chore: import upstream snapshot with attribution

examples/python/runtimes/microsandbox/README.md

@@ -0,0 +1,84 @@
+# Microsandbox + Mirage FUSE
+
+Run an untrusted [Microsandbox](https://microsandbox.dev) microVM that reads S3
+through a host-side Mirage FUSE mount. Mirage FUSE-mounts S3 on the **host**;
+Microsandbox bind-mounts that path into the microVM over virtio-fs. The guest
+reads `/s3` natively, with no S3 credentials and no network of its own.
+
+## How it works
+
+```
+microVM guest  --virtio-fs /s3-->  host FUSE mountpoint  -->  Mirage  -->  S3
+ (msb / libkrun)                       (fuse3)
+```
+
+1. `microsandbox_fuse.py` (host) FUSE-mounts an `S3Resource` at a temp mountpoint.
+1. It boots a microVM with `Volume.bind(<mountpoint>, readonly=True)` mapped to
+   `/s3`, so the guest's `/s3` is backed by the host FUSE mount over virtio-fs.
+1. `remote/guest.py` runs inside the microVM: it `os.listdir('/s3')` and reads
+   `/s3/data/example.jsonl` as if they were local files.
+
+The microVM guest has no `/dev/fuse`, so Mirage can't run in the guest; the host
+mount is shared in instead.
+
+## Prerequisites
+
+- **Microsandbox Python SDK**: `uv pip install microsandbox` (tested with 0.5.10).
+- **`msb` runtime** (provides libkrunfw): `curl -sSfL https://get.microsandbox.dev | sh`.
+  On Apple Silicon this also pulls the libkrun HVF backend; x86_64 macOS is not
+  supported by Microsandbox.
+- **Host FUSE**: Linux `fuse3` (see platform note below for macOS).
+- **AWS credentials** in `.env.development` at the repo root:
+  `AWS_S3_BUCKET`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, and optionally
+  `AWS_DEFAULT_REGION`.
+- The bucket must contain `data/example.jsonl` (any text/JSONL file works; the
+  guest just counts lines containing `mirage`).
+
+The SDK 0.5.10 embeds the runtime in-process, so there is **no separate `msb server` to start** (just run the example).
+
+## Run
+
+From the repo root (so `.env.development` loads):
+
+```bash
+./python/.venv/bin/python examples/python/runtimes/microsandbox/microsandbox_fuse.py
+```
+
+Expected tail:
+
+```
+=== guest output ===
+--- os.listdir('/s3') ---
+  data
+  ...
+--- read /s3/data/example.jsonl through virtio-fs -> FUSE -> Mirage -> S3 ---
+  5766 lines, 5678 containing 'mirage'
+
+Mirage served N ops, ... bytes to the sandbox
+```
+
+## Platform note: Linux only
+
+This example runs on **Linux**. On **macOS it does not work**: libkrun's virtio-fs
+cannot re-export a macFUSE-backed directory into the microVM. Booting the VM
+fails at the bind-mount with:
+
+```
+failed to start "mirage-fuse": mount s3_<hash>: Operation not permitted (os error 1)
+```
+
+This is a libkrun + macFUSE interaction, not a Mirage or Microsandbox bug:
+
+- It reproduces with both S3-backed and RAM-backed FUSE mounts (the trigger is the
+  macFUSE filesystem type, not the backend).
+- A plain (non-FUSE) host directory bind-mounts and reads fine inside the same
+  microVM, so virtio-fs itself works on macOS.
+- Mounting the FUSE filesystem with `allow_other` does not help; the failure is
+  `EPERM` (not `EACCES`), from a macOS-specific VFS operation libkrun's host-side
+  virtio-fs server issues during share setup that macFUSE rejects.
+
+On macOS, use the sibling [`wasmer`](../wasmer/README.md) example instead: it maps
+the same host FUSE mount into a WASIX guest with `--mapdir` and works on macOS.
+
+Not run in CI. It needs the Microsandbox runtime, host FUSE, and live AWS
+credentials.

