[wrangler] Python Workers: wrangler dev/types fail with blank `service core:user:: Uncaught Error`

## Observed symptom Python Workers: `wrangler dev` and `wrangler types` fail with blank `service core:user:: Uncaught Error` while loading Pyodide ### What versions & operating system are you using? - Ubuntu 24.04.5 LTS x86_64 - Node v24.21.0 - Wrangler 4.138.0 - workerd 2026-09-21 - compatibility_date: 2026-09-21 - compatibility_flags: ["python_workers"] wrangler.jsonc: ``` { "$schema": "./node_modules/wrangler/config-schema.json", "name": "steep-sun-3088", "main": "src/entry.py", "compatibility_date": "2026-09-21", "compatibility_flags": ["python_workers"] } ``` Minimal entry.py: ``` from workers import Response, WorkerEntrypoint class Default(WorkerEntrypoint): async def fetch(self, request): return Response("OK") ``` Reproduction: 1. npm install 2. npx wrangler@latest dev --log-level debug 3. npx wrangler types ### Please provide a link to a minimal reproduction N/A - Using Default Python Workers-Onl ## Literal error text ``` service core:user:: Uncaught Error ``` ## Environment GitHub issue cloudflare/workers-sdk #15841; state=open ## Trigger / context ### What versions & operating system are you using? - Ubuntu 24.04.5 LTS x86_64 - Node v24.21.0 - Wrangler 4.138.0 - workerd 2026-09-21 - compatibility_date: 2026-09-21 - compatibility_flags: ["python_workers"] wrangler.jsonc: ``` { "$schema": "./node_modules/wrangler/config-schema.json", "name": "steep-sun-3088", "main": "src/entry.py", "compatibility_date": "2026-09-21", "compatibility_flags": ["python_workers"] } ``` Minimal entry.py: ``` from workers import Response, WorkerEntrypoint class Default(WorkerEntrypoint): async def fetch(self, request): return Response("OK") ``` Reproduction: 1. npm install 2. npx wrangler@latest dev --log-level debug 3. npx wrangler types ### Please provide a link to a minimal reproduction N/A - Using Default Python Workers-Only Template ### Describe the Bug Full Disclosure: I used an LLM to assist with creating this bug report, but it was human tested and reviewed. Observed: - dev logs “Loading Pyodide bundle from internet” for pyodide_314.0.6_2026-08-17_6.capnp.bin, then fails: service core:user:ProxyWorker: Uncaught Error: Error in ProxyController: Could not connect to InspectorProxyWorker ERR_RUNTIME_FAILURE - `wrangler types` gets through “Generating project types...” and fails at “Generating runtime types...”: service core:user:: Uncaught Error: ERR_RUNTIME_FAILURE Checks: - curl downloads exact bundle successfully: HTTP/2 200; content-length 13727600; exit 0 - SHA-256: 3c3fd5a4179230e2 ## Source evidence - https://github.com/cloudflare/workers-sdk/issues/15841 (2026-09-24T17:27:38Z) — GitHub issue #15841 ## Freshness - classification: FRESH_14D - retrieved_at: 2026-10-02T09:43:35.178343Z - scout_id: C83d6d13eb4 ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.