@@ -0,0 +1,78 @@
+// Counts the test cases a pull request adds and removes, from a zero-context diff, so PR Size can
+// say when a change grows the suite. Counting declarations keeps the number deterministic, unlike
+// CI timings, which move with runner load.
+const MARKER = "<!-- test-delta -->";
+const NET_CASES_TO_REPORT = 20;
+const TEST_FILE = /\.(?:test|spec)\.[cm]?[jt]sx?$/;
+// `<` admits type arguments, as in `it.each<Row>(...)`, which may span lines.
+const TEST_CASE = /^\s*(?:it|test)(?:\.\w+)*\s*[(<]/;
+const isBrowserTest = (path) => path.includes(".browser.test.");
+
+function kindOf(path) {
+  if (isBrowserTest(path)) return "browser";
+  if (path.startsWith("apps/server/") || path.includes(".integration.")) return "server";
+  return "unit";
+}
+
+/** @param {string} diff output of `git diff -U0 base...head` */
+function countTestDelta(diff) {
+  const kinds = { browser: 0, server: 0, unit: 0 };
+  const newBrowserFiles = [];
+  let path = null;
+  // A browser test file is new when it is added, or renamed from a file that was not one.
+  let file = null;
+  const flush = () => {
+    if (file?.isNew && isBrowserTest(file.target)) newBrowserFiles.push(file.target);
+  };
+  for (const line of diff.split("\n")) {
+    if (line.startsWith("diff --git ")) {
+      flush();
+      path = null;
+      file = { target: line.replace(/^diff --git a\/\S+ b\//, ""), isNew: false };
+      continue;
+    }
+    if (line.startsWith("new file mode") && file) file.isNew = true;
+    if (line.startsWith("rename from ") && file) file.isNew = !isBrowserTest(line.slice(12));
+    if (line.startsWith("--- ")) {
+      const source = line.slice(4).replace(/^a\//, "");
+      path = TEST_FILE.test(source) ? source : null;
+      continue;
+    }
+    if (line.startsWith("+++ ")) {
+      const target = line.slice(4).replace(/^b\//, "");
+      // A deleted file's target is /dev/null; keep its old path to count the removed cases.
+      if (target !== "/dev/null") path = TEST_FILE.test(target) ? target : null;
+      continue;
+    }
+    if (line.startsWith("new file mode") || !path) continue;
+    const sign = line[0] === "+" ? 1 : line[0] === "-" ? -1 : 0;
+    if (sign !== 0 && TEST_CASE.test(line.slice(1))) kinds[kindOf(path)] += sign;
+  }
+  flush();
+  return { kinds, net: kinds.browser + kinds.server + kinds.unit, newBrowserFiles };
+}
+
+/** Returns the comment body, or null when the change does not grow the suite enough to mention. */
+function render(delta) {
+  if (delta.net < NET_CASES_TO_REPORT && delta.newBrowserFiles.length === 0) return null;
+  const signed = (n) => (n > 0 ? `+${n}` : String(n));
+  const lines = [
+    MARKER,
+    `This PR changes the test suite by **${signed(delta.net)} test cases** ` +
+      `(browser ${signed(delta.kinds.browser)}, unit ${signed(delta.kinds.unit)}, server ${signed(delta.kinds.server)}).`,
+  ];
+  if (delta.newBrowserFiles.length > 0) {
+    lines.push(
+      "",
+      `New browser test files: ${delta.newBrowserFiles.map((file) => `\`${file}\``).join(", ")}.`,
+      "Each browser test file costs CI seconds of module loading before its first test runs; a unit test costs milliseconds.",
+    );
+  }
+  lines.push(
+    "",
+    "Keep tests that would fail for a real reason, and test logic below the UI where it can be. See [Testing](https://github.com/pingdotgg/t3code/blob/main/docs/internals/testing.md).",
+  );
+  return lines.join("\n");
+}
+
+module.exports = { MARKER, countTestDelta, render };
@@ -0,0 +1,59 @@
+const assert = require("node:assert/strict");
+const test = require("node:test");
+
+const { countTestDelta, render } = require("./test-delta.cjs");
+
+const diff = `diff --git a/apps/web/src/Panel.browser.test.tsx b/apps/web/src/Panel.browser.test.tsx
+new file mode 100644
+--- /dev/null
++++ b/apps/web/src/Panel.browser.test.tsx
+@@ -0,0 +1,4 @@
++it("opens", async () => {});
++  it.each<{ n: number }>([{ n: 1 }])("renders $n", async () => {});
++// it("is a comment, still counted only when it starts the line")
+diff --git a/apps/server/src/thing.test.ts b/apps/server/src/thing.test.ts
+--- a/apps/server/src/thing.test.ts
++++ b/apps/server/src/thing.test.ts
+@@ -3,2 +3,1 @@
+-it.effect("old", () => {});
+-test("older", () => {});
++  it.effect("new", () => {});
+diff --git a/packages/shared/src/gone.test.ts b/packages/shared/src/gone.test.ts
+deleted file mode 100644
+--- a/packages/shared/src/gone.test.ts
++++ /dev/null
+@@ -1,1 +0,0 @@
+-it("goes", () => {});
+diff --git a/apps/web/src/Menu.test.tsx b/apps/web/src/Menu.browser.test.tsx
+similarity index 100%
+rename from apps/web/src/Menu.test.tsx
+rename to apps/web/src/Menu.browser.test.tsx
+diff --git a/apps/web/src/Old.browser.test.tsx b/apps/web/src/New.browser.test.tsx
+similarity index 100%
+rename from apps/web/src/Old.browser.test.tsx
+rename to apps/web/src/New.browser.test.tsx
+diff --git a/apps/web/src/Panel.tsx b/apps/web/src/Panel.tsx
+--- a/apps/web/src/Panel.tsx
++++ b/apps/web/src/Panel.tsx
+@@ -1 +1 @@
++it("is not a test file", () => {});
+`;
+
+test("counts cases by kind, including deleted files, and finds new or renamed browser files", () => {
+  assert.deepEqual(countTestDelta(diff), {
+    kinds: { browser: 2, server: -1, unit: -1 },
+    net: 0,
+    newBrowserFiles: ["apps/web/src/Panel.browser.test.tsx", "apps/web/src/Menu.browser.test.tsx"],
+  });
+});
+
+test("reports only growth worth a reviewer's attention", () => {
+  const quiet = { kinds: { browser: 0, server: 3, unit: 5 }, net: 8, newBrowserFiles: [] };
+  assert.equal(render(quiet), null);
+  const growth = { kinds: { browser: 4, server: 10, unit: 12 }, net: 26, newBrowserFiles: [] };
+  assert.match(render(growth), /\*\*\+26 test cases\*\* \(browser \+4, unit \+12, server \+10\)/);
+  assert.match(
+    render(countTestDelta(diff)),
+    /New browser test files: `apps\/web\/src\/Panel\.browser\.test\.tsx`/,
+  );
+});
@@ -326,7 +326,7 @@ jobs:
         run: python3 -B .github/scripts/stage-preview-bundle.test.py
 
