fix(tools): include trailing output in error briefs and render brief as plain text (#2389)

Signed-off-by: Kai <me@kaiyi.cool>
Co-authored-by: Kai <me@kaiyi.cool>

Author: liruifengv

CHANGELOG.md

@@ -11,6 +11,7 @@ Only write entries that are worth mentioning to users.
 
 ## Unreleased
 
+- Shell: Show trailing output in tool error briefs when commands fail
 ## 1.46.0 (2026-05-28)
 
 - Shell: Support styled text in welcome tips

docs/en/release-notes/changelog.md

@@ -4,6 +4,7 @@ This page documents the changes in each Kimi Code CLI release.
 
 ## Unreleased
 
+- Shell: Show trailing output in tool error briefs when commands fail
 ## 1.46.0 (2026-05-28)
 
 - Shell: Support styled text in welcome tips

docs/zh/release-notes/changelog.md

@@ -4,6 +4,7 @@
 
 ## 未发布
 
+- Shell：工具执行失败时显示完整错误信息
 ## 1.46.0 (2026-05-28)
 
 - Shell：欢迎提示支持样式化文本

src/kimi_cli/acp/tools.py

@@ -142,20 +142,22 @@ async def __call__(self, params: ShellParams) -> ToolReturnValue:
                 else ""
             )
 
+            tail = builder.tail()
+            tail_md = f"\n{tail}" if tail else ""
             if timed_out:
                 return builder.error(
                     f"Command killed by timeout ({timeout_label}){truncated_note}",
-                    brief=f"Killed by timeout ({timeout_label})",
+                    brief=f"Killed by timeout ({timeout_label}){tail_md}",
                 )
             if exit_signal:
                 return builder.error(
                     f"Command terminated by signal: {exit_signal}.{truncated_note}",
-                    brief=f"Signal: {exit_signal}",
+                    brief=f"Signal: {exit_signal}{tail_md}",
                 )
             if exit_code not in (None, 0):
                 return builder.error(
                     f"Command failed with exit code: {exit_code}.{truncated_note}",
-                    brief=f"Failed with exit code: {exit_code}",
+                    brief=f"Failed with exit code: {exit_code}{tail_md}",
                 )
             return builder.ok(f"Command executed successfully.{truncated_note}")
         finally:

src/kimi_cli/tools/shell/__init__.py

@@ -117,9 +117,13 @@ def stderr_cb(line: bytes):
             if exitcode == 0:
                 return builder.ok("Command executed successfully.")
             else:
+                brief = f"Failed with exit code: {exitcode}"
+                tail = builder.tail()
+                if tail:
+                    brief += f"\n{tail}"
                 return builder.error(
                     f"Command failed with exit code: {exitcode}.",
-                    brief=f"Failed with exit code: {exitcode}",
+                    brief=brief,
                 )
         except TimeoutError:
             return builder.error(

src/kimi_cli/tools/utils.py

@@ -127,6 +127,26 @@ def write(self, text: str) -> int:
 
         return chars_written
 
+    def tail(self, max_lines: int = 5, max_line_len: int = 200) -> str:
+        """Return the last non-empty lines from the buffer, joined with newlines.
+
+        Useful for surfacing actionable error context (stderr) in tool result briefs.
+        """
+        collected: list[str] = []
+        for chunk in reversed(self._buffer):
+            for line in reversed(chunk.splitlines()):
+                stripped = line.rstrip()
+                if not stripped.strip():
+                    continue
+                if len(stripped) > max_line_len:
+                    stripped = stripped[:max_line_len] + "..."
+                collected.append(stripped)
+                if len(collected) >= max_lines:
+                    break
+            if len(collected) >= max_lines:
+                break
+        return "\n".join(reversed(collected))
+
     def display(self, *blocks: DisplayBlock) -> None:
         """Add display blocks to the tool result."""
         self._display.extend(blocks)

src/kimi_cli/ui/shell/visualize/_blocks.py

@@ -518,7 +518,7 @@ def _compose(self) -> RenderableType:
                 elif isinstance(block, BriefDisplayBlock):
                     style = "grey50" if not self._result.is_error else "dark_red"
                     if block.text:
-                        lines.append(Markdown(block.text, style=style))
+                        lines.append(Text(block.text.rstrip("\n"), style=style))
                     idx += 1
                 elif isinstance(block, TodoDisplayBlock):
                     markdown = self._render_todo_markdown(block)

tests/utils/test_result_builder.py

@@ -155,3 +155,41 @@ def test_empty_write():
     assert written == 0
     assert builder.n_chars == 0
     assert not builder.is_full
+
+
+def test_tail_empty():
+    builder = ToolResultBuilder()
+    assert builder.tail() == ""
+
+
+def test_tail_basic():
+    builder = ToolResultBuilder()
+    builder.write("first line\nsecond line\nthird line\n")
+    assert builder.tail() == "first line\nsecond line\nthird line"
+
+
+def test_tail_skips_blank_lines():
+    builder = ToolResultBuilder()
+    builder.write("real error\n\n   \n")
+    assert builder.tail() == "real error"
+
+
+def test_tail_respects_max_lines():
+    builder = ToolResultBuilder()
+    builder.write("\n".join(f"line {i}" for i in range(10)) + "\n")
+    assert builder.tail(max_lines=3) == "line 7\nline 8\nline 9"
+
+
+def test_tail_truncates_long_line():
+    builder = ToolResultBuilder()
+    builder.write("x" * 500 + "\n")
+    tail = builder.tail(max_line_len=100)
+    assert tail.endswith("...")
+    assert len(tail) == 103
+
+
+def test_tail_handles_multiple_writes():
+    builder = ToolResultBuilder()
+    builder.write("stdout chunk\n")
+    builder.write("stderr: permission denied\n")
+    assert builder.tail(max_lines=2) == "stdout chunk\nstderr: permission denied"