Unhandled Promise Rejection

Web

TL;DR

Unhandled Promise Rejection indicates a runtime failure on Web that interrupts the current user flow.

Symptoms

Unhandled Promise Rejection appears in console output
The page flow breaks for the user

Common Causes

Unexpected state reaches an unsafe path
Input contracts are not enforced at boundaries

How to Verify

Reproduce with deterministic input and capture full logsInspect the first throw site and recent changes around it

Quick Fixes

Add guard checks and a safe fallback path
Disable or rollback the risky code path behind a flag

Proper Fixes

Enforce contracts with types, runtime checks, and tests
Refactor ownership and lifecycle boundaries to remove the failure mode

Example Stack Trace

Unhandled Promise Rejection at app.bundle.js:1:1234

Related Errors

UnknownHostException URLSession Error Main Thread Checker Violation