diff --git a/src/V3Active.cpp b/src/V3Active.cpp
index 68ef3dbf1..2ad8a1a8f 100644
--- a/src/V3Active.cpp
+++ b/src/V3Active.cpp
@@ -68,7 +68,7 @@ public:
         : V3GraphVertex{graphp}
         , m_name{name}
         , m_type{type} {}
-    string name() const override { return m_name + " " + typestr(); }
+    string name() const override VL_MT_STABLE { return m_name + " " + typestr(); }
     string dotColor() const override { return user() ? "green" : "black"; }
     virtual int type() const { return m_type; }
 };
diff --git a/src/V3Ast.cpp b/src/V3Ast.cpp
index 86e89fac3..c60db662f 100644
--- a/src/V3Ast.cpp
+++ b/src/V3Ast.cpp
@@ -125,7 +125,9 @@ string AstNode::encodeNumber(int64_t num) {
     }
 }
 
-string AstNode::nameProtect() const { return VIdProtect::protectIf(name(), protect()); }
+string AstNode::nameProtect() const VL_MT_STABLE {
+    return VIdProtect::protectIf(name(), protect());
+}
 string AstNode::origNameProtect() const { return VIdProtect::protectIf(origName(), protect()); }
 
 string AstNode::shortName() const {
diff --git a/src/V3Ast.h b/src/V3Ast.h
index 0d4ae58a7..cee54c5b8 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -1670,7 +1670,7 @@ public:
     static constexpr int INSTR_COUNT_PLI = 20;  // PLI routines
 
     // ACCESSORS
-    virtual string name() const VL_MT_SAFE { return ""; }
+    virtual string name() const VL_MT_STABLE { return ""; }
     virtual string origName() const { return ""; }
     virtual void name(const string& name) {
         this->v3fatalSrc("name() called on object without name() method");
@@ -1678,7 +1678,7 @@ public:
     virtual void tag(const string& text) {}
     virtual string tag() const { return ""; }
     virtual string verilogKwd() const { return ""; }
-    string nameProtect() const;  // Name with --protect-id applied
+    string nameProtect() const VL_MT_STABLE;  // Name with --protect-id applied
     string origNameProtect() const;  // origName with --protect-id applied
     string shortName() const;  // Name with __PVT__ removed for concatenating scopes
     static string dedotName(const string& namein);  // Name with dots removed
@@ -1691,7 +1691,7 @@ public:
     encodeName(const string& namein);  // Encode user name into internal C representation
     static string encodeNumber(int64_t num);  // Encode number into internal C representation
     static string vcdName(const string& namein);  // Name for printing out to vcd files
-    string prettyName() const VL_MT_SAFE { return prettyName(name()); }
+    string prettyName() const VL_MT_STABLE { return prettyName(name()); }
     string prettyNameQ() const { return prettyNameQ(name()); }
     string prettyTypeName() const;  // "VARREF" for error messages (NOT dtype's pretty name)
     virtual string prettyOperatorName() const { return "operator " + prettyTypeName(); }
diff --git a/src/V3AstNodeDType.h b/src/V3AstNodeDType.h
index 26f1a740e..97eaacc5b 100644
--- a/src/V3AstNodeDType.h
+++ b/src/V3AstNodeDType.h
@@ -242,7 +242,7 @@ public:
     bool similarDType(const AstNodeDType* samep) const override {
         return this == samep;  // We don't compare members, require exact equivalence
     }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& flag) override { m_name = flag; }
     bool packed() const VL_MT_SAFE { return m_packed; }
     void packed(bool flag) { m_packed = flag; }
@@ -281,7 +281,7 @@ public:
         this->valuep(valuep);
     }
     ASTGEN_MEMBERS_AstEnumItem;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool maybePointedTo() const override { return true; }
     bool hasDType() const override { return true; }
     void name(const string& flag) override { m_name = flag; }
@@ -409,7 +409,7 @@ public:
     bool similarDType(const AstNodeDType* samep) const override {
         return type() == samep->type() && same(samep);
     }
-    string name() const override { return m.m_keyword.ascii(); }
+    string name() const override VL_MT_STABLE { return m.m_keyword.ascii(); }
     string prettyDTypeName() const override;
     const char* broken() const override {
         BROKEN_RTN(dtypep() != this);
@@ -531,7 +531,7 @@ public:
     }
     void dump(std::ostream& str = std::cout) const override;
     void dumpSmall(std::ostream& str) const override;
-    string name() const override;
+    string name() const override VL_MT_STABLE;
     AstBasicDType* basicp() const override VL_MT_STABLE { return nullptr; }
     AstNodeDType* skipRefp() const override VL_MT_STABLE { return (AstNodeDType*)this; }
     AstNodeDType* skipRefToConstp() const override { return (AstNodeDType*)this; }
@@ -543,7 +543,7 @@ public:
     AstNodeDType* subDTypep() const override VL_MT_SAFE { return nullptr; }
     AstNodeModule* classOrPackagep() const { return m_classOrPackagep; }
     void classOrPackagep(AstNodeModule* nodep) { m_classOrPackagep = nodep; }
-    AstClass* classp() const { return m_classp; }
+    AstClass* classp() const VL_MT_STABLE { return m_classp; }
     void classp(AstClass* nodep) { m_classp = nodep; }
     bool isCompound() const override { return true; }
 };
@@ -641,7 +641,7 @@ public:
     AstNodeDType* skipRefToEnump() const override { return (AstNodeDType*)this; }
     int widthAlignBytes() const override { return dtypep()->widthAlignBytes(); }
     int widthTotalBytes() const override { return dtypep()->widthTotalBytes(); }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& flag) override { m_name = flag; }
     bool isCompound() const override { return false; }
 };
@@ -767,7 +767,7 @@ public:
     void refDTypep(AstNodeDType* nodep) { m_refDTypep = nodep; }
     AstNodeDType* virtRefDTypep() const override { return m_refDTypep; }
     void virtRefDTypep(AstNodeDType* nodep) override { refDTypep(nodep); }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& flag) override { m_name = flag; }
     void dump(std::ostream& str = std::cout) const override;
     void dumpSmall(std::ostream& str) const override;
@@ -879,7 +879,7 @@ public:
     }
     ASTGEN_MEMBERS_AstMemberDType;
     void dumpSmall(std::ostream& str) const override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     bool hasDType() const override { return true; }
     bool maybePointedTo() const override { return true; }
     const char* broken() const override {
@@ -955,7 +955,7 @@ public:
     int widthAlignBytes() const override { return dtypep()->widthAlignBytes(); }
     int widthTotalBytes() const override { return dtypep()->widthTotalBytes(); }
     // METHODS
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool maybePointedTo() const override { return true; }
     bool hasDType() const override { return true; }
     void name(const string& flag) override { m_name = flag; }
@@ -1093,7 +1093,7 @@ public:
     }
     void dump(std::ostream& str = std::cout) const override;
     void dumpSmall(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     string prettyDTypeName() const override {
         return subDTypep() ? prettyName(subDTypep()->name()) : prettyName();
     }
diff --git a/src/V3AstNodeExpr.h b/src/V3AstNodeExpr.h
index 5e12b2bd1..575bac814 100644
--- a/src/V3AstNodeExpr.h
+++ b/src/V3AstNodeExpr.h
@@ -236,7 +236,7 @@ public:
     const char* broken() const override;
     void cloneRelink() override;
     void dump(std::ostream& str = std::cout) const override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     bool isGateOptimizable() const override;
     string dotted() const { return m_dotted; }  // * = Scope name or ""
     string inlinedDots() const { return m_inlinedDots; }
@@ -474,7 +474,7 @@ public:
     const char* broken() const override;
     int instrCount() const override { return widthInstrs(); }
     void cloneRelink() override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     void name(const string& name) override { m_name = name; }
     VAccess access() const { return m_access; }
     void access(const VAccess& flag) { m_access = flag; }  // Avoid using this; Set in constructor
@@ -532,7 +532,7 @@ public:
     }
     ASTGEN_MEMBERS_AstArg;
     bool hasDType() const override { return false; }
-    string name() const override { return m_name; }  // * = Pin name, ""=go by number
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Pin name, ""=go by number
     void name(const string& name) override { m_name = name; }
     bool emptyConnectNoNext() const { return !exprp() && name() == "" && !nextp(); }
 
