Show HN: Specification First Agentic Development Plugin and Prove A developer released a Show HN plugin called Spec-First for agentic development, built around 9 skills and a single commit gate that runs four commands — create-spec, review-spec, apply-spec and deliver-spec — to write a spec, check it against the code, build it in its own worktree and open a verified pull request. The plugin, which works with Claude Code, Codex, Cursor and Copilot, assigns one branch and worktree per spec with offline-minted ids so parallel agents never collide, and stores state in context.yaml so work resumes after a restart. The author says the workflow is how the Agent Smith project is built daily across more than a thousand specs, with each non-obvious choice logged in decisions/ alongside the code. We'd like to use Google Analytics to see how many people visit and which pages they read. It sets cookies and sends data to Google. Nothing loads unless you say yes, and you can change your mind under Privacy settings at the bottom of every page. Vibe coding is dead. Talk it through, the rest is guided. Describe the feature in your own words. Four commands write the spec, check it against your code, build it in its own worktree and deliver it through your checks. Run several side by side and get back verified pull requests. You talk, it listensYou describe the app in your own words. Before asking anything, the agent reads your memory and the repository, so it only asks what neither can answer. The spec comes firstcreate-spec writes goal, facts with file and line, steps and done criteria, on a fresh branch in its own worktree. No code yet. A second pair of eyesA script checks that every cited file and line exists. Then a new agent with no chat history attacks the spec against the code, and its cuts are applied before anything is built. Built by the specapply-spec works through the steps, writes the tests the spec names, and logs every choice that wasn't obvious in decisions/. Only green landsThe commit goes through the gate: build and tests have to pass. Then the branch is pushed and the pull request opens with the spec inside. The rows with a dot are what the skills do on their own: reading, writing, checking, building. You type the lines in boxes. 9 skills1 commit gatea worktree per specids minted offline, safe in parallelClaude Code · Codex · Cursor · Copilot §1 What changes when agents work from specs This is how Agent Smith is built every day, across more than a thousand specs. Verified A fresh reviewer checks the spec against the code before the build. A gate runs your checks before the commit. Parallel One branch and worktree per spec. Ids come from the clock, so two agents never take the same one. Uninterrupted A reviewed spec has already answered the open questions, so the agent builds to its done criteria instead of coming back to ask. Structured One spec, one branch, one commit. A pull request carries one spec or a whole series, and every change has the same shape. Resumable State lives in context.yaml. Restart the machine or the agent and the work picks up where it stopped. Explained, as a side effect Each choice is logged with what it beat and why, so the reasoning stays next to the code. §2 A whole series, side by side Cut a bigger change into a series of specs. /spec-first:deliver-series reviews all of them, builds the groups that share no file at the same time, verifies the merged tree and opens one pull request. 3 worktrees building in parallel · every spec commit through the gate PR 42 An example run of /spec-first:deliver-series. Specs that share no file are built at the same time; specs that depend on each other share a group. §3 One spec, from idea to pull request Four skills take a piece of work through its own branch and worktree. Each one leaves a file behind for the next step and for whoever reads the history later. create-spec Goal, steps, facts with file and line, what done means. No code yet. specs/planned/{id}.yaml review-spec Every citation resolved, then a reviewer who never saw the chat attacks it. BUILD · CUTS · REFUSE apply-spec Contracts, code, wiring, tests, following the project's own rules. decisions/{id}.yaml deliver-spec One commit through the gate, pushed, pull request opened. feat: … {id} The recordgrows with every spec, read before every step specs/ Every spec, from planned to done, with its facts and done criteria. decisions/ What each spec chose, what it chose over, and why. memory/ What you told the agent once, so you don't say it twice. /spec-first:bootstrap-project writes the contexts once from your code: stack, rules and the checks a commit must pass. After that, each spec adds one line of state. §4 A spec is reviewed before anyone builds it A REFUSE costs you one spec. Without the review, the same mistake would have cost you the branch. Spec2026-10-27-8a3f Applies toserver Branchspec/8a3f Goal Ticket providers so pipelines can pull work from GitHub and Jira. Facts, read in the code Pipelines take work only from the CLI todayProgram.cs:40-58 Config already carries a tracker sectionAppConfig.cs:12-19 Decision Adapter over repository: read-mostly data, no unit of work needed. Done when GitHub provider returns tickets end to end Jira provider behind the same interface verify: stages green REVIEWED · BUILDfresh reviewer · 27 OCT review-spec · 2026-10-27-8a3f2 cuts ✓ src/Host/Program.cs:40-58 resolves ✓ src/Config/AppConfig.cs:12-19 resolves evidence resolves: 1 spec BUILD WITH CUTSthe spec holds once two steps change CUT 1 Step jira needs a second auth mode the config can't hold yet. AppConfig.cs:15 Move it to its own spec. CUT 2 Paging is missing: GitHub returns 30 issues per page. GitHubClient.cs:88 Add a done criterion. Every citation is checked A script opens each file and line the spec cites. A claim nobody checked in the code has to be listed as an assumption. The reviewer starts fresh A new agent with no conversation history reads the code as it is, not as the spec says it is. One verdict, with cuts named BUILD, BUILD WITH CUTS or REFUSE, and every finding names a file and a line. §5 The reasoning comes along for free Nobody has to write documentation afterwards. While it builds, the agent logs each choice that wasn't obvious: what it chose, what it chose over, and why. One file per spec, next to the code. decisions/2026-10-27-8a3f.yaml spec: 2026-10-27-8a3f decisions: - category: TradeOff chose: "Raw HttpClient for the GitHub API" over: "Octokit" reason: "Three megabytes of dependencies for four calls." - category: Architecture chose: "One ITicketProvider per tracker" over: "A generic REST mapper" reason: "Each tracker pages and authenticates differently; the mapper would leak it." No wiki to keep alive cat decisions/ .yaml is the project's reasoning, spec by spec, in the same history as the code it explains. Memory for what git can't tell How the operator wants things done, a constraint outside the repo, a pointer elsewhere. One fact per file, one line in an index. Back in thirty seconds Restart the machine, restart the agent, open context.yaml. It knows what is done, what is active and what comes next. §6 Nothing lands past a red stage The plugin's commit gate runs every verify stage your contexts declare when a commit names its spec. All green, it commits. The first red stage blocks it, and its output goes back to the agent. the commit git commit -m "feat: ticket providers 2026-10-27-8a3f " The id in parentheses triggers it. -F