[neekolas]

Standalone sandbox key could register a provider credential for a same-name VM that start would reject. Validate the VM in the shared key-registration helper before changing network policy or prompting for the secret.

Extend the manual regression matrix to reject unexpected agents, kits, and host mounts on this path. Tests remain outside CI discovery.

Follow-up to #4753 and its key-validation review comment.

Validation:

• All 14 manual sandbox tests pass. The pre-fix wrapper fails the five new key-registration cases.
• ShellCheck and Ruff pass.
• Adversarial review at 40fbfa3fe9: passed with no findings.

Note

Validate sandbox before registering provider keys in dev/sbx/sandbox

register_key now calls check_vm before building the secret env var, allowing network access, or prompting for the API key. If the check fails, those later steps are skipped.

• Extends test_sandbox.py to cover key registration for incompatible same-name VMs, and checks that no key prompt, network-policy call, or secret-setting call happens and saved state stays unchanged.

^{Macroscope summarized 40fbfa3.}

[macroscopeapp]

Approvability

Verdict: Needs Human Approval

Macroscope's review found this PR requires human approval — This is a focused development-wrapper fix that validates the sandbox before changing network policy or registering provider credentials. Because it changes API-key and secret-handling behavior, the credential path requires human review.

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