diff --git a/source/collada/CommonConvert.cpp b/source/collada/CommonConvert.cpp
index 3c74279b28..d641c436f3 100644
--- a/source/collada/CommonConvert.cpp
+++ b/source/collada/CommonConvert.cpp
@@ -32,7 +32,6 @@
 #include <FCollada.h>
 #include <FMath/FMVector3.h>
 #include <FUtils/FUString.h>
-#include <FUtils/FUtils.h>
 #include <algorithm>
 #include <cassert>
 #include <cstdarg>
diff --git a/source/collada/GeomReindex.cpp b/source/collada/GeomReindex.cpp
index 226dc6dbc9..e19b0e53f5 100644
--- a/source/collada/GeomReindex.cpp
+++ b/source/collada/GeomReindex.cpp
@@ -31,7 +31,6 @@
 #include <cassert>
 #include <cmath>
 #include <cstring>
-#include <iterator>
 #include <map>
 #include <utility>
 #include <vector>
diff --git a/source/collada/PSAConvert.cpp b/source/collada/PSAConvert.cpp
index 9a9e3f821b..efd0e3fd43 100644
--- a/source/collada/PSAConvert.cpp
+++ b/source/collada/PSAConvert.cpp
@@ -42,8 +42,8 @@
 #include <FUtils/Platforms.h>
 #include <algorithm>
 #include <cassert>
+#include <cfloat>
 #include <cstring>
-#include <float.h>
 #include <iterator>
 #include <limits>
 #include <vector>
diff --git a/source/collada/precompiled.h b/source/collada/precompiled.h
index 3b55b650bf..89c4cdd278 100644
--- a/source/collada/precompiled.h
+++ b/source/collada/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,8 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #ifndef INCLUDED_COLLADA_PRECOMPILED
 #define INCLUDED_COLLADA_PRECOMPILED
 
@@ -61,3 +63,5 @@ extern void Log(int severity, const char* fmt, ...);
 #undef max
 
 #endif // INCLUDED_COLLADA_PRECOMPILED
+
+// IWYU pragma: end_keep
diff --git a/source/graphics/CameraController.cpp b/source/graphics/CameraController.cpp
index 0d70b5e583..3ec5b4d258 100644
--- a/source/graphics/CameraController.cpp
+++ b/source/graphics/CameraController.cpp
@@ -40,7 +40,7 @@
 #include "simulation2/Simulation2.h"
 #include "simulation2/components/ICmpPosition.h"
 #include "simulation2/components/ICmpRangeManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 
 #include <algorithm>
 #include <cmath>
diff --git a/source/graphics/LOSTexture.cpp b/source/graphics/LOSTexture.cpp
index a375cda833..330176ecc0 100644
--- a/source/graphics/LOSTexture.cpp
+++ b/source/graphics/LOSTexture.cpp
@@ -44,9 +44,8 @@
 #include "simulation2/Simulation2.h"
 #include "simulation2/components/ICmpRangeManager.h"
 #include "simulation2/helpers/Los.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
-#include "simulation2/system/SimContext.h"
 
 #include <array>
 #include <cstring>
diff --git a/source/graphics/MapGenerator.cpp b/source/graphics/MapGenerator.cpp
index dc89cc0c87..4e7099f49e 100644
--- a/source/graphics/MapGenerator.cpp
+++ b/source/graphics/MapGenerator.cpp
@@ -46,7 +46,7 @@
 #include "scriptinterface/ScriptInterface.h"
 #include "scriptinterface/ScriptRequest.h"
 #include "simulation2/helpers/MapEdgeTiles.h"
-#include "simulation2/system/ParamNode.h"
+#include "simulation2/system/Component.h"
 
 #include <boost/random/linear_congruential.hpp>
 #include <cstddef>
diff --git a/source/graphics/MapWriter.cpp b/source/graphics/MapWriter.cpp
index cb4360a04b..794bf4d6c5 100644
--- a/source/graphics/MapWriter.cpp
+++ b/source/graphics/MapWriter.cpp
@@ -21,7 +21,6 @@
 
 #include "graphics/Camera.h"
 #include "graphics/Color.h"
-#include "graphics/HeightMipmap.h"
 #include "graphics/LightEnv.h"
 #include "graphics/MapIO.h"
 #include "graphics/MiniPatch.h"
@@ -45,6 +44,7 @@
 #include "renderer/PostprocManager.h"
 #include "renderer/SkyManager.h"
 #include "renderer/WaterManager.h"
+#include "scriptinterface/ScriptInterface.h"
 #include "simulation2/Simulation2.h"
 #include "simulation2/components/ICmpCinemaManager.h"
 #include "simulation2/components/ICmpGarrisonHolder.h"
@@ -56,8 +56,7 @@
 #include "simulation2/components/ICmpVisual.h"
 #include "simulation2/components/ICmpWaterManager.h"
 #include "simulation2/helpers/CinemaPath.h"
-#include "simulation2/system/CmpPtr.h"
-#include "simulation2/system/Components.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <algorithm>
diff --git a/source/graphics/MiniMapTexture.cpp b/source/graphics/MiniMapTexture.cpp
index d46607520b..b7a3f6301b 100644
--- a/source/graphics/MiniMapTexture.cpp
+++ b/source/graphics/MiniMapTexture.cpp
@@ -65,11 +65,8 @@
 #include "simulation2/components/ICmpMinimap.h"
 #include "simulation2/components/ICmpRangeManager.h"
 #include "simulation2/helpers/Position.h"
-#include "simulation2/system/CmpPtr.h"
-#include "simulation2/system/Components.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
-#include "simulation2/system/ParamNode.h"
-#include "simulation2/system/SimContext.h"
 
