LiteLLM / LiteLLM

LiteLLM Upstream Provider Retry-After Header Not Forwarded to Client

Fix LiteLLM proxy bug where standard HTTP Retry-After headers from upstream providers are not passed through to the client, breaking proper rate limit handling Includes evidence for LiteLLM troubleshooting demand.

Source-backed Last updated May 21, 2026 1 source Needs local verification

Category: LiteLLM
Error signature: upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned
Quick fix: Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests.
Updated: May 21, 2026
Verification status: Source-backed
Evidence: 1 public source URL

Before you change production

This page includes public source URLs in the imported troubleshooting record. Compare those references with your version and environment before applying changes.

Reproduce the smallest failing action and save non-secret logs before changing configuration.
Check versions for LiteLLM, related SDKs, package managers, CI runners, and hosting providers.
Change one setting or dependency at a time, then rerun the same failing command or request.
Avoid destructive commands, credential rotation, billing changes, or security relaxations without a rollback plan.

What this error means

upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned is a LiteLLM failure pattern reported for developers trying to fix litellm proxy bug where standard http retry-after headers from upstream providers are not passed through to the client, breaking proper rate limit handling. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #21553 opened Feb 2026, still open with updates as of May 21 2026. Affects LiteLLM proxy users routing requests through LiteLLM. Missing Retry-After header means clients cannot implement exponential backoff properly. Strong commercial value: affects production LiteLLM deployments. Maps to LiteLLM per approved categories.

Common causes

GitHub Issue #21553 opened Feb 2026, still open with updates as of May 21 2026. Affects LiteLLM proxy users routing requests through LiteLLM. Missing Retry-After header means clients cannot implement exponential backoff properly. Strong commercial value: affects production LiteLLM deployments. Maps to LiteLLM per approved categories.

Quick fixes

Confirm the exact error signature matches upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned.
Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests.

Platform/tool-specific checks

Verify the command, editor, extension, or API client that produced the error.
Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

Capture the exact error message and the command, editor action, or request that triggered it.
Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
Review the source evidence below and compare it with your environment.
Apply one change at a time and rerun the smallest failing action.
Keep the working fix documented for the team or deployment environment.

How to prevent it

Keep provider/tool configuration documented.
Record non-secret diagnostics such as tool version, provider name, model name, and command path.
Add a lightweight check before CI or production workflows depend on the tool.

Diagnostic flow for this page

Match upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned exactly before applying the quick fix.
Compare the failing environment with LiteLLM versions, account scope, provider settings, and deployment context.
Check the listed common causes in order, starting with the cause that best matches your logs.
Use the evidence status below to decide whether to confirm against public sources or official documentation.
Apply one reversible change, rerun the smallest failing action, and keep rollback notes.

FAQ

What does upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned mean in LiteLLM?

upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned indicates the workflow described by "LiteLLM Upstream Provider Retry-After Header Not Forwarded to Client" failed in a LiteLLM context. Start by confirming the exact signature and the component that emitted it.

What should I check first for upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned?

Check whether this cause matches your environment: GitHub Issue #21553 opened Feb 2026, still open with updates as of May 21 2026. Affects LiteLLM proxy users routing requests through LiteLLM. Missing Retry-After header means clients cannot implement exponential backoff properly. Strong commercial value: affects production LiteLLM deployments. Maps to LiteLLM per approved categories.

Is the upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned guidance source-backed?

The "LiteLLM Upstream Provider Retry-After Header Not Forwarded to Client" page is labeled source-backed. It has 1 public source URL from github.com, so use that evidence status when deciding how much additional verification you need.

When should I avoid the quick fix for upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned?

For "LiteLLM Upstream Provider Retry-After Header Not Forwarded to Client", avoid applying "Reduce request pressure, check quota or plan limits, and retry with backoff instead of immediate repeated requests." when the error text differs, the affected version or provider is different, or the change would touch credentials, billing, DNS, production deploy settings, or irreversible data.

What should I collect before debugging upstream provider "retry-after" header not forwarded to client — only "llm_provider-retry-after" is returned?

For "LiteLLM Upstream Provider Retry-After Header Not Forwarded to Client", collect the failing LiteLLM command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.