move, I think?
+    river_window_v1.useSsd();
+
+    river_window_v1.setCapabilities(.{ .fullscreen = true, .maximize = true });
+    river_window_v1.setTiled(.{ .top = true, .bottom = true, .left = true, .right = true });
+
+    const res = window.applyRules();
+    if (res.tags) |tags| window.tags = tags;
+    if (res.float) |should_float|
+        window.pending_manage.floating = should_float;
+}
+
+pub fn manage(window: *Window) void {
     // Updating state since the last manage event
     defer window.pending_manage = .{};
     const pending_manage = window.pending_manage;
+    const river_window_v1 = window.river_window_v1;
     // Floating status
+    var became_floating = false;
     if (pending_manage.floating) |floating| blk: {
         // This needs to be before proposing the new dimensions since we want to save the current ones!
         // Skip the rest of the block if floating matches what is already set
@@ -173,14 +249,16 @@ pub fn manage(window: *Window) void {
 
         window.floating = floating;
         if (floating) {
+            became_floating = true;
             // Let the window know it isn't tiled
             river_window_v1.setTiled(.{});
 
             if (window.floating_rect.width == 0) {
-                // Never floated before; use 75% of usable area, centered on output
+                // This window has never floated before, let's give it floating dimensions.
+                // Use 75% of the output's usable size, clamped to the window's dimension hints.
                 if (window.output) |output| {
-                    window.floating_rect.width = @divFloor(output.usable_geometry.width * 3, 4);
-                    window.floating_rect.height = @divFloor(output.usable_geometry.height * 3, 4);
+                    window.floating_rect.width = window.dimensions_hint.clampWidth(@divFloor(output.usable_geometry.width * 3, 4));
+                    window.floating_rect.height = window.dimensions_hint.clampHeight(@divFloor(output.usable_geometry.height * 3, 4));
                     window.floating_rect.x = output.usable_geometry.x + @divFloor(output.usable_geometry.width, 2) - @divFloor(window.floating_rect.width, 2);
                     window.floating_rect.y = output.usable_geometry.y + @divFloor(output.usable_geometry.height, 2) - @divFloor(window.floating_rect.height, 2);
                 } else {
@@ -202,11 +280,14 @@ pub fn manage(window: *Window) void {
             window.floating_rect.y = window.rect.y;
         }
     }
-    // Layout (pre-computed by WindowManager.calculatePrimaryStackLayout())
+    // Layout (pre-computed by WindowManager.caluclateLayout())
     if (pending_manage.dimensions) |dimensions| {
         window.rect.width = dimensions.width;
         window.rect.height = dimensions.height;
-        window.river_window_v1.proposeDimensions(dimensions.width, dimensions.height);
+        if (!became_floating) {
+            // We want to skip this if the floating block above already proposed dimensions
+            window.river_window_v1.proposeDimensions(dimensions.width, dimensions.height);
+        }
     }
     // Fullscreen and maximize operations
     if (pending_manage.fullscreen) |fullscreen| blk: {
@@ -280,17 +361,51 @@ fn applyBorders(window: *Window, color: utils.RiverColor) void {
     window.river_window_v1.setBorders(all_sides, border_width, color.red, color.green, color.blue, color.alpha);
 }
 
+// Iterate over all window rules and apply any that match.
+// Later rules in the list overwrite earlier ones.
+fn applyRules(window: *Window) struct {
+    float: ?bool = null,
+    tags: ?u32 = null,
+} {
+    var float: ?bool = null;
+    var tags: ?u32 = null;
+    for (window.context.config.window_rules.items) |rule| {
+        const app_id_matches = if (rule.app_id_glob) |glob|
+            if (window.app_id) |app_id| globber.match(app_id, glob) else false
+        else
+            true;
+        const title_matches = if (rule.title_glob) |glob|
+            if (window.title) |title| globber.match(title, glob) else false
+        else
+            true;
+        if (app_id_matches and title_matches) {
+            switch (rule.action) {
+                .float => |should_float| float = should_float,
+                .tags => |tagmask| tags = tagmask,
+            }
+        }
+    }
+
+    return .{
+        .float = float,
+        .tags = tags,
+    };
+}
+
 const std = @import("std");
 const assert = std.debug.assert;
+const math = std.math;
 const DoublyLinkedList = std.DoublyLinkedList;
 
 const wayland = @import("wayland");
 const wl = wayland.client.wl;
 const river = wayland.client.river;
 
