diff --git a/examples/ffi-objc-arc-01-autoreleasepool.sx b/examples/ffi-objc-arc-01-autoreleasepool.sx
new file mode 100644
index 0000000..d707f28
--- /dev/null
+++ b/examples/ffi-objc-arc-01-autoreleasepool.sx
@@ -0,0 +1,50 @@
+// ffi-objc-arc-01 — M4.A smoke test for NSObject + autoreleasepool.
+//
+// Exercises:
+//   1. NSObject is declared in std/objc.sx and reachable from user code.
+//      `obj.retain()` / `obj.release()` dispatch via the M2.3 #extends-aware
+//      method chain. Pattern: `defer obj.release();` as the canonical
+//      sx idiom for owned Obj-C handles.
+//   2. `autoreleasepool(body)` stdlib helper wraps `body` in a
+//      push/defer-pop pair so Foundation factory returns drain at block
+//      end.
+//
+// macOS-only — libobjc + NSObject must be available at runtime.
+
+#import "modules/std.sx";
+#import "modules/std/objc.sx";
+#import "modules/compiler.sx";
+
+main :: () -> s32 {
+    inline if OS == .macos {
+        // Manual retain/release on an NSObject instance — the
+        // `defer obj.release();` pattern is the canonical sx idiom.
+        obj := NSObject.alloc().init();
+        if obj == null { print("FAIL: alloc null\n"); return 1; }
+        defer obj.release();
+
+        // Bump the count and drop the extra; refcount math stays balanced.
+        _ = obj.retain();
+        obj.release();
+
+        print("retain/release: ok\n");
+
+        // autoreleasepool helper round-trip — just exercise that the
+        // push/pop pair executes. We don't have a side-effect to observe
+        // (NSObject.new returns a +1 retained, NOT autoreleased), so this
+        // is a smoke test of the helper's shape, not the runtime
+        // behavior.
+        autoreleasepool(() => {
+            inner := NSObject.new();
+            if inner != null {
+                inner.release();
+            }
+        });
+
+        print("autoreleasepool: ok\n");
+    }
+    inline if OS != .macos {
+        print("skipped (not macos)\n");
+    }
+    0;
+}
diff --git a/library/modules/platform/uikit.sx b/library/modules/platform/uikit.sx
index 58a2e1f..fa65302 100644
--- a/library/modules/platform/uikit.sx
+++ b/library/modules/platform/uikit.sx
@@ -59,11 +59,13 @@ CGRect :: struct {
 // (split on `_`; each piece becomes a keyword with `:`).
 
 NSValue :: #foreign #objc_class("NSValue") {
+    #extends NSObject;
     // CGRect unboxing — returns by value via the sret/HFA path.
     CGRectValue :: (self: *Self) -> CGRect;
 }
 
 NSNumber :: #foreign #objc_class("NSNumber") {
+    #extends NSObject;
     // Class method (no `self: *Self` first param → static dispatch).
     numberWithBool :: (b: s8) -> *NSNumber;
     // Instance value extractors.
@@ -72,30 +74,36 @@ NSNumber :: #foreign #objc_class("NSNumber") {
 }
 
 NSDictionary :: #foreign #objc_class("NSDictionary") {
+    #extends NSObject;
     objectForKey :: (self: *Self, key: *void) -> *void;
 }
 
 NSMutableDictionary :: #foreign #objc_class("NSMutableDictionary") {
+    #extends NSDictionary;
     dictionary         :: () -> *NSMutableDictionary;
     setObject_forKey   :: (self: *Self, obj: *void, key: *void);
 }
 
 NSSet :: #foreign #objc_class("NSSet") {
+    #extends NSObject;
     anyObject :: (self: *Self) -> *void;
 }
 
 // ── Notifications + Bundle (Phase 3.2 C2) ──────────────────────────────
 
 NSNotification :: #foreign #objc_class("NSNotification") {
+    #extends NSObject;
     userInfo :: (self: *Self) -> *NSDictionary;
 }
 
 NSBundle :: #foreign #objc_class("NSBundle") {
+    #extends NSObject;
     mainBundle   :: () -> *NSBundle;
     resourcePath :: (self: *Self) -> *void;
 }
 
 NSNotificationCenter :: #foreign #objc_class("NSNotificationCenter") {
+    #extends NSObject;
     defaultCenter :: () -> *NSNotificationCenter;
     addObserver_selector_name_object :: (self: *Self, observer: *void, sel: *void, name: *void, obj: *void);
 }
@@ -103,10 +111,12 @@ NSNotificationCenter :: #foreign #objc_class("NSNotificationCenter") {
 // ── RunLoop + display timing (Phase 3.2 C3) ────────────────────────────
 
