Dynamic Workflows in Opus 4.8: Build a Self-Verifying PR Reviewer

You stopped being the loop Most people use Opus 4.8 the way they used every model before it: open a chat, type a request, watch the cursor, correct it, repeat. That's a conversation. A dynamic workflow is something else entirely. The shift is this: you stop being the loop. Instead, an orchestrator — plain code you control — spawns subagents you design, fanning out work in parallel, running steps in sequence, judging and merging results, and reporting back when the whole thing is done. Opus 4.8 can drive hundreds of parallel subagents inside a single workflow, with effort control per node so cheap steps stay cheap and hard steps think harder. In this tutorial you'll learn the core patterns by building one concrete thing: a pull-request reviewer that fans out across correctness, security, and performance, then adversarially verifies every finding before it reaches you. // You design the shape. The orchestrator runs it. const found = await parallel ( DIMENSIONS . map ( d => () => agent ( d . prompt , { schema : FINDINGS }))) const deduped = dedupeByFileLine ( found . flatMap ( r => r . findings )) const verified = await parallel ( deduped . map ( f => () => agent ( refutePrompt ( f ), { schema : VERDICT }))) const real = verified . filter ( v => v . refuted === false ) By the end you'll know when to reach for parallel() versus pipeline() , how structured output schemas keep subagents composable, and where to set effort per node. The mental model: it's a graph, not a prompt Stop thinking "I send a prompt, I get a completion." Start thinking: an orchestrator runs a workflow graph, and each node is an agent call. The orchestrator is plain code. It decides what runs, in what order, and what to do with each result. Subagents are the leaf workers — each gets a focused prompt, a structured-output schema, and its own effort setting. The unit of work is no longer the prompt; it's the graph. Two primitives compose every graph, and the difference between them is entirely about ba