Claude Code / AI Coding Tools

Claude Code Desktop App Hangs on New Messages in Long Sessions

Fix Claude Code desktop app hanging on messages in long sessions 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: Anthropic API 400 messages: text content blocks must be non-empty
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

Anthropic API 400 messages: text content blocks must be non-empty is a Claude Code failure pattern reported for developers trying to fix claude code desktop app hanging on messages in long sessions. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Desktop app on macOS, Opus 4.7 model, Max tier. Loading indicator appears but nothing streams. No error message, no timeout. Reproduces on every new message in affected sessions. Fresh sessions on same repos work normally.

Common causes

New messages sent to long-running Claude Code desktop sessions hang indefinitely with no response, no error, and no timeout. The loading indicator appears but nothing streams back. Fresh sessions work normally. Affects Max tier users paying premium prices.
Desktop app on macOS, Opus 4.7 model, Max tier. Loading indicator appears but nothing streams. No error message, no timeout. Reproduces on every new message in affected sessions. Fresh sessions on same repos work normally.

Quick fixes

Confirm the exact error signature matches Anthropic API 400 messages: text content blocks must be non-empty.
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 Anthropic API 400 messages: text content blocks must be non-empty 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 Anthropic API 400 messages: text content blocks must be non-empty mean in Claude Code?

Anthropic API 400 messages: text content blocks must be non-empty indicates the workflow described by "Claude Code Desktop App Hangs on New Messages in Long 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 Anthropic API 400 messages: text content blocks must be non-empty?

Check whether this cause matches your environment: New messages sent to long-running Claude Code desktop sessions hang indefinitely with no response, no error, and no timeout. The loading indicator appears but nothing streams back. Fresh sessions work normally. Affects Max tier users paying premium prices.

Is the Anthropic API 400 messages: text content blocks must be non-empty guidance source-backed?

The "Claude Code Desktop App Hangs on New Messages in Long 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 Anthropic API 400 messages: text content blocks must be non-empty?

For "Claude Code Desktop App Hangs on New Messages in Long 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 Anthropic API 400 messages: text content blocks must be non-empty?

For "Claude Code Desktop App Hangs on New Messages in Long 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.