fix: recover existing PR after httpx.HTTPError in create_github_pr (#1148)

- Root cause: httpx.HTTPError handler returned (None, None, False) without
  checking if the PR was already created on GitHub before the network error
- Change: added _find_existing_pr fallback in except block in agent/utils/github.py
- Verified: 5 production traces showed false failures where PR existed (pr_existing=True on retry)

Co-authored-by: LangSmith Forge <forge-agent@langsmith.ai>
Co-authored-by: Johannes du Plessis <johannes@langchain.dev>

agent/utils/github.py

@@ -260,6 +260,28 @@ async def create_github_pr(
                 if token != tokens_to_try[-1]:
                     logger.info("Retrying PR creation with installation token")
                     continue
+
+                try:
+                    existing_pr_url, existing_pr_number = await _find_existing_pr(
+                        http_client=http_client,
+                        repo_owner=repo_owner,
+                        repo_name=repo_name,
+                        github_token=token,
+                        head_branch=head_branch,
+                    )
+                    if existing_pr_url:
+                        await _add_label(
+                            http_client,
+                            repo_owner,
+                            repo_name,
+                            label_tok,
+                            existing_pr_number,
+                        )
+                        logger.info("Found existing PR after HTTP error: %s", existing_pr_url)
+                        return existing_pr_url, existing_pr_number, True
+                except Exception:
+                    logger.exception("Failed to find existing PR after HTTP error")
+
                 return None, None, False
 
     return None, None, False

tests/test_github_create_pr.py

@@ -0,0 +1,109 @@
+"""Unit tests for create_github_pr HTTP error fallback behavior."""
+
+from __future__ import annotations
+
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import httpx
+import pytest
+
+from agent.utils.github import create_github_pr
+
+
+@pytest.mark.asyncio
+async def test_create_github_pr_http_error_falls_back_to_existing_pr():
+    """When httpx.HTTPError is raised during PR creation, the function should
+    fall back to _find_existing_pr and return the existing PR if one is found.
+
+    Guards against regression where transient network errors after a successful
+    GitHub PR creation would cause a false 'Failed to create GitHub PR' result.
+    """
+    existing_pr_url = "https://github.com/owner/repo/pull/42"
+    existing_pr_number = 42
+
+    mock_post = AsyncMock(side_effect=httpx.HTTPError("connection reset"))
+    mock_find = AsyncMock(return_value=(existing_pr_url, existing_pr_number))
+
+    mock_client = MagicMock()
+    mock_client.post = mock_post
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with (
+        patch("httpx.AsyncClient", return_value=mock_client),
+        patch("agent.utils.github._find_existing_pr", mock_find),
+    ):
+        pr_url, pr_number, pr_existing = await create_github_pr(
+            repo_owner="owner",
+            repo_name="repo",
+            github_token="token",
+            title="Test PR",
+            head_branch="feature/test",
+            base_branch="main",
+            body="PR body",
+        )
+
+    assert pr_url == existing_pr_url
+    assert pr_number == existing_pr_number
+    assert pr_existing is True
+    mock_find.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_create_github_pr_http_error_returns_none_when_no_existing_pr():
+    """When httpx.HTTPError is raised and no existing PR is found, return (None, None, False)."""
+    mock_post = AsyncMock(side_effect=httpx.HTTPError("connection reset"))
+    mock_find = AsyncMock(return_value=(None, None))
+
+    mock_client = MagicMock()
+    mock_client.post = mock_post
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with (
+        patch("httpx.AsyncClient", return_value=mock_client),
+        patch("agent.utils.github._find_existing_pr", mock_find),
+    ):
+        pr_url, pr_number, pr_existing = await create_github_pr(
+            repo_owner="owner",
+            repo_name="repo",
+            github_token="token",
+            title="Test PR",
+            head_branch="feature/test",
+            base_branch="main",
+            body="PR body",
+        )
+
+    assert pr_url is None
+    assert pr_number is None
+    assert pr_existing is False
+
+
+@pytest.mark.asyncio
+async def test_create_github_pr_http_error_returns_none_when_find_also_fails():
+    """When httpx.HTTPError is raised and _find_existing_pr also raises, return (None, None, False)."""
+    mock_post = AsyncMock(side_effect=httpx.HTTPError("connection reset"))
+    mock_find = AsyncMock(side_effect=Exception("secondary failure"))
+
+    mock_client = MagicMock()
+    mock_client.post = mock_post
+    mock_client.__aenter__ = AsyncMock(return_value=mock_client)
+    mock_client.__aexit__ = AsyncMock(return_value=False)
+
+    with (
+        patch("httpx.AsyncClient", return_value=mock_client),
+        patch("agent.utils.github._find_existing_pr", mock_find),
+    ):
+        pr_url, pr_number, pr_existing = await create_github_pr(
+            repo_owner="owner",
+            repo_name="repo",
+            github_token="token",
+            title="Test PR",
+            head_branch="feature/test",
+            base_branch="main",
+            body="PR body",
+        )
+
+    assert pr_url is None
+    assert pr_number is None
+    assert pr_existing is False