diff --git a/test/pyxtest/meson.build b/test/pyxtest/meson.build
index d7091d462..b70bd5576 100644
--- a/test/pyxtest/meson.build
+++ b/test/pyxtest/meson.build
@@ -55,11 +55,17 @@ if pytest.found()
 
     # This needs to be kept in sync with the test_foo.py files in the tree
     tests_pyxtest = [
+        'test_present.py',
         'test_randr.py',
         'test_record.py',
+        'test_render.py',
         'test_screensaver.py',
+        'test_shm.py',
+        'test_vidmode.py',
+        'test_xinerama.py',
         'test_xi.py',
         'test_xkb.py',
+        'test_xres.py',
     ]
 
     test_list_data = configuration_data()
diff --git a/test/pyxtest/proto/present.py b/test/pyxtest/proto/present.py
new file mode 100644
index 000000000..b2e1d888a
--- /dev/null
+++ b/test/pyxtest/proto/present.py
@@ -0,0 +1,157 @@
+# SPDX-License-Identifier: MIT
+#
+# Present extension protocol request builders for byteswap testing.
+
+import struct
+from dataclasses import dataclass
+
+# Present minor opcodes
+PresentQueryVersion = 0
+PresentPixmap = 1
+PresentNotifyMSC = 2
+PresentSelectInput = 3
+PresentQueryCapabilities = 4
+
+
+@dataclass
+class QueryVersionRequest:
+    """PresentQueryVersion request."""
+
+    opcode: int
+    major: int = 1
+    minor: int = 2
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHII",
+            self.opcode,
+            PresentQueryVersion,
+            3,
+            self.major,
+            self.minor,
+        )
+
+
+@dataclass
+class SelectInputRequest:
+    """PresentSelectInput request."""
+
+    opcode: int
+    eid: int
+    window: int
+    event_mask: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH III",
+            self.opcode,
+            PresentSelectInput,
+            4,
+            self.eid,
+            self.window,
+            self.event_mask,
+        )
+
+
+@dataclass
+class QueryCapabilitiesRequest:
+    """PresentQueryCapabilities request."""
+
+    opcode: int
+    target: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH I",
+            self.opcode,
+            PresentQueryCapabilities,
+            2,
+            self.target,
+        )
+
+
+@dataclass
+class PixmapRequest:
+    """PresentPixmap request.
+
+    This is a large request with many fields. All fields are included
+    to test that byte-swapping handles them all correctly.
+    """
+
+    opcode: int
+    window: int
+    pixmap: int
+    serial: int = 0
+    valid: int = 0  # region or None
+    update: int = 0  # region or None
+    x_off: int = 0
+    y_off: int = 0
+    target_crtc: int = 0
+    wait_fence: int = 0
+    idle_fence: int = 0
+    options: int = 0
+    target_msc: int = 0
+    divisor: int = 0
+    remainder: int = 0
+    # notifies follow but we omit them for testing
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH"  # header: opcode, sub-opcode, length
+            f"III"  # window, pixmap, serial
+            f"II"  # valid, update
+            f"hh"  # x_off, y_off
+            f"III"  # target_crtc, wait_fence, idle_fence
+            f"I"  # options
+            f"xxxx"  # pad
+            f"Q"  # target_msc (CARD64)
+            f"Q"  # divisor (CARD64)
+            f"Q",  # remainder (CARD64)
+            self.opcode,
+            PresentPixmap,
+            18,  # 72 bytes = 18 words
+            self.window,
+            self.pixmap,
+            self.serial,
+            self.valid,
+            self.update,
+            self.x_off,
+            self.y_off,
+            self.target_crtc,
+            self.wait_fence,
+            self.idle_fence,
+            self.options,
+            self.target_msc,
+            self.divisor,
+            self.remainder,
+        )
+
+
+@dataclass
+class NotifyMSCRequest:
+    """PresentNotifyMSC request."""
+
+    opcode: int
+    window: int
+    serial: int = 0
+    target_msc: int = 0
+    divisor: int = 0
+    remainder: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH"
+            f"II"  # window, serial
+            f"xxxx"  # pad
+            f"Q"  # target_msc
+            f"Q"  # divisor
+            f"Q",  # remainder
+            self.opcode,
+            PresentNotifyMSC,
+            10,  # 40 bytes = 10 words
+            self.window,
+            self.serial,
+            self.target_msc,
+            self.divisor,
+            self.remainder,
+        )
diff --git a/test/pyxtest/proto/randr.py b/test/pyxtest/proto/randr.py
index 35b879ee8..f131c3d00 100644
--- a/test/pyxtest/proto/randr.py
+++ b/test/pyxtest/proto/randr.py
@@ -7,10 +7,17 @@ from dataclasses import dataclass
 
 # RandR minor opcodes
 RRQueryVersion = 0
+RRSetScreenConfig = 2
+RRSelectInput = 4
 RRGetScreenResources = 8
+RRGetOutputInfo = 9
+RRCreateMode = 16
 RRChangeOutputProperty = 13
 RRGetOutputProperty = 15
 RRGetScreenResourcesCurrent = 25
+RRGetProviderInfo = 33
+RRCreateLease = 45
+RRFreeLease = 46
 
