diff --git a/Cargo.lock b/Cargo.lock
index 450e0be..7a8dab2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -164,6 +164,12 @@ version = "0.21.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
 
+[[package]]
+name = "base64ct"
+version = "1.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -430,6 +436,12 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "const-oid"
+version = "0.9.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2459377285ad874054d797f3ccebf984978aa39129f6eafde5cdc8315b612f8"
+
 [[package]]
 name = "core-foundation"
 version = "0.9.4"
@@ -664,6 +676,33 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
+[[package]]
+name = "curve25519-dalek"
+version = "4.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "97fb8b7c4503de7d6ae7b42ab72a5a59857b4c937ec27a3d4539dba95b5ab2be"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "curve25519-dalek-derive",
+ "digest",
+ "fiat-crypto",
+ "rustc_version",
+ "subtle",
+ "zeroize",
+]
+
+[[package]]
+name = "curve25519-dalek-derive"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f46882e17999c6cc590af592290432be3bce0428cb0d5f8b6715e4dc7b383eb3"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "data-encoding"
 version = "2.10.0"
@@ -679,6 +718,16 @@ dependencies = [
  "uuid",
 ]
 
+[[package]]
+name = "der"
+version = "0.7.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e7c1832837b905bbfb5101e07cc24c8deddf52f93225eee6ead5f4d63d53ddcb"
+dependencies = [
+ "const-oid",
+ "zeroize",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -809,6 +858,31 @@ dependencies = [
  "linux-raw-sys 0.9.4",
 ]
 
+[[package]]
+name = "ed25519"
+version = "2.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "115531babc129696a58c64a4fef0a8bf9e9698629fb97e9e40767d235cfbcd53"
+dependencies = [
+ "pkcs8",
+ "signature",
+]
+
+[[package]]
+name = "ed25519-dalek"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70e796c081cee67dc755e1a36a0a172b897fab85fc3f6bc48307991f64e4eca9"
+dependencies = [
+ "curve25519-dalek",
+ "ed25519",
+ "rand_core 0.6.4",
+ "serde",
+ "sha2",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "either"
 version = "1.15.0"
@@ -875,6 +949,23 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "fiat-crypto"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28dea519a9695b9977216879a3ebfddf92f1c08c05d984f8996aecd6ecdc811d"
+
+[[package]]
+name = "filetime"
+version = "0.2.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f98844151eee8917efc50bd9e8318cb963ae8b297431495d3f758616ea5c57db"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "libredox",
+]
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.9"
@@ -1153,6 +1244,12 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc0fef456e4baa96da950455cd02c081ca953b141298e41db3fc7e36b1da849c"
 
+[[package]]
+name = "hex"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
+
 [[package]]
 name = "http"
 version = "1.4.0"
@@ -2009,6 +2106,16 @@ version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a89322df9ebe1c1578d689c92318e070967d1042b512afbe49518723f4e6d5cd"
 
+[[package]]
+name = "pkcs8"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f950b2377845cebe5cf8b5165cb3cc1a5e0fa5cfa3e1f7f55707d8fd82e0a7b7"
+dependencies = [
+ "der",
+ "spki",
+]
+
 [[package]]
 name = "pkg-config"
 version = "0.3.32"
@@ -2339,6 +2446,15 @@ version = "2.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "357703d41365b4b27c590e3ed91eabb1b663f07c4c084095e60cbed4362dff0d"
 
+[[package]]
+name = "rustc_version"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfcb3a22ef46e85b45de6ee7e79d063319ebb6594faafcf1c225ea92ab6e9b92"
+dependencies = [
+ "semver",
+]
+
 [[package]]
 name = "rustix"
 version = "0.38.44"
@@ -2405,6 +2521,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "seccompiler"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "345a3e4dddf721a478089d4697b83c6c0a8f5bf16086f6c13397e4534eb6e2e5"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "semver"
 version = "1.0.27"
@@ -2532,6 +2657,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "signature"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
+dependencies = [
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -2650,6 +2784,16 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "spki"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d91ed6c858b01f942cd56b37a94b3e0a1798290327d1236e4d9cf4eaca44d29d"
+dependencies = [
+ "base64ct",
+ "der",
+]
+
 [[package]]
 name = "sptr"
 version = "0.3.2"
@@ -2662,6 +2806,12 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
 
