@@ -2997,9 +2997,22 @@ jobs:
             packages/spec/json-schema/
           retention-days: 30
 
+      # Keeps only the entries the build's run summary (`--summarize`, left in
+      # `.turbo/runs/` by the assertion above) names, as Test Core's prune step
+      # does (#25452): the restore step takes the newest seed by prefix and
+      # turbo never evicts its local cache, so a seed saved whole is every seed
+      # before it plus this run. No summary -- the build never finished --
+      # means no save, and the previous seed stays the newest.
+      - name: Prune the Turbo cache to this run's tasks (main only)
+        id: prune-turbo-cache
+        if: always() && github.event_name == 'push'
+        run: |
+          node scripts/ci/prune-turbo-cache.mjs --site 'Build Core' \
+            --cache .turbo/cache --run-summaries .turbo/runs
+
       # Seed the shared Turbo cache from main only (see the restore step above).
       - name: Save Turbo cache (main only)
-        if: always() && github.event_name == 'push'
+        if: always() && github.event_name == 'push' && steps.prune-turbo-cache.outputs.save == 'true'
         uses: actions/cache/save@v6
         with:
           path: .turbo/cache
 
@@ -5684,7 +5684,7 @@ jobs:
           fi
           if [ -n "$WHOLE" ]; then
             echo "Type-checking the whole workspace -- $WHOLE."
-            pnpm exec turbo run typecheck "${UNIVERSE[@]}"
+            pnpm exec turbo run typecheck "${UNIVERSE[@]}" --summarize
             exit 0
           fi
           pnpm exec turbo ls "${UNIVERSE[@]}" --output=json > "$RUNNER_TEMP/typecheck-universe.json"
@@ -5700,7 +5700,7 @@ jobs:
           printf '  %s\n' "${SELECTED[@]}"
           FILTERS=()
           for P in "${SELECTED[@]}"; do FILTERS+=("--filter=$P"); done
-          pnpm exec turbo run typecheck "${FILTERS[@]}"
+          pnpm exec turbo run typecheck "${FILTERS[@]}" --summarize
 
       # Seed the shared Turbo cache from main only (see the restore step above).
       #
@@ -5721,8 +5721,21 @@ jobs:
       # merge_group is deliberately NOT added to this condition — see the
       # "why queue-branch saves are not the win they look like" note on the
       # `typecheck` aggregator at the bottom of this file.
-      - name: Save Turbo cache (main only)
+      #
+      # The seed keeps only the entries this lane's two turbo runs used, as
+      # ci.yml Test Core's prune step does (#25452): the build's and the
+      # typecheck's `--summarize` summaries, both left in `.turbo/runs/`. A
+      # bookkeeping step, not a gate: no `continue-on-error`, and it exits 0 on
+      # every run-time path.
+      - name: Prune the Turbo cache to this run's tasks (main only)
+        id: prune-turbo-cache
         if: always() && github.event_name == 'push'
+        run: |
+          node scripts/ci/prune-turbo-cache.mjs --site 'Type Check · workspace' \
+            --cache .turbo/cache --run-summaries .turbo/runs
+
+      - name: Save Turbo cache (main only)
+        if: always() && github.event_name == 'push' && steps.prune-turbo-cache.outputs.save == 'true'
         uses: actions/cache/save@v6
         with:
           path: .turbo/cache
 
@@ -121,8 +121,11 @@ jobs:
       - name: Setup workspace
         uses: ./.github/actions/setup-workspace
 
+      # Restore here, save at the end of the job: the save sits behind the
+      # prune step below, which a combined `actions/cache` post-step cannot.
       - name: Setup turbo cache
-        uses: actions/cache@v6
+        id: turbo-cache
+        uses: actions/cache/restore@v6
         with:
           path: .turbo/cache
           key: ${{ runner.os }}-turbo-${{ github.job }}-${{ github.sha }}
@@ -132,12 +135,38 @@ jobs:
 
       # The driver's own prerequisite, asserted by the script itself: pack mode
       # fails fast unless packages/cli/dist and the create-objectstack bin exist.
+      # `--summarize` writes the run summary the prune step below keeps.
       - name: Build
-        run: pnpm run build
+        run: pnpm run build --summarize
 
