python runtime_error ai_generated true

RuntimeError: ContextVar 'context' already exists

ID: python/fastapi-runtimeerror-starlette-context-already-exists

Also available as: JSON · Markdown · 中文
80%Fix Rate
81%Confidence
0Evidence
2025-03-20First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

Duplicate declaration of a ContextVar in the same scope, often due to middleware or dependency injection conflicts.

generic

中文

在同一作用域中重复声明了ContextVar，通常是由于中间件或依赖注入冲突。

Workarounds

  1. 90% success Remove duplicate ContextVar declaration 
    Ensure only one declaration: from contextvars import ContextVar
context = ContextVar('context', default=None)
  2. 85% success Use a single ContextVar across modules 
    Create a shared module for ContextVar and import it.

Dead Ends

Common approaches that don't work:

  1. Ignoring the error and retrying 90% fail

    ContextVar conflict persists until code is fixed.

  2. Using different variable names without understanding 60% fail

    Root cause is duplicate declaration, not name.