diff --git a/.forgejo/workflows/infra-sync.yml b/.forgejo/workflows/infra-sync.yml
index a3af20e..1827354 100644
--- a/.forgejo/workflows/infra-sync.yml
+++ b/.forgejo/workflows/infra-sync.yml
@@ -163,3 +163,105 @@ jobs:
               render_thermograph_secrets /opt/thermograph/infra prod /etc/thermograph.env
             fi
             echo "synced to $(git log --oneline -1)"
+
+  sync-centralis:
+    # Centralis' /etc/centralis.env has been HAND-MAINTAINED. The vault has held a
+    # copy since deploy/secrets/centralis.prod.yaml was seeded, and
+    # render_centralis_secrets has existed since the OpenBao work -- but nothing
+    # on any deploy path ever called it. A renderer with no caller is not a
+    # migration, it is a file.
+    #
+    # That gap is why enabling Google sign-in on Centralis had no safe home: the
+    # only way to set CENTRALIS_GOOGLE_CLIENT_ID was to hand-edit the live file,
+    # which is exactly what render-secrets.sh's header warns against.
+    #
+    # WHY THIS JOB RECREATES A CONTAINER WHEN THE OTHER THREE DELIBERATELY DO NOT.
+    # This workflow's header says it never rolls a service, because image tags are
+    # the app domains' axis. Centralis is different in kind: its compose file
+    # interpolates /etc/centralis.env at PARSE time (`set -a && . /etc/centralis.env
+    # && docker compose up -d`), so rendering the file without recreating the
+    # container changes nothing at all. Rendering and not recreating would be the
+    # silent no-op this estate keeps getting bitten by. It is one container with no
+    # replicas -- a two-second recreate, not a deploy.
+    if: github.ref_name == 'main'
+    runs-on: docker
+    concurrency:
+      group: infra-sync-centralis
+      cancel-in-progress: false
+    steps:
+      - name: Render /etc/centralis.env from the vault, then recreate Centralis
+        uses: https://github.com/appleboy/ssh-action@v1.2.0
+        with:
+          host: ${{ secrets.VPS2_SSH_HOST }}
+          username: ${{ secrets.VPS2_SSH_USER }}
+          key: ${{ secrets.VPS2_SSH_KEY }}
+          port: ${{ secrets.VPS2_SSH_PORT }}
+          script: |
+            set -euo pipefail
+            umask 077
+            cd /opt/thermograph
+            [ -f infra/deploy/secrets/centralis.prod.yaml ] || { echo "no Centralis vault — nothing to do"; exit 0; }
+
+            . infra/deploy/env-topology.sh
+            thermograph_topology prod
+            . infra/deploy/render-secrets.sh
+
+            scratch=$(mktemp -d); chmod 700 "$scratch"
+            trap 'rm -rf -- "$scratch"' EXIT
+
+            # Render to scratch FIRST. CENTRALIS_RENDER_DEST is the override the
+            # renderer already carries for exactly this: look before writing.
+            CENTRALIS_RENDER_DEST="$scratch/rendered.env" \
+              render_centralis_secrets /opt/thermograph/infra
+
+            # THE GUARD. On 2026-07-24 this estate lost Centralis' token registry by
+            # writing a file that was missing a key the live one had. The renderer
+            # proves its OWN output round-trips through bash, but it cannot know
+            # about a key that exists only in the live file -- someone hand-editing
+            # /etc/centralis.env to add, say, CENTRALIS_GOOGLE_CLIENT_ID is invisible
+            # to it. So: the vault must be a SUPERSET of what is live, or nothing is
+            # written and the job fails loudly.
+            #
+            # Names only. Both files are sourced in a clean environment so the
+            # comparison is over what bash actually ends up with, not over text.
+            # The `|| true` is load-bearing under `set -o pipefail`: grep exits 1 when
+            # a file yields no matching keys, which would otherwise abort the job on
+            # the exact edge case this guard exists to handle -- an empty or
+            # unreadable live file, i.e. a first run.
+            keys() { env -i bash -c 'set -a; . "$1" >/dev/null 2>&1; set +a; compgen -v' _ "$1" \
+                     | { grep -E '^(CENTRALIS_|DISCORD_)' || true; } | sort -u; }
+            keys "$scratch/rendered.env" > "$scratch/new.keys"
+            if [ -r /etc/centralis.env ]; then keys /etc/centralis.env > "$scratch/live.keys"; else : > "$scratch/live.keys"; fi
+
+            missing=$(comm -23 "$scratch/live.keys" "$scratch/new.keys" || true)
+            if [ -n "$missing" ]; then
+              echo "!! REFUSING to write /etc/centralis.env."
+              echo "!! The live file has keys the vault does not, so rendering would DELETE them:"
+              printf '!!   %s\n' $missing
+              echo "!! Someone hand-edited the live file. Put those keys in the vault instead:"
+              echo "!!   sops edit infra/deploy/secrets/centralis.prod.yaml"
+              exit 1
+            fi
+
+            added=$(comm -13 "$scratch/live.keys" "$scratch/new.keys" || true)
+            [ -n "$added" ] && printf '    new key from the vault: %s\n' $added
+
+            # Same file, byte for byte? Then there is nothing to do and no reason to
+            # bounce a healthy container.
+            if [ -r /etc/centralis.env ] && cmp -s "$scratch/rendered.env" /etc/centralis.env; then
+              echo "==> /etc/centralis.env already matches the vault — not recreating"
+              exit 0
+            fi
+
+            install -m 0600 -o "$(stat -c %U /etc/centralis.env 2>/dev/null || echo "$USER")" \
+                    -g "$(stat -c %G /etc/centralis.env 2>/dev/null || echo "$USER")" \
+                    "$scratch/rendered.env" /etc/centralis.env 2>/dev/null \
+              || sudo install -m 0600 -o agent -g agent "$scratch/rendered.env" /etc/centralis.env
+            echo "==> wrote /etc/centralis.env from the vault"
+
+            # Recreate so compose re-reads it. `docker restart` would NOT: the values
+            # are interpolated when the compose file is parsed, not read at runtime.
+            cd /opt/centralis/deploy
+            set -a; . /etc/centralis.env; set +a
+            docker compose up -d
+            docker compose ps --format '{{.Name}}\t{{.State}}\t{{.Status}}'