diff --git a/.github/workflows/goroot.yml b/.github/workflows/goroot.yml
index da1b28c..a4667c4 100644
--- a/.github/workflows/goroot.yml
+++ b/.github/workflows/goroot.yml
@@ -16,6 +16,12 @@ on:
         required: true
         default: main
         type: string
+      test_scope:
+        description: Suites to qualify
+        required: true
+        default: all
+        type: choice
+        options: [all, wasm]
   schedule:
     # 01:00 Asia/Shanghai (17:00 UTC on the previous day), daily.
     - cron: "0 17 * * *"
@@ -31,6 +37,7 @@ concurrency:
 
 jobs:
   goroot:
+    if: ${{ inputs.test_scope != 'wasm' }}
     name: GOROOT (${{ matrix.os }}${{ startsWith(matrix.os, 'windows') && format(', {0}, {1}', matrix.windows_abi, matrix.windows_arch) || '' }}, Go 1.26+1.27, shard ${{ matrix.shard-index }}/${{ matrix.shard-total }})
     timeout-minutes: 180
     outputs:
@@ -588,14 +595,11 @@ jobs:
             return "${pipeline_status[0]}"
           }
 
-          run_goroot "$GO126_GOROOT" "${{ steps.go126.outputs.version }}" "$shard_index" &
-          pids=("$!")
-          run_goroot "$GO127_GOROOT" "${{ steps.go127.outputs.version }}" "$paired_shard_index" &
-          pids+=("$!")
+          # Asyncify dominates large runoutput builds. Do not let two
+          # compiler/linker pools compete for this runner's CPU and memory.
           status=0
-          for pid in "${pids[@]}"; do
-            wait "$pid" || status=1
-          done
+          run_goroot "$GO126_GOROOT" "${{ steps.go126.outputs.version }}" "$shard_index" || status=1
+          run_goroot "$GO127_GOROOT" "${{ steps.go127.outputs.version }}" "$paired_shard_index" || status=1
           exit "$status"
 
       - name: Summarize GOROOT shard
@@ -712,9 +716,16 @@ jobs:
           WASM_RESULT: ${{ needs.goroot-wasm.result }}
           NATIVE_EXPECTED_REPORTS: ${{ needs.goroot.outputs.expected-reports }}
           WASM_EXPECTED_REPORTS: ${{ needs.goroot-wasm.outputs.expected-reports }}
+          TEST_SCOPE: ${{ inputs.test_scope || 'all' }}
         run: |
           source dev/go_toolchain.sh
-          if [[ ! "$NATIVE_EXPECTED_REPORTS" =~ ^[1-9][0-9]*$ || ! "$WASM_EXPECTED_REPORTS" =~ ^[1-9][0-9]*$ ]]; then
+          if [[ "$TEST_SCOPE" == wasm && "$GOROOT_RESULT" == skipped ]]; then
+            NATIVE_EXPECTED_REPORTS=0
+          elif [[ ! "$NATIVE_EXPECTED_REPORTS" =~ ^[1-9][0-9]*$ ]]; then
+            echo "error: missing expected native report count" >&2
+            exit 1
+          fi
+          if [[ ! "$WASM_EXPECTED_REPORTS" =~ ^[1-9][0-9]*$ ]]; then
             echo "error: missing expected report counts from the GOROOT matrices" >&2
             exit 1
           fi
@@ -765,6 +776,7 @@ jobs:
             echo '## GOROOT run summary'
             echo
             echo "Received $report_count/$expected_reports shard reports (two Go versions per configured matrix job)."
+            echo "Qualification scope: $TEST_SCOPE."
             echo
             echo '| Platform / toolchain | Shards | Selected | Observed | Passed | Failed | Skipped |'
             echo '|---|---:|---:|---:|---:|---:|---:|'
@@ -847,12 +859,15 @@ jobs:
         env:
           GOROOT_RESULT: ${{ needs.goroot.result }}
           WASM_RESULT: ${{ needs.goroot-wasm.result }}
+          TEST_SCOPE: ${{ inputs.test_scope || 'all' }}
         run: |
           if [[ "$GOROOT_REPORT_COUNT" -ne "$GOROOT_EXPECTED_REPORT_COUNT" ]]; then
             echo "error: expected $GOROOT_EXPECTED_REPORT_COUNT shard reports, got $GOROOT_REPORT_COUNT" >&2
             exit 1
           fi
-          if [[ "$GOROOT_RESULT" != success || "$WASM_RESULT" != success ]]; then
+          native_expected=success
+          if [[ "$TEST_SCOPE" == wasm ]]; then native_expected=skipped; fi
+          if [[ "$GOROOT_RESULT" != "$native_expected" || "$WASM_RESULT" != success ]]; then
             echo "error: one or more GOROOT shards did not succeed" >&2
             exit 1
           fi
diff --git a/.github/workflows/std.yml b/.github/workflows/std.yml
index 18dfa34..af79d7d 100644
--- a/.github/workflows/std.yml
+++ b/.github/workflows/std.yml
@@ -13,6 +13,12 @@ on:
         required: true
         default: main
         type: string
+      wasm_workers:
+        description: Go scheduler workers for Emscripten std profiles
+        required: true
+        default: '1'
+        type: choice
+        options: ['1', '2', '4']
   schedule:
     # 04:00 Asia/Shanghai (20:00 UTC on the previous day), daily.
     - cron: "0 20 * * *"
@@ -20,7 +26,7 @@ on:
 concurrency:
   # Periodic compatibility runs are reports, so a later invocation must not
   # cancel one that has already consumed hosted-runner time.
-  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.ref }}
+  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.ref }}-${{ inputs.wasm_workers || '1' }}
   cancel-in-progress: false
 
