diff --git a/src/roe/utils/transport.py b/src/roe/utils/transport.py
index d18fce6..e7f3f12 100644
--- a/src/roe/utils/transport.py
+++ b/src/roe/utils/transport.py
@@ -3,9 +3,9 @@
 Retries failed requests with exponential backoff (capped at ~10 seconds):
 
 - Transport errors: ``httpx.TransportError`` (disconnects, timeouts, etc.).
-- HTTP statuses: ``5xx``, ``408``, ``429``.
-- Applies to **all** HTTP methods, including POST (replay is handled by httpx /
-  rewindable buffers for JSON-encoded bodies).
+  POST and PATCH retry only errors raised before the request was sent, so a
+  timed-out run is never started twice.
+- HTTP statuses: ``5xx``, ``408``, ``429``, for all HTTP methods.
 
 Multipart agent-run helpers opt out via the ``x-roe-skip-retry`` header so
 those POSTs are not retried (non-idempotent streamed bodies).
@@ -26,6 +26,9 @@
 logger = logging.getLogger(__name__)
 
 _BYPASS_HEADER = "x-roe-skip-retry"
+_NON_IDEMPOTENT_METHODS = {"POST", "PATCH"}
+# Raised before any bytes reach the server, so resending cannot duplicate work.
+_UNSENT_ERRORS = (httpx.ConnectError, httpx.ConnectTimeout, httpx.PoolTimeout)
 
 
 def _should_retry_status(status_code: int) -> bool:
@@ -47,7 +50,10 @@ def handle_request(self, request: httpx.Request) -> httpx.Response:
             try:
                 response = super().handle_request(request)
             except httpx.TransportError as exc:
-                if attempt >= self.max_retries:
+                if attempt >= self.max_retries or (
+                    request.method in _NON_IDEMPOTENT_METHODS
+                    and not isinstance(exc, _UNSENT_ERRORS)
+                ):
                     raise
                 wait_time = min(2**attempt, 10)
                 logger.warning(
diff --git a/tests/unit/test_retry_transport.py b/tests/unit/test_retry_transport.py
new file mode 100644
index 0000000..a45b63e
--- /dev/null
+++ b/tests/unit/test_retry_transport.py
@@ -0,0 +1,44 @@
+"""Verify RoeRetryTransport only replays requests that are safe to send twice."""
+
+from __future__ import annotations
+
+import os
+import sys
+
+import httpx
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "src"))
+
+from roe.utils import transport  # noqa: E402
+from roe.utils.transport import RoeRetryTransport  # noqa: E402
+
+
+@pytest.mark.parametrize(
+    ("method", "error", "expected_attempts"),
+    [
+        # The request may already have reached the server: never resend a POST.
+        ("POST", httpx.ReadTimeout, 1),
+        ("PATCH", httpx.RemoteProtocolError, 1),
+        # The request never left the client, so resending is safe.
+        ("POST", httpx.ConnectError, 4),
+        ("POST", httpx.ConnectTimeout, 4),
+        # Idempotent methods keep retrying every transport error.
+        ("GET", httpx.ReadTimeout, 4),
+        ("DELETE", httpx.ReadTimeout, 4),
+    ],
+)
+def test_transport_error_retries(monkeypatch, method, error, expected_attempts):
+    attempts = []
+
+    def fail(self, request):
+        attempts.append(request.method)
+        raise error("boom", request=request)
+
+    monkeypatch.setattr(httpx.HTTPTransport, "handle_request", fail)
+    monkeypatch.setattr(transport.time, "sleep", lambda _: None)
+
+    request = httpx.Request(method, "https://api.roe-ai.com/v1/workflows/w/runs/")
+    with pytest.raises(error):
+        RoeRetryTransport(max_retries=3).handle_request(request)
+    assert len(attempts) == expected_attempts