MLA 024 Agentic Software Engineering: Specs, Verification, and the Review Loop

How working engineers ship with coding agents: issues an agent can verify, plan mode before code, a verification loop with a browser in it, agent review of agent code, worktrees and CI, cost discipline, and where agents still fail. Links Try a walking desk - stay healthy & sharp while you learn & code More OCDevel shows - this one has siblings, each on its own subject and produced the same way

Third and last episode of the vibe-coding sequence. Vibe Coding in 2026 picked an agent; Inside a Coding Agent explained the mechanics. This one is the practice: how working engineers ship real software with Claude Code, Codex, and Antigravity without shipping garbage. Specs, verification loops, agent review, parallel worktrees, headless CI, cost discipline, and the failure modes. From vibe coding to agentic engineering Andrej Karpathy coined vibe coding in early 2025 and, a year later, proposed "agentic engineering" for professional work. His older idea of jagged intelligence (models clear hard problems and trip on trivial ones, unpredictably) is why the job is judgment rather than button-pressing. The frame for the episode: when implementation is cheap, the value moves to the two ends of the pipeline, specification (saying exactly what should be true) and verification (proving it). Vibe coding stays fine for throwaways; the rest applies to codebases with users. Specs: issues as prompts, plan mode in Claude Code, Codex, and Antigravity The prompt is a spec whether you meant it or not. The unit of work is a tracker issue with four parts: what's wrong, where to look, acceptance criteria a machine or a five-second human check can verify, and an explicit out-of-scope fence. Every serious agent has a read-only planning phase: Claude Code's plan mode (Shift+Tab or /plan), Codex's plan mode on the same keystroke with its own plan-mode reasoning effort, and Antigravity's implementation plan artifact. Judge a plan on three things: the files it names, the verification step it commits to, and whether it stays inside the fence. Heavier spec tooling (GitHub spec-kit, Kiro specs) formalizes requirements, design, and tasks. Anthropic's best practices teach a lighter interview-then-spec-file pattern and say to skip planning when you could describe the diff in one sentence; OpenAI's Codex best practices frame a task as goal, context, constraints, and "done when." Verification loops: one-command checks, test-first, Playwright MCP and browser agents An agent without feedback guesses; an agent with a runnable check searches. Make typecheck, lint, tests, and build fast and runnable from one command, because that command is what the agent lives inside. Test-first changes meaning here: it used to be design pressure, and now it gives the agent a fixed target. Anthropic's guidance is that without a success criterion the developer is the only feedback loop (building verification loops). Then add a browser. Playwright MCP drives a real one through accessibility snapshots with stable element refs, no vision model needed; Claude in Chrome is the screenshot route Anthropic names for UI verification; Antigravity's browser agent starts the dev server and clicks through on its own, ending in a walkthrough with verification evidence. The principle: every acceptance criterion maps to a check the agent can run. If one doesn't, either the criterion is vague or the project is missing a kind of check. The review loop: agent PRs, Claude Code and Codex review, human gate Five vendor-agnostic stages: trigger, implement, review, fix, gate. Agent review of agent code works because the reviewer has fresh context, so never reuse the implementing session as its own reviewer. Ask for correctness and quality separately and set a confidence bar so the reviewer reports only what it's sure of. Anthropic's code-review plugin runs four parallel reviewers with 0-100 confidence scores and drops findings under 80; a cloud tier (Ultrareview) reproduces each finding before reportin