@@ -16,6 +16,7 @@ path = "src/main.rs"
 
 [dependencies]
 openshell-core = { path = "../openshell-core", default-features = false, features = ["driver-extraction"] }
+openshell-isolation-interface = { path = "../openshell-isolation-interface" }
 openshell-otel = { path = "../openshell-otel" }
 
 opentelemetry = { workspace = true }
@@ -38,15 +39,17 @@ miette = { workspace = true }
 toml = { workspace = true }
 tower-http = { workspace = true }
 http = { workspace = true }
+rand = { workspace = true }
+sha2 = { workspace = true }
+tar = "0.4"
+tempfile = "3"
 
 [dev-dependencies]
 openshell-otel-test-support = { path = "../openshell-otel-test-support" }
 opentelemetry = { workspace = true }
 opentelemetry_sdk = { workspace = true, features = ["testing"] }
 prost-types = { workspace = true }
-tar = "0.4"
 temp-env = "0.3"
-tempfile = "3"
 tracing-subscriber = { workspace = true }
 
 [lints]
 
@@ -29,18 +29,31 @@ no candidate responds.
 
 ## Runtime Model
 
-The gateway runs as a host process. The Docker driver creates one container per
-sandbox and starts the `openshell-sandbox` supervisor inside that container. The
-supervisor then creates the nested sandbox namespace for the agent process.
+The gateway and Docker driver run on the host. For each sandbox, the driver
+starts `openshell-sandbox --mode=control` beside the gateway and
+`openshell-sandbox --mode=boundary` as PID 1 in the workload container. The two
+roles use the shared RFC 0012 protocol over a private bind-mounted Unix socket.
+
+Control owns the gateway session, policy, SSH relay, and network proxy. The
+boundary owns the process tree, exec/signal/wait/PTY operations, loopback port
+forwarding, procfs binary identity, and the workload network namespace. The
+boundary receives no gateway JWT, client TLS private key, or policy authority.
+
+The driver bind-mounts the boundary socket from a short, digest-keyed runtime
+directory under `/tmp/openshell-docker-boundaries`. This keeps the host endpoint
+below Linux's Unix-socket path limit even when the gateway state directory is
+deeply nested. The full protected topology and gateway material remain in the
+normal driver state directory, and sandbox cleanup removes both locations.
 
 ## Stop and Start
 
-Stop stops the managed container without removing it. Docker retains the
-container writable layer, attached volumes, labels, token material, and restart
-policy. Start starts that same container, so files in the resolved OCI
-workspace remain available. A durably stopped sandbox is excluded from
-gateway startup recovery and stays stopped across gateway restarts. Delete
-continues to force-remove the container and clean up driver-owned material.
+Stop terminates host control and stops the managed container without removing
+it. Docker retains the container writable layer, attached volumes, labels, and
+the protected driver topology. Start starts that same container and recreates
+host control, so files in the resolved OCI workspace remain available. A
+durably stopped sandbox is excluded from gateway startup recovery and stays
+stopped across gateway restarts. Delete force-removes the container and the
+driver-owned boundary directory.
 Graceful gateway shutdown sends `StopSandbox` for each sandbox whose persisted
 phase requires running compute without changing that persisted intent. On
 startup, the gateway sends an idempotent `StartSandbox` request for the same
@@ -50,9 +63,9 @@ remain excluded.
 Before creating the container, the driver inspects the final sandbox image and
 captures its immutable image ID, raw OCI `Config.User`, and OCI
 `Config.WorkingDir`. Container creation uses that image ID, preventing a
-mutable tag from changing between inspection and launch. The supervisor runs as
-root, resolves omitted policy identity fields from the image declaration, and
-drops only agent children to the resulting identity. Named OCI components
+mutable tag from changing between inspection and launch. The boundary runs as
+root, resolves omitted policy identity fields from the image declaration inside
+the image filesystem, and drops only agent children to the resulting identity. Named OCI components
 remain names after validation; a missing group is filled with the user's
 numeric primary GID. Explicit `process.run_as_user` and
 `process.run_as_group` values take precedence independently.
@@ -83,14 +96,12 @@ are rejected, as are paths that overlap concrete OpenShell control resources.
 The workspace is the child cwd and `HOME`. The supervisor starts from `/`, then
 reports an invalid workdir as a readiness failure.
 
-Docker containers join an OpenShell-managed bridge network. The driver injects
-`host.openshell.internal` and `host.docker.internal` so supervisors have stable
-names for reaching the gateway host. On Docker Desktop, Colima, Rancher
-Desktop, OrbStack, and macOS-hosted gateways, those names use Docker's
-`host-gateway` alias. The driver requests a separate IPv4 loopback callback
-listener when the primary listener does not already cover it. On native Linux
-Docker, the gateway also binds the bridge gateway IP so containers can call
-back to the host process.
+Boundary containers use Docker `network_mode=none`. The nested agent network
+namespace can reach only the boundary's mediation listener. Each accepted TCP
+stream and its procfs-derived executable identity cross the private Unix socket
+to host control, which applies policy before dialing the destination. Host
+control reaches the gateway directly; the existing managed bridge listener is
+retained for compatibility with legacy containers created before this split.
 
