Run WordPress within Cloudflare Worker memory limits

[chubes4]

Summary

Run a full seeded WordPress 7.0.2 runtime inside Cloudflare Workers' fixed 128 MB isolate limit, with canonical Markdown/JSON revisions persisted in R2 and mutation coordination limited to a Durable Object lease/CAS protocol.

What changed

• Stream and filter the WordPress archive to the server files required by the runtime.
• Boot from a disposable installed WordPress SQLite seed rather than running wp_install() in the isolate.
• Bundle the constrained primary runtime from Add constrained primary runtime and explicit flush contract markdown-database-integration#126 at immutable commit 94b9f875ffb8402d5e8eb726893a12324e20f45c.
• Execute normal MDI driver SQL mutations in PHP-WASM and explicitly flush deterministic relative Markdown/JSON paths.
• Store content-addressed canonical objects and immutable revision manifests in R2; SQLite remains disposable and is never uploaded.
• Use the Durable Object only for persisted mutation leases, base-revision validation, and atomic current-pointer promotion.
• Preserve cold reconstruction and serialize concurrent mutations without running PHP-WASM inside the Durable Object.

Stack

1. Fix range-filtered remote ZIP decoding WordPress/wordpress-playground#4110 provides bounded workerd-compatible filtered Range decoding.
2. Add constrained primary runtime and explicit flush contract markdown-database-integration#126 provides the public constrained primary runtime and explicit flush contract.

Tracking issue: #1838.

How to test

1. Install dependencies from a fresh checkout with npm install.
2. Until Fix range-filtered remote ZIP decoding WordPress/wordpress-playground#4110 is released, install the @php-wasm/stream-compression artifact produced from that PR.
3. Run npm run generate:cloudflare-mdi-runtime-bundle; expect nine deterministic MDI runtime files from revision 94b9f875ffb8402d5e8eb726893a12324e20f45c.
4. Run npm run test:cloudflare-runtime; expect all Cloudflare runtime tests and TypeScript checks to pass.
5. Run npm run cloudflare:dry-run; expect Wrangler to package the Worker with the WORDPRESS_STATE Durable Object and WORDPRESS_STATE_BUCKET R2 bindings.
6. Run npm run cloudflare:local-gate; expect two HTTP 200 WordPress health envelopes.
7. In an authorized disposable Cloudflare account with the declared R2 bucket, deploy the committed branch and send sequential and concurrent POST /?phase=r2-mutate requests. Expect monotonic revision values, previousPostFound: true, deterministic canonicalChanges, and sqlitePersisted: false.

Verification

• npm run test:cloudflare-runtime passed: 5 tests.
• npm run cloudflare:dry-run passed. Wrangler reports a pre-existing duplicate test:php-browser-preview-only-session package-script warning.
• Extracted mutation PHP passed php -l.
• GitHub workflow-lint passed; contracts is pending.

Supplementary deployed proof

Disposable Worker commit a900ae51, version 5c9c2452-9cf8-478f-8318-81c61eaaccc1:

• Health returned WordPress 7.0.2 and PHP 8.5.8.
• The first upgraded cold mutation restored prior R2 state and advanced revision value 4 to 5.
• MDI flush reported post/cloudflare-r2-proof-5.md as created and _options/wp_codebox_mdi_revision.json as changed.
• Two concurrent requests serialized as values 6 and 7, each recovering the preceding post and promoting a distinct pointer.
• Final R2 pointer revision: b35e7137-71e0-4551-97fb-23bee79e76f8.
• Every response reported sqlitePersisted: false.

Worker: https://wp-codebox-cloudflare-runtime.chubes.workers.dev

Compatibility

This is an additive draft runtime package. Existing WP Codebox runtime behavior and extension APIs are unchanged. The Cloudflare path depends on unreleased upstream contracts in WordPress/wordpress-playground#4110 and Automattic/markdown-database-integration#126.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode and Homeboy
• Model: OpenAI GPT-5.6 Sol and openai/gpt-5.6-terra
• Used for: Memory-boundary investigation, upstream contract design, implementation, review, deterministic verification, and disposable Cloudflare proof in collaboration with Chris Huber.