@@ -1,9 +1,9 @@
 name: Memory Probe
 
-# Throwaway diagnostic. Builds only the app.Dockerfile builder stage (the stage
-# that OOM-killed) on a GitHub-hosted runner across heap ceilings, sampling peak
-# memory. 8192 is the control: it must fail, or a pass at 4096 proves nothing.
-# Delete this file and the ci-memtest branch once the number is settled.
+# Throwaway diagnostic. Round 1 (heap ceilings 4096/6144/8192 on free ubuntu-latest)
+# failed at all three with exit 137 and ~15.9 GB peak — the heap ceiling is not the
+# binding constraint. Round 2 confirms the paid 8-core/32 GB runner builds it.
+# Delete this file and the ci-memtest branch once confirmed.
 
 on:
   push:
@@ -14,22 +14,22 @@ permissions:
 
 jobs:
   probe:
-    name: Build @ ${{ matrix.heap }} MB
-    runs-on: ubuntu-latest
-    timeout-minutes: 45
+    name: app image @ ${{ matrix.runner }}
+    runs-on: ${{ matrix.runner }}
+    timeout-minutes: 60
     strategy:
       fail-fast: false
       matrix:
-        heap: [8192, 6144, 4096]
+        runner: [linux-x64-8-core]
     steps:
       - name: Checkout code
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
 
       - name: Runner specs
         run: |
           echo "nproc: $(nproc)"
-          free -h
-          echo "MemTotal: $(awk '/MemTotal/{printf "%.2f GiB\n", $2/1048576}' /proc/meminfo)"
+          awk '/MemTotal/{printf "MemTotal: %.2f GiB\n", $2/1048576}' /proc/meminfo
+          df -h / | tail -1
 
       - name: Start memory sampler
         run: |
@@ -52,19 +52,21 @@ jobs:
           target: builder
           platforms: linux/amd64
           push: false
-          build-args: NEXT_BUILD_HEAP_MB=${{ matrix.heap }}
           provenance: false
           sbom: false
 
       - name: Report
         run: |
           kill "${sampler_pid}" 2>/dev/null || true
           PEAK=$(sort -n /tmp/mem-samples.log | tail -1)
-          echo "heap_ceiling_mb=${{ matrix.heap }}"
+          TOTAL=$(awk '/MemTotal/{printf "%d", $2/1024}' /proc/meminfo)
+          echo "runner=${{ matrix.runner }}"
           echo "build_outcome=${{ steps.build.outcome }}"
           echo "peak_used_mb=${PEAK}"
+          echo "total_mb=${TOTAL}"
           {
-            echo "| heap MB | outcome | peak used MB |"
-            echo "|---|---|---|"
-            echo "| ${{ matrix.heap }} | ${{ steps.build.outcome }} | ${PEAK} |"
+            echo "| runner | outcome | peak used MB | total MB |"
+            echo "|---|---|---|---|"
+            echo "| ${{ matrix.runner }} | ${{ steps.build.outcome }} | ${PEAK} | ${TOTAL} |"
           } >> $GITHUB_STEP_SUMMARY
+          [ "${{ steps.build.outcome }}" = "success" ] || exit 1