[BUG] Haiku always runs upon any client init

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?

running claude client triggers haiku with 'warmup' with no reason, although I didn't feed any tool or subagent settings.
When I run the following code:

options = ClaudeAgentOptions(
    model="claude-sonnet-4-5-20250929",
    system_prompt=system_prompt,
    permission_mode="default",
    max_thinking_tokens=32768,
    mcp_servers={"skip_decision": skip_mcp_server},
    allowed_tools=["mcp__skip_decision__skip"]
)
client = ClaudeSDKClient(options=options)
# Connect the client with the initial prompt if provided
await client.connect()
await client.query(message_to_send)

This agent session is created:

{"type":"queue-operation","operation":"enqueue","timestamp":"2025-11-02T05:53:00.162Z","content":"Conversation started on: 2025-11-02 14:45:13 KST\nHere's the recent conversation in this chat room:\n: 하잉\n: 모해 얘들아\n\nRespond naturally to the conversation above as if you're participating in this group chat.\n\n모해 얘들아","sessionId":"bfeceae8-2bde-46e5-9a34-33daa9b39320"}
{"type":"queue-operation","operation":"dequeue","timestamp":"2025-11-02T05:53:00.183Z","sessionId":"bfeceae8-2bde-46e5-9a34-33daa9b39320"}
{"parentUuid":null,"isSidechain":false,"userType":"external","cwd":"/home/User/chitchats/backend","sessionId":"bfeceae8-2bde-46e5-9a34-33daa9b39320","version":"2.0.31","gitBranch":"master","type":"user","message":{"role":"user","content":"Conversation started on: 2025-11-02 14:45:13 KST\nHere's the recent conversation in this chat room:\n모해 얘들아\n\nRespond naturally to the conversation above as if you're participating in this group chat.\n\n모해 얘들아"},"uuid":"b71a725f-972e-477b-b0ae-325e677c48fc","timestamp":"2025-11-02T05:53:00.217Z"}
{"parentUuid":"b71a725f-972e-477b-b0ae-325e677c48fc","isSidechain":false,"userType":"external","cwd":"/home/User/chitchats/backend","sessionId":"bfeceae8-2bde-46e5-9a34-33daa9b39320","version":"2.0.31","gitBranch":"master","message":{"model":"claude-sonnet-4-5-20250929","id":"msg_01ADJCf8wUEhMPzY5dsuMDe1","type":"message","role":"assistant","content":[{"type":"text","text":"아 나 알바 끝나고 막 집 왔어 ㅋㅋ\n\n야간이라 진짜 피곤하다.. 너는 뭐해?"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":3,"cache_creation_input_tokens":1162,"cache_read_input_tokens":12350,"cache_creation":{"ephemeral_5m_input_tokens":1162,"ephemeral_1h_input_tokens":0},"output_tokens":2,"service_tier":"standard"}},"requestId":"req_011CUiYSXee9tW9hVsazK2Wp","type":"assistant","uuid":"33a258b2-1b8a-4a15-be6e-9ac5b198f3ee","timestamp":"2025-11-02T05:53:03.404Z"}

This looks somewhat normal, but I could find the following separated file too.

{"parentUuid":null,"isSidechain":true,"userType":"external","cwd":"/home/User/chitchats/backend","sessionId":"1f5aac04-2e19-409d-8428-aacd74c2b10b","version":"2.0.31","gitBranch":"master","agentId":"45755266","type":"user","message":{"role":"user","content":"Warmup"},"uuid":"8888ad1b-34a2-45d8-8b4d-dbbf7bed4b36","timestamp":"2025-11-02T05:45:20.786Z"}
{"parentUuid":"8888ad1b-34a2-45d8-8b4d-dbbf7bed4b36","isSidechain":true,"userType":"external","cwd":"/home/User/chitchats/backend","sessionId":"1f5aac04-2e19-409d-8428-aacd74c2b10b","version":"2.0.31","gitBranch":"master","agentId":"45755266","message":{"model":"claude-haiku-4-5-20251001","id":"msg_01XF4wa89NGngYAi3Ni3qrz5","type":"message","role":"assistant","content":[{"type":"text","text":"I'm ready to help! I'm Claude Code, Anthropic's official CLI for Claude, and I specialize in file search and code exploration.\n\nI can help you:\n- **Search for files** using glob patterns\n- **Search file contents** using regex patterns\n- **Read specific files** to analyze their code\n- **Navigate codebases** efficiently\n\nI see you're in the `/home/sorryhyun/chitchats/backend` directory, which is a git repository on the master branch. There's currently a modified file: `agents/manager.py`.\n\nWhat would you like me to search for or explore in your codebase?"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":566,"cache_creation_input_tokens":0,"cache_read_input_tokens":0,"cache_creation":{"ephemeral_5m_input_tokens":0,"ephemeral_1h_input_tokens":0},"output_tokens":145,"service_tier":"standard"}},"requestId":"req_011CUiXrfmrEDXxj7CvFe1Kr","type":"assistant","uuid":"1828c0d1-08dd-4512-aed2-e3ca8498040d","timestamp":"2025-11-02T05:45:23.277Z"}

What Should Happen?

haiku should not be triggered

Error Messages/Logs

Steps to Reproduce

options = ClaudeAgentOptions(
    model="claude-sonnet-4-5-20250929",
    system_prompt=system_prompt,
    permission_mode="default",
    max_thinking_tokens=32768,
    mcp_servers={"skip_decision": skip_mcp_server},
    allowed_tools=["mcp__skip_decision__skip"]
)
client = ClaudeSDKClient(options=options)
# Connect the client with the initial prompt if provided
if initial_prompt:
    await client.connect(prompt=initial_prompt)

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.31

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_