Overview
A reusable skill is a compact operating procedure. It stores a name, description, instructions, permitted tools, and the process for completing a recurring function. A specialized subagent can receive similar information, but it also starts with a separate context window and performs the work behind a clearer execution boundary.
This makes skills and subagents closely related. Both package task-specific knowledge and tool use.
The main difference is that a subagent usually gets a fresh context, while a skill often runs inside the current agent's context. A skill reduces context by compressing a procedure. A subagent reduces context by isolating the procedure in a new thread.
In the parent-researcher-QA pattern, a strong parent agent acts as orchestrator. It decides what needs to be done and delegates broad information collection to several research agents. The researchers return concise findings. The parent uses those findings to design or implement the solution. A fresh QA agent then inspects the result, reports defects or weaknesses, and sends feedback to the parent. The parent revises the work and repeats the QA loop until no material issues remain or a stop condition is reached.
In the developer-QA pattern, the system is even simpler. One capable agent performs the work. A newly spawned reviewer with no development history inspects the output. The developer receives the review, corrects the issues, and submits the result again.
The fresh QA context is important. The developer has seen the assumptions, compromises, and reasoning that produced the implementation. That history can bias its self-review. A separate reviewer sees the artifact rather than the development story and is therefore more likely to challenge what the builder accepted.
Sequential specialist pipelines use the same principle. Agent A completes one stage and hands a defined artifact to agent B, which performs a different stage, then passes its output to agent C.
Development, bug review, and testing are natural examples because building quickly and looking aggressively for faults reward different behaviors.