---
title: Runbook — DEPENDENCY_4XX_CLIENT (업스트림 클라이언트 오류)
category: PERMANENT_DEPENDENCY
error_codes: [DEPENDENCY_4XX_CLIENT]
severity: P2
owner: oncall
last_updated: 2026-06-15
status: stub
---

# Runbook: DEPENDENCY_4XX_CLIENT (`runbook://dependency/4xx-client`)

## Symptoms

- HTTP 502 with `error.code=DEPENDENCY_4XX_CLIENT`
- Upstream returned 401/403/400 — credential, scope, or request format issue

## Diagnosis

- Check upstream response body in logs for error detail
- Verify API credentials and scopes are valid

## Action

- Rotate credentials if expired
- Fix request format if API contract changed

## Escalation

- Escalate to upstream API owner if contract change is suspected

---

> **Stub**: Phase D2 — author body after domain adoption. (feature-operational-runbook-contract D9)