fix(hooks): extract text from ContentPart for UserPromptSubmit hook

CHANGELOG.md

@@ -11,6 +11,8 @@ Only write entries that are worth mentioning to users.
 
 ## Unreleased
 
+- Core: Fix `UserPromptSubmit` hook receiving an empty string when user input is a list of `ContentPart` objects — the hook now correctly extracts concatenated text content instead of treating non-string input as empty
+
 ## 1.50.0 (2026-09-02)
 
 - Kosong: Stop sending an empty `anthropic-beta` header when no beta features are declared — adaptive thinking removes the interleaved-thinking beta, which previously left an empty header value that some backends reject

docs/en/release-notes/changelog.md

@@ -4,6 +4,7 @@ This page documents the changes in each Kimi Code CLI release.
 
 ## Unreleased
 
+- Core: Fix `UserPromptSubmit` hook receiving an empty string when user input is a list of `ContentPart` objects — the hook now correctly extracts concatenated text content instead of treating non-string input as empty
 - Kosong: Stop sending an empty `anthropic-beta` header when no beta features are declared — adaptive thinking removes the interleaved-thinking beta, which previously left an empty header value that some backends reject
 
 ## 1.49.0 (2026-07-16)

docs/zh/release-notes/changelog.md

@@ -4,6 +4,7 @@
 
 ## 未发布
 
+- Core：修复 `UserPromptSubmit` hook 在用户输入为 `ContentPart` 列表时收到空字符串的问题——hook 现在会正确提取并拼接文本内容，而非将非字符串输入视为空值
 - Kosong：当没有声明任何 beta 特性时不再发送值为空的 `anthropic-beta` 请求头——adaptive thinking 会移除 interleaved-thinking beta，此前会留下一个空值请求头，部分后端会拒绝该请求
 
 ## 1.49.0 (2026-07-16)

src/kimi_cli/soul/kimisoul.py

@@ -689,16 +689,17 @@ async def run(
             # the wait ceiling is hit) must bypass ``UserPromptSubmit``:
             # they are not user input, and a user-configured prompt-blocking
             # hook would drop the notification and hang the wait loop.
-            if not skip_user_prompt_hook:
-                text_input_for_hook = user_input if isinstance(user_input, str) else ""
+            user_message = Message(role="user", content=user_input)
+            text_input = user_message.extract_text(" ").strip()
 
+            if not skip_user_prompt_hook:
                 hook_results = await self._hook_engine.trigger(
                     "UserPromptSubmit",
-                    matcher_value=text_input_for_hook,
+                    matcher_value=text_input,
                     input_data=events.user_prompt_submit(
                         session_id=self._runtime.session.id,
                         cwd=str(Path.cwd()),
-                        prompt=text_input_for_hook,
+                        prompt=text_input,
                     ),
                 )
                 for result in hook_results:
@@ -719,8 +720,6 @@ async def run(
                 mode="plan" if self._plan_mode else "agent",
                 **_provider_telemetry_kwargs(self._runtime.llm),
             )
-            user_message = Message(role="user", content=user_input)
-            text_input = user_message.extract_text(" ").strip()
 
             if command_call := parse_slash_command_call(text_input):
                 command = self._find_slash_command(command_call.name)

tests/core/test_user_prompt_submit_hook.py

@@ -0,0 +1,80 @@
+"""Tests for UserPromptSubmit hook text extraction."""
+
+from __future__ import annotations
+
+from typing import cast
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from kosong.message import ContentPart, TextPart
+
+from kimi_cli.hooks.engine import HookEngine
+from kimi_cli.soul.kimisoul import KimiSoul
+
+
+def _make_runnable_soul() -> KimiSoul:
+    """Minimal KimiSoul bypassing __init__, just enough for run()."""
+    soul = object.__new__(KimiSoul)
+
+    runtime = MagicMock()
+    runtime.session.id = "test-session"
+    runtime.approval_runtime = None
+    runtime.oauth.ensure_fresh = AsyncMock()
+    soul._runtime = runtime
+
+    ctx = MagicMock()
+    ctx.history = []
+    ctx.append_message = AsyncMock()
+    soul._context = ctx
+
+    soul._hook_engine = MagicMock(spec=HookEngine)
+    soul._hook_engine.trigger = AsyncMock(return_value=[])
+
+    soul._loop_control = MagicMock()
+    soul._loop_control.max_ralph_iterations = 0
+
+    soul._plan_mode = False
+
+    soul._agent = MagicMock()
+    soul._agent.system_prompt = "sys"
+
+    soul._turn = AsyncMock(return_value=MagicMock())
+    soul._slash_commands = []
+    soul._steer_queue = MagicMock()
+    soul._steer_queue.empty.return_value = True
+
+    soul._stop_hook_active = False
+    soul._injection_providers = []
+    soul._compaction = MagicMock()
+    soul._checkpoint = AsyncMock()
+
+    return soul
+
+
+@pytest.mark.asyncio
+async def test_user_prompt_submit_hook_receives_text_from_string() -> None:
+    """When user_input is a plain string, the hook receives it as prompt."""
+    soul = _make_runnable_soul()
+
+    with patch("kimi_cli.soul.kimisoul.wire_send"):
+        await soul.run("hello world")
+
+    call_args = cast(AsyncMock, soul._hook_engine.trigger).call_args_list[0]
+    assert call_args[0][0] == "UserPromptSubmit"
+    assert call_args[1]["matcher_value"] == "hello world"
+    assert call_args[1]["input_data"]["prompt"] == "hello world"
+
+
+@pytest.mark.asyncio
+async def test_user_prompt_submit_hook_receives_text_from_content_parts() -> None:
+    """When user_input is a list of ContentPart, the hook receives extracted text."""
+    soul = _make_runnable_soul()
+    parts: list[ContentPart] = [TextPart(text="hello"), TextPart(text="world")]
+
+    with patch("kimi_cli.soul.kimisoul.wire_send"):
+        await soul.run(parts)
+
+    call_args = cast(AsyncMock, soul._hook_engine.trigger).call_args_list[0]
+    assert call_args[0][0] == "UserPromptSubmit"
+    assert call_args[1]["matcher_value"] == "hello world"
+    assert call_args[1]["input_data"]["prompt"] == "hello world"