[Seatbelt] Remove the `spawn-open` launch method and replace probe with system-lib function check by theelliotm · Pull Request #1511 · microsoft/mxc

Elliot (theelliotm) · 2026-10-15T20:56:57Z

📖 Description

The spawn-open launch method was removed in schema version 0.9. The code is currently unreachable. In addition, the probe for both spawn-exec and spawn-open checked for a file (/usr/bin/sandbox-exec) that only validates spawn-open would work.

This PR removes all code and documentation mentioning spawn-open, and replaces the probe with a check for the sandbox_init function symbol's existence in shared system libraries. This probe function is referenced by both Rust and Node.

New probe:

pub(crate) fn sandbox_init_available() -> bool {
    // SAFETY: `dlsym` only reads the NUL-terminated symbol name.
    !unsafe { libc::dlsym(libc::RTLD_SELF, c"sandbox_init".as_ptr()) }.is_null()
}

🔗 References

Resolves #1510

🔍 Validation

Lint, clippy, and full validation suite passed locally.

✅ Checklist

Signed the Contributor License Agreement
Linked to an issue
Updated documentation (if applicable)
Updated Copilot instructions (if build, architecture, or conventions changed)
If this PR changes Cargo.lock, the dependency-feed-check check passes (see pull request builds)

📋 Issue Type

Bug fix
Feature
Task

Microsoft Reviewers: Open in CodeFlow

…function exists in the system library

azure-pipelines · 2026-10-15T20:57:08Z

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Copilot

🟡 Changes recommended

The symbol lookup can incorrectly report Seatbelt as unavailable when Node loads the native library with local visibility.

1 open finding

macOS detection misses locally loaded sandbox_init symbols · New

What changed in this PR

Removes the retired Seatbelt launch path and updates macOS availability detection to check sandbox_init, addressing #1510.

Changes:

Removes spawn_open, its configuration fields, helpers, and obsolete tests.
Shares native Seatbelt discovery with the Node SDK.
Updates documentation and adds macOS platform-support tests.

File	Description
src/mxc-sdk/tests/wxc_e2e_tests_e2e_seatbelt_characterization.rs	Updates test commentary.
src/mxc-sdk/src/core/mxc_engine/probe.rs	Uses symbol-based detection.
src/mxc-sdk/src/core/mxc_engine/platform.rs	Updates availability check and diagnostic.
src/mxc-sdk/src/core/mxc_common/wire.rs	Removes launch-method field and enum.
src/mxc-sdk/src/core/mxc_common/models.rs	Removes legacy launch configuration.
src/mxc-sdk/src/core/mxc_common/config_parser.rs	Removes launch-method mapping.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/v1_0/one_shot.rs	Removes obsolete field initialization.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/v1_0/one_shot_tests/stable_candidate.rs	Removes obsolete assertions.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/v0_9/one_shot.rs	Removes obsolete field initialization.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/v0_9/one_shot_tests/stable_candidate.rs	Removes obsolete assertions.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/dev/one_shot.rs	Removes obsolete field initialization.
src/mxc-sdk/src/core/mxc_common/config_contract_adapters/dev/one_shot_tests/stable_candidate.rs	Removes obsolete assertions.
src/mxc-sdk/src/backends/seatbelt/common/seatbelt_runner.rs	Deletes LaunchServices execution; adds symbol probe.
src/mxc-sdk/src/backends/seatbelt/common/profile_builder.rs	Clarifies profile documentation.
src/mxc-sdk/src/backends/seatbelt/common/mod.rs	Corrects backend documentation.
src/mxc-sdk/README.md	Removes legacy PTY restriction text.
sdk/node/tests/unit/platform.test.ts	Adds macOS discovery projection tests.
sdk/node/src/v1/platform.ts	Uses native discovery on macOS.
sdk/node/src/v1/container.ts	Corrects profile application commentary.
sdk/node/README.md	Removes legacy PTY restriction text.
sdk/dotnet/README.md	Removes legacy PTY restriction text.
docs/development/plans/backend-support-probe-api.md	Documents revised macOS discovery.
docs/backends/seatbelt/seatbelt-backend.md	Removes retired launch-path documentation.
docs/api-reference/rust/v1/api.md	Updates PTY restrictions.
docs/api-reference/node/v1/api.md	Updates PTY restrictions.
docs/api-reference/dotnet/v1/api.md	Updates PTY restrictions.
.github/workflows/Build.MacOS.Job.yml	Updates test prerequisite commentary.

🧠 Review effort: Balanced

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Copilot

🟡 Changes recommended

The new integration test uses a URL-escaped working directory, causing failures in checkout paths containing spaces or non-ASCII characters.

