Sealed Client's production code is designed never to:

• Open its own HTTP connection, socket, or webhook
• Collect telemetry or transmit play information
• Read Minecraft launcher accounts, profiles, or auth tokens
• Download or remotely load executable code
• Launch external processes
• Update itself remotely

Minecraft still talks to whatever game server you chose, and Sealed Client exposes packet events from that connection to its modules. "Local-only" does not mean the game connection is blocked; it means Sealed Client does not create a channel of its own separate from that connection.

The only direct file access expected is the Fabric-provided config paths, config/sealedclient/ and config/sealedclient-26.2.json. Config writes use a temporary file and swap atomically where the filesystem supports it. 1.21.4 keeps a backup of the last config that loaded cleanly and restores from it; 26.2 quarantines a corrupted file and falls back to safe defaults.

Clipboard profile exchange on 1.21.4 does not include friends, waypoints, or server connection details. Imports are capped at 256 KiB and 32 levels of JSON nesting, and only registered modules and setting values are applied. No executable code or jars are read, and enabling combat, movement, packet, or automation modules is skipped without a separate confirmation.

Local Fabric mods can use the Sealed Client API through the sealedclient:addon entry point. Sealed Client does not download addons or scan arbitrary directories for jars, but any mod you install yourself runs with the same process privileges as Sealed Client, so an addon's safety is your own assessment. The optional Baritone integration likewise only detects an official mod you installed; it is neither downloaded nor bundled. A separately installed Baritone jar is outside this security boundary for the same reason, and you should verify its source and checksum independently.

• SHA-256 detects an unofficial jar that differs from what was published
• Dependency checksums block a Gradle download that differs from what was reviewed
• A source policy test catches accidental introduction of network, process, or token APIs
• Source jars ship alongside a runtime dependency list, so review is possible
• Combat, movement, and automation default to disabled, carry risk labels, and both platforms provide ;sealed panic (disables active non-passive modules and releases keys, slots, combat, movement, Freecam, XRay, and any Sealed Client-owned Baritone state)

• A string-based source policy test is not a complete malware analyser.
• Dependency checksums confirm that a downloaded file matches; they do not prove that dependency is inherently safe.
• SHA-256 only means something when compared against a reference hash obtained through a trusted path.
• The per-platform SBOM is a list of runtime dependencies confirmed by a local build. It is not a vulnerability scan, a signature, or a security certification.
• Stripping archive timestamps and pinning file order helps reproducibility but does not automatically verify bit-for-bit reproducibility across different environments.
• Other Fabric mods you install, your Java runtime, your launcher, and your operating system are outside this repository's security boundary.

Run these against the repository state you reviewed. The Gradle toolchain uses Java 21 and 25 as appropriate per platform.

./gradlew --no-daemon clean :common:clean :platform-26.2:clean multiVersionBuild
./gradlew --no-daemon e2eTest
scripts/performance-soak.sh
scripts/baritone-integration-smoke.sh
scripts/verify-release.sh

check includes a policy test that searches production code for known network, process execution, launcher account, and token API markers. Gradle dependency verification compares build plugins, Minecraft, Fabric, test tooling, and transitive dependencies against gradle/verification-metadata.xml. Because Loom generates intermediate mapping jars whose bytes differ per operating system from the same official mapping inputs, only the public CI unit-test and build commands run in lenient mode. CI logs verification failures, while the local qualityGate and the release scripts keep strict verification.

e2eTest runs an isolated 1.21.4 Fabric client against a local integrated server. It never connects to 2b2t or any other external Minecraft server. 26.2 also verifies the real client's panic and release paths in a Client GameTest. Public CI only runs unit tests and the build, so run the local qualityGate separately before a release.

baritone-integration-smoke.sh downloads the Baritone API Fabric jar and its checksum from the official GitHub release into a temporary directory, and only when you explicitly run it. The input jar is compared against the official checksum before it runs and is never included in the Sealed Client release bundle.

You can also compare release checksums across two local builds:

scripts/verify-release.sh --repeat-builds 2

The verification script checks the SHA-256 list, basic SBOM structure, and checksum agreement between repeated builds. That comparison only establishes that two results match in that environment; it is not a substitute for independent reproducible-build infrastructure or third-party attestation.

• Build from source you reviewed, or use jars from a distribution path you trust.
• Avoid Discord attachments, unofficial mirrors, and jars redistributed by third-party launchers.
• Verify the jar and SHA256SUMS through independent trust paths where possible.
• Do not run a distribution that contains obfuscated jars absent from the source, or that requires an additional installer.
• Do not attach launcher tokens, session values, account files, or full logs to a bug report.

If you find a security problem, send the maintainers the Sealed Client version you used, your Minecraft and Fabric versions, a minimal reproduction, and the scope of impact. Strip real account tokens, server addresses, personal paths, and sensitive logs. Do not post exploitable detail or secrets publicly.

The current security review scope is the Minecraft 1.21.4 and 26.2 jars built from this repository at Sealed Client 1.0.x. Unofficial jars converted or repackaged by third parties are not covered.