@@ -610,7 +610,7 @@ public:
         this->addPinsp(pinsp);
     }
     ASTGEN_MEMBERS_AstCMethodHard;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     void name(const string& name) override { m_name = name; }
     bool same(const AstNode* samep) const override {
         const AstCMethodHard* asamep = static_cast<const AstCMethodHard*>(samep);
@@ -689,7 +689,7 @@ public:
     }
     ASTGEN_MEMBERS_AstCellArrayRef;
     // ACCESSORS
-    string name() const override { return m_name; }  // * = Array name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Array name
 
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -710,7 +710,7 @@ public:
     }
     ASTGEN_MEMBERS_AstCellRef;
     // ACCESSORS
-    string name() const override { return m_name; }  // * = Array name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Array name
 
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -746,7 +746,7 @@ public:
                 == static_cast<const AstClassOrPackageRef*>(samep)->m_classOrPackageNodep);
     }
     void dump(std::ostream& str = std::cout) const override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     AstNode* classOrPackageNodep() const { return m_classOrPackageNodep; }
     void classOrPackageNodep(AstNode* nodep) { m_classOrPackageNodep = nodep; }
     AstNodeModule* classOrPackagep() const;
@@ -990,7 +990,7 @@ public:
         initWithNumber();
     }
     ASTGEN_MEMBERS_AstConst;
-    string name() const override { return num().ascii(); }  // * = Value
+    string name() const override VL_MT_STABLE { return num().ascii(); }  // * = Value
     const V3Number& num() const VL_MT_SAFE { return m_num; }  // * = Value
     V3Number& num() { return m_num; }  // * = Value
     uint32_t toUInt() const { return num().toUInt(); }
@@ -1058,7 +1058,7 @@ public:
     }
     ASTGEN_MEMBERS_AstEnumItemRef;
     void dump(std::ostream& str) const override;
-    string name() const override { return itemp()->name(); }
+    string name() const override VL_MT_STABLE { return itemp()->name(); }
     int instrCount() const override { return 0; }
     const char* broken() const override;
     void cloneRelink() override {
@@ -1068,7 +1068,7 @@ public:
         const AstEnumItemRef* const sp = static_cast<const AstEnumItemRef*>(samep);
         return itemp() == sp->itemp();
     }
-    AstEnumItem* itemp() const { return m_itemp; }
+    AstEnumItem* itemp() const VL_MT_STABLE { return m_itemp; }
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
     bool cleanOut() const override { return true; }
@@ -1209,7 +1209,7 @@ public:
         this->filep(filep);
     }
     ASTGEN_MEMBERS_AstFScanF;
-    string name() const override { return m_text; }
+    string name() const override VL_MT_STABLE { return m_text; }
     string verilogKwd() const override { return "$fscanf"; }
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -1406,7 +1406,7 @@ public:
     string emitC() override { V3ERROR_NA_RETURN(""); }
     bool cleanOut() const override { return true; }
     int instrCount() const override { return widthInstrs(); }
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     void name(const string& name) override { m_name = name; }
     bool index() const { return m_index; }
 };
@@ -1432,7 +1432,7 @@ public:
     void cloneRelink() override;
     const char* broken() const override;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& name) override { m_name = name; }
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -1497,7 +1497,7 @@ public:
     }
     ASTGEN_MEMBERS_AstParseRef;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     bool same(const AstNode* samep) const override {
         const AstParseRef* const asamep = static_cast<const AstParseRef*>(samep);
         return (expect() == asamep->expect() && m_name == asamep->m_name);
@@ -1671,7 +1671,7 @@ public:
         addExprsp(exprsp);
     }
     ASTGEN_MEMBERS_AstSFormatF;
-    string name() const override { return m_text; }
+    string name() const override VL_MT_STABLE { return m_text; }
     int instrCount() const override { return INSTR_COUNT_PLI; }
     bool same(const AstNode* samep) const override {
         return text() == static_cast<const AstSFormatF*>(samep)->text();
@@ -1706,7 +1706,7 @@ public:
         this->fromp(fromp);
     }
     ASTGEN_MEMBERS_AstSScanF;
-    string name() const override { return m_text; }
+    string name() const override VL_MT_STABLE { return m_text; }
     string verilogKwd() const override { return "$sscanf"; }
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -1891,7 +1891,7 @@ public:
         dtypep(nullptr);  // V3Width will resolve
     }
     ASTGEN_MEMBERS_AstStructSel;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& name) override { m_name = name; }
     string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     string emitC() override { V3ERROR_NA_RETURN(""); }
@@ -2200,7 +2200,7 @@ public:
     void numberOperate(V3Number& out, const V3Number& lhs, const V3Number& rhs) override {
         out.opCompareNN(lhs, rhs, m_ignoreCase);
     }
-    string name() const override { return m_ignoreCase ? "icompare" : "compare"; }
+    string name() const override VL_MT_STABLE { return m_ignoreCase ? "icompare" : "compare"; }
     string emitVerilog() override {
         return m_ignoreCase ? "%k(%l.icompare(%r))" : "%k(%l.compare(%r))";
     }
@@ -2424,7 +2424,7 @@ public:
     void numberOperate(V3Number& out, const V3Number& lhs, const V3Number& rhs) override {
         out.opGetcN(lhs, rhs);
     }
-    string name() const override { return "getc"; }
+    string name() const override VL_MT_STABLE { return "getc"; }
     string emitVerilog() override { return "%k(%l.getc(%r))"; }
     string emitC() override { return "VL_GETC_N(%li,%ri)"; }
     string emitSimpleOperator() override { return ""; }
@@ -4304,7 +4304,7 @@ public:
                        const V3Number& ths) override {
         out.opPutcN(lhs, rhs, ths);
     }
-    string name() const override { return "putc"; }
+    string name() const override VL_MT_STABLE { return "putc"; }
     string emitVerilog() override { return "%k(%l.putc(%r,%t))"; }
     string emitC() override { return "VL_PUTC_N(%li,%ri,%ti)"; }
     string emitSimpleOperator() override { return ""; }
@@ -4411,7 +4411,7 @@ public:
                        const V3Number& ths) override {
         out.opSubstrN(lhs, rhs, ths);
     }
-    string name() const override { return "substr"; }
+    string name() const override VL_MT_STABLE { return "substr"; }
     string emitVerilog() override { return "%k(%l.substr(%r,%t))"; }
     string emitC() override { return "VL_SUBSTR_N(%li,%ri,%ti)"; }
     string emitSimpleOperator() override { return ""; }
@@ -4488,7 +4488,7 @@ public:
     }
     ASTGEN_MEMBERS_AstAtoN;
     void numberOperate(V3Number& out, const V3Number& lhs) override { out.opAtoN(lhs, m_fmt); }
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         switch (m_fmt) {
         case ATOI: return "atoi";
         case ATOHEX: return "atohex";
diff --git a/src/V3AstNodeOther.h b/src/V3AstNodeOther.h
index 72db0c8d0..ed0bf5098 100644
--- a/src/V3AstNodeOther.h
+++ b/src/V3AstNodeOther.h
@@ -48,7 +48,7 @@ protected:
 public:
     ASTGEN_MEMBERS_AstNodeBlock;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }  // * = Block name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Block name
     void name(const string& name) override { m_name = name; }
     bool unnamed() const { return m_unnamed; }
     bool isFirstInMyListOfStatements(AstNode* nodep) const override { return nodep == stmtsp(); }
@@ -118,7 +118,7 @@ protected:
 public:
     ASTGEN_MEMBERS_AstNodeFTask;
     void dump(std::ostream& str = std::cout) const override;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     bool maybePointedTo() const override { return true; }
     bool isGateOptimizable() const override { return !((m_dpiExport || m_dpiImport) && !m_pure); }
     // {AstFunc only} op1 = Range output variable
@@ -186,7 +186,7 @@ public:
         , m_name{name} {}
     ASTGEN_MEMBERS_AstNodeFile;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool same(const AstNode* /*samep*/) const override { return true; }
 };
 class AstNodeModule VL_NOT_FINAL : public AstNode {
@@ -234,7 +234,7 @@ public:
     ASTGEN_MEMBERS_AstNodeModule;
     void dump(std::ostream& str) const override;
     bool maybePointedTo() const override { return true; }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     virtual bool timescaleMatters() const = 0;
     // ACCESSORS
     void name(const string& name) override { m_name = name; }
@@ -373,7 +373,7 @@ public:
         this->addPasssp(passsp);
     }
     ASTGEN_MEMBERS_AstNodeCoverOrAssert;
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     bool same(const AstNode* samep) const override { return samep->name() == name(); }
     void name(const string& name) override { m_name = name; }
     void dump(std::ostream& str = std::cout) const override;
@@ -512,7 +512,7 @@ public:
     }
     ASTGEN_MEMBERS_AstActive;
     void dump(std::ostream& str = std::cout) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     const char* broken() const override;
     void cloneRelink() override;
     // Statements are broken into pieces, as some must come before others.
@@ -537,7 +537,7 @@ public:
     }
     ASTGEN_MEMBERS_AstBind;
     // ACCESSORS
-    string name() const override { return m_name; }  // * = Bind Target name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Bind Target name
     void name(const string& name) override { m_name = name; }
 };
 class AstCFunc final : public AstNode {
@@ -607,7 +607,7 @@ public:
         m_dpiTraceInit = false;
     }
     ASTGEN_MEMBERS_AstCFunc;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     const char* broken() const override;
     void cloneRelink() override;
     bool maybePointedTo() const override { return true; }
@@ -702,7 +702,7 @@ public:
         , m_useType{useType} {}
     ASTGEN_MEMBERS_AstCUse;
