diff --git a/.gitea/workflows/backfill.yml b/.gitea/workflows/backfill.yml
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+name: Backfill events (one-time)
+
+# Manual only (workflow_dispatch, no push trigger) - this is a one-time
+# migration, not something that should run on every deploy. Runs the
+# same backfill_events binary (src/bin/backfill_events.rs) that would
+# otherwise need a `sudo`'d terminal session on the host to read
+# /etc/app/uhhm-portal.env's secrets - the CI job already has them
+# natively via secrets.PORTAL_NATS_URL, same source deploy.yml's
+# "Write service env" step uses, so nothing needs reading off disk at
+# all. Defaults to a dry run; check "apply" to actually write.
+
+on:
+  workflow_dispatch:
+    inputs:
+      apply:
+        description: "Actually write (unchecked = dry run, writes nothing)"
+        type: boolean
+        default: false
+
+jobs:
+  backfill:
+    runs-on: bare
+    env:
+      CARGO_HOME: /var/local/cargo
+      RUSTUP_HOME: /var/local/rustup
+      PATH: /var/local/cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/bin
+      SCCACHE_DIR: /var/local/sccache
+      SCCACHE_SERVER_PORT: "4228"
+      CARGO_TARGET_DIR: /var/local/cargo-target
+      NATS_URL: ${{ secrets.PORTAL_NATS_URL }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build backfill_events
+        run: cargo build --release --features ssr --bin backfill_events
+
+      - name: Run backfill
+        run: |
+          set -euo pipefail
+          if [ "${{ inputs.apply }}" = "true" ]; then
+            "$CARGO_TARGET_DIR/release/backfill_events" --apply
+          else
+            "$CARGO_TARGET_DIR/release/backfill_events"
+          fi