[Candidate / unverified] Solution for 597221e8-2cb9-4e63-984f-8ee2165b457b: For ReadableStream or async-iterable upload bodies, pass duplex: 'half' in the f

## Support semantics This is a **candidate / unverified** Solution from the KFA Solution Factory Tier-2 gate. It is source-grounded research material, not an Outcome, and does **not** claim independent reproduction or confirmed field success. ## Cause undici Request constructor throws TypeError for GET/HEAD with body and throws when initBody is non-null, body source is null (stream), and init.duplex is missing. ## Steps 1. If the error mentions duplex, add duplex: 'half' alongside method/body when body is a stream. 2. Alternatively read the stream into a Buffer and pass as a non-stream body. 3. If the error mentions GET/HEAD body, remove the body or change method to POST/PUT per API spec. 4. Retry the request and confirm no synchronous TypeError before network I/O. ## Expected result Request constructor accepts the init; fetch proceeds to network layer without TypeError on validation. ## Misleading approaches - Assuming axios/node-fetch v2 GET-with-body behavior applies to undici fetch. - Adding duplex without changing GET+body combinations. ## Limitations - Only duplex value 'half' is supported in undici for this path. - Spec still forbids GET/HEAD bodies; duplex does not override that rule. ## Unknowns - Exact undici major version bundled with a given Node.js LTS release. ## Evidence claims - (documented_platform_behavior) undici fetch throws TypeError 'Request with GET/HEAD method cannot have body.' when init or input supplies a body for GET or HEAD. — https://raw.githubusercontent.com/nodejs/undici/main/lib/web/fetch/request.js - (documented_platform_behavior) Stream bodies without a fixed source require init.duplex or the constructor throws 'RequestInit: duplex option is required when sending a body.' — https://raw.githubusercontent.com/nodejs/undici/main/lib/web/fetch/request.js