     void dump(std::ostream& str = std::cout) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     VUseType useType() const { return m_useType; }
 };
 class AstCaseItem final : public AstNode {
@@ -755,7 +755,7 @@ public:
     const char* broken() const override;
     bool maybePointedTo() const override { return true; }
     // ACCESSORS
-    string name() const override { return m_name; }  // * = Cell name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Cell name
     void name(const string& name) override { m_name = name; }
     string origName() const override { return m_origName; }  // * = Original name
     void origName(const string& name) { m_origName = name; }
@@ -794,7 +794,7 @@ public:
     void dump(std::ostream& str) const override;
     const char* broken() const override;
     // ACCESSORS
-    string name() const override { return m_name; }  // * = Cell name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Cell name
     string origModName() const { return m_origModName; }  // * = modp()->origName() before inlining
     void name(const string& name) override { m_name = name; }
     void scopep(AstScope* scp) { m_scopep = scp; }
@@ -845,7 +845,7 @@ public:
     }
     ASTGEN_MEMBERS_AstClocking;
     void dump(std::ostream& str) const override;
-    std::string name() const override { return m_name; }
+    std::string name() const override VL_MT_STABLE { return m_name; }
     bool isDefault() const { return m_isDefault; }
     bool isGlobal() const { return m_isGlobal; }
 };
@@ -916,7 +916,7 @@ public:
         , m_path{path} {
         this->rhsp(rhsp);
     }
-    string name() const override { return m_name; }  // * = Scope name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Scope name
     ASTGEN_MEMBERS_AstDefParam;
     bool same(const AstNode*) const override { return true; }
     string path() const { return m_path; }
@@ -934,7 +934,7 @@ public:
         , m_name{vname}
         , m_cname{cname} {}
     ASTGEN_MEMBERS_AstDpiExport;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void name(const string& name) override { m_name = name; }
     string cname() const { return m_cname; }
     void cname(const string& cname) { m_cname = cname; }
@@ -995,7 +995,7 @@ public:
         BROKEN_RTN(!m_depGraphp);
         return nullptr;
     }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     V3Graph* depGraphp() { return m_depGraphp; }
     const V3Graph* depGraphp() const { return m_depGraphp; }
 };
@@ -1033,7 +1033,7 @@ public:
     AstIntfRef(FileLine* fl, const string& name)
         : ASTGEN_SUPER_IntfRef(fl)
         , m_name{name} {}
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     ASTGEN_MEMBERS_AstIntfRef;
 };
 class AstMTaskBody final : public AstNode {
@@ -1070,7 +1070,7 @@ public:
         , m_name{name} {
         this->addVarsp(varsp);
     }
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool maybePointedTo() const override { return true; }
     ASTGEN_MEMBERS_AstModport;
 };
@@ -1092,7 +1092,7 @@ public:
     const char* broken() const override;
     void cloneRelink() override;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool isImport() const { return !m_export; }
     bool isExport() const { return m_export; }
     AstNodeFTask* ftaskp() const { return m_ftaskp; }  // [After Link] Pointer to variable
@@ -1115,7 +1115,7 @@ public:
     const char* broken() const override;
     void cloneRelink() override;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     void direction(const VDirection& flag) { m_direction = flag; }
     VDirection direction() const { return m_direction; }
     AstVar* varp() const { return m_varp; }  // [After Link] Pointer to variable
@@ -1149,7 +1149,7 @@ public:
     ASTGEN_MEMBERS_AstNetlist;
     const char* broken() const override;
     void cloneRelink() override { V3ERROR_NA; }
-    string name() const override { return "$root"; }
+    string name() const override VL_MT_STABLE { return "$root"; }
     void dump(std::ostream& str) const override;
     AstNodeModule* topModulep() const {  // Top module in hierarchy
         return modulesp();  // First one in the list, for now
@@ -1198,7 +1198,7 @@ public:
     const char* broken() const override;
     void cloneRelink() override;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     AstPackage* packagep() const { return m_packagep; }
     void packagep(AstPackage* nodep) { m_packagep = nodep; }
 };
@@ -1224,7 +1224,7 @@ public:
     const char* broken() const override;
     void cloneRelink() override;
     void dump(std::ostream& str) const override;
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     AstPackage* packagep() const { return m_packagep; }
     void packagep(AstPackage* nodep) { m_packagep = nodep; }
 };
@@ -1250,7 +1250,7 @@ public:
     ASTGEN_MEMBERS_AstPin;
     void dump(std::ostream& str) const override;
     const char* broken() const override;
-    string name() const override { return m_name; }  // * = Pin name, ""=go by number
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Pin name, ""=go by number
     void name(const string& name) override { m_name = name; }
     string prettyOperatorName() const override;
     bool dotStar() const { return name() == ".*"; }  // Fake name for .* connections until linked
@@ -1278,7 +1278,7 @@ public:
         , m_pinNum{pinnum}
         , m_name{name} {}
     ASTGEN_MEMBERS_AstPort;
-    string name() const override { return m_name; }  // * = Port name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Port name
     int pinNum() const { return m_pinNum; }  // * = Pin number, for order based instantiation
 };
 class AstPragma final : public AstNode {
@@ -1356,7 +1356,7 @@ public:
     void cloneRelink() override;
     const char* broken() const override;
     bool maybePointedTo() const override { return true; }
-    string name() const override { return m_name; }  // * = Scope name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Scope name
     void name(const string& name) override { m_name = name; }
     void dump(std::ostream& str) const override;
     string nameDotless() const;
@@ -1548,7 +1548,7 @@ public:
         return dtypep() ? dtypep() : childDTypep();
     }
     // METHODS
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool maybePointedTo() const override { return true; }
     bool hasDType() const override { return true; }
     void name(const string& flag) override { m_name = flag; }
@@ -1568,7 +1568,7 @@ public:
         , m_name{name} {}
     ASTGEN_MEMBERS_AstTypedefFwd;
     // METHODS
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
     bool maybePointedTo() const override { return true; }
 };
 class AstUdpTable final : public AstNode {
@@ -1588,7 +1588,7 @@ public:
         : ASTGEN_SUPER_UdpTableLine(fl)
         , m_text{text} {}
     ASTGEN_MEMBERS_AstUdpTableLine;
-    string name() const override { return m_text; }
+    string name() const override VL_MT_STABLE { return m_text; }
     string text() const { return m_text; }
 };
 class AstVar final : public AstNode {
@@ -1758,7 +1758,7 @@ public:
     }
     ASTGEN_MEMBERS_AstVar;
     void dump(std::ostream& str) const override;
-    string name() const override VL_MT_SAFE { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE VL_MT_SAFE { return m_name; }  // * = Var name
     bool hasDType() const override { return true; }
     bool maybePointedTo() const override { return true; }
     string origName() const override { return m_origName; }  // * = Original name
@@ -1998,7 +1998,7 @@ public:
         return nullptr;
     }
     bool maybePointedTo() const override { return true; }
-    string name() const override { return scopep()->name() + "->" + varp()->name(); }
+    string name() const override VL_MT_STABLE { return scopep()->name() + "->" + varp()->name(); }
     void dump(std::ostream& str) const override;
     bool hasDType() const override { return true; }
     AstVar* varp() const { return m_varp; }  // [After Link] Pointer to variable
@@ -2452,7 +2452,7 @@ public:
         , m_name{name}
         , m_showAt{showAt} {}
     ASTGEN_MEMBERS_AstComment;
-    string name() const override { return m_name; }  // * = Text
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Text
     bool same(const AstNode* samep) const override { return true; }  // Ignore name in comments
     virtual bool showAt() const { return m_showAt; }
 };
@@ -2593,7 +2593,7 @@ public:
         : ASTGEN_SUPER_Disable(fl)
         , m_name{name} {}
     ASTGEN_MEMBERS_AstDisable;
-    string name() const override { return m_name; }  // * = Block name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Block name
     void name(const string& flag) override { m_name = flag; }
     bool isBrancher() const override {
         return true;  // SPECIAL: We don't process code after breaks
@@ -2884,7 +2884,7 @@ public:
         : ASTGEN_SUPER_PrintTimeScale(fl) {}
     ASTGEN_MEMBERS_AstPrintTimeScale;
     void name(const string& name) override { m_name = name; }
-    string name() const override { return m_name; }  // * = Var name
+    string name() const override VL_MT_STABLE { return m_name; }  // * = Var name
     void dump(std::ostream& str) const override;
     string verilogKwd() const override { return "$printtimescale"; }
     bool isGateOptimizable() const override { return false; }
@@ -3103,7 +3103,7 @@ public:
     void dump(std::ostream& str) const override;
     int instrCount() const override { return 100; }  // Large...
     ASTGEN_MEMBERS_AstTraceDecl;
-    string name() const override { return m_showname; }
+    string name() const override VL_MT_STABLE { return m_showname; }
     bool maybePointedTo() const override { return true; }
     bool hasDType() const override { return true; }
     bool same(const AstNode* samep) const override { return false; }
diff --git a/src/V3Config.cpp b/src/V3Config.cpp
index b6ede32c0..c6fb382c3 100644
--- a/src/V3Config.cpp
+++ b/src/V3Config.cpp
@@ -40,25 +40,31 @@ template <typename T>
 class V3ConfigWildcardResolver final {
     using Map = std::map<const std::string, T>;
 
