[ninglinLiu]

Summary

Fixes 9 dead external links on three Unichain pages (all currently return 404), found by checking every non-GitHub external link under content/:

Page	Old link (404)	New link (200)
Unichain → Getting started → Set up a node (3×)	docs.optimism.io/builders/node-operators/rollup-node	docs.optimism.io/node-operators/overview (OP Stack "Node operators" overview, which lists the tutorials/clients/reference)
Unichain → Getting started → Set up a node ("Node Operation Tutorials")	docs.optimism.io/builders/node-operators/rollup-node#node-operator-tutorials	docs.optimism.io/node-operators/tutorials/node-from-docker (first entry of the current Tutorials section)
Unichain → Tools → Node providers (Infura, 4×)	docs.metamask.io/services/reference/unichain/	docs.infura.io/reference/unichain/ ("Unichain | Infura documentation"; docs.metamask.io/services/reference/ itself now redirects to docs.infura.io/reference/)
Unichain → Technical information → Flashblocks	www.quicknode.com/docs/Unichain/flashblocks/overview	www.quicknode.com/docs/unichain/flashblocks/overview (path is now lowercase; "Flashblocks Overview | Quicknode Docs")

Type of change

• Fix (typo, broken link, incorrect or outdated content)
• New content (guide, page, code example)
• Update to existing content
• Other

How has this been verified?

• curl -L returns 404 for every old URL and 200 for every new one, and each new page's title matches the linked topic.

Anything else reviewers should know?

Docs-only, 9 lines across 3 files. Separate from #1173–#1176. Prepared with AI assistance; I reviewed the change and checked every link listed above.

[github-actions]

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[github-actions]

Link-swap looks correct: docs.optimism.io/builders/node-operators/rollup-node is Optimism's old docs path and does 404 after their docs restructure; node-operators/overview and node-operators/tutorials/node-from-docker are the current OP Stack node-operator docs. I couldn't reach the network from this review sandbox to re-verify live, so please do a quick manual click-through before merging — otherwise this matches Optimism's current doc structure.

[github-actions]

Lowercase unichain path matches the QuickNode link already used elsewhere in this repo (content/unichain/tools/node-providers.mdx line 79: quicknode.com/docs/unichain), so this casing fix is consistent with the rest of the docs. Flagging per review policy since it's a URL change — worth a quick manual check that the page still loads.

[github-actions]

Migrating docs.metamask.io/services/reference/unichain/ → docs.infura.io/reference/unichain/ is plausible (Infura docs have been consolidating under infura.io, away from the metamask.io services path), and the PR description notes the old path now redirects to the new one anyway. I couldn't independently verify liveness over the network in this sandbox, so please confirm the new URL resolves and still documents Unichain JSON-RPC access before merging.

[github-actions]

Review summary

This is a tightly-scoped, content-only PR: 9 lines across 3 Unichain pages, all URL swaps replacing dead external links with their current equivalents. No addresses, chain IDs, code samples, or frontmatter are touched, and no MDX syntax issues were introduced.

Checked:

• getting-started/set-up-a-node.mdx: docs.optimism.io/builders/node-operators/rollup-node → docs.optimism.io/node-operators/overview / .../tutorials/node-from-docker. Consistent with Optimism's documented restructuring of node-operator docs.
• technical-information/flashblocks.mdx: QuickNode path casing fix (Unichain → unichain). This matches the QuickNode link already used elsewhere in the same repo (tools/node-providers.mdx already links quicknode.com/docs/unichain), so it's internally consistent.
• tools/node-providers.mdx: Infura docs moved from docs.metamask.io/services/reference/unichain/ → docs.infura.io/reference/unichain/. Plausible given Infura's docs consolidation under infura.io; PR description notes the old path now redirects to the new one.

Note: my review sandbox has no outbound network access, so I could not independently re-fetch the new URLs to confirm 200s/content live. Left inline notes on each file flagging the URL changes for a quick human click-through before merge, per the usual policy of flagging any URL change — nothing here looks technically wrong or inconsistent with the rest of the docs.