diff --git a/AGENTS.md b/AGENTS.md
index 7098007f5..8a5254889 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -22,6 +22,8 @@ A file for [guiding coding agents](https://agents.md/).
 - Build WASM: `zig build -Demit-lib-vt -Dtarget=wasm32-freestanding -Doptimize=ReleaseSmall`
 - Test: `zig build test-lib-vt -Dtest-filter=<filter>`
   - Prefer this when the change is in a libghostty-vt file
+- All C enums in `include/ghostty/vt/` must have a `_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE`
+  sentinel as the last entry to force int enum sizing (pre-C23 portability).
 
 ## Directory Structure
 
diff --git a/include/ghostty/vt/build_info.h b/include/ghostty/vt/build_info.h
index 19999e77f..d0aedfdc1 100644
--- a/include/ghostty/vt/build_info.h
+++ b/include/ghostty/vt/build_info.h
@@ -40,6 +40,7 @@ typedef enum {
   GHOSTTY_OPTIMIZE_RELEASE_SAFE = 1,
   GHOSTTY_OPTIMIZE_RELEASE_SMALL = 2,
   GHOSTTY_OPTIMIZE_RELEASE_FAST = 3,
+  GHOSTTY_OPTIMIZE_MODE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyOptimizeMode;
 
 /**
@@ -122,6 +123,7 @@ typedef enum {
    * Output type: GhosttyString *
    */
   GHOSTTY_BUILD_INFO_VERSION_BUILD = 10,
+  GHOSTTY_BUILD_INFO_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyBuildInfo;
 
 /**
diff --git a/include/ghostty/vt/device.h b/include/ghostty/vt/device.h
index fdf6bca7d..3b6ba3d7c 100644
--- a/include/ghostty/vt/device.h
+++ b/include/ghostty/vt/device.h
@@ -74,6 +74,7 @@ extern "C" {
 typedef enum {
     GHOSTTY_COLOR_SCHEME_LIGHT = 0,
     GHOSTTY_COLOR_SCHEME_DARK = 1,
+    GHOSTTY_COLOR_SCHEME_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyColorScheme;
 
 /**
diff --git a/include/ghostty/vt/focus.h b/include/ghostty/vt/focus.h
index 6e4c9502c..2f4954965 100644
--- a/include/ghostty/vt/focus.h
+++ b/include/ghostty/vt/focus.h
@@ -40,6 +40,7 @@ typedef enum {
     GHOSTTY_FOCUS_GAINED = 0,
     /** Terminal window lost focus */
     GHOSTTY_FOCUS_LOST = 1,
+    GHOSTTY_FOCUS_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyFocusEvent;
 
 /**
diff --git a/include/ghostty/vt/formatter.h b/include/ghostty/vt/formatter.h
index 9eacc6409..f0fc1447d 100644
--- a/include/ghostty/vt/formatter.h
+++ b/include/ghostty/vt/formatter.h
@@ -46,6 +46,7 @@ typedef enum {
 
   /** HTML with inline styles. */
   GHOSTTY_FORMATTER_FORMAT_HTML,
+  GHOSTTY_FORMATTER_FORMAT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyFormatterFormat;
 
 /**
diff --git a/include/ghostty/vt/key/encoder.h b/include/ghostty/vt/key/encoder.h
index 9d8282cec..5d1200741 100644
--- a/include/ghostty/vt/key/encoder.h
+++ b/include/ghostty/vt/key/encoder.h
@@ -73,6 +73,7 @@ typedef enum {
     GHOSTTY_OPTION_AS_ALT_LEFT = 2,
     /** Only right option key is treated as alt */
     GHOSTTY_OPTION_AS_ALT_RIGHT = 3,
+    GHOSTTY_OPTION_AS_ALT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyOptionAsAlt;
 
 /**
@@ -104,6 +105,7 @@ typedef enum {
     
     /** macOS option-as-alt setting (value: GhosttyOptionAsAlt) */
     GHOSTTY_KEY_ENCODER_OPT_MACOS_OPTION_AS_ALT = 6,
+    GHOSTTY_KEY_ENCODER_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKeyEncoderOption;
 
 /**
diff --git a/include/ghostty/vt/key/event.h b/include/ghostty/vt/key/event.h
index bcc9d8dec..39f23d7e4 100644
--- a/include/ghostty/vt/key/event.h
+++ b/include/ghostty/vt/key/event.h
@@ -35,6 +35,7 @@ typedef enum {
     GHOSTTY_KEY_ACTION_PRESS = 1,
     /** Key is being repeated (held down) */
     GHOSTTY_KEY_ACTION_REPEAT = 2,
+    GHOSTTY_KEY_ACTION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKeyAction;
 
