terragrunt stack-dependencies supports cross-stack dependency patterns

Introduced 2026-04-21 · score 0.96

HOW TO USE IT

When a stack needs dependencies on another stack or a unit in a nested stack, declare them in `autoinclude` in `terragrunt.stack.hcl` using stack paths and dependency outputs. Plan all units with the `stack-dependencies` experiment enabled.

stack "infra" {
  source = "<stack-source>"
  path   = "infra"
}

unit "app" {
  source = "<unit-source>"
  path   = "app"

  autoinclude {
    dependency "infra" {
      config_path = stack.infra.path
    }
    inputs = {
      vpc_id = dependency.infra.outputs.vpc.vpc_id
    }
  }
}

stack "networking" {
  source = "<stack-source>"
  path   = "networking"
}

unit "app" {
  source = "<unit-source>"
  path   = "app"

  autoinclude {
    dependency "vpc" {
      config_path = stack.networking.vpc.path
    }
    inputs = {
      vpc_id = dependency.vpc.outputs.vpc_id
    }
  }
}

terragrunt run --all --experiment stack-dependencies -- plan

WHY THIS HELPS

Configure a Terragrunt stack so units can depend on another stack or on a unit in a nested stack.

BEFORE THIS CHANGE

Before stack dependencies, stacks passed dependency paths to units through `values`, and units declared `dependency` blocks using those values as `config_path`.

REQUIREMENTS AND LIMITATIONS

Version: v1.0.2
Availability: The `stack-dependencies` experiment.
stack.<name>.path (required): Path reference for depending on the whole named stack.
stack.<name>.<unit_name>.path (required): Path reference for depending on a unit within a nested stack.
dependency.<name>.config_path (required): Path to the dependency configuration; examples set it to a stack path reference.
dependency.<name>.outputs.<unit_name>.<output_key>: Access an output from a unit through a dependency targeting a stack directory; use the dependent stack's name and the unit/output names.
--all: Run the specified OpenTofu/Terraform command against all units in the current stack.
--experiment stack-dependencies (required): Enables the stack-dependencies experiment for the command.
plan (required): OpenTofu/Terraform command passed to `terragrunt run`.
Prerequisite: Enable the `stack-dependencies` experiment for the run with `--experiment stack-dependencies`.
Prerequisite: The stack and unit declarations, including their `source` and `path`, belong in `terragrunt.stack.hcl`; `autoinclude` is nested in the unit or stack declaration.

FIRST-PARTY EVIDENCE

Check the installed version and the source before using it. Entry JSON

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Changes

terragrunt stack-dependencies supports cross-stack dependency patterns