diff --git a/api/base/build.gradle.kts b/api/base/build.gradle.kts
index a6fa608cc..c6cebe0ba 100644
--- a/api/base/build.gradle.kts
+++ b/api/base/build.gradle.kts
@@ -4,4 +4,5 @@ dependencies {
         exclude(group = "com.google.guava", module = "guava")
         exclude(group = "org.lanternpowered", module = "lmbda")
     }
+    compileOnlyApi("org.jetbrains", "annotations", "23.0.0")
 }
\ No newline at end of file
diff --git a/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandExecutor.java b/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandExecutor.java
index d384d097c..12a54ee90 100644
--- a/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandExecutor.java
+++ b/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandExecutor.java
@@ -25,13 +25,14 @@
 
 package org.geysermc.geyser.api.command;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
+
 /**
  * Handles executing a command.
  *
  * @param <T> the command source
  */
 public interface CommandExecutor<T extends CommandSource> {
-
     /**
      * Executes the given {@link Command} with the given
      * {@link CommandSource}.
@@ -40,5 +41,5 @@ public interface CommandExecutor<T extends CommandSource> {
      * @param command the command
      * @param args the arguments
      */
-    void execute(T source, Command command, String[] args);
+    void execute(@NonNull T source, @NonNull Command command, @NonNull String[] args);
 }
diff --git a/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandSource.java b/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandSource.java
index aabf0c4e8..45276e2c4 100644
--- a/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandSource.java
+++ b/api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandSource.java
@@ -25,6 +25,8 @@
 
 package org.geysermc.geyser.api.command;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
+
 /**
  * Represents an instance capable of sending commands.
  */
@@ -42,7 +44,7 @@ public interface CommandSource {
      *
      * @param message the message to send
      */
-    void sendMessage(String message);
+    void sendMessage(@NonNull String message);
 
     /**
      * Sends the given messages to the command source
@@ -58,7 +60,7 @@ public interface CommandSource {
     /**
      * If this source is the console.
      *
-     * @return true if  this source is the console
+     * @return true if this source is the console
      */
     boolean isConsole();
 
diff --git a/api/geyser/src/main/java/org/geysermc/geyser/api/event/EventRegistrar.java b/api/geyser/src/main/java/org/geysermc/geyser/api/event/EventRegistrar.java
index 7a2cc0071..064dd55f6 100644
--- a/api/geyser/src/main/java/org/geysermc/geyser/api/event/EventRegistrar.java
+++ b/api/geyser/src/main/java/org/geysermc/geyser/api/event/EventRegistrar.java
@@ -25,6 +25,7 @@
 
 package org.geysermc.geyser.api.event;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.geysermc.geyser.api.GeyserApi;
 
 /**
@@ -39,7 +40,8 @@ public interface EventRegistrar {
      * @param object the object to wrap around
      * @return an event registrar instance
      */
-    static EventRegistrar of(Object object) {
+    @NonNull
+    static EventRegistrar of(@NonNull Object object) {
         return GeyserApi.api().provider(EventRegistrar.class, object);
     }
 }
diff --git a/api/geyser/src/main/java/org/geysermc/geyser/api/network/BedrockListener.java b/api/geyser/src/main/java/org/geysermc/geyser/api/network/BedrockListener.java
index 58a597eb6..61fe286aa 100644
--- a/api/geyser/src/main/java/org/geysermc/geyser/api/network/BedrockListener.java
+++ b/api/geyser/src/main/java/org/geysermc/geyser/api/network/BedrockListener.java
@@ -25,6 +25,8 @@
 
 package org.geysermc.geyser.api.network;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
+
 /**
  * The listener that handles connections from Minecraft:
  * Bedrock Edition.
@@ -37,6 +39,7 @@ public interface BedrockListener {
      *
      * @return the listening address
      */
+    @NonNull
     String address();
 
     /**
diff --git a/api/geyser/src/main/java/org/geysermc/geyser/api/network/RemoteServer.java b/api/geyser/src/main/java/org/geysermc/geyser/api/network/RemoteServer.java
index b13ae5930..d0ac6ee7e 100644
--- a/api/geyser/src/main/java/org/geysermc/geyser/api/network/RemoteServer.java
+++ b/api/geyser/src/main/java/org/geysermc/geyser/api/network/RemoteServer.java
@@ -25,6 +25,8 @@
 
 package org.geysermc.geyser.api.network;
 
+import org.jetbrains.annotations.NotNull;
+
 /**
  * Represents the Java server that Geyser is connecting to.
  */
@@ -63,5 +65,6 @@ public interface RemoteServer {
      *
      * @return the auth type required by the remote server
      */
+    @NotNull
     AuthType authType();
 }
diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index d5f1c7a72..98ddd99b8 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -84,7 +84,7 @@ configure<BlossomExtension> {
 
     val mainFile = "src/main/java/org/geysermc/geyser/GeyserImpl.java"
     // On Jenkins, a detached head is checked out, so indra cannot determine the branch. Fortunately, this environment variable is available.
-    val branchName = indra.branchName() ?: System.getenv("GIT_BRANCH") ?: "DEV"
+    val branchName = indra.branchName() ?: System.getenv("BRANCH") ?: "DEV"
     val commit = indra.commit()
     val git = indra.git()
     val gitVersion = "git-${branchName}-${commit?.name?.substring(0, 7) ?: "0000000"}"