Config Sample: Virtual Filesystem

Demonstrates running the Copilot agent with custom tool implementations backed by an in-memory store instead of the real filesystem. The agent doesn't know it's virtual — it sees create_file, read_file, and list_files tools that work normally, but zero bytes ever touch disk.

This pattern is the foundation for:

• WASM / browser agents where there's no real filesystem
• Cloud-hosted sandboxes where file ops go to object storage
• Multi-tenant platforms where each user gets isolated virtual storage
• Office add-ins where "files" are document sections in memory

How It Works

1. Disable all built-in tools with availableTools: []
2. Provide custom tools (create_file, read_file, list_files) whose handlers read/write a Map / dict / HashMap in the host process
3. Auto-approve permissions — no dialogs since the tools are entirely user-controlled
4. The agent uses the tools normally — it doesn't know they're virtual

What Each Sample Does

1. Creates a session with no built-in tools + 3 custom virtual FS tools
2. Sends: "Create a file called plan.md with a brief 3-item project plan for building a CLI tool. Then read it back and tell me what you wrote."
3. The agent calls create_file → writes to in-memory map
4. The agent calls read_file → reads from in-memory map
5. Prints the agent's response
6. Dumps the in-memory store to prove files exist only in memory

Configuration

Option	Value	Effect
availableTools	[] (empty)	Removes all built-in tools (bash, view, edit, create_file, grep, glob, etc.)
tools	[create_file, read_file, list_files]	Custom tools backed by in-memory storage
onPermissionRequest	Auto-approve	No permission dialogs
hooks.onPreToolUse	Auto-allow	No tool confirmation prompts

Key Insight

The integrator controls the tool layer. By replacing built-in tools with custom implementations, you can swap the backing store to anything — Map, Redis, S3, SQLite, IndexedDB — without the agent knowing or caring. The system prompt stays the same. The agent plans and operates normally.

Custom tools with the same name as a built-in automatically override the built-in — no need to explicitly exclude them. availableTools: [] removes all built-ins while keeping your custom tools available.

Run

./verify.sh

Requires the copilot binary (auto-detected or set COPILOT_CLI_PATH) and GITHUB_TOKEN.