diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ab4a44268d..ee0727329c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -613,6 +613,17 @@ jobs:
     # var unset/false) also falls back to ubuntu-latest.
     runs-on: ${{ (vars.USE_VPS_RUNNER == 'true' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository)) && fromJSON('["self-hosted","omni-release"]') || 'ubuntu-latest' }}
     needs: changes
+    # The .113 pool runs ONE next-build with room to spare and two at the edge: the
+    # box has 31 GB and a single next-build peaks at 14–16 GB RSS. On 2026-08-28
+    # 13:50Z the kernel OOM-killed main's build while a PR build ran beside it
+    # (five Build jobs had been queued by a burst of PRs). Two lanes: main keeps
+    # its own so a release is never queued behind PR traffic; PR builds serialize
+    # among themselves. GitHub keeps one running + one pending per group and
+    # CANCELS older pendings — a cancelled PR build is re-runnable; a dead main
+    # build costs the publish its artefact and a 40-minute rebuild that OOMs.
+    concurrency:
+      group: heavy-build-${{ github.ref == 'refs/heads/main' && 'main' || 'pr' }}
+      cancel-in-progress: false
     if: ${{ github.event_name != 'pull_request' || (needs.changes.outputs.code == 'true' && github.event.pull_request.draft == false) }}
     steps:
       - uses: actions/checkout@v7
diff --git a/changelog.d/maintenance/11897-ci-heavy-build-lane.md b/changelog.d/maintenance/11897-ci-heavy-build-lane.md
new file mode 100644
index 0000000000..6bb3bbee3b
--- /dev/null
+++ b/changelog.d/maintenance/11897-ci-heavy-build-lane.md
@@ -0,0 +1,3 @@
+- The CI `build` job now runs in two concurrency lanes — `main` and pull requests —
+  so a release build is never queued behind (or OOM-killed beside) PR builds on the
+  self-hosted pool, which holds one `next-build` comfortably and two at the edge.