Anthropic API / Anthropic API

Anthropic Vertex AI 413 Payload Too Large: Incorrect rejection of requests well under documented 32MB limit

Developer sends ~2MB document payload to Claude Sonnet 4 via Vertex AI and gets 413 error despite being well under the documented 32MB limit — debugging difficult because error misreports the cause Includes evidence for Anthropic API troubleshooting demand.

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

Category: Anthropic API
Error signature: Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected)
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 Anthropic API, 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

Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected) is a Anthropic API failure pattern reported for developers trying to developer sends ~2mb document payload to claude sonnet 4 via vertex ai and gets 413 error despite being well under the documented 32mb limit — debugging difficult because error misreports the cause. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub Issue #1028 on anthropics/anthropic-sdk-python opened Sep 7, 2025 by abhiwebshar. Detailed root-cause analysis reveals Vertex AI incorrectly maps Citations API rate limit violations (actual 429 rate_limit_error) to misleading 413 'Prompt is too long' errors. Payloads as small as 147KB are rejected with 413. Root cause: error misreporting, not actual payload size limit. Affects production use of large-context capabilities on Vertex AI. Also reports 403 errors around 200k tokens blocking full context window usage.

Common causes

GitHub Issue #1028 on anthropics/anthropic-sdk-python opened Sep 7, 2025 by abhiwebshar. Detailed root-cause analysis reveals Vertex AI incorrectly maps Citations API rate limit violations (actual 429 rate_limit_error) to misleading 413 'Prompt is too long' errors. Payloads as small as 147KB are rejected with 413. Root cause: error misreporting, not actual payload size limit. Affects production use of large-context capabilities on Vertex AI. Also reports 403 errors around 200k tokens blocking full context window usage.

Quick fixes

Confirm the exact error signature matches Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected).
Check the Anthropic API 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 Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected) exactly before applying the quick fix.
Compare the failing environment with Anthropic API 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 Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected) mean in Anthropic API?

Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected) indicates the workflow described by "Anthropic Vertex AI 413 Payload Too Large: Incorrect rejection of requests well under documented 32MB limit" failed in a Anthropic API context. Start by confirming the exact signature and the component that emitted it.

What should I check first for Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected)?

Check whether this cause matches your environment: GitHub Issue #1028 on anthropics/anthropic-sdk-python opened Sep 7, 2025 by abhiwebshar. Detailed root-cause analysis reveals Vertex AI incorrectly maps Citations API rate limit violations (actual 429 rate_limit_error) to misleading 413 'Prompt is too long' errors. Payloads as small as 147KB are rejected with 413. Root cause: error misreporting, not actual payload size limit. Affects production use of large-context capabilities on Vertex AI. Also reports 403 errors around 200k tokens blocking full context window usage.

Is the Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected) guidance source-backed?

The "Anthropic Vertex AI 413 Payload Too Large: Incorrect rejection of requests well under documented 32MB limit" 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 Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected)?

For "Anthropic Vertex AI 413 Payload Too Large: Incorrect rejection of requests well under documented 32MB limit", 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 Error code: 413 - Request exceeds the maximum allowed number of bytes. The maximum request size is 32 MB (but payloads of ~2MB are rejected)?

For "Anthropic Vertex AI 413 Payload Too Large: Incorrect rejection of requests well under documented 32MB limit", collect the failing Anthropic API command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.