diff --git a/enzyme/Enzyme/CApi.cpp b/enzyme/Enzyme/CApi.cpp
index 209e3d3a02c4..081a665d80cf 100644
--- a/enzyme/Enzyme/CApi.cpp
+++ b/enzyme/Enzyme/CApi.cpp
@@ -23,6 +23,7 @@
 //===----------------------------------------------------------------------===//
 #include "CApi.h"
 #include "EnzymeLogic.h"
+#include "LibraryFuncs.h"
 #include "SCEV/TargetLibraryInfo.h"
 
 #include "llvm/ADT/Triple.h"
@@ -184,6 +185,23 @@ void FreeTypeAnalysis(EnzymeTypeAnalysisRef TAR) {
   delete TA;
 }
 
+void EnzymeRegisterAllocationHandler(char *Name, CustomShadowAlloc AHandle,
+                                     CustomShadowFree FHandle) {
+  shadowHandlers[std::string(Name)] =
+      [=](IRBuilder<> &B, CallInst *CI,
+          ArrayRef<Value *> Args) -> llvm::Value * {
+    SmallVector<LLVMValueRef, 3> refs;
+    for (auto a : Args)
+      refs.push_back(wrap(a));
+    return unwrap(AHandle(wrap(&B), wrap(CI), Args.size(), refs.data()));
+  };
+  shadowErasers[std::string(Name)] = [=](IRBuilder<> &B, Value *ToFree,
+                                         Function *AllocF) -> llvm::CallInst * {
+    return cast_or_null<CallInst>(
+        unwrap(FHandle(wrap(&B), wrap(ToFree), wrap(AllocF))));
+  };
+}
+
 LLVMValueRef EnzymeCreatePrimalAndGradient(
     LLVMValueRef todiff, CDIFFE_TYPE retType, CDIFFE_TYPE *constant_args,
     size_t constant_args_size, EnzymeTypeAnalysisRef TA,
diff --git a/enzyme/Enzyme/CApi.h b/enzyme/Enzyme/CApi.h
index c32ac6bc70ec..7ff0f54eb4a7 100644
--- a/enzyme/Enzyme/CApi.h
+++ b/enzyme/Enzyme/CApi.h
@@ -145,6 +145,14 @@ LLVMValueRef
 EnzymeExtractFunctionFromAugmentation(EnzymeAugmentedReturnPtr ret);
 LLVMTypeRef EnzymeExtractTapeTypeFromAugmentation(EnzymeAugmentedReturnPtr ret);
 
+typedef LLVMValueRef (*CustomShadowAlloc)(LLVMBuilderRef, LLVMValueRef,
+                                          size_t /*numArgs*/, LLVMValueRef *);
+typedef LLVMValueRef (*CustomShadowFree)(LLVMBuilderRef, LLVMValueRef,
+                                         LLVMValueRef);
+
+void EnzymeRegisterAllocationHandler(char *Name, CustomShadowAlloc AHandle,
+                                     CustomShadowFree FHandle);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/enzyme/Enzyme/GradientUtils.cpp b/enzyme/Enzyme/GradientUtils.cpp
index bed206d826d7..0c6ab462c27b 100644
--- a/enzyme/Enzyme/GradientUtils.cpp
+++ b/enzyme/Enzyme/GradientUtils.cpp
@@ -45,6 +45,13 @@
 
 #include <algorithm>
 
+std::map<std::string, std::function<llvm::Value *(IRBuilder<> &, CallInst *,
+                                                  ArrayRef<Value *>)>>
+    shadowHandlers;
+std::map<std::string,
+         std::function<llvm::CallInst *(IRBuilder<> &, Value *, Function *)>>
+    shadowErasers;
+
 llvm::cl::opt<bool>
     EnzymeNewCache("enzyme-new-cache", cl::init(true), cl::Hidden,
                    cl::desc("Use new cache decision algorithm"));
diff --git a/enzyme/Enzyme/GradientUtils.h b/enzyme/Enzyme/GradientUtils.h
index 6c2b1ae44526..499fee6cea62 100644
--- a/enzyme/Enzyme/GradientUtils.h
+++ b/enzyme/Enzyme/GradientUtils.h
@@ -73,6 +73,12 @@ using namespace llvm;
 
 enum class DerivativeMode { Forward, Reverse, Both };
 