 #include <algorithm>
 #include <array>
diff --git a/source/graphics/Model.cpp b/source/graphics/Model.cpp
index 986213b56b..20856d162c 100644
--- a/source/graphics/Model.cpp
+++ b/source/graphics/Model.cpp
@@ -37,7 +37,7 @@
 #include "renderer/RenderingOptions.h"
 #include "simulation2/components/ICmpTerrain.h"
 #include "simulation2/components/ICmpWaterManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <algorithm>
diff --git a/source/graphics/ObjectManager.cpp b/source/graphics/ObjectManager.cpp
index 2d8d96fa8f..9e5e5c9055 100644
--- a/source/graphics/ObjectManager.cpp
+++ b/source/graphics/ObjectManager.cpp
@@ -28,13 +28,12 @@
 #include "ps/ConfigDB.h"
 #include "ps/Filesystem.h"
 #include "ps/Profiler2.h"
-#include "ps/XMB/XMBStorage.h"
 #include "ps/XML/Xeromyces.h"
+#include "scriptinterface/ScriptInterface.h"
 #include "simulation2/Simulation2.h"
 #include "simulation2/components/ICmpTerrain.h"
 #include "simulation2/components/ICmpVisual.h"
-#include "simulation2/system/CmpPtr.h"
-#include "simulation2/system/Components.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <cstddef>
diff --git a/source/graphics/scripting/JSInterface_GameView.cpp b/source/graphics/scripting/JSInterface_GameView.cpp
index 86998ffd5c..3a2d9e6cfe 100644
--- a/source/graphics/scripting/JSInterface_GameView.cpp
+++ b/source/graphics/scripting/JSInterface_GameView.cpp
@@ -34,7 +34,6 @@
 #include "simulation2/helpers/Position.h"
 #include "simulation2/system/Entity.h"
 
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <js/TypeDecls.h>
 #include <js/Value.h>
diff --git a/source/gui/CGUI.h b/source/gui/CGUI.h
index 780732de9d..7c16807550 100644
--- a/source/gui/CGUI.h
+++ b/source/gui/CGUI.h
@@ -39,10 +39,8 @@
 #include "scriptinterface/ModuleLoader.h"
 #include "scriptinterface/StructuredClone.h"
 
-#include <iterator>
 #include <js/RootingAPI.h>
 #include <js/TypeDecls.h>
-#include <js/Value.h>
 #include <map>
 #include <memory>
 #include <optional>
@@ -50,6 +48,7 @@
 #include <string_view>
 #include <unordered_map>
 #include <unordered_set>
+#include <utility>
 #include <vector>
 
 class CCanvas2D;
@@ -65,6 +64,7 @@ class ScriptRequest;
 class XMBData;
 class XMBElement;
 namespace JS { class HandleValueArray; }
+namespace JS { class Value; }
 namespace js { class BaseProxyHandler; }
 struct SDL_Event_;
 struct SGUIImageEffects;
diff --git a/source/gui/GUIManager.cpp b/source/gui/GUIManager.cpp
index 2898fe1320..4acbebfa08 100644
--- a/source/gui/GUIManager.cpp
+++ b/source/gui/GUIManager.cpp
@@ -22,6 +22,7 @@
 #include "gui/CGUI.h"
 #include "gui/SGUIMessage.h"
 #include "lib/debug.h"
+#include "lib/file/vfs/vfs_path.h"
 #include "lib/file/vfs/vfs_util.h"
 #include "lib/utf8.h"
 #include "ps/CLogger.h"
@@ -31,6 +32,7 @@
 #include "ps/Profiler2.h"
 #include "ps/VideoMode.h"
 #include "ps/XMB/XMBData.h"
+#include "ps/XMB/XMBStorage.h"
 #include "ps/XML/Xeromyces.h"
 #include "ps/containers/StaticVector.h"
 #include "scriptinterface/FunctionWrapper.h"
@@ -40,14 +42,13 @@
 #include "scriptinterface/ScriptInterface.h"
 #include "scriptinterface/ScriptRequest.h"
 #include "scriptinterface/StructuredClone.h"
-#include "simulation2/system/ParamNode.h"
+#include "simulation2/system/Component.h"
 
 #include <algorithm>
 #include <iterator>
 #include <js/Equality.h>
 #include <js/GCVector.h>
 #include <js/Promise.h>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <js/String.h>
 #include <js/Symbol.h>
diff --git a/source/gui/GUIManager.h b/source/gui/GUIManager.h
index 789eafe6ec..02ef174369 100644
--- a/source/gui/GUIManager.h
+++ b/source/gui/GUIManager.h
@@ -19,12 +19,12 @@
 #define INCLUDED_GUIMANAGER
 
 #include "lib/code_annotation.h"
-#include "lib/file/vfs/vfs_path.h"
 #include "lib/input.h"
 #include "lib/path.h"
 #include "lib/status.h"
 #include "ps/CStr.h"
 #include "ps/TemplateLoader.h"
+#include "scriptinterface/ScriptInterface.h"
 #include "scriptinterface/StructuredClone.h"
 
