diff --git a/.dockerignore b/.dockerignore
index cc88bf5..d14ce17 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -7,15 +7,17 @@
 .git
 .claude
 **/node_modules
-# plugins/ is code-only and excluded from the MAIN felis image — EXCEPT the two
-# source trees the login-limbo image (deploy/limbo/Dockerfile) compiles: its own
-# module (plugins/limbo) and the shared link core it srcDir-includes (plugins/shared).
+# plugins/ is code-only and excluded from the MAIN felis image — EXCEPT the source
+# trees the two game images compile: the login-limbo image (deploy/limbo/Dockerfile)
+# builds plugins/limbo, the lobby image (deploy/lobby/Dockerfile) builds plugins/paper,
+# and both srcDir-include the shared link core (plugins/shared).
 # `plugins/*` excludes each sibling module individually (so plugins/ itself is still
-# walked and the negations below can re-include), then the two build trees are pulled
+# walked and the negations below can re-include), then the build trees are pulled
 # back in and their Gradle outputs re-excluded to keep the context lean. The main
-# image copies none of plugins/, so carrying these two small source dirs is harmless.
+# image copies none of plugins/, so carrying these small source dirs is harmless.
 plugins/*
 !plugins/limbo
+!plugins/paper
 !plugins/shared
 plugins/**/build
 plugins/**/.gradle
diff --git a/deploy/lobby/Dockerfile b/deploy/lobby/Dockerfile
index 1aee3be..09cc548 100644
--- a/deploy/lobby/Dockerfile
+++ b/deploy/lobby/Dockerfile
@@ -17,7 +17,9 @@
 # token.
 
 # ---- build the felis-paper plugin jar (Paper API is Java 21) ----
-FROM eclipse-temurin:21-jdk AS plugin
+# gradle:8.14-jdk21 — an official Gradle image on JDK 21 (this tree vendors no Gradle
+# wrapper, and a bare JDK image ships no `gradle`). JDK 21 matches the Paper API.
+FROM gradle:8.14-jdk21 AS plugin
 WORKDIR /src
 COPY plugins/paper/ ./plugins/paper/
 COPY plugins/shared/ ./plugins/shared/