       - name: Test release checks
-        run: node --test .github/scripts/check-nightly-release.test.cjs .github/scripts/vercel-deployment-output.test.cjs .github/scripts/mobile-preview-comment.test.cjs
+        run: node --test .github/scripts/check-nightly-release.test.cjs .github/scripts/vercel-deployment-output.test.cjs .github/scripts/mobile-preview-comment.test.cjs .github/scripts/test-delta.test.cjs
 
       - name: Finish installing browser secret helper build libraries
         timeout-minutes: 5
@@ -355,16 +355,22 @@ jobs:
 
   # The web suite is the largest outside the server. In the shared Test job it
   # started last and ran alone for about 40s after everything else finished.
-  # release.yml mirrors this test, test_web, and test_server split.
+  # Browser tests are bound by the Vite server transforming modules for each
+  # file, not by Chromium, so a second runner (and Vite server) halves the job
+  # that gated every run. release.yml mirrors this test, test_web, and test_server split.
   test_web:
     permissions:
       contents: read
       id-token: write
-    name: Test Web
+    name: Test Web ${{ matrix.shard }}
     needs: changes
     if: ${{ !cancelled() && needs.changes.outputs.test_web != 'false' }}
     runs-on: blacksmith-8vcpu-ubuntu-2404
     timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        shard: [1, 2]
     steps:
       - name: Checkout
         uses: actions/checkout@v6
@@ -406,7 +412,7 @@ jobs:
           fi
 
       - name: Test
-        run: vp run --filter @t3tools/web test
+        run: vp run --filter @t3tools/web test --shard ${{ matrix.shard }}/${{ strategy.job-total }}
 
