Unclear The finding says the /sandbox exclude and ! suggestions appear only in a "non-auto" branch but does not say what that mode is.
What
The sandbox is a restricted environment that shell commands run inside, limiting what they can reach. Claude receives written instructions about it, and those instructions now include two paragraphs that only apply on macOS:
- Local port binding: this applies when a network proxy is configured and local binding is turned off. An
EPERMerror from bind or listen (the calls a program makes to open a port on your machine) means the sandbox blocked it. Claude can tell you to setsandbox.network.allowLocalBinding: true, which takes effect without a restart. In one variant of the instructions it can also suggest/sandbox exclude <pattern>or running the command yourself with the!prefix. openandosascript: these are blocked whenallowAppleEventsis not set to true, and Claude is told not to retry them withdangerouslyDisableSandbox: true.
Why
On a Mac, a local dev server that fails to start should now come with an explanation and a specific setting to change, instead of a bare permission error. Commands that open apps or run AppleScript will not be quietly retried outside the sandbox.
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The writer flagged doubt
The finding says the `/sandbox exclude` and `!` suggestions appear only in a "non-auto" branch but does not say what that mode is.
Anthropic's release notes agree
Improved sandbox guidance on macOS: when a local dev server can't bind a port, Claude now points to sandbox.network.allowLocalBinding