 RR_MAJOR = 1
 RR_MINOR = 6
@@ -132,3 +139,127 @@ class GetOutputPropertyRequest:
             1 if self.pending else 0,
             0,  # pad
         )
+
+
+@dataclass
+class SetScreenConfigRequest:
+    """RRSetScreenConfig request (RandR 1.1 format with rate)."""
+
+    opcode: int
+    drawable: int
+    timestamp: int = 0
+    config_timestamp: int = 0
+    size_id: int = 0
+    rotation: int = 1  # RR_Rotate_0
+    rate: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH I II HH H xx",
+            self.opcode,
+            RRSetScreenConfig,
+            6,  # 24 bytes = 6 words
+            self.drawable,
+            self.timestamp,
+            self.config_timestamp,
+            self.size_id,
+            self.rotation,
+            self.rate,
+        )
+
+
+@dataclass
+class GetScreenResourcesRequest:
+    """RRGetScreenResources request."""
+
+    opcode: int
+    window: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHI",
+            self.opcode,
+            RRGetScreenResources,
+            2,
+            self.window,
+        )
+
+
+@dataclass
+class CreateLeaseRequest:
+    """RRCreateLease request.
+
+    Header is 16 bytes followed by nCrtcs CARD32 crtc IDs and
+    nOutputs CARD32 output IDs.
+    """
+
+    opcode: int
+    window: int
+    lid: int
+    crtcs: list[int] | None = None
+    outputs: list[int] | None = None
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        crtc_list = self.crtcs or []
+        output_list = self.outputs or []
+
+        crtc_data = b""
+        for c in crtc_list:
+            crtc_data += struct.pack(f"{byte_order}I", c)
+        output_data = b""
+        for o in output_list:
+            output_data += struct.pack(f"{byte_order}I", o)
+
+        total = 16 + len(crtc_data) + len(output_data)
+        pad_len = (4 - total % 4) % 4
+        length = (total + pad_len) // 4
+
+        header = struct.pack(
+            f"{byte_order}BBH II HH",
+            self.opcode,
+            RRCreateLease,
+            length,
+            self.window,
+            self.lid,
+            len(crtc_list),
+            len(output_list),
+        )
+        return header + crtc_data + output_data + b"\x00" * pad_len
+
+
+@dataclass
+class SelectInputRequest:
+    """RRSelectInput request."""
+
+    opcode: int
+    window: int
+    enable: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH I H xx",
+            self.opcode,
+            RRSelectInput,
+            3,
+            self.window,
+            self.enable,
+        )
+
+
+@dataclass
+class GetProviderInfoRequest:
+    """RRGetProviderInfo request."""
+
+    opcode: int
+    provider: int
+    config_timestamp: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH II",
+            self.opcode,
+            RRGetProviderInfo,
+            3,
+            self.provider,
+            self.config_timestamp,
+        )
diff --git a/test/pyxtest/proto/render.py b/test/pyxtest/proto/render.py
new file mode 100644
index 000000000..c6c88fc72
--- /dev/null
+++ b/test/pyxtest/proto/render.py
@@ -0,0 +1,193 @@
+# SPDX-License-Identifier: MIT
+#
+# Render extension protocol request builders
+
+import struct
+from dataclasses import dataclass, field
+
+# Render minor opcodes
+RenderQueryVersion = 0
+RenderQueryPictFormats = 1
+RenderCreatePicture = 4
+RenderCreateGlyphSet = 17
+RenderCompositeGlyphs8 = 23
+RenderCompositeGlyphs16 = 24
+RenderCompositeGlyphs32 = 25
+RenderSetPictureFilter = 30
+
+
+@dataclass
+class QueryVersionRequest:
+    """RenderQueryVersion request."""
+
+    opcode: int
+    major: int = 0
+    minor: int = 11
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHII",
+            self.opcode,
+            RenderQueryVersion,
+            3,
+            self.major,
+            self.minor,
+        )
+
+
+@dataclass
+class QueryPictFormatsRequest:
+    """RenderQueryPictFormats request."""
+
+    opcode: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH",
+            self.opcode,
+            RenderQueryPictFormats,
+            1,
+        )
+
+
+@dataclass
+class CreatePictureRequest:
+    """RenderCreatePicture request."""
+
+    opcode: int
+    picture_id: int
+    drawable: int
+    format_id: int
+    value_mask: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHIIII",
+            self.opcode,
+            RenderCreatePicture,
+            5,
+            self.picture_id,
+            self.drawable,
+            self.format_id,
+            self.value_mask,
+        )
+
+
+@dataclass
+class CreateGlyphSetRequest:
+    """RenderCreateGlyphSet request."""
+
+    opcode: int
+    glyph_set_id: int
+    format_id: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHII",
+            self.opcode,
+            RenderCreateGlyphSet,
+            3,
+            self.glyph_set_id,
+            self.format_id,
+        )
+
+
+@dataclass
+class _CompositeGlyphsRequestBase:
+    """Base class for RenderCompositeGlyphs{8,16,32} requests.
+
+    glyph_elts is raw xGlyphElt + glyph ID data.
+    Subclasses set _minor_opcode for the glyph size (8/16/32 bit IDs).
+    """
+
+    _minor_opcode: int = field(default=0, init=False, repr=False)
+
+    opcode: int = 0
+    src_picture: int = 0
+    dst_picture: int = 0
+    glyph_set: int = 0
+    mask_format: int = 0
+    op: int = 3  # PictOpOver
+    src_x: int = 0
+    src_y: int = 0
+    glyph_elts: bytes = b""
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        total = 28 + len(self.glyph_elts)
+        pad_len = (4 - total % 4) % 4
+        length = (total + pad_len) // 4
+
+        header = struct.pack(
+            f"{byte_order}BBH BxH IIII hh",
+            self.opcode,
+            self._minor_opcode,
+            length,
+            self.op,
+            0,  # pad2
+            self.src_picture,
+            self.dst_picture,
+            self.mask_format,
+            self.glyph_set,
+            self.src_x,
+            self.src_y,
+        )
+        return header + self.glyph_elts + b"\x00" * pad_len
+
+
+@dataclass
+class CompositeGlyphs8Request(_CompositeGlyphsRequestBase):
+    """RenderCompositeGlyphs8 request (minor opcode 23)."""
+
+    _minor_opcode: int = field(default=RenderCompositeGlyphs8, init=False, repr=False)
+
+
+@dataclass
+class CompositeGlyphs16Request(_CompositeGlyphsRequestBase):
+    """RenderCompositeGlyphs16 request (minor opcode 24)."""
+
+    _minor_opcode: int = field(default=RenderCompositeGlyphs16, init=False, repr=False)
+
+
+@dataclass
+class CompositeGlyphs32Request(_CompositeGlyphsRequestBase):
+    """RenderCompositeGlyphs32 request (minor opcode 25)."""
+
+    _minor_opcode: int = field(default=RenderCompositeGlyphs32, init=False, repr=False)
+
+
+@dataclass
+class SetPictureFilterRequest:
+    """RenderSetPictureFilter request.
+
+    The filter name is a variable-length string followed by padding,
+    then xFixed (CARD32) filter parameter values.
+    """
+
+    opcode: int
+    picture: int
+    filter_name: str = "nearest"
+    params: list[int] | None = None  # xFixed values (CARD32)