+#include "llvm-c/Core.h"
+
+extern std::map<std::string, std::function<llvm::Value *(
+                                 IRBuilder<> &, CallInst *, ArrayRef<Value *>)>>
+    shadowHandlers;
+
 static inline std::string to_string(DerivativeMode mode) {
   switch (mode) {
   case DerivativeMode::Forward:
@@ -525,6 +531,22 @@ class GradientUtils : public CacheUtility {
     for (unsigned i = 0; i < orig->getNumArgOperands(); ++i) {
       args.push_back(getNewFromOriginal(orig->getArgOperand(i)));
     }
+
+    if (shadowHandlers.find(orig->getCalledFunction()->getName().str()) !=
+        shadowHandlers.end()) {
+      Value *anti = shadowHandlers[orig->getCalledFunction()->getName().str()](
+          bb, orig, args);
+      invertedPointers[orig] = anti;
+      // assert(placeholder != anti);
+      bb.SetInsertPoint(placeholder->getNextNode());
+      replaceAWithB(placeholder, anti);
+      erase(placeholder);
+
+      anti = cacheForReverse(bb, anti, idx);
+      invertedPointers[orig] = anti;
+      return anti;
+    }
+
     Value *anti =
         bb.CreateCall(orig->getCalledFunction(), args, orig->getName() + "'mi");
     cast<CallInst>(anti)->setAttributes(orig->getAttributes());
@@ -575,16 +597,22 @@ class GradientUtils : public CacheUtility {
                       *orig);
         }
       }
-      auto dst_arg = bb.CreateBitCast(
-          anti, Type::getInt8PtrTy(orig->getContext(),
-                                   anti->getType()->getPointerAddressSpace()));
+
+      Value *dst_arg = anti;
+
+      dst_arg = bb.CreateBitCast(
+          dst_arg,
+          Type::getInt8PtrTy(orig->getContext(),
+                             anti->getType()->getPointerAddressSpace()));
+
       auto val_arg = ConstantInt::get(Type::getInt8Ty(orig->getContext()), 0);
       Value *size;
       // todo check if this memset is legal and if a write barrier is needed
-      if (orig->getCalledFunction()->getName() == "julia.gc_alloc_obj")
+      if (orig->getCalledFunction()->getName() == "julia.gc_alloc_obj") {
         size = args[1];
-      else
+      } else {
         size = args[0];
+      }
       auto len_arg =
           bb.CreateZExtOrTrunc(size, Type::getInt64Ty(orig->getContext()));
       auto volatile_arg = ConstantInt::getFalse(orig->getContext());
diff --git a/enzyme/Enzyme/LibraryFuncs.h b/enzyme/Enzyme/LibraryFuncs.h
index ce00580ac1bf..25ec662f346e 100644
--- a/enzyme/Enzyme/LibraryFuncs.h
+++ b/enzyme/Enzyme/LibraryFuncs.h
@@ -28,6 +28,15 @@
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 
+extern std::map<std::string, std::function<llvm::Value *(
+                                 llvm::IRBuilder<> &, llvm::CallInst *,
+                                 llvm::ArrayRef<llvm::Value *>)>>
+    shadowHandlers;
+extern std::map<std::string,
+                std::function<llvm::CallInst *(
+                    llvm::IRBuilder<> &, llvm::Value *, llvm::Function *)>>
+    shadowErasers;
+
 /// Return whether a given function is a known C/C++ memory allocation function
 /// For updating below one should read MemoryBuiltins.cpp, TargetLibraryInfo.cpp
 static inline bool isAllocationFunction(const llvm::Function &F,
@@ -38,6 +47,9 @@ static inline bool isAllocationFunction(const llvm::Function &F,
     return true;
   if (F.getName() == "julia.gc_alloc_obj")
     return true;
+  if (shadowHandlers.find(F.getName().str()) != shadowHandlers.end())
+    return true;
+
   using namespace llvm;
   llvm::LibFunc libfunc;
   if (!TLI.getLibFunc(F, libfunc))
@@ -193,8 +205,12 @@ freeKnownAllocation(llvm::IRBuilder<> &builder, llvm::Value *tofree,
       allocationfn.getName() == "__rust_alloc_zeroed") {
     llvm_unreachable("todo - hook in rust allocation fns");
   }
-  if (allocationfn.getName() == "julia.gc_alloc_obj") {
+  if (allocationfn.getName() == "julia.gc_alloc_obj")
     return nullptr;
+
+  if (shadowErasers.find(allocationfn.getName().str()) != shadowErasers.end()) {
+    return shadowErasers[allocationfn.getName().str()](builder, tofree,
+                                                       &allocationfn);
   }
 