       # SMOKE_MODE defaults to `pack`, so this is the same invocation
       # publish-smoke.yml's pack-smoke job makes. ⛔ Do not add flags or env here
       # to make a red go away: the assertions are #14000's deliverable and a
       # refusal this script reports is a refusal a user would get.
       - name: Publish smoke (packed tarballs)
         run: bash scripts/publish-smoke.sh
+
+      # Keeps only the entries the build's run summary (`.turbo/runs/`) names,
+      # as ci.yml Test Core's prune step does (#25452): the restore step takes
+      # the newest seed by prefix and turbo never evicts its local cache, so a
+      # seed saved whole is every seed before it plus this run. The save keeps
+      # the gate the combined `actions/cache` post-step had: a green job whose
+      # exact key missed, and a save failure never fails the job.
+      - name: Prune the Turbo cache to this run's tasks
+        id: prune-turbo-cache
+        if: success() && steps.turbo-cache.outputs.cache-hit != 'true'
+        run: |
+          node scripts/ci/prune-turbo-cache.mjs --site 'Packed-tarball smoke (opt-in)' \
+            --cache .turbo/cache --run-summaries .turbo/runs
+
+      - name: Save turbo cache
+        if: >-
+          success()
+          && steps.turbo-cache.outputs.cache-hit != 'true'
+          && steps.prune-turbo-cache.outputs.save == 'true'
+        uses: actions/cache/save@v6
+        timeout-minutes: 5
+        continue-on-error: true
+        with:
+          path: .turbo/cache
+          key: ${{ runner.os }}-turbo-${{ github.job }}-${{ github.sha }}
@@ -201,17 +201,21 @@ jobs:
       - name: Setup workspace
         uses: ./.github/actions/setup-workspace
 
+      # Restore here, save at the end of the job: the save sits behind the
+      # prune step below, which a combined `actions/cache` post-step cannot.
       - name: Setup turbo cache
-        uses: actions/cache@v6
+        id: turbo-cache
+        uses: actions/cache/restore@v6
         with:
           path: .turbo/cache
           key: ${{ runner.os }}-turbo-${{ github.job }}-${{ github.sha }}
           restore-keys: |
             ${{ runner.os }}-turbo-${{ github.job }}-
             ${{ runner.os }}-turbo-
 
+      # `--summarize` writes the run summary the prune step below keeps.
       - name: Build
-        run: pnpm run build
+        run: pnpm run build --summarize
 
       - name: Publish smoke (packed tarballs)
         run: bash scripts/publish-smoke.sh
@@ -237,6 +241,31 @@ jobs:
             -f description="$desc" \
             -f target_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
 
+      # Keeps only the entries the build's run summary (`.turbo/runs/`) names,
+      # as ci.yml Test Core's prune step does (#25452): the restore step takes
+      # the newest seed by prefix and turbo never evicts its local cache, so a
+      # seed saved whole is every seed before it plus this run. The save keeps
+      # the gate the combined `actions/cache` post-step had: a green job whose
+      # exact key missed, and a save failure never fails the job.
+      - name: Prune the Turbo cache to this run's tasks
+        id: prune-turbo-cache
+        if: success() && steps.turbo-cache.outputs.cache-hit != 'true'
+        run: |
+          node scripts/ci/prune-turbo-cache.mjs --site 'Packed-tarball smoke (release candidate)' \
+            --cache .turbo/cache --run-summaries .turbo/runs
+
+      - name: Save turbo cache
+        if: >-
+          success()
+          && steps.turbo-cache.outputs.cache-hit != 'true'
+          && steps.prune-turbo-cache.outputs.save == 'true'
+        uses: actions/cache/save@v6
+        timeout-minutes: 5
+        continue-on-error: true
+        with:
+          path: .turbo/cache
+          key: ${{ runner.os }}-turbo-${{ github.job }}-${{ github.sha }}
+
   registry-canary:
     name: Registry canary (published latest)
     if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'