Skip to content
GitHub Agentic Workflows

Templating

Agentic workflows support three simple templating/substitution mechanisms:

  • GitHub Actions expressions in frontmatter or markdown
  • Conditional Templating blocks in markdown
  • Imports in frontmatter or markdown

GitHub Actions Expressions

Section titled “GitHub Actions Expressions”

Agentic workflows restrict which GitHub Actions expressions can be used in markdown content. This prevents potential security vulnerabilities where access to secrets or environment variables is passed to workflows.

Note: These restrictions apply only to expressions in the markdown content portion of workflows. The YAML frontmatter can still use secrets and environment variables as needed for workflow configuration (e.g., env: and authentication).

Permitted GitHub Actions expressions in markdown content include:

Event properties: Most github.event.* properties (issue/PR numbers, titles, states, SHAs, IDs for comments, deployments, releases, discussions, reviews, workflow runs, etc.)

Repository context: github.actor, github.owner, github.repository, github.server_url, github.workspace, and repository event details

Run metadata: github.run_id, github.run_number, github.job, github.workflow

Pattern expressions: needs.* (job outputs), steps.* (step outputs), and github.event.inputs.* (workflow_dispatch inputs) are also permitted.

Prohibited Expressions

Section titled “Prohibited Expressions”

All other expressions are disallowed, including secrets.*, env.*, vars.*, and complex functions like toJson() or fromJson().

Expression safety is validated during compilation. Unauthorized expressions produce errors like:

error: unauthorized expressions: [secrets.TOKEN, env.MY_VAR].
allowed: [github.repository, github.actor, github.workflow, ...]

Conditional Markdown

Section titled “Conditional Markdown”

Conditional markdown includes or excludes prompt sections based on boolean expressions. The template renderer processes {{#if ...}} ... {{/if}} blocks after GitHub Actions interpolates expressions, evaluating them as truthy or falsy while preserving markdown formatting.

Syntax

Section titled “Syntax”

Template conditionals use a simple mustache-style syntax:

{{#if expression}}
Content to include if expression is truthy
{{/if}}

Automatic Expression Wrapping

Section titled “Automatic Expression Wrapping”

The compiler automatically wraps expressions in {{#if}} blocks with ${{ }} for GitHub Actions evaluation. Writing {{#if github.event.issue.number}} becomes {{#if ${{ github.event.issue.number }} }} automatically, ensuring runtime values are used rather than literal strings. Expressions already wrapped with ${{ are not double-wrapped.

Truthy and Falsy Values

Section titled “Truthy and Falsy Values”

Falsy values (remove content): false, 0, null, undefined, "" (empty string). All other values are truthy (keep content). Evaluation is case-insensitive.

How It Works

Section titled “How It Works”

The compiler wraps expressions with ${{ }} if needed, detects {{#if patterns, and adds a rendering step. During execution, GitHub Actions evaluates expressions, then the renderer processes blocks (keeping truthy content, removing falsy content) and updates the prompt file.

Example

Section titled “Example”
---
on:
  issues:
    types: [opened]
engine: claude
---


# Issue Analysis


Analyze issue #${{ github.event.issue.number }}.


{{#if github.event.issue.number}}
## Issue-Specific Analysis
This section appears only when processing an issue.
You are analyzing issue #${{ github.event.issue.number }}.
{{/if}}


{{#if github.event.pull_request.number}}
## Pull Request Analysis
This section appears only when processing a pull request.
You are analyzing PR #${{ github.event.pull_request.number }}.
{{/if}}

The compiler wraps expressions automatically, so {{#if github.event.issue.number}} becomes {{#if ${{ github.event.issue.number }} }} before GitHub Actions evaluates them.

Limitations

Section titled “Limitations”

The template system intentionally supports only basic conditionals: no nesting, else clauses, variables (beyond ${{ }}), loops, or complex evaluation. This keeps it simple, safe, and predictable.

Section titled “Related Documentation”