 NSRunLoop :: #foreign #objc_class("NSRunLoop") {
+    #extends NSObject;
     currentRunLoop :: () -> *NSRunLoop;
 }
 
 CADisplayLink :: #foreign #objc_class("CADisplayLink") {
+    #extends NSObject;
     displayLinkWithTarget_selector :: (target: *void, sel: *void) -> *CADisplayLink;
     addToRunLoop_forMode :: (self: *Self, runloop: *NSRunLoop, mode: *void);
     targetTimestamp :: (self: *Self) -> f64;
@@ -117,6 +127,7 @@ CADisplayLink :: #foreign #objc_class("CADisplayLink") {
 // (Declared before UIView so `layer :: (...) -> *CALayer` can reference it.)
 
 CALayer :: #foreign #objc_class("CALayer") {
+    #extends NSObject;
     setOpaque :: (self: *Self, opaque: s8);
 }
 
@@ -132,6 +143,7 @@ CAMetalLayer :: #foreign #objc_class("CAMetalLayer") {
 }
 
 EAGLContext :: #foreign #objc_class("EAGLContext") {
+    #extends NSObject;
     alloc                            :: () -> *EAGLContext;
     initWithAPI                      :: (self: *Self, api: s32) -> *EAGLContext;
     setCurrentContext                :: (ctx: *EAGLContext);
@@ -142,6 +154,7 @@ EAGLContext :: #foreign #objc_class("EAGLContext") {
 // ── UIKit chrome (Phase 3.2 C4) ────────────────────────────────────────
 
 UIScreen :: #foreign #objc_class("UIScreen") {
+    #extends NSObject;
     mainScreen  :: () -> *UIScreen;
     nativeScale :: (self: *Self) -> f64;
     bounds      :: (self: *Self) -> CGRect;
@@ -152,6 +165,7 @@ UIScreen :: #foreign #objc_class("UIScreen") {
 // participate in lifecycle callbacks (delegates, scene delegates)
 // extend it so the runtime picks up the responder-chain behavior.
 UIResponder :: #foreign #objc_class("UIResponder") {
+    #extends NSObject;
     becomeFirstResponder :: (self: *Self) -> s8;
     resignFirstResponder :: (self: *Self) -> s8;
 }
@@ -165,6 +179,7 @@ UIView :: #foreign #objc_class("UIView") {
 }
 
 UIWindow :: #foreign #objc_class("UIWindow") {
+    #extends UIView;
     alloc                  :: () -> *UIWindow;
     initWithWindowScene    :: (self: *Self, scene: *void) -> *UIWindow;
     setRootViewController  :: (self: *Self, vc: *void);
@@ -173,6 +188,7 @@ UIWindow :: #foreign #objc_class("UIWindow") {
 }
 
