diff --git a/.gitignore b/.gitignore
index 429fa87..737b20f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ releases/
 *.res
 *.rst
 *.s
+!runtime/src/main/asm/*.s
 
 # Shared / dynamic libraries
 *.so
diff --git a/compiler/src/main/pascal/uCodeGenQBE.pas b/compiler/src/main/pascal/uCodeGenQBE.pas
index 56f81ca..d3c625d 100644
--- a/compiler/src/main/pascal/uCodeGenQBE.pas
+++ b/compiler/src/main/pascal/uCodeGenQBE.pas
@@ -18,9 +18,8 @@ interface
 uses
   SysUtils, StrUtils, Classes, uAST, uSymbolTable, uStrCompat;
 
-// Raw byte copy used by TIRBuffer — maps to libc memcpy under both compilers.
-// FPC: {$linklib c} ensures libc is linked; Blaise links blaise_rtl.a which
-// already pulls in libc.
+// Raw byte copy used by TIRBuffer — maps to libc memcpy.
+// Blaise links blaise_rtl.a which already pulls in libc.
 procedure _ir_memcpy(Dst, Src: Pointer; N: Int64); external name 'memcpy';
 
 type
@@ -2030,7 +2029,7 @@ begin
   Inc(FExcDepth);
 
   SjrTemp := AllocTemp;
-  EmitLine(Format('  %s =w call $setjmp(l %s)', [SjrTemp, FrameTemp]));
+  EmitLine(Format('  %s =w call $_blaise_setjmp(l %s)', [SjrTemp, FrameTemp]));
   EmitLine(Format('  jnz %s, @%s, @%s', [SjrTemp, LblFinExc, LblTry]));
 
   { Normal path: run try body, pop frame, run finally body }
@@ -2078,15 +2077,15 @@ begin
   LblEnd    := AllocLabel('except_end');
 
   { Use a pre-allocated exception frame slot from @start (see EmitExcFrameAllocs).
-    Matches the size contract in blaise_exc.c — must hold jmp_buf (200 B on
-    Linux x86_64, ~312 B on macOS ARM64) plus two pointer fields. }
+    Matches the size contract in blaise_exc.pas — must hold jmp_buf (64 B on
+    x86_64, larger on ARM64) plus two pointer fields. }
   FrameTemp := Format('%%_exc_frame_%d', [FExcFrameNext]);
   FExcFrameNext := FExcFrameNext + 1;
   EmitLine(Format('  call $_PushExcFrame(l %s)', [FrameTemp]));
   Inc(FExcDepth);
 
   SjrTemp := AllocTemp;
-  EmitLine(Format('  %s =w call $setjmp(l %s)', [SjrTemp, FrameTemp]));
+  EmitLine(Format('  %s =w call $_blaise_setjmp(l %s)', [SjrTemp, FrameTemp]));
   EmitLine(Format('  jnz %s, @%s, @%s', [SjrTemp, LblExcept, LblTry]));
 
   { Normal path: run try body, pop frame on clean exit }
diff --git a/compiler/src/test/pascal/cp.test.exceptions.pas b/compiler/src/test/pascal/cp.test.exceptions.pas
index 2301d45..b2e9049 100644
--- a/compiler/src/test/pascal/cp.test.exceptions.pas
+++ b/compiler/src/test/pascal/cp.test.exceptions.pas
@@ -581,7 +581,7 @@ procedure TExceptionTests.TestCodegen_TryExcept_CallsSetjmp;
 var IR: string;
 begin
   IR := GenIR(SrcTryExcept);
-  AssertTrue('try/except calls setjmp', Pos('call $setjmp', IR) > 0);
+  AssertTrue('try/except calls _blaise_setjmp', Pos('call $_blaise_setjmp', IR) > 0);
 end;
 
 procedure TExceptionTests.TestCodegen_TryExcept_PopsFrame;
diff --git a/runtime/Makefile b/runtime/Makefile
index cde1430..da9be85 100644
--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -10,6 +10,7 @@ CFLAGS  = -O2 -Wall -Wextra -std=c11
 
 SRC_DIR     = src/main/c
 PAS_SRC_DIR = src/main/pascal
+ASM_DIR     = src/main/asm
 OBJ_DIR     = target
 LIB         = $(OBJ_DIR)/blaise_rtl.a
 
