diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1abe420b67..5c485a0c6a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -363,7 +363,8 @@ set(DUSK_COPYRIGHT "Copyright (C) Twilit Realm contributors")
 source_group("dolzel" FILES ${DOLZEL_FILES} ${Z2AUDIOLIB_FILES} ${REL_FILES})
 source_group("dusklight" FILES ${DUSK_FILES} ${DUSK_HTTP_BACKEND_FILES})
 
-set(GAME_COMPILE_DEFS TARGET_PC WIDESCREEN_SUPPORT=1 AVOID_UB=1 VERSION=0 MTX_USE_PS=1)
+# PARTIAL_DEBUG makes debug and release share one struct/vtable ABI so a mod binary loads into either
+set(GAME_COMPILE_DEFS TARGET_PC WIDESCREEN_SUPPORT=1 AVOID_UB=1 VERSION=0 MTX_USE_PS=1 PARTIAL_DEBUG=1)
 
 set(GAME_INCLUDE_DIRS
     include
@@ -474,7 +475,7 @@ set(GAME_DEBUG_FILES
 set_source_files_properties(
         ${GAME_DEBUG_FILES}
         PROPERTIES
-        COMPILE_DEFINITIONS "$<$<CONFIG:Debug>:DEBUG=1>;$<$<CONFIG:Debug>:PARTIAL_DEBUG=1>"
+        COMPILE_DEFINITIONS "$<$<CONFIG:Debug>:DEBUG=1>;PARTIAL_DEBUG=1"
 )
 
 # game_base is for all other game code files
@@ -488,14 +489,14 @@ set(GAME_BASE_FILES
 set_source_files_properties(
         ${GAME_BASE_FILES}
         PROPERTIES
-        COMPILE_DEFINITIONS "NDEBUG=1;NDEBUG_DEFINED=1;DEBUG_DEFINED=0;$<$<CONFIG:Debug>:PARTIAL_DEBUG=1>"
+        COMPILE_DEFINITIONS "NDEBUG=1;NDEBUG_DEFINED=1;DEBUG_DEFINED=0;PARTIAL_DEBUG=1"
 )
 
 foreach(jsystem_lib IN LISTS JSYSTEM_LIBRARIES)
     target_compile_definitions(${jsystem_lib} PRIVATE
             ${GAME_COMPILE_DEFS}
             $<$<CONFIG:Debug>:DEBUG=1>
-            $<$<CONFIG:Debug>:PARTIAL_DEBUG=1>
+            PARTIAL_DEBUG=1
     )
     target_include_directories(${jsystem_lib} PRIVATE ${GAME_INCLUDE_DIRS})
     target_link_libraries(${jsystem_lib} PRIVATE ${GAME_LIBS})
diff --git a/include/SSystem/SComponent/c_bg_s_shdw_draw.h b/include/SSystem/SComponent/c_bg_s_shdw_draw.h
index 9ec3023306..55792f8410 100644
--- a/include/SSystem/SComponent/c_bg_s_shdw_draw.h
+++ b/include/SSystem/SComponent/c_bg_s_shdw_draw.h
@@ -20,7 +20,7 @@ public:
 
     /* 0x14 */ cM3dGAab mM3dGAab;
     /* 0x30 */ cBgS_ShdwDraw_Callback mCallbackFun;
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     /* 0x34 */ int field_0x34;
     #endif
 };
diff --git a/include/Z2AudioLib/Z2AudioMgr.h b/include/Z2AudioLib/Z2AudioMgr.h
index e543bf6061..0f8e5a17ea 100644
--- a/include/Z2AudioLib/Z2AudioMgr.h
+++ b/include/Z2AudioLib/Z2AudioMgr.h
@@ -48,6 +48,8 @@ public:
     /* 0x1370 */ Z2FxLineMgr mFxLineMgr;
     #if DEBUG
     /* 0x13BC */ Z2DebugSys mDebugSys;
+    #elif PARTIAL_DEBUG
+    alignas(Z2DebugSys) u8 mDebugSys[sizeof(Z2DebugSys)];
     #endif
 };  // Size: 0x138C
 
diff --git a/include/Z2AudioLib/Z2SeqMgr.h b/include/Z2AudioLib/Z2SeqMgr.h
index 76c2674697..94191a1318 100644
--- a/include/Z2AudioLib/Z2SeqMgr.h
+++ b/include/Z2AudioLib/Z2SeqMgr.h
@@ -194,7 +194,7 @@ public:
     JAISoundHandle* getMainBgmHandle() { return &mMainBgmHandle; }
     JAISoundHandle* getSubBgmHandle() { return &mSubBgmHandle; }
 
