diff --git a/toolchain/check/cpp/export.cpp b/toolchain/check/cpp/export.cpp
index 7813e6037957..75764ff508e3 100644
--- a/toolchain/check/cpp/export.cpp
+++ b/toolchain/check/cpp/export.cpp
@@ -1144,14 +1144,8 @@ auto ExportFunctionSpecializationToCpp(
   auto bindings = context.inst_blocks().Get(generic.bindings_id);
   CARBON_CHECK(bindings.size() == template_args.size());
 
-  // This name will be appended to the thunk name to disambiguate
-  // between specializations.
-  std::string extra_name;
-
   // Map the `clang::TemplateArgument`s into Carbon types suitable for
   // passing into `MakeSpecific`.
-  //
-  // Also initialize `extra_name`.
   llvm::SmallVector<SemIR::InstId> specific_arg_ids;
   for (auto [binding_inst_id, clang_template_arg] :
        llvm::zip(bindings, template_args)) {
@@ -1165,9 +1159,6 @@ auto ExportFunctionSpecializationToCpp(
       return false;
     }
 
-    // TODO: this generates a pretty ugly name.
-    extra_name += std::string(llvm::formatv("{}", type_expr.inst_id));
-
     auto binding_const_inst_id =
         context.constant_values().GetConstantInstId(binding_inst_id);
 