 /**
@@ -296,6 +297,7 @@ typedef enum {
     GHOSTTY_KEY_COPY,
     GHOSTTY_KEY_CUT,
     GHOSTTY_KEY_PASTE,
+    GHOSTTY_KEY_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKey;
 
 /**
diff --git a/include/ghostty/vt/kitty_graphics.h b/include/ghostty/vt/kitty_graphics.h
index 1f6884348..b9ea64eb3 100644
--- a/include/ghostty/vt/kitty_graphics.h
+++ b/include/ghostty/vt/kitty_graphics.h
@@ -119,6 +119,7 @@ typedef enum {
    * Output type: GhosttyKittyGraphicsPlacementIterator *
    */
   GHOSTTY_KITTY_GRAPHICS_DATA_PLACEMENT_ITERATOR = 1,
+  GHOSTTY_KITTY_GRAPHICS_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyGraphicsData;
 
 /**
@@ -213,6 +214,7 @@ typedef enum {
    * Output type: int32_t *
    */
   GHOSTTY_KITTY_GRAPHICS_PLACEMENT_DATA_Z = 12,
+  GHOSTTY_KITTY_GRAPHICS_PLACEMENT_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyGraphicsPlacementData;
 
 /**
@@ -231,6 +233,7 @@ typedef enum {
   GHOSTTY_KITTY_PLACEMENT_LAYER_BELOW_BG = 1,
   GHOSTTY_KITTY_PLACEMENT_LAYER_BELOW_TEXT = 2,
   GHOSTTY_KITTY_PLACEMENT_LAYER_ABOVE_TEXT = 3,
+  GHOSTTY_KITTY_PLACEMENT_LAYER_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyPlacementLayer;
 
 /**
@@ -245,6 +248,7 @@ typedef enum {
    * Input type: GhosttyKittyPlacementLayer *
    */
   GHOSTTY_KITTY_GRAPHICS_PLACEMENT_ITERATOR_OPTION_LAYER = 0,
+  GHOSTTY_KITTY_GRAPHICS_PLACEMENT_ITERATOR_OPTION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyGraphicsPlacementIteratorOption;
 
 /**
@@ -258,6 +262,7 @@ typedef enum {
   GHOSTTY_KITTY_IMAGE_FORMAT_PNG = 2,
   GHOSTTY_KITTY_IMAGE_FORMAT_GRAY_ALPHA = 3,
   GHOSTTY_KITTY_IMAGE_FORMAT_GRAY = 4,
+  GHOSTTY_KITTY_IMAGE_FORMAT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyImageFormat;
 
 /**
@@ -268,6 +273,7 @@ typedef enum {
 typedef enum {
   GHOSTTY_KITTY_IMAGE_COMPRESSION_NONE = 0,
   GHOSTTY_KITTY_IMAGE_COMPRESSION_ZLIB_DEFLATE = 1,
+  GHOSTTY_KITTY_IMAGE_COMPRESSION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyImageCompression;
 
 /**
@@ -335,6 +341,7 @@ typedef enum {
    * Output type: size_t *
    */
   GHOSTTY_KITTY_IMAGE_DATA_DATA_LEN = 8,
+  GHOSTTY_KITTY_IMAGE_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyKittyGraphicsImageData;
 
 /**
diff --git a/include/ghostty/vt/modes.h b/include/ghostty/vt/modes.h
index 513aaf5a5..f8fa7c009 100644
--- a/include/ghostty/vt/modes.h
+++ b/include/ghostty/vt/modes.h
@@ -157,6 +157,7 @@ typedef enum {
     GHOSTTY_MODE_REPORT_PERMANENTLY_SET = 3,
     /** Mode is permanently reset */
     GHOSTTY_MODE_REPORT_PERMANENTLY_RESET = 4,
+    GHOSTTY_MODE_REPORT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyModeReportState;
 
 /**
diff --git a/include/ghostty/vt/mouse/encoder.h b/include/ghostty/vt/mouse/encoder.h
index 744b99303..a82dda089 100644
--- a/include/ghostty/vt/mouse/encoder.h
+++ b/include/ghostty/vt/mouse/encoder.h
@@ -45,6 +45,7 @@ typedef enum {
 
   /** Any-event tracking mode. */
   GHOSTTY_MOUSE_TRACKING_ANY = 4,
+  GHOSTTY_MOUSE_TRACKING_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyMouseTrackingMode;
 