+const globber = @import("globber.zig");
 const utils = @import("utils.zig");
 const Context = @import("Context.zig");
 const Output = @import("Output.zig");
 const Seat = @import("Seat.zig");
+const WindowRule = @import("Config.zig").WindowRule;
 
 const log = std.log.scoped(.Window);
diff --git a/src/WindowManager.zig b/src/WindowManager.zig
index 1211aa6..cb64fc5 100644
--- a/src/WindowManager.zig
+++ b/src/WindowManager.zig
@@ -72,7 +72,63 @@ pub fn prevOutput(wm: *WindowManager, current: *Output) ?*Output {
     return @fieldParentPtr("link", prev_link);
 }
 
-fn manage_start(wm: *WindowManager) void {
+fn initialize(wm: *WindowManager) void {
+    if (wm.context.initialized) return;
+
+    // We need a seat to intitialize this stuff, so let's just not do it right now.
+    // The WM can run fine without it, though, it won't be fully usuable.
+    const seat = wm.seats.first() orelse return;
+    const river_seat_v1 = seat.river_seat_v1;
+
+    const context = wm.context;
+    context.initialized = true;
+
+    // Tag bindings
+    for (context.config.tag_binds.items) |tag_bind| {
+        comptime var i: u8 = 1;
+        comptime var buffer: [1]u8 = undefined;
+        inline while (i <= 9) : (i += 1) {
+            const tags: u32 = 1 << (i - 1);
+            buffer[0] = i + '0';
+            const command: XkbBindings.Command = switch (tag_bind.command) {
+                .set_output_tags => .{ .set_output_tags = tags },
+                .set_window_tags => .{ .set_window_tags = tags },
+                .toggle_output_tags => .{ .toggle_output_tags = tags },
+                .toggle_window_tags => .{ .toggle_window_tags = tags },
+                else => unreachable,
+            };
+            context.xkb_bindings.addBinding(river_seat_v1, @field(xkbcommon.Keysym, &buffer), tag_bind.modifiers, command);
+        }
+    }
+    // Rest of the keybinds
+    for (context.config.keybinds.keys(), context.config.keybinds.values()) |key, command| {
+        context.xkb_bindings.addBinding(river_seat_v1, key.keysym, key.modifiers, command);
+    }
+
+    // Pointer bindings
+    for (context.config.pointer_binds.items) |pointer_bind| {
+        const binding = river_seat_v1.getPointerBinding(pointer_bind.button, pointer_bind.modifiers) catch {
+            log.err("Failed to create pointer binding", .{});
+            continue;
+        };
+
+        switch (pointer_bind.action) {
+            .move_window => {
+                if (seat.move_pointer_binding) |old| old.destroy();
+                binding.setListener(*Seat, Seat.movePointerBindingListener, seat);
+                seat.move_pointer_binding = binding;
+            },
+            .resize_window => {
+                if (seat.resize_pointer_binding) |old| old.destroy();
+                binding.setListener(*Seat, Seat.resizePointerBindingListener, seat);
+                seat.resize_pointer_binding = binding;
+            },
+        }
+        binding.enable();
+    }
+}
+
+fn manage(wm: *WindowManager) void {
     const river_window_manager_v1 = wm.river_window_manager_v1;
     const context = wm.context;
 
