Header types is the Important line in Axios 0.34.0

So Axios put v0.34.0 on the feed, dated September 13, 2026. We flagged it Important as a breaking change. The version tag is kind of the decoy. The line that matters opens under Breaking Changes: TypeScript now rejects header values that are Promises, functions, or objects with custom toString() methods. Resolve them or convert them before you assign. Scalar, array, and grouped headers still work.

Recency wants captureCallerStack and AbortSignal.reason preservation. Fine. Those are the names people screenshot. The partner-break line, to the best of my understanding, is the type reject. Your AE forwards 0.34.0. The customer who typed headers with a lazy Promise or a fancy object starts failing the TypeScript build overnight. That is the product change you track when you sell next to HTTP clients, not the cheerful diagnostics bullet.

There is a second Important line in the same note if you sell into proxy-heavy Node shops. NO_PROXY / no_proxy entries now support IPv4 and IPv6 CIDR ranges. Ranges that used to do nothing now actually bypass the proxy for matching IP destinations. Review the ranges when you upgrade. That is a routing behavior change dressed as a point release. Same release also hardens a few request-config paths against inherited properties. Real, and still secondary to the header types and CIDR bypass if a prospect asks what broke after they bumped.

I keep almost filing Axios under "HTTP client bump, ignore." Kind of the wrong habit when you sell next to API platforms or anyone whose SDK wraps axios. Tracking product change here means reading past the tag and asking which line changes a partner ticket. Let's say the talking point is not "0.34 shipped." It is TypeScript will reject those header shapes, then check whether your NO_PROXY CIDR ranges suddenly start bypassing. We pull it into a uniform entry shape at /sources/axios-releases. Same JSON as everything else. Recency still wants the diagnostics features. Recency is not the header type reject.