_drain_remaining_stderr() — langchain Function Reference

Architecture documentation for the _drain_remaining_stderr() function in shell_tool.py from the langchain codebase.

Function python LangChainCore MessageInterface called by 1

Entity Profile

LangChainCore→ MessageInterface→ _drain_remaining_stderr() — langchain Function Reference

Dependency Diagram

graph TD
  2c92ef14_d880_f149_5132_20d7d028b5b7["_drain_remaining_stderr()"]
  cf4eeaa4_4bcc_69d9_a0f3_664b1eecb4e8["ShellSession"]
  2c92ef14_d880_f149_5132_20d7d028b5b7 -->|defined in| cf4eeaa4_4bcc_69d9_a0f3_664b1eecb4e8
  89d586a2_0b74_ac5c_97da_a6a18a02f59d["_collect_output()"]
  89d586a2_0b74_ac5c_97da_a6a18a02f59d -->|calls| 2c92ef14_d880_f149_5132_20d7d028b5b7
  style 2c92ef14_d880_f149_5132_20d7d028b5b7 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/langchain_v1/langchain/agents/middleware/shell_tool.py lines 424–453

    def _drain_remaining_stderr(
        self, collected: list[str], deadline: float, drain_timeout: float = 0.05
    ) -> None:
        """Drain any stderr output that arrived concurrently with the done marker.

        The stdout and stderr reader threads run independently. When a command writes to
        stderr just before exiting, the stderr output may still be in transit when the
        done marker arrives on stdout. This method briefly polls the queue to capture
        such output.

        Args:
            collected: The list to append collected stderr lines to.
            deadline: The original command deadline (used as an upper bound).
            drain_timeout: Maximum time to wait for additional stderr output.
        """
        drain_deadline = min(time.monotonic() + drain_timeout, deadline)
        while True:
            remaining = drain_deadline - time.monotonic()
            if remaining <= 0:
                break
            try:
                source, data = self._queue.get(timeout=remaining)
            except queue.Empty:
                break
            if data is None or source != "stderr":
                continue
            stripped = data.rstrip("\n")
            collected.append(f"[stderr] {stripped}")
            if data.endswith("\n"):
                collected.append("\n")