Claude Code’s latest release (v2.1.9x) adds initialPrompt — a YAML frontmatter field that auto-submits a first turn when a subagent is spawned. This guide shows you exactly how to use it.

What You’ll Accomplish

By the end of this guide, you’ll have subagents that start executing immediately when invoked — no manual prompting required.

Prerequisites

  • Claude Code v2.1.9x or later (claude --version to check)
  • An existing Claude Code project with at least one subagent definition
  • Basic familiarity with YAML frontmatter in agent files

Step 1: Update Claude Code

First, make sure you’re on the latest version:

# Homebrew
brew upgrade claude-code

# Verify
claude --version

The initialPrompt field is not available in earlier versions. Attempting to use it on older versions will either silently ignore the field or raise a frontmatter validation error.

Step 2: Understand the Frontmatter Format

A Claude Code subagent is defined in a Markdown file (.md extension) inside your project’s .claude/agents/ directory. The file starts with YAML frontmatter.

Before initialPrompt:

---
name: my-researcher
description: Searches and summarizes AI news
---

You are a research agent. When given a topic, search for recent news and return a summary.

With initialPrompt:

---
name: my-researcher
description: Searches and summarizes AI news
initialPrompt: "Search for the latest AI agent news from the past 24 hours and return a structured summary with the top 5 stories."
---

You are a research agent. When given a topic, search for recent news and return a summary.

The initialPrompt value is submitted as the first user turn when the subagent is invoked. The agent’s system prompt (the body of the file, below the frontmatter) is still applied — initialPrompt is an additional first message, not a replacement for the system prompt.

Step 3: Create Your First Self-Starting Agent

Create the agents directory if it doesn’t exist:

mkdir -p .claude/agents

Create a new agent file:

cat > .claude/agents/daily-news-researcher.md << 'EOF'
---
name: daily-news-researcher
description: Fetches and summarizes today's AI agent news
initialPrompt: "Start your daily research session. Search for AI agent news published in the last 24 hours. Return a structured list of the top 5 stories with title, source, and 2-sentence summary for each."
---

You are a focused research agent for subagentic.ai. Your job is to find high-signal AI agent news.

Search tools you have access to:
- web_search: For broad web coverage
- news_search: For news-specific results with freshness filtering

Always include source URLs in your output. Prioritize original reporting over aggregators.
EOF```

## Step 4: Invoke the Agent and Watch It Self-Start

From your main Claude Code session, invoke the agent:

/agents daily-news-researcher


Or programmatically via the SDK:

```python
# In your orchestrator agent
Task(
    description="Run the daily news research cycle",
    subagent_type="daily-news-researcher"
    # No 'prompt' field needed — initialPrompt handles the first turn
)

The agent will immediately begin executing the initialPrompt without waiting for additional input.

Step 5: Patterns and Best Practices

Pattern 1: Pipeline Stage Kickstart

For pipeline-style orchestration where each stage has a well-defined start condition:

---
name: analyst-stage
description: Analyzes research handoff and prioritizes stories
initialPrompt: "Read the latest handoff file from ~/pipeline/runs/current-run/handoff_searcher_to_analyst.md and begin your analysis. Apply your standard filtering criteria."
---

Pattern 2: Scheduled Tasks

For agents designed to run on a schedule:

---
name: morning-briefing
description: Generates a morning status briefing
initialPrompt: "Generate this morning's status briefing. Check all monitored channels, summarize overnight activity, and flag anything requiring immediate attention."
---

Pattern 3: Tool-Specific Agents

For agents that perform a specific, repeatable operation:

---
name: cover-image-generator
description: Generates cover images for new articles
initialPrompt: "Check the queue file at ~/pipeline/cover-queue.md. For each listed article, generate a cover image using the article-cover skill. Mark each as done when complete."
---

Common Mistakes

Don’t confuse initialPrompt with the system prompt. The system prompt (the body of your .md file) defines who the agent is. initialPrompt defines what the agent does first. Both are applied.

Keep initialPrompt task-focused, not instructional. Behavioral instructions belong in the system prompt. initialPrompt should be a concrete action — “do X” not “you should always do X.”

Test initialPrompt values before deploying. Because the prompt auto-submits, a poorly written initialPrompt will cause your agent to take the wrong action immediately. Test by running the agent manually with that exact prompt first.

Avoid dynamic values in initialPrompt. The frontmatter is static — you can’t inject the current date or run ID into initialPrompt directly. For dynamic values, pass them via the task description from your orchestrator instead.

Verify It’s Working

After invoking your agent, the first message in the conversation should be the initialPrompt text, followed immediately by the agent’s response. If you see a blank waiting state instead, check your Claude Code version and verify the field name is exactly initialPrompt (camelCase, no spaces).

Sources:

  1. Claude Code Sub-Agents Docs — initialPrompt field
  2. Claude Code Releases v2.1.9x

Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260405-0800

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