diff --git a/src/layout.zig b/src/layout.zig
new file mode 100644
index 0000000..51722bd
--- /dev/null
+++ b/src/layout.zig
@@ -0,0 +1,365 @@
+const std = @import("std");
+const input = @import("input.zig");
+
+// Source-patched keyboard layout facts, intentionally separate from commands.
+// req: input/004, input/005, governance/001, testing/001, testing/002, testing/003, testing/004
+
+test {
+    _ = ios_qwertz;
+}
+
+pub const ProfileId = enum {
+    ios_qwertz,
+};
+
+pub const Kind = enum {
+    letter,
+    whitespace,
+    control,
+    punctuation,
+    unknown,
+};
+
+pub const Fact = struct {
+    raw: []const u8,
+    kind: Kind,
+};
+
+pub const Profile = struct {
+    id: ProfileId,
+    name: []const u8,
+    facts: []const Fact,
+};
+
+pub const Classified = struct {
+    event: input.Event,
+    kind: Kind,
+};
+
+pub const TraceResult = union(enum) {
+    ok,
+    diverged: Divergence,
+
+    pub fn deinit(self: TraceResult, allocator: std.mem.Allocator) void {
+        switch (self) {
+            .ok => {},
+            .diverged => |diverged| allocator.free(diverged.message),
+        }
+    }
+};
+
+pub const Divergence = struct {
+    step: usize,
+    message: []const u8,
+};
+
+pub const LayoutTraceRecorder = struct {
+    allocator: std.mem.Allocator,
+    profile: *const Profile,
+    lines: std.ArrayList(u8) = .empty,
+
+    pub fn init(allocator: std.mem.Allocator, profile: *const Profile) LayoutTraceRecorder {
+        return .{ .allocator = allocator, .profile = profile };
+    }
+
+    pub fn deinit(self: *LayoutTraceRecorder) void {
+        self.lines.deinit(self.allocator);
+        self.* = undefined;
+    }
+
+    pub fn capture(self: *LayoutTraceRecorder, raw: []const u8) !void {
+        const label = try classificationLabelAlloc(self.allocator, classifyRaw(self.profile, raw));
+        defer self.allocator.free(label);
+        try appendHex(self.allocator, &self.lines, raw);
+        try self.lines.appendSlice(self.allocator, " => ");
+        try self.lines.appendSlice(self.allocator, @tagName(self.profile.id));
+        try self.lines.append(self.allocator, ':');
+        try self.lines.appendSlice(self.allocator, label);
+        try self.lines.append(self.allocator, '\n');
+    }
+
+    pub fn text(self: *const LayoutTraceRecorder) []const u8 {
+        return self.lines.items;
+    }
+};
+
+pub const ios_qwertz = Profile{
+    .id = .ios_qwertz,
+    .name = "iOS QWERTZ",
+    .facts = &ios_qwertz_facts,
+};
+
+const ios_qwertz_facts = [_]Fact{
+    .{ .raw = "a", .kind = .letter },
+    .{ .raw = "b", .kind = .letter },
+    .{ .raw = "c", .kind = .letter },
+    .{ .raw = "d", .kind = .letter },
+    .{ .raw = "e", .kind = .letter },
+    .{ .raw = "f", .kind = .letter },
+    .{ .raw = "g", .kind = .letter },
+    .{ .raw = "h", .kind = .letter },
+    .{ .raw = "i", .kind = .letter },
+    .{ .raw = "j", .kind = .letter },
+    .{ .raw = "k", .kind = .letter },
+    .{ .raw = "l", .kind = .letter },
+    .{ .raw = "m", .kind = .letter },
+    .{ .raw = "n", .kind = .letter },
+    .{ .raw = "o", .kind = .letter },
+    .{ .raw = "p", .kind = .letter },
+    .{ .raw = "q", .kind = .letter },
+    .{ .raw = "r", .kind = .letter },
+    .{ .raw = "s", .kind = .letter },
+    .{ .raw = "t", .kind = .letter },
+    .{ .raw = "u", .kind = .letter },
+    .{ .raw = "v", .kind = .letter },
+    .{ .raw = "w", .kind = .letter },
+    .{ .raw = "x", .kind = .letter },
+    .{ .raw = "y", .kind = .letter },
+    .{ .raw = "z", .kind = .letter },
