Merge pull request #3779 from rudycelekli/fix/cow-bash-line-truncation-log-20261017

fix: preserve complete Bash output after line truncation

agent/tools/bash/bash.py

@@ -319,9 +319,9 @@ SAFETY:
 
             # Check if we need to save full output to temp file
             temp_file_path = None
-            total_bytes = len(output.encode('utf-8'))
+            truncation = truncate_tail(output)
 
-            if total_bytes > DEFAULT_MAX_BYTES:
+            if truncation.truncated:
                 # Save full output to temp file. encoding='utf-8' is required:
                 # the default text-mode encoding is the platform locale (e.g.
                 # cp936/GBK on Chinese Windows), which raises UnicodeEncodeError
@@ -331,8 +331,6 @@ SAFETY:
                     f.write(output)
                     temp_file_path = f.name
 
-            # Apply tail truncation
-            truncation = truncate_tail(output)
             output_text = truncation.content or "(no output)"
 
             # Build result

tests/test_bash_full_output.py

@@ -0,0 +1,72 @@
+"""Every truncated shell result must retain an accessible full output log."""
+import os
+import shlex
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+import pytest
+
+from agent.tools.bash.bash import Bash
+from agent.tools.utils.truncate import DEFAULT_MAX_BYTES, DEFAULT_MAX_LINES
+
+
+@pytest.fixture
+def tool(tmp_path, monkeypatch):
+    original = tempfile.NamedTemporaryFile
+
+    def owned_temp_file(*args, **kwargs):
+        kwargs["dir"] = str(tmp_path)
+        return original(*args, **kwargs)
+
+    # Keep generated logs in the owned fixture. No subprocess/stream mocks.
+    monkeypatch.setattr(tempfile, "NamedTemporaryFile", owned_temp_file)
+    return Bash({"cwd": str(tmp_path)})
+
+
+def _run(tool, expression, exit_code=0):
+    script = f"import sys; sys.stdout.write({expression}); sys.exit({exit_code})"
+    command = (subprocess.list2cmdline([sys.executable, "-c", script]) if os.name == "nt"
+               else shlex.quote(sys.executable) + " -c " + shlex.quote(script))
+    return tool.execute({"command": command, "timeout": 10})
+
+
+@pytest.mark.parametrize("kind", ["lines", "bytes", "both"])
+def test_every_truncation_keeps_the_original_output(tool, kind):
+    expressions = {
+        "lines": f"'\\n'.join('row-'+str(i) for i in range({DEFAULT_MAX_LINES + 50}))",
+        "bytes": f"chr(0x1f389)*({DEFAULT_MAX_BYTES}//4+10)",
+        "both": f"'\\n'.join(str(i)+'-'+chr(0x1f389)*10 for i in range({DEFAULT_MAX_LINES + 50}))",
+    }
+    expression = expressions[kind]
+    expected = eval(expression, {"chr": chr, "range": range, "str": str})
+    if kind == "lines":
+        assert len(expected.encode("utf-8")) < DEFAULT_MAX_BYTES
+    result = _run(tool, expression)
+    assert result.status == "success", result.result
+    details = result.result["details"]
+    assert details["truncation"]["truncated"]
+    path = Path(details["full_output_path"])
+    assert path.parent == Path(tool.cwd)
+    assert path.read_text(encoding="utf-8") == expected
+    assert str(path) in result.result["output"]
+    assert "Full output: None" not in result.result["output"]
+
+
+def test_untruncated_boundary_does_not_create_a_log(tool):
+    expression = f"'\\n'.join('row-'+str(i) for i in range({DEFAULT_MAX_LINES}))"
+    result = _run(tool, expression)
+    assert result.status == "success", result.result
+    assert result.result["details"] is None
+    assert not list(Path(tool.cwd).glob("bash-*.log"))
+
+
+def test_failed_line_truncated_command_keeps_exit_status_and_full_log(tool):
+    expression = f"'\\n'.join('row-'+str(i) for i in range({DEFAULT_MAX_LINES + 1}))"
+    result = _run(tool, expression, exit_code=2)
+    assert result.status == "error", result.result
+    assert result.result["exit_code"] == 2
+    path = Path(result.result["details"]["full_output_path"])
+    assert path.read_text() == eval(expression, {"range": range, "str": str})
+    assert "Command exited with code 2" in result.result["output"]