 #include <cstddef>
@@ -39,7 +39,6 @@ class CCanvas2D;
 class CGUI;
 class CParamNode;
 class ScriptContext;
-class ScriptInterface;
 namespace JS { class HandleValueArray; }
 namespace JS { class Value; }
 namespace PS { template <typename T, size_t N> class StaticVector; }
diff --git a/source/gui/GUIRenderer.cpp b/source/gui/GUIRenderer.cpp
index 0ab2f16718..107bdd6812 100644
--- a/source/gui/GUIRenderer.cpp
+++ b/source/gui/GUIRenderer.cpp
@@ -27,13 +27,11 @@
 #include "gui/SettingTypes/CGUISize.h"
 #include "i18n/L10n.h"
 #include "lib/file/vfs/vfs_path.h"
-#include "lib/path.h"
 #include "lib/utf8.h"
 #include "maths/Vector2D.h"
 #include "ps/CLogger.h"
 #include "ps/CStr.h"
 #include "renderer/Renderer.h"
-#include "renderer/backend/Sampler.h"
 
 #include <string>
 #include <utility>
diff --git a/source/gui/ObjectBases/IGUIObject.cpp b/source/gui/ObjectBases/IGUIObject.cpp
index ea4e6b1fd6..b972eb7e3b 100644
--- a/source/gui/ObjectBases/IGUIObject.cpp
+++ b/source/gui/ObjectBases/IGUIObject.cpp
@@ -36,7 +36,6 @@
 #include "soundmanager/ISoundManager.h"
 
 #include <algorithm>
-#include <iterator>
 #include <js/CallAndConstruct.h>
 #include <js/ComparisonOperators.h>
 #include <js/CompilationAndEvaluation.h>
diff --git a/source/gui/ObjectTypes/CDropDown.cpp b/source/gui/ObjectTypes/CDropDown.cpp
index 19e8066a83..4f3a308e35 100644
--- a/source/gui/ObjectTypes/CDropDown.cpp
+++ b/source/gui/ObjectTypes/CDropDown.cpp
@@ -32,6 +32,7 @@
 #include <SDL_events.h>
 #include <SDL_keycode.h>
 #include <algorithm>
+#include <cmath>
 #include <cstdlib>
 #include <vector>
 
diff --git a/source/gui/ObjectTypes/CMiniMap.cpp b/source/gui/ObjectTypes/CMiniMap.cpp
index 72e61f08f4..4afc3f9bdc 100644
--- a/source/gui/ObjectTypes/CMiniMap.cpp
+++ b/source/gui/ObjectTypes/CMiniMap.cpp
@@ -47,13 +47,14 @@
 #include "scriptinterface/ScriptConversions.h"
 #include "scriptinterface/ScriptRequest.h"
 #include "simulation2/components/ICmpRangeManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <SDL_mouse.h>
 #include <algorithm>
 #include <array>
 #include <cmath>
+#include <cstddef>
 #include <fmt/printf.h>
 #include <js/GCVector.h>
 #include <js/RootingAPI.h>
@@ -61,7 +62,6 @@
 #include <js/Value.h>
 #include <js/ValueArray.h>
 #include <memory>
-#include <stddef.h>
 #include <string>
 #include <tuple>
 #include <vector>
diff --git a/source/gui/Scripting/JSInterface_CGUISize.cpp b/source/gui/Scripting/JSInterface_CGUISize.cpp
index d56c7b715d..78bc8e57fb 100644
--- a/source/gui/Scripting/JSInterface_CGUISize.cpp
+++ b/source/gui/Scripting/JSInterface_CGUISize.cpp
@@ -40,7 +40,6 @@
 #include <js/Class.h>
 #include <js/Conversions.h>
 #include <js/Object.h>
-#include <js/PropertyAndElement.h>
 #include <js/PropertyDescriptor.h>
 #include <js/PropertySpec.h>
 #include <js/RootingAPI.h>
diff --git a/source/gui/Scripting/JSInterface_GUIManager.cpp b/source/gui/Scripting/JSInterface_GUIManager.cpp
index 0b0c526cc4..091fe6a60c 100644
--- a/source/gui/Scripting/JSInterface_GUIManager.cpp
+++ b/source/gui/Scripting/JSInterface_GUIManager.cpp
@@ -21,19 +21,18 @@
 
 #include "gui/CGUI.h"
 #include "gui/GUIManager.h"
+#include "ps/CStr.h"
 #include "ps/VideoMode.h"
 #include "scriptinterface/FunctionWrapper.h"
 #include "scriptinterface/ScriptInterface.h"
 #include "scriptinterface/StructuredClone.h"
-#include "simulation2/system/ParamNode.h"
-#include <js/PropertyAndElement.h>
+#include "simulation2/system/Component.h"
+
 #include <js/RootingAPI.h>
 #include <js/TypeDecls.h>
 #include <js/Value.h>
 #include <string>
 
-#include <stdexcept>
-
 namespace JSI_GUIManager
 {
 // Note that the initData argument may only contain clonable data.
diff --git a/source/gui/Scripting/JSInterface_GUIProxy.h b/source/gui/Scripting/JSInterface_GUIProxy.h
index 1cd1ce3aef..0e7d750f47 100644
--- a/source/gui/Scripting/JSInterface_GUIProxy.h
+++ b/source/gui/Scripting/JSInterface_GUIProxy.h
@@ -22,7 +22,6 @@
 #include "lib/sysdep/compiler.h"
 #include "scriptinterface/ScriptExtraHeaders.h"
 