   llvm::LibFunc libfunc;
diff --git a/enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp b/enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp
index 8fcbbad88051..bb85fb8e7e46 100644
--- a/enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp
+++ b/enzyme/Enzyme/TypeAnalysis/TypeAnalysis.cpp
@@ -2500,26 +2500,7 @@ void TypeAnalyzer::visitCallInst(CallInst &call) {
     analyzeFuncTypes<__VA_ARGS__>(::fn, call, *this);                          \
     return;                                                                    \
   }
-    // All these are always valid => no direction check
-    // CONSIDER(malloc)
-    // TODO consider handling other allocation functions integer inputs
-    if (isAllocationFunction(*ci, interprocedural.TLI)) {
-      size_t Idx = 0;
-      for (auto &Arg : ci->args()) {
-        if (Arg.getType()->isIntegerTy()) {
-          updateAnalysis(call.getOperand(Idx),
-                         TypeTree(BaseType::Integer).Only(-1), &call);
-        }
-        Idx++;
-      }
-      assert(ci->getReturnType()->isPointerTy());
-      updateAnalysis(&call, TypeTree(BaseType::Pointer).Only(-1), &call);
-      return;
-    }
-    if (ci->getName().startswith("_ZN3std2io5stdio6_print") ||
-        ci->getName().startswith("_ZN4core3fmt")) {
-      return;
-    }
+
     auto customrule = interprocedural.CustomRules.find(ci->getName().str());
     if (customrule != interprocedural.CustomRules.end()) {
       auto returnAnalysis = getAnalysis(&call);
@@ -2544,6 +2525,26 @@ void TypeAnalyzer::visitCallInst(CallInst &call) {
       }
       return;
     }
+    // All these are always valid => no direction check
+    // CONSIDER(malloc)
+    // TODO consider handling other allocation functions integer inputs
+    if (isAllocationFunction(*ci, interprocedural.TLI)) {
+      size_t Idx = 0;
+      for (auto &Arg : ci->args()) {
+        if (Arg.getType()->isIntegerTy()) {
+          updateAnalysis(call.getOperand(Idx),
+                         TypeTree(BaseType::Integer).Only(-1), &call);
+        }
+        Idx++;
+      }
+      assert(ci->getReturnType()->isPointerTy());
+      updateAnalysis(&call, TypeTree(BaseType::Pointer).Only(-1), &call);
+      return;
+    }
+    if (ci->getName().startswith("_ZN3std2io5stdio6_print") ||
+        ci->getName().startswith("_ZN4core3fmt")) {
+      return;
+    }
     /// MPI
     if (ci->getName() == "MPI_Init") {
       TypeTree ptrint;