 ## Container Contract
 
@@ -100,13 +111,15 @@ contract:
 | Setting | Purpose |
 |---|---|
 | `user = "0"` | The supervisor needs root inside the container to prepare namespaces, mounts, Landlock, and seccomp. |
-| `network_mode = openshell` | Places the supervisor on the managed Docker bridge network. |
+| `network_mode = none` | Removes direct container egress; the nested workload namespace can emit only through the authenticated boundary stream. |
 | `cap_add` | Grants supervisor-only capabilities required for namespace setup and process inspection. |
 | `apparmor=unconfined` | Avoids Docker's default profile blocking required mount operations. |
 | `restart_policy = no` | A canonical main-process exit remains terminal and is not silently restarted by Docker. |
 | `PidsLimit` | Enforces the sandbox PID budget at the Docker cgroup layer. Set `[openshell.drivers.docker].sandbox_pids_limit = 0` to inherit the Docker/runtime default. |
 | CDI GPU request | Uses opaque `driver_config.cdi_devices` values when set; otherwise selects the requested count of NVIDIA CDI GPUs in round-robin order when daemon CDI support is detected. Docker daemon `/info` can permit `nvidia.com/gpu=all` as a WSL2 all-only compatibility fallback, where it counts as one selectable device. Exact CDI device lists must not contain duplicates and must match the effective GPU count. |
-| `policy-dns-transparent-tcp` capability | Declares that the combined Docker supervisor can own namespace-local DNS/TCP capture and coupled workload restart. The shared supervisor still owns DNS eligibility, mappings, authorization, pinned dialing, relaying, and OCSF decisions. The marker is stripped from the workload environment. |
+| Read-only supervisor/runtime mounts | Supplies the boundary binary and trusted `ip`/`nft` helper runtime without trusting workload-image tools. |
+| Private boundary bind mount | Carries the protected boundary config and Unix control socket. The directory is host-owned mode `0700`; workload children cannot access it. |
+| `policy-dns-transparent-tcp` capability | Declares that the shared boundary can own namespace-local DNS/TCP capture while host control retains authorization, pinned dialing, relaying, and OCSF decisions. The marker is not exposed to the workload environment. |
 
 The agent child process does not retain these supervisor privileges.
 
@@ -127,8 +140,9 @@ mount types:
 
 Host bind mounts are disabled by default because they expose gateway host
 paths to sandbox requests. Image mounts are not part of the Docker
-driver-config schema. The driver still uses internal bind mounts for
-OpenShell-owned supervisor, token, and TLS material.
+driver-config schema. The driver still uses internal bind mounts for the
+OpenShell-owned boundary binary, trusted helper runtime, and private socket
+directory. Gateway token and TLS material remain on the host.
 
 Docker `bind` mounts accept `source`, `target`, optional `read_only`, and an
 optional `selinux_label` of `shared` (applies `:z`) or `private` (applies
@@ -154,8 +168,9 @@ openshell sandbox create \
 
 ## Supervisor Binary Resolution
 
-The Docker driver bind-mounts a host-side Linux `openshell-sandbox` binary into
-each sandbox container. Resolution order is:
+The Docker driver bind-mounts a host-side Linux `openshell-sandbox` boundary
+binary and trusted helper runtime into each sandbox container. Resolution order
+for the Linux artifact is:
 
 1. `supervisor_bin` in `[openshell.drivers.docker]`.
 2. `supervisor_image` in `[openshell.drivers.docker]`, extracting
@@ -164,22 +179,28 @@ each sandbox container. Resolution order is:
 4. A local Linux cargo target build for the Docker daemon architecture.
 5. The release-matched default supervisor image, extracting `/openshell-sandbox`.
 
+When a selected binary has no valid sibling `openshell-runtime`, the driver
+extracts `/openshell-runtime` from the configured or release-matched supervisor
+image. Host control uses the native `openshell-sandbox` beside the gateway (or a
+local native cargo build); Linux hosts can reuse the boundary binary.
+
 Release and Docker-image gateway builds bake the matching supervisor image tag
 into the binary at compile time. The default Docker supervisor image is not
 `:latest` unless a custom build explicitly sets that tag.
 
 ## Callback and TLS
 
-`OPENSHELL_ENDPOINT` is injected from the gateway's configured gRPC endpoint.
+`OPENSHELL_ENDPOINT` is injected only into host control from the gateway's
+configured gRPC endpoint.
 When no endpoint is configured, the driver uses
 `host.openshell.internal:<gateway-port>` with the appropriate HTTP or HTTPS
 scheme. Set `host_gateway_ip` only when the host has an explicit, locally
 assigned address that containers should use for callbacks; package-managed
 macOS gateways should leave it unset.
 