-#include <iterator>
 #include <js/GCVector.h>
 #include <js/Id.h>
 #include <js/Proxy.h>
@@ -31,7 +30,9 @@
 #include <js/Value.h>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <utility>
+#include <vector>
 
 class JSFunction;
 class JSObject;
diff --git a/source/gui/Scripting/JSInterface_GUISize.h b/source/gui/Scripting/JSInterface_GUISize.h
index 0999d49a52..137ae92275 100644
--- a/source/gui/Scripting/JSInterface_GUISize.h
+++ b/source/gui/Scripting/JSInterface_GUISize.h
@@ -19,17 +19,18 @@
 #define INCLUDED_JSI_GUISIZE
 
 
+#include "lib/posix/posix_types.h"
 #include "lib/types.h"
 #include "ps/CStr.h"
 #include "scriptinterface/ScriptTypes.h"
 
-#include <js/PropertySpec.h>
-
 class ScriptInterface;
 namespace JS { class Value; }
 struct JSClass;
 struct JSClassOps;
 struct JSContext;
+struct JSFunctionSpec;
+struct JSPropertySpec;
 
 namespace JSI_GUISize
 {
diff --git a/source/gui/tests/test_GuiManager.h b/source/gui/tests/test_GuiManager.h
index 423b425b0b..6e18183957 100644
--- a/source/gui/tests/test_GuiManager.h
+++ b/source/gui/tests/test_GuiManager.h
@@ -25,7 +25,6 @@
 #include "lib/file/vfs/vfs.h"
 #include "lib/input.h"
 #include "lib/path.h"
-#include "lib/sysdep/compiler.h"
 #include "ps/CLogger.h"
 #include "ps/CStr.h"
 #include "ps/ConfigDB.h"
@@ -40,18 +39,18 @@
 #include "scriptinterface/ScriptRequest.h"
 #include "scriptinterface/StructuredClone.h"
 
+#include <SDL_events.h>
+#include <SDL_scancode.h>
 #include <array>
 #include <js/CallArgs.h>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <js/TypeDecls.h>
 #include <js/Value.h>
 #include <memory>
 #include <optional>
-#include <SDL_events.h>
-#include <SDL_scancode.h>
 #include <stdexcept>
 #include <tuple>
+#include <utility>
 #include <variant>
 
 #include "js/Promise.h"
diff --git a/source/i18n/scripting/JSInterface_L10n.cpp b/source/i18n/scripting/JSInterface_L10n.cpp
index bf2ff8d2a7..a25a055afa 100644
--- a/source/i18n/scripting/JSInterface_L10n.cpp
+++ b/source/i18n/scripting/JSInterface_L10n.cpp
@@ -23,7 +23,6 @@
 #include "ps/CLogger.h"
 #include "scriptinterface/FunctionWrapper.h"
 
-#include <js/PropertyAndElement.h>
 #include <unicode/utypes.h>
 #include <string>
 #include <vector>
diff --git a/source/lib/allocators/shared_ptr.h b/source/lib/allocators/shared_ptr.h
index 5afbdbc53d..21f17da6bc 100644
--- a/source/lib/allocators/shared_ptr.h
+++ b/source/lib/allocators/shared_ptr.h
@@ -24,6 +24,7 @@
 #define INCLUDED_ALLOCATORS_SHARED_PTR
 
 #include "lib/alignment.h"
+#include "lib/debug.h"
 #include "lib/status.h"
 #include "lib/sysdep/rtl.h" // rtl_AllocateAligned
 #include "lib/types.h"
diff --git a/source/lib/file/file.cpp b/source/lib/file/file.cpp
index ed4cd05854..9001c99b60 100644
--- a/source/lib/file/file.cpp
+++ b/source/lib/file/file.cpp
@@ -32,7 +32,6 @@
 #include "lib/debug.h"
 #include "lib/file/common/file_stats.h"
 #include "lib/posix/posix_filesystem.h"
-#include "lib/posix/posix_types.h"
 #include "lib/sysdep/filesystem.h"
 
 #include <cerrno>
diff --git a/source/lib/file/io/io.h b/source/lib/file/io/io.h
index fdb98be213..2371b3ad4f 100644
--- a/source/lib/file/io/io.h
+++ b/source/lib/file/io/io.h
@@ -49,8 +49,6 @@
 #include <fcntl.h>
 #include <memory>
 
-#include <utility>
-
 namespace ERR
 {
 	const Status IO = -110301;
diff --git a/source/lib/file/vfs/vfs_tree.h b/source/lib/file/vfs/vfs_tree.h
index 04eeabd79f..14db9dab62 100644
--- a/source/lib/file/vfs/vfs_tree.h
+++ b/source/lib/file/vfs/vfs_tree.h
@@ -27,15 +27,12 @@
 #ifndef INCLUDED_VFS_TREE
 #define INCLUDED_VFS_TREE
 
-#include <map>
-
 #include "lib/file/common/file_loader.h"	// PIFileLoader
 #include "lib/file/common/real_directory.h"	// PRealDirectory
 #include "lib/file/vfs/vfs_path.h"
-#include "lib/path.h"
 
 #include <ctime>
-#include <memory>
+#include <map>
 #include <string>
 
 class VfsFile
diff --git a/source/lib/input.h b/source/lib/input.h
index 8a673af762..9df9d8ca7c 100644
--- a/source/lib/input.h
+++ b/source/lib/input.h
@@ -27,8 +27,6 @@
 #ifndef INCLUDED_INPUT
 #define INCLUDED_INPUT
 
-#include "lib/external_libraries/libsdl_fwd.h"
-
 struct SDL_Event_;
 
