🔍 Research: GPT-5-Codex capabilities and GitHub PR integration

## Summary
Investigated OpenAI's new GPT-5-Codex model and Codex GitHub PR review integration capabilities.

## GPT-5-Codex Analysis

### Benchmark Performance (Good)
- SWE-bench Verified: 74.5% (vs GPT-5's 72.8%)
- Refactoring tasks: 51.3% (vs GPT-5's 33.9%)
- Code review: Higher developer ratings

### Real-World Issues (Concerning)
- Users report degraded coding performance
- Scripts that previously worked now fail
- Less consistent than GPT-4.5
- Longer response times (minutes vs instant)
- "Creatively and emotionally flat"
- Basic errors (e.g., counting letters incorrectly)

### Key Finding
Classic case of "optimizing for benchmarks vs real usability" - scores well on tests but performs poorly in practice.

## Codex GitHub PR Integration

### Setup Process
1. Enable MFA and connect GitHub account
2. Authorize Codex GitHub app for repos
3. Enable "Code review" in repository settings

### Usage Methods
- **Manual**: Comment '@codex review' in PR
- **Automatic**: Triggers when PR moves from draft to ready

### Current Limitations
- One-way communication (doesn't respond to review comments)
- Prefers creating new PRs over updating existing ones
- Better for single-pass reviews than iterative feedback

## 'codex resume' Feature
New session management capability:
- Resume previous codex exec sessions
- Useful for continuing long tasks across days
- Maintains context from interrupted work

🐱 The investigation reveals that while GPT-5-Codex shows benchmark improvements, practical developer experience has declined - a reminder that metrics don't always reflect real-world utility\!

src/llvm_py/instructions/boxcall.py

@@ -84,6 +84,15 @@ def lower_boxcall(
             vmap[dst_vid] = result
         return
 
+    if method_name == "size":
+        # Map/Array size via any.length_h
+        recv_h = _ensure_handle(builder, module, recv_val)
+        callee = _declare(module, "nyash.any.length_h", i64, [i64])
+        result = builder.call(callee, [recv_h], name="any_size_h")
+        if dst_vid is not None:
+            vmap[dst_vid] = result
+        return
+
     if method_name == "substring":
         # substring(start, end)
         # If receiver is a handle (i64), use handle-based helper; else pointer-based API
@@ -180,23 +189,60 @@ def lower_boxcall(
 
     if method_name == "get":
         # ArrayBox.get(index) → nyash.array.get_h(handle, idx)
+        # MapBox.get(key) → nyash.map.get_hh(handle, key_any)
         recv_h = _ensure_handle(builder, module, recv_val)
         if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
-            idx = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
+            k = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
         else:
-            idx = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
-        callee = _declare(module, "nyash.array.get_h", i64, [i64, i64])
-        res = builder.call(callee, [recv_h, idx], name="arr_get_h")
+            k = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
+        callee_map = _declare(module, "nyash.map.get_hh", i64, [i64, i64])
+        res = builder.call(callee_map, [recv_h, k], name="map_get_hh")
         if dst_vid is not None:
             vmap[dst_vid] = res
-            try:
-                if resolver is not None and hasattr(resolver, 'mark_string'):
-                    # Heuristic: args array often stores strings for CLI; tag as string-ish
-                    resolver.mark_string(dst_vid)
-            except Exception:
-                pass
         return
 
+    if method_name == "push":
+        # ArrayBox.push(val) → nyash.array.push_h(handle, val)
+        recv_h = _ensure_handle(builder, module, recv_val)
+        if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
+            v0 = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
+        else:
+            v0 = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
+        callee = _declare(module, "nyash.array.push_h", i64, [i64, i64])
+        res = builder.call(callee, [recv_h, v0], name="arr_push_h")
+        if dst_vid is not None:
+            vmap[dst_vid] = res
+        return
+
+    if method_name == "set":
+        # MapBox.set(key, val) → nyash.map.set_hh(handle, key_any, val_any)
+        recv_h = _ensure_handle(builder, module, recv_val)
+        if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
+            k = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if len(args) > 0 else ir.Constant(i64, 0)
+            v = resolver.resolve_i64(args[1], builder.block, preds, block_end_values, vmap, bb_map) if len(args) > 1 else ir.Constant(i64, 0)
+        else:
+            k = vmap.get(args[0], ir.Constant(i64, 0)) if len(args) > 0 else ir.Constant(i64, 0)
+            v = vmap.get(args[1], ir.Constant(i64, 0)) if len(args) > 1 else ir.Constant(i64, 0)
+        callee = _declare(module, "nyash.map.set_hh", i64, [i64, i64, i64])
+        res = builder.call(callee, [recv_h, k, v], name="map_set_hh")
+        if dst_vid is not None:
+            vmap[dst_vid] = res
+        return
+
+    if method_name == "has":
+        # MapBox.has(key) → nyash.map.has_hh(handle, key_any)
+        recv_h = _ensure_handle(builder, module, recv_val)
+        if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
+            k = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
+        else:
+            k = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
+        callee = _declare(module, "nyash.map.has_hh", i64, [i64, i64])
+        res = builder.call(callee, [recv_h, k], name="map_has_hh")
+        if dst_vid is not None:
+            vmap[dst_vid] = res
+        return
+
+
     if method_name in ("print", "println", "log"):
         # Console mapping (prefer pointer-API when possible to avoid handle registry mismatch)
         use_ptr = False

src/llvm_py/instructions/newbox.py

@@ -29,9 +29,22 @@ def lower_newbox(
         vmap: Value map
         resolver: Optional resolver for type handling
     """
-    # Use NyRT shim: nyash.env.box.new(type_name: i8*) -> i64
+    # Use NyRT shim: prefer birth_h for core boxes, otherwise env.box.new_i64x
     i64 = ir.IntType(64)
     i8p = ir.IntType(8).as_pointer()
+    # Core fast paths
+    if box_type in ("ArrayBox", "MapBox"):
+        birth_name = "nyash.array.birth_h" if box_type == "ArrayBox" else "nyash.map.birth_h"
+        birth = None
+        for f in module.functions:
+            if f.name == birth_name:
+                birth = f
+                break
+        if not birth:
+            birth = ir.Function(module, ir.FunctionType(i64, []), name=birth_name)
+        handle = builder.call(birth, [], name=f"birth_{box_type}")
+        vmap[dst_vid] = handle
+        return
     # Prefer variadic shim: nyash.env.box.new_i64x(type_name, argc, a1, a2, a3, a4)
     new_i64x = None
     for f in module.functions: