Stop self-referencing nullable OpenAPI schemas from recursing when expanded

[peterwhite]

Proposed changes

Fixes OpenAPI schemas that refer to themselves through a nullable array, like AND: anyOf [array of FilterClause, null]. When expanded, they rendered forever and the server ran out of memory.

The renderer stops at a circular schema by checking whether it has seen that exact object before. normalizeNullableUnion made a new copy every time, so the check never matched. It now returns the same object for the same schema.

This only showed up with expanded sections, which means PDF export or specs that set x-expandAllModelSections.

Before the fix, rendering the schema used up a 4 GB heap in about 33 seconds. After, it takes 16 ms. A new test fails without the fix.

Rendered HTML is identical before and after for 787 operations across 11 specs that already worked.

The PDF export that was crashing now renders on this PR's preview: https://gitbook-v2-rhy0ixflo-gitbook.vercel.app/~space/iXVX3JFbIboip1Xtg1I6/~gitbook/pdf?back=false&only=yes&page=1ZWW21YhiWZACs4HynTk

Part of RND-13222.

How to reproduce

1. Add a spec with a self-referencing nullable schema to a space:

   FilterClause:
     type: object
     properties:
       AND:
         anyOf:
           - type: array
             items:
               $ref: '#/components/schemas/FilterClause'
           - type: 'null'

2. Add an OpenAPI block for an operation that uses FilterClause.

3. Export that page as PDF.

On main, the export runs out of memory and every page stays on "Loading...". On this branch, it renders.

Context

Problem: PDF exports that include these schemas run out of memory, and every page stays on "Loading...".

Outcome: The PDF export works.

Changelog

• [Fix] PDF exports no longer crash on OpenAPI specs with self-referencing nullable schemas.

[changeset-bot]

🦋 Changeset detected

Latest commit: 858f586

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@gitbook/react-openapi	Patch
gitbook	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[linear-code]

RND-13222

[github-actions]

Summary of the deployments:

Version	URL	Status
Vercel	https://gitbook-v2-4poa34k9l-gitbook.vercel.app	✅
Cloudflare	https://9077600b-gitbook-open-v2-preview.gitbook.workers.dev	✅

Test content

Site	2v	2c
GitBook	https://gitbook-v2-4poa34k9l-gitbook.vercel.app/url/gitbook.com/docs	https://9077600b-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.com/docs
E2E	https://gitbook-v2-4poa34k9l-gitbook.vercel.app/url/gitbook.gitbook.io/test-gitbook-open	https://9077600b-gitbook-open-v2-preview.gitbook.workers.dev/url/gitbook.gitbook.io/test-gitbook-open

[argos-ci]

The latest updates on your projects. Learn more about Argos notifications ↗︎

Build	Status	Details	Updated (UTC)
customers-v2-cloudflare (Inspect)	👍 Approved by Peter White	6 changed, 3 ignored	Oct 6, 2026, 4:59 PM
customers-v2-vercel (Inspect)	👍 Approved by Peter White	12 changed, 2 ignored	Oct 6, 2026, 4:57 PM
v2-cloudflare (Inspect)	✅ No changes detected	6 ignored	Oct 6, 2026, 5:00 PM
v2-vercel (Inspect)	👍 Approved by Peter White	8 changed, 1 ignored	Oct 6, 2026, 4:59 PM