langchain - 💡(How to fix) Fix bug(langchain): glob_search returns files in arbitrary order despite docstring promising mtime-desc sort

Submission checklist

• This is a bug, not a usage question.
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• This is not related to the langchain-community package.
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Related Issues / PRs

No response

Reproduction Steps / Example Code (Python)

import os
import time
import tempfile
from pathlib import Path
from langchain.agents.middleware.file_search import FilesystemFileSearchMiddleware

with tempfile.TemporaryDirectory() as root:
    root_path = Path(root)
    # Create three files with monotonically increasing mtimes.
    for name in ["oldest.txt", "middle.txt", "newest.txt"]:
        p = root_path / name
        p.write_text("x")
        time.sleep(0.05)

    mw = FilesystemFileSearchMiddleware(root_path=root_path, allow_absolute_paths=True)
    glob_search = mw.tools[0]  # `glob_search` tool

    result = glob_search.invoke({"pattern": "*.txt"})
    print(result)
    # Docstring promises: most recently modified first ->
    #   newest.txt
    #   middle.txt
    #   oldest.txt
    # Actual order is whatever Path.glob() returns -> filesystem-dependent.

Error Message and Stack Trace (if applicable)

Description

The glob_search tool exposed by FilesystemFileSearchMiddleware documents that it "returns matching file paths sorted by modification time (most recently modified first)".

Internally it does call match.stat() for every match and builds a list of (virtual_path, modified_at_iso) tuples — but it never sorts that list before joining. The result order is whatever Path.glob() yields, which is OS- and filesystem-dependent.

Two consequences:

1. Callers (and the LLM driving the tool) rely on the documented ordering to decide which files to inspect first. The current behavior silently breaks that contract.
2. The stat() calls and datetime.fromtimestamp(...) conversions are pure overhead — their output is computed and immediately discarded.

Fix: sort matching by the ISO timestamp (descending) before extracting the paths.

System Info

System Information

OS: Linux OS Version: #29~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Jun 26 14:16:59 UTC 2 Python Version: 3.12.3 (main, Mar 23 2026, 19:04:32) [GCC 13.3.0]

Package Information

langchain_core: 1.4.0 langchain: 1.3.0 langsmith: 0.8.3 langchain_protocol: 0.0.15 langgraph_sdk: 0.3.14

Optional packages not installed

deepagents deepagents-cli

Other Dependencies

httpx: 0.28.1 jsonpatch: 1.33 langgraph: 1.2.0 orjson: 3.11.9 packaging: 26.2 pydantic: 2.13.4 pyyaml: 6.0.3 requests: 2.34.0 requests-toolbelt: 1.0.0 tenacity: 9.1.4 typing-extensions: 4.15.0 uuid-utils: 0.15.0 xxhash: 3.7.0 zstandard: 0.25.0