   # apps/server sets `fileParallelism: false`, so its test files run strictly
   # one at a time. Sharding spreads them over separate runners instead of
@@ -481,6 +487,17 @@ jobs:
             node apps/server/node_modules/playwright-core/cli.js install-deps chromium
           fi
 
+      # Each server test file runs in its own Vitest process, and a fresh install starts
+      # Vitest's content-keyed module cache empty, so every file re-transformed its imports.
+      # Only pushes to main save it, so pull requests never evict each other's entries.
+      - name: Restore Vitest module cache
+        if: steps.changes.outputs.test_server != 'false'
+        uses: actions/cache/restore@v6
+        with:
+          path: node_modules/.vitest-cache
+          key: vitest-modules-server-${{ matrix.shard }}-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml') }}-${{ github.sha }}
+          restore-keys: vitest-modules-server-${{ matrix.shard }}-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml') }}-
+
       - name: Test
         if: steps.changes.outputs.test_server != 'false'
         env:
@@ -489,15 +506,14 @@ jobs:
         run: >-
           vp run test:cached -- --shard ${{ matrix.shard }}/${{ strategy.job-total }}
           --uncached apps/server/integration/transferBudgetV2.integration.test.ts
-          --verify-hits 1 --report "${{ runner.temp }}/test-cache-${{ matrix.shard }}.json" apps/server
+          --verify-hits 1 apps/server
 
-      - name: Upload test cache measurements
-        if: always() && steps.changes.outputs.test_server != 'false'
-        uses: actions/upload-artifact@v7
+      - name: Save Vitest module cache
+        if: github.event_name == 'push' && steps.changes.outputs.test_server != 'false'
+        uses: actions/cache/save@v6
         with:
-          name: test-cache-${{ matrix.shard }}
-          path: ${{ runner.temp }}/test-cache-${{ matrix.shard }}.json
-          if-no-files-found: error
+          path: node_modules/.vitest-cache
+          key: vitest-modules-server-${{ matrix.shard }}-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml') }}-${{ github.sha }}
 
       # integration/transferBudgetV2.integration.test.ts writes the report; exactly one shard
       # produces these files. Gating the upload on their presence keeps a
 
@@ -293,3 +293,55 @@ jobs:
             core.info(
               `PR #${issueNumber}: ${nonTestChangedLines} non-test lines, ${testChangedLines} test lines, ${changedLines} effective lines -> ${nextLabelName} (${classification})`,
             );
+      # Reads the script from the base checkout above; the PR's own commits are only diffed.
+      - name: Report test suite growth
+        uses: actions/github-script@v8
+        with:
+          script: |
+            const { execFileSync } = require("node:child_process");
+            const { MARKER, countTestDelta, render } = require(
+              `${process.env.GITHUB_WORKSPACE}/.github/scripts/test-delta.cjs`,
+            );
+
+            const issueNumber = context.payload.pull_request.number;
+            const diff = execFileSync(
+              "git",
+              ["diff", "-U0", `${context.payload.pull_request.base.sha}...refs/remotes/pr-size/${issueNumber}`],
+              { encoding: "utf8", maxBuffer: 256 * 1024 * 1024 },
+            );
+            const delta = countTestDelta(diff);
+            const body = render(delta);
+            core.info(`PR #${issueNumber}: test cases ${JSON.stringify(delta.kinds)}, net ${delta.net}`);
+
+            const comments = await github.paginate(github.rest.issues.listComments, {
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: issueNumber,
+              per_page: 100,
+            });
+            const existing = comments.find(
+              (comment) => comment.user?.type === "Bot" && comment.body?.startsWith(MARKER),
+            );
+            if (body && existing) {
+              if (existing.body !== body) {
+                await github.rest.issues.updateComment({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  comment_id: existing.id,
+                  body,
+                });
+              }
+            } else if (body) {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: issueNumber,
+                body,
+              });
+            } else if (existing) {
+              await github.rest.issues.deleteComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+              });
+            }
@@ -300,11 +300,15 @@ jobs:
   # Web browser tests time out when they share a runner with the other package
   # suites: Chromium gets too little CPU and diff workers miss their 10s start budget.
   test_web:
-    name: Release web tests
+    name: Release web tests ${{ matrix.shard }}
     needs: [preflight]
     if: ${{ !failure() && !cancelled() && needs.preflight.result == 'success' }}
     runs-on: blacksmith-8vcpu-ubuntu-2404
     timeout-minutes: 10
+    strategy:
+      fail-fast: false
+      matrix:
+        shard: [1, 2]
     steps:
       - name: Checkout
         uses: actions/checkout@v6
@@ -344,10 +348,11 @@ jobs:
           fi
 