 // input handler return values.
diff --git a/source/lib/ogl.cpp b/source/lib/ogl.cpp
index 4808bf37a7..d530727630 100644
--- a/source/lib/ogl.cpp
+++ b/source/lib/ogl.cpp
@@ -35,6 +35,7 @@
 # if OS_WIN
 #  include <glad/wgl.h>
 # elif !OS_MACOSX
+#  include <SDL_config.h>
 #  include <SDL_syswm.h>
 #  if defined(SDL_VIDEO_DRIVER_X11)
 #   include <X11/Xlib.h>
diff --git a/source/lib/secure_crt.cpp b/source/lib/secure_crt.cpp
index 4dae6efe2c..486b1d413f 100644
--- a/source/lib/secure_crt.cpp
+++ b/source/lib/secure_crt.cpp
@@ -36,7 +36,6 @@
 #include <cinttypes>
 #include <cstdarg>
 #include <cstdio>
-#include <cstring>
 
 #if OS_ANDROID
 # include <boost/algorithm/string/replace.hpp>
diff --git a/source/lib/secure_crt.h b/source/lib/secure_crt.h
index 4c1eee2540..a43f865a95 100644
--- a/source/lib/secure_crt.h
+++ b/source/lib/secure_crt.h
@@ -30,7 +30,6 @@
 #include "lib/code_annotation.h"
 #include "lib/status.h"
 #include "lib/sysdep/compiler.h"
-#include "lib/sysdep/os.h"
 
 #include <cstdarg>
 #include <cstddef>
diff --git a/source/lib/self_test.h b/source/lib/self_test.h
index f0c3275086..2f69dd92e4 100644
--- a/source/lib/self_test.h
+++ b/source/lib/self_test.h
@@ -38,6 +38,7 @@
 // If HAVE_STD wasn't defined at the point the ValueTraits header was included
 // this header won't have been included and the default traits will be used for
 // all variables... So fix that now ;-)
+#include <cxxtest/GlobalFixture.h>
 #include <cxxtest/StdValueTraits.h>
 #include <cxxtest/TestSuite.h>
 
diff --git a/source/lib/sysdep/arch/x86_x64/apic.cpp b/source/lib/sysdep/arch/x86_x64/apic.cpp
index 15ca58c905..e258c09a01 100644
--- a/source/lib/sysdep/arch/x86_x64/apic.cpp
+++ b/source/lib/sysdep/arch/x86_x64/apic.cpp
@@ -25,7 +25,6 @@
 #include "apic.h"
 
 #include "lib/bits.h"
-#include "lib/code_annotation.h"
 #include "lib/debug.h"
 #include "lib/module_init.h"
 #include "lib/status.h"
diff --git a/source/lib/tests/test_cache_adt.h b/source/lib/tests/test_cache_adt.h
index 5b3a335354..2e10595a6b 100644
--- a/source/lib/tests/test_cache_adt.h
+++ b/source/lib/tests/test_cache_adt.h
@@ -23,7 +23,6 @@
 #include "lib/self_test.h"
 
 #include "lib/adts/cache_adt.h"
-#include "lib/timer.h"
 
 #include <cstddef>
 #include <queue>
diff --git a/source/lib/timer.cpp b/source/lib/timer.cpp
index 7ed7cae230..023f646d98 100644
--- a/source/lib/timer.cpp
+++ b/source/lib/timer.cpp
@@ -32,6 +32,7 @@
 #include "lib/posix/posix_types.h"
 #include "lib/status.h"
 #include "lib/sysdep/os.h"
+#include "lib/utf8.h"
 
 #include <algorithm>
 #include <ctime>
diff --git a/source/lib/timer.h b/source/lib/timer.h
index e6af2da934..39addee166 100644
--- a/source/lib/timer.h
+++ b/source/lib/timer.h
@@ -31,7 +31,6 @@
 #include "lib/config2.h"	// CONFIG2_TIMER_ALLOW_RDTSC
 #include "lib/debug.h"
 #include "lib/sysdep/arch.h"
-#include "lib/utf8.h"
 
 #include <cstdint>
 #include <string>
diff --git a/source/network/tests/test_FSM.h b/source/network/tests/test_FSM.h
index 85f7a47d00..595fa4971e 100644
--- a/source/network/tests/test_FSM.h
+++ b/source/network/tests/test_FSM.h
@@ -21,9 +21,6 @@
 
 #include <array>
 #include <cstddef>
-#include <memory>
-#include <new>
-#include <unordered_map>
 #include <utility>
 #include <variant>
 
diff --git a/source/network/tests/test_Net.h b/source/network/tests/test_Net.h
index 4d258c542d..96a7972961 100644
--- a/source/network/tests/test_Net.h
+++ b/source/network/tests/test_Net.h
@@ -22,7 +22,7 @@
 #include "lib/file/file_system.h"
 #include "lib/file/vfs/vfs.h"
 #include "lib/path.h"
-#include "lib/types.h"
+#include "lib/posix/posix_types.h"
 #include "network/NetClient.h"
 #include "network/NetMessage.h"
 #include "network/NetServer.h"
@@ -42,10 +42,8 @@
 #include <js/RootingAPI.h>
 #include <js/TypeDecls.h>
 #include <js/Value.h>
-#include <memory>
 #include <optional>
 #include <string>
-#include <utility>
 #include <vector>
 
 class TestNetComms : public CxxTest::TestSuite
diff --git a/source/pch/atlas/precompiled.h b/source/pch/atlas/precompiled.h
index 3da1657434..e835aa40bf 100644
--- a/source/pch/atlas/precompiled.h
+++ b/source/pch/atlas/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2019 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,8 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #define MINIMAL_PCH 2
 #include "lib/precompiled.h"	// common precompiled header
 
