Development mounts

Development mounts make your local source files visible inside containers, so you can edit code without rebuilding the image. Your application still needs a watcher or restart to load changed code.

Enable a mount#

Replace app with your module name. Review the proposed mount, then use its printed hash to save the configuration:

mm dev mounts plan app
mm dev mounts configure app --plan PLAN_HASH
mm config stack compile
mm deploy plan
mm deploy apply --plan DEPLOY_PLAN_HASH --yes

Mounts are allowed only for project.development-environment, on the local target, with Docker Compose or Podman Compose advertising bind-mount and volume support. Remote targets and Docker Swarm do not receive a mount or a copied source fallback.

Check the source directory, container path, services, and preserved directories in the plan. If discovery chooses the wrong settings, specify them on both commands:

mm dev mounts plan app --mount-target /app --service web --preset laravel
mm dev mounts configure app --mount-target /app --service web \
  --preset laravel --plan PLAN_HASH

--mount-target selects the container directory; the global --target still selects the runtime target, such as local.

Configuration#

The persisted source is relative to the module, never an absolute workstation path. The generated private runtime artifact resolves it to an absolute host path.

schema-version: 1
project:
  id: 019c527b-6242-7b43-bfd4-bd60e27c1de3
  name: mounted-app
  development-environment: local
target: local

stacks:
  app:
    files: [compose.yaml]

modules:
  app:
    path: app
    services:
      web:
        stack: app
    development-mount:
      source: .
      target: /app
      mode: read-write
      preserve:
        - path: /app/vendor
        - path: /app/storage
        - path: /app/bootstrap/cache
      services: [web]
      preset: laravel
environments:
  local:
    bindings: {}

Use mode: read-only when containers do not need to modify source. Available presets preserve common container-owned paths in managed named volumes:

Preserved directories are initialized from the image on first use. Existing volumes are kept, so reinstall dependencies when their lockfiles change. If a service already mounts application storage through Compose, omit that path from preserve to keep using its existing volume.

For a monorepo with sibling packages, keep the module path at the common build root and declare additional sources relative to that path:

development-mount:
  source: web
  target: /app
  additional:
    - source: packages/commerce
      target: /commerce
  services: [web, worker]
  preserve:
    - path: /app/vendor
    - path: /app/node_modules
  excludes: [.ai]

Additional sources use the same services and read/write mode as the primary source. excludes and protected name directories relative to the primary source; these are masked by empty volumes, not copied from the image. Preserved and masked directories are skipped by the source scan because their host contents are hidden in the container.

Preserved volumes can outlive a changed mount until the next reviewed deployment removes no-longer-referenced, exactly owned volumes. They may hold dependencies, build output, or application data; inspect the deployment plan before cleanup.

Safety#

mm resolves the source and symlinks and requires all content to remain inside both project and module roots. Absolute, drive-qualified, UNC, and .. sources are rejected. The safety scan also rejects .git, non-example .env files, .ssh, private-key files, secrets directories, mm private configuration, and configured sensitive patterns.

For a known false positive, review one exact exception:

mm dev mounts plan app --safe-exception fixtures/test.key

An exception permits that path to enter the container; it does not redact or protect its contents. Prefer narrowing the mount or removing sensitive data.

On SELinux hosts, generated bind mounts request shared relabeling. This can change the host source tree's SELinux context, just like a Compose :z mount. Review that effect before mounting security-sensitive or shared trees.

Disable a mount#

Review the current mount, remove its configuration, then deploy the change:

mm dev mounts plan app
mm dev mounts disable app --plan PLAN_HASH
mm deploy plan
mm deploy apply --plan DEPLOY_PLAN_HASH --yes

mm provides source visibility and stable container paths only. Hot reload, watchers, polling, ownership inside the source tree, and framework cache invalidation remain application concerns.