diff --git a/.kokoro/release/release-agentplatform.cfg b/.kokoro/release/release-agentplatform.cfg
index c6f0c3a7ca..bae98a1602 100644
--- a/.kokoro/release/release-agentplatform.cfg
+++ b/.kokoro/release/release-agentplatform.cfg
@@ -8,8 +8,13 @@ build_file: "google3/third_party/py/google/cloud/aiplatform/.kokoro/release/agen
 # current releases of `build` and `twine`. On 20.04's Python 3.8 pip resolves
 # back to build 1.2.2.post1, the last release that still supported 3.8. This
 # image carries python3, pip and pyenv.
+#
+# Pinned by digest rather than :current, so that a release is reproducible and a
+# rebuild of the same tag cannot silently change the toolchain underneath it.
+# This is the digest :current resolved to for the first green release build.
+# Re-pin deliberately.
 container_properties {
-  docker_image: "us-central1-docker.pkg.dev/kokoro-container-bakery/kokoro/ubuntu/ubuntu2204/full:current"
+  docker_image: "us-central1-docker.pkg.dev/kokoro-container-bakery/kokoro/ubuntu/ubuntu2204/full@sha256:a24c8287bad3a2d09eecbff0b98b8c339a3331fe5e3349d26599f3e130358244"
 }
 
 fileset_artifacts: {