feat: virtual file system by Tomas2D · Pull Request #2114 · i-am-bee/agentstack

Tomas2D · 2026-02-18T09:08:04Z

Summary

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Documentation

No Docs Needed:

If this PR adds new feature or changes existing. Make sure documentation is adjusted accordingly. If the docs is not needed, please explain why.

Signed-off-by: Tomas Dvorak <toomas2d@gmail.com>

gemini-code-assist · 2026-02-18T09:08:29Z

Summary of Changes

Hello @Tomas2D, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the AgentStack SDK by integrating an fsspec-compatible filesystem extension. This integration allows agents to interact with the AgentStack Files API using a unified and flexible interface, streamlining data access and manipulation. The changes encompass adding essential dependencies, implementing the core filesystem logic, and providing a clear demonstration agent to showcase its utility. This improvement aims to provide a more robust and developer-friendly experience for agents requiring file operations within the AgentStack ecosystem.

Highlights

New FileSystem Extension: Introduced a new FileSystemExtension in the AgentStack SDK to provide fsspec-compatible access to the AgentStack Files API, enabling standardized file operations.
Dependency Updates: Added fsspec as a core dependency across various AgentStack components to support the new filesystem capabilities. Also included numba, llvmlite, and numpy for the deepagents content builder.
New Example Agent: A new example agent named 'My Agent' was added to demonstrate the practical usage of the FileSystemExtensionServer for reading CSV files.
Tooling and Versioning Adjustments: Updated the SDK project version, replaced pyrefly with pyright for development dependencies, and adjusted linting configurations accordingly.

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Changelog

agents/deepagents_content_builder/pyproject.toml
- Added numba dependency.
agents/deepagents_content_builder/src/content_builder/agent.py
- Added a new example agent named "My Agent" demonstrating file system extension usage.
agents/deepagents_content_builder/uv.lock
- Added fsspec dependency.
- Added llvmlite dependency.
- Added numba dependency.
- Added numpy dependency.
apps/agentstack-cli/uv.lock
- Added fsspec dependency.
apps/agentstack-sdk-py/pyproject.toml
- Updated project version from 0.6.3 to 0.6.1.
- Removed typing-extensions, opentelemetry-instrumentation-httpx, and opentelemetry-instrumentation-openai dependencies.
- Added fsspec dependency.
- Replaced pyrefly with pyright in development dependencies.
- Updated linting ignore rule for F403 to reflect the use of Pyright.
- Replaced [tool.pyrefly] configuration with [tool.pyright] configuration.
apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/init.py
- Imported the new filesystem module.
apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/filesystem.py
- Added a new module implementing FileSystemExtensionSpec and FileSystemExtensionServer for fsspec-compatible access to AgentStack Files API.
apps/agentstack-sdk-py/tests/unit/test_filesystem_extension.py
- Added unit tests for the new FileSystemExtension.
apps/agentstack-sdk-py/uv.lock
- Added fsspec dependency.
apps/agentstack-server/uv.lock
- Added fsspec dependency.

Activity

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Code Review

The pull request introduces a Virtual File System (VFS) extension for AgentStack, enabling fsspec-compatible access to the Files API. While this is a valuable feature, it contains a high-severity path traversal vulnerability in the path normalization logic, allowing for bypassing the prefix restriction and potentially leading to unauthorized file access or modification. Furthermore, several code-related issues need addressing, such as a version regression in the SDK's pyproject.toml, missing imports and invalid method calls in the example agent, and potential performance bottlenecks in the VFS implementation due to eager file loading and inefficient async-to-sync bridging.

gemini-code-assist · 2026-02-18T09:10:48Z

apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/filesystem.py

+        path = path.lstrip("/")
+        return f"{self._prefix}/{path}" if self._prefix else path


The _normalize_path method is vulnerable to path traversal. It prepends a prefix to a user-supplied path but only strips leading slashes, failing to handle .. components. An attacker or a malicious LLM agent could use paths like ../../etc/passwd to escape the intended _prefix and access, modify, or delete unauthorized files in the AgentStack platform.

To fix this, use os.path.normpath to resolve relative path components and verify that the resulting path still starts with the allowed prefix.