-    Map m_mapWildcard;  // Wildcard strings to entities
-    Map m_mapResolved;  // Resolved strings to converged entities
+    mutable VerilatedMutex m_mutex;  // protects members
+    Map m_mapWildcard VL_GUARDED_BY(m_mutex);  // Wildcard strings to entities
+    Map m_mapResolved VL_GUARDED_BY(m_mutex);  // Resolved strings to converged entities
 public:
     V3ConfigWildcardResolver() = default;
     ~V3ConfigWildcardResolver() = default;
 
     /// Update into maps from other
-    void update(const V3ConfigWildcardResolver& other) {
+    void update(const V3ConfigWildcardResolver& other) VL_MT_SAFE_EXCLUDES(m_mutex)
+        VL_EXCLUDES(other.m_mutex) {
+        VerilatedLockGuard lock{m_mutex};
+        VerilatedLockGuard otherLock{other.m_mutex};
         for (const auto& itr : other.m_mapResolved) m_mapResolved[itr.first].update(itr.second);
         for (const auto& itr : other.m_mapWildcard) m_mapWildcard[itr.first].update(itr.second);
     }
 
     // Access and create a (wildcard) entity
-    T& at(const string& name) {
+    T& at(const string& name) VL_MT_SAFE_EXCLUDES(m_mutex) {
+        VerilatedLockGuard lock{m_mutex};
         // Don't store into wildcards if the name is not a wildcard string
         return m_mapWildcard[name];
     }
     // Access an entity and resolve wildcards that match it
-    T* resolve(const string& name) {
+    T* resolve(const string& name) VL_MT_SAFE_EXCLUDES(m_mutex) {
+        VerilatedLockGuard lock{m_mutex};
         // Lookup if it was resolved before, typically not
         auto it = m_mapResolved.find(name);
         if (VL_UNLIKELY(it != m_mapResolved.end())) return &it->second;
@@ -78,7 +84,10 @@ public:
         return newp;
     }
     // Flush on update
-    void flush() { m_mapResolved.clear(); }
+    void flush() VL_MT_SAFE_EXCLUDES(m_mutex) {
+        VerilatedLockGuard lock{m_mutex};
+        m_mapResolved.clear();
+    }
 };
 
 // Only public_flat_rw has the sensitity tree
diff --git a/src/V3EmitCBase.h b/src/V3EmitCBase.h
index ebb7ed3f4..a183b4e78 100644
--- a/src/V3EmitCBase.h
+++ b/src/V3EmitCBase.h
@@ -63,7 +63,9 @@ public:
     void putsQuoted(const string& str) { ofp()->putsQuoted(str); }
     void ensureNewLine() { ofp()->ensureNewLine(); }
     bool optSystemC() { return v3Global.opt.systemC(); }
-    static string protect(const string& name) { return VIdProtect::protectIf(name, true); }
+    static string protect(const string& name) VL_MT_SAFE {
+        return VIdProtect::protectIf(name, true);
+    }
     static string protectIf(const string& name, bool doIt) {
         return VIdProtect::protectIf(name, doIt);
     }
@@ -84,7 +86,7 @@ public:
         return symClassName() + "* const __restrict vlSymsp VL_ATTR_UNUSED = vlSelf->vlSymsp;\n";
     }
     static string funcNameProtect(const AstCFunc* nodep, const AstNodeModule* modp = nullptr);
-    static string prefixNameProtect(const AstNode* nodep) {  // C++ name with prefix
+    static string prefixNameProtect(const AstNode* nodep) VL_MT_SAFE {  // C++ name with prefix
         return v3Global.opt.modPrefix() + "_" + protect(nodep->name());
     }
     static string topClassName() VL_MT_SAFE {  // Return name of top wrapper module
diff --git a/src/V3File.cpp b/src/V3File.cpp
index 6ae1507e0..5fd603d6e 100644
--- a/src/V3File.cpp
+++ b/src/V3File.cpp
@@ -108,7 +108,8 @@ class V3FileDependImp final {
     };
 
     // MEMBERS
-    std::set<string> m_filenameSet;  // Files generated (elim duplicates)
+    VerilatedMutex m_mutex;  // Protects members
+    std::set<string> m_filenameSet VL_GUARDED_BY(m_mutex);  // Files generated (elim duplicates)
     std::set<DependFile> m_filenameList;  // Files sourced/generated
 
     static string stripQuotes(const string& in) {
@@ -121,7 +122,8 @@ class V3FileDependImp final {
 
 public:
     // ACCESSOR METHODS
-    void addSrcDepend(const string& filename) {
+    void addSrcDepend(const string& filename) VL_MT_SAFE_EXCLUDES(m_mutex) {
+        const VerilatedLockGuard lock{m_mutex};
         const auto itFoundPair = m_filenameSet.insert(filename);
         if (itFoundPair.second) {
             DependFile df{filename, false};
@@ -129,7 +131,8 @@ public:
             m_filenameList.insert(df);
         }
     }
-    void addTgtDepend(const string& filename) {
+    void addTgtDepend(const string& filename) VL_MT_SAFE_EXCLUDES(m_mutex) {
+        const VerilatedLockGuard lock{m_mutex};
         const auto itFoundPair = m_filenameSet.insert(filename);
         if (itFoundPair.second) m_filenameList.insert(DependFile{filename, true});
     }
@@ -297,8 +300,8 @@ bool V3FileDependImp::checkTimes(const string& filename, const string& cmdlineIn
 //######################################################################
 // V3File
 
