parallel-exploration

Parallel Exploration (Scout Fan-Out)

Overview

When you need to answer "where/how does X work?" across multiple domains (codebase, tests, docs, OSS), investigating sequentially wastes time. Each investigation is independent and can happen in parallel.

Core principle: Decompose into independent sub-questions, invoke one scout agent per sub-question, and synthesize the results together.

Safe in Planning mode: This is read-only exploration. It is OK to use during exploratory research even when there is no feature, no plan, and no approved tasks.

This skill is for read-only research. For parallel implementation work, refer to the skill at ../dispatching-parallel-agents/SKILL.md and invoke @forager directly for each runnable task.

When to Use

Default to this skill when: Use when:

• Investigation spans multiple domains (code + tests + docs)
• User asks 2+ questions across different domains (e.g., code + tests, code + docs/OSS, code + config/runtime)
• Questions are independent (answer to A doesn't affect B)
• User asks 3+ independent questions (often as a numbered list or separate bullets)
• No edits needed (read-only exploration)
• User asks for an exploration that likely spans multiple files/packages
• The work is read-only and the questions can be investigated independently

Only skip this skill when:

• Investigation requires shared state or context between questions
• It's a single focused question that is genuinely answerable with one quick grep + one file read
• Questions are dependent (answer A materially changes what to ask for B)
• Work involves file edits (use Hive tasks / Forager instead)

Important: Do not treat "this is exploratory" as a reason to avoid delegation. This skill is specifically for exploratory research when fan-out makes it faster and cleaner.

Tool-Aware Research

Load this skill before any multi-domain, read-only investigation that benefits from Scout fan-out.

• When the answer depends on rendered UI, browser state, console output, or network activity, use browser as one of the read-only slices.
• When external docs, APIs, or third-party implementations matter, use web or io.github.upstash/context7/* for the docs/OSS slice.
• Use todo only when you need to track multiple questions and evidence coverage during synthesis.
• Use vscode/memory only for findings the parent agent or a later turn will need after synthesis.

The Pattern

1. Decompose Into Independent Questions

Split your investigation into 2-4 independent sub-questions. Good decomposition:

Domain	Question Example
Codebase	"Where is X implemented? What files define it?"
Tests	"How is X tested? What test patterns exist?"
Docs/OSS	"How do other projects implement X? What's the recommended pattern?"
Config	"How is X configured? What environment variables affect it?"

Bad decomposition (dependent questions):

• "What is X?" then "How is X used?" (second depends on first)
• "Find the bug" then "Fix the bug" (not read-only)

2. Invoke Scout Agents in Parallel

Start all independent scout requests before waiting on any result.

Invoke the @scout agent via the agent tool for question 1.
Invoke the @scout agent via the agent tool for question 2.
Invoke the @scout agent via the agent tool for question 3.

Key points:

• Invoke the @scout agent via the agent tool for read-only exploration
• Give each invocation a clear, focused scope
• Make prompts specific about what evidence to return

3. Continue Working (Optional)

While tasks run, you can:

• Work on other aspects of the problem
• Prepare synthesis structure
• Start drafting based on what you already know

Each scout result returns to the parent chat when it completes.

4. Collect Results

When each task completes, its result is returned directly. Collect the outputs from each task and proceed to synthesis.

5. Synthesize Findings

Combine results from all tasks:

• Cross-reference findings (file X mentioned by tasks A and B)
• Identify gaps (task C found nothing, need different approach)
• Build coherent answer from parallel evidence

6. Cleanup (If Needed)

No manual cancellation is required for these agent invocations.

Prompt Templates

Codebase Slice

Investigate [TOPIC] in the codebase:
- Where is [X] defined/implemented?
- What files contain [X]?
- How does [X] interact with [Y]?

Return:
- File paths with line numbers
- Brief code snippets as evidence
- Key patterns observed

Tests Slice

Investigate how [TOPIC] is tested:
- What test files cover [X]?
- What testing patterns are used?
- What edge cases are tested?

Return:
- Test file paths
- Example test patterns
- Coverage gaps if obvious

Docs/OSS Slice

Research [TOPIC] in external sources:
- How do other projects implement [X]?
- What does the official documentation say?
- What are common patterns/anti-patterns?

Return:
- Links to relevant docs/repos
- Key recommendations
- Patterns that apply to our codebase

Real Example

Investigation: "How does the API routing system work?"

Decomposition:

1. Implementation: Where are API routes defined?
2. Routing: How does route registration work?
3. Notifications: How are errors surfaced to the caller?

Fan-out:

Invoke the @scout agent via the agent tool to find API route implementation.
Invoke the @scout agent via the agent tool to analyze concurrency.
Invoke the @scout agent via the agent tool to find the notification mechanism.

Results:

• Task 1: Found background-tools.ts (tool definition), index.ts (registration)
• Task 2: Found manager.ts with concurrency=3 default, queue-based scheduling
• Task 3: Found session.prompt() call in manager for parent notification

Synthesis: Complete picture of background task lifecycle in ~1/3 the time of sequential investigation.

Common Mistakes

Spawning sequentially (defeats the purpose):

Bad: invoke one scout agent, wait, then decide whether to invoke the next.

Good: issue all independent scout invocations in the same response.

Too many tasks (diminishing returns):

• 2-4 tasks: Good parallelization
• 5+ tasks: Overhead exceeds benefit, harder to synthesize

Dependent questions:

• Don't spawn task B if it needs task A's answer
• Either make them independent or run sequentially

Using for edits:

• Scout is read-only; use Forager for implementation
• This skill is for exploration, not execution

Key Benefits

1. Speed - 3 investigations in time of 1
2. Focus - Each Scout has narrow scope
3. Independence - No interference between tasks
4. Flexibility - Cancel unneeded tasks, add new ones

Verification

After using this pattern, verify:

• All tasks spawned before collecting any results (true fan-out)
• Verified agent-tool fan-out pattern used for parallel exploration
• Synthesized findings into coherent answer