diff --git a/.woodpecker/ci.yml b/.woodpecker/ci.yml
index 35acff9e..d06f9903 100644
--- a/.woodpecker/ci.yml
+++ b/.woodpecker/ci.yml
@@ -2,8 +2,22 @@
 # node:24-alpine + python3/make/g++/postgresql-client + pnpm + a warm pnpm
 # store. The install step resolves from the baked store (--prefer-offline)
 # instead of paying a ~731s cold fetch + native compile every run.
+#
+# PINNED to an immutable lock-tag (#1328, brain D27): ci-image.yml pushes
+# lock-<sha256(pnpm-lock.yaml)[:12]> atomically with :latest, so the two are
+# byte-identical at push time. A mutable :latest resolves per-pod at pull time
+# on the k8s backend, which made CI verdicts non-reproducible (same tree, same
+# config, different images across runs; see #1324 comment 23382/23386). The pin
+# changes ONLY through reviewed commits; a wrong tag fails loudly at image pull.
+#
+# Bump procedure: when a recipe change (pnpm-lock.yaml / Dockerfile.ci) lands on
+# main, ci-image.yml pushes lock-<new>; a follow-up PR updates this anchor.
+# Until then pipelines keep the old pin: reproducible, with the documented
+# network-fallback lag (frozen-lockfile resolves missing packages from network).
+# Known limitation: lock- addresses the lockfile only, so a Dockerfile-only
+# change re-pushes the same tag with new content (#1328 follow-up: recipe-hash).
 variables:
-  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:latest'
+  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:lock-9cb7ffcd8828'
   - &enable_pnpm 'corepack enable'
 
 when:
diff --git a/.woodpecker/publish.yml b/.woodpecker/publish.yml
index 2249b1c1..418ab21f 100644
--- a/.woodpecker/publish.yml
+++ b/.woodpecker/publish.yml
@@ -18,7 +18,12 @@
 variables:
   # Pre-baked CI base (see .woodpecker/ci-image.yml): node:24-alpine +
   # toolchain + warm pnpm store. Kills the second cold install publish pays.
-  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:latest'
+  # PINNED to the immutable lock-tag, not :latest (#1328, brain D27): a mutable
+  # tag resolves per-pod at pull time on the k8s backend and made CI verdicts
+  # non-reproducible (#1324). Byte-identical to :latest at pin time (pushed
+  # atomically by the same kaniko run, main 712c770, 2026-07-26). Bump only via
+  # reviewed PR, per the procedure in .woodpecker/ci.yml's header comment.
+  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:lock-9cb7ffcd8828'
   - &enable_pnpm 'corepack enable'
   # Heavy kaniko image builds (~25 min) — gate them so a merge that only touches
   # the npm-only CLI (@mosaicstack/mosaic) or docs does NOT rebuild the platform