examples/python/runtimes/microsandbox/microsandbox_fuse.py

@@ -0,0 +1,85 @@
+# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
+
+# The microVM guest has no /dev/fuse, so Mirage FUSE-mounts S3 on the HOST and
+# Microsandbox bind-mounts that path in over virtio-fs. The guest reads it
+# natively, with no S3 credentials and no network of its own.
+# Requires a running Microsandbox server (`msb server start`), host FUSE
+# (Linux fuse3 or macOS macFUSE), and AWS creds in .env.development.
+
+import asyncio
+import os
+import sys
+from pathlib import Path
+
+from dotenv import load_dotenv
+from microsandbox import Sandbox, Volume
+
+from mirage import Mount, MountMode, Workspace
+from mirage.resource.s3 import S3Config, S3Resource
+
+load_dotenv(".env.development")
+
+REMOTE_DIR = Path(__file__).parent / "remote"
+
+
+def s3_config() -> S3Config:
+    return S3Config(
+        bucket=os.environ["AWS_S3_BUCKET"],
+        region=os.environ.get("AWS_DEFAULT_REGION", "us-east-1"),
+        aws_access_key_id=os.environ["AWS_ACCESS_KEY_ID"],
+        aws_secret_access_key=os.environ["AWS_SECRET_ACCESS_KEY"],
+    )
+
+
+async def main():
+    print("=== Mirage FUSE-mounting S3 on the host ===")
+    with Workspace({
+            "/s3/":
+            Mount(S3Resource(s3_config()), mode=MountMode.READ, fuse=True)
+    }) as ws:
+        host_s3 = ws.fuse_mountpoint
+        print(f"  host mountpoint: {host_s3}")
+
+        print(
+            "\n=== booting microVM (S3 mount bind-mounted in, no network) ===")
+        async with await Sandbox.create(
+                "mirage-fuse",
+                image="python",
+                memory=1024,
+                cpus=1,
+                volumes={
+                    "/s3": Volume.bind(host_s3, readonly=True),
+                    "/prog": Volume.bind(str(REMOTE_DIR), readonly=True),
+                },
+                replace=True,
+        ) as sandbox:
+            result = await sandbox.exec("python", ["/prog/guest.py"])
+            print("=== guest output ===")
+            print(result.stdout_text.rstrip())
+            if result.exit_code != 0:
+                print(result.stderr_text, file=sys.stderr)
+                print(f"\n=== exit code: {result.exit_code} ===",
+                      file=sys.stderr)
+                sys.exit(result.exit_code)
+
+        records = ws.ops.records
+        total = sum(rec.bytes for rec in records)
+        print(
+            f"\nMirage served {len(records)} ops, {total} bytes to the sandbox"
+        )
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

examples/python/runtimes/microsandbox/remote/guest.py

@@ -0,0 +1,33 @@
+# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ========= Copyright 2026 @ Strukto.AI All Rights Reserved. =========
+
+# Runs inside a Microsandbox microVM (invoked by ../microsandbox_fuse.py).
+# /s3 is a host directory that Mirage FUSE-mounted from S3, bind-mounted in
+# via virtio-fs. No S3 credentials or network reach this guest.
+
+import os
+
+print("--- os.listdir('/s3') ---")
+for entry in sorted(os.listdir("/s3")):
+    print(f"  {entry}")
+
+path = "/s3/data/example.jsonl"
+print(f"\n--- read {path} through virtio-fs -> FUSE -> Mirage -> S3 ---")
+with open(path) as f:
+    lines = f.readlines()
+hits = sum(1 for line in lines if "mirage" in line)
+print(f"  {len(lines)} lines, {hits} containing 'mirage'")
+print("  head:")
+for line in lines[:3]:
+    print(f"    {line.rstrip()}")