fix: bound docs build concurrency to avoid Vercel OOM

[tin-berri]

Production docs builds are being killed by out-of-memory events on Vercel's 8 GB builder after compilation, blocking publication of merged changes including #2006. The image optimizer currently opens a pipeline for every image at once, while Docusaurus renders up to 32 pages concurrently.

Limit image optimization to two files at a time and default static page rendering to four concurrent pages through a portable build entry point. Keep the existing compression settings and error recovery, allow DOCUSAURUS_SSR_CONCURRENCY to override the page limit, and log both limits during builds.

Validation: the new regression test fails on the original optimizer with 101 simultaneous pipelines and passes with the fix. PNG/JPEG optimization and invalid-image recovery also passed using real Sharp. The regression tests run in the existing docs CI workflow. All GitHub checks passed. The Vercel preview completed successfully on the same 4-core / 8 GB builder in 15 minutes, compressed all 3,026 images, and saved 284.2 MB. Production also completed successfully on the same 8 GB builder in 18 minutes. The live post returns 200 with the October 3 date, the RSS and archive both contain it, and the hero document, scripts, fonts, icons, and social image all return 200.

Failure evidence: https://vercel.com/clerkieai/litellm/4F9ykPhVuYx85mU1s5PmXzpmLCz8

Successful preview: https://vercel.com/clerkieai/litellm/3JpUeEfzXFM8fsAQaf51KyWzisr2

Production deployment: https://vercel.com/clerkieai/litellm/2sSoZ6TYpijmQ5Un8BNQjJxUZuBP

Live post: https://docs.litellm.ai/blog/internal-devin-two-days

[vercel]

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Project	Deployment	Actions	Updated
litellm	Ready	Preview	Oct 4, 2026 1:13am UTC