+[[package]]
+name = "subtle"
+version = "2.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
+
 [[package]]
 name = "syn"
 version = "2.0.117"
@@ -2713,6 +2863,17 @@ dependencies = [
  "winx",
 ]
 
+[[package]]
+name = "tar"
+version = "0.4.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d863878d212c87a19c1a610eb53bb01fe12951c0501cf5a0d65f724914a667a"
+dependencies = [
+ "filetime",
+ "libc",
+ "xattr",
+]
+
 [[package]]
 name = "target-lexicon"
 version = "0.13.3"
@@ -3821,6 +3982,7 @@ dependencies = [
  "toml 0.8.23",
  "tracing",
  "tracing-subscriber",
+ "weft-ipc-types",
 ]
 
 [[package]]
@@ -3841,6 +4003,22 @@ dependencies = [
  "wayland-backend",
  "wayland-scanner",
  "wayland-server",
+ "weft-ipc-types",
+]
+
+[[package]]
+name = "weft-ipc-types"
+version = "0.1.0"
+dependencies = [
+ "rmp-serde",
+ "serde",
+]
+
+[[package]]
+name = "weft-mount-helper"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
 ]
 
 [[package]]
@@ -3848,8 +4026,14 @@ name = "weft-pack"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "ed25519-dalek",
+ "hex",
+ "rand 0.8.5",
  "serde",
+ "sha2",
+ "tar",
  "toml 0.8.23",
+ "zstd",
 ]
 
 [[package]]
@@ -3857,6 +4041,9 @@ name = "weft-runtime"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "cap-std",
+ "libc",
+ "seccompiler",
  "tracing",
  "tracing-subscriber",
  "wasmtime",
@@ -4475,6 +4662,16 @@ version = "0.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea6fc2961e4ef194dcbfe56bb845534d0dc8098940c7e5c012a258bfec6701bd"
 
