From 5984d6f7326845312bf5c00f4d4ae181cd733c41 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 10:16:25 -0700
Subject: [PATCH 01/10] terminal: add isTextMime helper for plain text MIME
 type names

---
 src/terminal/clipboard.zig | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/terminal/clipboard.zig b/src/terminal/clipboard.zig
index 554ca984b..170aa0725 100644
--- a/src/terminal/clipboard.zig
+++ b/src/terminal/clipboard.zig
@@ -1,3 +1,5 @@
+const std = @import("std");
+
 /// The clipboard destination for a write.
 pub const Location = enum(c_int) {
     standard = 0,
@@ -6,6 +8,21 @@ pub const Location = enum(c_int) {
     _,
 };
 
+/// MIME types that name plain text across the platforms terminals run
+/// on. We accept the union everywhere since serving text under any of these
+/// names is harmless.
+pub fn isTextMime(mime: []const u8) bool {
+    const names: []const []const u8 = &.{
+        "text/plain",
+        "text/plain;charset=utf-8",
+        "UTF8_STRING",
+        "TEXT",
+        "STRING",
+    };
+    for (names) |n| if (std.mem.eql(u8, mime, n)) return true;
+    return false;
+}
+
 /// A single representation of clipboard data.
 ///
 /// The MIME type and data are borrowed and only valid for the duration of a
@@ -34,3 +51,11 @@ pub const WriteResult = enum(c_int) {
     io_error = 5,
     _,
 };
+
+test isTextMime {
+    const testing = std.testing;
+    try testing.expect(isTextMime("text/plain"));
+    try testing.expect(isTextMime("UTF8_STRING"));
+    try testing.expect(!isTextMime("image/png"));
+    try testing.expect(!isTextMime("."));
+}

From 25b1170d422f06146661eb1531c1b574d20f1771 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 10:43:06 -0700
Subject: [PATCH 02/10] terminal: add kitty clipboard protocol (OSC 5522)
 command parsing

---
 src/terminal/kitty/clipboard.zig         |  55 ++++
 src/terminal/kitty/clipboard_command.zig | 386 +++++++++++++++++++++++
 2 files changed, 441 insertions(+)
 create mode 100644 src/terminal/kitty/clipboard.zig
 create mode 100644 src/terminal/kitty/clipboard_command.zig