1 open finding

Pass directory URL directly to avoid escaped pathname cwd failures · New

1 resolved since last review

macOS detection misses locally loaded sandbox_init symbols

🧠 Review effort: Balanced

Copilot

🟢 Approval recommended

The scoped cleanup preserves supported execution behavior, and the revised discovery includes success and failure coverage with no blocking issues identified.

0 open findings

1 resolved since last review

Pass directory URL directly to avoid escaped pathname cwd failures

🧠 Review effort: Balanced

Branden Bonaby (bbonaby) · 2026-10-15T22:15:37Z

            PlatformSupport {
                reason: Some(
-                    "/usr/bin/sandbox-exec not found; macOS install is incomplete".to_string(),
+                    "sandbox_init is unavailable; macOS install is incomplete".to_string(),


thought: thinking about all the updated error messages in this PR that reference "sandbox_init" I'm thinking we should make it more consumer friendly. Something like "Seatbelt support through MXC is unavailable" or something a long those lines. Thoughts?

Will update it to say "Seatbelt could not be found on this installation of macOS. Your macOS install might be incomplete. (sandbox_init not found)"

Branden Bonaby (bbonaby) · 2026-10-15T22:17:58Z

-/// given permissions mode. Uses `O_CREAT | O_EXCL` (create_new) to avoid
-/// symlink-following and collisions, and sets permissions immediately after
-/// creation on the open file descriptor to close the TOCTOU window.
-fn write_secure_temp_file(


question: Was this code for the launch method stuff only?

Copilot

🟢 Approval recommended

The scoped cleanup preserves supported execution behavior, and the shared detection changes have targeted coverage with no identified blocking issues.

0 open findings

🧠 Review effort: Balanced

Branden Bonaby (bbonaby) · 2026-10-16T04:59:09Z

+      support.reason = 'Seatbelt could not be found on this installation of macOS. Your macOS install might be incomplete. (sandbox_init not found)';
    }


note: we'll have to see how we can get this error message from the ffi directly so we don't have to add it in all the sdks. Do note though that I don't see an update to the .NET sdk for this. Was it already there?

remove open launch method and replace probe with a check the sandbox …

5523f56

…function exists in the system library

Elliot (theelliotm) requested a review from a team as a code owner October 15, 2026 20:56

Copilot AI balanced review requested due to automatic review settings October 15, 2026 20:57

Copilot started reviewing on behalf of Elliot (theelliotm) October 15, 2026 20:57

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Elliot (theelliotm) requested a review from Huzaifa Danish (huzaifa-d) October 15, 2026 20:59

Elliot (theelliotm) self-assigned this Oct 15, 2026

Copilot AI reviewed Oct 15, 2026

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Comment thread src/mxc-sdk/src/backends/seatbelt/common/seatbelt_runner.rs Outdated

probe now uses RTLD_SELF

22e80dd

Copilot AI balanced review requested due to automatic review settings October 15, 2026 21:50

Copilot started reviewing on behalf of Elliot (theelliotm) October 15, 2026 21:50

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Comment thread sdk/node/tests/integration/macos-seatbelt.test.ts Outdated

Using correct path type

7a20671

Copilot AI balanced review requested due to automatic review settings October 15, 2026 22:02

Copilot started reviewing on behalf of Elliot (theelliotm) October 15, 2026 22:02

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Branden Bonaby (bbonaby) reviewed Oct 15, 2026

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update msg when seatbelt isn't found

9ef4d97

Copilot AI balanced review requested due to automatic review settings October 16, 2026 00:08

Copilot started reviewing on behalf of Elliot (theelliotm) October 16, 2026 00:09

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Elliot (theelliotm) requested review from Branden Bonaby (bbonaby) and removed request for Huzaifa Danish (huzaifa-d) October 16, 2026 00:18

Branden Bonaby (bbonaby) approved these changes Oct 16, 2026

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Elliot (theelliotm) merged commit 28fbad4 into main Oct 16, 2026
31 checks passed

Elliot (theelliotm) deleted the user/emichlin/remove-open-launch-method branch October 16, 2026 05:32

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[Seatbelt] Remove the `spawn-open` launch method and replace probe with system-lib function check - #1511

[Seatbelt] Remove the `spawn-open` launch method and replace probe with system-lib function check#1511
Elliot (theelliotm) merged 4 commits into
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Elliot (theelliotm) commented Oct 15, 2026 •

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		support.reason = 'Seatbelt could not be found on this installation of macOS. Your macOS install might be incomplete. (sandbox_init not found)';
		}

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Elliot (theelliotm) commented Oct 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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📖 Description

New probe:

🔗 References

🔍 Validation

✅ Checklist

📋 Issue Type

Microsoft Reviewers: Open in CodeFlow

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Elliot (theelliotm) commented Oct 15, 2026 •

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