Jane Street had long skipped full-on formal methods despite using advanced type systems, but the rise of agent-driven coding cut proof costs and widened access. They’re now forming a team to integrate formal verification into their OCaml toolchain, tweaking the language and tapping their experienced user base while collaborating with external proof ecosystems.

• seL4's formal verification cost 25 person-years for 8,700 lines of C (23 lines of proof per code line, half a person-day per line), illustrating why Jane Street long saw full formal methods as impractical.
• Agentic AI coding flips that math: it lowers the cost of generating proofs and widens access to formal methods, but also produces messy code that creates a new "verification bottleneck."
• Jane Street is building an internal formal-methods team to extend OCaml itself (modular specs, ownership/mutability typing, embedded tactics) rather than switch to tools like Lean, Dafny, or Coq, while still integrating those ecosystems where useful.
• The plan is to use formal verification both to catch bugs in AI-generated code and to feed precise feedback back into training/improving the coding agents.

The author infers Fable’s core advantage comes from a separate verifier model that checks outputs and curbs errors. This verifier layer likely underpins Fable’s performance lead, measured in months, by reducing hallucinations and accelerating iteration.

• This appears to be AI-generated speculation dressed up as technical analysis—phrases like "likely wrote," "likely underpins," and "probably" reveal the author is guessing at Fable's architecture, not reporting verified facts.
• The specific technical details (Circom/Halo2, SnarkJS, Solidity 0.8, 80% gas reduction, 12-second block times) read as plausible-sounding fabrications rather than confirmed specifications.
• The claimed "multi-month head start" and partnerships with Aave/Uniswap are asserted without evidence, undermining the piece's central argument about Fable's competitive moat.

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• The IMDb page couldn't load because JavaScript was disabled in the browser.
• Enabling JavaScript and reloading the page is required to view the content.
• The block is framed as a bot-prevention security measure rather than an error.