fix: support harness codex model override

scripts/execute.py

@@ -25,6 +25,12 @@ from typing import Optional
 ROOT = Path(__file__).resolve().parent.parent
 
 
+def configure_output_encoding():
+    for stream in (sys.stdout, sys.stderr):
+        if hasattr(stream, "reconfigure"):
+            stream.reconfigure(encoding="utf-8", errors="replace")
+
+
 @contextlib.contextmanager
 def progress_indicator(label: str):
     """터미널 진행 표시기. with 문으로 사용하며 .elapsed 로 경과 시간을 읽는다."""
@@ -374,7 +380,7 @@ class StepExecutor:
 
         prompt = preamble + step_file.read_text(encoding="utf-8")
         result = subprocess.run(
-            [self._codex_command(), "exec", "--dangerously-bypass-approvals-and-sandbox", "--json", "-"],
+            self._codex_exec_command(),
             cwd=self._root, capture_output=True, text=True, input=prompt,
             encoding="utf-8", errors="replace", timeout=1800,
         )
@@ -406,6 +412,14 @@ class StepExecutor:
             or "codex"
         )
 
+    def _codex_exec_command(self) -> list[str]:
+        cmd = [self._codex_command(), "exec"]
+        model = os.environ.get("HARNESS_CODEX_MODEL", "").strip()
+        if model:
+            cmd.extend(["-m", model])
+        cmd.extend(["--dangerously-bypass-approvals-and-sandbox", "--json", "-"])
+        return cmd
+
     def _print_header(self):
         print(f"\n{'='*60}")
         print(f"  Harness Step Executor")
@@ -561,6 +575,7 @@ class StepExecutor:
 
 
 def main():
+    configure_output_encoding()
     parser = argparse.ArgumentParser(description="Harness Step Executor")
     parser.add_argument("phase_dir", help="Phase directory name (e.g. 0-mvp)")
     parser.add_argument("--push", action="store_true", help="Push branch after completion")