feat(podman): honor OCI image working directories

.agents/skills/debug-openshell-cluster/SKILL.md

@@ -202,6 +202,8 @@ Common findings:
 - Rootless networking unavailable: inspect Podman network configuration.
 - Sandbox image missing or pull denied: verify image reference and registry credentials.
 - Sandbox fails before readiness with an identity-resolution error: inspect the image's OCI `USER` and matching `/etc/passwd` and `/etc/group` entries, or explicitly set both process identity fields in policy. Root and missing identities are rejected.
+- Sandbox fails before readiness with an OCI workspace validation error: inspect the image's `WorkingDir` using the immutable image ID reported by the gateway. Empty, `/`, and explicit `/sandbox` use the managed `/sandbox` compatibility workspace. Any other workdir must be an absolute normalized directory with no symlink components; the effective global-or-sandbox policy UID, primary GID, or supplementary groups must already be able to traverse every parent and write and enter the directory. Podman checks the original image in a networkless temporary probe before attaching the workspace volume, so inspect the probe failure in gateway logs.
+- If Podman reports probe cleanup or timeout failures, inspect temporary containers with `podman ps -a --filter name=openshell-workdir-probe` and gateway logs. The driver force-removes the exact attempt-unique probe on every normal success or failure path. A gateway process crash can leave a stopped probe; verify its generated name and image before removing it manually. The driver deliberately does not sweep containers by a forgeable label or name prefix.
 - Supervisor cannot call back: check callback endpoint and gateway logs.
 - Gateway exits before becoming healthy with a callback-listener discovery
   error: inspect `podman info --debug`, the configured Podman network, and the

.agents/skills/openshell-cli/SKILL.md

@@ -446,6 +446,13 @@ field wins independently; omitted fields fall back to the image declaration.
 An image with no `USER` fails before readiness unless policy supplies both
 fields.
 
