feat: make code agent runs reproducible

docs/code-agent.md

@@ -85,10 +85,13 @@ python scripts/run_code_agent.py \
   --tasks dataset/code_rl_mini.jsonl \
   --base-url http://localhost:8998/v1 \
   --model minimind \
-  --max-attempts 3
+  --max-attempts 3 \
+  --seed 42 \
+  --output out/code_agent.json \
+  --resume
 ```
 
-Hidden-test details are not sent back to the model by default. Add `--reveal-test-details` only for public development tests.
+Each task receives a stable seed range, so the initial attempt remains comparable across single-pass and repair runs. With `--resume`, the output is atomically checkpointed after every task and completed tasks are skipped after an interruption. Hidden-test details are not sent back to the model by default. Add `--reveal-test-details` only for public development tests.
 
 ## Train with verifiable rewards
 

scripts/run_code_agent.py

@@ -11,6 +11,9 @@ sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
 from code_agent import CodeTask, ExecutionFeedbackAgent, OpenAICompatibleGenerator
 
 
+TASK_SEED_STRIDE = 1000
+
+
 def read_tasks(path):
     tasks = []
     with Path(path).open("r", encoding="utf-8") as handle:
@@ -24,6 +27,42 @@ def read_tasks(path):
     return tasks
 
 
+def read_existing_results(path):
+    output_path = Path(path)
+    if not output_path.exists():
+        return []
+    payload = json.loads(output_path.read_text(encoding="utf-8"))
+    results = payload.get("results")
+    if not isinstance(results, list):
+        raise ValueError(f"Invalid agent output at {path}: missing results list")
+    seen = set()
+    for result in results:
+        task_id = str(result.get("task_id", ""))
+        if not task_id or task_id in seen:
+            raise ValueError(f"Invalid agent output at {path}: duplicate or missing task_id")
+        seen.add(task_id)
+    return results
+
+
+def build_output(results):
+    return {
+        "task_count": len(results),
+        "success_count": sum(result["success"] for result in results),
+        "results": results,
+    }
+
+
+def write_output(path, output):
+    output_path = Path(path)
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    temporary_path = output_path.with_suffix(output_path.suffix + ".tmp")
+    temporary_path.write_text(
+        json.dumps(output, ensure_ascii=False, indent=2) + "\n",
+        encoding="utf-8",
+    )
+    temporary_path.replace(output_path)
+
+
 def main():
     parser = argparse.ArgumentParser(description="Generate, execute, and repair Python algorithm solutions")
     parser.add_argument("--tasks", required=True, help="CodeTask JSONL file")
@@ -37,16 +76,33 @@ def main():
     parser.add_argument("--max-attempts", type=int, default=3)
     parser.add_argument("--timeout", type=float, default=2.0)
     parser.add_argument("--memory-mb", type=int, default=256)
+    parser.add_argument("--seed", type=int, default=42, help="Base seed for reproducible task-level generation")
+    parser.add_argument("--resume", action="store_true", help="Resume completed tasks from --output")
     parser.add_argument("--open-thinking", action="store_true")
     parser.add_argument("--reveal-test-details", action="store_true")
     args = parser.parse_args()
 
-    tasks = read_tasks(args.tasks)
+    indexed_tasks = list(enumerate(read_tasks(args.tasks)))
     if args.task_id:
-        tasks = [task for task in tasks if task.task_id == args.task_id]
-        if not tasks:
+        indexed_tasks = [(index, task) for index, task in indexed_tasks if task.task_id == args.task_id]
+        if not indexed_tasks:
             raise ValueError(f"Unknown task id: {args.task_id}")
 
+    if args.resume and not args.output:
+        parser.error("--resume requires --output")
+    expected_task_ids = {task.task_id for _, task in indexed_tasks}
+    existing_results = read_existing_results(args.output) if args.resume else []
+    unexpected_task_ids = {result["task_id"] for result in existing_results} - expected_task_ids
+    if unexpected_task_ids:
+        raise ValueError(
+            f"Existing output contains tasks not selected for this run: {sorted(unexpected_task_ids)}"
+        )
+    results_by_id = {result["task_id"]: result for result in existing_results}
+
+    for position, (task_index, task) in enumerate(indexed_tasks, start=1):
+        if task.task_id in results_by_id:
+            print(f"[{position}/{len(indexed_tasks)}] {task.task_id}: already complete", flush=True)
+            continue
         generator = OpenAICompatibleGenerator(
             base_url=args.base_url,
             api_key=args.api_key,
@@ -54,6 +110,7 @@ def main():
             temperature=args.temperature,
             max_tokens=args.max_tokens,
             open_thinking=args.open_thinking,
+            seed=args.seed + task_index * TASK_SEED_STRIDE,
         )
         agent = ExecutionFeedbackAgent(
             generator,
@@ -62,15 +119,26 @@ def main():
             memory_mb=args.memory_mb,
             reveal_test_details=args.reveal_test_details,
         )
-    results = [agent.run(task).to_dict() for task in tasks]
-    output = {
-        "task_count": len(results),
-        "success_count": sum(result["success"] for result in results),
-        "results": results,
-    }
+        result = agent.run(task).to_dict()
+        results_by_id[task.task_id] = result
+        ordered_results = [
+            results_by_id[selected_task.task_id]
+            for _, selected_task in indexed_tasks
+            if selected_task.task_id in results_by_id
+        ]
+        if args.output:
+            write_output(args.output, build_output(ordered_results))
+        print(
+            f"[{position}/{len(indexed_tasks)}] {task.task_id}: "
+            f"success={result['success']} attempts={result['attempt_count']}",
+            flush=True,
+        )
+
+    results = [results_by_id[task.task_id] for _, task in indexed_tasks]
+    output = build_output(results)
     rendered = json.dumps(output, ensure_ascii=False, indent=2)
     if args.output:
-        Path(args.output).write_text(rendered + "\n", encoding="utf-8")
+        write_output(args.output, output)
     print(rendered)
 
 

tests/test_run_code_agent.py

@@ -0,0 +1,39 @@
+import json
+
+import pytest
+
+from scripts.run_code_agent import build_output, read_existing_results, write_output
+
+
+def test_agent_output_round_trip(tmp_path):
+    output_path = tmp_path / "agent.json"
+    results = [
+        {"task_id": "task-a", "success": True, "attempt_count": 1, "attempts": []},
+        {"task_id": "task-b", "success": False, "attempt_count": 3, "attempts": []},
+    ]
+
+    output = build_output(results)
+    write_output(output_path, output)
+
+    assert json.loads(output_path.read_text(encoding="utf-8")) == output
+    assert read_existing_results(output_path) == results
+    assert output["task_count"] == 2
+    assert output["success_count"] == 1
+
+
+def test_agent_resume_rejects_duplicate_task_ids(tmp_path):
+    output_path = tmp_path / "agent.json"
+    output_path.write_text(
+        json.dumps(
+            {
+                "results": [
+                    {"task_id": "task-a", "success": False},
+                    {"task_id": "task-a", "success": True},
+                ]
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    with pytest.raises(ValueError, match="duplicate or missing task_id"):
+        read_existing_results(output_path)