 UIViewController :: #foreign #objc_class("UIViewController") {
+    #extends UIResponder;
     alloc   :: () -> *UIViewController;
     init    :: (self: *Self) -> *UIViewController;
     setView :: (self: *Self, view: *void);
diff --git a/library/modules/std/objc.sx b/library/modules/std/objc.sx
index f6b1c2b..f2d4c9d 100644
--- a/library/modules/std/objc.sx
+++ b/library/modules/std/objc.sx
@@ -93,3 +93,50 @@ c_string :: (ns: *void) -> [*]u8 {
     fn_ptr : (*void, *void) -> [*]u8 callconv(.c) = xx objc_msgSend;
     return fn_ptr(ns, sel);
 }
+
+// ─── NSObject (Phase 4 / M4.A) ───────────────────────────────────────────
+// Root of every Obj-C class hierarchy. Apple's runtime supplies the IMPs;
+// sx declares the method surface so user code can write
+// `defer view.release();` and `view.retain()` directly instead of going
+// through `objc_msgSend` casts. M2.3's `#extends`-aware dispatch finds
+// these methods automatically once a class roots its `#extends` chain at
+// NSObject (foreign classes in uikit.sx etc. add `#extends NSObject;` to
+// inherit the surface).
+//
+// `release` is NOT a reserved keyword in sx — modern clang ARC bans
+// user-source calls to it (the ARC compiler emits them automatically), but
+// sx isn't under clang ARC. Calling `view.release()` here is equivalent to
+// pre-ARC Obj-C source code: dispatches through the runtime, decrements the
+// refcount, fires `-dealloc` at zero.
+NSObject :: #foreign #objc_class("NSObject") {
+    alloc       :: () -> *NSObject;
+    init        :: (self: *Self) -> *NSObject;
+    new         :: () -> *NSObject;       // shorthand for [[Cls alloc] init]
+    retain      :: (self: *Self) -> *Self;
+    release     :: (self: *Self);
+    autorelease :: (self: *Self) -> *Self;
+    class       :: () -> *void;            // metaclass query — `Cls.class()`
+    description :: (self: *Self) -> *void;  // returns *NSString
+    hash        :: (self: *Self) -> u64;
+    isEqual_    :: (self: *Self, other: *void) -> BOOL;
+    isKindOfClass_ :: (self: *Self, cls: *void) -> BOOL;
+    respondsToSelector_ :: (self: *Self, sel: *void) -> BOOL;
+}
+
+// ─── Autoreleasepool (M4.A) ──────────────────────────────────────────────
+// Foundation factory methods (`NSString.stringWithUTF8String:`,
+// `[NSArray array]`, ...) return autoreleased objects — valid until the
+// current pool drains. Wrap such code in `autoreleasepool(() => { ... })`
+// so the pool drains deterministically at block end.
+//
+// Stdlib helper, not a language keyword. The closure call adds a frame —
+// for hot loops, inline the push/defer-pop pattern manually.
+
+objc_autoreleasePoolPush :: ()                  -> *void  #foreign objc;
+objc_autoreleasePoolPop  :: (pool: *void)                 #foreign objc;
+
+autoreleasepool :: (body: Closure()) {
+    pool := objc_autoreleasePoolPush();
+    defer objc_autoreleasePoolPop(pool);
+    body();
+}
diff --git a/tests/expected/ffi-objc-arc-01-autoreleasepool.exit b/tests/expected/ffi-objc-arc-01-autoreleasepool.exit
new file mode 100644
index 0000000..573541a
--- /dev/null
+++ b/tests/expected/ffi-objc-arc-01-autoreleasepool.exit
@@ -0,0 +1 @@
+0
diff --git a/tests/expected/ffi-objc-arc-01-autoreleasepool.txt b/tests/expected/ffi-objc-arc-01-autoreleasepool.txt
new file mode 100644
index 0000000..bfb03de
--- /dev/null
+++ b/tests/expected/ffi-objc-arc-01-autoreleasepool.txt
@@ -0,0 +1,2 @@
+retain/release: ok
+autoreleasepool: ok
diff --git a/tests/expected/ffi-objc-call-06-sret-return.ir b/tests/expected/ffi-objc-call-06-sret-return.ir
index e47d423..eddaff3 100644
--- a/tests/expected/ffi-objc-call-06-sret-return.ir
+++ b/tests/expected/ffi-objc-call-06-sret-return.ir
@@ -903,13 +903,13 @@ entry:
     i64 30, label %match.arm.44
     i64 32, label %match.arm.44
     i64 36, label %match.arm.44
-    i64 38, label %match.arm.44
+    i64 39, label %match.arm.44
     i64 34, label %match.arm.45
     i64 35, label %match.arm.45
-    i64 44, label %match.arm.47
-    i64 51, label %match.arm.47
+    i64 45, label %match.arm.47
+    i64 52, label %match.arm.47
     i64 33, label %match.arm.48
-    i64 43, label %match.arm.48
+    i64 44, label %match.arm.48
     i64 17, label %match.arm.49
     i64 20, label %match.arm.49
     i64 22, label %match.arm.49
@@ -918,17 +918,17 @@ entry:
     i64 27, label %match.arm.49
     i64 29, label %match.arm.49
     i64 31, label %match.arm.49
-    i64 39, label %match.arm.49
     i64 40, label %match.arm.49
     i64 41, label %match.arm.49
     i64 42, label %match.arm.49
-    i64 45, label %match.arm.49
+    i64 43, label %match.arm.49
     i64 46, label %match.arm.49
     i64 47, label %match.arm.49
     i64 48, label %match.arm.49
     i64 49, label %match.arm.49
     i64 50, label %match.arm.49
-    i64 52, label %match.arm.49
+    i64 51, label %match.arm.49
+    i64 53, label %match.arm.49
     i64 13, label %match.arm.50
   ]
 
