Customize an outpost

The generated application includes an image block for the workspace Devin sees in a new session. Customize that block with the normal modal.Image API.

Before you begin

You need a deployed modal-devin application from Create an outpost.

Open the generated outpost file

Find this block in outposts/my_outpost.py:

base_image = (
    worker.base_image()
    # Add every application-specific build step here.
)

image = worker.prepare_image(base_image)

Install workspace tools

Add packages before prepare_image():

base_image = (
    worker.base_image()
    .apt_install("ripgrep", "jq")
    .pip_install("pytest", "ruff")
)
image = worker.prepare_image(base_image)

Add a repository

The default workspace is /root/workspace:

base_image = (
    worker.base_image()
    .run_commands(
        "git clone https://github.com/your-org/app /root/workspace/app"
    )
)
image = worker.prepare_image(base_image)

Set environment variables

Add non-secret configuration to the image:

base_image = worker.base_image().env(
    {
        "PYTHONUNBUFFERED": "1",
        "PROJECT_ROOT": "/root/workspace/app",
    }
)
image = worker.prepare_image(base_image)

Keep credentials out of image environment variables. Attach a Modal Secret to the function that needs it.

Deploy the changes

uv run modal-devin deploy outposts/my_outpost.py

New sessions use the new image. A resumed session continues from its preserved filesystem instead of merging in later image changes.

Keep every image build operation before prepare_image() and leave the generated image wiring unchanged elsewhere in the application.

Optional tools

Choose the Python version or disable Chrome and FFmpeg when the workload does not need them:

base_image = worker.base_image(
    python_version="3.12",
    install_chrome=False,
    install_ffmpeg=False,
)

Option	Default	Effect
`python_version`	`"3.12"`	Selects the Python version
`install_chrome`	`True`	Enables browser and computer-use support
`install_ffmpeg`	`True`	Enables screen-recording support

See the image reference for everything else the standard image includes.

Tutorials

How-to guides

Concepts

Reference

Before you begin

Optional tools

​Before you begin

​Optional tools

Before you begin

Optional tools