-void V3File::addSrcDepend(const string& filename) { dependImp.addSrcDepend(filename); }
-void V3File::addTgtDepend(const string& filename) { dependImp.addTgtDepend(filename); }
+void V3File::addSrcDepend(const string& filename) VL_MT_SAFE { dependImp.addSrcDepend(filename); }
+void V3File::addTgtDepend(const string& filename) VL_MT_SAFE { dependImp.addTgtDepend(filename); }
 void V3File::writeDepend(const string& filename) { dependImp.writeDepend(filename); }
 std::vector<string> V3File::getAllDeps() { return dependImp.getAllDeps(); }
 void V3File::writeTimes(const string& filename, const string& cmdlineIn) {
@@ -954,12 +957,13 @@ void V3OutCFile::putsGuard() {
 
 class VIdProtectImp final {
     // MEMBERS
+    VerilatedMutex m_mutex;  // Protects members
     std::map<const std::string, std::string> m_nameMap;  // Map of old name into new name
-    std::unordered_set<std::string> m_newIdSet;  // Which new names exist
+    std::unordered_set<std::string> m_newIdSet VL_GUARDED_BY(m_mutex);  // Which new names exist
 protected:
     // CONSTRUCTORS
     friend class VIdProtect;
-    static VIdProtectImp& singleton() {
+    static VIdProtectImp& singleton() VL_MT_SAFE {
         static VIdProtectImp s;
         return s;
     }
@@ -973,8 +977,9 @@ public:
     }
     ~VIdProtectImp() = default;
     // METHODS
-    string passthru(const string& old) {
+    string passthru(const string& old) VL_MT_SAFE_EXCLUDES(m_mutex) {
         if (!v3Global.opt.protectIds()) return old;
+        const VerilatedLockGuard lock{m_mutex};
         const auto it = m_nameMap.find(old);
         if (it != m_nameMap.end()) {
             // No way to go back and correct the older crypt name
@@ -986,8 +991,9 @@ public:
         }
         return old;
     }
-    string protectIf(const string& old, bool doIt) {
+    string protectIf(const string& old, bool doIt) VL_MT_SAFE_EXCLUDES(m_mutex) {
         if (!v3Global.opt.protectIds() || old.empty() || !doIt) return old;
+        const VerilatedLockGuard lock{m_mutex};
         const auto it = m_nameMap.find(old);
         if (it != m_nameMap.end()) {
             return it->second;
@@ -1017,7 +1023,7 @@ public:
             return out;
         }
     }
-    string protectWordsIf(const string& old, bool doIt) {
+    string protectWordsIf(const string& old, bool doIt) VL_MT_SAFE {
         // Split at " " (for traces), "." (for scopes), "->", "(", "&", ")" (for self pointers)
         if (!(doIt && v3Global.opt.protectIds())) return old;
         string out;
@@ -1056,7 +1062,7 @@ public:
 
 private:
     void trySep(const string& old, string::size_type start, const string& trySep,
-                string::size_type& posr, string& separatorr) {
+                string::size_type& posr, string& separatorr) VL_PURE {
         const string::size_type trypos = old.find(trySep, start);
         if (trypos != string::npos) {
             if (posr == string::npos || (posr > trypos)) {
@@ -1067,10 +1073,10 @@ private:
     }
 };
 
-string VIdProtect::protectIf(const string& old, bool doIt) {
+string VIdProtect::protectIf(const string& old, bool doIt) VL_MT_SAFE {
     return VIdProtectImp::singleton().protectIf(old, doIt);
 }
-string VIdProtect::protectWordsIf(const string& old, bool doIt) {
+string VIdProtect::protectWordsIf(const string& old, bool doIt) VL_MT_SAFE {
     return VIdProtectImp::singleton().protectWordsIf(old, doIt);
 }
 void VIdProtect::writeMapFile(const string& filename) {
diff --git a/src/V3File.h b/src/V3File.h
index 2c1d34850..3f1cbebc2 100644
--- a/src/V3File.h
+++ b/src/V3File.h
@@ -61,8 +61,8 @@ public:
     }
 
     // Dependencies
-    static void addSrcDepend(const string& filename);
-    static void addTgtDepend(const string& filename);
+    static void addSrcDepend(const string& filename) VL_MT_SAFE;
+    static void addTgtDepend(const string& filename) VL_MT_SAFE;
     static void writeDepend(const string& filename);
     static std::vector<string> getAllDeps();
     static void writeTimes(const string& filename, const string& cmdlineIn);
@@ -318,10 +318,10 @@ class VIdProtect final {
 public:
     // METHODS
     // Rename to a new encoded string (unless earlier passthru'ed)
-    static string protect(const string& old) { return protectIf(old, true); }
-    static string protectIf(const string& old, bool doIt = true);
+    static string protect(const string& old) VL_MT_SAFE { return protectIf(old, true); }
+    static string protectIf(const string& old, bool doIt = true) VL_MT_SAFE;
     // Rename words to a new encoded string
-    static string protectWordsIf(const string& old, bool doIt = true);
+    static string protectWordsIf(const string& old, bool doIt = true) VL_MT_SAFE;
     // Write map of renames to output file
     static void writeMapFile(const string& filename);
 };
diff --git a/src/V3FileLine.cpp b/src/V3FileLine.cpp
index 8f7362b38..839bd4573 100644
--- a/src/V3FileLine.cpp
+++ b/src/V3FileLine.cpp
@@ -87,7 +87,9 @@ void FileLineSingleton::fileNameNumMapDumpXml(std::ostream& os) {
     os << "</files>\n";
 }
 
-FileLineSingleton::msgEnSetIdx_t FileLineSingleton::addMsgEnBitSet(const MsgEnBitSet& bitSet) {
+FileLineSingleton::msgEnSetIdx_t FileLineSingleton::addMsgEnBitSet(const MsgEnBitSet& bitSet)
+    VL_MT_SAFE_EXCLUDES(m_mutex) {
+    VerilatedLockGuard lock{m_mutex};
     const auto pair = m_internedMsgEnIdxs.emplace(bitSet, 0);
     msgEnSetIdx_t& idx = pair.first->second;
     if (pair.second) {
@@ -100,7 +102,7 @@ FileLineSingleton::msgEnSetIdx_t FileLineSingleton::addMsgEnBitSet(const MsgEnBi
     return idx;
 }
 
-FileLineSingleton::msgEnSetIdx_t FileLineSingleton::defaultMsgEnIndex() {
+FileLineSingleton::msgEnSetIdx_t FileLineSingleton::defaultMsgEnIndex() VL_MT_SAFE {
     MsgEnBitSet msgEnBitSet;
     for (int i = V3ErrorCode::EC_MIN; i < V3ErrorCode::_ENUM_MAX; ++i) {
         msgEnBitSet.set(i, !V3ErrorCode{i}.defaultsOff());
diff --git a/src/V3FileLine.h b/src/V3FileLine.h
index 96a52526c..6f66277c1 100644
--- a/src/V3FileLine.h
+++ b/src/V3FileLine.h
@@ -20,6 +20,8 @@
 #include "config_build.h"
 #include "verilatedos.h"
 
+#include "verilated_threads.h"
+
 #include "V3Error.h"
 #include "V3LangCode.h"
 
@@ -50,12 +52,13 @@ class FileLineSingleton final {
     using MsgEnBitSet = std::bitset<V3ErrorCode::_ENUM_MAX>;
 
