[BUG] Critical: UnicodeDecodeError when trying to launch on Windows #51
Description
Describe the bug
When running agentcore launch (CLI) or the Runtime object's launch() method (Python) on Windows, the application fails with a UnicodeDecodeError due to subprocess output being decoded using Windows' default 'charmap' codec instead of UTF-8. This occurs in the container runtime build process when calling Docker commands via subprocess.
The issue occurs because in utils/runtime/container.py, subprocess.Popen is called with text=True but without specifying encoding='utf-8'. On Windows, this causes Python to use the default 'charmap' codec (cp1252) which cannot handle certain UTF-8 bytes. The fix is to explicitly specify encoding='utf-8' in all subprocess calls that use text=True.
I submitted a PR with the fix: #52
To Reproduce
Steps to reproduce the behavior:
- Install bedrock-agentcore-starter-toolkit on Windows
- Configure an agent
- Run
agentcore launchor calllaunch()on theRuntimeobject in Python - See UnicodeDecodeError during Docker build process
Expected behavior
The launch process should complete successfully without encoding errors, properly handling UTF-8 output from subprocess calls.
Error Output
CLI:
$ agentcore launch
Launching Bedrock AgentCore (cloud mode)...
Launching Bedrock AgentCore agent 'mcp_server' to cloud
❌ 'charmap' codec can't decode byte 0x81 in position 14: character maps to <undefined> Python:
UnicodeDecodeError Traceback (most recent call last)
...
File ~\AppData\Roaming\Python\Python313\site-packages\bedrock_agentcore_starter_toolkit\notebook\runtime\bedrock_agentcore.py:130, in Runtime.launch(self, local, push_ecr, env_vars)
127 if not self._config_path:
128 raise ValueError("Must configure before launching. Call .configure() first.")
--> 130 result = launch_bedrock_agentcore(self._config_path, local=local, push_ecr_only=push_ecr, env_vars=env_vars)
132 if result.mode == "cloud":
133 log.info("Deployed to cloud: %s", result.agent_arn)
File ~\AppData\Roaming\Python\Python313\site-packages\bedrock_agentcore_starter_toolkit\operations\runtime\launch.py:58, in launch_bedrock_agentcore(config_path, agent_name, local, push_ecr_only, env_vars)
55 tag = f"bedrock_agentcore-{bedrock_agentcore_name}:latest"
57 # Step 1: Build Docker image
---> 58 success, output = runtime.build(build_dir, tag)
59 if not success:
60 error_lines = output[-10:] if len(output) > 10 else output
File ~\AppData\Roaming\Python\Python313\site-packages\bedrock_agentcore_starter_toolkit\utils\runtime\container.py:205, in ContainerRuntime.build(self, dockerfile_dir, tag, platform)
202 cmd.extend(["--platform", build_platform])
...
File c:\Program Files\Python313\Lib\encodings\cp1252.py:23, in IncrementalDecoder.decode(self, input, final)
22 def decode(self, input, final=False):
---> 23 return codecs.charmap_decode(input,self.errors,decoding_table)[0]
UnicodeDecodeError: 'charmap' codec can't decode byte 0x81 in position 14: character maps to <undefined>Environment:
- OS: Windows 11
- Python version: 3.13.2
- Package version: 0.1.0
- Installation method: any method