Variable Reference

Archon substitutes variables in command files, inline prompts, and bash scripts before execution. There are three categories of variables: workflow variables (substituted by the workflow engine), positional arguments (substituted by the command handler), and node output references (DAG workflows only).

Workflow Variables

These variables are substituted by the workflow executor in all node types (command:, prompt:, bash:, loop:).

Variable	Resolves to	Notes
$ARGUMENTS	The user’s input message that triggered the workflow	Primary way to pass user input to commands
$USER_MESSAGE	Same as $ARGUMENTS	Alias
$WORKFLOW_ID	Unique ID for the current workflow run	Useful for artifact naming and log correlation
$ARTIFACTS_DIR	Pre-created external artifacts directory (~/.archon/workspaces/<owner>/<repo>/artifacts/runs/<id>/)	Always exists before node execution; stored outside the repo to avoid polluting the working tree
$BASE_BRANCH	Base branch for git operations	Auto-detected from the repository’s default branch, or set via worktree.baseBranch in .archon/config.yaml. Throws an error if referenced in a prompt but cannot be resolved
$DOCS_DIR	Documentation directory path	Configured via docs.path in .archon/config.yaml. Defaults to docs/ when not set. Never throws
$CONTEXT	GitHub issue or PR context, if available	Populated when the workflow is triggered from a GitHub issue/PR. Replaced with empty string when unavailable
$EXTERNAL_CONTEXT	Same as $CONTEXT	Alias
$ISSUE_CONTEXT	Same as $CONTEXT	Alias
$LOOP_USER_INPUT	User feedback from an interactive loop approval gate	Only populated on the first iteration of a resumed interactive loop. Empty string on all other iterations
$REJECTION_REASON	Reviewer feedback from an approval node rejection	Only available in on_reject prompts. Empty string elsewhere

Context Variable Behavior

The three context aliases ($CONTEXT, $EXTERNAL_CONTEXT, $ISSUE_CONTEXT) all resolve to the same value. When no issue context is available, they are replaced with an empty string to avoid sending the literal $CONTEXT text to the AI.

If issue context is present but no context variable appears in the prompt, the context is appended to the end of the prompt automatically. This prevents duplicate context when a command explicitly uses $CONTEXT.

$BASE_BRANCH Fail-Fast

Unlike other variables, $BASE_BRANCH will cause the workflow to fail immediately if:

• The variable is referenced in a prompt, AND
• Auto-detection from git fails, AND
• worktree.baseBranch is not set in .archon/config.yaml

If the variable is not referenced, no error occurs even if the base branch cannot be determined.

Positional Arguments

These variables are substituted by the command handler when commands are invoked directly (outside workflows). They are processed before workflow variables.

Variable	Resolves to	Notes
$1	First positional argument	Split by whitespace from the user’s input
$2	Second positional argument
$3 … $9	Third through ninth positional arguments
$ARGUMENTS	All arguments as a single string	Same variable, available in both contexts
\$	Literal $ character	Escape a dollar sign to prevent substitution

Node Output References

In DAG workflows, nodes can reference the output of any completed upstream node. These are substituted after workflow variables.

Pattern	Resolves to	Notes
$nodeId.output	Full output string of the referenced node	The node must be a declared dependency (in depends_on)
$nodeId.output.field	A specific JSON field from the node’s output	Requires the upstream node to use output_format for structured JSON

Example

nodes:
  - id: classify
    command: classify-issue
    output_format:
      type: object
      properties:
        type: { type: string, enum: [BUG, FEATURE] }
      required: [type]

  - id: fix
    prompt: |
      The issue was classified as: $classify.output.type
      Full classification: $classify.output
      User's original request: $USER_MESSAGE
    depends_on: [classify]

Substitution Order

Variables are substituted in a defined order:

1. Workflow variables — $WORKFLOW_ID, $USER_MESSAGE, $ARGUMENTS, $ARTIFACTS_DIR, $BASE_BRANCH, $DOCS_DIR, $LOOP_USER_INPUT, $REJECTION_REASON
2. Context variables — $CONTEXT, $EXTERNAL_CONTEXT, $ISSUE_CONTEXT
3. Node output references — $nodeId.output, $nodeId.output.field

Positional arguments ($1 through $9) are substituted separately by the command handler and are only available when commands are invoked directly, not through workflow nodes.

Variable Availability by Context

Variable	Workflow nodes	Direct command invocation	when: conditions
$ARGUMENTS / $USER_MESSAGE	Yes	Yes (as $ARGUMENTS)	No
$1 … $9	No	Yes	No
$WORKFLOW_ID	Yes	No	No
$ARTIFACTS_DIR	Yes	No	No
$BASE_BRANCH	Yes	No	No
$DOCS_DIR	Yes	No	No
$CONTEXT / aliases	Yes	No	No
$LOOP_USER_INPUT	Yes (loop nodes)	No	No
$REJECTION_REASON	Yes (on_reject only)	No	No
$nodeId.output	Yes (DAG nodes)	No	Yes