     // MEMBERS
+    VerilatedMutex m_mutex;  // protects members
     std::map<const std::string, fileNameIdx_t> m_namemap;  // filenameno for each filename
     std::deque<string> m_names;  // filename text for each filenameno
     std::deque<V3LangCode> m_languages;  // language for each filenameno
 
     // Map from flag set to the index in m_internedMsgEns for interning
-    std::unordered_map<MsgEnBitSet, msgEnSetIdx_t> m_internedMsgEnIdxs;
+    std::unordered_map<MsgEnBitSet, msgEnSetIdx_t> m_internedMsgEnIdxs VL_GUARDED_BY(m_mutex);
     // Interned message enablement flag sets
     std::vector<MsgEnBitSet> m_internedMsgEns;
 
@@ -78,9 +81,9 @@ class FileLineSingleton final {
     static string filenameLetters(fileNameIdx_t fileno) VL_PURE;
 
     // Add given bitset to the interned bitsets, return interned index
-    msgEnSetIdx_t addMsgEnBitSet(const MsgEnBitSet& bitSet);
+    msgEnSetIdx_t addMsgEnBitSet(const MsgEnBitSet& bitSet) VL_MT_SAFE_EXCLUDES(m_mutex);
     // Add index of default bitset
-    msgEnSetIdx_t defaultMsgEnIndex();
+    msgEnSetIdx_t defaultMsgEnIndex() VL_MT_SAFE;
     // Set bitIdx to value in bitset at interned index setIdx, return interned index of result
     msgEnSetIdx_t msgEnSetBit(msgEnSetIdx_t setIdx, size_t bitIdx, bool value);
     // Return index to intersection set
diff --git a/src/V3Gate.cpp b/src/V3Gate.cpp
index 3b450856f..4c4ef2e7d 100644
--- a/src/V3Gate.cpp
+++ b/src/V3Gate.cpp
@@ -134,7 +134,9 @@ public:
     ~GateVarVertex() override = default;
     // ACCESSORS
     AstVarScope* varScp() const { return m_varScp; }
-    string name() const override { return (cvtToHex(m_varScp) + " " + varScp()->name()); }
+    string name() const override VL_MT_STABLE {
+        return (cvtToHex(m_varScp) + " " + varScp()->name());
+    }
     string dotColor() const override { return "blue"; }
     bool isTop() const { return m_isTop; }
     void setIsTop() { m_isTop = true; }
@@ -174,7 +176,9 @@ public:
         , m_slow{slow} {}
     ~GateLogicVertex() override = default;
     // ACCESSORS
-    string name() const override { return (cvtToHex(m_nodep) + "@" + scopep()->prettyName()); }
+    string name() const override VL_MT_STABLE {
+        return (cvtToHex(m_nodep) + "@" + scopep()->prettyName());
+    }
     string dotColor() const override { return "purple"; }
     FileLine* fileline() const override { return nodep()->fileline(); }
     AstNode* nodep() const { return m_nodep; }
diff --git a/src/V3Global.h b/src/V3Global.h
index 0537f534c..db6dc04ba 100644
--- a/src/V3Global.h
+++ b/src/V3Global.h
@@ -98,7 +98,7 @@ class V3Global final {
     VWidthMinUsage m_widthMinUsage
         = VWidthMinUsage::LINT_WIDTH;  // What AstNode::widthMin() is used for
 
-    int m_debugFileNumber = 0;  // Number to append to debug files created
+    std::atomic_int m_debugFileNumber{0};  // Number to append to debug files created
     bool m_assertDTypesResolved = false;  // Tree should have dtypep()'s
     bool m_assertScoped = false;  // Tree is scoped
     bool m_constRemoveXs = false;  // Const needs to strip any Xs
@@ -143,7 +143,7 @@ public:
     void widthMinUsage(const VWidthMinUsage& flag) { m_widthMinUsage = flag; }
     bool constRemoveXs() const { return m_constRemoveXs; }
     void constRemoveXs(bool flag) { m_constRemoveXs = flag; }
-    string debugFilename(const string& nameComment, int newNumber = 0) VL_MT_SAFE;
+    string debugFilename(const string& nameComment, int newNumber = 0);
     static string digitsFilename(int number);
     bool needTraceDumper() const { return m_needTraceDumper; }
     void needTraceDumper(bool flag) { m_needTraceDumper = flag; }
diff --git a/src/V3GraphTest.cpp b/src/V3GraphTest.cpp
index cb48888a6..8a9637cdf 100644
--- a/src/V3GraphTest.cpp
+++ b/src/V3GraphTest.cpp
@@ -60,7 +60,7 @@ public:
         , m_name{name} {}
     ~V3GraphTestVertex() override = default;
     // ACCESSORS
-    string name() const override { return m_name; }
+    string name() const override VL_MT_STABLE { return m_name; }
 };
 
 class V3GraphTestVarVertex final : public V3GraphTestVertex {
diff --git a/src/V3LinkCells.cpp b/src/V3LinkCells.cpp
index 20f5e545c..f30bb9601 100644
--- a/src/V3LinkCells.cpp
+++ b/src/V3LinkCells.cpp
@@ -59,8 +59,8 @@ public:
         : V3GraphVertex{graphp}
         , m_modp{modp} {}
     ~LinkCellsVertex() override = default;
-    AstNodeModule* modp() const { return m_modp; }
-    string name() const override { return modp()->name(); }
+    AstNodeModule* modp() const VL_MT_STABLE { return m_modp; }
+    string name() const override VL_MT_STABLE { return modp()->name(); }
     FileLine* fileline() const override { return modp()->fileline(); }
     // Recursive modules get space for maximum recursion
     uint32_t rankAdder() const override {
@@ -73,7 +73,7 @@ public:
     explicit LibraryVertex(V3Graph* graphp)
         : V3GraphVertex{graphp} {}
     ~LibraryVertex() override = default;
-    string name() const override { return "*LIBRARY*"; }
+    string name() const override VL_MT_STABLE { return "*LIBRARY*"; }
 };
 
 void LinkCellsGraph::loopsMessageCb(V3GraphVertex* vertexp) {
diff --git a/src/V3Number.cpp b/src/V3Number.cpp
index a74d7a64d..7defef9a5 100644
--- a/src/V3Number.cpp
+++ b/src/V3Number.cpp
@@ -498,7 +498,7 @@ V3Number& V3Number::setMask(int nbits) {
 //======================================================================
 // ACCESSORS - as strings
 
-string V3Number::ascii(bool prefixed, bool cleanVerilog) const {
+string V3Number::ascii(bool prefixed, bool cleanVerilog) const VL_MT_SAFE {
     std::ostringstream out;
 
     if (is1Step()) {
@@ -1050,7 +1050,7 @@ bool V3Number::isEqAllOnes(int optwidth) const {
     }
     return true;
 }
-bool V3Number::isFourState() const {
+bool V3Number::isFourState() const VL_MT_SAFE {
     if (isDouble() || isString()) return false;
     for (int i = 0; i < words(); ++i) {
         if (m_data.num()[i].m_valueX) return true;
diff --git a/src/V3Number.h b/src/V3Number.h
index 2afc9354f..b94a212fb 100644
--- a/src/V3Number.h
+++ b/src/V3Number.h
@@ -583,7 +583,7 @@ public:
     V3Number& setMask(int nbits);  // IE if nbits=1, then 0b1, if 2->0b11, if 3->0b111 etc
 
