diff --git a/.forgejo/workflows/build.yml b/.forgejo/workflows/build.yml
index 70f8fd3fe..4bdb21722 100644
--- a/.forgejo/workflows/build.yml
+++ b/.forgejo/workflows/build.yml
@@ -22,17 +22,39 @@ jobs:
       - name: Get version
         id: version
         run: |
-          # Match both "'version' => '4.3.12'" and "'version' => env('COOLIFY_VERSION') ?: '4.3.12'"
-          # (greedy .* means the capture takes the last quoted string on the line)
-          BASE_VERSION=$(sed -n "s/.*'version' => .*'\([^']*\)'.*/\1/p" config/constants.php | head -1)
-          if [ -z "$BASE_VERSION" ]; then
-            echo "ERROR: could not extract base version from config/constants.php" >&2
-            exit 1
-          fi
+          # Reads one version constant out of config/constants.php.
+          # The match is anchored at the start of the line, so a nested key on
+          # another line (e.g. "'nightly' => ['version' => '5.9.9']") cannot be
+          # picked up, and the trailing greedy .* takes the LAST quoted string on
+          # the line, so both upstream shapes work:
+          #   'version' => '4.2.0',
+          #   'version' => env('COOLIFY_VERSION') ?: '4.3.12',
+          # Empty or non-version results fail the build instead of tagging the
+          # image and versions.json with garbage.
+          extract_version() {
+            key="$1"
+            value=$(sed -n "s/^[[:space:]]*'${key}' => .*'\([^']*\)'.*/\1/p" config/constants.php | head -1)
+            if [ -z "$value" ]; then
+              echo "ERROR: could not extract '${key}' from config/constants.php" >&2
+              grep -n "'${key}' =>" config/constants.php >&2 || true
+              exit 1
+            fi
+            if ! printf '%s' "$value" | grep -Eq '^[0-9]+(\.[0-9]+)+([-.][0-9A-Za-z.]+)?$'; then
+              echo "ERROR: extracted ${key} '${value}' does not look like a version." >&2
+              echo "       The '${key}' entry in config/constants.php probably changed shape;" >&2
+              echo "       see docs/operations/COOLIFY_FORK.md (How version bumping works)." >&2
+              exit 1
+            fi
+            printf '%s' "$value"
+          }
+
+          # `exit 1` inside the function only leaves the command substitution's
+          # subshell, so each call needs its own `|| exit 1`.
+          BASE_VERSION=$(extract_version version) || exit 1
+          HELPER_VERSION=$(extract_version helper_version) || exit 1
+          REALTIME_VERSION=$(extract_version realtime_version) || exit 1
           TIMESTAMP=$(date -u +%Y%m%d%H%M)
           VERSION="${BASE_VERSION}.${TIMESTAMP}"
-          HELPER_VERSION=$(sed -n "s/.*'helper_version' => '\([^']*\)'.*/\1/p" config/constants.php)
-          REALTIME_VERSION=$(sed -n "s/.*'realtime_version' => '\([^']*\)'.*/\1/p" config/constants.php)
           echo "VERSION=${VERSION}" >> "$GITHUB_OUTPUT"
           echo "HELPER_VERSION=${HELPER_VERSION}" >> "$GITHUB_OUTPUT"
           echo "REALTIME_VERSION=${REALTIME_VERSION}" >> "$GITHUB_OUTPUT"
diff --git a/docker/production/Dockerfile b/docker/production/Dockerfile
index 264bac448..277ab3a77 100644
--- a/docker/production/Dockerfile
+++ b/docker/production/Dockerfile
@@ -151,9 +151,23 @@ COPY --chown=www-data:www-data config ./config
 # MapleDeploy: inject build version into constants.php at build time.
 # The version in git stays at the upstream value to avoid rebase conflicts.
 # CI passes the timestamped version (e.g. 4.0.0-beta.468.202603140006) as a build arg.
+# The substitution replaces the whole 'version' line rather than matching a
+# quoted literal, so it works for both upstream constant shapes:
+#   'version' => '4.2.0',
+#   'version' => env('COOLIFY_VERSION') ?: '4.3.12',
+# and it collapses the env() indirection to a literal so the image always
+# reports the version it was built as, regardless of runtime env.
+# The grep is a hard gate: a silently unmatched sed used to ship an image
+# tagged with a timestamped version while reporting the upstream base version.
 ARG MAPLEDEPLOY_VERSION=""
 RUN if [ -n "$MAPLEDEPLOY_VERSION" ]; then \
-      sed -i "s/'version' => '[^']*'/'version' => '$MAPLEDEPLOY_VERSION'/" config/constants.php && \
+      sed -i -E "s|^([[:space:]]*'version' => ).*|\1'$MAPLEDEPLOY_VERSION',|" config/constants.php; \
+      if ! grep -qF "'version' => '$MAPLEDEPLOY_VERSION'," config/constants.php; then \
+        echo "ERROR: MapleDeploy version injection failed: no 'version' entry in config/constants.php matched the expected shape."; \
+        echo "       See docs/operations/COOLIFY_FORK.md (How version bumping works) before changing this step."; \
+        grep -n "'version' =>" config/constants.php || true; \
+        exit 1; \
+      fi; \
       chown www-data:www-data config/constants.php; \
     fi