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     f32 field_0x00_debug;
     u8 field_0x04_debug;
     #endif
diff --git a/include/Z2AudioLib/Z2SoundObjMgr.h b/include/Z2AudioLib/Z2SoundObjMgr.h
index c0b4ed778c..687f9eaf0a 100644
--- a/include/Z2AudioLib/Z2SoundObjMgr.h
+++ b/include/Z2AudioLib/Z2SoundObjMgr.h
@@ -100,13 +100,13 @@ public:
     bool isForceBattle() { return forceBattle_; }
     JSUList<Z2CreatureEnemy>* getEnemyList() { return &field_0x0; }
 
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     JSUList<Z2SoundObjBase>* getAllList() { return &allList_; }
     #endif
 
 private:
     /* 0x00 */ JSUList<Z2CreatureEnemy> field_0x0;
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     /* 0x0C */ JSUList<Z2SoundObjBase> allList_;
     #endif
     /* 0x0C */ Z2EnemyArea enemyArea_;
diff --git a/include/Z2AudioLib/Z2SoundObject.h b/include/Z2AudioLib/Z2SoundObject.h
index ca4b69a520..2d85db34c0 100644
--- a/include/Z2AudioLib/Z2SoundObject.h
+++ b/include/Z2AudioLib/Z2SoundObject.h
@@ -7,7 +7,7 @@
 struct Z2SoundStarter;
 
 class Z2SoundObjBase : public Z2SoundHandles
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
 , public JSULink<Z2SoundObjBase>
 #endif
 {
diff --git a/include/d/d_attention.h b/include/d/d_attention.h
index 455516e54f..5b8930b5dd 100644
--- a/include/d/d_attention.h
+++ b/include/d/d_attention.h
@@ -45,7 +45,7 @@ private:
 
 class dAttParam_c : public JORReflexible {
 public:
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x04 */ s8 mHIOChildNo;
 #endif
 
@@ -66,7 +66,7 @@ public:
     /* 0x35 */ u8 mAttnCursorDisappearFrames;
     /* 0x38 */ f32 field_0x38;
     /* 0x3C */ f32 field_0x3c;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x44 */ s32 mDebugDispPosX;
     /* 0x48 */ s32 mDebugDispPosY;
 #endif
diff --git a/include/d/d_bg_s_acch.h b/include/d/d_bg_s_acch.h
index 33bca24c0a..04a388c61b 100644
--- a/include/d/d_bg_s_acch.h
+++ b/include/d/d_bg_s_acch.h
@@ -201,7 +201,7 @@ private:
     /* 0x02C */ u32 m_flags;
     /* 0x030 */ cXyz* pm_pos;
     /* 0x034 */ cXyz* pm_old_pos;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x038 */ cXyz unk_0x38;
 #endif
     /* 0x038 */ cXyz* pm_speed;
@@ -229,7 +229,7 @@ private:
     /* 0x0CC */ f32 field_0xcc;
     /* 0x0D0 */ f32 m_wtr_chk_offset;
     /* 0x0D4 */ cBgS_PolyInfo* pm_out_poly_info;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x0E4 */ cXyz unk_0xe4;
 #endif
     /* 0x0D8 */ f32 field_0xd8;
diff --git a/include/d/d_cc_s.h b/include/d/d_cc_s.h
index b4d90787ae..d156867cce 100644
--- a/include/d/d_cc_s.h
+++ b/include/d/d_cc_s.h
@@ -79,7 +79,7 @@ public:
 