diff --git a/src/terminal/kitty/clipboard.zig b/src/terminal/kitty/clipboard.zig
new file mode 100644
index 000000000..ddc768c34
--- /dev/null
+++ b/src/terminal/kitty/clipboard.zig
@@ -0,0 +1,55 @@
+//! Kitty clipboard protocol (OSC 5522).
+//!
+//! This implements the protocol semantics on top of the raw OSC capture:
+//! src/terminal/osc/parsers/kitty_clipboard_protocol.zig:
+//!
+//! The behavior here is modeled on the kitty reference implementation
+//! (kitty/clipboard.py) rather than only the prose spec, since the two
+//! disagree in places. Notable reference behaviors we reproduce:
+//!
+//!   * Malformed metadata (any record without '=', including an empty
+//!     metadata section), an unknown or missing `type`, and invalid
+//!     base64 in `mime`, `name`, or `pw` all silently drop the request
+//!     with no response.
+//!   * `mime`, `name`, and `pw` metadata values are base64-encoded UTF-8;
+//!     everything else is verbatim. Unknown keys are ignored.
+//!   * `id` is sanitized by stripping characters outside [a-zA-Z0-9-_+.]
+//!     and truncating to 512 bytes, then echoed verbatim in every
+//!     response packet (omitted when empty).
+//!   * Write data chunks are decoded with a streaming base64 decoder that
+//!     persists across packets of the same MIME type; a '=' padding
+//!     mid-stream finishes the current group and resets the decoder, so
+//!     both per-chunk-padded and continuous unpadded streams work. A
+//!     chunk with invalid base64 is dropped (decoder reset) and the
+//!     transaction continues; it is not a protocol error.
+//!   * A `type=write` silently replaces any in-flight transaction. A
+//!     commit (`type=wdata` without a MIME type) with no in-flight
+//!     transaction is silently ignored.
+//!   * Oversized writes are truncated and still complete with DONE.
+//!   * Responses never send a payload section for an empty payload,
+//!     except the targets ('.') listing DATA packet which is always sent.
+//!
+//! I plan to open an upstream issue asking for clarification on these
+//! once I implement this.
+//!
+//! Specification: https://sw.kovidgoyal.net/kitty/clipboard/
+
+const oscpkg = @import("../osc.zig");
+const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
+const command = @import("clipboard_command.zig");
+
+pub const OSC = protocol.OSC;
+pub const Operation = protocol.Operation;
+pub const Status = protocol.Status;
+pub const Terminator = oscpkg.Terminator;
+
+pub const Metadata = command.Metadata;
+pub const Payload = command.Payload;
+pub const max_id_len = command.max_id_len;
+pub const max_pw_len = command.max_pw_len;
+pub const max_mime_len = command.max_mime_len;
+pub const max_name_len = command.max_name_len;
+
+test {
+    @import("std").testing.refAllDecls(@This());
+}
diff --git a/src/terminal/kitty/clipboard_command.zig b/src/terminal/kitty/clipboard_command.zig
new file mode 100644
index 000000000..5f7115d83
--- /dev/null
+++ b/src/terminal/kitty/clipboard_command.zig
@@ -0,0 +1,386 @@
+//! Kitty clipboard protocol (OSC 5522) request decoding.
+//!
+//! OSC 5522 format: `<OSC>5522;metadata;payload<ST>`
+//!
+//! Per the spec: "metadata is a colon separated list of key-value
+//! pairs and payload is base64 encoded data."
+//!
+//! This contains the logic for parsing this.
+
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+const simd = @import("../../simd/main.zig");
+const clipboard = @import("../clipboard.zig");
+const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
+
+const Operation = protocol.Operation;
+
+/// Maximum id length, nothing specified but this is the limit used
+/// in Kitty's source so we'll match it.
+pub const max_id_len = 512;
+
+/// Maximum decoded password length. Kitty has no limit. Passwords are
+/// UUID-sized in practice so anything longer simply never matches a
+/// stored grant anyway.
+pub const max_pw_len = 128;
+
+/// Maximum decoded MIME type length. Kitty has no limit but real MIME
+/// types are tiny; anything longer drops the packet.
+pub const max_mime_len = 256;
+
+/// Maximum decoded name length we bother validating. Longer names are
+/// treated as present without validation; only their presence matters.
+pub const max_name_len = 256;
+
+/// The decoded, validated metadata of one OSC 5522 sequence.
+///
+/// All slice values are allocated from the allocator given to parse and
+/// are sized to their contents. Callers are expected to pass an arena
+/// scoped to handling the packet. There is no deinit.
+pub const Metadata = struct {
+    op: Operation,
+
+    /// The clipboard this operation targets. Per the spec: "To read
+    /// from the primary selection instead of the clipboard, add the
+    /// key `loc=primary` to the metadata section." Any other value
+    /// means the clipboard, so only standard and primary are possible
+    /// here.
+    loc: clipboard.Location = .standard,
+
+    /// Sanitized id: invalid characters stripped, truncated to
+    /// max_id_len. Empty means no id.
+    id: []const u8 = "",
+
+    /// Decoded mime metadata value. Empty means absent; kitty treats an
+    /// empty mime the same as a missing one everywhere it matters (a
+    /// wdata packet with either commits the transaction).
+    mime: []const u8 = "",
+
+    /// Decoded password. Empty means absent. Per the spec:
+    /// "Specifying a password without a human friendly name is
+    /// equivalent to not specifying a password and the terminal must
+    /// treat the request as though it had no password."
+    pw: []const u8 = "",
+
+    /// True if a non-empty (valid) name was given. We don't retain the
+    /// name contents; it exists to opt into password grants.
+    has_name: bool = false,
+
+    /// Parse the metadata field. The raw value is expected to be exactly
+    /// the metadata (prefix and payload and separators stripped out).
+    ///
+    /// A null result means it was invalid but without any response.
+    /// Silently drop the OSC.
+    pub fn parse(
+        alloc: Allocator,
+        raw: []const u8,
+    ) Allocator.Error!?Metadata {
+        var op_raw: ?[]const u8 = null;
+        var result: Metadata = .{ .op = undefined };
+
+        // Note this loop visits every record even though an empty raw
+        // string yields a single empty record: that record has no '='
+        // and correctly drops the packet, matching kitty which requires
+        // at least a valid `type` record.
+        var it = std.mem.splitScalar(u8, raw, ':');
+        while (it.next()) |record| {
+            // Every record must be key=value. Any single invalid record
+            // is dropped, matching Kitty's behavior.
+            const eql_idx = std.mem.indexOfScalar(u8, record, '=') orelse return null;
+            const key = record[0..eql_idx];
+            const value = record[eql_idx + 1 ..];
+
+            if (std.mem.eql(u8, key, "type")) {
+                // Validated after the loop: a duplicate key's last
+                // occurrence wins. This isn't specified but its how Kitty
+                // works.
+                op_raw = value;
+            } else if (std.mem.eql(u8, key, "loc")) {
+                result.loc = if (std.mem.eql(u8, value, "primary"))
+                    .primary
+                else
+                    .standard;
+            } else if (std.mem.eql(u8, key, "id")) {
+                result.id = try sanitizeId(alloc, value);
+            } else if (std.mem.eql(u8, key, "mime")) {
+                result.mime = decodeValue(
+                    alloc,
+                    value,
+                    max_mime_len,
+                ) catch |err| switch (err) {
+                    error.OutOfMemory => return error.OutOfMemory,
+                    error.Overflow, error.Invalid => return null,
+                };
+            } else if (std.mem.eql(u8, key, "pw")) {
+                result.pw = decodeValue(
+                    alloc,
+                    value,
+                    max_pw_len,
+                ) catch |err| switch (err) {
+                    error.OutOfMemory => return error.OutOfMemory,
+                    // An over-long password behaves as if none was
+                    // given: it can never match a stored grant.
+                    error.Overflow => "",
+                    error.Invalid => return null,
+                };
+            } else if (std.mem.eql(u8, key, "name")) {
+                // We only need to know whether a (non-empty) name was
+                // given; the contents are decoded for validation only.
+                result.has_name = has_name: {
+                    const name = decodeValue(
+                        alloc,
+                        value,
+                        max_name_len,
+                    ) catch |err| switch (err) {
+                        error.OutOfMemory => return error.OutOfMemory,
+                        // Over-long names are accepted as present but
+                        // not validated further.
+                        error.Overflow => break :has_name true,
+                        error.Invalid => return null,
+                    };
+                    break :has_name name.len > 0;
+                };
+            }
+            // Unknown keys are ignored.
+        }
+
+        // A missing or unknown operation drops the request.
+        result.op = Operation.init(op_raw orelse return null) orelse return null;
+        return result;
+    }
+
+    /// Sanitize the ID according to the spec:
+    ///
+    /// Valid ids must include only characters from the set: [a-zA-Z0-9-_+.].
+    /// Any other characters must be stripped out from the id by the terminal
+    /// emulator before retransmitting it.
+    fn sanitizeId(alloc: Allocator, value: []const u8) Allocator.Error![]const u8 {
+        var list: std.ArrayListUnmanaged(u8) = .empty;
+        defer list.deinit(alloc);
+        for (value) |c| {
+            switch (c) {
+                'a'...'z', 'A'...'Z', '0'...'9', '-', '_', '+', '.' => {},
+                else => continue,
+            }
+            if (list.items.len >= max_id_len) break;
+            try list.append(alloc, c);
+        }
+        return try list.toOwnedSlice(alloc);
+    }
+
+    /// Base64-decode a metadata value. Per the spec these values "are
+    /// UTF-8 strings that are base64 encoded", so the decoded result
+    /// must be valid UTF-8.
+    fn decodeValue(alloc: Allocator, value: []const u8, max_len: usize) error{
+        OutOfMemory,
+        Overflow,
+        Invalid,
+    }![]const u8 {
+        const Encoder = std.base64.standard.Encoder;
+
+        // Avoid hostile large payloads.
+        if (value.len > Encoder.calcSize(max_len)) return error.Overflow;
+
+        // Decode
+        const buf = try alloc.alloc(u8, simd.base64.maxLen(value));
+        errdefer alloc.free(buf);
+        const decoded = simd.base64.decode(
+            value,
+            buf,
+        ) catch return error.Invalid;
+
+        // Must be valid UTF-8
+        if (!std.unicode.utf8ValidateSlice(decoded)) return error.Invalid;
+        if (decoded.len > max_len) return error.Overflow;
+        return decoded;
+    }
+};
+
+/// A decoded base64 payload of one OSC 5522 sequence, e.g. the MIME
+/// type list of a read request or the alias list of a walias packet.
+/// The data slice aliases the allocated buf.
+pub const Payload = struct {
+    buf: []u8,
+    data: []const u8,
+
+    /// Decode a base64 payload into freshly allocated memory. An
+    /// invalid payload means the sequence is dropped.
+    pub fn init(
+        alloc: Allocator,
+        payload: []const u8,
+    ) error{ OutOfMemory, Invalid }!Payload {
+        const buf = try alloc.alloc(u8, simd.base64.maxLen(payload));
+        errdefer alloc.free(buf);
+        const data = simd.base64.decode(
+            payload,
+            buf,
+        ) catch return error.Invalid;
+        return .{ .buf = buf, .data = data };
+    }
+
+    pub fn deinit(self: *const Payload, alloc: Allocator) void {
+        alloc.free(self.buf);
+    }
+
+    /// Iterate the whitespace-separated MIME types of the payload.
+    /// Matches Python str.split() used by kitty.
+    pub fn mimeIterator(self: *const Payload) std.mem.TokenIterator(u8, .any) {
+        return std.mem.tokenizeAny(
+            u8,
+            self.data,
+            &std.ascii.whitespace,
+        );
+    }
+};
+
+test "metadata: empty is dropped" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expect((try Metadata.parse(arena.allocator(), "")) == null);
+}
+
+test "metadata: record without = is dropped" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=read:bare")) == null);
+    try testing.expect((try Metadata.parse(arena.allocator(), "bare:type=read")) == null);
+}
+
+test "metadata: missing or unknown type is dropped" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expect((try Metadata.parse(arena.allocator(), "loc=primary")) == null);
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=bobr")) == null);
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=")) == null);
+}
+
+test "metadata: duplicate keys keep the last occurrence" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expectEqual(
+        Operation.read,
+        (try Metadata.parse(arena.allocator(), "type=bobr:type=read")).?.op,
+    );
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=read:type=bobr")) == null);
+}
+
+test "metadata: basic read" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    const meta = (try Metadata.parse(arena.allocator(), "type=read")).?;
+    try testing.expectEqual(Operation.read, meta.op);
+    try testing.expect(meta.loc == .standard);
+    try testing.expectEqual(@as(usize, 0), meta.id.len);
+}
+
+test "metadata: unknown keys ignored" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    const meta = (try Metadata.parse(arena.allocator(), "type=read:bobr=kurwa")).?;
+    try testing.expectEqual(Operation.read, meta.op);
+}
+
+test "metadata: loc" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=read:loc=primary")).?.loc == .primary);
+    // Anything other than "primary" means the clipboard; it is not an
+    // error.
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=read:loc=bobr")).?.loc == .standard);
+}
+
+test "metadata: id sanitized" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    {
+        const meta = (try Metadata.parse(arena.allocator(), "type=read:id=abc-123_x.Y+z")).?;
+        try testing.expectEqualStrings("abc-123_x.Y+z", meta.id);
+    }
+    {
+        // Invalid characters are stripped, not rejected.
+        const meta = (try Metadata.parse(arena.allocator(), "type=read:id=*4 2*")).?;
+        try testing.expectEqualStrings("42", meta.id);
+    }
+}
+
+test "metadata: id truncated to max" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    const raw = "type=read:id=" ++ "a" ** (max_id_len + 100);
+    const meta = (try Metadata.parse(arena.allocator(), raw)).?;
+    try testing.expectEqual(@as(usize, max_id_len), meta.id.len);
+}
+
+test "metadata: mime decoded" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    // "text/plain"
+    const meta = (try Metadata.parse(arena.allocator(), "type=wdata:mime=dGV4dC9wbGFpbg==")).?;
+    try testing.expectEqualStrings("text/plain", meta.mime);
+}
+
+test "metadata: invalid mime base64 dropped" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=wdata:mime=!!!")) == null);
+}
+
+test "metadata: invalid mime utf8 dropped" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    // base64 of 0xff 0xfe
+    try testing.expect((try Metadata.parse(arena.allocator(), "type=wdata:mime=//4=")) == null);
+}
+
+test "metadata: pw and name" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    // pw="secret", name="app"
+    const meta = (try Metadata.parse(arena.allocator(), "type=read:pw=c2VjcmV0:name=YXBw")).?;
+    try testing.expectEqualStrings("secret", meta.pw);
+    try testing.expect(meta.has_name);
+}
+
+test "metadata: empty name" {
+    const testing = std.testing;
+    var arena: std.heap.ArenaAllocator = .init(testing.allocator);
+    defer arena.deinit();
+    const meta = (try Metadata.parse(arena.allocator(), "type=read:pw=c2VjcmV0:name=")).?;
+    try testing.expect(!meta.has_name);
+}
+
+test "payload: mime iterator" {
+    const testing = std.testing;
+    // base64 of "text/plain  text/html\ntext/uri-list"
+    const payload = try Payload.init(
+        testing.allocator,
+        "dGV4dC9wbGFpbiAgdGV4dC9odG1sCnRleHQvdXJpLWxpc3Q=",
+    );
+    defer payload.deinit(testing.allocator);
+    var it = payload.mimeIterator();
+    try testing.expectEqualStrings("text/plain", it.next().?);
+    try testing.expectEqualStrings("text/html", it.next().?);
+    try testing.expectEqualStrings("text/uri-list", it.next().?);
+    try testing.expect(it.next() == null);
+}
+
+test "payload: invalid base64" {
+    const testing = std.testing;
+    try testing.expectError(
+        error.Invalid,
+        Payload.init(testing.allocator, "!!!"),
+    );
+}