+Docker and Podman gateways also honor the image's OCI `WORKDIR`. An empty
+value, `/`, or `/sandbox` uses the compatibility workspace at `/sandbox`.
+Any other value must be an absolute, normalized path that already exists in
+the image, contains no symlink components, and is traversable and writable by
+the sandbox UID, GID, and supplementary groups. Podman validates that access
+against the pinned image before its managed workspace volume covers the path.
+
 ### Forward ports
 
 ```bash

architecture/compute-runtimes.md

@@ -185,8 +185,8 @@ The gateway preserves whether each policy process field was omitted. The active
 driver then supplies one authoritative identity input to the supervisor:
 
 - Docker and Podman inspect the final sandbox image, pin container creation to
-  its immutable image ID, and pass its raw OCI `Config.User`. Docker also
-  resolves the workspace from OCI `Config.WorkingDir` during that inspection.
+  its immutable image ID, and pass its raw OCI `Config.User`. They also resolve
+  the workspace from OCI `Config.WorkingDir` during that inspection.
 - Kubernetes passes its platform-resolved numeric UID/GID, including OpenShift
   SCC-derived values.
 - VM keeps its existing guest identity behavior.
@@ -199,7 +199,7 @@ and uses the same privilege-drop path for direct and SSH children. When a
 declaration omits the group, the supervisor fills it with the user's numeric
 primary GID. It does not rewrite the account files.
 
-Docker uses an absolute OCI working directory as the workspace. An
+Docker and Podman use an absolute OCI working directory as the workspace. An
 empty, root (`/`), or explicit `/sandbox` declaration uses `/sandbox`, which
 OpenShell creates and owns as a compatibility workspace. Any other workdir must already
 exist in the immutable image without symlink components. The completed
@@ -210,12 +210,19 @@ uses kernel effective-access checks so POSIX ACL and LSM decisions are honored.
 Path checks reserve the standard OCI runtime namespaces under `/proc`, `/sys`,
 and `/dev`, while separate collision checks are derived from actual OpenShell
 control paths.
-Docker performs the check in the final container before workload launch and
-rejects image `VOLUME` declarations that would mask the workdir ancestry. The
-resolved workspace is the child cwd and `HOME`; when
-`filesystem.include_workdir` is enabled, it becomes the automatic writable
-policy path. Podman, Kubernetes/OpenShift, and VM retain their existing
-`/sandbox` workspace behavior.
+Both drivers reject image `VOLUME` declarations that would mask the workdir
+ancestry. Docker performs the check in the final container before workload
+launch. Podman performs it in a minimal networkless container from the same
+pinned image ID before its managed workspace volume covers the path. The probe
+adopts the identity source from the effective global-or-sandbox policy, or
+discovers the image policy when neither exists, and emits a normalized
+attestation that the final supervisor must match. This internal Podman-only
+contract is required because the managed volume hides the original image tree
+before the final supervisor starts. The resolved workspace is the child cwd and `HOME`;
+when `filesystem.include_workdir` is enabled, it
+becomes the automatic writable policy path. Kubernetes/OpenShift keep their
+`/sandbox` PVC and `fsGroup` behavior, and VM keeps its `/sandbox` guest
+initialization path.
 
 Sandbox creation fails before the workload becomes ready when a required image
 identity is absent, malformed, unknown, ambiguous, or resolves to UID/GID 0.

crates/openshell-core/src/sandbox_env.rs

@@ -126,6 +126,13 @@ pub const SANDBOX_GID: &str = "OPENSHELL_SANDBOX_GID";
 /// OCI only for the former contract.
 pub const OCI_IMAGE_USER: &str = "OPENSHELL_OCI_IMAGE_USER";
 
+/// Normalized UID/GID/supplementary-group identity attested by the Podman
+/// immutable-image workspace probe.
+///
+/// A non-empty value also asserts that the
+/// original workspace was validated before Podman's managed volume covered it.
+pub const OCI_WORKSPACE_IDENTITY: &str = "OPENSHELL_OCI_WORKSPACE_IDENTITY";
+
 // The corporate upstream-proxy configuration deliberately has no reserved
 // environment variables: it travels on the supervisor's argv
 // (`--upstream-proxy` and friends), which a sandbox image cannot forge the

crates/openshell-driver-docker/src/lib.rs

@@ -2195,6 +2195,7 @@ fn build_environment_for_oci_user(
             user_env.extend(template.environment.clone());
         }
         user_env.extend(spec.environment.clone());
+        user_env.remove(openshell_core::sandbox_env::OCI_WORKSPACE_IDENTITY);
         environment.extend(user_env.clone());
         if !user_env.is_empty()
             && let Ok(json) = serde_json::to_string(&user_env)
@@ -2250,6 +2251,11 @@ fn build_environment_for_oci_user(
 
     environment.remove(openshell_core::sandbox_env::SANDBOX_TOKEN);
     environment.remove(openshell_core::sandbox_env::SANDBOX_TOKEN_FILE);
