diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index a47e3304..b9870d64 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -139,7 +139,7 @@ cmake --build recompiler/build
 cd recompiler/build && ctest --output-on-failure
 ```
 
-37 tests, under five seconds, no BIOS dump or disc image required. See
+38 tests, under five seconds, no BIOS dump or disc image required. See
 [`docs/TESTING.md`](docs/TESTING.md) for running individual tests, what the
 suite covers, and the three known-failing tests that are deliberately not
 registered.
diff --git a/docs/BUILDING.md b/docs/BUILDING.md
index 7e2f2c28..1d09623b 100644
--- a/docs/BUILDING.md
+++ b/docs/BUILDING.md
@@ -135,7 +135,7 @@ After step 1 above — no BIOS or disc needed — verify the tree is sane:
 cd recompiler/build && ctest --output-on-failure
 ```
 
-37 tests, under five seconds. See [`TESTING.md`](TESTING.md).
+38 tests, under five seconds. See [`TESTING.md`](TESTING.md).
 
 On Windows with MSVC or plain MinGW makefiles, swap `-G Ninja` for your generator
 (e.g. `-G "Unix Makefiles"`); everything else is identical.
diff --git a/docs/TESTING.md b/docs/TESTING.md
index c8fb0be4..2fe84b13 100644
--- a/docs/TESTING.md
+++ b/docs/TESTING.md
@@ -8,7 +8,7 @@ cmake --build recompiler/build
 cd recompiler/build && ctest --output-on-failure
 ```
 
-That is the whole thing. 37 tests, under 5 seconds, and it needs **no BIOS dump,
+That is the whole thing. 38 tests, under 5 seconds, and it needs **no BIOS dump,
 no disc image, and no generated code** — a plain recompiler build is enough. This
 is the check to run before opening a PR.
 
diff --git a/recompiler/CMakeLists.txt b/recompiler/CMakeLists.txt
index e3fb993e..52202b0f 100644
--- a/recompiler/CMakeLists.txt
+++ b/recompiler/CMakeLists.txt
@@ -409,8 +409,9 @@ if(BUILD_TESTING)
                 mod_controller_override
                 overlay_candidate_capacity
                 overlay_decodable_fallback
-                overlay_init_guard
-                vk_build_default
+                overlay_init_guard
+                sdl3_main_single_include
+                vk_build_default
                 vk_color_self_barrier
                 vk_command_buffer_batching
                 vk_draw_area_batch_boundary
diff --git a/runtime/include/psx_sdl.h b/runtime/include/psx_sdl.h
index ef1ceb70..1749b46f 100644
--- a/runtime/include/psx_sdl.h
+++ b/runtime/include/psx_sdl.h
@@ -11,7 +11,6 @@
 #define SDL_ENABLE_OLD_NAMES
 #define SDL_FUNCTION_POINTER_IS_VOID_POINTER
 #include <SDL3/SDL.h>
-#include <SDL3/SDL_main.h>
 
 #ifndef SDL_WINDOW_SHOWN
 #define SDL_WINDOW_SHOWN 0
diff --git a/runtime/src/main.cpp b/runtime/src/main.cpp
index 181cddcc..23e39501 100644
--- a/runtime/src/main.cpp
+++ b/runtime/src/main.cpp
@@ -72,6 +72,14 @@ extern "C" void psx_event_step_conservative_env_init(void);
 #include "launcher_profile.h"  /* per-system variant profile (theme/caps bundle) */
 #endif
 #include "psx_sdl.h"
+#if defined(PSX_SDL3)
+/*
+ * SDL_main.h is a single-header implementation in SDL3. Keep it in the one
+ * translation unit that defines main(); including it through psx_sdl.h makes
+ * every SDL-using source emit WinMain under MinGW.
+ */
+#include <SDL3/SDL_main.h>
+#endif
 #include "psx_sdl_audio.h"
 #if defined(PSX_WEB)
 #include <emscripten/emscripten.h>
diff --git a/runtime/tests/test_sdl3_main_single_include.py b/runtime/tests/test_sdl3_main_single_include.py
new file mode 100644
index 00000000..71a4ad2b
--- /dev/null
+++ b/runtime/tests/test_sdl3_main_single_include.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+"""Keep SDL3's single-header entry-point implementation in main.cpp only."""
+
+from pathlib import Path
+import sys
+
+
+ROOT = Path(__file__).resolve().parents[2]
+SDL_MAIN_HEADER = "<SDL3/SDL_main.h>"
+
+
+def main() -> int:
+    runtime = ROOT / "runtime"
+    owners = []
+    for pattern in ("*.c", "*.cpp", "*.h"):
+        for path in runtime.rglob(pattern):
+            source = path.read_text(encoding="utf-8")
+            if SDL_MAIN_HEADER in source:
+                owners.append(path.relative_to(ROOT).as_posix())
+
+    if owners != ["runtime/src/main.cpp"]:
+        raise AssertionError(
+            "SDL_main.h must be included exactly once by runtime/src/main.cpp; "
+            f"found {owners}"
+        )
+
+    main_cpp = (runtime / "src/main.cpp").read_text(encoding="utf-8")
+    guard = (
+        "#if defined(PSX_SDL3)\n"
+        "/*\n"
+        " * SDL_main.h is a single-header implementation"
+    )
+    if guard not in main_cpp:
+        raise AssertionError("SDL_main.h include is no longer guarded by PSX_SDL3")
+
+    print("PASS: SDL3 entry-point implementation has one owner")
+    return 0
+
+
+if __name__ == "__main__":
+    try:
+        sys.exit(main())
+    except AssertionError as exc:
+        print(f"FAIL: {exc}")
+        sys.exit(1)