ANTHROPIC_CUSTOM_HEADERS and CLAUDE_CODE_EXTRA

ANTHROPIC_CUSTOM_HEADERS and CLAUDE_CODE_EXTRA_BODY are now grouped together

Under the hood Internal Changes

JSON All of v2.1.319

Under the hoodTier: how much it should matter to you

1Useful: my rating, 1 to 5

1Signal: worth watching, 1 to 5

Environment VariablesArea: what it touches

Internal ChangesKind: in v2.1.319, 06 Nov 26

Internal ChangesSection of the release

Unclear What Claude Code does with the list, and whether it changes how these variables apply, is not stated.

What

An environment variable is a named value you set in your shell before starting a program. Claude Code now keeps a list holding two of them, so it can handle them together:

ANTHROPIC_CUSTOM_HEADERS, which adds your own headers to the requests Claude Code sends.
CLAUDE_CODE_EXTRA_BODY, which adds your own fields to the body of each request.

Why

Both variables let you change what Claude Code sends to the model provider, so they are sensitive. Grouping them suggests Claude Code now gives them special treatment.

Read from

Names in the bundleANTHROPIC_CUSTOM_HEADERSCLAUDE_CODE_EXTRA_BODY

How sure we are

Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.

The writer flagged doubtWhat Claude Code does with the list, and whether it changes how these variables apply, is not stated.

See this entry in the whole of v2.1.319 →

The build it came inv2.1.319

6 Nov 2026 · 480 entries, this one is #464.

Use it now39
You'll notice291
Nothing to try yet13
Under the hood137

Either side of it

v2.1.318Older

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Names in this entry

envANTHROPIC_CUSTOM_HEADERS
Custom headers to add to requests (Name: Value format, newline-separated for multiple headers). If a name or value contains a character an HTTP header can't carry, such as a curly quote or a zero-width space, the request fails with an error that identifies the pair by position. Requires Claude Code v2.1.227 or later. Invalid request header value lists the exact character set and where the check runs. A value that sets a credential, org or tenant, routing, or API-behavior header, such as Authorization or Host, counts as a setting that needs approval when server-managed settings deliver it. From project or local settings, such a value follows the rules for when env values apply
envCLAUDE_CODE_EXTRA_BODY
JSON object to merge into the top level of every API request body. Useful for passing provider-specific parameters that Claude Code doesn't expose directly. A value exported in your shell also applies to the background sessions you dispatch with claude agents or --bg. Before v2.1.206, background sessions ignored a shell-exported value and used whatever copy the background supervisor process inherited

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