MCP servers: (finch build failures with UV_PYTHON_PREFERENCE=only-system)

[rickosaws]

Describe the bug

When using finch build -t awslabs/aws-documentation-mcp-server . the aws-documentation-mcp-server fails with missing interpreter error during the build phase.

[uv 6/7] RUN --mount=type=cache,target=/root/.cache/uv uv sync --frozen --no-dev --no-editable:
0.133 error: No interpreter found for Python 3.10 in search path

Expected Behavior

Container image should build successfully.

Current Behavior

Build fails with the following errors

[uv 6/7] RUN --mount=type=cache,target=/root/.cache/uv uv sync --frozen --no-dev --no-editable:
0.133 error: No interpreter found for Python 3.10 in search path

Reproduction Steps

Setting or leaving UV_PYTHON_PREFERENCE=only-system in the DockerFile and running finch build -t awslabs/aws-documentation-mcp-server .

Possible Solution

This can currently be worked around by setting UV_PYTHON_PREFERENCE=managed in the Dockerfile

Additional Information/Context

I am using finch instead of docker for my container build commands

OS

Mac OS 15.4.1

Server

aws-documentation-mcp-server

Server Version

No response

Region experiencing the issue

all

Other information

No response

Service quota

• I have reviewed the service quotas for this construct

[krokoko]

Hi @rickosaws , thank you for reporting this. I think this issue is global to all servers and not specific to the documentation server. I'll update the title to reflect it

[krokoko]

Hi @rickosaws , I am not able to reproduce the issue. I am using Finch version v1.8.0, on Mac OS 15.4.1
When building the image:

finch build -t finch-doc .
[+] Building 33.0s (16/16) FINISHED                                                                                                                                                          
 => [internal] load build definition from Dockerfile                                                                                                                                    0.0s
 => => transferring dockerfile: 2.87kB                                                                                                                                                  0.0s
 => [internal] load metadata for public.ecr.aws/sam/build-python3.13@sha256:06115a411095d035cb10ddc720c9f41ae54c11350e6594fd4ed3b9677ca30ab4                                            1.5s
 => [internal] load .dockerignore                                                                                                                                                       0.0s
 => => transferring context: 2B                                                                                                                                                         0.0s
 => [uv 1/7] FROM public.ecr.aws/sam/build-python3.13@sha256:06115a411095d035cb10ddc720c9f41ae54c11350e6594fd4ed3b9677ca30ab4                                                          20.6s
 => => resolve public.ecr.aws/sam/build-python3.13@sha256:06115a411095d035cb10ddc720c9f41ae54c11350e6594fd4ed3b9677ca30ab4                                                              0.0s
 => => sha256:93c5ea111c396ee8120936ed0daee82b72a2d8ee84623d1ce39c0833205a0187 122.18kB / 122.18kB                                                                                      0.4s
 => => sha256:9d817008d0d914f2689b4d2785181fcf03da47de80969c92dea61341ba5eae0d 266.11kB / 266.11kB                                                                                      0.5s
 => => sha256:b21b5474569884f61781ed3943108cb9e1e6daf03f074b32a2c2a5a7b0598a8d 5.79MB / 5.79MB                                                                                          0.8s
 => => sha256:92980e542e769e7ca764006e1e2531b0abd7c3675a4c7294634bd0e647d0e89c 1.84MB / 1.84MB                                                                                          0.7s
 => => sha256:2a80365874c7f8b70be4df50febd76960867cb1cbac3e2a669f85dc08d7bd806 3.36MB / 3.36MB                                                                                          0.6s
 => => sha256:fe186d8fab3f6200259573b0db1b76586f0242b5bce053dc178505497ed1cde6 5.20kB / 5.20kB                                                                                          0.2s
 => => sha256:8a5dbaa5621da2fd67eab298a7a646e7164b45f5317e8dab3381f0a54ef00030 71.51MB / 71.51MB                                                                                        4.2s
 => => sha256:6bb585419a1426894b978eef533c2243b9843913533779747e70db20ab49aa89 65.16MB / 65.16MB                                                                                        3.8s
 => => sha256:b0589c6e646867ec107ec9f4508d173b33d2a7dd31bdcaa54613334da1ad4136 234.32MB / 234.32MB                                                                                     14.8s
 => => sha256:2a707c02db07cfbd025062641e27e8f05e4e10051dfbfedc752d2014b2e87cd0 106.65MB / 106.65MB                                                                                      6.0s
 => => sha256:c3f1bcf14f4a2a9f7a467d7efead40d6f1a88f4e1e0edef2b109867b3efb602c 14.19kB / 14.19kB                                                                                        0.3s
 => => sha256:75a7504cbcbc31bb6edee338ec7e9d8fb8110880d441e374a4a1847b4dc8c3c8 150.84MB / 150.84MB                                                                                      8.8s
 => => sha256:976b40d4bc882ddc62ec3d38813ac419a080910f7f848481fc3ba9166be52886 2.47MB / 2.47MB                                                                                          0.6s
 => => sha256:0e7d2f8a9687cfcfc220f12af82a48ad361cf061a1340e5f20935dd8b4f5e00c 417B / 417B                                                                                              0.3s
 => => sha256:42a31152db1111831a295ec5bc9066fe0c30d4a0952dcc46b6c09f42a4f43ce3 88.12kB / 88.12kB                                                                                        0.4s
 => => sha256:482d407cae38204df76abb15b41a6706500457c899b2193adbb49d7c6d102805 37.90MB / 37.90MB                                                                                        2.2s
 => => extracting sha256:482d407cae38204df76abb15b41a6706500457c899b2193adbb49d7c6d102805                                                                                               0.6s
 => => extracting sha256:42a31152db1111831a295ec5bc9066fe0c30d4a0952dcc46b6c09f42a4f43ce3                                                                                               0.0s
 => => extracting sha256:0e7d2f8a9687cfcfc220f12af82a48ad361cf061a1340e5f20935dd8b4f5e00c                                                                                               0.0s
 => => extracting sha256:976b40d4bc882ddc62ec3d38813ac419a080910f7f848481fc3ba9166be52886                                                                                               0.0s
 => => extracting sha256:75a7504cbcbc31bb6edee338ec7e9d8fb8110880d441e374a4a1847b4dc8c3c8                                                                                               1.4s
 => => extracting sha256:c3f1bcf14f4a2a9f7a467d7efead40d6f1a88f4e1e0edef2b109867b3efb602c                                                                                               0.0s
 => => extracting sha256:2a707c02db07cfbd025062641e27e8f05e4e10051dfbfedc752d2014b2e87cd0                                                                                               0.9s
 => => extracting sha256:b0589c6e646867ec107ec9f4508d173b33d2a7dd31bdcaa54613334da1ad4136                                                                                               2.3s
 => => extracting sha256:6bb585419a1426894b978eef533c2243b9843913533779747e70db20ab49aa89                                                                                               0.9s
 => => extracting sha256:8a5dbaa5621da2fd67eab298a7a646e7164b45f5317e8dab3381f0a54ef00030                                                                                               1.0s
 => => extracting sha256:fe186d8fab3f6200259573b0db1b76586f0242b5bce053dc178505497ed1cde6                                                                                               0.0s
 => => extracting sha256:92980e542e769e7ca764006e1e2531b0abd7c3675a4c7294634bd0e647d0e89c                                                                                               0.0s
 => => extracting sha256:b21b5474569884f61781ed3943108cb9e1e6daf03f074b32a2c2a5a7b0598a8d                                                                                               0.1s
 => => extracting sha256:2a80365874c7f8b70be4df50febd76960867cb1cbac3e2a669f85dc08d7bd806                                                                                               0.1s
 => => extracting sha256:9d817008d0d914f2689b4d2785181fcf03da47de80969c92dea61341ba5eae0d                                                                                               0.0s
 => => extracting sha256:93c5ea111c396ee8120936ed0daee82b72a2d8ee84623d1ce39c0833205a0187                                                                                               0.0s
 => [internal] load build context                                                                                                                                                       3.5s
 => => transferring context: 79.20MB                                                                                                                                                    3.4s
 => [uv 2/7] WORKDIR /app                                                                                                                                                               0.4s
 => [stage-1 2/5] RUN dnf update -y &&     dnf install -y lsof &&     dnf clean all -y &&     rm -rf /var/cache/dnf &&     groupadd --force --system app &&     useradd app -g app -d   9.8s
 => [uv 3/7] COPY pyproject.toml uv.lock ./                                                                                                                                             0.0s
 => [uv 4/7] RUN --mount=type=cache,target=/root/.cache/uv     pip install uv &&     uv sync --frozen --no-install-project --no-dev --no-editable                                       2.1s
 => [uv 5/7] COPY . /app                                                                                                                                                                0.5s
 => [uv 6/7] RUN --mount=type=cache,target=/root/.cache/uv     uv sync --frozen --no-dev --no-editable                                                                                  1.1s
 => [uv 7/7] RUN mkdir -p /root/.local                                                                                                                                                  0.1s
 => [stage-1 3/5] COPY --from=uv --chown=app:app /root/.local /root/.local                                                                                                              0.0s
 => [stage-1 4/5] COPY --from=uv --chown=app:app /app/.venv /app/.venv                                                                                                                  0.1s
 => [stage-1 5/5] COPY ./docker-healthcheck.sh /usr/local/bin/docker-healthcheck.sh                                                                                                     0.0s
 => exporting to image                                                                                                                                                                  0.9s
 => => exporting layers                                                                                                                                                                 0.7s
 => => exporting manifest sha256:c3072bb7ca25439a722536ada74b66128f9d251ab62acd9fcc1144693f016ddf                                                                                       0.0s
 => => exporting config sha256:4912e83b7d923452842471e00e08cc9613af720a224e8b934b1fd597e8c90f9c                                                                                         0.0s
 => => naming to docker.io/library/finch-doc:latest                                                                                                                                     0.0s
 => => unpacking to docker.io/library/finch-doc:latest  

Are you using the latest version of Finch and of this repo ? Thank you

[rickosaws]

Thanks for checking on this @krokoko - im also unable to reproduce after upgrading to the latest version of finch. Ill close this