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        name_bytes = self.filter_name.encode("ascii")
+        name_len = len(name_bytes)
+        name_padded = name_bytes + b"\x00" * ((4 - name_len % 4) % 4)
+
+        param_data = b""
+        if self.params:
+            for p in self.params:
+                param_data += struct.pack(f"{byte_order}I", p)
+
+        total = 12 + len(name_padded) + len(param_data)
+        pad_len = (4 - total % 4) % 4
+        length = (total + pad_len) // 4
+
+        header = struct.pack(
+            f"{byte_order}BBH I H xx",
+            self.opcode,
+            RenderSetPictureFilter,
+            length,
+            self.picture,
+            name_len,
+        )
+        return header + name_padded + param_data + b"\x00" * pad_len
diff --git a/test/pyxtest/proto/shm.py b/test/pyxtest/proto/shm.py
new file mode 100644
index 000000000..0c584beda
--- /dev/null
+++ b/test/pyxtest/proto/shm.py
@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: MIT
+#
+# MIT-SHM extension protocol request builders for byteswap testing.
+
+import struct
+from dataclasses import dataclass
+
+# SHM minor opcodes
+ShmQueryVersion = 0
+ShmAttach = 1
+ShmDetach = 2
+ShmPutImage = 3
+ShmGetImage = 4
+ShmCreatePixmap = 5
+ShmAttachFd = 6
+ShmCreateSegment = 7
+
+
+@dataclass
+class QueryVersionRequest:
+    """ShmQueryVersion request."""
+
+    opcode: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH",
+            self.opcode,
+            ShmQueryVersion,
+            1,
+        )
+
+
+@dataclass
+class CreateSegmentRequest:
+    """ShmCreateSegment request.
+
+    Creates a shared memory segment owned by the server.
+    Returns a file descriptor and whether the segment is read-only.
+    """
+
+    opcode: int
+    shmseg: int
+    size: int
+    read_only: bool = False
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH II Bxxx",
+            self.opcode,
+            ShmCreateSegment,
+            4,  # 16 bytes = 4 words
+            self.shmseg,
+            self.size,
+            1 if self.read_only else 0,
+        )
diff --git a/test/pyxtest/proto/vidmode.py b/test/pyxtest/proto/vidmode.py
new file mode 100644
index 000000000..6a9eebb95
--- /dev/null
+++ b/test/pyxtest/proto/vidmode.py
@@ -0,0 +1,198 @@
+# SPDX-License-Identifier: MIT
+#
+# XFree86-VidModeExtension protocol request builders for byteswap testing.
+
+import struct
+from dataclasses import dataclass
+
+# VidMode minor opcodes
+VidModeQueryVersion = 0
+VidModeGetModeLine = 1
+VidModeModModeLine = 2
+VidModeSwitchMode = 3
+VidModeGetMonitor = 4
+VidModeLockModeSwitch = 5
+VidModeGetAllModeLines = 6
+VidModeAddModeLine = 7
+VidModeDeleteModeLine = 8
+VidModeValidateModeLine = 9
+VidModeSwitchToMode = 10
+VidModeGetViewPort = 11
+VidModeSetViewPort = 12
+
+
+@dataclass
+class QueryVersionRequest:
+    """VidModeQueryVersion request."""
+
+    opcode: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH",
+            self.opcode,
+            VidModeQueryVersion,
+            1,
+        )
+
+
+@dataclass
+class GetModeLineRequest:
+    """VidModeGetModeLine request."""
+
+    opcode: int
+    screen: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH H xx",
+            self.opcode,
+            VidModeGetModeLine,
+            2,
+            self.screen,
+        )
+
+
+@dataclass
+class SwitchModeRequest:
+    """VidModeSwitchMode request."""
+
+    opcode: int
+    screen: int = 0
+    zoom: int = 1
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH HH",
+            self.opcode,
+            VidModeSwitchMode,
+            2,
+            self.screen,
+            self.zoom,
+        )
+
+
+@dataclass
+class SwitchToModeRequest:
+    """VidModeSwitchToMode request (v2 format, 52 bytes).
+
+    xXF86VidModeSwitchToModeReq:
+      reqType(1) + xf86vidmodeReqType(1) + length(2) +
+      screen(4) + dotclock(4) +
+      hdisplay(2) + hsyncstart(2) + hsyncend(2) + htotal(2) + hskew(2) +
+      vdisplay(2) + vsyncstart(2) + vsyncend(2) + vtotal(2) + pad1(2) +
+      flags(4) + reserved1(4) + reserved2(4) + reserved3(4) + privsize(4)
+    """
+
+    opcode: int
+    screen: int = 0
+    dotclock: int = 0
+    hdisplay: int = 0
+    hsyncstart: int = 0
+    hsyncend: int = 0
+    htotal: int = 0
+    hskew: int = 0
+    vdisplay: int = 0
+    vsyncstart: int = 0
+    vsyncend: int = 0
+    vtotal: int = 0
+    flags: int = 0
+    privsize: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH"  # header (4)
+            f"I"  # screen (4)
+            f"I"  # dotclock (4)
+            f"HHHHH"  # hdisplay, hsyncstart, hsyncend, htotal, hskew (10)
+            f"HHHH"  # vdisplay, vsyncstart, vsyncend, vtotal (8)
+            f"xx"  # pad1 (2)
+            f"I"  # flags (4)
+            f"I"  # reserved1 (4)
+            f"I"  # reserved2 (4)
+            f"I"  # reserved3 (4)
+            f"I",  # privsize (4)
+            self.opcode,
+            VidModeSwitchToMode,
+            13,  # 52 bytes = 13 words
+            self.screen,
+            self.dotclock,
+            self.hdisplay,
+            self.hsyncstart,
+            self.hsyncend,
+            self.htotal,
+            self.hskew,
+            self.vdisplay,
+            self.vsyncstart,
+            self.vsyncend,
+            self.vtotal,
+            self.flags,
+            0,  # reserved1
+            0,  # reserved2
+            0,  # reserved3
+            self.privsize,
+        )
+
+
+@dataclass
+class GetAllModeLinesRequest:
+    """VidModeGetAllModeLines request."""
+
+    opcode: int
+    screen: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH H xx",
+            self.opcode,
+            VidModeGetAllModeLines,
+            2,
+            self.screen,
+        )
+
+
+@dataclass
+class ValidateModeLineRequest:
+    """VidModeValidateModeLine request (v2 format, 52 bytes).
+
+    Same layout as SwitchToModeRequest.
+    """
+
+    opcode: int
+    screen: int = 0
+    dotclock: int = 0
+    hdisplay: int = 0
+    hsyncstart: int = 0
+    hsyncend: int = 0
+    htotal: int = 0
+    hskew: int = 0
+    vdisplay: int = 0
+    vsyncstart: int = 0
+    vsyncend: int = 0
+    vtotal: int = 0
+    flags: int = 0
+    privsize: int = 0
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHIIHHHHHHHHHxxIIIII",
+            self.opcode,
+            VidModeValidateModeLine,
+            13,  # 52 bytes = 13 words
+            self.screen,
+            self.dotclock,
+            self.hdisplay,
+            self.hsyncstart,
+            self.hsyncend,
+            self.htotal,
+            self.hskew,
+            self.vdisplay,
+            self.vsyncstart,
+            self.vsyncend,
+            self.vtotal,
+            self.flags,
+            0,  # reserved1
+            0,  # reserved2
+            0,  # reserved3
+            self.privsize,
+        )
diff --git a/test/pyxtest/proto/xi.py b/test/pyxtest/proto/xi.py
index 20f889c50..aad42e89b 100644
--- a/test/pyxtest/proto/xi.py
+++ b/test/pyxtest/proto/xi.py
@@ -5,6 +5,9 @@
 import struct
 from dataclasses import dataclass
 