From e28acd928c4c02e8a7d8999e55b4d118098ec423 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 11:34:30 -0700
Subject: [PATCH 03/10] terminal: add kitty clipboard protocol (OSC 5522)
 response encoding

---
 src/terminal/kitty/clipboard.zig          |   7 +
 src/terminal/kitty/clipboard_response.zig | 385 ++++++++++++++++++++++
 2 files changed, 392 insertions(+)
 create mode 100644 src/terminal/kitty/clipboard_response.zig

diff --git a/src/terminal/kitty/clipboard.zig b/src/terminal/kitty/clipboard.zig
index ddc768c34..7ef850bfe 100644
--- a/src/terminal/kitty/clipboard.zig
+++ b/src/terminal/kitty/clipboard.zig
@@ -37,6 +37,7 @@
 const oscpkg = @import("../osc.zig");
 const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
 const command = @import("clipboard_command.zig");
+const response = @import("clipboard_response.zig");
 
 pub const OSC = protocol.OSC;
 pub const Operation = protocol.Operation;
@@ -50,6 +51,12 @@ pub const max_pw_len = command.max_pw_len;
 pub const max_mime_len = command.max_mime_len;
 pub const max_name_len = command.max_name_len;
 
+pub const Response = response.Response;
+pub const ReadSuccess = response.ReadSuccess;
+pub const read_chunk_size = response.read_chunk_size;
+pub const max_read_mimes = response.max_read_mimes;
+pub const targets_mime = response.targets_mime;
+
 test {
     @import("std").testing.refAllDecls(@This());
 }
diff --git a/src/terminal/kitty/clipboard_response.zig b/src/terminal/kitty/clipboard_response.zig
new file mode 100644
index 000000000..c7f01c165
--- /dev/null
+++ b/src/terminal/kitty/clipboard_response.zig
@@ -0,0 +1,385 @@
+//! Kitty clipboard protocol (OSC 5522) response encoding.
+
+const std = @import("std");
+const clipboard = @import("../clipboard.zig");
+const oscpkg = @import("../osc.zig");
+const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
+
+const b64 = std.base64.standard.Encoder;
+const Content = clipboard.Content;
+const Operation = protocol.Operation;
+const Status = protocol.Status;
+const Terminator = oscpkg.Terminator;
+
+/// Maximum raw (pre-base64) bytes per DATA packet in read responses.
+/// This is specified by the protocol.
+pub const read_chunk_size = 4096;
+
+/// Maximum requested MIME types served by a single read request.
+/// Requests beyond this simply see no DATA packets for the extras,
+/// which is how the protocol communicates an unavailable type anyway.
+pub const max_read_mimes = 4;
+
+/// The special MIME type that requests the list of available types.
+pub const targets_mime = ".";
+
+/// A single response packet.
+pub const Response = struct {
+    op: Operation,
+    status: Status,
+    primary: bool = false,
+    id: []const u8 = "",
+    mime: ?[]const u8 = null,
+    pw: ?[]const u8 = null,
+    /// The raw payload; the encoder base64-encodes it. An empty payload
+    /// emits no payload section at all (no ';').
+    payload: []const u8 = "",
+    terminator: Terminator = .st,
+
+    /// Encode the response. Errors may result in partially written data
+    /// so it is up to callers to buffer it if they need to.
+    pub fn encode(
+        self: *const Response,
+        writer: *std.Io.Writer,
+    ) std.Io.Writer.Error!void {
+        try self.encodeMetadata(writer);
+        if (self.payload.len > 0) {
+            try writer.writeAll(";");
+            try b64.encodeWriter(writer, self.payload);
+        }
+        try writer.writeAll(self.terminator.string());
+    }
+
+    /// Encode the escape prefix and metadata section only: everything
+    /// up to (and not including) the payload section and terminator.
+    fn encodeMetadata(
+        self: *const Response,
+        writer: *std.Io.Writer,
+    ) std.Io.Writer.Error!void {
+        // The exact order of fields here matches what Kitty does.
+        try writer.print("\x1b]5522;type={t}:status={t}", .{ self.op, self.status });
+        if (self.primary) try writer.writeAll(":loc=primary");
+        if (self.id.len > 0) try writer.print(":id={s}", .{self.id});
+        if (self.mime) |mime| {
+            try writer.writeAll(":mime=");
+            try b64.encodeWriter(writer, mime);
+        }
+        if (self.pw) |pw| {
+            try writer.writeAll(":pw=");
+            try b64.encodeWriter(writer, pw);
+        }
+    }
+};
+
+/// Encode a full successful read response: the OK packet, the targets
+/// listing if requested, DATA chunks for each served representation,
+/// and the final DONE packet. This is also the shape of an unsolicited
+/// paste event (list=true, pw set to the one-time password).
+pub const ReadSuccess = struct {
+    primary: bool = false,
+    id: []const u8 = "",
+
+    /// One-time password echoed in every packet. Only used for
+    /// terminal-initiated paste events.
+    pw: ?[]const u8 = null,
+
+    /// True when the targets ('.') listing was requested.
+    list: bool = false,
+
+    /// The MIME types available on the clipboard, reported by the
+    /// targets listing. Kitty reports these space-separated in one
+    /// packet with a trailing newline when non-empty.
+    available: []const []const u8 = &.{},
+
+    /// The representations to serve, in request order. Each entry's
+    /// data is chunked into DATA packets under its own MIME type. An
+    /// entry with empty data produces no packets, which is how the
+    /// protocol communicates an unavailable type.
+    contents: []const Content = &.{},
+
+    terminator: Terminator = .st,
+
+    pub fn encode(
+        self: *const ReadSuccess,
+        writer: *std.Io.Writer,
+    ) std.Io.Writer.Error!void {
+        // Initial read response
+        try (Response{
+            .op = .read,
+            .status = .OK,
+            .primary = self.primary,
+            .id = self.id,
+            .pw = self.pw,
+            .terminator = self.terminator,
+        }).encode(writer);
+
+        // Listing of mimes if requested
+        if (self.list) try self.encodeListing(writer);
+
+        // Encoding of each mime-type + content
+        for (self.contents) |content| {
+            var i: usize = 0;
+            while (i < content.data.len) {
+                const n = @min(content.data.len - i, read_chunk_size);
+                try (Response{
+                    .op = .read,
+                    .status = .DATA,
+                    .id = self.id,
+                    .mime = content.mime,
+                    .pw = self.pw,
+                    .payload = content.data[i..][0..n],
+                    .terminator = self.terminator,
+                }).encode(writer);
+                i += n;
+            }
+        }
+
+        // Trailing done.
+        try (Response{
+            .op = .read,
+            .status = .DONE,
+            .id = self.id,
+            .pw = self.pw,
+            .terminator = self.terminator,
+        }).encode(writer);
+    }
+
+    /// Encode the targets ('.') listing packet. The listing gets a
+    /// trailing newline when non-empty.
+    fn encodeListing(
+        self: *const ReadSuccess,
+        writer: *std.Io.Writer,
+    ) std.Io.Writer.Error!void {
+        const listing: Response = .{
+            .op = .read,
+            .status = .DATA,
+            .id = self.id,
+            .mime = targets_mime,
+            .pw = self.pw,
+            .terminator = self.terminator,
+        };
+        try listing.encodeMetadata(writer);
+        if (self.available.len > 0) {
+            try writer.writeAll(";");
+
+            // Join the types into one chunk before encoding. The
+            // listing is a DATA packet, so it shares the pre-encoding
+            // chunk size bound of any other data packet; types that
+            // don't fit are dropped (a listing that large doesn't
+            // happen in practice).
+            var raw: [read_chunk_size]u8 = undefined;
+            var fixed: std.Io.Writer = .fixed(&raw);
+            for (self.available, 0..) |mime, i| {
+                const sep: usize = if (i > 0) 1 else 0;
+                if (fixed.end + sep + mime.len + "\n".len > raw.len) break;
+                if (i > 0) fixed.writeAll(" ") catch unreachable;
+                fixed.writeAll(mime) catch unreachable;
+            }
+            fixed.writeAll("\n") catch unreachable;
+            try b64.encodeWriter(writer, fixed.buffered());
+        }
+        try writer.writeAll(self.terminator.string());
+    }
+};
+
+test "response: basic status packet" {
+    const testing = std.testing;
+
+    var buf: [128]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (Response{ .op = .write, .status = .DONE }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=write:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "response: id echo and terminator" {
+    const testing = std.testing;
+
+    var buf: [128]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (Response{
+        .op = .write,
+        .status = .EPERM,
+        .id = "42",
+        .terminator = .bel,
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=write:status=EPERM:id=42\x07",
+        writer.buffered(),
+    );
+}
+
+test "response: key order type,status,loc,id,mime,pw and payload" {
+    const testing = std.testing;
+
+    var buf: [256]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (Response{
+        .op = .read,
+        .status = .DATA,
+        .primary = true,
+        .id = "x",
+        .mime = "text/plain",
+        .pw = "otp",
+        .payload = "Ghostty",
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=DATA:loc=primary:id=x" ++
+            ":mime=dGV4dC9wbGFpbg==:pw=b3Rw;R2hvc3R0eQ==\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: empty request is OK then DONE" {
+    const testing = std.testing;
+
+    var buf: [256]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{ .id = "7" }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK:id=7\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE:id=7\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: targets listing with text" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{ .list = true, .available = &.{"text/plain"} }).encode(&writer);
+    // "." => "Lg==", "text/plain\n" => "dGV4dC9wbGFpbgo="
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=Lg==;dGV4dC9wbGFpbgo=\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: targets listing joins multiple types" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{
+        .list = true,
+        .available = &.{ "text/plain", "image/png" },
+    }).encode(&writer);
+    // Payload is base64 of "text/plain image/png\n".
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=Lg==;dGV4dC9wbGFpbiBpbWFnZS9wbmcK\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: empty targets listing packet still sent" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{ .list = true }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=Lg==\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: data chunks under requested mime" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{
+        .contents = &.{.{ .mime = "text/plain", .data = "Ghostty" }},
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=dGV4dC9wbGFpbg==;R2hvc3R0eQ==\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: each representation carries its own data" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{
+        .contents = &.{
+            .{ .mime = "text/plain", .data = "hello" },
+            .{ .mime = "image/png", .data = "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a" },
+        },
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=dGV4dC9wbGFpbg==;aGVsbG8=\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=aW1hZ2UvcG5n;iVBORw0KGgo=\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: chunking at read_chunk_size" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const data = "z" ** (read_chunk_size + 1);
+    var aw: std.Io.Writer.Allocating = .init(alloc);
+    defer aw.deinit();
+    try (ReadSuccess{
+        .contents = &.{.{ .mime = "text/plain", .data = data }},
+    }).encode(&aw.writer);
+
+    // OK + 2 DATA packets + DONE = 4 packets.
+    const count = std.mem.count(u8, aw.written(), "\x1b]5522;");
+    try testing.expectEqual(@as(usize, 4), count);
+
+    // The first chunk is exactly read_chunk_size bytes, base64 encoded
+    // with padding.
+    const Encoder = std.base64.standard.Encoder;
+    var chunk_buf: [Encoder.calcSize(read_chunk_size)]u8 = undefined;
+    const first = Encoder.encode(&chunk_buf, data[0..read_chunk_size]);
+    try testing.expect(std.mem.indexOf(u8, aw.written(), first) != null);
+}
+
+test "read success: no data packets for empty clipboard" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{
+        .contents = &.{.{ .mime = "text/plain", .data = "" }},
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE\x1b\\",
+        writer.buffered(),
+    );
+}
+
+test "read success: paste event carries pw in every packet" {
+    const testing = std.testing;
+
+    var buf: [512]u8 = undefined;
+    var writer: std.Io.Writer = .fixed(&buf);
+    try (ReadSuccess{
+        .list = true,
+        .pw = "otp",
+        .available = &.{"text/plain"},
+    }).encode(&writer);
+    try testing.expectEqualStrings(
+        "\x1b]5522;type=read:status=OK:pw=b3Rw\x1b\\" ++
+            "\x1b]5522;type=read:status=DATA:mime=Lg==:pw=b3Rw;dGV4dC9wbGFpbgo=\x1b\\" ++
+            "\x1b]5522;type=read:status=DONE:pw=b3Rw\x1b\\",
+        writer.buffered(),
+    );
+}