@@ -30,3 +32,5 @@
 #include <unordered_map>
 
 #endif // CONFIG_ENABLE_PCH
+
+// IWYU pragma: end_keep
diff --git a/source/pch/engine/precompiled.h b/source/pch/engine/precompiled.h
index 73b4f59ddf..df76d5f55f 100644
--- a/source/pch/engine/precompiled.h
+++ b/source/pch/engine/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2020 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,8 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #include "lib/precompiled.h"	// common precompiled header
 
 // "engine"-specific PCH:
@@ -26,3 +28,5 @@
 #include "lib/file/vfs/vfs_util.h"
 #include "scriptinterface/ScriptTypes.h"
 #endif // CONFIG_ENABLE_PCH
+
+// IWYU pragma: end_keep
diff --git a/source/pch/gui/precompiled.h b/source/pch/gui/precompiled.h
index 5c703e93c5..402626fa77 100644
--- a/source/pch/gui/precompiled.h
+++ b/source/pch/gui/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,8 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #define MINIMAL_PCH 2
 #include "lib/precompiled.h"	// common precompiled header
 
@@ -28,3 +30,5 @@
 #include "ps/CStr.h"
 
 #endif // CONFIG_ENABLE_PCH
+
+// IWYU pragma: end_keep
diff --git a/source/pch/lowlevel/precompiled.h b/source/pch/lowlevel/precompiled.h
index 2cd85d519e..9031b1dca5 100644
--- a/source/pch/lowlevel/precompiled.h
+++ b/source/pch/lowlevel/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,10 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #include "lib/precompiled.h"	// common precompiled header
 
 // "lowlevel"-specific PCH:
+
+// IWYU pragma: end_keep
diff --git a/source/pch/test/precompiled.h b/source/pch/test/precompiled.h
index 7b195e4480..8bf2613271 100644
--- a/source/pch/test/precompiled.h
+++ b/source/pch/test/precompiled.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2019 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -15,6 +15,8 @@
  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+// IWYU pragma: begin_keep
+
 #include "lib/precompiled.h"	// common precompiled header
 
 #if CONFIG_ENABLE_PCH
@@ -27,3 +29,5 @@
 #include <cxxtest/RealDescriptions.h>
 
 #endif // CONFIG_ENABLE_PCH
+
+// IWYU pragma: end_keep
diff --git a/source/ps/Hotkey.h b/source/ps/Hotkey.h
index de0be44ac1..b407e9c5a4 100644
--- a/source/ps/Hotkey.h
+++ b/source/ps/Hotkey.h
@@ -32,7 +32,7 @@
  */
 
 #include "lib/input.h"
-#include "lib/posix/posix_types.h"
+#include "lib/types.h"
 #include "ps/CStr.h"
 #include "ps/containers/StaticVector.h"
 
diff --git a/source/renderer/DecalRData.cpp b/source/renderer/DecalRData.cpp
index 06d9c01eb4..ea1f6a8774 100644
--- a/source/renderer/DecalRData.cpp
+++ b/source/renderer/DecalRData.cpp
@@ -48,7 +48,7 @@
 #include "renderer/backend/IDeviceCommandContext.h"
 #include "renderer/backend/IShaderProgram.h"
 #include "simulation2/components/ICmpWaterManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <algorithm>
diff --git a/source/renderer/PatchRData.cpp b/source/renderer/PatchRData.cpp
index f558939df7..66566af3dd 100644
--- a/source/renderer/PatchRData.cpp
+++ b/source/renderer/PatchRData.cpp
@@ -60,7 +60,7 @@
 #include "renderer/backend/IDeviceCommandContext.h"
 #include "renderer/backend/IShaderProgram.h"
 #include "simulation2/components/ICmpWaterManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
 
 #include <algorithm>
diff --git a/source/renderer/TerrainOverlay.cpp b/source/renderer/TerrainOverlay.cpp
index 03687cdc7a..61034959e2 100644
--- a/source/renderer/TerrainOverlay.cpp
+++ b/source/renderer/TerrainOverlay.cpp
@@ -47,7 +47,7 @@
 #include "renderer/backend/ITexture.h"
 #include "renderer/backend/PipelineState.h"
 #include "renderer/backend/Sampler.h"
-#include "simulation2/system/SimContext.h"
+#include "simulation2/system/Component.h"
 
 #include <algorithm>
 #include <array>
diff --git a/source/renderer/TexturedLineRData.cpp b/source/renderer/TexturedLineRData.cpp
index 34352d67a2..fd87fbe8d9 100644
--- a/source/renderer/TexturedLineRData.cpp
+++ b/source/renderer/TexturedLineRData.cpp
@@ -37,9 +37,8 @@
 #include "renderer/backend/IDeviceCommandContext.h"
 #include "renderer/backend/IShaderProgram.h"
 #include "simulation2/components/ICmpWaterManager.h"
-#include "simulation2/system/CmpPtr.h"
+#include "simulation2/system/Component.h"
 #include "simulation2/system/Entity.h"
-#include "simulation2/system/SimContext.h"
 
 #include <array>
 #include <cmath>
diff --git a/source/renderer/backend/dummy/Device.cpp b/source/renderer/backend/dummy/Device.cpp
index 64652fa958..67d508626b 100644
--- a/source/renderer/backend/dummy/Device.cpp
+++ b/source/renderer/backend/dummy/Device.cpp
@@ -32,7 +32,6 @@
 