+# XI (v1) minor opcodes
+XChangeDeviceControl = 35
+
 # XI2 minor opcodes
 XIQueryVersion = 47
 XIPassiveGrabDevice = 54
@@ -43,6 +46,13 @@ PropModeAppend = 2
 VirtualCorePointer = 2
 VirtualCoreKeyboard = 3
 
+# Device control types (for XChangeDeviceControl)
+DEVICE_RESOLUTION = 1
+DEVICE_ABS_CALIB = 2
+DEVICE_ABS_AREA = 3
+DEVICE_CORE = 4
+DEVICE_ENABLE = 5
+
 
 @dataclass
 class XIQueryVersionRequest:
@@ -225,3 +235,64 @@ class XIGetPropertyRequest:
             self.offset,
             self.length,
         )
+
+
+@dataclass
+class XChangeDeviceControlRequest:
+    """XChangeDeviceControl request (XI v1, minor opcode 35).
+
+    The request header is 8 bytes (xChangeDeviceControlReq), followed by
+    a device control structure that depends on the control type.
+    For DEVICE_RESOLUTION, the control is xDeviceResolutionCtl (12 bytes)
+    followed by num_valuators CARD32 values.
+    """
+
+    opcode: int
+    control: int
+    deviceid: int
+    control_data: bytes = b""
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        total = 8 + len(self.control_data)
+        pad_len = (4 - total % 4) % 4
+        length = (total + pad_len) // 4
+
+        header = struct.pack(
+            f"{byte_order}BBH HBx",
+            self.opcode,
+            XChangeDeviceControl,
+            length,
+            self.control,
+            self.deviceid,
+        )
+        return header + self.control_data + b"\x00" * pad_len
+
+
+@dataclass
+class DeviceResolutionCtl:
+    """xDeviceResolutionCtl structure (8 bytes + valuator values).
+
+    control(2) + length(2) + first_valuator(1) + num_valuators(1) + pad(2)
+    followed by num_valuators CARD32 resolution values.
+    """
+
+    first_valuator: int = 0
+    num_valuators: int = 0
+    resolutions: list[int] | None = None
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        vals = self.resolutions if self.resolutions is not None else []
+        val_data = b""
+        for v in vals:
+            val_data += struct.pack(f"{byte_order}I", v)
+
+        ctl_length = (8 + len(val_data)) // 4
+
+        header = struct.pack(
+            f"{byte_order}HH BB xx",
+            DEVICE_RESOLUTION,
+            ctl_length,
+            self.first_valuator,
+            self.num_valuators,
+        )
+        return header + val_data
diff --git a/test/pyxtest/proto/xinerama.py b/test/pyxtest/proto/xinerama.py
new file mode 100644
index 000000000..694d96797
--- /dev/null
+++ b/test/pyxtest/proto/xinerama.py
@@ -0,0 +1,102 @@
+# SPDX-License-Identifier: MIT
+#
+# Xinerama (PanoramiX / pseudoramiX) extension protocol request builders
+# for byteswap testing.
+
+import struct
+from dataclasses import dataclass
+
+# Xinerama minor opcodes
+PanoramiXQueryVersion = 0
+PanoramiXGetState = 1
+PanoramiXGetScreenCount = 2
+PanoramiXGetScreenSize = 3
+XineramaIsActive = 4
+XineramaQueryScreens = 5
+
+
+@dataclass
+class QueryVersionRequest:
+    """PanoramiXQueryVersion request."""
+
+    opcode: int
+    major: int = 1
+    minor: int = 1
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHBB xx",
+            self.opcode,
+            PanoramiXQueryVersion,
+            2,
+            self.major,
+            self.minor,
+        )
+
+
+@dataclass
+class GetStateRequest:
+    """PanoramiXGetState request."""
+
+    opcode: int
+    window: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH I",
+            self.opcode,
+            PanoramiXGetState,
+            2,
+            self.window,
+        )
+
+
+@dataclass
+class GetScreenCountRequest:
+    """PanoramiXGetScreenCount request."""
+
+    opcode: int
+    window: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH I",
+            self.opcode,
+            PanoramiXGetScreenCount,
+            2,
+            self.window,
+        )
+
+
+@dataclass
+class GetScreenSizeRequest:
+    """PanoramiXGetScreenSize request."""
+
+    opcode: int
+    window: int
+    screen: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH II",
+            self.opcode,
+            PanoramiXGetScreenSize,
+            3,
+            self.window,
+            self.screen,
+        )
+
+
+@dataclass
+class IsActiveRequest:
+    """XineramaIsActive request."""
+
+    opcode: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH",
+            self.opcode,
+            XineramaIsActive,
+            1,
+        )
diff --git a/test/pyxtest/proto/xres.py b/test/pyxtest/proto/xres.py
new file mode 100644
index 000000000..8cd1a2d94
--- /dev/null
+++ b/test/pyxtest/proto/xres.py
@@ -0,0 +1,85 @@
+# SPDX-License-Identifier: MIT
+#
+# X-Resource extension protocol request builders for byteswap testing.
+
+import struct
+from dataclasses import dataclass, field
+
+# XRes minor opcodes
+XResQueryVersion = 0
+XResQueryClients = 1
+XResQueryClientResources = 2
+XResQueryClientPixmapBytes = 3
+XResQueryClientIds = 4
+XResQueryResourceBytes = 5
+
+
+@dataclass
+class QueryVersionRequest:
+    """XResQueryVersion request."""
+
+    opcode: int
+    major: int = 1
+    minor: int = 2
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBHBB xx",
+            self.opcode,
+            XResQueryVersion,
+            2,
+            self.major,
+            self.minor,
+        )
+
+
+@dataclass
+class QueryClientsRequest:
+    """XResQueryClients request."""
+
+    opcode: int
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        return struct.pack(
+            f"{byte_order}BBH",
+            self.opcode,
+            XResQueryClients,
+            1,
+        )
+
+
+@dataclass
+class QueryClientIdsRequest:
+    """XResQueryClientIds request.
+
+    Followed by numSpecs xXResClientIdSpec entries (8 bytes each:
+    client CARD32 + mask CARD32).
+    """
+
+    opcode: int
+    specs: list[tuple[int, int]] = field(default_factory=list)  # (client, mask) pairs
+    num_specs_override: int | None = None
+
+    def to_bytes(self, byte_order: str = "<") -> bytes:
+        num_specs = (
+            self.num_specs_override
+            if self.num_specs_override is not None
+            else len(self.specs)
+        )
+
+        spec_data = b""
+        for client, mask in self.specs:
+            spec_data += struct.pack(f"{byte_order}II", client, mask)
+
+        total = 8 + len(spec_data)
+        pad_len = (4 - total % 4) % 4
+        length = (total + pad_len) // 4
+
+        header = struct.pack(
+            f"{byte_order}BBH I",
+            self.opcode,
+            XResQueryClientIds,
+            length,
+            num_specs,
+        )
+        return header + spec_data + b"\x00" * pad_len
diff --git a/test/pyxtest/test_present.py b/test/pyxtest/test_present.py
new file mode 100644
index 000000000..2c274c11f
--- /dev/null
+++ b/test/pyxtest/test_present.py
@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: MIT
+#
+# Tests for Present extension.
+
+import pytest
+
+from proto import present
+from xclient import Extension, X11Error
+
+
+class TestPresentSelectInput:
+    @pytest.mark.swapped_client
+    def test_present_select_input_eid_swapped(self, xserver, xclient_swapped):
+        """
+        sproc_present_select_input was missing swapl(&stuff->eid).
+        Without the swap, the eid fails LEGAL_NEW_RESOURCE because
+        the client-bits portion of the garbled XID doesn't match
+        clientAsMask → BadIDChoice error.
+
+        Fixed in commit a5ac3c871219 ("present: add missing byte
+        swapping for various fields").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.PRESENT)
+        if not ext:
+            pytest.skip("Present extension not available")
+
+        req = present.QueryVersionRequest(opcode=ext.opcode)
+        conn.send_request(req.to_bytes(">"))
+        conn.recv_response(timeout=5.0)
+
+        win = conn.create_window()
+        eid = conn.alloc_id()
+
+        # Use a non-zero event_mask so the server reaches
+        # LEGAL_NEW_RESOURCE(eid).  With event_mask=0 the server
+        # returns Success immediately without validating the eid.
+        PresentConfigureNotifyMask = 1
+        req = present.SelectInputRequest(
+            opcode=ext.opcode,
+            eid=eid,
+            window=win,
+            event_mask=PresentConfigureNotifyMask,
+        )
+        conn.send_request(req.to_bytes(">"))
+        responses = conn.flush_responses(timeout=1.0)
+
+        assert xserver.is_alive, "Server crashed"
+
+        # With the fix: no error (void request succeeds silently).
+        # Without the fix: BadIDChoice error.
+        errors = [r for r in responses if isinstance(r, X11Error)]
+        assert len(errors) == 0, (
+            f"PresentSelectInput returned error(s): {errors} - "
+            "eid not swapped → BadIDChoice"
+        )
diff --git a/test/pyxtest/test_randr.py b/test/pyxtest/test_randr.py
index 86c318999..00a21a598 100644
--- a/test/pyxtest/test_randr.py
+++ b/test/pyxtest/test_randr.py
@@ -45,6 +45,20 @@ def randr_xclient(xclient):
     return xclient, ext.opcode, output_id
 
 
+@pytest.fixture
+def randr_xclient_swapped(xclient_swapped):
+    """Provide a byte-swapped xclient with RandR initialized."""
+    ext = xclient_swapped.query_extension(Extension.RANDR)
+    if not ext:
+        pytest.skip("RANDR extension not available")
+
+    req = randr.QueryVersionRequest(opcode=ext.opcode)
+    xclient_swapped.send_request(req.to_bytes(">"))
+    xclient_swapped.recv_response(timeout=5.0)
+
+    return xclient_swapped, ext.opcode
+
+
 class TestRandROutputProperty:
     """Tests for RRChangeOutputProperty vulnerabilities."""
 