+    // Ignore image-provided Podman probe attestations.
+    environment.insert(
+        openshell_core::sandbox_env::OCI_WORKSPACE_IDENTITY.to_string(),
+        String::new(),
+    );
     environment.insert(
         openshell_core::sandbox_env::OCI_IMAGE_USER.to_string(),
         oci_user.to_string(),

crates/openshell-driver-docker/src/tests.rs

@@ -45,6 +45,7 @@ fn test_sandbox() -> DriverSandbox {
             }),
             resource_requirements: None,
             sandbox_token: String::new(),
+            workspace_validation_identity: None,
         }),
         status: None,
         workspace: String::new(),
@@ -578,6 +579,10 @@ fn build_environment_protects_oci_identity_metadata() {
         (openshell_core::sandbox_env::OCI_IMAGE_USER, "spoofed"),
         (openshell_core::sandbox_env::SANDBOX_UID, "9999"),
         (openshell_core::sandbox_env::SANDBOX_GID, "9999"),
+        (
+            openshell_core::sandbox_env::OCI_WORKSPACE_IDENTITY,
+            "9999:9999:",
+        ),
     ] {
         spec.environment.insert(key.to_string(), value.to_string());
     }
@@ -590,6 +595,10 @@ fn build_environment_protects_oci_identity_metadata() {
     )));
     assert!(env.contains(&format!("{}=", openshell_core::sandbox_env::SANDBOX_UID)));
     assert!(env.contains(&format!("{}=", openshell_core::sandbox_env::SANDBOX_GID)));
+    assert!(env.contains(&format!(
+        "{}=",
+        openshell_core::sandbox_env::OCI_WORKSPACE_IDENTITY
+    )));
     assert!(!env.iter().any(|entry| entry.ends_with("=spoofed")));
     assert!(!env.iter().any(|entry| entry.ends_with("=9999")));
 }

crates/openshell-driver-podman/Cargo.toml

@@ -35,6 +35,7 @@ tracing-subscriber = { workspace = true }
 thiserror = { workspace = true }
 miette = { workspace = true }
 url = { workspace = true }
+uuid = { workspace = true }
 
 [dev-dependencies]
 prost-types = { workspace = true }

crates/openshell-driver-podman/README.md

@@ -8,14 +8,27 @@ isolation enforcement to the `openshell-sandbox` supervisor binary, which is
 sideloaded into each container via an OCI image volume mount.
 
 Before creating the container, the driver inspects the final sandbox image and
-captures its immutable image ID and raw OCI `Config.User`. Container creation
-uses that image ID with pulling disabled, 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 completed 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.
+captures its immutable image ID, raw OCI `Config.User`, and OCI
+`Config.WorkingDir`. Container creation uses that image ID with pulling
+disabled, 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 completed 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.
+
+An absolute OCI working directory becomes the agent workspace. An empty,
+root (`/`), or explicit `/sandbox` declaration uses `/sandbox`, which OpenShell
+creates and owns as a compatibility workspace. For any other workdir, a
+resource-limited, networkless probe verifies the original pinned image before
+Podman covers the path with the managed workspace volume. The completed process
+identity must already be able to traverse every parent and write and enter the
+directory, without symlink components or OpenShell control-path collisions.
+The gateway supplies the identity source from the effective global-or-sandbox
+policy, or requests image-policy discovery when neither exists. The final
+supervisor must match the probe's normalized identity before preparing the
+volume. See [Compute runtimes](../../architecture/compute-runtimes.md#process-identity)
+for the invariant and probe lifecycle.
 
 For a rootless networking deep dive, see [NETWORKING.md](NETWORKING.md).
 
@@ -87,9 +100,11 @@ optional `selinux_label` of `shared` (applies `:z`) or `private` (applies
 read-only by default; set `read_only: false` to make them writable. Podman
 image and volume mounts do not support `subpath` in OpenShell driver config.
 Mount `source` and `target` values must not contain surrounding whitespace.
-Mount targets must be absolute container paths and must not replace
-the workspace root (`/sandbox`) or overlap OpenShell supervisor files,
-`/etc/openshell`, `/etc/openshell-tls`, or `/run/netns`.
+Mount targets must be absolute container paths and must not replace the
+resolved workspace root or any of its parents. Nested workspace mounts remain
+valid. Mounts also must not contain or be contained by concrete OpenShell
+control targets such as the supervisor mount, TLS and token files, runtime
+socket, or `/run/netns`.
 
 Example named-volume usage:
 
@@ -291,6 +306,13 @@ sequenceDiagram
 
     D->>P: pull_image(supervisor, "missing")
     D->>P: pull_image(sandbox_image, policy)
+    D->>P: inspect_image(sandbox_image)
+
+    opt Non-default OCI workdir
+        D->>P: create + start validation probe
+        D->>P: wait + read bounded logs
+        D->>P: force-remove exact probe name
+    end
 
     D->>P: create_volume(workspace)
     Note over D: On failure below, rollback volume