[vpacher]

Refs obs-rust/obs-studio#1092

What and why

On macOS the browser source ran without the CEF sandbox: browser-sandbox had no probe for macOS, so settings.no_sandbox stayed true (#1092). Measured on macOS 26.7.1, Apple Silicon, with CEF 7871: with the helpers sandboxed, browser sources work, including HTTPS fetch, WebAudio, and WebM recording and playback.

• Each helper sandboxes itself before the framework loads (CefScopedSandboxContext, as in CEF's sample helper), unless OBS passed --no-sandbox.
• The helper loads libcef_sandbox.dylib from the framework next to it (<app>/Contents/Frameworks/Chromium Embedded Framework.framework/Libraries/). ProbeSandbox() on macOS checks that file, with the framework found from the executable's path, so the probe and the helper agree. (dladdr() on cef_version_info, as on Linux, does not point into the framework on macOS.)
• With the library: mode Seatbelt, "CEF sandbox on". Without it a sandboxed helper would exit and no browser source would render, so OBS runs without the sandbox and shows the fallback warning (SandboxFallback.Message.NoSandboxLibrary, new string in en-US.ini).

Linux is unchanged; Windows still has no probe (obs-rust/obs-studio#2379).

RED → GREEN

• RED 820ca85: the probe gets macOS facts (macos, sandbox_library) and the mode Seatbelt; tests/sandbox-decision.cpp gets 6 macOS cases (decision, fallback, warning; with and without the library). 5 fail: DecideSandbox() treated the macOS probe like a Linux one.
• GREEN 82cab3b: all 28 cases pass.
• Real app (macOS 26.7.1, Apple Silicon, ad-hoc signed, local build), with a page that turns green only if HTTPS fetch, WebAudio and WebM recording and playback all work:
  • with libcef_sandbox.dylib: "CEF sandbox on: libcef_sandbox.dylib is in the CEF framework", all six helpers sandboxed (sandbox_check(): the GPU process, three utility processes, two renderers), the page green;
  • with the library moved out of the app: the fallback warning, the helpers run without the sandbox, the page green.
• Not tested: an Intel Mac (none available), and a Developer ID signed build (the releases are ad-hoc signed until macos: Releases are still not signed or notarized: configure the release credentials obs-studio#2383).

AI note: Claude Code (Claude Opus 5.5) wrote the change, the tests and this text under the submitter's direction, and ran the tests above on the submitter's machine.

[zackees]

Reviewed. The macOS helper code stays inside the existing __APPLE__ && !ENABLE_BROWSER_LEGACY block. CefScopedSandboxContext runs before LoadInHelper, as in CEF's sample helper, and --no-sandbox turns it off. The probe and the helper look in the same place (Frameworks/…/Libraries/libcef_sandbox.dylib). RED → GREEN adds 6 macOS decision, fallback and warning cases, and the fallback string is added to en-US.ini. The real-app check covers both the case with the library and the case without it. Linux behaviour is unchanged. LGTM.