@@ -169,3 +183,128 @@ class TestRandROutputProperty:
             f"Expected BadLength (16), got error code {resp.error_code} - "
             f"integer truncation not caught by length check"
         )
+
+
+class TestRandRSetScreenConfig:
+    @pytest.mark.swapped_client
+    def test_set_screen_config_config_timestamp_swapped(
+        self, xserver, randr_xclient_swapped
+    ):
+        """
+        SProcRRSetScreenConfig was missing swapl(&stuff->configTimestamp).
+
+        First query the server's configTimestamp via GetScreenResources,
+        then send it back in SetScreenConfig.  Without the fix, the
+        unswapped configTimestamp won't match → the reply has
+        status=RRSetConfigInvalidConfigTime (1) instead of
+        RRSetConfigSuccess (0).
+
+        Fixed in commit ac45f9b29e3a ("randr: add missing byte swapping
+        for various fields").
+        """
+        conn, opcode = randr_xclient_swapped
+
+        # Get screen resources to obtain the configTimestamp
+        req = randr.GetScreenResourcesCurrentRequest(
+            opcode=opcode,
+            window=conn.root_window,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+        assert len(resp.data) >= 32, "Reply too short"
+
+        # xRRGetScreenResourcesReply:
+        #   [8]  timestamp(4)
+        #   [12] configTimestamp(4)
+        config_ts = struct.unpack_from(">I", resp.data, 12)[0]
+
+        req = randr.SetScreenConfigRequest(
+            opcode=opcode,
+            drawable=conn.root_window,
+            timestamp=0,  # CurrentTime
+            config_timestamp=config_ts,
+            size_id=0,
+            rotation=1,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        # xRRSetScreenConfigReply:
+        #   [1] status
+        # RRSetConfigSuccess = 0
+        # RRSetConfigInvalidConfigTime = 1
+        # RRSetConfigInvalidTime = 2
+        # RRSetConfigFailed = 3
+        #
+        # Without the fix, the unswapped configTimestamp fails
+        # the equality check → status 1 (RRSetConfigInvalidConfigTime).
+        status = resp.data[1]
+        assert status != 1, (
+            "SetScreenConfig status = 1 "
+            "(RRSetConfigInvalidConfigTime) - configTimestamp "
+            "was not byte-swapped correctly."
+        )
+
+
+class TestRandRCreateLease:
+    @pytest.mark.swapped_client
+    def test_create_lease_lid_swapped(self, xserver, randr_xclient_swapped):
+        """
+        SProcRRCreateLease was missing swapl(&stuff->lid).
+        Without the swap, the garbled lid fails LEGAL_NEW_RESOURCE
+        → BadIDChoice error (error code 14).
+
+        With the fix, the request should succeed far enough to reach
+        the crtc/output validation (possibly returning BadValue for
+        the empty lists, but NOT BadIDChoice).
+
+        Fixed in commit ac45f9b29e3a ("randr: add missing byte swapping
+        for various fields").
+        """
+        conn, opcode = randr_xclient_swapped
+
+        lid = conn.alloc_id()
+
+        # Get screen resources to find a crtc and output
+        req = randr.GetScreenResourcesCurrentRequest(
+            opcode=opcode,
+            window=conn.root_window,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        n_crtcs = struct.unpack_from(">H", resp.data, 16)[0]
+        n_outputs = struct.unpack_from(">H", resp.data, 18)[0]
+
+        crtcs = []
+        outputs = []
+        if n_crtcs > 0:
+            crtcs = [struct.unpack_from(">I", resp.data, 32)[0]]
+        if n_outputs > 0:
+            offset = 32 + n_crtcs * 4
+            outputs = [struct.unpack_from(">I", resp.data, offset)[0]]
+
+        req = randr.CreateLeaseRequest(
+            opcode=opcode,
+            window=conn.root_window,
+            lid=lid,
+            crtcs=crtcs,
+            outputs=outputs,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+
+        # Without the fix: BadIDChoice (error code 14).
+        # With the fix: either success or some other error.
+        if isinstance(resp, X11Error):
+            assert resp.error_code != 14, (
+                "CreateLease returned BadIDChoice (error 14) - lid not byte-swapped"
+            )
diff --git a/test/pyxtest/test_render.py b/test/pyxtest/test_render.py
new file mode 100644
index 000000000..766e1a7ff
--- /dev/null
+++ b/test/pyxtest/test_render.py
@@ -0,0 +1,113 @@
+# SPDX-License-Identifier: MIT
+#
+# Security tests for Render extension vulnerabilities.
+
+import struct
+
+import pytest
+
+from proto import render
+from xclient import Extension, X11Error, X11Reply
+
+
+@pytest.fixture
+def render_xclient_swapped(xclient_swapped):
+    """Provide a byte-swapped xclient with Render initialized."""
+    ext = xclient_swapped.query_extension(Extension.RENDER)
+    if not ext:
+        pytest.skip("RENDER extension not available")
+
+    req = render.QueryVersionRequest(opcode=ext.opcode)
+    xclient_swapped.send_request(req.to_bytes(">"))
+    xclient_swapped.recv_response(timeout=5.0)
+
+    return xclient_swapped, ext.opcode
+
+
+class TestRenderSetPictureFilter:
+    @pytest.mark.swapped_client
+    def test_set_picture_filter_convolution_params_swapped(
+        self, xserver, render_xclient_swapped
+    ):
+        """
+        SProcRenderSetPictureFilter was missing SwapLongs() for the
+        xFixed filter parameter values.
+
+        Set a 3x1 convolution filter with params [3.0, 1.0, 1.0, 1.0, 1.0]
+        (in xFixed: [0x00030000, 0x00010000, ...]).  Without the swap,
+        the server sees garbled width/height and rejects with BadMatch.
+        With the swap, it succeeds.
+
+        Fixed in commit c98273d0bc00 ("render: add missing byte-swap of
+        filter params in SProcRenderSetPictureFilter").
+        """
+        conn, opcode = render_xclient_swapped
+
+        # Get a PictFormat that matches the root depth.
+        # xRenderQueryPictFormatsReply header (32 bytes):
+        #   [8]  numFormats(4)
+        # followed by numFormats xPictFormInfo entries (28 bytes each):
+        #   [0] id(4)  [4] type(1)  [5] depth(1)  ...
+        req = render.QueryPictFormatsRequest(opcode=opcode)
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert isinstance(resp, X11Reply), "QueryPictFormats failed"
+        num_formats = struct.unpack_from(">I", resp.data, 8)[0]
+
+        format_id = 0
+        for i in range(num_formats):
+            off = 32 + i * 28
+            if off + 6 > len(resp.data):
+                break
+            fid = struct.unpack_from(">I", resp.data, off)[0]
+            fdepth = resp.data[off + 5]
+            if fdepth == conn.root_depth:
+                format_id = fid
+                break
+
+        if format_id == 0:
+            pytest.skip("No PictFormat matching root depth")
+
+        pix = conn.create_pixmap(width=10, height=10)
+        pic = conn.alloc_id()
+
+        req = render.CreatePictureRequest(
+            opcode=opcode,
+            picture_id=pic,
+            drawable=pix,
+            format_id=format_id,
+        )
+        conn.send_request(req.to_bytes(">"))
+        errors = conn.flush_responses(timeout=0.5)
+        create_errors = [r for r in errors if isinstance(r, X11Error)]
+        assert len(create_errors) == 0, f"CreatePicture failed: {create_errors}"
+
+        # Set convolution filter: 3x1 kernel with all weights = 1.0
+        # xFixed 3.0 = 0x00030000, xFixed 1.0 = 0x00010000
+        # params: [width=3, height=1, k0=1.0, k1=1.0, k2=1.0]
+        req = render.SetPictureFilterRequest(
+            opcode=opcode,
+            picture=pic,
+            filter_name="convolution",
+            params=[
+                0x00030000,
+                0x00010000,
+                0x00010000,
+                0x00010000,
+                0x00010000,
+            ],
+        )
+        conn.send_request(req.to_bytes(">"))
+        responses = conn.flush_responses(timeout=1.0)
+
+        assert xserver.is_alive, "Server crashed"
+
+        # With the fix: no error (filter set successfully).
+        # Without the fix: BadMatch because
+        # convolutionFilterValidateParams rejects the garbled params.
+        errors = [r for r in responses if isinstance(r, X11Error)]
+        assert len(errors) == 0, (
+            f"SetPictureFilter returned error(s): {errors} - "
+            "filter params not byte-swapped → BadMatch"
+        )
diff --git a/test/pyxtest/test_screensaver.py b/test/pyxtest/test_screensaver.py
index 2d10e4fd1..d08ab3757 100644
--- a/test/pyxtest/test_screensaver.py
+++ b/test/pyxtest/test_screensaver.py
@@ -7,7 +7,7 @@ import time
 import pytest
 