 /**
@@ -58,6 +59,7 @@ typedef enum {
   GHOSTTY_MOUSE_FORMAT_SGR = 2,
   GHOSTTY_MOUSE_FORMAT_URXVT = 3,
   GHOSTTY_MOUSE_FORMAT_SGR_PIXELS = 4,
+  GHOSTTY_MOUSE_FORMAT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyMouseFormat;
 
 /**
@@ -120,6 +122,7 @@ typedef enum {
 
   /** Whether to enable motion deduplication by last cell (value: bool). */
   GHOSTTY_MOUSE_ENCODER_OPT_TRACK_LAST_CELL = 4,
+  GHOSTTY_MOUSE_ENCODER_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyMouseEncoderOption;
 
 /**
diff --git a/include/ghostty/vt/mouse/event.h b/include/ghostty/vt/mouse/event.h
index 5b72735fc..ac71881f2 100644
--- a/include/ghostty/vt/mouse/event.h
+++ b/include/ghostty/vt/mouse/event.h
@@ -36,6 +36,7 @@ typedef enum {
 
   /** Mouse moved. */
   GHOSTTY_MOUSE_ACTION_MOTION = 2,
+  GHOSTTY_MOUSE_ACTION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyMouseAction;
 
 /**
@@ -56,6 +57,7 @@ typedef enum {
   GHOSTTY_MOUSE_BUTTON_NINE = 9,
   GHOSTTY_MOUSE_BUTTON_TEN = 10,
   GHOSTTY_MOUSE_BUTTON_ELEVEN = 11,
+  GHOSTTY_MOUSE_BUTTON_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyMouseButton;
 
 /**
diff --git a/include/ghostty/vt/osc.h b/include/ghostty/vt/osc.h
index e17a8a182..43d137061 100644
--- a/include/ghostty/vt/osc.h
+++ b/include/ghostty/vt/osc.h
@@ -63,6 +63,7 @@ typedef enum {
   GHOSTTY_OSC_COMMAND_CONEMU_XTERM_EMULATION = 20,
   GHOSTTY_OSC_COMMAND_CONEMU_COMMENT = 21,
   GHOSTTY_OSC_COMMAND_KITTY_TEXT_SIZING = 22,
+  GHOSTTY_OSC_COMMAND_TYPE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyOscCommandType;
 
 /**
@@ -88,6 +89,7 @@ typedef enum {
    * the same parser instance. Memory is owned by the parser.
    */
   GHOSTTY_OSC_DATA_CHANGE_WINDOW_TITLE_STR = 1,
+  GHOSTTY_OSC_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyOscCommandData;
 
 /**
diff --git a/include/ghostty/vt/point.h b/include/ghostty/vt/point.h
index f152a5c46..c1ade0f96 100644
--- a/include/ghostty/vt/point.h
+++ b/include/ghostty/vt/point.h
@@ -54,7 +54,8 @@ typedef enum {
 
   /** Scrollback history only (before active area). */
   GHOSTTY_POINT_TAG_HISTORY = 3,
-} GhosttyPointTag;
+  GHOSTTY_POINT_TAG_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+  } GhosttyPointTag;
 
 /**
  * Point value union.
diff --git a/include/ghostty/vt/render.h b/include/ghostty/vt/render.h
index b15be4902..759c9354c 100644
--- a/include/ghostty/vt/render.h
+++ b/include/ghostty/vt/render.h
@@ -95,6 +95,7 @@ typedef enum {
 
   /** Global state changed; renderer should redraw everything. */
   GHOSTTY_RENDER_STATE_DIRTY_FULL = 2,
+  GHOSTTY_RENDER_STATE_DIRTY_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateDirty;
 
 /**
@@ -114,6 +115,7 @@ typedef enum {
 
   /** Hollow block cursor. */
   GHOSTTY_RENDER_STATE_CURSOR_VISUAL_STYLE_BLOCK_HOLLOW = 3,
+  GHOSTTY_RENDER_STATE_CURSOR_VISUAL_STYLE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateCursorVisualStyle;
 
 /**
@@ -185,6 +187,7 @@ typedef enum {
   /** Whether the cursor is on the tail of a wide character (bool).
    *  Only valid when CURSOR_VIEWPORT_HAS_VALUE is true. */
   GHOSTTY_RENDER_STATE_DATA_CURSOR_VIEWPORT_WIDE_TAIL = 17,
+  GHOSTTY_RENDER_STATE_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateData;
 
 /**
@@ -195,6 +198,7 @@ typedef enum {
 typedef enum {
   /** Set dirty state (GhosttyRenderStateDirty). */
   GHOSTTY_RENDER_STATE_OPTION_DIRTY = 0,
+  GHOSTTY_RENDER_STATE_OPTION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateOption;
 
