diff --git a/.github/workflows/nightly-deep.yml b/.github/workflows/nightly-deep.yml
index acb8d064..0095d537 100644
--- a/.github/workflows/nightly-deep.yml
+++ b/.github/workflows/nightly-deep.yml
@@ -123,7 +123,7 @@ jobs:
       - run: pnpm verify
 
   browser:
-    name: Browser journeys (${{ matrix.browser }})
+    name: Browser journeys (${{ matrix.browser }} / ${{ matrix.project }} / ${{ matrix.shard }} of 2)
     needs: changes
     if: needs.changes.outputs.run_deep == 'true'
     runs-on: ubuntu-latest
@@ -132,10 +132,17 @@ jobs:
       fail-fast: false
       matrix:
         browser: [chromium, firefox, webkit]
+        # Each runner owns one database and one Next dev server for about 75 tests.
+        # The prior job sent all 302 tests and six browser workers through one server.
+        project: [mobile, desktop]
+        shard: [1, 2]
     env:
       CI: true
       DATABASE_URL: postgresql://peanut:peanut@localhost:5432/peanut_split_dev
       E2E_BROWSER: ${{ matrix.browser }}
+      # A single browser shares the runner with Next and Postgres. Hosted evidence
+      # showed three workers still starved long journeys; one was stable locally.
+      E2E_WORKERS: 1
     services:
       postgres:
         image: postgres:16-alpine
@@ -157,14 +164,16 @@ jobs:
           node-version: 22
       - run: corepack enable
       - run: pnpm bootstrap
+      - name: Validate the ${{ matrix.project }} shard ${{ matrix.shard }} of 2 plan
+        run: pnpm --dir apps/web e2e:plan ${{ matrix.project }} ${{ matrix.shard }}/2
       - run: pnpm --dir apps/web exec prisma migrate deploy
       - run: pnpm --dir apps/web exec playwright install --with-deps ${{ matrix.browser }}
-      - run: pnpm --dir apps/web e2e
+      - run: pnpm --dir apps/web exec playwright test --project=${{ matrix.project }} --shard=${{ matrix.shard }}/2
       - name: Keep the report and traces
         if: ${{ !cancelled() }}
         uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
         with:
-          name: browser-${{ matrix.browser }}-${{ github.sha }}
+          name: browser-${{ matrix.browser }}-${{ matrix.project }}-${{ matrix.shard }}of2-${{ github.sha }}
           path: |
             apps/web/playwright-report
             apps/web/test-results
diff --git a/apps/web/package.json b/apps/web/package.json
index 344e6796..c04ce2c0 100644
--- a/apps/web/package.json
+++ b/apps/web/package.json
@@ -19,6 +19,7 @@
         "classes:audit": "node scripts/tailwind-class-audit.mjs",
         "test:watch": "vitest",
         "e2e": "playwright test",
+        "e2e:plan": "node scripts/validate-e2e-project-plan.mjs",
         "e2e:v2": "playwright test --config playwright.v2.config.ts",
         "icons": "node scripts/generate-icons.mjs"
     },
diff --git a/apps/web/scripts/validate-e2e-project-plan.mjs b/apps/web/scripts/validate-e2e-project-plan.mjs
new file mode 100644
index 00000000..75e93ee4
--- /dev/null
+++ b/apps/web/scripts/validate-e2e-project-plan.mjs
@@ -0,0 +1,69 @@
+import { spawnSync } from 'node:child_process'
+import { resolve } from 'node:path'
+
+const project = process.argv[2]
+const shard = process.argv[3]
+const knownProjects = ['mobile', 'desktop']
+const knownShards = ['1/2', '2/2']
+
+if (!knownProjects.includes(project)) {
+    console.error(`Expected one browser shard project (${knownProjects.join(' or ')}), got ${project ?? 'nothing'}`)
+    process.exit(1)
+}
+if (!knownShards.includes(shard)) {
+    console.error(`Expected one browser shard (${knownShards.join(' or ')}), got ${shard ?? 'nothing'}`)
+    process.exit(1)
+}
+
+const root = resolve(import.meta.dirname, '..')
+const fail = (message, result) => {
+    process.stdout.write(result?.stdout ?? '')
+    process.stderr.write(result?.stderr ?? '')
+    console.error(message)
+    process.exit(1)
+}
+
+const list = (selectedShard) => {
+    const args = ['exec', 'playwright', 'test', '--list', `--project=${project}`]
+    if (selectedShard) args.push(`--shard=${selectedShard}`)
+    const result = spawnSync('pnpm', args, {
+        cwd: root,
+        encoding: 'utf8',
+        env: { ...process.env, CI: 'true' },
+    })
+
+    if (result.error) fail(`Could not list ${project} ${selectedShard ?? 'unsharded'}: ${result.error.message}`, result)
+    if (result.status !== 0) fail(`Playwright could not list ${project} ${selectedShard ?? 'unsharded'}`, result)
+
+    const tests = [...result.stdout.matchAll(/^\s+\[([^\]]+)] › (.+)$/gm)].map((match) => ({
+        project: match[1],
+        identity: match[2],
+    }))
+    const summary = result.stdout.match(/^Total: (\d+) tests in (\d+) files$/m)
+    const foreignProjects = [...new Set(tests.filter((test) => test.project !== project).map((test) => test.project))]
+
+    if (!summary || tests.length === 0) fail(`${project} ${selectedShard ?? 'unsharded'} selected no tests`, result)
+    if (foreignProjects.length > 0)
+        fail(`${project} ${selectedShard ?? 'unsharded'} also selected: ${foreignProjects.join(', ')}`, result)
+    if (Number(summary[1]) !== tests.length)
+        fail(`Playwright reported ${summary[1]} tests but listed ${tests.length}`, result)
+
+    return { tests: new Set(tests.map((test) => test.identity)), count: tests.length, files: Number(summary[2]) }
+}
+
+const full = list()
+const halves = knownShards.map(list)
+const overlap = [...halves[0].tests].filter((test) => halves[1].tests.has(test))
+const combined = new Set(halves.flatMap((half) => [...half.tests]))
+const missing = [...full.tests].filter((test) => !combined.has(test))
+const extra = [...combined].filter((test) => !full.tests.has(test))
+
+if (overlap.length > 0) fail(`${project} shards overlap on ${overlap.length} tests`)
+if (missing.length > 0) fail(`${project} shards omit ${missing.length} tests`)
+if (extra.length > 0) fail(`${project} shards add ${extra.length} tests`)
+
+const selected = halves[knownShards.indexOf(shard)]
+console.log(
+    `Validated ${project} ${shard}: ${selected.count} tests in ${selected.files} files; ` +
+        `both shards partition all ${full.count} tests`
+)