From 7a940ec02830fcd39f94ea9a28974c2a82d96486 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:09:53 -0700
Subject: [PATCH 04/10] terminal: add kitty clipboard protocol (OSC 5522) write
 transactions

---
 src/terminal/kitty/clipboard.zig       |  13 +-
 src/terminal/kitty/clipboard_write.zig | 443 +++++++++++++++++++++++++
 2 files changed, 451 insertions(+), 5 deletions(-)
 create mode 100644 src/terminal/kitty/clipboard_write.zig

diff --git a/src/terminal/kitty/clipboard.zig b/src/terminal/kitty/clipboard.zig
index 7ef850bfe..4c9472e13 100644
--- a/src/terminal/kitty/clipboard.zig
+++ b/src/terminal/kitty/clipboard.zig
@@ -16,11 +16,7 @@
 //!   * `id` is sanitized by stripping characters outside [a-zA-Z0-9-_+.]
 //!     and truncating to 512 bytes, then echoed verbatim in every
 //!     response packet (omitted when empty).
-//!   * Write data chunks are decoded with a streaming base64 decoder that
-//!     persists across packets of the same MIME type; a '=' padding
-//!     mid-stream finishes the current group and resets the decoder, so
-//!     both per-chunk-padded and continuous unpadded streams work. A
-//!     chunk with invalid base64 is dropped (decoder reset) and the
+//!   * A write data chunk with invalid base64 is dropped and the
 //!     transaction continues; it is not a protocol error.
 //!   * A `type=write` silently replaces any in-flight transaction. A
 //!     commit (`type=wdata` without a MIME type) with no in-flight
@@ -37,6 +33,7 @@
 const oscpkg = @import("../osc.zig");
 const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
 const command = @import("clipboard_command.zig");
+const write = @import("clipboard_write.zig");
 const response = @import("clipboard_response.zig");
 
 pub const OSC = protocol.OSC;
@@ -51,6 +48,12 @@ pub const max_pw_len = command.max_pw_len;
 pub const max_mime_len = command.max_mime_len;
 pub const max_name_len = command.max_name_len;
 
