Claude Code / AI Coding Tools

Claude Code API 400 'cache_control cannot be set for empty text blocks' Bricks Sessions

Fix Claude Code session crash caused by 400 error on cache_control with empty text blocks Includes evidence for Claude Code troubleshooting demand.

Source-backed Last updated May 14, 2026 1 source Needs local verification

Category: AI Coding Tools
Error signature: cache_control cannot be set for empty text blocks
Quick fix: Compare the failing environment with a known working setup, then change one configuration value at a time.
Updated: May 14, 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 Claude Code, 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

cache_control cannot be set for empty text blocks is a Claude Code failure pattern reported for developers trying to fix claude code session crash caused by 400 error on cache_control with empty text blocks. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Multiple users report Claude Code Cloud sessions crashing with API Error 400 messages.248.content.3.text: cache_control cannot be set for empty text blocks. Sessions become unrecoverable. Happens in both long (>200 messages) and new (~25 messages) sessions, triggered by pasting screenshots.

Common causes

Claude Code sessions become permanently unusable once this error occurs. The agent constructs request payloads with empty text content blocks that have cache_control markers, which the Anthropic API rejects. Users on paid Max tier plans lose active coding sessions with no recovery path.
Multiple users report Claude Code Cloud sessions crashing with API Error 400 messages.248.content.3.text: cache_control cannot be set for empty text blocks. Sessions become unrecoverable. Happens in both long (>200 messages) and new (~25 messages) sessions, triggered by pasting screenshots.

Quick fixes

Confirm the exact error signature matches cache_control cannot be set for empty text blocks.
Check the Claude Code 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 cache_control cannot be set for empty text blocks exactly before applying the quick fix.
Compare the failing environment with Claude Code 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 cache_control cannot be set for empty text blocks mean in Claude Code?

cache_control cannot be set for empty text blocks indicates the workflow described by "Claude Code API 400 'cache_control cannot be set for empty text blocks' Bricks Sessions" failed in a AI Coding Tools context. Start by confirming the exact signature and the component that emitted it.

What should I check first for cache_control cannot be set for empty text blocks?

Check whether this cause matches your environment: Claude Code sessions become permanently unusable once this error occurs. The agent constructs request payloads with empty text content blocks that have cache_control markers, which the Anthropic API rejects. Users on paid Max tier plans lose active coding sessions with no recovery path.

Is the cache_control cannot be set for empty text blocks guidance source-backed?

The "Claude Code API 400 'cache_control cannot be set for empty text blocks' Bricks Sessions" 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 cache_control cannot be set for empty text blocks?

For "Claude Code API 400 'cache_control cannot be set for empty text blocks' Bricks Sessions", 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 cache_control cannot be set for empty text blocks?

For "Claude Code API 400 'cache_control cannot be set for empty text blocks' Bricks Sessions", collect the failing Claude Code command or request, non-secret configuration, versions, timestamps, request IDs when available, and the smallest reproduction that still triggers the signature.