Architecture

Architecture

Vespasian uses a two-stage pipeline that separates traffic capture from specification generation.

Why Two Stages

• Capture once, generate many. Run different generators against the same capture without re-scanning.
• Debuggable. The capture file is inspectable JSON, isolating capture bugs from generation bugs.
• Composable. Import traffic from any source (browser crawls, proxy captures, mobile testing).
• Offline analysis. Generate specifications without network access, useful during limited engagement windows.

Pipeline Components

Component	Purpose	Supported Types
Crawler	Captures HTTP traffic via one of two backends: a headless Chrome browser (go-rod, full JavaScript/SPA support, default) or a dependency-free stdlib net/http engine (--headless=false)	Protocol-agnostic
Importers	Convert Burp Suite XML, HAR, and mitmproxy traffic to capture format	All three formats
Classifier	Separates API calls from static assets using heuristics	REST, GraphQL, WSDL
Prober	Enriches endpoints via active requests	OPTIONS, JSON schema, WSDL fetch, GraphQL introspection
Generator	Produces specification files from classified and probed traffic	OpenAPI 3.0, GraphQL SDL, WSDL

Package Layout

cmd/vespasian/          CLI entry point
pkg/crawl/              Headless browser crawler + capture format
pkg/importer/           Traffic importers (Burp, HAR, mitmproxy)
pkg/classify/           API classification (REST, GraphQL, WSDL)
pkg/probe/              Endpoint probing (OPTIONS, schema, WSDL, GraphQL introspection)
pkg/generate/
  ├── rest/             OpenAPI 3.0 generation, path normalization, schema inference
  ├── graphql/          GraphQL SDL generation, introspection, traffic inference
  └── wsdl/             WSDL generation, SOAP operation extraction

See Also

• CLI Reference
• REST API Discovery
• GraphQL Discovery
• SOAP WSDL Discovery