+pub const Content = write.Content;
+pub const WriteState = write.WriteState;
+pub const max_write_size = write.max_write_size;
+pub const max_write_mimes = write.max_write_mimes;
+pub const max_write_aliases = write.max_write_aliases;
+
 pub const Response = response.Response;
 pub const ReadSuccess = response.ReadSuccess;
 pub const read_chunk_size = response.read_chunk_size;
diff --git a/src/terminal/kitty/clipboard_write.zig b/src/terminal/kitty/clipboard_write.zig
new file mode 100644
index 000000000..c4e33a4f3
--- /dev/null
+++ b/src/terminal/kitty/clipboard_write.zig
@@ -0,0 +1,443 @@
+//! Kitty clipboard protocol (OSC 5522) write transactions: the
+//! stateful accumulation of wdata chunks and walias aliases until the
+//! commit packet arrives. See clipboard.zig for the protocol overview.
+
+const std = @import("std");
+const assert = @import("../../quirks.zig").inlineAssert;
+const Allocator = std.mem.Allocator;
+const clipboard = @import("../clipboard.zig");
+const clipboard_command = @import("clipboard_command.zig");
+
+const Metadata = clipboard_command.Metadata;
+const Payload = clipboard_command.Payload;
+const max_mime_len = clipboard_command.max_mime_len;
+
+const log = std.log.scoped(.kitty_clipboard);
+
+/// Maximum total decoded bytes accumulated by one write transaction.
+/// We hardcode this for now but probably will make this configurable
+/// later.
+pub const max_write_size = 32 * 1024 * 1024;
+
+/// Maximum MIME types and aliases per write transaction.
+pub const max_write_mimes = 64;
+pub const max_write_aliases = 64;
+
+/// One MIME representation of committed clipboard data. This is the
+/// same type the clipboard write effect consumes so committed contents
+/// can be passed through directly.
+pub const Content = clipboard.Content;
+
+/// The state of one in-flight write transaction: a single `type=write`
+/// plus all the `wdata` chunks and `walias` aliases until completion
+/// or error.
+pub const WriteState = struct {
+    arena: std.heap.ArenaAllocator,
+    loc: clipboard.Location,
+    id: []const u8,
+    pw: []const u8,
+    has_name: bool,
+    spool: std.ArrayListUnmanaged(u8) = .empty,
+    entries: std.ArrayListUnmanaged(Entry) = .empty,
+    aliases: std.ArrayListUnmanaged(Alias) = .empty,
+
+    /// Index into entries currently receiving data.
+    current: ?usize = null,
+
+    /// Set when max_write_size was exceeded; excess data is dropped
+    /// but the write still completes.
+    truncated: bool = false,
+
+    const Entry = struct {
+        /// Owned by the transaction arena.
+        mime: []const u8,
+        start: usize = 0,
+        len: usize = 0,
+    };
+
+    const Alias = struct {
+        /// Owned by the transaction arena.
+        alias: []const u8,
+        target: []const u8,
+    };
+
+    /// Begin a transaction from a type=write packet.
+    pub fn init(alloc: Allocator, meta: *const Metadata) Allocator.Error!WriteState {
+        assert(meta.op == .write);
+        var arena: std.heap.ArenaAllocator = .init(alloc);
+        errdefer arena.deinit();
+        const id = try arena.allocator().dupe(u8, meta.id);
+        const pw = try arena.allocator().dupe(u8, meta.pw);
+        return .{
+            .arena = arena,
+            .loc = meta.loc,
+            .id = id,
+            .pw = pw,
+            .has_name = meta.has_name,
+        };
+    }
+
+    pub fn deinit(self: *WriteState, alloc: Allocator) void {
+        self.spool.deinit(alloc);
+        self.entries.deinit(alloc);
+        self.aliases.deinit(alloc);
+        self.arena.deinit();
+    }
+
+    /// Accumulate one wdata chunk carrying data for meta.mime (which
+    /// must be non-empty; an empty mime is a commit, not data).
+    pub fn data(
+        self: *WriteState,
+        alloc: Allocator,
+        meta: *const Metadata,
+        payload: []const u8,
+    ) error{OutOfMemory}!void {
+        assert(meta.op == .wdata);
+        assert(meta.mime.len > 0);
+        // Switch the receiving entry if this chunk is for a different
+        // MIME type than the last one.
+        entry: {
+            if (self.current) |idx| {
+                const entry = &self.entries.items[idx];
+                if (std.mem.eql(u8, entry.mime, meta.mime)) {
+                    break :entry;
+                }
+
+                // Finalize the previous region.
+                entry.len = self.spool.items.len - entry.start;
+            }
+
+            // Re-using an earlier MIME type starts a fresh region,
+            // overwriting the previous mapping.
+            for (self.entries.items, 0..) |*entry, idx| {
+                if (std.mem.eql(u8, entry.mime, meta.mime)) {
+                    entry.start = self.spool.items.len;
+                    entry.len = 0;
+                    self.current = idx;
+                    break :entry;
+                }
+            }
+
+            if (self.entries.items.len >= max_write_mimes) {
+                log.warn(
+                    "clipboard write has too many MIME types, ignoring mime={s}",
+                    .{meta.mime},
+                );
+                self.current = null;
+                return;
+            }
+
+            try self.entries.append(alloc, .{
+                .mime = try self.arena.allocator().dupe(u8, meta.mime),
+                .start = self.spool.items.len,
+            });
+            self.current = self.entries.items.len - 1;
+        }
+
+        // Each packet's payload is independently base64-encoded: per
+        // the spec, "payload is base64 encoded data" and clients chunk
+        // the data before encoding. An invalid chunk is dropped and
+        // the transaction continues.
+        const decoded = Payload.init(
+            alloc,
+            payload,
+        ) catch |err| switch (err) {
+            error.OutOfMemory => return error.OutOfMemory,
+            error.Invalid => {
+                log.warn("clipboard write chunk has invalid base64, ignoring chunk", .{});
+                return;
+            },
+        };
+        defer decoded.deinit(alloc);
+
+        const remaining = max_write_size -| self.spool.items.len;
+        const n = @min(decoded.data.len, remaining);
+        try self.spool.appendSlice(alloc, decoded.data[0..n]);
+        if (n < decoded.data.len) {
+            self.truncated = true;
+            logTruncatedOnce();
+        }
+    }
+
+    /// Register aliases from a walias packet: meta.mime is the target
+    /// (the type that carries data) and the payload is a base64-encoded,
+    /// whitespace-separated list of aliases. Returns error.Invalid for
+    /// an undecodable payload, which aborts the transaction with EINVAL.
+    pub fn alias(
+        self: *WriteState,
+        alloc: Allocator,
+        meta: *const Metadata,
+        payload: []const u8,
+    ) error{ OutOfMemory, Invalid }!void {
+        assert(meta.op == .walias);
+        assert(meta.mime.len > 0);
+        const decoded = try Payload.init(alloc, payload);
+        defer decoded.deinit(alloc);
+        var it = decoded.mimeIterator();
+
+        // Copy the target only if at least one valid alias exists.
+        const target: []const u8 = target: {
+            while (it.next()) |name| {
+                if (name.len > max_mime_len) continue;
+                break :target try self.arena.allocator().dupe(u8, meta.mime);
+            }
+
+            // If we didn't find a target then ignore it.
+            return;
+        };
+
+        // Rewind so the alias that satisfied the check above is
+        // associated too.
+        it.reset();
+
+        // Associate the aliases
+        while (it.next()) |name| {
+            if (name.len > max_mime_len) continue;
+
+            // A repeated alias overwrites its previous target.
+            for (self.aliases.items) |*a| {
+                if (std.mem.eql(u8, a.alias, name)) {
+                    a.target = target;
+                    break;
+                }
+            } else {
+                if (self.aliases.items.len >= max_write_aliases) {
+                    log.warn("clipboard write has too many aliases, ignoring", .{});
+                    return;
+                }
+
+                try self.aliases.append(alloc, .{
+                    .alias = try self.arena.allocator().dupe(u8, name),
+                    .target = target,
+                });
+            }
+        }
+    }
+
+    /// The result of a committed transaction. All slices borrow the
+    /// WriteState's memory and are valid until it is deinited.
+    pub const Committed = struct {
+        loc: clipboard.Location,
+        id: []const u8,
+        pw: []const u8,
+        has_name: bool,
+        truncated: bool,
+        contents: []const Content,
+
+        pub fn deinit(self: *const Committed, alloc: Allocator) void {
+            alloc.free(self.contents);
+        }
+    };
+
+    /// Commit the transaction (a wdata packet without a MIME type).
+    /// The caller must use the result, call Committed.deinit, and then
+    /// deinit this state.
+    pub fn commit(
+        self: *WriteState,
+        alloc: Allocator,
+    ) error{OutOfMemory}!Committed {
+        // Finalize the region receiving data.
+        if (self.current) |idx| {
+            const entry = &self.entries.items[idx];
+            entry.len = self.spool.items.len - entry.start;
+            self.current = null;
+        }
+
+        // Resolve the final MIME map: entries in arrival order, then
+        // aliases applied sequentially against the evolving map so
+        // chained aliases work like kitty's dict iteration. An alias
+        // whose target has no mapping is dropped; an alias colliding
+        // with an existing name overwrites it.
+        var contents: std.ArrayListUnmanaged(Content) = .empty;
+        defer contents.deinit(alloc);
+        try contents.ensureTotalCapacity(
+            alloc,
+            self.entries.items.len + self.aliases.items.len,
+        );
+
+        for (self.entries.items) |*entry| {
+            contents.appendAssumeCapacity(.{
+                .mime = entry.mime,
+                .data = self.spool.items[entry.start..][0..entry.len],
+            });
+        }
+
+        for (self.aliases.items) |*a| {
+            const target: Content = target: {
+                for (contents.items) |c| {
+                    if (std.mem.eql(u8, c.mime, a.target)) {
+                        break :target c;
+                    }
+                }
+                continue;
+            };
+
+            for (contents.items) |*c| {
+                if (std.mem.eql(u8, c.mime, a.alias)) {
+                    c.data = target.data;
+                    break;
+                }
+            } else {
+                contents.appendAssumeCapacity(.{
+                    .mime = a.alias,
+                    .data = target.data,
+                });
+            }
+        }
+
+        return .{
+            .loc = self.loc,
+            .id = self.id,
+            .pw = self.pw,
+            .has_name = self.has_name,
+            .truncated = self.truncated,
+            .contents = try contents.toOwnedSlice(alloc),
+        };
+    }
+
+    fn logTruncatedOnce() void {
+        // Log spam protection: this can be hit for every chunk of an
+        // oversized write.
+        const S = struct {
+            var logged: bool = false;
+        };
+        if (!S.logged) {
+            S.logged = true;
+            log.warn(
+                "clipboard write exceeds {} bytes, truncating",
+                .{max_write_size},
+            );
+        }
+    }
+};
+
+test "write: basic transaction" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write, .id = "42" };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "R2hvc3R0eQ=="); // "Ghostty"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqualStrings("42", committed.id);
+    try testing.expect(committed.loc == .standard);
+    try testing.expectEqual(@as(usize, 1), committed.contents.len);
+    try testing.expectEqualStrings("text/plain", committed.contents[0].mime);
+    try testing.expectEqualStrings("Ghostty", committed.contents[0].data);
+}
+
+test "write: chunked data accumulates" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "SGVsbG8="); // "Hello"
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "V29ybGQ="); // "World"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqualStrings("HelloWorld", committed.contents[0].data);
+}
+
+test "write: multiple mimes in order" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "YQ=="); // "a"
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/html" }, "Yg=="); // "b"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqual(@as(usize, 2), committed.contents.len);
+    try testing.expectEqualStrings("text/plain", committed.contents[0].mime);
+    try testing.expectEqualStrings("a", committed.contents[0].data);
+    try testing.expectEqualStrings("text/html", committed.contents[1].mime);
+    try testing.expectEqualStrings("b", committed.contents[1].data);
+}
+
+test "write: reused mime overwrites" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "YQ=="); // "a"
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/html" }, "Yg=="); // "b"
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "Yw=="); // "c"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqual(@as(usize, 2), committed.contents.len);
+    // Position preserved, data replaced.
+    try testing.expectEqualStrings("text/plain", committed.contents[0].mime);
+    try testing.expectEqualStrings("c", committed.contents[0].data);
+}
+
+test "write: invalid base64 chunk is dropped, transaction continues" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "SGVsbG8="); // "Hello"
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "!!!bad!!!");
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "V29ybGQ="); // "World"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqualStrings("HelloWorld", committed.contents[0].data);
+}
+
+test "write: aliases resolve at commit" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    try state.data(alloc, &.{ .op = .wdata, .mime = "text/plain" }, "R2hvc3R0eQ=="); // "Ghostty"
+
+    // Alias "TEXT UTF8_STRING" -> text/plain.
+    const alias_meta: Metadata = .{ .op = .walias, .mime = "text/plain" };
+    try state.alias(alloc, &alias_meta, "VEVYVCBVVEY4X1NUUklORw==");
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqual(@as(usize, 3), committed.contents.len);
+    try testing.expectEqualStrings("TEXT", committed.contents[1].mime);
+    try testing.expectEqualStrings("Ghostty", committed.contents[1].data);
+    try testing.expectEqualStrings("UTF8_STRING", committed.contents[2].mime);
+    try testing.expectEqualStrings("Ghostty", committed.contents[2].data);
+}
+
+test "write: alias without data target is dropped" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const begin_meta: Metadata = .{ .op = .write };
+    var state: WriteState = try .init(alloc, &begin_meta);
+    defer state.deinit(alloc);
+
+    const alias_meta: Metadata = .{ .op = .walias, .mime = "text/plain" };
+    try state.alias(alloc, &alias_meta, "VEVYVA=="); // "TEXT"
+
+    const committed = try state.commit(alloc);
+    defer committed.deinit(alloc);
+    try testing.expectEqual(@as(usize, 0), committed.contents.len);
+}

