bug: mxc crate build is broken

[jeffmaury]

User Story

As a developer working on OpenShell, I want the openshell-driver-mxc crate to compile successfully, so that I can build and test the full project on Windows.

Problem Statement

The openshell-driver-mxc crate fails to compile after commit 9b6d904 ("delegate sandbox authentication to drivers") introduced the authenticate_sandbox method on the ComputeDriver trait and added a supports_sandbox_authentication field to GetCapabilitiesResponse. The mxc driver was not updated to implement the new trait method or include the new field.

Impact / Why This Matters

Any developer attempting to build the full workspace or specifically the mxc crate hits a compile error, blocking all mxc-related development and testing on Windows. There is no workaround short of manually patching the code locally.

Acceptance Criteria

• cargo check -p openshell-driver-mxc compiles without errors
• ComputeDriverService implements the authenticate_sandbox trait method
• GetCapabilitiesResponse initializer includes the supports_sandbox_authentication field

Reproduction Steps

1. Check out the main branch at or after commit 9b6d904e
2. Run cargo check -p openshell-driver-mxc
3. Observe two compilation errors:
   • E0046: missing authenticate_sandbox in ComputeDriver impl (grpc.rs:36)
   • E0063: missing field supports_sandbox_authentication in GetCapabilitiesResponse (driver.rs:302)

Environment

• OpenShell: main branch @ 9b6d904e
• OS: Windows 11 Enterprise 10.0.26200
• Rust: 1.95.0 (59807616e 2026-04-14)

Logs

error[E0046]: not all trait items implemented, missing: `authenticate_sandbox`
  --> crates\openshell-driver-mxc\src\grpc.rs:36:1
   |
36 | impl ComputeDriver for ComputeDriverService {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `authenticate_sandbox` in implementation

error[E0063]: missing field `supports_sandbox_authentication` in initializer of `GetCapabilitiesResponse`
   --> crates\openshell-driver-mxc\src\driver.rs:302:9
    |
302 |         GetCapabilitiesResponse {
    |         ^^^^^^^^^^^^^^^^^^^^^^^ missing `supports_sandbox_authentication`

[jeffmaury]

🏗️ build-plan

Implementation Plan

Issue type: fix
Complexity: Low
Confidence: High — clear path, established pattern across Docker/Podman drivers

Summary

The MXC driver is missing the authenticate_sandbox trait method added in commit 9b6d904. The supports_sandbox_authentication field in GetCapabilitiesResponse is already present (set to false). Only grpc.rs needs a one-method stub addition plus an import update, following the exact pattern used by Docker and Podman drivers.

Scope

• crates/openshell-driver-mxc/src/grpc.rs: Add AuthenticateSandboxRequest/AuthenticateSandboxResponse imports and implement authenticate_sandbox returning Status::unimplemented

Implementation Steps

1. Add AuthenticateSandboxRequest, AuthenticateSandboxResponse to the proto import block in grpc.rs
2. Add authenticate_sandbox method stub to impl ComputeDriver for ComputeDriverService returning Err(Status::unimplemented("mxc does not authenticate sandbox credentials"))

Test Plan

• Unit tests: Existing tests must continue to pass (cargo test -p openshell-driver-mxc). No new test needed — the method is a one-line unimplemented stub behind a capability gate, matching Docker/Podman which also don't test theirs.
• Integration tests: N/A
• E2E tests: N/A

Risks & Open Questions

• None. Mechanical stub following an established pattern. The gateway never dispatches to this method because supports_sandbox_authentication: false.

Documentation Impact

• None expected

---

Revision 1 — initial plan

[jeffmaury]

🏗️ build-from-issue-agent

Implementation Complete

PR: #3158

What was built

Added the missing authenticate_sandbox trait method to the MXC driver, returning Status::unimplemented to match the Docker/Podman pattern. The supports_sandbox_authentication field was already present in driver.rs.

Tests

• Unit: 27 existing tests pass; no new test needed (one-line stub behind capability gate)
• Integration: 48 existing tests pass
• E2E: N/A

Docs updated

• None needed

The issue will auto-close when the PR is merged.