@@ -19,10 +20,8 @@ COMPILER_BIN = ../compiler/target
 BLAISE       = $(COMPILER_BIN)/blaise
 QBE          = ../vendor/qbe/qbe
 
-# C sources — only those that cannot be expressed in Pascal remain.
-# blaise_exc.c: setjmp/longjmp, type identity, nil-check (QBE cannot express these).
-C_SRCS = $(SRC_DIR)/blaise_exc.c
-C_OBJS = $(patsubst $(SRC_DIR)/%.c,$(OBJ_DIR)/%.o,$(C_SRCS))
+# Assembly sources — platform-specific, no C compiler needed.
+ASM_OBJS = $(OBJ_DIR)/blaise_setjmp_x86_64.o
 
 # Pascal RTL units compiled via the Blaise compiler.
 # Each unit is compiled by a thin driver program; the program section is
@@ -33,9 +32,10 @@ PAS_OBJS = $(OBJ_DIR)/blaise_mem.o \
            $(OBJ_DIR)/blaise_weak.o \
            $(OBJ_DIR)/blaise_float.o \
            $(OBJ_DIR)/blaise_thread.o \
+           $(OBJ_DIR)/blaise_exc.o \
            $(OBJ_DIR)/rtl_platform_posix.o
 
-OBJS = $(C_OBJS) $(PAS_OBJS)
+OBJS = $(ASM_OBJS) $(PAS_OBJS)
 
 .PHONY: all install clean
 
@@ -44,10 +44,10 @@ all: $(LIB)
 $(LIB): $(OBJS)
 	ar rcs $@ $^
 
-# --- C rules ---
-$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c
+# --- Assembly rules ---
+$(OBJ_DIR)/%.o: $(ASM_DIR)/%.s
 	@mkdir -p $(OBJ_DIR)
-	$(CC) $(CFLAGS) -c -o $@ $<
+	$(CC) -c -o $@ $<
 
 # --- Pascal unit rules ---
 # Compile via a build driver, strip everything from '# Generated by Blaise'
@@ -151,6 +151,20 @@ $(OBJ_DIR)/blaise_thread.s: $(OBJ_DIR)/blaise_thread.ssa
 $(OBJ_DIR)/blaise_thread.o: $(OBJ_DIR)/blaise_thread.s
 	$(CC) -c -o $@ $<
 