       - name: Test
-        run: vp run --filter @t3tools/web test
+        run: vp run --filter @t3tools/web test --shard ${{ matrix.shard }}/${{ strategy.job-total }}
 
       # Browser tests run source modules; this boots the production chunk graph.
       - name: Boot the built web client
+        if: matrix.shard == 1
         run: |
           vp run --filter @t3tools/web build
           node apps/web/scripts/verify-built-boot.ts
 
@@ -44,7 +44,7 @@ The reference for how this codebase wants UI built is the composer banner system
 
 - `ComposerBanner.tsx` exports one object of small slot components (`Root`, `Row`, `Icon`, `Content`, `Actions`, `Dismiss`, `Children`, and so on). Each slot owns its own Tailwind classes, exposes a `data-slot` attribute, takes `className` and spreads the rest of its props, and uses `cn` so callers can adjust without overriding. Variants and density are props on `Root`, not ad hoc class strings at call sites. Where a slot needs a real control it renders `Button` from `ui/` rather than a styled `<button>`.
 - `ComposerBannerStack.tsx` composes those slots into the ordered stack and owns only stack behavior (priority, expand and collapse, dismiss transitions).
-- Consumers such as `ComposerPlanFollowUpBanner.tsx` are a few lines of `<ComposerBanner.Row><ComposerBanner.Icon/><ComposerBanner.Content>…` and style only their own content.
+- Consumers compose the slots and style only their own content.
 
 Hold new and changed UI to that shape:
 
 
@@ -105,6 +105,7 @@ An empty database is a bad test. Seed your worktree's `.t3` with a copy of real
 - Test behavior that can break, such as orchestration and event-sourcing, provider protocol translation, auth and permission guards, persistence and migrations, external-format parsing, race fixes, and the logic a bug fix changed. Leave out tests for what types already guarantee, trivial logic, copy text, smoke runs, mock-call mirrors, callback wiring, and props rendered to static markup.
 - Extend before you add. When an existing test or table covers the behavior, add a row or an assertion there. Write a new `it` only when no case fits.
 - Test at one layer: the lowest one that fails on `main`. Do not repeat the case in a wrapper test, at each call site, or in web and mobile copies of the same logic.
+- Write a browser test only for behavior that needs a real browser: layout and scrolling, focus and pointer input, real workers, or a component wired to its hooks. Logic a component calls gets a unit test beside it (`*.logic.test.ts`). A browser test file spends seconds in CI loading its module graph before its first test runs; a unit test takes milliseconds.
 - [Testing](docs/internals/testing.md) carries these same test rules, plus review guidance, for review bots. Change both together.
 - **Do not run repo-wide checks.** No `vp check`, no `vp run -r test`, no `vp run -r typecheck` unless I ask. CI owns the full suite.
 - Backend behavior changes ship with focused tests for that behavior.
 
@@ -52,6 +52,8 @@ const childTreeGracePeriodMs = 1_200;
 const remoteDebuggingPort = process.env.T3CODE_DESKTOP_REMOTE_DEBUGGING_PORT?.trim();
 // oxlint-disable-next-line t3code/no-global-process-runtime -- Standalone dev script has no Effect runtime.
 const hostPlatform = NodeOS.platform();
+const parentPid = process.ppid;
+const parentWatchIntervalMs = 1_000;
 
 NodeChildProcess.execFileSync(
   process.execPath,
@@ -271,3 +273,14 @@ process.once("SIGTERM", () => {
 process.once("SIGHUP", () => {
   void shutdown(129);
 });
+// A parent killed without forwarding a signal leaves us reparented (to a subreaper on Linux, not
+// necessarily PID 1), and nothing else would ever stop the restart loop. This only notices the
+// death of our direct parent, so vite.config.ts launches us without a shell in between. Windows
+// never reparents, and reading process.ppid there snapshots the process table.
+if (hostPlatform !== "win32") {
+  setInterval(() => {
+    if (process.ppid !== parentPid) {
+      void shutdown(129);
+    }
+  }, parentWatchIntervalMs).unref();
+}