@@ -82,54 +138,7 @@ fn manage_start(wm: *WindowManager) void {
     if (!context.initialized) {
         // This code runs during initial startup and after config reloads.
         @branchHint(.cold);
-        context.initialized = true;
-
-        const seat = wm.seats.first() orelse @panic("Failed to get seat");
-        const river_seat_v1 = seat.river_seat_v1;
-
-        // Tag bindings
-        for (context.config.tag_binds.items) |tag_bind| {
-            comptime var i: u8 = 1;
-            comptime var buffer: [1]u8 = undefined;
-            inline while (i <= 9) : (i += 1) {
-                const tags: u32 = 1 << (i - 1);
-                buffer[0] = i + '0';
-                const command: XkbBindings.Command = switch (tag_bind.command) {
-                    .set_output_tags => .{ .set_output_tags = tags },
-                    .set_window_tags => .{ .set_window_tags = tags },
-                    .toggle_output_tags => .{ .toggle_output_tags = tags },
-                    .toggle_window_tags => .{ .toggle_window_tags = tags },
-                    else => unreachable,
-                };
-                context.xkb_bindings.addBinding(river_seat_v1, @field(xkbcommon.Keysym, &buffer), tag_bind.modifiers, command);
-            }
-        }
-        // Rest of the keybinds
-        for (context.config.keybinds.keys(), context.config.keybinds.values()) |key, command| {
-            context.xkb_bindings.addBinding(river_seat_v1, key.keysym, key.modifiers, command);
-        }
-
-        // Pointer bindings
-        for (context.config.pointer_binds.items) |pointer_bind| {
-            const binding = river_seat_v1.getPointerBinding(pointer_bind.button, pointer_bind.modifiers) catch {
-                log.err("Failed to create pointer binding", .{});
-                continue;
-            };
-
-            switch (pointer_bind.action) {
-                .move_window => {
-                    if (seat.move_pointer_binding) |old| old.destroy();
-                    binding.setListener(*Seat, Seat.movePointerBindingListener, seat);
-                    seat.move_pointer_binding = binding;
-                },
-                .resize_window => {
-                    if (seat.resize_pointer_binding) |old| old.destroy();
-                    binding.setListener(*Seat, Seat.resizePointerBindingListener, seat);
-                    seat.resize_pointer_binding = binding;
-                },
-            }
-            binding.enable();
-        }
+        wm.initialize();
     }
 
     {
@@ -147,7 +156,7 @@ fn manage_start(wm: *WindowManager) void {
     river_window_manager_v1.manageFinish();
 }
 
