diff --git a/src/coder_eval/orchestrator.py b/src/coder_eval/orchestrator.py
index 83f67da3..c087fd1c 100644
--- a/src/coder_eval/orchestrator.py
+++ b/src/coder_eval/orchestrator.py
@@ -76,6 +76,28 @@
 _WAIT_FOR_GRACE_SECONDS = 2.0
 
 
+def _close_subprocess_transport(proc: asyncio.subprocess.Process | None) -> None:
+    """Release a finished subprocess's pipe transport deterministically.
+
+    ``asyncio`` gives ``Process`` no public way to do this: the transport is held
+    privately and is only closed when the object is garbage-collected. On
+    Windows' Proactor loop ``_ProactorBasePipeTransport.__del__`` then emits
+    ``ResourceWarning: unclosed transport`` — one per pipe — which a strict test
+    run surfaces as ``PytestUnraisableExceptionWarning`` attributed to whichever
+    test happened to be running when the GC fired, not to the code that leaked.
+    That is exactly the shape of the intermittent Windows CI failures in
+    ``test_pre_run`` / ``test_post_run`` / ``test_preservation_mode``.
+
+    Best-effort and idempotent: a second ``close()`` is a no-op, and any error is
+    swallowed because releasing a pipe must never turn into a task failure.
+    """
+    transport = getattr(proc, "_transport", None)
+    if transport is None:
+        return
+    with suppress(Exception):
+        transport.close()
+
+
 async def _pump_stream(
     stream: asyncio.StreamReader | None,
     log_fn: Callable[..., None],
@@ -2172,6 +2194,9 @@ async def _run_command_list(
             start = time.time()
             logger.info("Running %s command: %s", human.lower(), cmd.command)
 
+            # Bound outside the try so the `finally` can tell "never spawned"
+            # (a create_subprocess_shell failure) from "spawned, needs closing".
+            proc: asyncio.subprocess.Process | None = None
             try:
                 proc = await asyncio.create_subprocess_shell(
                     cmd.command,
@@ -2246,6 +2271,13 @@ async def _run_command_list(
                 if fail_on_error:
                     raise RuntimeError(f"{human} command failed: {cmd.command!r}") from e
                 logger.warning("%s command '%s' failed: %s", human, cmd.command, e)
+            finally:
+                # Every exit from this iteration -- normal, `continue` from the
+                # timeout branch, or a raised RuntimeError -- must release the
+                # two pipes this command opened. Without it they survive until
+                # GC, which on Windows reports as an unraisable ResourceWarning
+                # against an unrelated test. See _close_subprocess_transport.
+                _close_subprocess_transport(proc)
 
     async def _run_pre_run_commands(self) -> None:
         """Execute pre-run commands inside the sandbox before evaluation.
diff --git a/uv.lock b/uv.lock
index bbe0e461..211895bb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -2253,11 +2253,11 @@ wheels = [
 
 [[package]]
 name = "sqlparse"
-version = "0.5.5"
+version = "0.6.0"
 source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/90/76/437d71068094df0726366574cf3432a4ed754217b436eb7429415cf2d480/sqlparse-0.5.5.tar.gz", hash = "sha256:e20d4a9b0b8585fdf63b10d30066c7c94c5d7a7ec47c889a2d83a3caa93ff28e", size = 120815, upload-time = "2025-12-19T07:17:45.073Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/5f/d3/3f06a1006f2261d1342aefb3c71eed02f5d4ca5bdbecd86ebc12ad38306e/sqlparse-0.6.0.tar.gz", hash = "sha256:113c35c75365ab9cc9c7231d68c6428fb11c085fc8e9eb1ad659b7ddbf6cd2b9", size = 178477, upload-time = "2026-08-13T19:16:06.396Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/49/4b/359f28a903c13438ef59ebeee215fb25da53066db67b305c125f1c6d2a25/sqlparse-0.5.5-py3-none-any.whl", hash = "sha256:12a08b3bf3eec877c519589833aed092e2444e68240a3577e8e26148acc7b1ba", size = 46138, upload-time = "2025-12-19T07:17:46.573Z" },
+    { url = "https://files.pythonhosted.org/packages/d9/50/f00935da0ec7cbf325f8dc4f772ae46fbc7b672dd62876e73f0a94adda57/sqlparse-0.6.0-py3-none-any.whl", hash = "sha256:b861c0288ce2fa56209a9a6412d2e066ac664b3873b89c26c9d8415e8e32996f", size = 50070, upload-time = "2026-08-13T19:16:04.062Z" },
 ]
 
 [[package]]