Inside Claude Code Web: Anthropic's Private PaaS 'Antspace' and Web App Builder 'Baku' Discovered

A researcher reverse-engineered the Firecracker MicroVM inside Claude Code Web, revealing Anthropic's private infrastructure and platform strategy. The analysis revealed that Anthropic is developing its own PaaS called Antspace and a web app builder called Baku, instead of relying on external hosting.

Antspace: Self-Hosted Deployment Infrastructure

Antspace is an internal system with no internet search results, mentioned as a competitor to Vercel.

• Underlying Technology: Based on Firecracker MicroVM similar to AWS Lambda (4 vCPUs, 16GB RAM, Linux 6.18.5).
• Structure: Deployment-related modules such as deploy, snapshot, and status were confirmed in the directory structure, and patterns for dist.tar.gz and application/x-ndjson were discovered.

Baku: Web App Builder and BYOC

Baku is believed to be the internal codename for the claude.ai web app builder.

• Workflow: When a user makes a request in natural language, Claude generates an application, a Supabase database is automatically provisioned, and the application is deployed to Antspace.
• BYOC Support: It supports BYOC (Bring Your Own Cloud) mode for enterprise customers, designed so that customers run environment-runner on their own infrastructure while the Anthropic API handles orchestration.

Implications

This discovery suggests that Anthropic is building a vertically integrated AI application platform that owns the entire stack, from LLMs to hosting.