-fn render_start(wm: *WindowManager) void {
+fn render(wm: *WindowManager) void {
     const river_window_manager_v1 = wm.river_window_manager_v1;
     {
         var it = wm.seats.iterator(.forward);
@@ -171,8 +180,8 @@ fn windowManagerV1Listener(window_manager_v1: *river.WindowManagerV1, event: riv
         .unavailable => {
             fatal("Window manager unavailable (some other wm instance is running). Exiting", .{});
         },
-        .manage_start => wm.manage_start(),
-        .render_start => wm.render_start(),
+        .manage_start => wm.manage(),
+        .render_start => wm.render(),
         .output => |ev| {
             const output = Output.create(context, ev.id) catch @panic("Out of memory");
             wm.outputs.append(output);
@@ -212,12 +221,32 @@ fn windowManagerV1Listener(window_manager_v1: *river.WindowManagerV1, event: riv
             // If there was already an output, but no seats, set the first output as focused
             if (wm.outputs.first()) |output| {
                 seat.pending_manage.output = .{ .output = output };
+
+                // Adopt any orphan windows that arrived before we had a seat
+                var it = wm.orphan_windows.iterator(.forward);
+                while (it.next()) |window| {
+                    window.pending_manage.pending_output = .{ .output = output };
+                }
+                if (wm.orphan_windows.first()) |first| {
+                    seat.pending_manage.window = .{ .window = first };
+                    seat.pending_manage.should_warp_pointer = true;
+                }
+                output.windows.appendList(&wm.orphan_windows);
             }
         },
         .window => |ev| {
             // TODO: Support multiple seats
-            const seat = wm.seats.first() orelse @panic("Failed to get seat");
-            const focused_output = seat.focused_output;
+            const seat = wm.seats.first();
+            const focused_output = if (seat) |s|
+                s.focused_output orelse if (s.pending_manage.output) |pending_output|
+                    switch (pending_output) {
+                        .output => |output| output,
+                        .clear_focus => null,
+                    }
+                else
+                    wm.outputs.first()
+            else
+                wm.outputs.first();
             const window_list = if (focused_output) |output|
                 &output.windows
             else
@@ -228,8 +257,10 @@ fn windowManagerV1Listener(window_manager_v1: *river.WindowManagerV1, event: riv
                 .top => window_list.prepend(window),
                 .bottom => window_list.append(window),
             }
-            seat.pending_manage.window = .{ .window = window };
-            seat.pending_manage.should_warp_pointer = true;
+            if (seat) |s| {
+                s.pending_manage.window = .{ .window = window };
+                s.pending_manage.should_warp_pointer = true;
+            }
         },
         else => |ev| {
             log.debug("unhandled event: {s}", .{@tagName(ev)});
diff --git a/src/config/helpers.zig b/src/config/helpers.zig
index bbfeecf..ffc5643 100644
--- a/src/config/helpers.zig
+++ b/src/config/helpers.zig
@@ -7,7 +7,7 @@
 /// if arg_str in ["#true", "true"], return true
 /// if arg_str in ["#false", "false"], return false
 /// else, return null
-pub fn boolFromKdlStr(arg_str: []const u8) ?bool {
+pub fn boolFromKdlStr(arg_str: []const u8) !bool {
     if (mem.eql(u8, arg_str, "#true") or
         mem.eql(u8, arg_str, "true"))
     {
@@ -17,7 +17,7 @@ pub fn boolFromKdlStr(arg_str: []const u8) ?bool {
     {
         return false;
     }
-    return null;
+    return error.NotABool;
 }
 
 pub fn parseButton(s: []const u8) ?u32 {
@@ -96,16 +96,16 @@ const testing = std.testing;
 
 test "boolFromKdlStr" {
     // True valid
-    try testing.expectEqual(@as(?bool, true), boolFromKdlStr("#true"));
-    try testing.expectEqual(@as(?bool, true), boolFromKdlStr("true"));
+    try testing.expectEqual(true, try boolFromKdlStr("#true"));
+    try testing.expectEqual(true, try boolFromKdlStr("true"));
     // False valid
-    try testing.expectEqual(@as(?bool, false), boolFromKdlStr("#false"));
-    try testing.expectEqual(@as(?bool, false), boolFromKdlStr("false"));
+    try testing.expectEqual(false, try boolFromKdlStr("#false"));
+    try testing.expectEqual(false, try boolFromKdlStr("false"));
     // Invalid
-    try testing.expectEqual(@as(?bool, null), boolFromKdlStr("yes"));
-    try testing.expectEqual(@as(?bool, null), boolFromKdlStr("1"));
-    try testing.expectEqual(@as(?bool, null), boolFromKdlStr(""));
-    try testing.expectEqual(@as(?bool, null), boolFromKdlStr("TRUE"));
+    try testing.expectError(error.NotABool, boolFromKdlStr("yes"));
+    try testing.expectError(error.NotABool, boolFromKdlStr("1"));
+    try testing.expectError(error.NotABool, boolFromKdlStr(""));
+    try testing.expectError(error.NotABool, boolFromKdlStr("TRUE"));
 }
 
