Configuration Overview

Squadron uses HCL (HashiCorp Configuration Language) for all configuration.

File Structure

A typical config directory:


my-config/
├── variables.hcl    # Variable definitions
├── models.hcl       # LLM provider configurations
├── agents.hcl       # Agent definitions
├── tools.hcl        # Custom tool definitions (optional)
├── missions.hcl     # Mission definitions (optional)
└── mcp.hcl          # MCP server config (optional)

You can also put everything in a single file—Squadron reads all .hcl files in the directory.

Loading Order

Squadron uses staged evaluation to resolve references:

Variables - Load variable blocks (no context needed)
Plugins - Load plugin blocks with vars context
Models - Load model blocks with vars + plugins context
Tools - Load custom tool blocks with vars + models + plugins context
Agents - Load agent blocks with vars + models + tools + plugins context
Missions - Load mission blocks with full context

This enables expressions like:


model "anthropic" {
  api_key = vars.anthropic_api_key  # Reference a variable
}
 
agent "assistant" {
  model = models.anthropic.claude_sonnet_4  # Reference a model
  tools = [tools.weather]
}

Block Types

Block	Purpose
`variable`	Define configuration variables
`model`	Configure LLM providers
`agent`	Define AI agents
`skill`	Define on-demand capability packages for agents
`tool`	Create custom tools
`plugin`	Load external plugins
`mcp "name"`	Pull tools from an external MCP server (npm, github, http, or bare command)
`mcp_host`	Start a built-in MCP host to expose Squadron to AI clients
`mission`	Define multi-task missions
`commander`	Commander server connection config
`shared_folder`	Shared file folders accessible to missions

Expressions

HCL supports expressions for dynamic values:


# String interpolation
description = "Agent for ${vars.app_name}"
 
# References
api_key = vars.anthropic_api_key
model = models.anthropic.claude_sonnet_4
 
# Lists
tools = [builtins.http.get]

Validation

Always validate your config before running:


squadron verify ./my-config

This catches errors like:

Invalid HCL syntax
Missing variable values
Invalid model references
Circular mission dependencies