Convert Next.js Turbopack bundle analysis data into Unigraph MapGraph JSON.

Background

Next.js ships a command next experimental-analyze -o that runs a production Turbopack build and writes binary analysis data to .next/diagnostics/analyze/data/. This data contains the full module dependency graph plus per-route size attribution.

This crate reads that data and produces a Unigraph MapGraph — a JSON format that Unigraph Explorer can visualize with dominator trees, tiered metrics, force-directed layout, and more.

Data sources

The analyze output directory contains three kinds of files:

• modules.data — Global module dependency graph. Contains every module across all routes and RSC layers, plus sync and async dependency edges. This is ONE graph — edges do not vary per route.

• routes.json — JSON array of route path strings (e.g. ["/", "/about"]).

• Per-route analyze.data — Size attribution data. For each route, which source files contribute how many bytes to the route's output chunks. Contains NO dependency edges — only sizes.

See ANALYZE_DATA_FORMAT.md in this crate for the full binary format specification.

Key design decisions

• Layers always separate: The same file compiled in different RSC layers (app-rsc, app-client, app-ssr) has genuinely different dependency edges and produces separate nodes. A layer label enables UI filtering.

• Single graph, routes as labels: Since edges are global, we produce one graph with route labels on each node indicating which routes include it. Sizes are summed across routes.

• Fragments collapsed by default: Tree-shaking fragments (<exports>, <module evaluation>) are merged back into their parent module unless --fragments is passed. Collapsing unions edges, sums sizes, and removes self-edges that arise from inter-fragment references.

• Tiered traversal: Sync imports map to the "eager" tier, async imports (import()) map to the "lazy" tier. This gives Unigraph's tiered metrics: size#eager (initial load), size#lazy (total), size#eager~dominated (unique cost per module in the initial bundle).

Usage

# Generate analyze data
cd your-next-app && ./node_modules/.bin/next experimental-analyze -o

# Convert to Unigraph (via task runner)
ut unigraph_turbopack .next/diagnostics/analyze/data/ -o graph.json --pretty

# Visualize
ut serve -f graph.json