     // ACCESSORS
-    string ascii(bool prefixed = true, bool cleanVerilog = false) const;
+    string ascii(bool prefixed = true, bool cleanVerilog = false) const VL_MT_SAFE;
     string displayed(AstNode* nodep, const string& vformat) const VL_MT_SAFE;
     static bool displayedFmtLegal(char format, bool isScan);  // Is this a valid format letter?
     int width() const VL_MT_SAFE { return m_data.width(); }
@@ -615,7 +615,7 @@ public:
     bool isNegative() const { return !isString() && bitIs1(width() - 1); }
     bool is1Step() const VL_MT_SAFE { return m_data.m_is1Step; }
     bool isNull() const VL_MT_SAFE { return m_data.m_isNull; }
-    bool isFourState() const;
+    bool isFourState() const VL_MT_SAFE;
     bool hasZ() const {
         if (isString()) return false;
         for (int i = 0; i < words(); i++) {
diff --git a/src/V3Options.cpp b/src/V3Options.cpp
index 96996d58c..ea3fcf25f 100644
--- a/src/V3Options.cpp
+++ b/src/V3Options.cpp
@@ -880,7 +880,9 @@ string V3Options::version() VL_PURE {
     return ver;
 }
 
-string V3Options::protectKeyDefaulted() {
+string V3Options::protectKeyDefaulted() VL_MT_SAFE {
+    static VerilatedMutex mutex;
+    const VerilatedLockGuard lock{mutex};
     if (m_protectKey.empty()) {
         // Create a key with a human-readable symbol-like name.
         // This conversion drops ~2 bits of entropy out of 256, shouldn't matter.
diff --git a/src/V3Options.h b/src/V3Options.h
index 26a41f712..7e6b639b3 100644
--- a/src/V3Options.h
+++ b/src/V3Options.h
@@ -573,7 +573,7 @@ public:
     string prefix() const VL_MT_SAFE { return m_prefix; }
     // Not just called protectKey() to avoid bugs of not using protectKeyDefaulted()
     bool protectKeyProvided() const { return !m_protectKey.empty(); }
-    string protectKeyDefaulted();  // Set default key if not set by user
+    string protectKeyDefaulted() VL_MT_SAFE;  // Set default key if not set by user
     string topModule() const { return m_topModule; }
     string unusedRegexp() const { return m_unusedRegexp; }
     string waiverOutput() const { return m_waiverOutput; }
diff --git a/src/V3OrderGraph.h b/src/V3OrderGraph.h
index 5cc0ea85b..c1e3f2a91 100644
--- a/src/V3OrderGraph.h
+++ b/src/V3OrderGraph.h
@@ -159,7 +159,7 @@ public:
     AstSenTree* hybridp() const { return m_hybridp; }
 
     // LCOV_EXCL_START // Debug code
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         return (cvtToHex(m_nodep) + "\\n " + cvtToStr(nodep()->typeName()));
     }
     string dotShape() const override { return VN_IS(m_nodep, Active) ? "doubleoctagon" : "rect"; }
@@ -182,7 +182,7 @@ public:
     // LCOV_EXCL_START // Debug code
     string dotShape() const override final { return "ellipse"; }
     virtual string nameSuffix() const = 0;
-    string name() const override final {
+    string name() const override final VL_MT_STABLE {
         return cvtToHex(m_vscp) + " " + nameSuffix() + "\\n " + m_vscp->name();
     }
     // LCOV_EXCL_STOP
diff --git a/src/V3OrderMoveGraph.h b/src/V3OrderMoveGraph.h
index c0187a68f..622ffd5d9 100644
--- a/src/V3OrderMoveGraph.h
+++ b/src/V3OrderMoveGraph.h
@@ -64,7 +64,7 @@ public:
         }
     }
 
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         string nm;
         if (VL_UNCOVERABLE(!logicp())) {  // Avoid crash when debugging
             nm = "nul";  // LCOV_EXCL_LINE
diff --git a/src/V3Os.cpp b/src/V3Os.cpp
index 7a4722839..377e3594f 100644
--- a/src/V3Os.cpp
+++ b/src/V3Os.cpp
@@ -28,6 +28,8 @@
 #include "config_build.h"
 #include "verilatedos.h"
 
+#include "verilated_threads.h"
+
 // Limited V3 headers here - this is a base class for Vlc etc
 #include "V3Os.h"
 #include "V3String.h"
@@ -286,7 +288,7 @@ uint64_t V3Os::rand64(std::array<uint64_t, 2>& stater) {
     return result;
 }
 
-string V3Os::trueRandom(size_t size) {
+string V3Os::trueRandom(size_t size) VL_MT_SAFE {
     string result(size, '\xFF');
     char* const data = const_cast<char*>(result.data());
     // Note: std::string.data() returns a non-const Char* from C++17 onwards.
diff --git a/src/V3Os.h b/src/V3Os.h
index 4300417fd..4f4d44bb9 100644
--- a/src/V3Os.h
+++ b/src/V3Os.h
@@ -59,7 +59,7 @@ public:
 
     // METHODS (random)
     static uint64_t rand64(std::array<uint64_t, 2>& stater);
-    static string trueRandom(size_t size);
+    static string trueRandom(size_t size) VL_MT_SAFE;
 
     // METHODS (time & performance)
     static void u_sleep(int64_t usec);  ///< Sleep for a given number of microseconds.
diff --git a/src/V3Partition.cpp b/src/V3Partition.cpp
index 82b41ca32..45976fe76 100644
--- a/src/V3Partition.cpp
+++ b/src/V3Partition.cpp
@@ -321,7 +321,7 @@ public:
 
     void checkRelativesCp(GraphWay way) const;
 
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         // Display forward and reverse critical path costs. This gives a quick
         // read on whether graph partitioning looks reasonable or bad.
         std::ostringstream out;
diff --git a/src/V3PartitionGraph.h b/src/V3PartitionGraph.h
index fc16c81c6..b83679a06 100644
--- a/src/V3PartitionGraph.h
+++ b/src/V3PartitionGraph.h
@@ -85,7 +85,7 @@ public:
         // If this MTask maps to a C function, this should be the name
         return std::string{"__Vmtask"} + "__" + cvtToStr(m_id);
     }
-    string name() const override { return std::string{"mt"} + cvtToStr(id()); }
+    string name() const override VL_MT_STABLE { return std::string{"mt"} + cvtToStr(id()); }
     string hashName() const { return m_hashName; }
     void hashName(const string& name) { m_hashName = name; }
     void dump(std::ostream& str) const {
diff --git a/src/V3SchedAcyclic.cpp b/src/V3SchedAcyclic.cpp
index bed28d66d..ac9bec353 100644
--- a/src/V3SchedAcyclic.cpp
+++ b/src/V3SchedAcyclic.cpp
@@ -76,7 +76,7 @@ public:
     AstScope* scopep() const { return m_scopep; }
 
     // LCOV_EXCL_START // Debug code
-    string name() const override { return m_logicp->fileline()->ascii(); };
+    string name() const override VL_MT_STABLE { return m_logicp->fileline()->ascii(); };
     string dotShape() const override { return "rectangle2"; }
     // LCOV_EXCL_STOP
 };
@@ -93,7 +93,7 @@ public:
     V3GraphVertex* clone(V3Graph* graphp) const override { return new VarVertex{graphp, vscp()}; }
 
     // LCOV_EXCL_START // Debug code
-    string name() const override { return m_vscp->name(); }
+    string name() const override VL_MT_STABLE { return m_vscp->name(); }
     string dotShape() const override { return "ellipse"; }
     string dotColor() const override { return "blue"; }
     // LCOV_EXCL_STOP
diff --git a/src/V3SchedPartition.cpp b/src/V3SchedPartition.cpp
index 0234dab01..849ff16e7 100644
--- a/src/V3SchedPartition.cpp
+++ b/src/V3SchedPartition.cpp
@@ -89,7 +89,7 @@ public:
     AstNode* logicp() const { return m_logicp; }
 
     // LCOV_EXCL_START // Debug code
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         return m_logicp->typeName() + ("\n" + m_logicp->fileline()->ascii());
     };
     string dotShape() const override { return "rectangle"; }
@@ -105,7 +105,7 @@ public:
         , m_vscp{vscp} {}
 
     // LCOV_EXCL_START // Debug code
-    string name() const override { return m_vscp->name(); }
+    string name() const override VL_MT_STABLE { return m_vscp->name(); }
     string dotShape() const override {
         return m_vscp->scopep()->isTop() && m_vscp->varp()->isNonOutput() ? "invhouse" : "ellipse";
     }
diff --git a/src/V3SchedReplicate.cpp b/src/V3SchedReplicate.cpp
index 0564bb60d..7db10cabf 100644
--- a/src/V3SchedReplicate.cpp
+++ b/src/V3SchedReplicate.cpp
@@ -109,7 +109,7 @@ public:
     RegionFlags assignedRegion() const { return m_assignedRegion; }
 
