[BUG] Multi-turn tool use in -p mode fails with "tool_use ids must be unique" (regression in 2.1.19)

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 using Claude Code in non-interactive print mode (-p) with tools enabled and --max-turns > 1, the second API call after a tool execution fails with:

echo "Read the file package.json" | ~/.local/share/claude/versions/2.1.19 -p --max-turns 2 --allowedTools "Read"

Fails with:

API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.1: `tool_use` ids must be unique"},"request_id":"req_011CXWiczWyfqE6xJjdJ3ktn"}

This is a regression introduced in version 2.1.19. Versions 2.1.17 and 2.1.18 work correctly.

What Should Happen?

Claude reads the file and returns a summary.

Error Messages/Logs

Steps to Reproduce

echo "Read the file package.json" | ~/.local/share/claude/versions/2.1.19 -p --max-turns 2 --allowedTools "Read"

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.18

Claude Code Version

2.1.19

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

From ~/.claude/debug/*.txt when the error occurs:

  2026-01-26T20:29:51.437Z [DEBUG] Stream started - received first chunk
  2026-01-26T20:29:52.958Z [DEBUG] executePreToolHooks called for tool: Read
  2026-01-26T20:29:53.016Z [DEBUG] Getting matching hook commands for PostToolUse with query: Read
  2026-01-26T20:29:53.080Z [DEBUG] [API:request] Creating client, ANTHROPIC_CUSTOM_HEADERS present: false, has Authorization header: false
  2026-01-26T20:29:53.080Z [DEBUG] [API:auth] OAuth token check starting
  2026-01-26T20:29:53.080Z [DEBUG] [API:auth] OAuth token check complete
  2026-01-26T20:29:53.221Z [ERROR] Error in non-streaming fallback: 400 {"type":"error","error":{"type":"invalid_request_error","message":"messages.1.content.1: tool_use ids must be
  unique"},"request_id":"req_011CXWd4ekrvcjusemBs62DQ"}

The error messages.1.content.1 indicates that in the second message (index 1), the second content block (index 1) contains a duplicate tool_use id. This suggests the CLI is incorrectly constructing the
conversation history when making the follow-up API call after tool execution.

The error occurs consistently with any tool (Read, Glob, Grep, Bash) and any model (opus, sonnet, haiku).

With --output-format stream-json --verbose, we can see the tool executes successfully:
```json
{"type":"assistant","message":{"content":[{"type":"tool_use","id":"toolu_01LnYAiD1gBt2qQWUUGZNaWM","name":"Glob","input":{"pattern":"**/*.ts"}}]}}
{"type":"user","message":{"content":[{"tool_use_id":"toolu_01LnYAiD1gBt2qQWUUGZNaWM","type":"tool_result","content":"..."}]}}

But then the next API call fails with the duplicate ID error.