+$(OBJ_DIR)/blaise_exc.ssa: $(PAS_SRC_DIR)/blaise_exc.pas \
+                            $(PAS_SRC_DIR)/blaise_exc_build_driver.pas
+	@mkdir -p $(OBJ_DIR)
+	$(BLAISE) --source $(PAS_SRC_DIR)/blaise_exc_build_driver.pas \
+	          --unit-path $(PAS_SRC_DIR) \
+	          --emit-ir \
+	| sed '/^# Generated by Blaise/,$$d' > $@
+
+$(OBJ_DIR)/blaise_exc.s: $(OBJ_DIR)/blaise_exc.ssa
+	$(QBE) -o $@ $<
+
+$(OBJ_DIR)/blaise_exc.o: $(OBJ_DIR)/blaise_exc.s
+	$(CC) -c -o $@ $<
+
 install: $(LIB)
 	@mkdir -p $(COMPILER_BIN)
 	cp $(LIB) $(COMPILER_BIN)/blaise_rtl.a
diff --git a/runtime/src/main/asm/blaise_setjmp_x86_64.s b/runtime/src/main/asm/blaise_setjmp_x86_64.s
new file mode 100644
index 0000000..6fd6ed6
--- /dev/null
+++ b/runtime/src/main/asm/blaise_setjmp_x86_64.s
@@ -0,0 +1,72 @@
+#
+# Blaise — An Object Pascal Compiler
+# Copyright (c) 2026 Graeme Geldenhuys
+# SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
+# Licensed under the Apache License v2.0 with Runtime Library Exception.
+# See LICENSE file in the project root for full license terms.
+#
+# Minimal setjmp/longjmp for Blaise exception handling (x86_64, System V ABI).
+#
+# These replace libc setjmp/longjmp so the runtime has zero C dependencies
+# for exception dispatch.  Only callee-saved registers are stored — this is
+# sufficient because the compiler never promotes locals across setjmp (all
+# locals in try-bearing functions remain as stack slots).
+#
+# jmp_buf layout (64 bytes at offset 0 of BlaiseExcFrame):
+#   [0]  RBX
+#   [8]  RBP
+#   [16] R12
+#   [24] R13
+#   [32] R14
+#   [40] R15
+#   [48] RSP  (caller's stack pointer, after return address)
+#   [56] RIP  (return address)
+#
+
+.text
+
+# int _blaise_setjmp(void *buf)
+#   %rdi = pointer to jmp_buf (first 64 bytes of BlaiseExcFrame)
+#   Returns 0 on direct call, non-zero when restored by _blaise_longjmp.
+.globl _blaise_setjmp
+.type  _blaise_setjmp, @function
+_blaise_setjmp:
+    mov  %rbx,    (%rdi)
+    mov  %rbp,   8(%rdi)
+    mov  %r12,  16(%rdi)
+    mov  %r13,  24(%rdi)
+    mov  %r14,  32(%rdi)
+    mov  %r15,  40(%rdi)
+    lea  8(%rsp), %rax          # caller's RSP (skip the return address)
+    mov  %rax,  48(%rdi)
+    mov  (%rsp), %rax           # return address
+    mov  %rax,  56(%rdi)
+    xor  %eax, %eax             # return 0
+    ret
+.size _blaise_setjmp, .-_blaise_setjmp
+
+
+# void _blaise_longjmp(void *buf, int val)
+#   %rdi = pointer to jmp_buf
+#   %esi = return value (passed back through setjmp's return)
+#   Does not return to caller — jumps to the setjmp call site.
+.globl _blaise_longjmp
+.type  _blaise_longjmp, @function
+_blaise_longjmp:
+    mov  %esi, %eax             # return value
+    test %eax, %eax
+    jnz  1f
+    inc  %eax                   # longjmp(buf, 0) must return 1
+1:
+    mov    (%rdi), %rbx
+    mov   8(%rdi), %rbp
+    mov  16(%rdi), %r12
+    mov  24(%rdi), %r13
+    mov  32(%rdi), %r14
+    mov  40(%rdi), %r15
+    mov  48(%rdi), %rsp
+    jmp *56(%rdi)               # jump to saved return address
+.size _blaise_longjmp, .-_blaise_longjmp
+
+
+.section .note.GNU-stack,"",@progbits
diff --git a/runtime/src/main/c/blaise_exc.c b/runtime/src/main/c/blaise_exc.c
deleted file mode 100644
index a3f69fe..0000000
--- a/runtime/src/main/c/blaise_exc.c
+++ /dev/null
@@ -1,228 +0,0 @@
-/*
- * Blaise — An Object Pascal Compiler
- * Copyright (c) 2026 Graeme Geldenhuys
- * SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
- * Licensed under the Apache License v2.0 with Runtime Library Exception.
- * See LICENSE file in the project root for full license terms.
- *
- * Blaise RTL — Exception frame management (Phase 2)
- *
- * Uses setjmp/longjmp for exception dispatch.  Each try block allocates a
- * BlaiseExcFrame on the Pascal stack.  jbuf MUST be at offset 0 so the
