Peter Wielander
fd621b1167
On a cold serverless instance the first replay parses the entire workflow bundle before it can reach the first step. The in-process vm.Script cache (#2471) only helps subsequent replays in the same process; the cold first one still pays a full parse, which grows ~30ms/MB and dominates time-to-first-step for large bundles. Producer (builders/next): for bundles over a size threshold, compile the bundle at build time and emit Script.createCachedData() as base64 in the generated flow route, passed via workflowEntrypoint's cachedData option. Skipped for small bundles (parse is ~1ms; the blob would just bloat the artifact) and via WORKFLOW_DISABLE_BUNDLE_CODE_CACHE. Consumer (core): getCachedWorkflowScript compiles with the cachedData so V8 skips parsing on the first compile. The blob is filename-independent so one build-time cache serves every per-workflow filename; V8 validates it and falls back to a full parse on any version/source mismatch, so a stale blob is never a correctness risk. Measured fresh-process parse: 2MB 34->4.8ms, 8MB 147->21ms (~7x). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Workflow SDK
Getting Started
The Workflow SDK lets you easily add durability, reliability, and observability to async JavaScript. Build apps and AI agents that can suspend, resume, and maintain state with ease.
Visit https://workflow-sdk.dev to view the full documentation.
Community
The Workflow SDK community can be found on GitHub Discussions, where you can ask questions, voice ideas, and share your projects with other people.
Contributing
Contributions to Workflow SDK are welcome and highly appreciated. Please use GitHub issues and discussions to collaborate with the team and wider community.
Author list
Workflow SDK was built by engineers at Vercel and the Open Source Community.
The initial core contributing engineers are:
- Adrian Lam (@adriandlam)
- Dillon Mulroy (@dmmulroy)
- Gal Schlezinger (@Schniz)
- JJ Kasper (@ijjk)
- Nathan Rajlich (@TooTallNate)
- Peter Wielander (@VaguelySerious)
- Pranay Prakash (@pranaygp)
The Workflow SDK logo was designed by Cecilio Ruiz @ceciliorz
Security
If you believe you have found a security vulnerability in Workflow SDK, we encourage you to responsibly disclose this and not open a public issue.
To participate in our Open Source Software Bug Bounty program, please email responsible.disclosure@vercel.com. We will add you to the program and provide further instructions for submitting your report.