 #include <SDL_video.h>
 #include <initializer_list>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 
 namespace Renderer
diff --git a/source/renderer/backend/gl/Device.cpp b/source/renderer/backend/gl/Device.cpp
index a79bcf5698..acafeabbc8 100644
--- a/source/renderer/backend/gl/Device.cpp
+++ b/source/renderer/backend/gl/Device.cpp
@@ -42,6 +42,7 @@
 #include "renderer/backend/gl/Texture.h"
 #include "scriptinterface/Object.h"
 
+#include <SDL_config.h>
 #include <SDL_error.h>
 #include <SDL_version.h>
 #include <SDL_video.h>
@@ -52,7 +53,6 @@
 #include <climits>
 #include <cstring>
 #include <iterator>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <limits>
 #include <utility>
diff --git a/source/renderer/backend/vulkan/Device.cpp b/source/renderer/backend/vulkan/Device.cpp
index 965077f600..d2c7b66220 100644
--- a/source/renderer/backend/vulkan/Device.cpp
+++ b/source/renderer/backend/vulkan/Device.cpp
@@ -51,7 +51,6 @@
 #include <algorithm>
 #include <array>
 #include <iterator>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <js/Value.h>
 #include <limits>
diff --git a/source/renderer/backend/vulkan/DeviceCommandContext.cpp b/source/renderer/backend/vulkan/DeviceCommandContext.cpp
index 0854fec56c..d20f7edd61 100644
--- a/source/renderer/backend/vulkan/DeviceCommandContext.cpp
+++ b/source/renderer/backend/vulkan/DeviceCommandContext.cpp
@@ -21,7 +21,6 @@
 
 #include "graphics/Color.h"
 #include "lib/bits.h"
-#include "lib/code_annotation.h"
 #include "lib/debug.h"
 #include "ps/CLogger.h"
 #include "ps/ConfigDB.h"
diff --git a/source/renderer/backend/vulkan/DeviceSelection.cpp b/source/renderer/backend/vulkan/DeviceSelection.cpp
index 057f0aa552..ad04399549 100644
--- a/source/renderer/backend/vulkan/DeviceSelection.cpp
+++ b/source/renderer/backend/vulkan/DeviceSelection.cpp
@@ -26,7 +26,6 @@
 
 #include <algorithm>
 #include <iterator>
-#include <js/PropertyAndElement.h>
 #include <js/RootingAPI.h>
 #include <js/Value.h>
 #include <limits>
diff --git a/source/renderer/scripting/JSInterface_Renderer.cpp b/source/renderer/scripting/JSInterface_Renderer.cpp
index fc4c3783e9..e1664b7f9c 100644
--- a/source/renderer/scripting/JSInterface_Renderer.cpp
+++ b/source/renderer/scripting/JSInterface_Renderer.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -26,7 +26,6 @@
 #include "renderer/RenderingOptions.h"
 #include "scriptinterface/FunctionWrapper.h"
 
-#include <js/PropertyAndElement.h>
 #include <string>
 
 namespace JSI_Renderer
diff --git a/source/scriptinterface/ScriptInterface.h b/source/scriptinterface/ScriptInterface.h
index 70daf2146c..b65559802b 100644
--- a/source/scriptinterface/ScriptInterface.h
+++ b/source/scriptinterface/ScriptInterface.h
@@ -19,7 +19,6 @@
 #define INCLUDED_SCRIPTINTERFACE
 
 #include "lib/code_annotation.h"
-#include "lib/posix/posix_types.h"
 #include "lib/types.h"
 #include "ps/Errors.h"
 #include "scriptinterface/ScriptConversions.h"
@@ -43,7 +42,6 @@
 class JSObject;
 class Path;
 class ScriptContext;
-namespace JS { class HandleValueArray; }
 namespace Script { class ModuleLoader; }
 namespace boost { namespace random { class rand48; } }
 struct JSClass;
diff --git a/source/simulation2/components/CCmpRallyPointRenderer.cpp b/source/simulation2/components/CCmpRallyPointRenderer.cpp
index b4d34fc388..39b902df5b 100644
--- a/source/simulation2/components/CCmpRallyPointRenderer.cpp
+++ b/source/simulation2/components/CCmpRallyPointRenderer.cpp
@@ -31,11 +31,14 @@
 #include "renderer/Scene.h"
 #include "renderer/backend/Sampler.h"
 #include "simulation2/MessageTypes.h"
+#include "simulation2/components/ICmpFootprint.h"
 #include "simulation2/components/ICmpIdentity.h"
 #include "simulation2/components/ICmpObstructionManager.h"
 #include "simulation2/components/ICmpOwnership.h"
+#include "simulation2/components/ICmpPathfinder.h"
 #include "simulation2/components/ICmpPlayer.h"
 #include "simulation2/components/ICmpPlayerManager.h"
+#include "simulation2/components/ICmpPosition.h"
 #include "simulation2/components/ICmpRangeManager.h"
 #include "simulation2/components/ICmpTerrain.h"
 #include "simulation2/components/ICmpWaterManager.h"
diff --git a/source/simulation2/components/CCmpRallyPointRenderer.h b/source/simulation2/components/CCmpRallyPointRenderer.h
index 73b895deff..d8894d20f9 100644
--- a/source/simulation2/components/CCmpRallyPointRenderer.h
+++ b/source/simulation2/components/CCmpRallyPointRenderer.h
@@ -24,9 +24,6 @@
 #include "lib/types.h"
 #include "maths/FixedVector2D.h"
 #include "maths/Vector2D.h"
-#include "simulation2/components/ICmpFootprint.h"
-#include "simulation2/components/ICmpPathfinder.h"
-#include "simulation2/components/ICmpPosition.h"
 #include "simulation2/components/ICmpRallyPointRenderer.h"
 #include "simulation2/helpers/Player.h"
 #include "simulation2/system/Component.h"
@@ -37,6 +34,9 @@
 #include <vector>
 
