[BUG] Claude Code CLI returns blank output for --json-schema

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When submitting any non-interactive prompt with --json-schema flag, the model appears to call the structured output tool, but the CLI never returns the output.

To reproduce:
claude -p --model sonnet --json-schema '{"type":"object","properties":{"color":{"type":"string"},"count":{"type":"number"}},"required":["color","count"]}' "How many legs does a cat have? Reply with the color of the sky and the number of legs."

Returns zero output.

Transcript from the above query (generated via claude-devtools):

---

Session Export

| Property | Value |
|----------|-------|
| Session | c2a9bad2-78a3-4cb3-96b0-2460816b159a |
| Project | /Users/shXXXXXXXXXXXXXXXXXXXXXXXXX |
| Branch | main |
| Date | 2026-03-19 03:04:16 UTC |

Metrics

| Metric | Value |
|--------|-------|
| Duration | 3s |
| Total Tokens | 31,987 |
| Input Tokens | 3 |
| Output Tokens | 71 |
| Cache Read | 6,341 |
| Cache Created | 25,572 |
| Messages | 3 |
| Cost | N/A |

Conversation

User (Turn 1)

How many legs does a cat have? Reply with the color of the sky and the number of legs.

Assistant (Turn 2)

Tool: StructuredOutput
Input: {
"color": "blue",
"count": 4
}

Structured output provided successfully

Tool: StructuredOutput

{
  "color": "blue",
  "count": 4
}

Result:

Structured output provided successfully

What Should Happen?

Output for the above query should be:

{
"color": "blue",
"count": 4
}

Error Messages/Logs

Steps to Reproduce

Just run the following prompt:

claude -p --model sonnet --json-schema '{"type":"object","properties":{"color":{"type":"string"},"count":{"type":"number"}},"required":["color","count"]}' "How many legs does a cat have? Reply with the color of the sky and the number of legs."

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.79 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

<img width="836" height="327" alt="Image" src="https://github.com/user-attachments/assets/188ddc00-dffa-436e-961c-42943a37f1fc" />