 from proto import screensaver
-from xclient import Extension, RawX11Connection, X11ConnectionError
+from xclient import Extension
 
 
 class TestScreenSaverSuspend:
@@ -15,7 +15,7 @@ class TestScreenSaverSuspend:
 
     @pytest.mark.swapped_client
     @pytest.mark.asan
-    def test_suspend_swap_before_size_check(self, xserver):
+    def test_suspend_swap_before_size_check(self, xserver, xclient_swapped):
         """
         CVE-2021-4010 / ZDI-CAN-14951: SProcScreenSaverSuspend() did
         swapl() on stuff->suspend before REQUEST_SIZE_MATCH, so a
@@ -26,29 +26,21 @@ class TestScreenSaverSuspend:
         Fixed in commit 6c4c53010772 ("Xext: Fix out of bounds access
         in SProcScreenSaverSuspend()").
         """
-        try:
-            conn = RawX11Connection(xserver.display_num, swapped=True)
-        except X11ConnectionError as e:
-            if "endian" in str(e).lower():
-                pytest.skip("Server does not accept big-endian clients")
-            raise
+        conn = xclient_swapped
 
-        try:
-            ext = conn.query_extension(Extension.MIT_SCREEN_SAVER)
-            if not ext:
-                pytest.skip("MIT-SCREEN-SAVER extension not available")
+        ext = conn.query_extension(Extension.MIT_SCREEN_SAVER)
+        if not ext:
+            pytest.skip("MIT-SCREEN-SAVER extension not available")
 
-            # Send a valid ScreenSaverSuspend (the fix ensures proper
-            # validation order: size check before swap).
-            req = screensaver.SuspendRequest(
-                opcode=ext.opcode,
-                suspend=1,
-            )
-            conn.send_request(req.to_bytes(">"))
-            time.sleep(0.5)
+        # Send a valid ScreenSaverSuspend (the fix ensures proper
+        # validation order: size check before swap).
+        req = screensaver.SuspendRequest(
+            opcode=ext.opcode,
+            suspend=1,
+        )
+        conn.send_request(req.to_bytes(">"))
+        time.sleep(0.5)
 