+    .{ .raw = "ä", .kind = .letter },
+    .{ .raw = "ö", .kind = .letter },
+    .{ .raw = "ü", .kind = .letter },
+    .{ .raw = "ß", .kind = .letter },
+
+    .{ .raw = ".", .kind = .punctuation },
+    .{ .raw = ",", .kind = .punctuation },
+    .{ .raw = ":", .kind = .punctuation },
+    .{ .raw = ";", .kind = .punctuation },
+    .{ .raw = "-", .kind = .punctuation },
+    .{ .raw = "_", .kind = .punctuation },
+    .{ .raw = "/", .kind = .punctuation },
+    .{ .raw = "\\", .kind = .punctuation },
+    .{ .raw = "'", .kind = .punctuation },
+    .{ .raw = "\"", .kind = .punctuation },
+    .{ .raw = "`", .kind = .punctuation },
+    .{ .raw = "~", .kind = .punctuation },
+    .{ .raw = "(", .kind = .punctuation },
+    .{ .raw = ")", .kind = .punctuation },
+    .{ .raw = "[", .kind = .punctuation },
+    .{ .raw = "]", .kind = .punctuation },
+    .{ .raw = "{", .kind = .punctuation },
+    .{ .raw = "}", .kind = .punctuation },
+    .{ .raw = "<", .kind = .punctuation },
+    .{ .raw = ">", .kind = .punctuation },
+    .{ .raw = "=", .kind = .punctuation },
+    .{ .raw = "+", .kind = .punctuation },
+    .{ .raw = "*", .kind = .punctuation },
+    .{ .raw = "!", .kind = .punctuation },
+    .{ .raw = "?", .kind = .punctuation },
+    .{ .raw = "@", .kind = .punctuation },
+    .{ .raw = "#", .kind = .punctuation },
+    .{ .raw = "$", .kind = .punctuation },
+    .{ .raw = "%", .kind = .punctuation },
+    .{ .raw = "&", .kind = .punctuation },
+    .{ .raw = "|", .kind = .punctuation },
+};
+
+pub fn classifyRaw(profile: *const Profile, raw: []const u8) Classified {
+    return classifyEvent(profile, input.normalize(raw));
+}
+
+pub fn classifyEvent(profile: *const Profile, event: input.Event) Classified {
+    const kind: Kind = switch (event) {
+        .key => |key| switch (key) {
+            .space, .tab => .whitespace,
+            .enter, .backspace, .escape, .arrow_left, .arrow_right, .arrow_up, .arrow_down => .control,
+        },
+        .text => |text| lookupFact(profile, text) orelse .unknown,
+        .unknown => .unknown,
+    };
+    return .{ .event = event, .kind = kind };
+}
+
+pub fn replayLayoutTrace(allocator: std.mem.Allocator, profile: *const Profile, trace: []const u8) !TraceResult {
+    var step: usize = 0;
+    var lines = std.mem.splitScalar(u8, trace, '\n');
+    while (lines.next()) |line| {
+        if (line.len == 0) continue;
+        step += 1;
+        const separator = std.mem.indexOf(u8, line, " => ") orelse return divergence(allocator, step, "layout trace line is missing separator");
+        const raw_hex = line[0..separator];
+        const expected = line[separator + 4 ..];
+        var raw = std.ArrayList(u8).empty;
+        defer raw.deinit(allocator);
+        parseHexInto(allocator, &raw, raw_hex) catch |err| switch (err) {
+            error.InvalidHex => return divergence(allocator, step, "layout trace line has invalid hex bytes"),
+            else => return err,
+        };
+        const actual = try classificationLabelWithProfileAlloc(allocator, profile, classifyRaw(profile, raw.items));
+        defer allocator.free(actual);
+        if (!std.mem.eql(u8, expected, actual)) {
+            return divergenceFmt(allocator, step, "expected layout event '{s}' but got '{s}'", .{ expected, actual });
+        }
+    }
+    return .ok;
+}
+
+fn lookupFact(profile: *const Profile, text: []const u8) ?Kind {
+    for (profile.facts) |fact| {
+        if (std.mem.eql(u8, text, fact.raw)) return fact.kind;
+    }
+    return null;
+}
+