 permissions:
@@ -258,7 +264,7 @@ jobs:
           retention-days: 1
 
   wasm-std:
-    name: wasm std acceptance (${{ matrix.profile }}, ${{ matrix.shard }}/${{ matrix.profile == 'W32-WASI' && 5 || 3 }})
+    name: wasm std acceptance (${{ matrix.profile }}, workers ${{ (matrix.profile == 'J32-Emscripten' || matrix.profile == 'J64-Emscripten') && inputs.wasm_workers || '1' }}, ${{ matrix.shard }}/${{ matrix.profile == 'W32-WASI' && 5 || 3 }})
     runs-on: ubuntu-24.04
     timeout-minutes: 180
     strategy:
@@ -273,6 +279,7 @@ jobs:
             shard: 4
     env:
       GOFLAGS: -tags=llvm22
+      LLGO_WASM_WORKERS: ${{ (matrix.profile == 'J32-Emscripten' || matrix.profile == 'J64-Emscripten') && inputs.wasm_workers || '1' }}
     steps:
       - uses: actions/checkout@v7
         with:
@@ -364,9 +371,11 @@ jobs:
           if-no-files-found: error
 
   wasm-browser:
-    name: real-browser GoJS callback
+    name: real-browser GoJS callback and worker acceptance
     runs-on: ubuntu-24.04
-    timeout-minutes: 30
+    # Complete Node/Chrome worker acceptance takes about 25 minutes before
+    # dependency setup and the GoJS browser smoke; retain its per-case limits.
+    timeout-minutes: 45
     env:
       GOFLAGS: -tags=llvm22
       LLGO_BUILD_CACHE: 'on'
@@ -381,6 +390,16 @@ jobs:
       - uses: emscripten-core/setup-emsdk@v15
         with:
           version: '6.0.8'
+      - uses: actions/setup-node@v7
+        if: inputs.wasm_workers != '' && inputs.wasm_workers != '1'
+        with:
+          node-version: '24'
+      - uses: ./.github/actions/setup-binaryen
+        if: inputs.wasm_workers != '' && inputs.wasm_workers != '1'
+      - uses: bytecodealliance/actions/wasm-tools/setup@v1
+        if: inputs.wasm_workers != '' && inputs.wasm_workers != '1'
+        with:
+          version: '1.243.0'
       - uses: ./.github/actions/setup-go
       - name: Set up Chrome
         id: setup-chrome
@@ -400,6 +419,12 @@ jobs:
           BROWSER_BIN: ${{ steps.setup-chrome.outputs.chrome-path }}
           LLGO: ${{ runner.temp }}/llgo
         run: dev/test_wasm_browser.sh
+      - name: Run Emscripten worker acceptance in Node and Chrome
+        if: inputs.wasm_workers != '' && inputs.wasm_workers != '1'
+        env:
+          CHROME: ${{ steps.setup-chrome.outputs.chrome-path }}
+          LLGO: ${{ runner.temp }}/llgo
+        run: dev/test_wasm_workers.sh
 
   wasm-sentinels:
     name: wasm GOROOT sentinels
@@ -569,6 +594,8 @@ jobs:
             } >"$report_md"
           fi
 
+          printf '\nEmscripten std scheduler workers: %s. W32 uses its pthread backend; J32-GoJS, the DOM callback, and GOROOT sentinel suites use the single-worker JS scheduler.\n' \
+            '${{ inputs.wasm_workers || '1' }}' >>"$report_md"
           cat "$report_md" >>"$GITHUB_STEP_SUMMARY"
           echo "STD_REPORT=$report_md" >>"$GITHUB_ENV"