ContextFS is a library that lets you construct a virtual filesystem using a router-style API. It's mountable via NFS or `just-bash`, and useful for providing agents with hierarchical, explorable context defined in code.

  // Define file system structure
  const vfs = createFileSystem({
    issues: {
      ":id": {
        [list]: () => getIssues().map(i => ({ id: i.id })),
        [read]: (c) => getIssue(c.params.id).body,
      }
    }
  });

  // Mount with NFS
  await mount(vfs, { mountPoint: "/tmp/issues" });
  await fsp.readFile("/tmp/issues/123");

  // Explore with just-bash
  const env = new Bash({ fs: new ContextFS(vfs) });
  await env.exec("ls /tmp/issues");

Key features: - Express-style dynamic paths (:id, :slug.md) with full TypeScript inference - Read and optional write support - Symlinks to represent relationships - Browser-safe core library - Pure TypeScript NFS v3 implementation, no native deps