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Plumb is a deterministic verification layer for coding agents. It reads the repository—not just the agent's answer—to discover the checks and instructions it declares, determines what can actually run, and independently verifies the work. No model calls. No repository upload. It can PASS, FAIL, BLOCK, or preserve uncertainty instead of pretending it knows. Built for Claude Code, Codex, and other coding agents.
I'm Nathan, the builder of Plumb.
Plumb started with a simple failure: a coding agent told me it was done, but it hadn't actually established that.
My first instinct was to add more instructions. Then I realized I was assuming that would solve the problem, so I tested the assumption instead.
That turned into months of work across real repositories, held-out evaluations, third-party research data, and quite a few experiments that failed. Some features were killed entirely because the evidence didn't support them.
The result is Plumb: a deterministic layer that reads what a repository itself declares, finds the verification it can support, and checks the work independently of the coding agent.
Plumb doesn't use another model to grade the first model. It can also refuse to claim success when the evidence isn't there.
It runs locally, makes no model calls, doesn't upload your repository, and works alongside coding agents like Claude Code and Codex.
Install it with:
curl -fsSL https://plumbing.sh/install | sh
I built Plumb around a simple idea:
Agents can guess. Evidence shouldn't.
This is the hardest I've worked on a software project, and at this point the most useful testing can't come from me anymore. It needs to come from repositories and developers I haven't seen.
If you use coding agents, I'd love for you to try Plumb and tell me where it gets things wrong.
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About Plumb on Product Hunt
“Your coding agent says it's done. Plumb checks.”
Plumb was submitted on Product Hunt and earned 2 upvotes and 1 comments, placing #156 on the daily leaderboard. Plumb is a deterministic verification layer for coding agents. It reads the repository—not just the agent's answer—to discover the checks and instructions it declares, determines what can actually run, and independently verifies the work. No model calls. No repository upload. It can PASS, FAIL, BLOCK, or preserve uncertainty instead of pretending it knows. Built for Claude Code, Codex, and other coding agents.
Plumb was featured in Productivity (659.4k followers), Developer Tools (518.3k followers) and Artificial Intelligence (477.2k followers) on Product Hunt. Together, these topics include over 354.6k products, making this a competitive space to launch in.
Who hunted Plumb?
Plumb was hunted by Nathan Haring. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
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Nathan Haring