tweakcc 4.3.3: new CJS parse-check breaks all ESM bundles (node --check bundle.cjs)

[rgutzen]

Summary

tweakcc 4.3.3 fails to apply any customizations to Claude Code installations whose bundle is ESM, because the new parse-check (node --check bundle.cjs) treats the bundle as CommonJS. Every --apply ends in:

✖ The patched bundle failed to parse. Your customizations were not applied; Claude Code is running the original unmodified version.
import{createRequire as vP5}from"node:module";var MP5=Object.create;...
^

SyntaxError: Cannot use import statement outside a module

Root cause

Claude Code's cli.js has shipped as an ES module ("type": "module" in package.json, top-level import{...}from"...") since v1.0.20 — this is not new.

The node --check bundle.cjs parse-check is new in 4.3.3. 4.3.2 has no parse-check at all (I unpacked tweakcc@4.3.2 and confirmed no mkdtemp/bundle.cjs/PatchedBundleParseError code exists). Because the check writes the bundle to bundle.cjs, Node parses it with CommonJS semantics and rejects the top-level import statements even when the bundle is completely valid ESM.

Verified directly:

# claude-code 2.1.112 cli.js (valid ESM)
cp cli.js /tmp/test.mjs && node --check /tmp/test.mjs   # exit 0
cp cli.js /tmp/test.cjs && node --check /tmp/test.cjs   # SyntaxError: Cannot use import statement outside a module

So the failure is entirely a function of the .cjs extension tweakcc 4.3.3 uses, not the content of the bundle or the user's customizations.

Reproduction

npm i -g @anthropic-ai/claude-code@2.1.112   # last version shipping cli.js (bin: cli.js)
npx tweakcc@4.3.3 --apply --yes
# => "Patched bundle failed to parse"

Note: npx tweakcc@4.3.2 --apply --yes on the exact same install succeeds (patches apply, changesApplied: true).

Two related issues

1. Parse check must use .mjs (or respect the bundle's "type": "module"), since Claude Code bundles are ESM. Using .cjs guarantees failure.

2. Native installs (Claude Code ≥ 2.1.113, incl. npm bin/claude.exe) have a separate, still-open breakage: since 2.1.247 the Bun bundle is split into ESM chunks. extractClaudeJsFromNativeInstallation extracts the entry module /$bunfs/root/cli (a ~20 KB stub of import{...}from"/$bunfs/root/chunk-*.js"), while the actual code (and system prompts) live in the separate chunk-*.js modules. Every patch reports "Could not find ... in cli.js", and even the unpatched entry stub fails the .cjs parse-check. The Claude Code 2.1.231 renames the entry module to /$bunfs/root/cli — extraction fails on every native install #945 fix (entry-module rename) is not sufficient for the chunk-split layout — the chunk modules must be read/inlined.

Environment

• tweakcc 4.3.3 (broken) vs 4.3.2 (works on cli.js installs)
• Claude Code 2.1.112 (npm, bin: cli.js, "type": "module")
• Node v26.7.0, Linux x64