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Edit Atmos config, stacks, and vendor manifests without breaking YAML

· 3 min read
Erik Osterman
Erik Osterman
Founder @ Cloud Posse

Atmos can now read and edit your YAML — atmos.yaml, stack manifests, and vendor.yaml — through first-class commands that preserve comments, anchors, YAML functions, and Go templates. No more sed or yq one-liners that strip your comments and reformat the file.

What Changed​

Three new sets of dot-notation get/set/delete commands, all built on a shared, format-preserving YAML engine:

  • atmos config get|set|delete <path> — edit the active atmos.yaml.
  • atmos stack get|set|delete <path> -s <stack> -c <component> — edit a component's value in a stack. Atmos uses provenance to find the manifest that actually defines the effective (post-merge) value and edits that file.
  • atmos vendor get|set <component> [version] — read or pin a vendored component's version, matched by name.
atmos config set logs.level Debug
atmos stack set vars.region us-west-2 -s plat-ue2-prod -c vpc
atmos vendor set vpc v1.5.0

Why This Matters​

Atmos YAML is human-authored: comments explain intent, anchors keep it DRY, and !terraform.output functions and {{ … }} templates carry real behavior. A naive "parse → re-serialize" edit destroys all of that. These commands operate at the node level (via the yq engine Atmos already ships) and are verified to preserve comments, anchors/aliases, Atmos YAML functions, and templates. A strict guard even refuses edits that would silently mutate a value shared through a YAML anchor.

How to Use It​

Paths are dot-notation by default (vars.region, sources[0].version), and --type lets you write typed values (--type=bool, int, float, null, or a raw yaml literal). For stacks, get reports where a value resolves from, and --file lets you target a manifest explicitly. See the config, stack, and vendor command docs.

Bonus: vendor update and diff​

Built on the same engine, two more commands manage vendored components:

  • atmos vendor update checks each Git source for a newer version (honoring per-source semver constraints) and updates the version field in place — preserving comments, anchors, and {{.Version}} templates. Use --check for a dry run and --pull to fetch afterward.
  • atmos vendor diff shows the Git diff between two versions of a component, without a local checkout.

Both use go-git (no git binary required) and the same format-preserving writer.

Get Involved​

This is the foundation for scripted, comment-safe configuration changes across Atmos. A normalize (fmt) command builds on the same engine and is on the way.