 test "parseButton named buttons" {
diff --git a/src/config/window_rule.zig b/src/config/window_rule.zig
new file mode 100644
index 0000000..dcdddc4
--- /dev/null
+++ b/src/config/window_rule.zig
@@ -0,0 +1,104 @@
+// SPDX-FileCopyrightText: 2026 Ben Buhse <me@benbuhse.email>
+//
+// SPDX-License-Identifier: GPL-3.0-only
+
+const NodeName = enum {
+    float,
+    no_float,
+    tags,
+    // TODO: Add more of riverctl's rule options such as ssd/csd
+};
+
+pub const Rule = struct {
+    // if app_id/title are null, they match all values
+    app_id_glob: ?[]const u8 = null,
+    title_glob: ?[]const u8 = null,
+    action: Action,
+};
+
+pub const Action = union(enum) {
+    float: bool,
+    tags: u32,
+};
+
+pub fn load(config: *Config, parser: *kdl.Parser, hostname: ?[]const u8) !void {
+    while (try parser.next()) |event| {
+        switch (event) {
+            .node => |node| {
+                const node_name = std.meta.stringToEnum(NodeName, node.name);
+                if (node_name) |name| {
+                    if (!helpers.hostMatches(node, parser, hostname)) {
+                        log.debug("Skipping \"window_rule.{s}\" (host mismatch)", .{@tagName(name)});
+                        continue;
+                    }
+
+                    const app_id_glob = if (node.prop(parser, "app_id")) |raw_app_id| blk: {
+                        const app_id = utils.stripQuotes(raw_app_id);
+                        globber.validate(app_id) catch {
+                            log.warn("Invalid glob for app_id \"{s}\"", .{app_id});
+                            continue;
+                        };
+                        break :blk try utils.gpa.dupe(u8, app_id);
+                    } else null;
+                    errdefer if (app_id_glob) |app_id| utils.gpa.free(app_id);
+                    const title_glob = if (node.prop(parser, "title")) |raw_title| blk: {
+                        const title = utils.stripQuotes(raw_title);
+                        globber.validate(title) catch {
+                            log.warn("Invalid glob for title \"{s}\"", .{title});
+                            continue;
+                        };
+                        break :blk try utils.gpa.dupe(u8, title);
+                    } else null;
+                    errdefer if (title_glob) |title| utils.gpa.free(title);
+
+                    const action: Action = sw: switch (name) {
+                        .float => .{ .float = true },
+                        .no_float => .{ .float = false },
+                        .tags => {
+                            const tags_str = utils.stripQuotes(node.arg(parser, 0) orelse "");
+                            const tags = fmt.parseInt(u32, tags_str, 0) catch {
+                                logWarnInvalidNodeArg(name, tags_str);
+                                continue;
+                            };
+                            break :sw .{ .tags = tags };
+                        },
+                    };
+                    try config.window_rules.append(utils.gpa, .{
+                        .app_id_glob = app_id_glob,
+                        .title_glob = title_glob,
+                        .action = action,
+                    });
+                } else {
+                    helpers.logWarnInvalidNode(node.name);
+                }
+            },
+            .child_block_begin => {
+                // window_rules should never have a nested child block
+                try helpers.skipChildBlock(parser);
+            },
+            .child_block_end => {
+                // Done parsing the window_rules block; return
+                return;
+            },
+        }
+    }
+}
+
+inline fn logWarnInvalidNodeArg(node_name: NodeName, node_value: []const u8) void {
+    log.warn("Invalid \"window_rule.{s}\" ({s}). Ignoring", .{ @tagName(node_name), node_value });
+}
+
+const std = @import("std");
