difyctl SSE read failures become unhandled rejections while the consumer processes an event #43942

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Dify version

Source main 0838e2511da0ef0953b59d90d5407e0b441e2b32, difyctl 1.17.1.

Cloud or Self Hosted

Self Hosted (Source). Isolated CLI stream reproduction on Windows, Node.js 24.18.0; no deployed server or model call.

Steps to reproduce

cli/src/call/sse.ts starts a background read pump and only awaits its Promise when the consumer drains the queue. If the response body fails while the async generator is suspended at a yielded event, the pump rejects before a handler is attached. Node's default unhandled-rejection policy terminates the process before the consumer can handle the stream error.

With the CLI dependencies installed, save this as cli/repro.mjs and run node --unhandled-rejections=strict cli/repro.mjs from the repository root:

import { parseSSE } from './src/call/sse.ts'

let controller
const body = new ReadableStream({ start(c) { controller = c } })
const events = parseSSE(body)
controller.enqueue(new TextEncoder().encode('data: hello\n\n'))
console.log('first event:', await events.next())
controller.error(new Error('network disconnected'))
// Represents time spent writing/processing the previously yielded event.
await new Promise(resolve => setTimeout(resolve, 30))
try {
  await events.next()
} catch (error) {
  console.log('caught by consumer:', error.message)
}

The reproduction used an unchanged snapshot of sse.ts with the repository-pinned eventsource-parser@4.1.1. It exits with status 1 before printing caught by consumer.

Proposed focused fix: attach a rejection observer to the pump immediately, retaining the existing await that propagates the original error to the consumer. Add a regression that yields one event, fails the response body while the consumer is suspended, and verifies that resuming consumption rejects with that error without an unhandled rejection. This does not add retries or change SSE event ordering.

✔️ Expected Behavior

A failed response body is reported through the iterator and can reach the CLI's normal error handling, including when the consumer is temporarily processing an event.

❌ Actual Behavior

first event:
Error: network disconnected
    at .../repro.mjs:...
Node.js v24.18.0

The process exits before the surrounding consumer's catch runs.

From Codex