- * compiler can pass the frame pointer directly to setjmp.
- *
- * Frame size contract: the compiler allocates BLAISE_EXC_FRAME_ALLOC16 * 16
- * bytes (currently 512) for each try block via QBE alloc16.  This must be >=
- * sizeof(BlaiseExcFrame) on every supported target.
- *
- *   Linux x86_64:  sizeof(jmp_buf) = 200 → frame = 216 bytes  < 512 ✓
- *   macOS ARM64:   sizeof(jmp_buf) ≈ 312 → frame = 328 bytes  < 512 ✓
- */
-
-#include <setjmp.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <string.h>
-
-/* Forward declaration — implemented in blaise_mem.pas.  Blaise strings
-   must be allocated through _BlaiseGetMem so that _StringRelease can
-   free them via _BlaiseFreeMem without a heap mismatch. */
-extern void* _BlaiseGetMem(int32_t size);
-
-/* Forward-declared string helper to build a Blaise string from a C string. */
-static void* exc_str_from_cstr(const char* s) {
-    typedef struct { int32_t refcnt; int32_t length; int32_t capacity; } StrHdr;
-    int32_t len = s ? (int32_t)strlen(s) : 0;
-    StrHdr* h = (StrHdr*)_BlaiseGetMem((int32_t)(sizeof(StrHdr) + len + 1));
-    if (!h) return NULL;
-    h->refcnt = 0; h->length = len; h->capacity = len;
-    if (len > 0) memcpy((char*)(h + 1), s, (size_t)len);
-    ((char*)(h + 1))[len] = '\0';
-    return (void*)h;
-}
-
-typedef struct BlaiseExcFrame {
-    jmp_buf jbuf;       /* offset 0 — frame ptr passed directly to setjmp   */
-    void*   exception;  /* live exception object; NULL on normal path        */
-    void*   prev;       /* previous BlaiseExcFrame* in the thread-local chain */
-} BlaiseExcFrame;
-
-#ifdef _WIN32
-static __declspec(thread) BlaiseExcFrame* g_exc_top        = NULL;
-static __declspec(thread) void*           g_current_exception = NULL;
-#else
-static __thread BlaiseExcFrame* g_exc_top        = NULL;
-static __thread void*           g_current_exception = NULL;
-#endif
-
-/*
- * _PushExcFrame — link a new exception frame into the thread-local chain.
- * Called by the compiler BEFORE setjmp at the start of every try block.
- */
-void _PushExcFrame(void* frame) {
-    BlaiseExcFrame* f = (BlaiseExcFrame*)frame;
-    f->exception = NULL;
-    f->prev      = (void*)g_exc_top;
-    g_exc_top    = f;
-}
-
-/*
- * _PopExcFrame — unlink the top frame.
- * Called on normal exit from a try scope or at the start of an except/finally
- * handler before running handler body.
- */
-void _PopExcFrame(void) {
-    if (g_exc_top)
-        g_exc_top = (BlaiseExcFrame*)g_exc_top->prev;
-}
-
-/*
- * _Raise — raise an exception.  Sets obj on the current frame and longjmps.
- * Aborts if no active handler exists (unhandled exception).
- */
-void _Raise(void* obj) {
-    if (!g_exc_top)
-        abort();
-    g_current_exception  = obj;
-    g_exc_top->exception = obj;
-    longjmp(*(jmp_buf*)g_exc_top, 1);
-}
-
-/*
- * _CurrentException — return the live exception object.
- * Called from an except handler to capture the exception pointer.
- * Uses g_current_exception (set by _Raise) rather than g_exc_top->exception
- * so that bare re-raise inside a typed handler continues to work after
- * _PopExcFrame has already unwound the handler's own frame.
- */
-void* _CurrentException(void) {
-    return g_current_exception;
-}
-
-/*
- * _CurrentExceptionMessage — return the Message string of the current exception.
- * Class layout: offset 0 = vptr (8 bytes), offset 8 = FMessage (string pointer).
- * Returns an empty string if no exception is active.
- */
-void* _CurrentExceptionMessage(void) {
-    /* Use g_current_exception rather than g_exc_top->exception: the codegen
-       calls _PopExcFrame() before running the except body, so g_exc_top has
-       already been unwound by the time CurrentExceptionMessage is called. */
-    void* exc = g_current_exception;
