diff --git a/src/kimi_cli/tools/file/write.py b/src/kimi_cli/tools/file/write.py
index f6dd53229..eaaa2e9d2 100644
--- a/src/kimi_cli/tools/file/write.py
+++ b/src/kimi_cli/tools/file/write.py
@@ -61,14 +61,9 @@ async def __call__(self, params: Params) -> ToolReturnValue:
         try:
             p = KaosPath(params.path)
 
+            # Auto-resolve relative paths to working directory
             if not p.is_absolute():
-                return ToolError(
-                    message=(
-                        f"`{params.path}` is not an absolute path. "
-                        "You must provide an absolute path to write a file."
-                    ),
-                    brief="Invalid path",
-                )
+                p = self._work_dir / params.path
 
             # Validate path safety
             path_error = await self._validate_path(p)
diff --git a/tests/test_write_file.py b/tests/test_write_file.py
index 95069af3f..8623bc235 100644
--- a/tests/test_write_file.py
+++ b/tests/test_write_file.py
@@ -96,12 +96,14 @@ async def test_write_multiline_content(write_file_tool: WriteFile, temp_work_dir
     assert await file_path.read_text() == content
 
 
-async def test_write_with_relative_path(write_file_tool: WriteFile):
-    """Test writing with a relative path (should fail)."""
-    result = await write_file_tool(Params(path="relative/path/file.txt", content="content"))
+async def test_write_with_relative_path(write_file_tool: WriteFile, temp_work_dir: KaosPath):
+    """Test writing with a relative path (should auto-resolve to work directory)."""
+    result = await write_file_tool(Params(path="test_relative.txt", content="content"))
 
-    assert result.is_error
-    assert "not an absolute path" in result.message
+    assert not result.is_error
+    created_file = temp_work_dir / "test_relative.txt"
+    assert await created_file.exists()
+    assert await created_file.read_text() == "content"
 
 
 async def test_write_outside_work_directory(write_file_tool: WriteFile, outside_file: Path):