{"slug": "tlaplusplus-a-faster-tla-model-checker-in-c11", "title": "TLAPlusPlus: A Faster TLA+ Model Checker in C11", "summary": "Developer soasme released TLAPlusPlus, a TLA+ model checker written in C11 as a single C file and one header file, built with Claude Code and validated against TLC as an oracle. Version 0.4.0 of TLAPlusPlus runs 4x to 20x faster than the official Java-based TLC, according to the developer, after v0.1.0 came in only slightly faster and v0.2.0 passed the Small Python TLA+ specs. Feedback from TLA+ core maintainer Markus Alexander Kuppe and TLA-RS author Fabrício Bracht shaped v0.6.1, the current release.", "body_md": "# TLAPlusPlus: A Faster TLA+ Model Checker in C11\n\nIn the past few days, I have been working on a fun project: [TLAPlusPlus](https://github.com/soasme/tlaplusplus).\n\nWhile running TLA+ specs for [Small Python](https://github.com/soasme/small-python/), one thing that really blocked me was the time it took to run them. I use a lot of TLA+ specs to model the C implementation, and the expensive run time kills me.\n\nI was never into Java. So I asked Claude Code to build one in C11. Just one C file and one header file. I asked it to produce a language specification first, then test262-style test specs, and then use TLC as the oracle. The outcome is amazing: it’s slightly faster than the official Java version. [v0.1.0](https://github.com/soasme/tlaplusplus/releases#release-v0.1.0)\n\nMaking it actually pass all the [Small Python TLA+ specs](https://github.com/soasme/small-python/tree/main/tests/tla) is a real-world testament. To make that happen, more bugs were fixed. [v0.2.0](https://github.com/soasme/tlaplusplus/releases#release-v0.2.0)\n\nI wasn’t satisfied. I wanted it faster. So after another overnight session, [v0.4.0](https://github.com/soasme/tlaplusplus/releases#release-v0.4.0) made it 4x-20x faster than TLC.\n\nI wanted to share it with the world, but I wasn’t confident it actually worked well. So I asked the agent to find more real-world examples, and in turn it fixed more bugs. [v0.5.0](https://github.com/soasme/tlaplusplus/releases#release-v0.5.0)\n\nI shared it with the Reddit community ([post](https://www.reddit.com/r/tlaplus/s/bqGusinwxy)) and got some good feedback from Markus Alexander Kuppe (core TLA+ maintainer) and Fabrício Bracht (author of TLA-RS). [v0.6.1](https://github.com/soasme/tlaplusplus/releases#release-v0.6.1) was made from that feedback while I was playing chess, Chinese chess, poker, and football with my family on Sunday.\n\nSo this is the short story of making software that actually solves my own pain and can benefit others.", "url": "https://wpnews.pro/news/tlaplusplus-a-faster-tla-model-checker-in-c11", "canonical_source": "https://julin.ai/2026/11/08/tlaplusplus/", "published_at": "2026-11-07 11:00:00+00:00", "updated_at": "2026-11-09 01:22:41.352435+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools", "ai-agents"], "entities": ["TLAPlusPlus", "TLA+", "TLC", "Claude Code", "Small Python", "Markus Alexander Kuppe", "Fabrício Bracht", "TLA-RS"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/tlaplusplus-a-faster-tla-model-checker-in-c11", "markdown": "https://wpnews.pro/news/tlaplusplus-a-faster-tla-model-checker-in-c11.md", "text": "https://wpnews.pro/news/tlaplusplus-a-faster-tla-model-checker-in-c11.txt", "jsonld": "https://wpnews.pro/news/tlaplusplus-a-faster-tla-model-checker-in-c11.jsonld"}}