@@ -1180,6 +1171,11 @@ auto ExportFunctionSpecializationToCpp(
   // parameters with symbolic types to concrete types.
   auto specific_id = MakeSpecific(context, loc_id, target.function.generic_id,
                                   specific_arg_ids);
+  // This name is appended to the thunk name to disambiguate between
+  // specializations.
+  SemIR::Mangler m(context.sem_ir(), context.total_ir_count(),
+                   context.mangle_string_fingerprint());
+  auto extra_name = m.MangleSpecificId(specific_id);
   target.return_type_id =
       target.function.GetDeclaredReturnType(context.sem_ir(), specific_id);
   for (auto& param : target.explicit_params) {
diff --git a/toolchain/check/testdata/interop/cpp/function/export/generic.carbon b/toolchain/check/testdata/interop/cpp/function/export/generic.carbon
index fc793f4e5349..a14042e95617 100644
--- a/toolchain/check/testdata/interop/cpp/function/export/generic.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/export/generic.carbon
@@ -486,14 +486,14 @@ void G() {
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @F__carbon_thunkinst64000043(%_.param.loc24_23.1: ref %A, %_.param.loc24_23.2: ref %A) {
+// CHECK:STDOUT: fn @F__carbon_thunk.83afdff581006d1a(%_.param.loc24_23.1: ref %A, %_.param.loc24_23.2: ref %A) {
 // CHECK:STDOUT: !entry:
-// CHECK:STDOUT:   %F__carbon_thunkinst64000043.ref: %F.type = name_ref F__carbon_thunkinst64000043, file.%F.decl [concrete = constants.%F]
+// CHECK:STDOUT:   %F__carbon_thunk.83afdff581006d1a.ref: %F.type = name_ref F__carbon_thunk.83afdff581006d1a, file.%F.decl [concrete = constants.%F]
 // CHECK:STDOUT:   %I.facet.loc24_23.1: %I.type = facet_value constants.%A, (constants.%I.impl_witness.6ad) [concrete = constants.%I.facet.64b]
 // CHECK:STDOUT:   %.loc24_23.1: %I.type = converted constants.%A, %I.facet.loc24_23.1 [concrete = constants.%I.facet.64b]
 // CHECK:STDOUT:   %I.facet.loc24_23.2: %I.type = facet_value constants.%A, (constants.%I.impl_witness.6ad) [concrete = constants.%I.facet.64b]
 // CHECK:STDOUT:   %.loc24_23.2: %I.type = converted constants.%A, %I.facet.loc24_23.2 [concrete = constants.%I.facet.64b]
-// CHECK:STDOUT:   %F.specific_fn: <specific function> = specific_function %F__carbon_thunkinst64000043.ref, @F(constants.%I.facet.64b) [concrete = constants.%F.specific_fn.f33]
+// CHECK:STDOUT:   %F.specific_fn: <specific function> = specific_function %F__carbon_thunk.83afdff581006d1a.ref, @F(constants.%I.facet.64b) [concrete = constants.%F.specific_fn.f33]
 // CHECK:STDOUT:   %.loc24_23.3: ref %A = splice_block %_.param.loc24_23.2 {}
 // CHECK:STDOUT:   %.loc24_23.4: %A = acquire_value %_.param.loc24_23.1
 // CHECK:STDOUT:   %F.call: init %A to %.loc24_23.3 = call %F.specific_fn(%.loc24_23.4)
@@ -501,14 +501,14 @@ void G() {
 // CHECK:STDOUT:   return
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @F__carbon_thunkinst6400006E(%_.param.loc24_23.1: ref %B, %_.param.loc24_23.2: ref %B) {
+// CHECK:STDOUT: fn @F__carbon_thunk.36f470e96b413347(%_.param.loc24_23.1: ref %B, %_.param.loc24_23.2: ref %B) {
 // CHECK:STDOUT: !entry:
-// CHECK:STDOUT:   %F__carbon_thunkinst6400006E.ref: %F.type = name_ref F__carbon_thunkinst6400006E, file.%F.decl [concrete = constants.%F]
+// CHECK:STDOUT:   %F__carbon_thunk.36f470e96b413347.ref: %F.type = name_ref F__carbon_thunk.36f470e96b413347, file.%F.decl [concrete = constants.%F]
 // CHECK:STDOUT:   %I.facet.loc24_23.1: %I.type = facet_value constants.%B, (constants.%I.impl_witness.5b8) [concrete = constants.%I.facet.9f8]
 // CHECK:STDOUT:   %.loc24_23.1: %I.type = converted constants.%B, %I.facet.loc24_23.1 [concrete = constants.%I.facet.9f8]
 // CHECK:STDOUT:   %I.facet.loc24_23.2: %I.type = facet_value constants.%B, (constants.%I.impl_witness.5b8) [concrete = constants.%I.facet.9f8]
 // CHECK:STDOUT:   %.loc24_23.2: %I.type = converted constants.%B, %I.facet.loc24_23.2 [concrete = constants.%I.facet.9f8]
-// CHECK:STDOUT:   %F.specific_fn: <specific function> = specific_function %F__carbon_thunkinst6400006E.ref, @F(constants.%I.facet.9f8) [concrete = constants.%F.specific_fn.db2]
+// CHECK:STDOUT:   %F.specific_fn: <specific function> = specific_function %F__carbon_thunk.36f470e96b413347.ref, @F(constants.%I.facet.9f8) [concrete = constants.%F.specific_fn.db2]
 // CHECK:STDOUT:   %.loc24_23.3: ref %B = splice_block %_.param.loc24_23.2 {}
 // CHECK:STDOUT:   %.loc24_23.4: %B = acquire_value %_.param.loc24_23.1
 // CHECK:STDOUT:   %F.call: init %B to %.loc24_23.3 = call %F.specific_fn(%.loc24_23.4)
diff --git a/toolchain/lower/testdata/interop/cpp/function/export/generic.carbon b/toolchain/lower/testdata/interop/cpp/function/export/generic.carbon