+const fmt = std.fmt;
+const mem = std.mem;
+
+const kdl = @import("kdl");
+
+const globber = @import("../globber.zig");
+const utils = @import("../utils.zig");
+const Config = @import("../Config.zig");
+const XkbBindings = @import("../XkbBindings.zig");
+
+const helpers = @import("helpers.zig");
+
+const log = std.log.scoped(.config_window_rule);
diff --git a/src/globber.zig b/src/globber.zig
new file mode 100644
index 0000000..9b273e6
--- /dev/null
+++ b/src/globber.zig
@@ -0,0 +1,211 @@
+// Copyright 2023 Isaac Freund
+// SPDX-FileCopyrightText: 2023 Isaac Freund
+//
+// SPDX-License-Identifier: 0BSD
+
+const std = @import("std");
+const mem = std.mem;
+
+/// Validate a glob, returning error.InvalidGlob if it is empty, "**" or has a
+/// '*' at any position other than the first and/or last byte.
+pub fn validate(glob: []const u8) error{InvalidGlob}!void {
+    switch (glob.len) {
+        0 => return error.InvalidGlob,
+        1 => {},
+        2 => if (glob[0] == '*' and glob[1] == '*') return error.InvalidGlob,
+        else => if (mem.indexOfScalar(u8, glob[1 .. glob.len - 1], '*') != null) {
+            return error.InvalidGlob;
+        },
+    }
+}
+
+test validate {
+    const testing = std.testing;
+
+    try validate("*");
+    try validate("a");
+    try validate("*a");
+    try validate("a*");
+    try validate("*a*");
+    try validate("ab");
+    try validate("*ab");
+    try validate("ab*");
+    try validate("*ab*");
+    try validate("abc");
+    try validate("*abc");
+    try validate("abc*");
+    try validate("*abc*");
+
+    try testing.expectError(error.InvalidGlob, validate(""));
+    try testing.expectError(error.InvalidGlob, validate("**"));
+    try testing.expectError(error.InvalidGlob, validate("***"));
+    try testing.expectError(error.InvalidGlob, validate("a*c"));
+    try testing.expectError(error.InvalidGlob, validate("ab*c*"));
+    try testing.expectError(error.InvalidGlob, validate("*ab*c"));
+    try testing.expectError(error.InvalidGlob, validate("ab*c"));
+    try testing.expectError(error.InvalidGlob, validate("a*bc*"));
+    try testing.expectError(error.InvalidGlob, validate("**a"));
+    try testing.expectError(error.InvalidGlob, validate("abc**"));
+}
+
+/// Return true if s is matched by glob.
+/// Asserts that the glob is valid, see `validate()`.
+pub fn match(s: []const u8, glob: []const u8) bool {
+    if (std.debug.runtime_safety) {
+        validate(glob) catch unreachable;
+    }
+
+    if (glob.len == 1) {
+        return glob[0] == '*' or mem.eql(u8, s, glob);
+    }
+
+    const suffix_match = glob[0] == '*';
+    const prefix_match = glob[glob.len - 1] == '*';
+
+    if (suffix_match and prefix_match) {
+        return mem.indexOf(u8, s, glob[1 .. glob.len - 1]) != null;
+    } else if (suffix_match) {
+        return mem.endsWith(u8, s, glob[1..]);
+    } else if (prefix_match) {
+        return mem.startsWith(u8, s, glob[0 .. glob.len - 1]);
+    } else {
+        return mem.eql(u8, s, glob);
+    }
+}
+
+test match {
+    const testing = std.testing;
+
+    try testing.expect(match("", "*"));
+
+    try testing.expect(match("a", "*"));
+    try testing.expect(match("a", "*a*"));
+    try testing.expect(match("a", "a*"));
+    try testing.expect(match("a", "*a"));
+    try testing.expect(match("a", "a"));
+
+    try testing.expect(!match("a", "b"));
+    try testing.expect(!match("a", "*b*"));
+    try testing.expect(!match("a", "b*"));
+    try testing.expect(!match("a", "*b"));
+
+    try testing.expect(match("ab", "*"));
+    try testing.expect(match("ab", "*a*"));
+    try testing.expect(match("ab", "*b*"));
+    try testing.expect(match("ab", "a*"));
+    try testing.expect(match("ab", "*b"));
+    try testing.expect(match("ab", "*ab*"));
+    try testing.expect(match("ab", "ab*"));
+    try testing.expect(match("ab", "*ab"));
+    try testing.expect(match("ab", "ab"));