 /**
@@ -217,6 +221,7 @@ typedef enum {
    *  valid as long as the underlying render state is not updated. 
    *  It is unsafe to use cell data after updating the render state. */
   GHOSTTY_RENDER_STATE_ROW_DATA_CELLS = 3,
+  GHOSTTY_RENDER_STATE_ROW_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateRowData;
 
 /**
@@ -227,6 +232,7 @@ typedef enum {
 typedef enum {
   /** Set dirty state for the current row (bool). */
   GHOSTTY_RENDER_STATE_ROW_OPTION_DIRTY = 0,
+  GHOSTTY_RENDER_STATE_ROW_OPTION_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateRowOption;
 
 /**
@@ -509,6 +515,7 @@ typedef enum {
    *  color, in which case the caller should use whatever default foreground
    *  color it wants (e.g. the terminal foreground). */
   GHOSTTY_RENDER_STATE_ROW_CELLS_DATA_FG_COLOR = 6,
+  GHOSTTY_RENDER_STATE_ROW_CELLS_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRenderStateRowCellsData;
 
 /**
diff --git a/include/ghostty/vt/screen.h b/include/ghostty/vt/screen.h
index 89b4825fe..13bb8e43b 100644
--- a/include/ghostty/vt/screen.h
+++ b/include/ghostty/vt/screen.h
@@ -69,6 +69,7 @@ typedef enum {
 
   /** No text; background color as RGB. */
   GHOSTTY_CELL_CONTENT_BG_COLOR_RGB = 3,
+  GHOSTTY_CELL_CONTENT_TAG_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyCellContentTag;
 
 /**
@@ -90,6 +91,7 @@ typedef enum {
 
   /** Spacer at end of soft-wrapped line for a wide character. */
   GHOSTTY_CELL_WIDE_SPACER_HEAD = 3,
+  GHOSTTY_CELL_WIDE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyCellWide;
 
 /**
@@ -109,6 +111,7 @@ typedef enum {
 
   /** Content that is part of a shell prompt. */
   GHOSTTY_CELL_SEMANTIC_PROMPT = 2,
+  GHOSTTY_CELL_SEMANTIC_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyCellSemanticContent;
 
 /**
@@ -201,6 +204,7 @@ typedef enum {
    * Output type: GhosttyColorRgb *
    */
   GHOSTTY_CELL_DATA_COLOR_RGB = 11,
+  GHOSTTY_CELL_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyCellData;
 
 /**
@@ -220,6 +224,7 @@ typedef enum {
 
   /** Prompt cells exist and this is a continuation line. */
   GHOSTTY_ROW_SEMANTIC_PROMPT_CONTINUATION = 2,
+  GHOSTTY_ROW_SEMANTIC_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRowSemanticPrompt;
 
 /**
@@ -289,6 +294,7 @@ typedef enum {
    * Output type: bool *
    */
   GHOSTTY_ROW_DATA_DIRTY = 8,
+  GHOSTTY_ROW_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyRowData;
 
 /**
diff --git a/include/ghostty/vt/sgr.h b/include/ghostty/vt/sgr.h
index b093bc9ff..00849283d 100644
--- a/include/ghostty/vt/sgr.h
+++ b/include/ghostty/vt/sgr.h
@@ -87,6 +87,7 @@ typedef enum {
   GHOSTTY_SGR_ATTR_BRIGHT_FG_8 = 28,
   GHOSTTY_SGR_ATTR_BG_256 = 29,
   GHOSTTY_SGR_ATTR_FG_256 = 30,
+  GHOSTTY_SGR_ATTR_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttySgrAttributeTag;
 
 /**
@@ -101,6 +102,7 @@ typedef enum {
   GHOSTTY_SGR_UNDERLINE_CURLY = 3,
   GHOSTTY_SGR_UNDERLINE_DOTTED = 4,
   GHOSTTY_SGR_UNDERLINE_DASHED = 5,
+  GHOSTTY_SGR_UNDERLINE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttySgrUnderline;
 
 /**
diff --git a/include/ghostty/vt/size_report.h b/include/ghostty/vt/size_report.h
index 98c67c5ed..d65fa95f6 100644
--- a/include/ghostty/vt/size_report.h
+++ b/include/ghostty/vt/size_report.h
@@ -49,6 +49,7 @@ typedef enum {
     GHOSTTY_SIZE_REPORT_CSI_16_T = 2,
     /** XTWINOPS text area size in characters: ESC [ 8 ; rows ; cols t */
     GHOSTTY_SIZE_REPORT_CSI_18_T = 3,
+    GHOSTTY_SIZE_REPORT_STYLE_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttySizeReportStyle;
 