-            assert xserver.is_alive, (
-                "Server crashed - SProcScreenSaverSuspend (CVE-2021-4010)"
-            )
-        finally:
-            conn.close()
+        assert xserver.is_alive, (
+            "Server crashed - SProcScreenSaverSuspend (CVE-2021-4010)"
+        )
diff --git a/test/pyxtest/test_shm.py b/test/pyxtest/test_shm.py
new file mode 100644
index 000000000..732c3c745
--- /dev/null
+++ b/test/pyxtest/test_shm.py
@@ -0,0 +1,82 @@
+# SPDX-License-Identifier: MIT
+#
+# Tests for MIT-SHM extension.
+
+import struct
+
+import pytest
+
+from proto import shm
+from xclient import Extension, X11Reply
+
+
+class TestShmCreateSegment:
+    @pytest.mark.swapped_client
+    def test_create_segment_reply_sequence_swapped(self, xserver, xclient_swapped):
+        """
+        ProcShmCreateSegment was missing swaps(&rep.sequenceNumber) and
+        swapl(&rep.length) for byte-swapped clients.
+
+        Without the fix the sequence number in the reply is
+        byte-reversed.  We send the request and verify that the
+        reply's sequence number matches the expected value.
+
+        ShmCreateSegment requires SHM fd-passing (SHM 1.2+) and a
+        local connection (Unix socket).  The reply also carries an fd
+        via SCM_RIGHTS which our simple recv() silently drops — that's
+        fine, we only need to check the header fields.
+
+        Fixed in commit c49c150dcfb7 ("Xext/shm: add missing reply
+        byte-swap in ProcShmCreateSegment").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.MIT_SHM)
+        if not ext:
+            pytest.skip("MIT-SHM extension not available")
+
+        # Query SHM version
+        req = shm.QueryVersionRequest(opcode=ext.opcode)
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        if not isinstance(resp, X11Reply):
+            pytest.skip("SHM QueryVersion failed")
+
+        # Check for SHM 1.2+ (fd-passing / CreateSegment support)
+        # Reply: type(1) + sharedPixmaps(1) + seq(2) + length(4) +
+        #        majorVersion(2) + minorVersion(2) + ...
+        if len(resp.data) < 12:
+            pytest.skip("SHM QueryVersion reply too short")
+
+        major = struct.unpack_from(">H", resp.data, 8)[0]
+        minor = struct.unpack_from(">H", resp.data, 10)[0]
+        if major < 1 or (major == 1 and minor < 2):
+            pytest.skip(f"SHM {major}.{minor} does not support CreateSegment")
+
+        shmseg_id = conn.alloc_id()
+        seq = conn.send_request(
+            shm.CreateSegmentRequest(
+                opcode=ext.opcode,
+                shmseg=shmseg_id,
+                size=4096,
+                read_only=False,
+            ).to_bytes(">")
+        )
+
+        # Read the 32-byte reply header.  The fd arrives as
+        # ancillary data which plain recv() drops, but the data
+        # bytes still arrive on the stream.
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        # Verify the sequence number was swapped correctly.
+        reply_seq = struct.unpack_from(">H", resp.data, 2)[0]
+        assert reply_seq == (seq & 0xFFFF), (
+            f"Reply sequence = {reply_seq:#06x}, "
+            f"expected {seq & 0xFFFF:#06x}. "
+            f"sequenceNumber not byte-swapped in "
+            f"ProcShmCreateSegment reply."
+        )
diff --git a/test/pyxtest/test_vidmode.py b/test/pyxtest/test_vidmode.py
new file mode 100644
index 000000000..fa47163fb
--- /dev/null
+++ b/test/pyxtest/test_vidmode.py
@@ -0,0 +1,106 @@
+# SPDX-License-Identifier: MIT
+#
+# Tests for XFree86-VidModeExtension.
+
+import struct
+
+import pytest
+
+from proto import vidmode
+from xclient import Extension, X11Error, X11Reply
+
+
+class TestVidModeSwitchToMode:
+    @pytest.mark.swapped_client
+    @pytest.mark.xorg_only
+    def test_switch_to_mode_fields_swapped(self, xserver, xclient_swapped):
+        """
+        SProcVidModeSwitchToMode previously only swapped stuff->screen.
+        All mode-line fields (dotclock, hdisplay, …) were left in
+        wire byte order, so ProcVidModeSwitchToMode could never match
+        them against any existing mode → BadValue.
+
+        Strategy: query the current mode with GetModeLine, then send
+        the same timings back via SwitchToMode.  With the fix the
+        values match → success.  Without the fix the garbled timings
+        don't match anything → BadValue error.
+
+        Fixed in commit 751e631e1c99 ("Xext/vidmode: fix
+        SProcVidModeSwitchToMode swapping only screen field").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.XF86VIDMODE)
+        if not ext:
+            pytest.skip("XF86-VidModeExtension not available")
+
+        req = vidmode.QueryVersionRequest(opcode=ext.opcode)
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+        if not isinstance(resp, X11Reply):
+            pytest.skip("VidMode QueryVersion failed")
+
+        # Get the current mode line so we can echo it back.
+        # xXF86VidModeGetModeLineReply (v2, 52 bytes):
+        #   [8]  dotclock(4)
+        #   [12] hdisplay(2)  hsyncstart(2)
+        #   [16] hsyncend(2)  htotal(2)
+        #   [20] hskew(4)
+        #   [24] vdisplay(2)  vsyncstart(2)
+        #   [28] vsyncend(2)  vtotal(2)
+        #   [32] flags(4)
+        #   [36] privsize(4)
+        req = vidmode.GetModeLineRequest(
+            opcode=ext.opcode,
+            screen=0,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        if isinstance(resp, X11Error):
+            pytest.skip("GetModeLine not supported (VidMode not initialised?)")
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+        assert len(resp.data) >= 40, f"Reply too short: {len(resp.data)}"
+
+        dotclock = struct.unpack_from(">I", resp.data, 8)[0]
+        hdisplay = struct.unpack_from(">H", resp.data, 12)[0]
+        hsyncstart = struct.unpack_from(">H", resp.data, 14)[0]
+        hsyncend = struct.unpack_from(">H", resp.data, 16)[0]
+        htotal = struct.unpack_from(">H", resp.data, 18)[0]
+        hskew = struct.unpack_from(">I", resp.data, 20)[0]
+        vdisplay = struct.unpack_from(">H", resp.data, 24)[0]
+        vsyncstart = struct.unpack_from(">H", resp.data, 26)[0]
+        vsyncend = struct.unpack_from(">H", resp.data, 28)[0]
+        vtotal = struct.unpack_from(">H", resp.data, 30)[0]
+        flags = struct.unpack_from(">I", resp.data, 32)[0]
+
+        # Switch to the same mode — should succeed.
+        req = vidmode.SwitchToModeRequest(
+            opcode=ext.opcode,
+            screen=0,
+            dotclock=dotclock,
+            hdisplay=hdisplay,
+            hsyncstart=hsyncstart,
+            hsyncend=hsyncend,
+            htotal=htotal,
+            hskew=hskew,
+            vdisplay=vdisplay,
+            vsyncstart=vsyncstart,
+            vsyncend=vsyncend,
+            vtotal=vtotal,
+            flags=flags,
+            privsize=0,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=2.0)
+
+        assert xserver.is_alive, "Server crashed"
+        # With the fix: no response (void request, success).
+        # Without the fix: BadValue error because the garbled
+        # timing fields don't match any mode.
+        if resp is not None:
+            assert not isinstance(resp, X11Error), (
+                f"SwitchToMode returned error {resp} - "
+                f"mode-line fields not byte-swapped in "
+                f"SProcVidModeSwitchToMode"
+            )
diff --git a/test/pyxtest/test_xi.py b/test/pyxtest/test_xi.py
index 7c1a0d2c2..f3afa5446 100644
--- a/test/pyxtest/test_xi.py
+++ b/test/pyxtest/test_xi.py
@@ -236,3 +236,64 @@ class TestXIChangeProperty:
         assert values == (1, 2, 10, 20, 30), (
             f"Expected (1, 2, 10, 20, 30), got {values}"
         )
+
+
+class TestXIChangeDeviceControl:
+    @pytest.mark.swapped_client
+    @pytest.mark.xorg_only
+    def test_change_device_control_resolution_values_swapped(
+        self, xserver, xclient_swapped
+    ):
+        """
+        SProcXChangeDeviceControl did not byte-swap the resolution
+        values array for DEVICE_RESOLUTION.
+
+        Send a ChangeDeviceControl/DEVICE_RESOLUTION with a resolution
+        value that is valid in native byte order but out-of-range when
+        byte-reversed (e.g. 1000 = 0x000003E8 → 0xE8030000 reversed).
+
+        Without the fix: the garbled value exceeds max_resolution →
+        BadValue error.
+        With the fix: the correct value is in range → success reply
+        (or BadMatch if the device doesn't support it, but not BadValue).
+
+        Fixed in commit e24bd73e9d6f ("Xi: add missing byte-swap of
+        resolution values in SProcXChangeDeviceControl").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.XI)
+        if not ext:
+            pytest.skip("XInput extension not available")
+
+        req = xi.XIQueryVersionRequest(opcode=ext.opcode)
+        conn.send_request(req.to_bytes(">"))
+        conn.recv_response(timeout=5.0)
+
+        ctl = xi.DeviceResolutionCtl(
+            first_valuator=0,
+            num_valuators=1,
+            resolutions=[1000],
+        )
