bun-agent

n2b — Node.js -> Bun codemod

n2b analyses a Node.js project and reports (or automatically fixes) incompatibilities with the Bun runtime. It covers:

• Rewriting npm / npx / pnpm / yarn -> bun / bunx in package.json scripts, GitHub Actions workflows, shell scripts, and Dockerfiles.
• The node: prefix on builtin imports (fs, path, crypto, ...).
• Dependencies made redundant by native Bun APIs (dotenv, node-fetch, uuid, better-sqlite3, rimraf, ...).
• Migrating Node idioms to Bun (fs.readFileSync -> Bun.file().text(), fileURLToPath(import.meta.url) -> import.meta.dir, node shebang -> bun, actions/setup-node -> oven-sh/setup-bun@v2).
• Detecting rival lockfiles and Node APIs unsupported by Bun.

Architecture (v0.4.0 — Turborepo style)

n2b/
├── schema/v2.json                      <- single source of truth for the JSON contract
├── crates/
│   ├── n2b-core/                       <- orchestrator
│   ├── n2b-types/                      <- data models (Rust)
│   ├── n2b-rules/                      <- rules
│   ├── n2b-scanners/                   <- AST / file scanners
│   ├── n2b-report/                     <- SARIF/JSON render engines
│   ├── n2b-ai/                         <- AI / LLM integration
│   ├── n2b-github/                     <- GitHub integration
│   ├── n2b-cli/                        <- `n2b` binary
│   └── n2b-native/                     <- cdylib FFI
├── packages/
│   ├── n2b/                            <- main TS wrapper (cli)
│   ├── n2b-types/                      <- generated TypeScript types
│   ├── n2b-plugin/                     <- native Bun plugin
│   └── n2b-shims/                      <- native Bun shims
├── turbo.json                          <- global Turborepo configuration
├── scripts/generate-schema-types.ts    <- Rust + TS codegen
└── tests/
    ├── fixture/                        <- test project
    ├── rpb-dashboard-baseline/         <- snapshots
    ├── snapshots/baseline/
    └── compare-baseline.sh

Installation

# Rust CLI binary
cargo build --release -p n2b
sudo install -m755 target/release/n2b /usr/local/bin/n2b

# TypeScript facade
bun install

CLI usage

# Dry-run audit (exit 1 if there are findings)
n2b .

# Apply the safe fixes
n2b . --fix

# Aggressive migration (rewrites Node APIs -> Bun)
n2b . --aggressive

# Full migration (--fix --aggressive + side effects: bun install, removes pnpm-lock.yaml, etc.)
n2b . --migrate

# Reports
n2b . --report=text                     # default, colourised
n2b . --report=json                     # schema v2 (see schema/v2.json)
n2b . --report=jsonl                    # streamable
n2b . --report=markdown
n2b . --report=sarif                    # GitHub Code Scanning

# Exclusions
n2b . --ignore="**/legacy/**" --ignore="**/fixtures/**"

TypeScript usage — @aphrody/n2b-core

Subprocess wrapper

import { scan, rules } from "@aphrody/n2b-core";

const report = await scan(".", { mode: "check", quiet: true });
console.log(`${report.findings_total} finding(s) in ${report.files_scanned} file(s)`);

Bun plugin (lint at build time)

import { n2bPlugin } from "@aphrody/n2b-plugin";

Bun.plugin(n2bPlugin({ onFindings: "warn" }));
// or "error" to fail builds that have findings

Bun-native shims

import { env, fs, path, shell } from "@aphrody/n2b-shims";

const DB = env.str("DATABASE_URL", { required: true });
const port = env.int("PORT", { default: 3000 });
const config = await fs.readJson<Config>(path.relativeTo(import.meta, "config.json"));
const result = await shell.run("git rev-parse HEAD");

Rules

Category	IDs	--fix	--aggressive
CLI (npm/pnpm/yarn/npx)	cli/*	yes	yes
node: prefix	imports/node-prefix	yes	yes
Shebang	shebang/node	yes	yes
GitHub Actions	ci/*	yes	yes
package.json (scripts, engines, deps)	pkg/*	partial	partial
Rival lockfiles	lock/rival	report	report
Package replacements	imports/bun-native	report	yes (bun: / node: specifiers)
Node APIs -> Bun	api/*	report	yes

List the rules: n2b rules or n2b rules --report=json.

Development

# Full test suite
turbo run test                            # full TS + Rust test via Turbo
cargo test --workspace                    # Rust tests (schema + contract + proptest)
bash tests/compare-baseline.sh            # CLI-as-API baseline (13 assertions)

# Quality (lint & format)
turbo run //#quality                      # global oxlint, oxfmt, taplo
cargo fmt --all -- --check
cargo clippy --workspace --all-targets -- -D warnings
turbo run typecheck                       # TypeScript type-checking

# Regenerate types from the schema
bun run codegen:schema

Exit codes