[BUG] TLS context not working in 2.39.3.

[jglogan]

Description

Is this a regression? The following works fine in every version I tested back to 2.36.2.

What I see when I build a trivial compose YAML with a TLS context is:

% docker compose build
[+] Building 0.0s (0/0)                                                                                                                                                                                                                                
error during connect: Head "https://192.168.100.2:2376/_ping": remote error: tls: certificate required

This works fine:

docker build -t my-image:latest -f Dockerfile .

Steps To Reproduce

Dockerfile:

FROM alpine:latest
RUN apk add curl

services:
  http-server:
    container_name: http-server
    image: python:slim
    command: [ "python3", "-m", "http.server" ]
    restart: always
    ports:
      - 127.0.0.1:8000:8000
  http-client:
    container_name: http-client
    build:
      context: .
      dockerfile: Dockerfile
    image: my-image:latest
    command: [ "sleep", "3600" ]
    restart: always

Compose Version

% docker compose version
Docker Compose version 2.39.3
% docker-compose version
Docker Compose version 2.39.3

Docker Environment

% docker info
Client: Docker Engine - Community
 Version:    28.4.0
 Context:    test
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.28.0
    Path:     /opt/homebrew/lib/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  2.39.3
    Path:     /opt/homebrew/lib/docker/cli-plugins/docker-compose

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 6
 Server Version: 28.3.0
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.1.12-0-g51d5e946
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.6.9
 Operating System: Alpine Linux v3.22 (containerized)
 OSType: linux
 Architecture: aarch64
 CPUs: 4
 Total Memory: 23.44GiB
 Name: docker
 ID: 811b7624-2bbe-4a46-837e-e7c0b3346696
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Live Restore Enabled: false
 Product License: Community Engine

WARNING: No cpuset support

Anything else?

% docker version
Client: Docker Engine - Community
 Version:           28.4.0
 API version:       1.51
 Go version:        go1.25.0
 Git commit:        d8eb465f86
 Built:             Wed Sep  3 20:52:20 2025
 OS/Arch:           darwin/arm64
 Context:           test

Server: Docker Engine - Community
 Engine:
  Version:          28.3.0
  API version:      1.51 (minimum version 1.24)
  Go version:       go1.24.4
  Git commit:       265f709
  Built:            Tue Jun 24 15:44:06 2025
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          v1.7.27
  GitCommit:        05044ec0a9a75232cad458027ca83437aae3f4da
 runc:
  Version:          1.1.12
  GitCommit:        v1.1.12-0-g51d5e946
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

% docker context inspect
[
    {
        "Name": "test",
        "Metadata": {},
        "Endpoints": {
            "docker": {
                "Host": "tcp://192.168.100.2:2376",
                "SkipTLSVerify": false
            }
        },
        "TLSMaterial": {
            "docker": [
                "ca.pem",
                "cert.pem",
                "key.pem"
            ]
        },
        "Storage": {
            "MetadataPath": "/Users/john/.docker/contexts/meta/2df5712e1cf303a50fac51e4b2c0ac71884f746b20f206f9df2eb6375fde7270",
            "TLSPath": "/Users/john/.docker/contexts/tls/2df5712e1cf303a50fac51e4b2c0ac71884f746b20f206f9df2eb6375fde7270"
        }
    }
]