     // /* 0x0000 */ cCcS mCCcS;
     /* 0x284C */ dCcMassS_Mng mMass_Mng;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x2AD0 */ u8 m_is_mass_all_timer;
 #endif
 };  // Size = 0x2AC4
diff --git a/include/d/d_com_inf_game.h b/include/d/d_com_inf_game.h
index fbc9964ca2..d240507f97 100644
--- a/include/d/d_com_inf_game.h
+++ b/include/d/d_com_inf_game.h
@@ -1037,7 +1037,7 @@ public:
     /* 0x1DE09 */ u8 field_0x1de09;
     /* 0x1DE0A */ u8 field_0x1de0a;
     /* 0x1DE0B */ u8 mIsDebugMode;
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     /* 0x1DE0C */ OSStopwatch mStopwatch;
     #endif
 
diff --git a/include/d/d_event_manager.h b/include/d/d_event_manager.h
index 03a8ef7ac3..de046797ff 100644
--- a/include/d/d_event_manager.h
+++ b/include/d/d_event_manager.h
@@ -41,7 +41,7 @@ public:
         BASE_ROOM5,
         BASE_DEMO,
 
-        #if DEBUG
+        #if PARTIAL_DEBUG || DEBUG
         BASE_DEBUG,
         #endif
 
diff --git a/include/d/d_kankyo.h b/include/d/d_kankyo.h
index 3c81f08d10..06c8f0eb56 100644
--- a/include/d/d_kankyo.h
+++ b/include/d/d_kankyo.h
@@ -259,7 +259,7 @@ public:
     /* 0x09B8 */ DUNGEON_LIGHT dungeonlight[8];
     /* 0x0C18 */ BOSS_LIGHT field_0x0c18[8];
     /* 0x0D58 */ BOSS_LIGHT field_0x0d58[6];
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x0E48 */ NAVYCHAN navy;
     /* 0x0E58 */ u8 field_0xe58[0xE68 - 0xE58];  // part of NAVYCHAN?
 #endif
diff --git a/include/d/d_particle.h b/include/d/d_particle.h
index c9db174fcd..3098dbd521 100644
--- a/include/d/d_particle.h
+++ b/include/d/d_particle.h
@@ -521,13 +521,13 @@ private:
     /* 0x019 */ u8 field_0x19;
     /* 0x01A */ u8 field_0x1a;
     /* 0x01B */ u8 field_0x1b;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x01C */ dPa_simpleEcallBack field_0x1c[48];
 #else
     /* 0x01C */ dPa_simpleEcallBack field_0x1c[25];
 #endif
     /* 0x210 */ level_c field_0x210;
-    #if DEBUG
+    #if PARTIAL_DEBUG || DEBUG
     u8 mSceneCount;
     #endif
 };
diff --git a/include/d/d_resorce.h b/include/d/d_resorce.h
index 31d028a082..b70d2d5452 100644
--- a/include/d/d_resorce.h
+++ b/include/d/d_resorce.h
@@ -59,7 +59,7 @@ private:
     /* 0x18 */ JKRHeap* heap;
     /* 0x1C */ JKRSolidHeap* mDataHeap;
     /* 0x20 */ void** mRes;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x24 */ int mSize;
 #endif
 };  // Size: 0x24
diff --git a/include/d/d_save.h b/include/d/d_save.h
index 69d4d3174d..fc54e541f4 100644
--- a/include/d/d_save.h
+++ b/include/d/d_save.h
@@ -1008,7 +1008,7 @@ public:
 
     static const int ZONE_MAX = 0x20;
 
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x000 */ u8 unk_0x0;
     /* 0x001 */ char unk_0x1;
     /* 0x000 */ u8 unk_0x2[0x48 - 0x2];
@@ -1029,6 +1029,9 @@ public:
     /* 0xF30 */ s64 mSaveTotalTime;
 #if DEBUG
     /* 0xF80 */ flagFile_c mFlagFile;
+#elif PARTIAL_DEBUG
+    // flagFile_c's ctor/virtuals are only defined under #if DEBUG (d_save.cpp)
+    alignas(flagFile_c) u8 mFlagFile[sizeof(flagFile_c)];
 #endif
 };  // Size: 0xF38
 