 /**
diff --git a/include/ghostty/vt/style.h b/include/ghostty/vt/style.h
index ac0495600..ea1750395 100644
--- a/include/ghostty/vt/style.h
+++ b/include/ghostty/vt/style.h
@@ -50,7 +50,8 @@ typedef enum {
   GHOSTTY_STYLE_COLOR_NONE = 0,
   GHOSTTY_STYLE_COLOR_PALETTE = 1,
   GHOSTTY_STYLE_COLOR_RGB = 2,
-} GhosttyStyleColorTag;
+  GHOSTTY_STYLE_COLOR_TAG_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
+  } GhosttyStyleColorTag;
 
 /**
  * Style color value union.
diff --git a/include/ghostty/vt/sys.h b/include/ghostty/vt/sys.h
index 0634f5ac8..56e60b237 100644
--- a/include/ghostty/vt/sys.h
+++ b/include/ghostty/vt/sys.h
@@ -106,6 +106,7 @@ typedef enum {
      * Input type: GhosttySysDecodePngFn (function pointer, or NULL)
      */
     GHOSTTY_SYS_OPT_DECODE_PNG = 1,
+    GHOSTTY_SYS_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttySysOption;
 
 /**
diff --git a/include/ghostty/vt/terminal.h b/include/ghostty/vt/terminal.h
index a229dd700..c57ba27b5 100644
--- a/include/ghostty/vt/terminal.h
+++ b/include/ghostty/vt/terminal.h
@@ -189,6 +189,7 @@ typedef enum {
 
   /** Scroll by a delta amount (up is negative). */
   GHOSTTY_SCROLL_VIEWPORT_DELTA,
+  GHOSTTY_SCROLL_VIEWPORT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalScrollViewportTag;
 
 /**
@@ -227,6 +228,7 @@ typedef enum {
 
   /** The alternate screen. */
   GHOSTTY_TERMINAL_SCREEN_ALTERNATE = 1,
+  GHOSTTY_TERMINAL_SCREEN_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalScreen;
 
 /**
@@ -571,6 +573,7 @@ typedef enum {
    * Input type: bool*
    */
   GHOSTTY_TERMINAL_OPT_KITTY_IMAGE_MEDIUM_SHARED_MEM = 18,
+  GHOSTTY_TERMINAL_OPT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalOption;
 
 /**
@@ -846,6 +849,7 @@ typedef enum {
    * Output type: GhosttyKittyGraphics *
    */
   GHOSTTY_TERMINAL_DATA_KITTY_GRAPHICS = 30,
+  GHOSTTY_TERMINAL_DATA_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyTerminalData;
 
 /**
diff --git a/include/ghostty/vt/types.h b/include/ghostty/vt/types.h
index 0fe37e3b2..70ac11d57 100644
--- a/include/ghostty/vt/types.h
+++ b/include/ghostty/vt/types.h
@@ -7,6 +7,7 @@
 #ifndef GHOSTTY_VT_TYPES_H
 #define GHOSTTY_VT_TYPES_H
 
+#include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ -32,6 +33,26 @@
 #endif
 #endif
 
+/**
+ * Sentinel value for enum definitions to force max int width sizing.
+ *
+ * Pre-C23, the C standard allows compilers to choose any integer type
+ * that can represent all enum values (C11 §6.7.2.2), so small enums
+ * could be backed by char or short. Adding this value as the last
+ * entry in every enum forces the compiler to use at an `int`
+ * type, ensuring ABI stability across compilers and platforms.
+ *
+ * We use INT_MAX rather than a fixed constant like 0xFFFFFFFF because
+ * enum constants must have type int (which is signed). Values above
+ * INT_MAX overflow signed int and are a constraint violation in
+ * standard C; compilers that accept them interpret them as negative
+ * values via two's complement, which can collide with legitimate
+ * negative enum values. Using INT_MAX also ensures the enum matches
+ * the target's int size, which is important because the Zig side
+ * backs these enums with c_int for ABI compatibility.
+ */
+#define GHOSTTY_ENUM_MAX_VALUE INT_MAX
+
 /**
  * Result codes for libghostty-vt operations.
  */
@@ -46,6 +67,7 @@ typedef enum {
     GHOSTTY_OUT_OF_SPACE = -3,
     /** The requested value has no value */
     GHOSTTY_NO_VALUE = -4,
+    GHOSTTY_RESULT_MAX_VALUE = GHOSTTY_ENUM_MAX_VALUE,
 } GhosttyResult;
 
 /* ---- Opaque handles ---- */