+        ctl_bytes = ctl.to_bytes(">")
+
+        req = xi.XChangeDeviceControlRequest(
+            opcode=ext.opcode,
+            control=xi.DEVICE_RESOLUTION,
+            deviceid=xi.VirtualCorePointer,
+            control_data=ctl_bytes,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=2.0)
+
+        assert xserver.is_alive, "Server crashed"
+
+        # Without the fix: BadValue (error code 2) because the
+        # byte-reversed resolution 0xE8030000 exceeds max_resolution.
+        # With the fix: either a reply (success) or BadMatch (device
+        # doesn't support resolution control), but NOT BadValue.
+        if isinstance(resp, X11Error):
+            assert resp.error_code != 2, (
+                "ChangeDeviceControl returned BadValue (error 2) - "
+                "resolution values not byte-swapped"
+            )
diff --git a/test/pyxtest/test_xinerama.py b/test/pyxtest/test_xinerama.py
new file mode 100644
index 000000000..db1af4054
--- /dev/null
+++ b/test/pyxtest/test_xinerama.py
@@ -0,0 +1,100 @@
+# SPDX-License-Identifier: MIT
+#
+# Tests for XINERAMA (PanoramiX / pseudoramiX) extension.
+
+import pytest
+
+from proto import xinerama
+from xclient import Extension, X11Reply
+
+
+class TestPseudoramiXGetState:
+    @pytest.mark.swapped_client
+    def test_xinerama_get_state_window_swapped(self, xserver, xclient_swapped):
+        """
+        SProcPseudoramiXGetState was missing swapl(&stuff->window).
+        Without it, dixLookupWindow fails → BadWindow error.
+
+        Fixed in commit 6c51a0f9053c ("pseudoramiX: add missing byte
+        swapping in various fields").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.XINERAMA)
+        if not ext:
+            pytest.skip("XINERAMA extension not available")
+
+        req = xinerama.GetStateRequest(
+            opcode=ext.opcode,
+            window=conn.root_window,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), (
+            f"Expected reply from GetState, got {resp} - "
+            "window field not swapped → BadWindow"
+        )
+
+
+class TestPseudoramiXGetScreenCount:
+    @pytest.mark.swapped_client
+    def test_xinerama_get_screen_count_window_swapped(self, xserver, xclient_swapped):
+        """
+        SProcPseudoramiXGetScreenCount was missing swapl(&stuff->window).
+        Without it, dixLookupWindow fails → BadWindow error.
+
+        Fixed in commit 6c51a0f9053c ("pseudoramiX: add missing byte
+        swapping in various fields").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.XINERAMA)
+        if not ext:
+            pytest.skip("XINERAMA extension not available")
+
+        req = xinerama.GetScreenCountRequest(
+            opcode=ext.opcode,
+            window=conn.root_window,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), (
+            f"Expected reply from GetScreenCount, got {resp} - "
+            "window field not swapped → BadWindow"
+        )
+
+
+class TestPseudoramiXGetScreenSize:
+    @pytest.mark.swapped_client
+    def test_xinerama_get_screen_size_fields_swapped(self, xserver, xclient_swapped):
+        """
+        SProcPseudoramiXGetScreenSize was missing swapl(&stuff->window)
+        and swapl(&stuff->screen).  Without window swap,
+        dixLookupWindow fails → BadWindow error.
+
+        Fixed in commit 6c51a0f9053c ("pseudoramiX: add missing byte
+        swapping in various fields").
+        """
+        conn = xclient_swapped
+
+        ext = conn.query_extension(Extension.XINERAMA)
+        if not ext:
+            pytest.skip("XINERAMA extension not available")
+
+        req = xinerama.GetScreenSizeRequest(
+            opcode=ext.opcode,
+            window=conn.root_window,
+            screen=0,
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), (
+            f"Expected reply from GetScreenSize, got {resp} - "
+            "window/screen fields not swapped"
+        )
diff --git a/test/pyxtest/test_xres.py b/test/pyxtest/test_xres.py
new file mode 100644
index 000000000..5b5fa8c6b
--- /dev/null
+++ b/test/pyxtest/test_xres.py
@@ -0,0 +1,139 @@
+# SPDX-License-Identifier: MIT
+#
+# Tests for X-Resource extension.
+
+import struct
+
+import pytest
+
+from proto import xres
+from xclient import Extension, X11Reply
+
+
+@pytest.fixture
+def xres_xclient_swapped(xclient_swapped):
+    """Provide a byte-swapped xclient with X-Resource initialized."""
+    ext = xclient_swapped.query_extension(Extension.XRES)
+    if not ext:
+        pytest.skip("X-Resource extension not available")
+
+    req = xres.QueryVersionRequest(opcode=ext.opcode)
+    xclient_swapped.send_request(req.to_bytes(">"))
+    resp = xclient_swapped.recv_response(timeout=5.0)
+    if not isinstance(resp, X11Reply):
+        pytest.skip("XRes QueryVersion failed")
+
+    return xclient_swapped, ext.opcode
+
+
+class TestXResQueryClientIds:
+    @pytest.mark.swapped_client
+    def test_query_client_ids_spec_entries_swapped(self, xserver, xres_xclient_swapped):
+        """
+        SProcXResQueryClientIds was missing byte-swaps for the
+        xXResClientIdSpec entries.  Without the swaps, the mask field
+        (e.g. XResClientXIDMask=1) is seen as 0x01000000, which
+        doesn't match any known mask → the reply contains zero results.
+
+        With the fix, the reply should contain at least one result.
+
+        Fixed in commit f7b574931544 ("Xext/xres: add missing byte-swap
+        of spec entries in SProcXResQueryClientIds").
+        """
+        conn, opcode = xres_xclient_swapped
+
+        # X_XResClientXIDMask = 1.
+        # client=0 means "all clients" (the wildcard).
+        req = xres.QueryClientIdsRequest(
+            opcode=opcode,
+            specs=[(0, 1)],  # mask=1 (XResClientXIDMask)
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert xserver.is_alive, "Server crashed"
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        # xXResQueryClientIdsReply:
+        #   [8] numIds(4)
+        num_ids = struct.unpack_from(">I", resp.data, 8)[0]
+        assert num_ids > 0, (
+            "QueryClientIds returned numIds=0, expected >0. "
+            "The spec entry mask was not byte-swapped, so the "
+            "server didn't recognize XResClientXIDMask."
+        )
+
+    @pytest.mark.swapped_client
+    def test_construct_client_id_value_swap_check(
+        self, xserver, xres_xclient_swapped, xclient
+    ):
+        """
+        ConstructClientIdValue used client->swapped instead of
+        sendClient->swapped.  When a big-endian client queries
+        a native client's ID, the spec.client field in the reply
+        is not swapped → garbled value.
+
+        We create an additional native (little-endian) connection.
+        The big-endian connection queries the native client's XID.
+        With the fix, the returned spec.client should match the
+        native client's resource base.  Without the fix, it's
+        byte-swapped garbage.
+
+        Fixed in commit d2d4fb35e798 ("Xext/xres: fix wrong swap
+        check").
+        """
+        conn, opcode = xres_xclient_swapped
+        conn_native = xclient
+
+        # Get the list of clients
+        req = xres.QueryClientsRequest(opcode=opcode)
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        num_clients = struct.unpack_from(">I", resp.data, 8)[0]
+        assert num_clients >= 2, f"Expected at least 2 clients, got {num_clients}"
+
+        # Collect all client XIDs from the reply.
+        # Each xXResClient is 8 bytes: resource_base(4) + resource_mask(4)
+        client_xids = []
+        for i in range(num_clients):
+            offset = 32 + i * 8
+            if offset + 4 <= len(resp.data):
+                xid = struct.unpack_from(">I", resp.data, offset)[0]
+                client_xids.append(xid)
+
+        # Find the native client's resource base
+        native_base = conn_native._resource_id_base
+        target_xid = None
+        for xid in client_xids:
+            if (xid & 0xFFE00000) == (native_base & 0xFFE00000):
+                target_xid = xid
+                break
+
+        if target_xid is None:
+            pytest.skip("Could not find native client in XRes client list")
+
+        # Query the native client's XID using XResClientXIDMask
+        req = xres.QueryClientIdsRequest(
+            opcode=opcode,
+            specs=[(target_xid, 1)],  # XResClientXIDMask
+        )
+        conn.send_request(req.to_bytes(">"))
+        resp = conn.recv_response(timeout=5.0)
+
+        assert isinstance(resp, X11Reply), f"Expected reply, got {resp}"
+
+        num_ids = struct.unpack_from(">I", resp.data, 8)[0]
+        assert num_ids > 0, f"Expected >0 IDs, got {num_ids}"
+
+        # xXResClientIdValue:
+        #   spec.client(4) + spec.mask(4) + length(4) + value(4*length)
+        spec_client = struct.unpack_from(">I", resp.data, 32)[0]
+
+        assert spec_client == target_xid, (
+            f"spec.client = {spec_client:#010x}, "
+            f"expected {target_xid:#010x}. "
+            f"The swap check used client->swapped instead of "
+            f"sendClient->swapped."
+        )