Fix issue where MCP POST requests with expired tokens returns 307 instead of 401

[spastorelli]

Generally the MCP client should request a fresh token via refresh_token grant before token expiration but seen some cases where this doesn't happen.

[linear-code]

RND-10559

[changeset-bot]

⚠️ No Changeset found

Latest commit: cb4842d

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[github-actions]

Summary of the deployments:

Version	URL	Status
Vercel	https://gitbook-v2-p8buh9pux-gitbook.vercel.app	✅
Cloudflare	https://390153b4-gitbook-open-v2-preview.gitbook.workers.dev	✅

Test content

Site	2v	2c
GitBook	https://gitbook-v2-p8buh9pux-gitbook.vercel.app/url/gitbook.com/docs	https://390153b4-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.com/docs
E2E	https://gitbook-v2-p8buh9pux-gitbook.vercel.app/url/gitbook.gitbook.io/test-gitbook-open	https://390153b4-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.gitbook.io/test-gitbook-open

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Build	Status	Details	Updated (UTC)
customers-v2-cloudflare (Inspect)	👍 Changes approved	12 changed	May 28, 2026, 2:09 PM
customers-v2-vercel (Inspect)	👍 Changes approved	12 changed	May 28, 2026, 2:09 PM
v2-cloudflare (Inspect)	👍 Changes approved	21 changed	May 28, 2026, 2:33 PM
v2-vercel (Inspect)	👍 Changes approved	5 changed	May 28, 2026, 2:14 PM