From 6f007e7678a4d893a5c73df2f0305b1e00609b5a Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:13:56 -0700
Subject: [PATCH 05/10] terminal: add kitty clipboard protocol (OSC 5522)
 session password grants

---
 src/terminal/kitty/clipboard.zig        |   5 +
 src/terminal/kitty/clipboard_grants.zig | 184 ++++++++++++++++++++++++
 2 files changed, 189 insertions(+)
 create mode 100644 src/terminal/kitty/clipboard_grants.zig

diff --git a/src/terminal/kitty/clipboard.zig b/src/terminal/kitty/clipboard.zig
index 4c9472e13..18271c704 100644
--- a/src/terminal/kitty/clipboard.zig
+++ b/src/terminal/kitty/clipboard.zig
@@ -35,6 +35,7 @@ const protocol = @import("../osc/parsers/kitty_clipboard_protocol.zig");
 const command = @import("clipboard_command.zig");
 const write = @import("clipboard_write.zig");
 const response = @import("clipboard_response.zig");
+const grants = @import("clipboard_grants.zig");
 
 pub const OSC = protocol.OSC;
 pub const Operation = protocol.Operation;
@@ -60,6 +61,10 @@ pub const read_chunk_size = response.read_chunk_size;
 pub const max_read_mimes = response.max_read_mimes;
 pub const targets_mime = response.targets_mime;
 