diff --git a/include/d/d_stage.h b/include/d/d_stage.h
index 04a6115fd0..83a1c808fd 100644
--- a/include/d/d_stage.h
+++ b/include/d/d_stage.h
@@ -538,7 +538,7 @@ public:
     /* vt[86] */ virtual stage_tgsc_class* getDrTg(void) const = 0;
     /* vt[87] */ virtual void setDoor(stage_tgsc_class*) = 0;
     /* vt[88] */ virtual stage_tgsc_class* getDoor(void) const = 0;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     virtual void setUnit(void*) = 0;
     virtual void* getUnit() = 0;
 #endif
@@ -796,7 +796,7 @@ public:
     virtual stage_tgsc_class* getDrTg(void) const { return mDrTg; }
     virtual void setDoor(stage_tgsc_class* i_Door) { mDoor = i_Door; }
     virtual stage_tgsc_class* getDoor(void) const { return mDoor; }
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     virtual void setUnit(void* i_Unit) { mUnit = i_Unit; }
     virtual void* getUnit() { return mUnit; }
 #endif
@@ -845,7 +845,7 @@ public:
     /* 0x54 */ stage_tgsc_class* mDrTg;
     /* 0x58 */ stage_tgsc_class* mDoor;
     /* 0x5C */ dStage_FloorInfo_c* mFloorInfo;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x60 */ void* mUnit;
 #endif
     /* 0x60 */ u16 mPlayerNum;
@@ -990,7 +990,7 @@ public:
     /* vt[86] */ virtual stage_tgsc_class* getDrTg(void) const { return mDrTg; }
     /* vt[87] */ virtual void setDoor(stage_tgsc_class* i_Door) { mDoor = i_Door; }
     /* vt[88] */ virtual stage_tgsc_class* getDoor(void) const { return mDoor; }
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     virtual void setUnit(void* i_Unit) {
         UNUSED(i_Unit);
         OSReport("stage non unit list data !!\n");
diff --git a/include/d/d_vibration.h b/include/d/d_vibration.h
index 4018acea50..ee87f7dcc4 100644
--- a/include/d/d_vibration.h
+++ b/include/d/d_vibration.h
@@ -97,6 +97,9 @@ public:
 private:
 #if DEBUG
     /* 0x00 */ dVibTest_c mVibTest;
+#elif PARTIAL_DEBUG
+    // dVibTest_c's ctor/virtuals are only defined under #if DEBUG (d_vibration.cpp)
+    alignas(dVibTest_c) u8 mVibTest[sizeof(dVibTest_c)];
 #endif
 
     class {
diff --git a/include/f_pc/f_pc_node_req.h b/include/f_pc/f_pc_node_req.h
index d710379c89..880e733ac9 100644
--- a/include/f_pc/f_pc_node_req.h
+++ b/include/f_pc/f_pc_node_req.h
@@ -36,7 +36,7 @@ typedef struct node_create_request {
     /* 0x58 */ s16 name;
     /* 0x5C */ void* data;
     /* 0x60 */ s16 unk_0x60;
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     /* 0x64 */ int unk_0x64;
     /* 0x68 */ int unk_0x68;
 #endif
diff --git a/include/m_Do/m_Do_audio.h b/include/m_Do/m_Do_audio.h
index 4bc2f20c94..e1e15c1ef1 100644
--- a/include/m_Do/m_Do_audio.h
+++ b/include/m_Do/m_Do_audio.h
@@ -11,13 +11,13 @@ class mDoAud_zelAudio_c : public Z2AudioMgr {
 public:
     void reset();
     mDoAud_zelAudio_c() {
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
         setMode(2);
 #endif
     }
     ~mDoAud_zelAudio_c() {}
 
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
     u8 getMode() { return field_0x13bd; }
     void setMode(u8 mode) { field_0x13bd = mode; }
 
