add_per_request_headers_timeout_auth_overrides.md

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Add per-request headers, timeout, and auth overrides to endpoint functions

All generated endpoint functions (sync_detailed, asyncio_detailed, sync, asyncio) now accept three optional keyword arguments forwarded directly to the underlying httpx request:

• headers: dict[str, str] | None = None — extra headers merged on top of any spec-defined headers for this request
• timeout: httpx.Timeout | None | Unset = UNSET — override the client-level timeout for this request; None disables the timeout
• auth: httpx.Auth | None | Unset = UNSET — override the client-level auth for this request; None disables auth

This allows per-request customisation without creating a new client instance, preserving the shared httpx connection pool. Using with_headers() / with_timeout() at runtime was previously the only option, but those methods mutate the original client's underlying httpx client as a side effect and cause the returned client to open a new connection pool on first use—making them unsafe for concurrent async code.

Note: client-level headers cannot be fully removed for a single request via this mechanism, only overridden with a different value.