+pub const Grants = grants.Grants;
+pub const otp_len = grants.otp_len;
+pub const generateOtp = grants.generateOtp;
+
 test {
     @import("std").testing.refAllDecls(@This());
 }
diff --git a/src/terminal/kitty/clipboard_grants.zig b/src/terminal/kitty/clipboard_grants.zig
new file mode 100644
index 000000000..599e27e98
--- /dev/null
+++ b/src/terminal/kitty/clipboard_grants.zig
@@ -0,0 +1,184 @@
+//! Kitty clipboard protocol (OSC 5522) session password grants:
+//! requests carrying a granted password skip the permission prompt, and
+//! paste events mint one-time passwords.
+
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+const clipboard_command = @import("clipboard_command.zig");
+
+const max_pw_len = clipboard_command.max_pw_len;
+
+/// Session password grants, used to skip permission prompts for
+/// requests carrying a known pw. Callers can choose to scope these
+/// however they want, e.g. Kitty does it per window and the spec
+/// doesn't demand anything.
+pub const Grants = struct {
+    entries: std.ArrayListUnmanaged(Entry) = .empty,
+
+    const max_entries = 32;
+
+    pub const Direction = enum { read, write };
+
+    const Entry = struct {
+        /// Owned by the allocator passed to grant.
+        pw: []const u8,
+        read: bool = false,
+        write: bool = false,
+        one_time: bool = false,
+    };
+
+    pub fn deinit(self: *Grants, alloc: Allocator) void {
+        for (self.entries.items) |entry| alloc.free(entry.pw);
+        self.entries.deinit(alloc);
+    }
+
+    /// Record a grant for pw. An existing grant for the same password
+    /// gains the new direction.
+    pub fn grant(
+        self: *Grants,
+        alloc: Allocator,
+        pw: []const u8,
+        dir: Direction,
+        one_time: bool,
+    ) Allocator.Error!void {
+        if (pw.len == 0 or pw.len > max_pw_len) return;
+
+        const entry: *Entry = entry: {
+            if (self.findIndex(pw)) |idx| {
+                const entry = &self.entries.items[idx];
+                entry.one_time = entry.one_time and one_time;
+                break :entry entry;
+            }
+
+            // Evict the oldest grant once full.
+            if (self.entries.items.len >= max_entries) {
+                const oldest = self.entries.orderedRemove(0);
+                alloc.free(oldest.pw);
+            }
+
+            const owned = try alloc.dupe(u8, pw);
+            errdefer alloc.free(owned);
+            try self.entries.append(alloc, .{
+                .pw = owned,
+                .one_time = one_time,
+            });
+            break :entry &self.entries.items[self.entries.items.len - 1];
+        };
+
+        switch (dir) {
+            .read => entry.read = true,
+            .write => entry.write = true,
+        }
+    }
+
+    /// Check whether pw grants the given direction. A one-time grant is
+    /// consumed by this check even when the direction doesn't match,
+    /// matching kitty's pop-on-check behavior.
+    pub fn use(
+        self: *Grants,
+        alloc: Allocator,
+        pw: []const u8,
+        dir: Direction,
+    ) bool {
+        if (pw.len == 0) return false;
+        const idx = self.findIndex(pw) orelse return false;
+        const entry = &self.entries.items[idx];
+        const allowed = switch (dir) {
+            .read => entry.read,
+            .write => entry.write,
+        };
+        if (entry.one_time) {
+            const removed = self.entries.swapRemove(idx);
+            alloc.free(removed.pw);
+        }
+        return allowed;
+    }
+
+    fn findIndex(self: *const Grants, pw: []const u8) ?usize {
+        for (self.entries.items, 0..) |*entry, idx| {
+            if (std.mem.eql(u8, entry.pw, pw)) return idx;
+        }
+        return null;
+    }
+};
+
+/// The length of a one-time password generated for paste events.
+pub const otp_len = 22;
+
+/// Generate a one-time password for a paste event. The alphabet matches
+/// kitty (alphanumeric without easily-confused characters), but the spec
+/// doesn't demand this.
+pub fn generateOtp(random: std.Random) [otp_len]u8 {
+    const alphabet = "23456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";
+    var result: [otp_len]u8 = undefined;
+    for (&result) |*c| c.* = alphabet[random.uintLessThan(usize, alphabet.len)];
+    return result;
+}
+
+test "grants: basic grant and use" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var grants: Grants = .{};
+    defer grants.deinit(alloc);
+    try testing.expect(!grants.use(alloc, "pw1", .read));
+
+    try grants.grant(alloc, "pw1", .read, false);
+    try testing.expect(grants.use(alloc, "pw1", .read));
+    // Persistent grants survive use.
+    try testing.expect(grants.use(alloc, "pw1", .read));
+    try testing.expect(!grants.use(alloc, "pw1", .write));
+}
+
+test "grants: one-time consumed on check" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var grants: Grants = .{};
+    defer grants.deinit(alloc);
+    try grants.grant(alloc, "otp", .read, true);
+    try testing.expect(grants.use(alloc, "otp", .read));
+    try testing.expect(!grants.use(alloc, "otp", .read));
+}
+
+test "grants: one-time consumed even on direction mismatch" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var grants: Grants = .{};
+    defer grants.deinit(alloc);
+    try grants.grant(alloc, "otp", .read, true);
+    try testing.expect(!grants.use(alloc, "otp", .write));
+    try testing.expect(!grants.use(alloc, "otp", .read));
+}
+
+test "grants: directions are independent" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var grants: Grants = .{};
+    defer grants.deinit(alloc);
+    try grants.grant(alloc, "pw", .read, false);
+    try grants.grant(alloc, "pw", .write, false);
+    try testing.expect(grants.use(alloc, "pw", .read));
+    try testing.expect(grants.use(alloc, "pw", .write));
+}
+
+test "grants: capacity evicts the oldest" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var grants: Grants = .{};
+    defer grants.deinit(alloc);
+
+    var buf: [8]u8 = undefined;
+    for (0..Grants.max_entries + 1) |i| {
+        const pw = try std.fmt.bufPrint(&buf, "pw{}", .{i});
+        try grants.grant(alloc, pw, .read, false);
+    }
+
+    // The oldest grant was evicted; the newest survives.
+    try testing.expect(!grants.use(alloc, "pw0", .read));
+    const newest = try std.fmt.bufPrint(&buf, "pw{}", .{Grants.max_entries});
+    try testing.expect(grants.use(alloc, newest, .read));
+}

From f2d4b32be3eb8c17f1ca943dda82a6506e7260b3 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:15:07 -0700
Subject: [PATCH 06/10] terminal: expose kitty clipboard protocol (OSC 5522)
 for stream dispatch

---
 src/terminal/kitty.zig                                | 1 +
 src/terminal/osc/parsers/kitty_clipboard_protocol.zig | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/src/terminal/kitty.zig b/src/terminal/kitty.zig
index 0868a7710..471fb91e7 100644
--- a/src/terminal/kitty.zig
+++ b/src/terminal/kitty.zig
@@ -3,6 +3,7 @@
 const build_options = @import("terminal_options");
 
 const key = @import("kitty/key.zig");
+pub const clipboard = @import("kitty/clipboard.zig");
 pub const color = @import("kitty/color.zig");
 pub const graphics = if (build_options.kitty_graphics) @import("kitty/graphics.zig") else struct {};
 
diff --git a/src/terminal/osc/parsers/kitty_clipboard_protocol.zig b/src/terminal/osc/parsers/kitty_clipboard_protocol.zig
index 5bd0e2547..c257edd10 100644
--- a/src/terminal/osc/parsers/kitty_clipboard_protocol.zig
+++ b/src/terminal/osc/parsers/kitty_clipboard_protocol.zig
@@ -22,6 +22,12 @@ pub const OSC = struct {
     /// The terminator that was used in case we need to send a response.
     terminator: Terminator,
 
+    pub const C = void;
+
+    pub fn cval(_: OSC) C {
+        return {};
+    }
+
     /// Decode an option from the metadata.
     pub fn readOption(self: OSC, comptime key: Option) ?key.Type() {
         return key.read(self.metadata);

From 07c6fc21ba79f2d3d320f3300029269ebf84030b Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:16:38 -0700
Subject: [PATCH 07/10] terminal: add kitty clipboard paste events mode (5522),
 disabled for now

---
 include/ghostty/vt/modes.h | 1 +
 src/terminal/modes.zig     | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/ghostty/vt/modes.h b/include/ghostty/vt/modes.h
index fbef4e52b..6786f004b 100644
--- a/include/ghostty/vt/modes.h
+++ b/include/ghostty/vt/modes.h
@@ -94,6 +94,7 @@ extern "C" {
 #define GHOSTTY_MODE_COLOR_SCHEME_REPORT (ghostty_mode_new(2031, false)) /**< Report color scheme */
 #define GHOSTTY_MODE_VISIBILITY_REPORT (ghostty_mode_new(2033, false)) /**< Report terminal visibility */
 #define GHOSTTY_MODE_IN_BAND_RESIZE   (ghostty_mode_new(2048, false)) /**< In-band size reports */
+#define GHOSTTY_MODE_PASTE_EVENTS     (ghostty_mode_new(5522, false)) /**< Kitty clipboard protocol paste events */
 /** @} */
 
 /**
diff --git a/src/terminal/modes.zig b/src/terminal/modes.zig
index c545b3304..9b95e85ce 100644
--- a/src/terminal/modes.zig
+++ b/src/terminal/modes.zig
@@ -327,6 +327,15 @@ const entries: []const ModeEntry = &.{
     .{ .name = "report_color_scheme", .value = 2031 },
     .{ .name = "report_visibility", .value = 2033, .default_configurable = false },
     .{ .name = "in_band_size_reports", .value = 2048 },
+    // Kitty clipboard protocol paste events. When set, a user-initiated
+    // paste sends an unsolicited OSC 5522 targets listing with a
+    // one-time password instead of pasting the text.
+    // See https://sw.kovidgoyal.net/kitty/clipboard/
+    //
+    // Disabled until the apprt paste integration lands; until then the
+    // mode reports as unrecognized so applications correctly detect
+    // paste events as unsupported.
+    .{ .name = "paste_events", .value = 5522, .disabled = true },
 };
 
 test {

From bcf44b40e69ffc4f32216016bb8e6ee68560cae2 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:19:14 -0700
Subject: [PATCH 08/10] terminal: dispatch OSC 5522 as a kitty_clipboard stream
 action, unhandled

---
 src/terminal/stream.zig          | 9 ++++++++-
 src/terminal/stream_terminal.zig | 2 ++
 src/termio/stream_handler.zig    | 1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/terminal/stream.zig b/src/terminal/stream.zig
index 105cd1e4f..4308adf9f 100644
--- a/src/terminal/stream.zig
+++ b/src/terminal/stream.zig
@@ -128,6 +128,7 @@ pub const Action = union(Key) {
     kitty_color_report: kitty.color.OSC,
     color_operation: ColorOperation,
     semantic_prompt: SemanticPrompt,
+    kitty_clipboard: KittyClipboard,
 
     pub const Key = lib.Enum(
         lib.target,
@@ -227,6 +228,7 @@ pub const Action = union(Key) {
             "kitty_color_report",
             "color_operation",
             "semantic_prompt",
+            "kitty_clipboard",
         },
     );
 
@@ -444,6 +446,8 @@ pub const Action = union(Key) {
     };
 
     pub const SemanticPrompt = osc.Command.SemanticPrompt;
+
+    pub const KittyClipboard = osc.Command.KittyClipboardProtocol;
 };
 