-    if (!exc) return exc_str_from_cstr("");
-    /* FMessage is the first user field, after the 8-byte vptr */
-    void* msg = *((void**)((char*)exc + 8));
-    return msg ? msg : exc_str_from_cstr("");
-}
-
-/*
- * _Reraise — re-raise the given exception to the enclosing handler.
- * Called by the compiler on the exception path of try/finally, after
- * _PopExcFrame has already unlinked the try block's own frame.
- */
-void _Reraise(void* exc) {
-    _Raise(exc);
-}
-
-/* -----------------------------------------------------------------------
- * Type identity — is / as operators
- * ----------------------------------------------------------------------- */
-
-/*
- * BlaiseTypeInfo — one per class/interface, stored as vtable slot 0.
- * parent   = pointer to parent class TypeInfo, or NULL for root classes.
- * impllist = NULL-terminated array of {typeinfo_intf*, itab*} pairs, or NULL
- *            if the class implements no interfaces.
- */
-typedef struct BlaiseTypeInfo {
-    const struct BlaiseTypeInfo* parent;
-    const void**                 impllist;
-} BlaiseTypeInfo;
-
-/*
- * _IsInstance — runtime 'is' check for class inheritance.
- * Walks the TypeInfo parent chain from the object's own TypeInfo upward.
- * Returns 1 if the object is an instance of target (or a subclass), else 0.
- * obj must be non-nil and point to an instance whose first field is the vptr.
- */
-int _IsInstance(void* obj, const BlaiseTypeInfo* target) {
-    const BlaiseTypeInfo* ti;
-    void** vtable;
-    if (!obj || !target) return 0;
-    vtable = *(void***)obj;      /* obj[0] = vptr */
-    ti     = (const BlaiseTypeInfo*)vtable[0];  /* vtable[0] = typeinfo */
-    while (ti) {
-        if (ti == target) return 1;
-        ti = ti->parent;
-    }
-    return 0;
-}
-
-/*
- * _ImplementsInterface — runtime 'is' check for interface membership.
- * Walks the class TypeInfo chain; at each level searches the impllist for
- * a matching interface TypeInfo pointer.
- * Returns 1 if the object's class (or any ancestor) implements the interface.
- */
-int _ImplementsInterface(void* obj, const BlaiseTypeInfo* intf_ti) {
-    const BlaiseTypeInfo* ti;
-    const void**          impl;
-    void**                vtable;
-    if (!obj || !intf_ti) return 0;
-    vtable = *(void***)obj;
-    ti     = (const BlaiseTypeInfo*)vtable[0];
-    while (ti) {
-        impl = ti->impllist;
-        while (impl && *impl) {
-            if ((const BlaiseTypeInfo*)(*impl) == intf_ti) return 1;
-            impl += 2;  /* each entry is {typeinfo*, itab*} — skip both */
-        }
-        ti = ti->parent;
-    }
-    return 0;
-}
-
-/*
- * _GetItab — return the itab pointer for the given object/interface pair.
- * Walks the class TypeInfo chain searching the impllist for a matching
- * interface TypeInfo pointer; returns the associated itab on match.
- * Returns NULL if the object's class does not implement the interface.
- */
-const void* _GetItab(void* obj, const BlaiseTypeInfo* intf_ti) {
-    const BlaiseTypeInfo* ti;
-    const void**          impl;
-    void**                vtable;
-    if (!obj || !intf_ti) return 0;
-    vtable = *(void***)obj;
-    ti     = (const BlaiseTypeInfo*)vtable[0];
-    while (ti) {
-        impl = ti->impllist;
-        while (impl && *impl) {
-            if ((const BlaiseTypeInfo*)(*impl) == intf_ti) return *(impl + 1);
-            impl += 2;
-        }
-        ti = ti->parent;
-    }
-    return 0;
-}
-
-/*
- * _Raise_InvalidCast — raised by the 'as' operator when the type check fails.
- */
-void _Raise_InvalidCast(void) {
-    abort();
-}
-
-/*
- * _CheckNil — abort with a clear message if the object pointer is nil.
- * Emitted by codegen before every method dispatch on a class variable so
- * that calling a method on an uninitialised (nil) object produces a
