Third-party apps run as isolated processes under the Xous microkernel, so they cannot read KeyOS or another app’s memory. Each app declares the capabilities it needs, but KeyOS independently decides which are available. Sensitive APIs remain Foundation-only even if an app requests them, while other capabilities require an on-device prompt.
Most importantly, third-party apps cannot access the master seed. An app may request an app-specific seed, which requires user approval and is derived using HMAC-SHA-256 from the master seed and that app’s unique ID. This gives each app separate deterministic key material without exposing the master seed or another app’s keys.
App packages and their contents are also signed and hash-checked, and the publisher’s fingerprint must be explicitly allowed. Developer Mode enables development tooling; it does not disable the sandbox or permission system.
The remaining risks are the normal ones: a malicious app could misuse permissions you approve, steal information you enter directly into it, attempt phishing, or exploit an undiscovered KeyOS vulnerability. Only allow publishers after verifying their fingerprint through an official source, and only install apps you trust.