Suggested change

path = path.lstrip("/")

return f"{self._prefix}/{path}" if self._prefix else path

import os

path = path.lstrip("/")

if not self._prefix:

return path

full_path = os.path.normpath(os.path.join(self._prefix, path))

if not full_path.startswith(self._prefix):

raise ValueError("Access denied: path is outside the allowed prefix")

return full_path

gemini-code-assist · 2026-02-18T09:10:48Z

apps/agentstack-sdk-py/pyproject.toml

 [project]
 name = "agentstack-sdk"
-version = "0.6.3"
+version = "0.6.1"


The version of agentstack-sdk is being downgraded from 0.6.3 to 0.6.1. This appears to be an accidental regression and should be corrected to reflect the next version.

gemini-code-assist · 2026-02-18T09:10:48Z

agents/deepagents_content_builder/src/content_builder/agent.py

+        df = pd.read_csv(f, sep="|", header=None)
+        yield df.text()


There are two issues in this snippet:

The pd alias is used but pandas is not imported in this file.

pandas.DataFrame does not have a text() method. You likely intended to use df.to_string() or access a specific column.

gemini-code-assist · 2026-02-18T09:10:48Z

apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/filesystem.py

+        self._platform = platform
+        self._agentstack_fs = fs  # Store reference for our use
+
+        data = self._load_content() if "r" in mode else None


The current implementation eagerly loads the entire file content into memory upon opening in read mode. For large files, this will lead to high memory consumption and potential MemoryError. Consider implementing lazy loading or a buffered reader by inheriting from fsspec.spec.AbstractBufferedFile instead of MemoryFile.

gemini-code-assist · 2026-02-18T09:10:48Z

apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/filesystem.py

+
+        async def _commit():
+            async with platform.use_client() as client:
+                ct = "text/plain" if self.path.endswith(".txt") else "text/csv" if self.path.endswith(".csv") else "application/json" if self.path.endswith(".json") else "application/octet-stream"


Hardcoding mimetypes based on a few extensions is fragile. It's better to use the standard mimetypes library to determine the content type dynamically.

Suggested change

ct = "text/plain" if self.path.endswith(".txt") else "text/csv" if self.path.endswith(".csv") else "application/json" if self.path.endswith(".json") else "application/octet-stream"

import mimetypes

ct, _ = mimetypes.guess_type(self.path)

ct = ct or "application/octet-stream"

gemini-code-assist · 2026-02-18T09:10:48Z

apps/agentstack-sdk-py/src/agentstack_sdk/a2a/extensions/services/filesystem.py

+        if loop and loop.is_running():
+            import concurrent.futures
+
+            with concurrent.futures.ThreadPoolExecutor() as executor:


Creating a new ThreadPoolExecutor for every synchronous call to an asynchronous operation is inefficient as it involves significant overhead for thread creation and teardown. Consider using a shared class-level or module-level executor to improve performance.

feat: wip

d335a94

Signed-off-by: Tomas Dvorak <toomas2d@gmail.com>

github-project-automation bot added this to Agent Stack Feb 18, 2026

Tomas2D marked this pull request as draft February 18, 2026 09:08

dosubot bot added the size:L This PR changes 100-499 lines, ignoring generated files. label Feb 18, 2026

Tomas2D changed the title ~~feat: wip~~ feat: virtual file system Feb 18, 2026

gemini-code-assist bot reviewed Feb 18, 2026

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feat: virtual file system#2114

feat: virtual file system#2114
Tomas2D wants to merge 1 commit intomainfrom
feat/virtual-fs-s3

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		path = path.lstrip("/")
		return f"{self._prefix}/{path}" if self._prefix else path

-        path = path.lstrip("/")
-        return f"{self._prefix}/{path}" if self._prefix else path
+        import os
+        path = path.lstrip("/")
+        if not self._prefix:
+            return path
+        full_path = os.path.normpath(os.path.join(self._prefix, path))
+        if not full_path.startswith(self._prefix):
+            raise ValueError("Access denied: path is outside the allowed prefix")
+        return full_path

-                ct = "text/plain" if self.path.endswith(".txt") else "text/csv" if self.path.endswith(".csv") else "application/json" if self.path.endswith(".json") else "application/octet-stream"
+                import mimetypes
+                ct, _ = mimetypes.guess_type(self.path)
+                ct = ct or "application/octet-stream"

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Tomas2D commented Feb 18, 2026

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