+[[package]]
+name = "xattr"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32e45ad4206f6d2479085147f02bc2ef834ac85886624a23575ae137c8aa8156"
+dependencies = [
+ "libc",
+ "rustix 1.1.4",
+]
+
 [[package]]
 name = "xcursor"
 version = "0.3.10"
@@ -4581,6 +4778,12 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "zeroize"
+version = "1.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+
 [[package]]
 name = "zerotrie"
 version = "0.2.3"
diff --git a/Cargo.toml b/Cargo.toml
index ef21caa..e6e17e2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,7 @@ members = [
     "crates/weft-build-meta",
     "crates/weft-compositor",
     "crates/weft-ipc-types",
+    "crates/weft-mount-helper",
     "crates/weft-pack",
     "crates/weft-runtime",
     "crates/weft-servo-shell",
diff --git a/crates/weft-ipc-types/src/lib.rs b/crates/weft-ipc-types/src/lib.rs
index 5b2e604..753ef2b 100644
--- a/crates/weft-ipc-types/src/lib.rs
+++ b/crates/weft-ipc-types/src/lib.rs
@@ -83,7 +83,10 @@ impl std::fmt::Display for FrameDecodeError {
             Self::TooShort => write!(f, "frame buffer shorter than 4-byte header"),
             Self::TooLong(n) => write!(f, "frame length {n} exceeds MAX_FRAME_LEN"),
             Self::LengthMismatch { declared, actual } => {
-                write!(f, "declared length {declared} != actual body length {actual}")
+                write!(
+                    f,
+                    "declared length {declared} != actual body length {actual}"
+                )
             }
             Self::Deserialize(e) => write!(f, "MessagePack deserialize error: {e}"),
         }
@@ -113,7 +116,11 @@ mod tests {
         let frame = frame_encode(&msg).unwrap();
         let decoded: AppdToCompositor = frame_decode(&frame).unwrap();
         match decoded {
-            AppdToCompositor::AppSurfaceCreated { app_id, session_id, pid } => {
+            AppdToCompositor::AppSurfaceCreated {
+                app_id,
+                session_id,
+                pid,
+            } => {
                 assert_eq!(app_id, "com.example.app");
                 assert_eq!(session_id, 42);
                 assert_eq!(pid, 1234);
@@ -184,6 +191,9 @@ mod tests {
         frame[2] = bad_len[2];
         frame[3] = bad_len[3];
         let result: Result<AppdToCompositor, _> = frame_decode(&frame);
-        assert!(matches!(result, Err(FrameDecodeError::LengthMismatch { .. })));
+        assert!(matches!(
+            result,
+            Err(FrameDecodeError::LengthMismatch { .. })
+        ));
     }
 }
diff --git a/crates/weft-mount-helper/Cargo.toml b/crates/weft-mount-helper/Cargo.toml
new file mode 100644
index 0000000..f8b9946
--- /dev/null
+++ b/crates/weft-mount-helper/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "weft-mount-helper"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+
+[[bin]]
+name = "weft-mount-helper"
+path = "src/main.rs"
+
+[dependencies]
+anyhow = "1.0"
diff --git a/crates/weft-mount-helper/src/main.rs b/crates/weft-mount-helper/src/main.rs
new file mode 100644
index 0000000..a17a914
--- /dev/null
+++ b/crates/weft-mount-helper/src/main.rs
@@ -0,0 +1,162 @@
+use std::path::Path;
+
+use anyhow::Context;
+
+fn main() -> anyhow::Result<()> {
+    let args: Vec<String> = std::env::args().collect();
+    match args.get(1).map(String::as_str) {
+        Some("mount") => {
+            let img = args.get(2).context(
+                "usage: weft-mount-helper mount <img> <hash_dev> <root_hash> <mountpoint>",
+            )?;
+            let hash_dev = args.get(3).context("missing <hash_dev>")?;
+            let root_hash = args.get(4).context("missing <root_hash>")?;
+            let mountpoint = args.get(5).context("missing <mountpoint>")?;
+            cmd_mount(
+                Path::new(img),
+                Path::new(hash_dev),
+                root_hash,
+                Path::new(mountpoint),
+            )?;
+        }
+        Some("umount") => {
+            let mountpoint = args
+                .get(2)
+                .context("usage: weft-mount-helper umount <mountpoint>")?;
+            cmd_umount(Path::new(mountpoint))?;
+        }
+        _ => {
+            eprintln!("usage:");
+            eprintln!("  weft-mount-helper mount <img> <hash_dev> <root_hash> <mountpoint>");
+            eprintln!("  weft-mount-helper umount <mountpoint>");
+            std::process::exit(1);
+        }
+    }
+    Ok(())
+}
+
+fn effective_uid() -> Option<u32> {
+    let status = std::fs::read_to_string("/proc/self/status").ok()?;
+    status
+        .lines()
+        .find(|l| l.starts_with("Uid:"))
+        .and_then(|l| l.split_whitespace().nth(2))
+        .and_then(|s| s.parse().ok())
+}
+
+fn require_root() -> anyhow::Result<()> {
+    match effective_uid() {
+        Some(0) => Ok(()),
+        Some(uid) => anyhow::bail!("weft-mount-helper must run as root (euid={uid})"),
+        None => {
+            anyhow::bail!("weft-mount-helper must run as root (could not read /proc/self/status)")
+        }
+    }
+}
+
