DSH Bun Compatibility Patch

A compatibility layer that lets DeepSeek Harness (DSH) run on Bun 1.3.14+ without a Node bridge.

At launch the layer rewrites two files inside the user's installed DSH packages:

• node_modules/@deepseek-ai/dsh-code-runtime-worker-thread/lib/index.js — points its node:module import at this compat layer.
• node_modules/@deepseek-ai/dsh/lib/profile-boot-*.js — guards the Cordis server-side HMR loop, which depends on a Node-internal ESM loader hook that Bun does not provide.

Both edits are reverted on exit, so the user's node_modules is left untouched when the process terminates cleanly.

Problem it solves

DSH relies on a handful of Node APIs. Bun 1.3.14 covers most of them natively, but exactly one missing surface is relevant to DSH code runtime:

• node:module.stripTypeScriptTypes — Bun's node:module shim does not export this function. The compat layer re-implements it on top of Bun.Transpiler({ loader: "ts" }).transformSync, which is semantically equivalent and synchronous, matching the contract DSH expects when passing TypeScript source through workerData.

Everything else DSH uses is already covered by Bun:

• node:worker_threads — fully supported (Worker, workerData, parentPort, resourceLimits, stdout / stderr, eventLoopUtilization).
• Cordis server-side HMR — disabled by an env-gated guard because Bun lacks the Node-internal ESM loader hooks Cordis relies on.

No Node process is forked, no node binary is required on PATH, and no shadow directory is created.

Requirements

• Bun >= 1.3.14 (recommended >= 1.4.0).
• @deepseek-ai/dsh ^0.1.1-rc.2.

Verify your runtime:

bun --version

The patch is written against the build artifacts shipped with DSH 0.1.1-rc.2. When upgrading Bun or DSH, re-verify that the patch logic still applies.

Installation

Install alongside DSH in the same project:

bun add -d dsh-bun-compat-patch
bun add @deepseek-ai/dsh
bun run build

bun run build produces ./lib/{preload,node-module}.js (plus .map source maps).

Usage

Launch DSH through Bun with the compat preload:

bun --preload ./lib/preload.js ./node_modules/@deepseek-ai/dsh/lib/bin.js web --port 39881

The preload detects the DSH entry, applies the in-place patches, spawns the DSH process as a child Bun runtime, forwards SIGINT / SIGTERM, and restores the original files before exit.

Environment variables

Variable	Set by	Purpose
DSH_BUN_COMPAT_CHILD	preload	Marks the spawned child so the preload becomes a no-op there. Prevents recursive patching.
DSH_BUN_COMPAT_DISABLE_HMR	preload	Tells the patched profile-boot-*.js files to skip the Cordis HMR loop.
DSH_BUN_COMPAT_LIB	preload (optional)	Override for the directory holding lib/node-module.js. The preload normally walks up from import.meta.dir to locate it.
DSH_BUN_COMPAT_DEBUG	user	When set, prints an indented tree of any uncaught error (including cause and aggregated errors[]) to stderr.

How the in-place patch works

1. prepareInPlacePatch reads dsh-code-runtime-worker-thread/lib/index.js, backs the bytes up to $TMPDIR/dsh-bun-compat-patch-backup-*/index.js.bak, and rewrites the from "node:module" import to from "<compatLib>/node-module.js" via a file:// URL. A marker comment is prepended so a second run can detect the file is already patched and skip re-patching.
2. patchHmrGuards iterates every dsh/lib/profile-boot-*.js and prefixes the existing if (!signalShutdown.signal.aborted && ctx.fiber.state === 2 && ctx.get("loader") !== void 0) try { guard with !process.env.DSH_BUN_COMPAT_DISABLE_HMR && so the HMR loop short-circuits under Bun.
3. On clean exit, signal, or process.exit, restorePatch walks every backup and writes the original bytes back, then deletes the backup directory.

If the parent dies before cleanup (kill -9, power loss) a follow-up run will see the marker on the DSH file but no corresponding backup; it logs and skips, leaving the file patched. The user must reinstall DSH (or restore the file manually) in that case. Treat any kill -9 of the parent as leaving DSH in a dirty state.

Project layout

src/
  preload.ts      # Bun --preload entry; orchestrates patching + child spawn
  node-module.ts  # stripTypeScriptTypes implementation backed by Bun.Transpiler
  shadow.ts       # in-place patch / restore / HMR-guard helpers
  diagnostic.ts   # optional uncaught-error tree printer (gated on env)
build.ts          # bundles preload + emits node-module.js into ./lib
tsconfig.json     # strict TS, noEmit, noUnusedLocals / noUnusedParameters

The build emits only two files into ./lib:

• preload.js — bundled with shadow.ts and diagnostic.ts inlined.
• node-module.js — standalone, referenced via file:// URL from the patched DSH entry.

Scripts

Script	What it does
bun run build	Build ./lib from ./src.
bun run typecheck	tsc --noEmit against the strict tsconfig.
bun run pack	bun pm pack — produce the npm tarball.

License

MIT.