+fn classificationLabelWithProfileAlloc(allocator: std.mem.Allocator, profile: *const Profile, classified: Classified) ![]u8 {
+    const label = try classificationLabelAlloc(allocator, classified);
+    defer allocator.free(label);
+    return std.fmt.allocPrint(allocator, "{s}:{s}", .{ @tagName(profile.id), label });
+}
+
+fn classificationLabelAlloc(allocator: std.mem.Allocator, classified: Classified) ![]u8 {
+    return switch (classified.event) {
+        .key => |key| std.fmt.allocPrint(allocator, "{s}:key:{s}", .{ @tagName(classified.kind), @tagName(key) }),
+        .text => |text| std.fmt.allocPrint(allocator, "{s}:text:{s}", .{ @tagName(classified.kind), text }),
+        .unknown => |raw| unknownLabelAlloc(allocator, raw),
+    };
+}
+
+fn unknownLabelAlloc(allocator: std.mem.Allocator, raw: []const u8) ![]u8 {
+    var out = std.ArrayList(u8).empty;
+    errdefer out.deinit(allocator);
+    try out.appendSlice(allocator, "unknown:raw:");
+    try appendHex(allocator, &out, raw);
+    return out.toOwnedSlice(allocator);
+}
+
+fn appendHex(allocator: std.mem.Allocator, out: *std.ArrayList(u8), bytes: []const u8) !void {
+    const alphabet = "0123456789abcdef";
+    for (bytes) |byte| {
+        try out.append(allocator, alphabet[byte >> 4]);
+        try out.append(allocator, alphabet[byte & 0x0f]);
+    }
+}
+
+fn parseHexInto(allocator: std.mem.Allocator, out: *std.ArrayList(u8), hex: []const u8) !void {
+    if (hex.len % 2 != 0) return error.InvalidHex;
+    var i: usize = 0;
+    while (i < hex.len) : (i += 2) {
+        const high = hexNibble(hex[i]) orelse return error.InvalidHex;
+        const low = hexNibble(hex[i + 1]) orelse return error.InvalidHex;
+        try out.append(allocator, (high << 4) | low);
+    }
+}
+
+fn hexNibble(byte: u8) ?u8 {
+    return switch (byte) {
+        '0'...'9' => byte - '0',
+        'a'...'f' => byte - 'a' + 10,
+        'A'...'F' => byte - 'A' + 10,
+        else => null,
+    };
+}
+
+fn divergence(allocator: std.mem.Allocator, step: usize, message: []const u8) !TraceResult {
+    return .{ .diverged = .{ .step = step, .message = try allocator.dupe(u8, message) } };
+}
+
+fn divergenceFmt(allocator: std.mem.Allocator, step: usize, comptime fmt: []const u8, args: anytype) !TraceResult {
+    return .{ .diverged = .{ .step = step, .message = try std.fmt.allocPrint(allocator, fmt, args) } };
+}
+
+fn expectKind(raw: []const u8, expected: Kind) !void {
+    try std.testing.expectEqual(expected, classifyRaw(&ios_qwertz, raw).kind);
+}
+
+fn expectReplayOk(result: TraceResult) !void {
+    switch (result) {
+        .ok => {},
+        .diverged => return error.ExpectedTraceOk,
+    }
+}
+
+test "regular: iOS QWERTZ classifies letters including QWERTZ y and z" {
+    try expectKind("a", .letter);
+    try expectKind("m", .letter);
+    try expectKind("z", .letter);
+    try expectKind("y", .letter);
+    try expectKind("ä", .letter);
+    try expectKind("ö", .letter);
+    try expectKind("ü", .letter);
+    try expectKind("ß", .letter);
+}
+
+test "regular: iOS QWERTZ classifies whitespace and editing controls without commands" {
+    try expectKind(" ", .whitespace);
+    try expectKind("\t", .whitespace);
+    try expectKind("\r", .control);
+    try expectKind("\x7f", .control);
+    try expectKind("\x1b[D", .control);
+}
+
+test "regular: iOS QWERTZ classifies key coding punctuation" {
+    inline for (.{ ".", ",", ":", ";", "-", "_", "/", "\\", "'", "\"", "`", "~", "(", ")", "[", "]", "{", "}", "<", ">", "=", "+", "*", "!", "?", "@", "#", "$", "%", "&", "|" }) |raw| {