+fn device_name(mountpoint: &Path) -> String {
+    let s = mountpoint.to_string_lossy();
+    let sanitized: String = s
+        .chars()
+        .map(|c| if c.is_ascii_alphanumeric() { c } else { '-' })
+        .collect();
+    let suffix: String = sanitized
+        .trim_matches('-')
+        .chars()
+        .take(26)
+        .collect::<String>()
+        .trim_end_matches('-')
+        .to_string();
+    format!("weft-{suffix}")
+}
+
+fn cmd_mount(
+    img: &Path,
+    hash_dev: &Path,
+    root_hash: &str,
+    mountpoint: &Path,
+) -> anyhow::Result<()> {
+    require_root()?;
+    let dev_name = device_name(mountpoint);
+
+    let status = std::process::Command::new("veritysetup")
+        .args([
+            "open",
+            &img.to_string_lossy(),
+            &dev_name,
+            &hash_dev.to_string_lossy(),
+            root_hash,
+        ])
+        .status()
+        .context("spawn veritysetup; ensure cryptsetup-bin is installed")?;
+    if !status.success() {
+        anyhow::bail!("veritysetup open failed with status {status}");
+    }
+
+    let mapper_dev = format!("/dev/mapper/{dev_name}");
+    let status = std::process::Command::new("mount")
+        .args([
+            "-t",
+            "erofs",
+            "-o",
+            "ro",
+            &mapper_dev,
+            &mountpoint.to_string_lossy(),
+        ])
+        .status()
+        .context("spawn mount")?;
+    if !status.success() {
+        let _ = std::process::Command::new("veritysetup")
+            .args(["close", &dev_name])
+            .status();
+        anyhow::bail!("mount failed with status {status}");
+    }
+
+    eprintln!("mounted: {} -> {}", img.display(), mountpoint.display());
+    Ok(())
+}
+
+fn cmd_umount(mountpoint: &Path) -> anyhow::Result<()> {
+    require_root()?;
+    let dev_name = device_name(mountpoint);
+
+    let status = std::process::Command::new("umount")
+        .arg(mountpoint)
+        .status()
+        .context("spawn umount")?;
+    if !status.success() {
+        anyhow::bail!("umount failed with status {status}");
+    }
+
+    let status = std::process::Command::new("veritysetup")
+        .args(["close", &dev_name])
+        .status()
+        .context("spawn veritysetup close; ensure cryptsetup-bin is installed")?;
+    if !status.success() {
+        anyhow::bail!("veritysetup close failed with status {status}");
+    }
+
+    eprintln!("unmounted: {}", mountpoint.display());
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn device_name_sanitizes_path() {
+        let mp = Path::new("/run/weft/mounts/com.example.myapp");
+        let name = device_name(mp);
+        assert!(name.starts_with("weft-"));
+        assert!(name.chars().all(|c| c.is_ascii_alphanumeric() || c == '-'));
+        assert!(name.len() <= 31);
+    }
+
+    #[test]
+    fn device_name_truncates_long_paths() {
+        let mp = Path::new("/run/weft/mounts/com.example.averylongappidthatexceedsthemaximum");
+        let name = device_name(mp);
+        assert!(name.len() <= 31);
+    }
+}
diff --git a/crates/weft-pack/src/main.rs b/crates/weft-pack/src/main.rs
index c6ad57f..c8f164b 100644
--- a/crates/weft-pack/src/main.rs
+++ b/crates/weft-pack/src/main.rs
@@ -127,7 +127,9 @@ fn main() -> anyhow::Result<()> {
             eprintln!("  weft-pack install      <dir>             install package to app store");
             eprintln!("  weft-pack uninstall    <app_id>          remove installed package");
             eprintln!("  weft-pack list                           list installed packages");
-            eprintln!("  weft-pack build-image   <dir> [--out <img>] create EROFS image with mkfs.erofs");
+            eprintln!(
+                "  weft-pack build-image   <dir> [--out <img>] create EROFS image with mkfs.erofs"
+            );
             eprintln!("  weft-pack build-verity   <img> [--out <hash>] add dm-verity hash tree");
             eprintln!("  weft-pack bundle        <dir> [--out <dir>] create .app.tar.zst archive");
             eprintln!("  weft-pack unbundle      <archive> [--out <dir>] extract .app.tar.zst");
@@ -406,7 +408,11 @@ fn build_verity(img: &Path, hash_out: Option<&Path>) -> anyhow::Result<()> {
         anyhow::bail!("{} already exists", hash_path.display());
     }
     let output = std::process::Command::new("veritysetup")
-        .args(["format", &img.to_string_lossy(), &hash_path.to_string_lossy()])
+        .args([
+            "format",
+            &img.to_string_lossy(),
+            &hash_path.to_string_lossy(),
+        ])
         .output()
         .context("spawn veritysetup; ensure cryptsetup-bin is installed")?;
     if !output.status.success() {
diff --git a/scripts/wsl-test.sh b/scripts/wsl-test.sh
index 8262efc..fc8c1a4 100644
--- a/scripts/wsl-test.sh
+++ b/scripts/wsl-test.sh
@@ -38,5 +38,9 @@ echo ""
 echo "==> cargo test -p weft-pack"
 cargo test -p weft-pack -- --test-threads=1 2>&1
 
+echo ""
+echo "==> cargo test -p weft-mount-helper"
+cargo test -p weft-mount-helper -- --test-threads=1 2>&1
+
 echo ""
 echo "ALL DONE"