@@ -987,7 +987,7 @@ match.arm.44:                                     ; preds = %entry, %entry, %ent
     i64 30, label %dispatch.case.76
     i64 32, label %dispatch.case.77
     i64 36, label %dispatch.case.78
-    i64 38, label %dispatch.case.79
+    i64 39, label %dispatch.case.79
   ]
 
 match.arm.45:                                     ; preds = %entry, %entry
@@ -1007,8 +1007,8 @@ match.arm.47:                                     ; preds = %entry, %entry
   %loadN = load { i64, i64 }, ptr %alloca, align 8
   %allocaN = alloca { ptr, i64 }, align 8
   switch i64 %loadN, label %dispatch.default.139 [
-    i64 44, label %dispatch.case.140
-    i64 51, label %dispatch.case.141
+    i64 45, label %dispatch.case.140
+    i64 52, label %dispatch.case.141
   ]
 
 match.arm.48:                                     ; preds = %entry, %entry
@@ -1017,7 +1017,7 @@ match.arm.48:                                     ; preds = %entry, %entry
   %allocaN = alloca { ptr, i64 }, align 8
   switch i64 %loadN, label %dispatch.default.153 [
     i64 33, label %dispatch.case.154
-    i64 43, label %dispatch.case.155
+    i64 44, label %dispatch.case.155
   ]
 
 match.arm.49:                                     ; preds = %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry, %entry
@@ -1033,17 +1033,17 @@ match.arm.49:                                     ; preds = %entry, %entry, %ent
     i64 27, label %dispatch.case.173
     i64 29, label %dispatch.case.174
     i64 31, label %dispatch.case.175
-    i64 39, label %dispatch.case.176
-    i64 40, label %dispatch.case.177
-    i64 41, label %dispatch.case.178
-    i64 42, label %dispatch.case.179
-    i64 45, label %dispatch.case.180
-    i64 46, label %dispatch.case.181
-    i64 47, label %dispatch.case.182
-    i64 48, label %dispatch.case.183
-    i64 49, label %dispatch.case.184
-    i64 50, label %dispatch.case.185
-    i64 52, label %dispatch.case.186
+    i64 40, label %dispatch.case.176
+    i64 41, label %dispatch.case.177
+    i64 42, label %dispatch.case.178
+    i64 43, label %dispatch.case.179
+    i64 46, label %dispatch.case.180
+    i64 47, label %dispatch.case.181
+    i64 48, label %dispatch.case.182
+    i64 49, label %dispatch.case.183
+    i64 50, label %dispatch.case.184
+    i64 51, label %dispatch.case.185
+    i64 53, label %dispatch.case.186
   ]
 
 match.arm.50:                                     ; preds = %entry
@@ -1833,6 +1833,15 @@ declare ptr @ns_string(ptr, ptr) #0
 ; Function Attrs: nounwind
 declare ptr @c_string(ptr, ptr) #0
 
+; Function Attrs: nounwind
+declare ptr @objc_autoreleasePoolPush() #0
+
+; Function Attrs: nounwind
+declare void @objc_autoreleasePoolPop(ptr) #0
+
+; Function Attrs: nounwind
+declare void @autoreleasepool(ptr, [2 x i64]) #0
+
 ; Function Attrs: nounwind
 define internal void @triple_imp(ptr sret({ i64, i64, i64 }) %0, ptr %1, ptr %2) #0 {
 entry:
@@ -3610,3 +3619,5 @@ entry:
   store ptr %sel, ptr @OBJC_SELECTOR_REFERENCES_tripleValue, align 8
   ret void
 }
+
+
diff --git a/tests/expected/ffi-objc-dsl-07-mangling-table.ir b/tests/expected/ffi-objc-dsl-07-mangling-table.ir
index 61290dd..c66c53c 100644
--- a/tests/expected/ffi-objc-dsl-07-mangling-table.ir
+++ b/tests/expected/ffi-objc-dsl-07-mangling-table.ir
@@ -798,6 +798,15 @@ declare ptr @ns_string(ptr, ptr) #0
 ; Function Attrs: nounwind
 declare ptr @c_string(ptr, ptr) #0
 
+; Function Attrs: nounwind
+declare ptr @objc_autoreleasePoolPush() #0
+
+; Function Attrs: nounwind
+declare void @objc_autoreleasePoolPop(ptr) #0
+
+; Function Attrs: nounwind
+declare void @autoreleasepool(ptr, [2 x i64]) #0
+
 ; Function Attrs: nounwind
 define internal i32 @universal_imp(ptr %0, ptr %1, i32 %2, i32 %3, i32 %4, i32 %5) #0 {
 entry:
@@ -944,3 +953,5 @@ entry:
   store ptr %selN, ptr @OBJC_SELECTOR_REFERENCES_actualSelectorName, align 8
   ret void
 }
+
+