Elixir 1.20.4

Remember when Elixir was the niche language for telecom-style concurrency, running on the Erlang VM but rarely seen on a resume? That era is over. On August 28, 2026, Elixir shipped v1.20.4, a small patch that sits on top of a much larger story.

The real headline is gradual typing. What began as a research idea has, over recent releases, become the default experience. Elixir 1.20, released on June 3, 2026, taught the compiler to infer types across clauses, reason inside guards, and type check whole function bodies. Patch releases since then have steadily refined that system. v1.20.4 continues the polish.

Security Patching

Like every good historian knows, the boring patches carry the security fixes. v1.20.4 addresses advisory CVE-2026-75758 (GHSA-jf5q-v438-665c), so this is an upgrade you should take seriously.

What Changed

• Base: fix false positives in Base64 validation.
• Kernel: fix the inferred type of :erlang.split_binary/2 when given a bitstring.
• Kernel: further type checker refinements for edge cases.

The Trajectory

From 1.20.0 to 1.20.4, the team has hardened a release that requires Erlang/OTP 27 and plays nicely with OTP 29. The message is consistent: the type system works, the compiler stays fast, and security patches land on schedule.

Should You Upgrade?

Yes. A security fix plus type-checking corrections, with no framework-breaking API changes. Upgrade through asdf, mise, or your package manager and run your test suite.