- * meaningful error instead of silently succeeding or crashing randomly.
- */
-void _CheckNil(void* obj) {
-    if (!obj) {
-        fprintf(stderr, "Runtime error: method call on nil object\n");
-        abort();
-    }
-}
diff --git a/runtime/src/main/pascal/blaise_exc.pas b/runtime/src/main/pascal/blaise_exc.pas
new file mode 100644
index 0000000..19990bf
--- /dev/null
+++ b/runtime/src/main/pascal/blaise_exc.pas
@@ -0,0 +1,268 @@
+{
+  Blaise - An Object Pascal Compiler
+  Copyright (c) 2026 Graeme Geldenhuys
+  SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
+  Licensed under the Apache License v2.0 with Runtime Library Exception.
+  See LICENSE file in the project root for full license terms.
+}
+
+{
+  Blaise RTL — Exception frame management and type identity (pure Pascal)
+
+  Replaces the former blaise_exc.c.  setjmp/longjmp are provided by a
+  platform-specific assembly stub (blaise_setjmp_x86_64.s for x86_64)
+  so the exception subsystem has zero C dependencies.
+
+  Exception frame layout (BlaiseExcFrame):
+    offset  0: jmp_buf  (64 bytes on x86_64 — 8 callee-saved registers)
+    offset 64: exception  (Pointer — live exception object, nil on normal path)
+    offset 72: prev       (Pointer — previous frame in thread-local chain)
+
+  Frame size contract: the compiler allocates 512 bytes via QBE alloc16 for
+  each try block.  This must be >= 80 bytes (64 jmp_buf + 2 pointers) on
+  all supported targets.  The generous allocation leaves room for future
+  ARM64 jmp_buf growth without a compiler change.
+
+  Thread safety: g_exc_top and g_current_exception are plain globals.
+  When threadvar support is added to the language, they should become
+  thread-local.
+}
+
+unit blaise_exc;
+
+interface
+
+procedure _PushExcFrame(Frame: Pointer);
+procedure _PopExcFrame;
+procedure _Raise(Obj: Pointer);
+procedure _Reraise(Exc: Pointer);
+function  _CurrentException: Pointer;
+function  _CurrentExceptionMessage: Pointer;
+function  _IsInstance(Obj: Pointer; Target: Pointer): Integer;
+function  _ImplementsInterface(Obj: Pointer; IntfTI: Pointer): Integer;
+function  _GetItab(Obj: Pointer; IntfTI: Pointer): Pointer;
+procedure _Raise_InvalidCast;
+procedure _CheckNil(Obj: Pointer);
+
+implementation
+
+const
+  OFS_EXCEPTION = 64;
+  OFS_PREV = 72;
+
+type
+  PPointer = ^Pointer;
+
+procedure _blaise_longjmp(Buf: Pointer; Val: Integer); external name '_blaise_longjmp';
+
+function  _BlaiseGetMem(Size: Integer): Pointer; external name '_BlaiseGetMem';
+function  _libc_write(Fd: Integer; Buf: Pointer; Count: Int64): Int64; external name 'write';
+procedure _libc_abort; external name 'abort';
+
+var
+  g_exc_top: Pointer;
+  g_current_exception: Pointer;
+
+function ExcStrEmpty: Pointer;
+var
+  Base: Pointer;
+  RC, LN, CP: ^Integer;
+  Data: PChar;
+begin
+  Base := _BlaiseGetMem(13);
+  if Base = nil then
+  begin
+    Result := nil;
+    Exit;
+  end;
+  RC := Base;
+  RC^ := 0;
+  LN := Base + 4;
+  LN^ := 0;
+  CP := Base + 8;
+  CP^ := 0;
+  Data := PChar(Base + 12);
+  Data[0] := #0;
+  Result := Base + 12;
+end;
+
+procedure _PushExcFrame(Frame: Pointer);
+var
+  ExcSlot: PPointer;
+  PrevSlot: PPointer;
+begin
+  ExcSlot := Frame + OFS_EXCEPTION;
+  ExcSlot^ := nil;
+  PrevSlot := Frame + OFS_PREV;
+  PrevSlot^ := g_exc_top;
+  g_exc_top := Frame;
+end;
+
+procedure _PopExcFrame;
+var
+  PrevSlot: PPointer;
+begin
+  if g_exc_top <> nil then
+  begin
+    PrevSlot := g_exc_top + OFS_PREV;
+    g_exc_top := PrevSlot^;
+  end;
+end;
+
+procedure _Raise(Obj: Pointer);
+var
+  ExcSlot: PPointer;
+begin
+  if g_exc_top = nil then
+    _libc_abort;
+  g_current_exception := Obj;
+  ExcSlot := g_exc_top + OFS_EXCEPTION;
+  ExcSlot^ := Obj;
+  _blaise_longjmp(g_exc_top, 1);
+end;
+
+procedure _Reraise(Exc: Pointer);
