教 mainagent 何时 / 如何把任务分发给 subagent 来控制主线程上下文预算，并判断哪些独立任务适合并行、如何回收和验证结果。当任务命中「读超过 5 个文件 / 包含搜索 / 输出超过 500 行 / 主线程已 30+ tool call / 用户说调研/分析/扫一遍/梳理」任一条时启动。触发词：分发任务、上下文预算、主线程上下文、要不要 dispatch、subagent 分发、长任务、调研、扫一遍、避免上下文爆炸、context budget、控制上下文、mainagent context、上下文要爆了。
Use before implementation when a request is ambiguous, has materially different solution paths, changes architecture or public behavior, or involves costly or irreversible decisions. Skip for small well-scoped fixes, mechanical edits, and execution of an already approved plan.
Use when code review feedback has been received and needs to be assessed, answered, or implemented. Verify each suggestion against the actual code and requirements before changing anything.
Use when diagnosing a bug, test or build failure, performance issue, or unexpected technical behavior. Gather evidence and confirm a root-cause hypothesis before implementing a fix.
Use immediately before claiming work is complete, fixed, correct, or passing, and before publishing changes. Requires fresh, claim-specific evidence and accurate reporting of what was and was not verified.