+        try expectKind(raw, .punctuation);
+    }
+}
+
+test "regular: iOS QWERTZ layout trace records raw bytes and replays" {
+    var recorder = LayoutTraceRecorder.init(std.testing.allocator, &ios_qwertz);
+    defer recorder.deinit();
+
+    try recorder.capture("z");
+    try recorder.capture("y");
+    try recorder.capture(" ");
+    try recorder.capture("\r");
+    try recorder.capture("\x7f");
+    try recorder.capture("{");
+    try recorder.capture("|");
+
+    const result = try replayLayoutTrace(std.testing.allocator, &ios_qwertz, recorder.text());
+    defer result.deinit(std.testing.allocator);
+    try expectReplayOk(result);
+}
+
+test "regular: profile labels are facts, not editor command intents" {
+    var recorder = LayoutTraceRecorder.init(std.testing.allocator, &ios_qwertz);
+    defer recorder.deinit();
+    try recorder.capture(" ");
+
+    try std.testing.expectEqualStrings("20 => ios_qwertz:whitespace:key:space\n", recorder.text());
+    try std.testing.expect(std.mem.indexOf(u8, recorder.text(), "leader") == null);
+    try std.testing.expect(std.mem.indexOf(u8, recorder.text(), "save") == null);
+}
+
+test "adversarial: unknown printable text and unknown escapes stay unknown" {
+    try expectKind("🔥", .unknown);
+    try expectKind("\x1b[999~", .unknown);
+}
+
+test "adversarial: layout trace reports malformed lines and invalid hex" {
+    {
+        const result = try replayLayoutTrace(std.testing.allocator, &ios_qwertz, "7a ios_qwertz:letter:text:z\n");
+        defer result.deinit(std.testing.allocator);
+        switch (result) {
+            .diverged => |diverged| {
+                try std.testing.expectEqual(@as(usize, 1), diverged.step);
+                try std.testing.expectEqualStrings("layout trace line is missing separator", diverged.message);
+            },
+            .ok => return error.ExpectedTraceDivergence,
+        }
+    }
+
+    {
+        const result = try replayLayoutTrace(std.testing.allocator, &ios_qwertz, "zz => ios_qwertz:letter:text:z\n");
+        defer result.deinit(std.testing.allocator);
+        switch (result) {
+            .diverged => |diverged| {
+                try std.testing.expectEqual(@as(usize, 1), diverged.step);
+                try std.testing.expectEqualStrings("layout trace line has invalid hex bytes", diverged.message);
+            },
+            .ok => return error.ExpectedTraceDivergence,
+        }
+    }
+}
+
+test "adversarial: layout trace names first classification mismatch" {
+    const result = try replayLayoutTrace(std.testing.allocator, &ios_qwertz, "7a => ios_qwertz:punctuation:text:z\n");
+    defer result.deinit(std.testing.allocator);
+    switch (result) {
+        .diverged => |diverged| {
+            try std.testing.expectEqual(@as(usize, 1), diverged.step);
+            try std.testing.expect(std.mem.indexOf(u8, diverged.message, "expected layout event") != null);
+        },
+        .ok => return error.ExpectedTraceDivergence,
+    }
+}
diff --git a/src/main.zig b/src/main.zig
index f9aeb81..335ea3e 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,5 +1,6 @@
 const std = @import("std");
 const input = @import("input.zig");
+const layout = @import("layout.zig");
 const protocol = @import("protocol.zig");
 const replay = @import("replay.zig");
 const session = @import("session.zig");
@@ -118,6 +119,7 @@ fn collectRemainingArgs(allocator: std.mem.Allocator, args: *std.process.Args.It
 
 test {
     _ = input;
+    _ = layout;
     _ = protocol;
     _ = replay;
     _ = session;