 class CFrustum;
+class ICmpFootprint;
+class ICmpPathfinder;
+class ICmpPosition;
 class SceneCollector;
 
 struct SVisibilitySegment
diff --git a/source/simulation2/components/CCmpUnitMotionManager.h b/source/simulation2/components/CCmpUnitMotionManager.h
index 35e6466e62..08904cf3e6 100644
--- a/source/simulation2/components/CCmpUnitMotionManager.h
+++ b/source/simulation2/components/CCmpUnitMotionManager.h
@@ -20,7 +20,6 @@
 
 #include "maths/Fixed.h"
 #include "maths/FixedVector2D.h"
-#include "simulation2/MessageTypes.h"
 #include "simulation2/components/ICmpUnitMotionManager.h"
 #include "simulation2/helpers/Grid.h"
 #include "simulation2/helpers/Position.h"
diff --git a/source/simulation2/components/tests/test_TerritoryManager.h b/source/simulation2/components/tests/test_TerritoryManager.h
index 48ba8617f1..7d9fbda6ed 100644
--- a/source/simulation2/components/tests/test_TerritoryManager.h
+++ b/source/simulation2/components/tests/test_TerritoryManager.h
@@ -34,6 +34,7 @@
 #include "scriptinterface/ScriptInterface.h"
 #include "simulation2/MessageTypes.h"
 #include "simulation2/components/ICmpObstruction.h"
+#include "simulation2/components/ICmpObstructionManager.h"
 #include "simulation2/components/ICmpOwnership.h"
 #include "simulation2/components/ICmpPathfinder.h"
 #include "simulation2/components/ICmpPlayerManager.h"
diff --git a/source/simulation2/helpers/VertexPathfinder.h b/source/simulation2/helpers/VertexPathfinder.h
index 260e6a4320..addbe22c10 100644
--- a/source/simulation2/helpers/VertexPathfinder.h
+++ b/source/simulation2/helpers/VertexPathfinder.h
@@ -76,10 +76,6 @@ struct EdgeAA
 	fixed c1;
 };
 
-class ICmpObstructionManager;
-class CSimContext;
-class SceneCollector;
-
 class VertexPathfinder
 {
 public:
diff --git a/source/simulation2/tests/test_EntityMap.h b/source/simulation2/tests/test_EntityMap.h
index 3159250236..28f7d8bd71 100644
--- a/source/simulation2/tests/test_EntityMap.h
+++ b/source/simulation2/tests/test_EntityMap.h
@@ -22,8 +22,6 @@
 
 #include <algorithm>
 #include <cstdio>
-#include <cstdlib>
-#include <new>
 #include <random>
 #include <utility>
 #include <vector>
diff --git a/source/soundmanager/data/ogg.cpp b/source/soundmanager/data/ogg.cpp
index d653e76a86..858954ba17 100644
--- a/source/soundmanager/data/ogg.cpp
+++ b/source/soundmanager/data/ogg.cpp
@@ -34,6 +34,7 @@
 #include <fcntl.h>
 #include <fmt/format.h>
 #include <iterator>
+#include <ogg/config_types.h>
 #include <stdexcept>
 #include <vorbis/codec.h>
 #include <vorbis/vorbisfile.h>
diff --git a/source/soundmanager/items/CBufferItem.cpp b/source/soundmanager/items/CBufferItem.cpp
index dba96531db..a3ec9706fa 100644
--- a/source/soundmanager/items/CBufferItem.cpp
+++ b/source/soundmanager/items/CBufferItem.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -21,9 +21,12 @@
 
 #if CONFIG2_AUDIO
 
+#include "soundmanager/ISoundManager.h"
 #include "soundmanager/SoundManager.h"
 #include "soundmanager/data/SoundData.h"
 
+#include <AL/al.h>
+#include <cstddef>
 #include <mutex>
 
 CBufferItem::CBufferItem(CSoundData* sndData)
diff --git a/source/test_setup.cpp b/source/test_setup.cpp
index 1bd4e5045a..dcf6a7b9e2 100644
--- a/source/test_setup.cpp
+++ b/source/test_setup.cpp
@@ -24,20 +24,18 @@
 
 #include "precompiled.h"
 
-#include <fstream>
-
 #include "lib/self_test.h"
-#include <cxxtest/GlobalFixture.h>
 
-#include "lib/timer.h"
 #include "lib/sysdep/sysdep.h"
+#include "lib/timer.h"
 #include "ps/Profiler2.h"
 #include "ps/TaskManager.h"
 #include "scriptinterface/FunctionWrapper.h"
-#include "scriptinterface/ScriptEngine.h"
 #include "scriptinterface/ScriptContext.h"
+#include "scriptinterface/ScriptEngine.h"
 #include "scriptinterface/ScriptInterface.h"
 
+#include <fstream>
 #include <optional>
 
 class LeakReporter : public CxxTest::GlobalFixture