+
+    try testing.expect(!match("ab", "b*"));
+    try testing.expect(!match("ab", "*a"));
+    try testing.expect(!match("ab", "*c*"));
+    try testing.expect(!match("ab", "c*"));
+    try testing.expect(!match("ab", "*c"));
+    try testing.expect(!match("ab", "ac"));
+    try testing.expect(!match("ab", "*ac*"));
+    try testing.expect(!match("ab", "ac*"));
+    try testing.expect(!match("ab", "*ac"));
+
+    try testing.expect(match("abc", "*"));
+    try testing.expect(match("abc", "*a*"));
+    try testing.expect(match("abc", "*b*"));
+    try testing.expect(match("abc", "*c*"));
+    try testing.expect(match("abc", "a*"));
+    try testing.expect(match("abc", "*c"));
+    try testing.expect(match("abc", "*ab*"));
+    try testing.expect(match("abc", "ab*"));
+    try testing.expect(match("abc", "*bc*"));
+    try testing.expect(match("abc", "*bc"));
+    try testing.expect(match("abc", "*abc*"));
+    try testing.expect(match("abc", "abc*"));
+    try testing.expect(match("abc", "*abc"));
+    try testing.expect(match("abc", "abc"));
+
+    try testing.expect(!match("abc", "*a"));
+    try testing.expect(!match("abc", "*b"));
+    try testing.expect(!match("abc", "b*"));
+    try testing.expect(!match("abc", "c*"));
+    try testing.expect(!match("abc", "*ab"));
+    try testing.expect(!match("abc", "bc*"));
+    try testing.expect(!match("abc", "*d*"));
+    try testing.expect(!match("abc", "d*"));
+    try testing.expect(!match("abc", "*d"));
+}
+
+/// Returns .lt if a is less general than b.
+/// Returns .gt if a is more general than b.
+/// Returns .eq if a and b are equally general.
+/// Both a and b must be valid globs, see `validate()`.
+pub fn order(a: []const u8, b: []const u8) std.math.Order {
+    if (std.debug.runtime_safety) {
+        validate(a) catch unreachable;
+        validate(b) catch unreachable;
+    }
+
+    if (mem.eql(u8, a, "*") and mem.eql(u8, b, "*")) {
+        return .eq;
+    } else if (mem.eql(u8, a, "*")) {
+        return .gt;
+    } else if (mem.eql(u8, b, "*")) {
+        return .lt;
+    }
+
+    const count_a = @as(u2, @intFromBool(a[0] == '*')) + @intFromBool(a[a.len - 1] == '*');
+    const count_b = @as(u2, @intFromBool(b[0] == '*')) + @intFromBool(b[b.len - 1] == '*');
+
+    if (count_a == 0 and count_b == 0) {
+        return .eq;
+    } else if (count_a == count_b) {
+        // This may look backwards since e.g. "c*" is more general than "cc*"
+        return std.math.order(b.len, a.len);
+    } else {
+        return std.math.order(count_a, count_b);
+    }
+}
+
+test order {
+    const testing = std.testing;
+    const Order = std.math.Order;
+
+    try testing.expectEqual(Order.eq, order("*", "*"));
+    try testing.expectEqual(Order.eq, order("*a*", "*b*"));
+    try testing.expectEqual(Order.eq, order("a*", "*b"));
+    try testing.expectEqual(Order.eq, order("*a", "*b"));
+    try testing.expectEqual(Order.eq, order("*a", "b*"));
+    try testing.expectEqual(Order.eq, order("a*", "b*"));
+
+    const descending = [_][]const u8{
+        "*",
+        "*a*",
+        "*b*",
+        "*a*",
+        "*ab*",
+        "*bab*",
+        "*a",
+        "b*",
+        "*b",
+        "*a",
+        "a",
+        "bababab",
+        "b",
+        "a",
+    };
+
+    for (descending, 0..) |a, i| {
+        for (descending[i..]) |b| {
+            try testing.expect(order(a, b) != .lt);
+        }
+    }
+
+    var ascending = descending;
+    mem.reverse([]const u8, &ascending);
+
+    for (ascending, 0..) |a, i| {
+        for (ascending[i..]) |b| {
+            try testing.expect(order(a, b) != .gt);
+        }
+    }
+}
diff --git a/src/main.zig b/src/main.zig
index 72db61e..62f898b 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -357,4 +357,5 @@ const log = std.log.scoped(.main);
 test {
     _ = @import("utils.zig");
     _ = @import("Config.zig");
+    _ = @import("globber.zig");
 }