diff --git a/include/m_Do/m_Do_hostIO.h b/include/m_Do/m_Do_hostIO.h
index fa4eb8b1af..d88a0a9853 100644
--- a/include/m_Do/m_Do_hostIO.h
+++ b/include/m_Do/m_Do_hostIO.h
@@ -35,6 +35,11 @@ public:
     /* 0x4 */ s8 mNo;
     /* 0x5 */ u8 mCount;
 #else
+#if PARTIAL_DEBUG
+    // Initialized here since the DEBUG ctor doesn't run.
+    /* 0x4 */ s8 mNo = -1;
+    /* 0x5 */ u8 mCount = 0;
+#endif
     virtual ~mDoHIO_entry_c() {}
 #endif
 };
diff --git a/libs/JSystem/include/JSystem/JHostIO/JORReflexible.h b/libs/JSystem/include/JSystem/JHostIO/JORReflexible.h
index 533a3184ba..84894de275 100644
--- a/libs/JSystem/include/JSystem/JHostIO/JORReflexible.h
+++ b/libs/JSystem/include/JSystem/JHostIO/JORReflexible.h
@@ -12,12 +12,23 @@ struct JORNodeEvent;
 class JORMContext;
 class JORServer;
 
+// NOTE (stable game ABI): these classes stay non-polymorphic outside DEBUG
+// on purpose. Making them polymorphic under PARTIAL_DEBUG would give every one of the ~250
+// derived HIO classes a vptr and turn their plain `void genMessage(JORMContext*);`
+// declarations into implicit virtual overrides whose definitions are #if DEBUG-gated; every
+// instantiated one then fails to link (missing vtable). Closure types shared with DEBUG TUs
+// either declare their own unconditional virtuals (vptr in all TUs anyway) or add a
+// PARTIAL_DEBUG-only virtual dtor for vptr parity (see dAttParam_c).
 class JOREventListener {
 public:
 #if DEBUG
     JOREventListener() {}
+#if TARGET_PC
+    virtual void listenPropertyEvent(const JORPropertyEvent*) {}
+#else
     virtual void listenPropertyEvent(const JORPropertyEvent*) = 0;
 #endif
+#endif
 };
 
 class JORReflexible : public JOREventListener {
@@ -30,7 +41,11 @@ public:
     virtual void listenPropertyEvent(const JORPropertyEvent*);
     virtual void listen(u32, const JOREvent*);
     virtual void genObjectInfo(const JORGenEvent*);
+#if TARGET_PC
+    virtual void genMessage(JORMContext*) {}
+#else
     virtual void genMessage(JORMContext*) = 0;
+#endif
     virtual void listenNodeEvent(const JORNodeEvent*);
 #endif
 };
diff --git a/libs/JSystem/include/JSystem/JStudio/JStudio/functionvalue.h b/libs/JSystem/include/JSystem/JStudio/JStudio/functionvalue.h
index 7b2c935272..8acdbe1623 100644
--- a/libs/JSystem/include/JSystem/JStudio/JStudio/functionvalue.h
+++ b/libs/JSystem/include/JSystem/JStudio/JStudio/functionvalue.h
@@ -314,7 +314,7 @@ public:
         >
     {
         TIterator_data_(const TFunctionValue_list_parameter& rParent, const f32* value) {
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
             pOwn_ = &rParent;
 #endif
             pf_ = value;
@@ -372,7 +372,7 @@ public:
             return (r1.pf_ - r2.pf_) / suData_size;
         }
 
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
         /* 0x00 */ const TFunctionValue_list_parameter* pOwn_;
 #endif
         /* 0x00 */ const f32* pf_;
@@ -425,7 +425,7 @@ public:
         >
     {
         TIterator_data_(const TFunctionValue_hermite& rParent, const f32* value) {
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
             pOwn_ = &rParent;
 #endif
             pf_ = value;
@@ -491,7 +491,7 @@ public:
             return (r1.pf_ - r2.pf_) / r1.uSize_;
         }
 
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
         /* 0x00 */ const TFunctionValue_hermite* pOwn_;
         /* 0x04 */ const f32* pf_;
         /* 0x08 */ u32 uSize_;
diff --git a/src/Z2AudioLib/Z2SoundObject.cpp b/src/Z2AudioLib/Z2SoundObject.cpp
index 1c81be0f17..23e8171736 100644
--- a/src/Z2AudioLib/Z2SoundObject.cpp
+++ b/src/Z2AudioLib/Z2SoundObject.cpp
@@ -22,7 +22,7 @@
 #include "os_report.h"
 
 Z2SoundObjBase::Z2SoundObjBase()
-#if DEBUG
+#if PARTIAL_DEBUG || DEBUG
 : JSULink<Z2SoundObjBase>(this)
 #endif
 {