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Subagents: How Specialized Agents Work (And What’s Official)

Subagents are isolated specialists with scoped tools and separate context.

“Subagents” sounds like marketing until you look at the underlying constraint it addresses.

From first principles, a single agent conversation has two problems:

  1. Context contamination: lots of intermediate notes and searches pollute the main thread.
  2. Tool risk: a general agent with broad permissions can do the wrong thing.

Subagents solve both by creating specialists with separate context and restricted tool access.

What Subagents Are (Official Anthropic Definition)

Anthropic’s Claude Code documentation explicitly supports “custom AI subagents” stored as Markdown files with YAML frontmatter:

Anthropic’s Agent SDK also documents subagents and emphasizes:

The Core Pattern

Think of a subagent as a constrained worker:

  • The main agent holds the plan and integrates results.
  • A research subagent can scan files and summarize without editing.
  • A code-review subagent can read diffs and flag risk without changing code.
  • A test-runner subagent can run approved commands and return logs.

The system benefit is composability: you can build a workflow out of small, reliable parts.

Why Separation of Context Matters

If a research pass dumps 30 files worth of notes into the main context, you get:

  • slower responses
  • higher cost
  • worse reasoning (too much irrelevant text)

Anthropic calls out the value directly: a research subagent can explore “without cluttering the main conversation” and return only relevant findings.
https://docs.claude.com/en/docs/claude-code/sdk/subagents

Why Tool Scoping Matters

Tool scoping turns “trust” into configuration.

Anthropic gives examples like a doc-reviewer subagent that only has read tools so it “can analyze but never accidentally modify” docs.
https://docs.claude.com/en/docs/claude-code/sdk/subagents

This is a concrete safety move: least privilege by construction.

Are Subagents Universal Across All Agents?

Many agent frameworks support “multi-agent” patterns, but the implementation details differ.

What we can say officially (and precisely) is:

Other tools may have equivalents (workers, copilots, parallel tasks), but “subagent” isn’t a single standardized mechanism across every vendor today.

How This Applies to OutcomeDev

OutcomeDev already operationalizes the same first-principles constraints:

  • tasks run in isolated sandboxes
  • tools are attached explicitly via connectors (MCP servers)
  • execution is verified by commands and logs

Subagents are a natural extension of that philosophy: split “do work” into smaller specialists and keep the main task focused on plan + integration.

Sources

Subagents: How Specialized Agents Work (And What’s Official) - OutcomeDev Blog