 For HTTPS endpoints, the server certificate must include the endpoint host as a
-subject alternative name. Docker sandboxes also need the client TLS bundle
-mounted into the container and exposed with:
+subject alternative name. The client TLS bundle is exposed only to host control
+with:
 
 - `OPENSHELL_TLS_CA`
 - `OPENSHELL_TLS_CERT`
@@ -189,8 +210,9 @@ HTTP endpoints reject TLS material because the supervisor would not use it.
 
 ## Environment Ownership
 
-The driver merges template environment and sandbox spec environment first, then
-overwrites security-critical keys:
+The driver writes template and sandbox environment into the protected boundary
+config. Boundary mode exposes that map only to workload children. Host control
+owns these security-critical keys:
 
 - `OPENSHELL_ENDPOINT`
 - `OPENSHELL_SANDBOX_ID`
 
@@ -0,0 +1,107 @@
+// SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//! Docker provisioning for the shared authenticated boundary protocol.
+//!
+//! Docker owns only the container/socket topology and immutable OCI resource
+//! claims. Lifecycle, process, network, identity, and wire behavior live in
+//! `openshell-isolation-interface` and `openshell-sandbox`.
+
+use std::collections::{BTreeMap, HashMap};
+use std::net::IpAddr;
+use std::path::PathBuf;
+
+use openshell_isolation_interface::boundary_protocol::{
+    BOUNDARY_PROTOCOL_VERSION, BoundaryAgentIdentity, BoundaryConfig, BoundaryListener,
+    BoundaryTopology, BoundaryTransport,
+};
+
+/// Driver-owned inputs that bind one Docker container to one boundary.
+pub struct DockerBoundarySpec {
+    pub boundary_id: String,
+    pub bootstrap_token: String,
+    pub container_id: String,
+    pub image_identity: String,
+    pub listener_socket: PathBuf,
+    pub control_socket: PathBuf,
+    pub host_gateway_ip: Option<IpAddr>,
+    pub oci_user: String,
+    pub trusted_runtime_root: PathBuf,
+    pub child_env: HashMap<String, String>,
+}
+
+/// Protected container config and matching host descriptor.
+pub struct DockerBoundaryProvisioning {
+    pub boundary_config: BoundaryConfig,
+    pub topology: BoundaryTopology,
+}
+
+impl DockerBoundarySpec {
+    /// Produce both sides of the common protocol from the same immutable
+    /// Docker coordinates so attach cannot bind a different container.
+    #[must_use]
+    pub fn provision(self) -> DockerBoundaryProvisioning {
+        let resource_claims = BTreeMap::from([
+            ("docker.container_id".to_string(), self.container_id),
+            ("docker.image_identity".to_string(), self.image_identity),
+        ]);
+        DockerBoundaryProvisioning {
+            boundary_config: BoundaryConfig {
+                protocol_version: BOUNDARY_PROTOCOL_VERSION,
+                boundary_id: self.boundary_id.clone(),
+                bootstrap_token: self.bootstrap_token.clone(),
+                listener: BoundaryListener::Unix {
+                    socket_path: self.listener_socket,
+                },
+                resource_claims: resource_claims.clone(),
+                agent_identity: BoundaryAgentIdentity::OciUser {
+                    declaration: self.oci_user,
+                },
+                protect_config_file: true,
+                trusted_runtime_root: self.trusted_runtime_root,
+                child_env: self.child_env,
+            },
+            topology: BoundaryTopology {
+                protocol_version: BOUNDARY_PROTOCOL_VERSION,
+                boundary_id: self.boundary_id,
+                transport: BoundaryTransport::Unix {
+                    socket_path: self.control_socket,
+                },
+                host_gateway_ip: self.host_gateway_ip,
+                resource_claims,
+                bootstrap_token: self.bootstrap_token,
+            },
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn provisioning_binds_container_and_image_claims() {
+        let provisioned = DockerBoundarySpec {
+            boundary_id: "sandbox-1".to_string(),
+            bootstrap_token: "a".repeat(64),
+            container_id: "sha256:container".to_string(),
+            image_identity: "sha256:image".to_string(),
+            listener_socket: PathBuf::from("/run/openshell/boundary/control.sock"),
+            control_socket: PathBuf::from("/host/control.sock"),
+            host_gateway_ip: Some(IpAddr::from([127, 0, 0, 1])),
+            oci_user: "1000:1000".to_string(),
+            trusted_runtime_root: PathBuf::from("/opt/openshell/bin/openshell-runtime"),
+            child_env: HashMap::new(),
+        }
+        .provision();
+
+        assert_eq!(
+            provisioned.boundary_config.resource_claims,
+            provisioned.topology.resource_claims
+        );
+        assert_eq!(
+            provisioned.topology.resource_claims["docker.container_id"],
+            "sha256:container"
+        );
+    }
+}