Emscripten pthread-based WASM module fails to initialize in Bun while working in Node

[kevgeoleo]

What version of Bun is running?

1.3.11-canary.1+9e93bfa1b

What platform is your computer?

Linux 5.10.0-12-amd64 x86_64 x86_64

What steps can reproduce the bug?

Hi,

I would like to report a behavior in Bun that can be reproduced using the below snippet:

import { init } from "z3-solver";

const { Context } = await init();
const { Solver, Int, And } = new Context("main");

const x = Int.const("x");

const solver = new Solver();
solver.add(And(x.ge(0), x.le(9)));

// This call should complete without throwing, printing a satisfiability result such as `sat`.
console.log(await solver.check());

What is the expected behavior?

Work without throwing Assertion error

root@KContainer:~/17171# node poc.mjs
sat

What do you see instead?

root@KContainer:~/17171# bun run poc.mjs
Aborted(Assertion failed)
worker: onmessage() captured an uncaught exception: RuntimeError: Aborted(Assertion failed)
RuntimeError: Aborted(Assertion failed)
    at abort (/home/c01kele/node_modules/z3-solver/build/z3-built.js:848:27)
    at assert (/home/c01kele/node_modules/z3-solver/build/z3-built.js:396:5)
    at removeRunDependency (/home/c01kele/node_modules/z3-solver/build/z3-built.js:805:5)
    at receiveInstance (/home/c01kele/node_modules/z3-solver/build/z3-built.js:1019:5)
    at wasmModuleReceived (/home/c01kele/node_modules/z3-solver/build/z3-built.js:1062:9)
    at handleMessage (/home/c01kele/node_modules/z3-solver/build/z3-built.js:539:9)
Pthread 0x01d1d0e8 sent an error! undefined:undefined: Aborted(Assertion failed)
1616 |           var message = 'worker sent an error!';
1617 |           if (worker.pthread_ptr) {
1618 |             message = `Pthread ${ptrToString(worker.pthread_ptr)} sent an error!`;
1619 |           }
1620 |           err(`${message} ${e.filename}:${e.lineno}: ${e.message}`);
1621 |           throw e;
                       ^
error: Aborted(Assertion failed)
      at <anonymous> (/home/c01kele/node_modules/z3-solver/build/z3-built.js:1621:17)
      at <anonymous> (/home/c01kele/node_modules/z3-solver/build/z3-built.js:1626:44)
      at emitError (node:events:43:23)
      at #onError (node:worker_threads:222:14)
^C

Additional information

No response

[github-actions]

Found 3 possible duplicate issues:

1. Z3 doesn't work in Bun #19453
2. z3 optimizer crashes #25454
3. RangeError: Maximum call stack size exceeded when using z3-solver #7816

This issue will be automatically closed as a duplicate in 3 days.

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🤖 Generated with Claude Code

[robobun]

✅ Reproduced. In a node:worker_threads worker, Bun was dispatching parent messages to self.onmessage AND parentPort.on("message", …) listeners — Node only dispatches the latter. z3-solver sets self.onmessage = handleMessage and has parentPort.on("message", (m) => onmessage({data:m})), so handleMessage was running twice per message and the wasm-instantiate run-dependency assertion failed on the second call. Fix: #29215