 /// Returns a type that can process a stream of tty control characters.
@@ -2551,6 +2555,10 @@ pub fn Stream(comptime H: type) type {
                     self.handler.vt(.progress_report, v);
                 },
 
+                .kitty_clipboard_protocol => |v| {
+                    self.handler.vt(.kitty_clipboard, v);
+                },
+
                 .conemu_sleep,
                 .conemu_show_message_box,
                 .conemu_change_tab_title,
@@ -2561,7 +2569,6 @@ pub fn Stream(comptime H: type) type {
                 .conemu_output_environment_variable,
                 .conemu_run_process,
                 .kitty_text_sizing,
-                .kitty_clipboard_protocol,
                 .kitty_dnd_protocol,
                 .context_signal,
                 => {
diff --git a/src/terminal/stream_terminal.zig b/src/terminal/stream_terminal.zig
index 1b1ad6c65..d19324886 100644
--- a/src/terminal/stream_terminal.zig
+++ b/src/terminal/stream_terminal.zig
@@ -398,6 +398,8 @@ pub const Handler = struct {
             // Have no terminal-modifying effect
             .title_push,
             .title_pop,
+            // Unimplemented; the sequence is consumed and ignored.
+            .kitty_clipboard,
             => {},
         }
     }
diff --git a/src/termio/stream_handler.zig b/src/termio/stream_handler.zig
index cf6bca909..192e51644 100644
--- a/src/termio/stream_handler.zig
+++ b/src/termio/stream_handler.zig
@@ -356,6 +356,7 @@ pub const StreamHandler = struct {
             // Unimplemented
             .title_push,
             .title_pop,
+            .kitty_clipboard,
             => {},
         }
     }

From 128ec7cd047ab0d9ceb4f0b5c2c449984702266d Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:26:56 -0700
Subject: [PATCH 09/10] terminal: rename paste_events mode to
 kitty_paste_events

---
 src/terminal/modes.zig             |  7 +++----
 src/terminal/snapshot/snapshot.ksy |  6 ++++--
 src/terminal/snapshot/terminal.zig | 30 ++++++++++++++++++++----------
 3 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/src/terminal/modes.zig b/src/terminal/modes.zig
index 9b95e85ce..baacd0089 100644
--- a/src/terminal/modes.zig
+++ b/src/terminal/modes.zig
@@ -332,10 +332,9 @@ const entries: []const ModeEntry = &.{
     // one-time password instead of pasting the text.
     // See https://sw.kovidgoyal.net/kitty/clipboard/
     //
-    // Disabled until the apprt paste integration lands; until then the
-    // mode reports as unrecognized so applications correctly detect
-    // paste events as unsupported.
-    .{ .name = "paste_events", .value = 5522, .disabled = true },
+    // Forcibly disabled for now since the functionality isn't exposed
+    // yet to libghostty or any GUI apps.
+    .{ .name = "kitty_paste_events", .value = 5522, .disabled = true },
 };
 
 test {
diff --git a/src/terminal/snapshot/snapshot.ksy b/src/terminal/snapshot/snapshot.ksy
index 80a1d182f..2da917ea3 100644
--- a/src/terminal/snapshot/snapshot.ksy
+++ b/src/terminal/snapshot/snapshot.ksy
@@ -390,13 +390,13 @@ types:
       Each named instance exposes one bit from the little-endian integer.
       Arithmetic division is used instead of bitwise operations because the
       JavaScript target implements those operations with signed 32-bit values.
-      All values remain exact because the registry occupies only 42 bits,
+      All values remain exact because the registry occupies only 43 bits,
       within JavaScript's 53-bit safe integer range.
     seq:
       - id: raw
         type: u8
         valid:
-          max: 4398046511103
+          max: 8796093022207
     instances:
       disable_keyboard:
         value: (raw / 1) % 2 != 0
@@ -482,6 +482,8 @@ types:
         value: (raw / 1099511627776) % 2 != 0
       in_band_size_reports:
         value: (raw / 2199023255552) % 2 != 0
+      kitty_paste_events:
+        value: (raw / 4398046511104) % 2 != 0
 
   tab_stops:
     params:
diff --git a/src/terminal/snapshot/terminal.zig b/src/terminal/snapshot/terminal.zig
index f20b97707..11c9004bb 100644
--- a/src/terminal/snapshot/terminal.zig
+++ b/src/terminal/snapshot/terminal.zig
@@ -206,7 +206,8 @@
 //! bit 39  report_color_scheme
 //! bit 40  report_visibility
 //! bit 41  in_band_size_reports
-//! bits 42-63  reserved, zero
+//! bit 42  kitty_paste_events
+//! bits 43-63  reserved, zero
 //! ```
 //!
 //! This is the packed field order of native `ModePacked`. Its layout is
@@ -470,7 +471,7 @@ pub const Header = struct {
         try writer.writeByte(@intCast(@intFromEnum(self.mouse_shape)));
         try writer.writeByte(@intFromBool(self.password_input));
 
-        // Runtime, saved, and reset mode sets. ModePacked occupies 41 bits;
+        // Runtime, saved, and reset mode sets. ModePacked occupies 43 bits;
         // its eight-byte wire slots zero-extend the native packed value.
         const mode_values = [_]terminal_modes.ModePacked{
             self.current_modes,
@@ -1203,7 +1204,7 @@ const test_header_fixture = test_fixture.parse(
 
 test "TERMINAL mode bit layout" {
     try std.testing.expectEqual(
-        @as(usize, 42),
+        @as(usize, 43),
         @bitSizeOf(terminal_modes.ModePacked),
     );
 
@@ -1212,8 +1213,8 @@ test "TERMINAL mode bit layout" {
     );
     first.disable_keyboard = true;
     try std.testing.expectEqual(
-        @as(u42, 1) << 0,
-        @as(u42, @bitCast(first)),
+        @as(u43, 1) << 0,
+        @as(u43, @bitCast(first)),
     );
 
     var visibility: terminal_modes.ModePacked = std.mem.zeroes(
@@ -1221,17 +1222,26 @@ test "TERMINAL mode bit layout" {
     );
     visibility.report_visibility = true;
     try std.testing.expectEqual(
-        @as(u42, 1) << 40,
-        @as(u42, @bitCast(visibility)),
+        @as(u43, 1) << 40,
+        @as(u43, @bitCast(visibility)),
+    );
+
+    var size_reports: terminal_modes.ModePacked = std.mem.zeroes(
+        terminal_modes.ModePacked,
+    );
+    size_reports.in_band_size_reports = true;
+    try std.testing.expectEqual(
+        @as(u43, 1) << 41,
+        @as(u43, @bitCast(size_reports)),
     );
 
     var last: terminal_modes.ModePacked = std.mem.zeroes(
         terminal_modes.ModePacked,
     );
-    last.in_band_size_reports = true;
+    last.kitty_paste_events = true;
     try std.testing.expectEqual(
-        @as(u42, 1) << 41,
-        @as(u42, @bitCast(last)),
+        @as(u43, 1) << 42,
+        @as(u43, @bitCast(last)),
     );
 }
 

From a8c3ab1915c9dc9cecf4ae93b5337d65f1bfffbf Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Fri, 21 Aug 2026 12:45:35 -0700
Subject: [PATCH 10/10] simd: fix scalar base64 empty input handling causing a
 crash

---
 src/simd/base64.zig | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/simd/base64.zig b/src/simd/base64.zig
index 81feeb723..a0ba45ea9 100644
--- a/src/simd/base64.zig
+++ b/src/simd/base64.zig
@@ -53,9 +53,9 @@ fn decodeScalar(
 /// For non-SIMD enabled builds, we trim the padding from the end of the
 /// base64 input in order to get identical output with the SIMD version.
 fn scalarInput(input: []const u8) []const u8 {
-    var i: usize = 0;
-    while (input[input.len - i - 1] == '=') i += 1;
-    return input[0 .. input.len - i];
+    var end = input.len;
+    while (end > 0 and input[end - 1] == '=') end -= 1;
+    return input[0..end];
 }
 
 // base64.cpp
@@ -75,6 +75,14 @@ test "base64 maxLen" {
     try testing.expectEqual(11, len);
 }
 
+test "base64 empty input" {
+    const testing = std.testing;
+    var output: [0]u8 = .{};
+
+    try testing.expectEqual(0, maxLen(""));
+    try testing.expectEqualStrings("", try decode("", &output));
+}
+
 test "base64 decode" {
     const testing = std.testing;
     const alloc = testing.allocator;