[BUG] CodeBuild Fails When Entrypoint is in Subdirectory: Incorrect Build Context

[DennisTraub]

Summary

When using agentcore configure with an entrypoint located in a subdirectory (e.g., server/server.py), the Docker build fails during CodeBuild with the error "/server": not found. The root cause is that the generated Dockerfile attempts to COPY a subdirectory that doesn't exist in the Docker build context.

Environment

• Tool: bedrock-agentcore-starter-toolkit (via uv run agentcore)
• Platform: Windows
• Deployment Type: Container

Steps to Reproduce

1. Create a parent project with agentcore:

uv init --bare
uv add bedrock-agentcore-starter-toolkit

2. Create a subdirectory for the deployable:

mkdir server && cd server
uv init --bare --no-workspace
uv add mcp

3. Create a simple MCP server (server/server.py):

from mcp.server.fastmcp import FastMCP

mcp = FastMCP(name="EchoServer", stateless_http=True)

def main():
    mcp.run(transport="streamable-http")

if __name__ == "__main__":
    main()

4. Return to parent directory and configure agentcore:

cd ..
uv run agentcore configure \
   --entrypoint server/server.py \
   --requirements-file server/pyproject.toml \
   --non-interactive --disable-memory --disable-otel \
   --name test_server --protocol MCP \
   --deployment-type container

5. Launch the agent:

uv run agentcore launch --agent test_server

Expected Behavior

The CodeBuild project should succeed and the container should be deployed to ECR.

Actual Behavior

The tookit fails with:

🔄 COMPLETED started (total: 12s)
⠋ Launching Bedrock AgentCore...❌ Build failed during COMPLETED phase
❌ CodeBuild failed with status: FAILED

The CodeBuild project fails with:

#6 ERROR: failed to calculate checksum of ref 3dbb0167-26e0-4aa8-afd6-f9e595d75983::wes51ujh9l3i1ahked3byxdc7: "/server": not found
...
------
> [3/6] COPY server server:
------
Dockerfile:15
--------------------
13 \|
14 \|
15 \| >>> COPY server server
16 \|     # Install from pyproject.toml directory
17 \|     RUN cd server && uv pip install .
--------------------
ERROR: failed to build: failed to solve: failed to compute cache key: failed to calculate checksum of ref 3dbb0167-26e0-4aa8-afd6-f9e595d75983::wes51ujh9l3i1ahked3byxdc7: "/server": not found
Docker build failed

Root Cause Analysis

The issue occurs because of a mismatch between the Docker build context and the Dockerfile's COPY instruction:

1. Build Context: When agentcore detects the entrypoint is in a subdirectory (server/server.py), it sets source_path to the subdirectory:

   source_path: C:\Users\traubd\code\GitHub\code\examples\temp\server

2. Dockerfile Generation: The generated Dockerfile attempts to copy the subdirectory relative to the build context:

   COPY server server
   RUN cd server && uv pip install .

3. The Problem: Since the build context is already set to the server directory, there is no server subdirectory to copy. The Dockerfile is trying to copy server/server which doesn't exist.

Proposed Solution

When the source_path is set to a subdirectory, the Dockerfile should copy from the current directory (.) instead of trying to copy a subdirectory that doesn't exist in the build context.

The Dockerfile generation logic should be updated to:

• Detect when source_path points to a subdirectory
• Generate COPY . . (or copy specific files) instead of COPY <subdirectory> <subdirectory>
• Adjust the RUN command to install from the current directory: RUN uv pip install .

Example corrected Dockerfile:

FROM ghcr.io/astral-sh/uv:python3.12-bookworm-slim
WORKDIR /app

ENV UV_SYSTEM_PYTHON=1 \
    UV_COMPILE_BYTECODE=1 \
    UV_NO_PROGRESS=1 \
    PYTHONUNBUFFERED=1 \
    DOCKER_CONTAINER=1

# Copy and install from current directory (which is already the server directory)
COPY . .
RUN uv pip install .

# Create non-root user
RUN useradd -m -u 1000 bedrock_agentcore
USER bedrock_agentcore

EXPOSE 9000 8000 8080

CMD ["python", "-m", "server"]

Workaround

Currently, users must place their files in the root directory of the project rather than in a subdirectory.

Additional Context

This issue affects common project structures where developers organize their code into subdirectories (e.g., server/, src/, app/) rather than placing everything in the root directory.

[tejaskash]

Taking a look.