+begin
+  _Raise(Exc);
+end;
+
+function _CurrentException: Pointer;
+begin
+  Result := g_current_exception;
+end;
+
+function _CurrentExceptionMessage: Pointer;
+var
+  Exc: Pointer;
+  MsgSlot: PPointer;
+  Msg: Pointer;
+begin
+  Exc := g_current_exception;
+  if Exc = nil then
+  begin
+    Result := ExcStrEmpty;
+    Exit;
+  end;
+  MsgSlot := Exc + 8;
+  Msg := MsgSlot^;
+  if Msg = nil then
+    Result := ExcStrEmpty
+  else
+    Result := Msg;
+end;
+
+{ ------------------------------------------------------------------
+  Type identity — is / as operators
+  ------------------------------------------------------------------
+
+  BlaiseTypeInfo layout (matches the codegen-emitted typeinfo_ data):
+    offset 0: parent    (Pointer — parent class TypeInfo, or nil for root)
+    offset 8: impllist  (Pointer — nil-terminated array of (typeinfo*, itab*) pairs)
+  ------------------------------------------------------------------ }
+
+function _IsInstance(Obj: Pointer; Target: Pointer): Integer;
+var
+  VTable: PPointer;
+  TI: Pointer;
+  ParentSlot: PPointer;
+begin
+  Result := 0;
+  if (Obj = nil) or (Target = nil) then Exit;
+  VTable := PPointer(Obj)^;
+  TI := VTable^;
+  while TI <> nil do
+  begin
+    if TI = Target then
+    begin
+      Result := 1;
+      Exit;
+    end;
+    ParentSlot := TI;
+    TI := ParentSlot^;
+  end;
+end;
+
+function _ImplementsInterface(Obj: Pointer; IntfTI: Pointer): Integer;
+var
+  VTable: PPointer;
+  TI: Pointer;
+  ParentSlot: PPointer;
+  ImplSlot: PPointer;
+  Impl: PPointer;
+begin
+  Result := 0;
+  if (Obj = nil) or (IntfTI = nil) then Exit;
+  VTable := PPointer(Obj)^;
+  TI := VTable^;
+  while TI <> nil do
+  begin
+    ImplSlot := TI + 8;
+    Impl := ImplSlot^;
+    while (Impl <> nil) and (Impl^ <> nil) do
+    begin
+      if Impl^ = IntfTI then
+      begin
+        Result := 1;
+        Exit;
+      end;
+      Impl := Pointer(Impl) + 16;
+    end;
+    ParentSlot := TI;
+    TI := ParentSlot^;
+  end;
+end;
+
+function _GetItab(Obj: Pointer; IntfTI: Pointer): Pointer;
+var
+  VTable: PPointer;
+  TI: Pointer;
+  ParentSlot: PPointer;
+  ImplSlot: PPointer;
+  Impl: PPointer;
+  ItabSlot: PPointer;
+begin
+  Result := nil;
+  if (Obj = nil) or (IntfTI = nil) then Exit;
+  VTable := PPointer(Obj)^;
+  TI := VTable^;
+  while TI <> nil do
+  begin
+    ImplSlot := TI + 8;
+    Impl := ImplSlot^;
+    while (Impl <> nil) and (Impl^ <> nil) do
+    begin
+      if Impl^ = IntfTI then
+      begin
+        ItabSlot := Pointer(Impl) + 8;
+        Result := ItabSlot^;
+        Exit;
+      end;
+      Impl := Pointer(Impl) + 16;
+    end;
+    ParentSlot := TI;
+    TI := ParentSlot^;
+  end;
+end;
+
+procedure DiagAbort(Msg: Pointer; Len: Integer);
+var
+  NL: Byte;
+begin
+  _libc_write(2, Msg, Int64(Len));
+  NL := 10;
+  _libc_write(2, @NL, 1);
+  _libc_abort;
+end;
+
+procedure _Raise_InvalidCast;
+begin
+  DiagAbort('Runtime error: invalid typecast', 31);
+end;
+
+procedure _CheckNil(Obj: Pointer);
+begin
+  if Obj = nil then
+    DiagAbort('Runtime error: method call on nil object', 41);
+end;
+
+end.
diff --git a/runtime/src/main/pascal/blaise_exc_build_driver.pas b/runtime/src/main/pascal/blaise_exc_build_driver.pas
new file mode 100644
index 0000000..a7367bb
--- /dev/null
+++ b/runtime/src/main/pascal/blaise_exc_build_driver.pas
@@ -0,0 +1,17 @@
+{
+  Blaise - An Object Pascal Compiler
+  Copyright (c) 2026 Graeme Geldenhuys
+  SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
+  Licensed under the Apache License v2.0 with Runtime Library Exception.
+  See LICENSE file in the project root for full license terms.
+}
+
+{ Build driver for blaise_exc.pas — used only by the RTL Makefile. }
+
+program blaise_exc_build_driver;
+
+uses
+  blaise_exc;
+
+begin
+end.