index a7aca55cfcb7..f0bd2f44e78d 100644
--- a/toolchain/lower/testdata/interop/cpp/function/export/generic.carbon
+++ b/toolchain/lower/testdata/interop/cpp/function/export/generic.carbon
@@ -132,7 +132,7 @@ fn Run() {
 // CHECK:STDOUT: define internal void @_ZN6CarbonL1FENS_1AE() #2 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %0 = alloca %"class.Carbon::A", align 1
-// CHECK:STDOUT:   call void @_CF__carbon_thunkinst70000035.Main(ptr noundef nonnull align 1 %0)
+// CHECK:STDOUT:   call void @_CF__carbon_thunk.83afdff581006d1a.Main(ptr noundef nonnull align 1 %0)
 // CHECK:STDOUT:   ret void
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -152,7 +152,7 @@ fn Run() {
 // CHECK:STDOUT: define internal void @_ZN6CarbonL1FENS_1BE() #2 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %0 = alloca %"class.Carbon::B", align 1
-// CHECK:STDOUT:   call void @_CF__carbon_thunkinst70000052.Main(ptr noundef nonnull align 1 %0)
+// CHECK:STDOUT:   call void @_CF__carbon_thunk.36f470e96b413347.Main(ptr noundef nonnull align 1 %0)
 // CHECK:STDOUT:   ret void
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -208,14 +208,14 @@ fn Run() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF__carbon_thunkinst70000035.Main(ptr %_) #4 !dbg !44 {
+// CHECK:STDOUT: define void @_CF__carbon_thunk.83afdff581006d1a.Main(ptr %_) #4 !dbg !44 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_CF.Main.3e1f7ed08cd9ee58(ptr %_), !dbg !47
 // CHECK:STDOUT:   ret void, !dbg !47
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
-// CHECK:STDOUT: define void @_CF__carbon_thunkinst70000052.Main(ptr %_) #4 !dbg !48 {
+// CHECK:STDOUT: define void @_CF__carbon_thunk.36f470e96b413347.Main(ptr %_) #4 !dbg !48 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_CF.Main.bd1b6d59f703c190(ptr %_), !dbg !51
 // CHECK:STDOUT:   ret void, !dbg !51
@@ -303,11 +303,11 @@ fn Run() {
 // CHECK:STDOUT: !41 = !{!42}
 // CHECK:STDOUT: !42 = !DILocalVariable(arg: 1, scope: !40, type: !20)
 // CHECK:STDOUT: !43 = !DILocation(line: 13, column: 1, scope: !40)
-// CHECK:STDOUT: !44 = distinct !DISubprogram(name: "F__carbon_thunkinst70000035", linkageName: "_CF__carbon_thunkinst70000035.Main", scope: null, file: !1, line: 19, type: !18, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !45)
+// CHECK:STDOUT: !44 = distinct !DISubprogram(name: "F__carbon_thunk.83afdff581006d1a", linkageName: "_CF__carbon_thunk.83afdff581006d1a.Main", scope: null, file: !1, line: 19, type: !18, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !45)
 // CHECK:STDOUT: !45 = !{!46}
 // CHECK:STDOUT: !46 = !DILocalVariable(arg: 1, scope: !44, type: !20)
 // CHECK:STDOUT: !47 = !DILocation(line: 19, column: 1, scope: !44)
-// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "F__carbon_thunkinst70000052", linkageName: "_CF__carbon_thunkinst70000052.Main", scope: null, file: !1, line: 19, type: !18, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !49)
+// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "F__carbon_thunk.36f470e96b413347", linkageName: "_CF__carbon_thunk.36f470e96b413347.Main", scope: null, file: !1, line: 19, type: !18, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !49)
 // CHECK:STDOUT: !49 = !{!50}
 // CHECK:STDOUT: !50 = !DILocalVariable(arg: 1, scope: !48, type: !20)
 // CHECK:STDOUT: !51 = !DILocation(line: 19, column: 1, scope: !48)
diff --git a/toolchain/sem_ir/mangler.cpp b/toolchain/sem_ir/mangler.cpp
index d47f641c5770..e342b736d6d8 100644
--- a/toolchain/sem_ir/mangler.cpp
+++ b/toolchain/sem_ir/mangler.cpp
@@ -344,6 +344,12 @@ auto Mangler::MangleVTable(const SemIR::Class& class_info,
   return os.TakeStr();
 }
 
+auto Mangler::MangleSpecificId(SemIR::SpecificId specific_id) -> std::string {
+  RawStringOstream os;
+  MangleSpecificId(os, specific_id);
+  return os.TakeStr();
+}
+
 auto Mangler::MangleUnqualifiedName(llvm::raw_ostream& os,
                                     const SemIR::EntityWithParamsBase& entity,
                                     SemIR::SpecificId specific_id) -> void {
diff --git a/toolchain/sem_ir/mangler.h b/toolchain/sem_ir/mangler.h
index ec7523942dec..99a036a442ee 100644
--- a/toolchain/sem_ir/mangler.h
+++ b/toolchain/sem_ir/mangler.h
@@ -49,6 +49,9 @@ class Mangler {
   auto MangleVTable(const SemIR::Class& class_info,
                     SemIR::SpecificId specific_id) -> std::string;
 
+  // Produce a deterministically unique mangled name for a specific.
+  auto MangleSpecificId(SemIR::SpecificId specific_id) -> std::string;
+
  private:
   auto MangleImpl(SemIR::FunctionId function_id, SemIR::SpecificId specific_id,
                   llvm::raw_ostream& os) -> void;