LiteLLM / LiteLLM

LiteLLM proxy buffers Anthropic streamed responses instead of sending deltas incrementally

Production LiteLLM proxy user expects incremental streaming for Anthropic model calls but receives all content in a single buffered batch — breaks real-time chat UX Includes evidence for LiteLLM troubleshooting demand.

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

Category: LiteLLM
Error signature: Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
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

Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config is a LiteLLM failure pattern reported for developers trying to production litellm proxy user expects incremental streaming for anthropic model calls but receives all content in a single buffered batch — breaks real-time chat ux. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #28384 on BerriAI/litellm opened May 20, 2026 (13 hours ago) by dogmd. The bug is Anthropic-specific — OpenAI proxied calls stream fine with identical settings. User confirmed no nginx buffering (proxy_buffering off). Involves LiteLLM v1.85.0 running on Kubernetes with PostgreSQL DB. High urgency: broken streaming is critical for any production chat application using Anthropic models through LiteLLM proxy.

Common causes

GitHub Issue #28384 on BerriAI/litellm opened May 20, 2026 (13 hours ago) by dogmd. The bug is Anthropic-specific — OpenAI proxied calls stream fine with identical settings. User confirmed no nginx buffering (proxy_buffering off). Involves LiteLLM v1.85.0 running on Kubernetes with PostgreSQL DB. High urgency: broken streaming is critical for any production chat application using Anthropic models through LiteLLM proxy.

Quick fixes

Confirm the exact error signature matches Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config.
Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
Compare the failing environment with a known working setup, then change one configuration value at a time.

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 Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config 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 Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config mean in LiteLLM?

Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config indicates the workflow described by "LiteLLM proxy buffers Anthropic streamed responses instead of sending deltas incrementally" failed in a LiteLLM context. Start by confirming the exact signature and the component that emitted it.

What should I check first for Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config?

Check whether this cause matches your environment: GitHub Issue #28384 on BerriAI/litellm opened May 20, 2026 (13 hours ago) by dogmd. The bug is Anthropic-specific — OpenAI proxied calls stream fine with identical settings. User confirmed no nginx buffering (proxy_buffering off). Involves LiteLLM v1.85.0 running on Kubernetes with PostgreSQL DB. High urgency: broken streaming is critical for any production chat application using Anthropic models through LiteLLM proxy.

Is the Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config guidance source-backed?

The "LiteLLM proxy buffers Anthropic streamed responses instead of sending deltas incrementally" 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 Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config?

For "LiteLLM proxy buffers Anthropic streamed responses instead of sending deltas incrementally", avoid applying "Compare the failing environment with a known working setup, then change one configuration value at a time." 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 Proxied Anthropic Response is Buffered: response is sent in one large batch despite stream=true setting; works correctly for OpenAI models under same config?

For "LiteLLM proxy buffers Anthropic streamed responses instead of sending deltas incrementally", 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.