fix: remove duplicate version warning and include CLI path (#720)

## Summary

Two small fixes to the CLI version warning in `_check_claude_version()`:

1. **Remove duplicate output** — The warning was emitted twice: once via
`logger.warning()` and again via `print(..., file=sys.stderr)`. Users
saw the same message repeated. Now only `logger.warning()` is used,
which is the standard library approach for warning output.

2. **Include CLI path in the warning** — When the version is below
minimum, the warning now shows which CLI binary was found (e.g.,
`/opt/node22/bin/claude`), making it easier to diagnose when multiple
CLI installations exist.

Fixes #359, fixes #360

## Changes

- `subprocess_cli.py`: Replace `print()` + `logger.warning(f"...")` with
a single `logger.warning("...", ...)` using lazy `%s` formatting
- `subprocess_cli.py`: Remove now-unused `import sys`
- `test_transport.py`: Add two regression tests:
- `test_version_warning_includes_cli_path` — verifies the warning
includes version and CLI path, and that `print()` is not called
- `test_version_warning_not_emitted_for_current_version` — verifies no
warning for versions at or above minimum

## Verification

- All 329 tests pass (`pytest tests/`)
- Lint clean (`ruff check src/ tests/`)
- Type check clean (`mypy src/`)
- E2E verified with live SDK instance (v0.1.50, CLI 2.1.83) — query
completes successfully

Co-authored-by: Claude <noreply@anthropic.com>

Author: qing-ant

src/claude_agent_sdk/_internal/transport/subprocess_cli.py

@@ -6,7 +6,6 @@
 import platform
 import re
 import shutil
-import sys
 from collections.abc import AsyncIterable, AsyncIterator
 from contextlib import suppress
 from pathlib import Path
@@ -625,13 +624,14 @@ async def _check_claude_version(self) -> None:
                         ]
 
                         if version_parts < min_parts:
-                            warning = (
-                                f"Warning: Claude Code version {version} is unsupported in the Agent SDK. "
-                                f"Minimum required version is {MINIMUM_CLAUDE_CODE_VERSION}. "
-                                "Some features may not work correctly."
+                            logger.warning(
+                                "Claude Code version %s at %s is unsupported in the Agent SDK. "
+                                "Minimum required version is %s. "
+                                "Some features may not work correctly.",
+                                version,
+                                self._cli_path,
+                                MINIMUM_CLAUDE_CODE_VERSION,
                             )
-                            logger.warning(warning)
-                            print(warning, file=sys.stderr)
         except Exception:
             pass
         finally:

tests/test_transport.py

@@ -1064,3 +1064,76 @@ def test_build_command_large_agents_work(self):
         # No @filepath references should exist
         cmd_str = " ".join(cmd)
         assert "@" not in cmd_str
+
+    def test_version_warning_includes_cli_path(self):
+        """Test that the version warning includes the CLI path and uses only logger.warning."""
+
+        async def _test():
+            transport = SubprocessCLITransport(
+                prompt="test",
+                options=make_options(),
+            )
+
+            with (
+                patch("anyio.open_process") as mock_exec,
+                patch(
+                    "claude_agent_sdk._internal.transport.subprocess_cli.logger"
+                ) as mock_logger,
+                patch("builtins.print") as mock_print,
+            ):
+                # Mock version check returning an old version
+                mock_version_process = MagicMock()
+                mock_version_process.stdout = MagicMock()
+                mock_version_process.stdout.receive = AsyncMock(
+                    return_value=b"1.0.0 (Claude Code)"
+                )
+                mock_version_process.terminate = MagicMock()
+                mock_version_process.wait = AsyncMock()
+
+                mock_exec.return_value = mock_version_process
+
+                await transport._check_claude_version()
+
+                # logger.warning should be called with version and CLI path
+                mock_logger.warning.assert_called_once()
+                args, _ = mock_logger.warning.call_args
+                assert args[1] == "1.0.0"
+                assert args[2] == DEFAULT_CLI_PATH
+
+                # print should NOT be called (no duplicate output)
+                mock_print.assert_not_called()
+
+        anyio.run(_test)
+
+    def test_version_warning_not_emitted_for_current_version(self):
+        """Test that no warning is emitted when CLI version meets minimum."""
+
+        async def _test():
+            transport = SubprocessCLITransport(
+                prompt="test",
+                options=make_options(),
+            )
+
+            with (
+                patch("anyio.open_process") as mock_exec,
+                patch(
+                    "claude_agent_sdk._internal.transport.subprocess_cli.logger"
+                ) as mock_logger,
+            ):
+                # Mock version check returning a current version
+                mock_version_process = MagicMock()
+                mock_version_process.stdout = MagicMock()
+                mock_version_process.stdout.receive = AsyncMock(
+                    return_value=b"99.99.99 (Claude Code)"
+                )
+                mock_version_process.terminate = MagicMock()
+                mock_version_process.wait = AsyncMock()
+
+                mock_exec.return_value = mock_version_process
+
+                await transport._check_claude_version()
+
+                # No warning for a current version
+                mock_logger.warning.assert_not_called()
+
+        anyio.run(_test)