     // For graph dumping
-    string name() const override { return m_logicp->fileline()->ascii(); };
+    string name() const override VL_MT_STABLE { return m_logicp->fileline()->ascii(); };
     string dotShape() const override { return "rectangle"; }
 };
 
@@ -134,7 +134,7 @@ public:
     AstScope* scopep() const { return m_vscp->scopep(); }
 
     // For graph dumping
-    string name() const override { return m_vscp->name(); }
+    string name() const override VL_MT_STABLE { return m_vscp->name(); }
     string dotShape() const override { return varp()->isPrimaryInish() ? "invhouse" : "ellipse"; }
 };
 
diff --git a/src/V3Split.cpp b/src/V3Split.cpp
index db8a8da73..0c135d3e9 100644
--- a/src/V3Split.cpp
+++ b/src/V3Split.cpp
@@ -109,7 +109,9 @@ protected:
     // ACCESSORS
     // Do not make accessor for nodep(),  It may change due to
     // reordering a lower block, but we don't repair it
-    string name() const override { return cvtToHex(m_nodep) + ' ' + m_nodep->prettyTypeName(); }
+    string name() const override VL_MT_STABLE {
+        return cvtToHex(m_nodep) + ' ' + m_nodep->prettyTypeName();
+    }
     FileLine* fileline() const override { return nodep()->fileline(); }
 
 public:
@@ -121,7 +123,7 @@ public:
     explicit SplitPliVertex(V3Graph* graphp, AstNode* nodep)
         : SplitNodeVertex{graphp, nodep} {}
     ~SplitPliVertex() override = default;
-    string name() const override { return "*PLI*"; }
+    string name() const override VL_MT_STABLE { return "*PLI*"; }
     string dotColor() const override { return "green"; }
 };
 
@@ -146,7 +148,7 @@ public:
     SplitVarPostVertex(V3Graph* graphp, AstNode* nodep)
         : SplitNodeVertex{graphp, nodep} {}
     ~SplitVarPostVertex() override = default;
-    string name() const override { return string("POST ") + SplitNodeVertex::name(); }
+    string name() const override VL_MT_STABLE { return string("POST ") + SplitNodeVertex::name(); }
     string dotColor() const override { return "CadetBlue"; }
 };
 
diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index 500d8e6dc..64567e122 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -67,8 +67,8 @@ public:
         : TaskBaseVertex{graphp}
         , m_nodep{nodep} {}
     ~TaskFTaskVertex() override = default;
-    AstNodeFTask* nodep() const { return m_nodep; }
-    string name() const override { return nodep()->name(); }
+    AstNodeFTask* nodep() const VL_MT_STABLE { return m_nodep; }
+    string name() const override VL_MT_STABLE { return nodep()->name(); }
     string dotColor() const override { return pure() ? "black" : "red"; }
     AstCFunc* cFuncp() const { return m_cFuncp; }
     void cFuncp(AstCFunc* nodep) { m_cFuncp = nodep; }
@@ -80,7 +80,7 @@ public:
     explicit TaskCodeVertex(V3Graph* graphp)
         : TaskBaseVertex{graphp} {}
     ~TaskCodeVertex() override = default;
-    string name() const override { return "*CODE*"; }
+    string name() const override VL_MT_STABLE { return "*CODE*"; }
     string dotColor() const override { return "green"; }
 };
 
diff --git a/src/V3Timing.cpp b/src/V3Timing.cpp
index 0a096661e..afbba68f5 100644
--- a/src/V3Timing.cpp
+++ b/src/V3Timing.cpp
@@ -67,7 +67,7 @@ private:
     class DependencyVertex final : public V3GraphVertex {
         AstNode* const m_nodep;  // AST node represented by this graph vertex
         // ACCESSORS
-        string name() const override {
+        string name() const override VL_MT_STABLE {
             return cvtToHex(nodep()) + ' ' + nodep()->prettyTypeName();
         }
         FileLine* fileline() const override { return nodep()->fileline(); }
diff --git a/src/V3Tristate.cpp b/src/V3Tristate.cpp
index 26f2e0343..0028d2bc8 100644
--- a/src/V3Tristate.cpp
+++ b/src/V3Tristate.cpp
@@ -154,7 +154,7 @@ public:
     // ACCESSORS
     AstNode* nodep() const { return m_nodep; }
     const AstVar* varp() const { return VN_CAST(nodep(), Var); }
-    string name() const override {
+    string name() const override VL_MT_STABLE {
         return ((isTristate() ? "tri\\n"
                  : feedsTri() ? "feed\\n"
                               : "-\\n")
diff --git a/src/V3Waiver.cpp b/src/V3Waiver.cpp
index 606aa0b46..1650fdefa 100644
--- a/src/V3Waiver.cpp
+++ b/src/V3Waiver.cpp
@@ -23,8 +23,9 @@
 #include <memory>
 #include <sstream>
 
-void V3Waiver::addEntry(V3ErrorCode errorCode, const std::string& filename,
-                        const std::string& str) {
+void V3Waiver::addEntry(V3ErrorCode errorCode, const std::string& filename, const std::string& str)
+    VL_MT_SAFE_EXCLUDES(s_mutex) {
+    const VerilatedLockGuard lock{s_mutex};
     std::stringstream entry;
     const size_t pos = str.find('\n');
     entry << "lint_off -rule " << errorCode.ascii() << " -file \"*" << filename << "\" -match \""
@@ -34,7 +35,7 @@ void V3Waiver::addEntry(V3ErrorCode errorCode, const std::string& filename,
     s_waiverList.push_back(entry.str());
 }
 
-void V3Waiver::write(const std::string& filename) {
+void V3Waiver::write(const std::string& filename) VL_MT_SAFE_EXCLUDES(s_mutex) {
     const std::unique_ptr<std::ofstream> ofp{V3File::new_ofstream(filename)};
     if (ofp->fail()) v3fatal("Can't write " << filename);
 
@@ -48,9 +49,12 @@ void V3Waiver::write(const std::string& filename) {
     *ofp << "//   2. Keep the waiver permanently if you are sure this is okay\n";
     *ofp << "//   3. Keep the waiver temporarily to suppress the output\n\n";
 
+    const VerilatedLockGuard lock{s_mutex};
+
     if (s_waiverList.empty()) *ofp << "// No waivers needed - great!\n";
 
     for (const auto& i : s_waiverList) *ofp << "// " << i << "\n\n";
 }
 
+VerilatedMutex V3Waiver::s_mutex;
 V3Waiver::WaiverList V3Waiver::s_waiverList;
diff --git a/src/V3Waiver.h b/src/V3Waiver.h
index 10f711d1c..c8ca73137 100644
--- a/src/V3Waiver.h
+++ b/src/V3Waiver.h
@@ -17,6 +17,8 @@
 #ifndef VERILATOR_V3WAIVER_H_
 #define VERILATOR_V3WAIVER_H_
 
+#include "verilated_threads.h"
+
 #include "V3Error.h"
 
 #include <string>
@@ -25,11 +27,13 @@
 class V3Waiver final {
     // TYPES
     using WaiverList = std::vector<std::string>;
-    static WaiverList s_waiverList;
+    static VerilatedMutex s_mutex;  // Protect members
+    static WaiverList s_waiverList VL_GUARDED_BY(s_mutex);
 
 public:
-    static void addEntry(V3ErrorCode errorCode, const string& filename, const std::string& str);
-    static void write(const std::string& filename);
+    static void addEntry(V3ErrorCode errorCode, const string& filename, const std::string& str)
+        VL_MT_SAFE_EXCLUDES(s_mutex);
+    static void write(const std::string& filename) VL_MT_SAFE_EXCLUDES(s_mutex);
 };
 
 #endif  // Guard