LiteLLM Bedrock SigV4 returns 401 due to case-sensitive Content-Type header duplication

What this error means

SigV4 401 Unauthorized on bedrock/claude_platform/* route — signature never matches due to duplicate Content-Type header values is a LiteLLM failure pattern reported for developers trying to fix litellm bedrock authentication failure caused by case-sensitive content-type header key collision causing double headers in sigv4 signing. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

GitHub issue BerriAI/litellm#28491 — single-line fix needed: Content-Type uppercase conflicts with lowercase content-type in dict spread. botocore joins them into duplicate header, breaking AWS SigV4 signature match. One-line patch resolves production auth failures. Strong commercial impact for enterprise LiteLLM proxy users routing to AWS Bedrock.

Common causes

• GitHub issue BerriAI/litellm#28491 — single-line fix needed: Content-Type uppercase conflicts with lowercase content-type in dict spread. botocore joins them into duplicate header, breaking AWS SigV4 signature match. One-line patch resolves production auth failures. Strong commercial impact for enterprise LiteLLM proxy users routing to AWS Bedrock.

Quick fixes

1. Confirm the exact error signature matches SigV4 401 Unauthorized on bedrock/claude_platform/* route — signature never matches due to duplicate Content-Type header values.
2. Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
3. Verify the account session, API key, provider settings, and environment where the failing tool is running.

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

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. 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.

Sources checked

• https://github.com/BerriAI/litellm/issues/28491

Evidence note: GitHub issue BerriAI/litellm#28491 — single-line fix needed: Content-Type uppercase conflicts with lowercase content-type in dict spread. botocore joins them into duplicate header, breaking AWS SigV4 signature match. One-line patch resolves production auth failures. Strong commercial impact for enterprise LiteLLM proxy users routing to AWS Bedrock.

Related errors

• LiteLLM

FAQ

What should I check first?

Start with the exact SigV4 401 Unauthorized on bedrock/claude_platform/* route — signature never matches due to duplicate Content-Type header values text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed LiteLLM workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without SigV4 401 Unauthorized on bedrock/claude_platform/* route — signature never matches due to duplicate Content-Type header values.