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## 2.80.0

**`(feat):`** Add opt-in `allow-user-agent-app-info` config. When enabled, generated clients expose an
optional `AppInfo` client option (`Name`, `Version?`, `Comment?`) whose sanitized product
token is appended to whatever `User-Agent` the SDK would otherwise send
(`{sdk}/{version} ... {product}/{product-version} ({comment})`), following RFC 9110.
Disabled by default, so existing generated output is byte-identical, and it composes with
`include-platform-headers`, the configured `user-agent` template value, and the
`user-agent-name-from-package` fallback. Caller-supplied values are trimmed and encoded
(name/version percent-encoded to RFC 7230 `tchar`; comment delimiters `(`, `)`, `\` and
control characters incl. CR/LF escaped), so untrusted values cannot inject header content.
Still overridable by an explicit `User-Agent` header and suppressed by `omit-fern-headers`.
Works in both unified and non-unified client-options modes; generated code compiles for
`net462`, `net8.0`, and `netstandard2.0`.