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Clarify case-insensitive env carrier lookup #5180

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Merged
pellared merged 1 commit into from
Jun 29, 2026
Merged

Clarify case-insensitive env carrier lookup #5180

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7 changes: 7 additions & 0 deletions specification/context/env-carriers.md
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Expand Up @@ -98,6 +98,13 @@ environment-specific `Get` operation MUST normalize the requested key to
read a non-normalized environment variable named `x-b3-traceid`, even though
that name normalizes to `X_B3_TRACEID`.

> [!NOTE]
> On platforms with case-insensitive environment variable lookup, such as
> Windows, the platform lookup performed by `Get` may match an environment
> variable whose name differs from the normalized key only by case. For example,
> if a Windows process environment contains `traceparent`, reading the
> normalized key `TRACEPARENT` may return the value of `traceparent`.

> [!NOTE]
> This normalization is consistent with the environment variable naming rules
> defined in [POSIX.1-2024](https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap08.html).
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