diff --git a/.github/workflows/ci-frontend-lint.yaml b/.github/workflows/ci-frontend-lint.yaml
index 1c87375a96..2b5fbac9c0 100644
--- a/.github/workflows/ci-frontend-lint.yaml
+++ b/.github/workflows/ci-frontend-lint.yaml
@@ -121,6 +121,18 @@ jobs:
         working-directory: frontend
         run: bun run typecheck
 
+      # src/v1 is excluded from the step above and checked under its own
+      # stricter tsconfig, after scripts/check-v1.mjs rejects non-TS files.
+      - name: Run v1 typecheck
+        working-directory: frontend
+        run: bun run typecheck:v1
+
+      # Biome on src/v1, then the folder import contract, PropTypes and `ant-`
+      # checks in scripts/check-v1.mjs, which `biome ci` cannot express.
+      - name: Run v1 lint
+        working-directory: frontend
+        run: bun run lint:v1
+
   # ci-test.yaml runs the same suite as the rig's `frontend` group, but its
   # tiers skip frontend-only PRs; this job is what gates those.
   vitest:
diff --git a/.gitignore b/.gitignore
index cfd13e388f..4817bafa05 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,8 +41,12 @@ eggs/
 lib/
 lib64/
 # The Python `lib/` rule above also matches the frontend's shadcn/ui helper
-# directory (`@/lib/utils` per components.json). Keep that tracked.
+# directory (`@/lib/utils` per components.json), the v1 `lib/` folder and the
+# v1 guardrail fixtures. Keep those tracked, or their files are silently left
+# out of commits.
 !frontend/src/lib/
+!frontend/src/v1/**/lib/
+!frontend/test-fixtures/**/lib/
 parts/
 sdist/
 var/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index e279326d6f..fe06ede0a0 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -22,9 +22,9 @@ repos:
       - id: check-docstring-first
       - id: check-ast
       - id: check-json
-        # Both files are JSONC — their tooling (VS Code, tsc) allows comments,
+        # These files are JSONC — their tooling (VS Code, tsc) allows comments,
         # but this hook parses with strict `json.loads`, which does not.
-        exclude: "(\\.vscode/launch\\.json|frontend/tsconfig\\.json)$"
+        exclude: "(\\.vscode/launch\\.json|frontend/(src/v1/)?tsconfig\\.json)$"
       - id: check-executables-have-shebangs
       - id: check-shebang-scripts-are-executable
       - id: check-toml
diff --git a/frontend/biome.json b/frontend/biome.json
index eb98923c0c..6799918af6 100644
--- a/frontend/biome.json
+++ b/frontend/biome.json
@@ -129,5 +129,73 @@
   "assist": {
     "enabled": true,
     "actions": { "source": { "organizeImports": "on" } }
-  }
+  },
+  "overrides": [
+    {
+      "includes": ["src/v1/**"],
+      "linter": {
+        "rules": {
+          "style": {
+            "noRestrictedImports": {
+              "level": "error",
+              "options": {
+                "paths": {
+                  "prop-types": "v1 is typed with TypeScript; PropTypes are not used under src/v1.",
+                  "antd": "antd is not used under src/v1."
+                },
+                "patterns": [
+                  {
+                    "group": [
+                      "../**",
+                      "..",
+                      "./../**",
+                      "/**",
+                      "@/**",
+                      "src/**"
+                    ],
+                    "message": "v1 imports nothing outside src/v1, and never with '../'. Use './' within a folder and '@v1/...' across folders."
+                  },
+                  {
+                    "group": ["@ant-design/**", "antd/**"],
+                    "message": "antd is not used under src/v1."
+                  },
+                  {
+                    "group": ["prop-types/**"],
+                    "message": "v1 is typed with TypeScript; PropTypes are not used under src/v1."
+                  },
+                  {
+                    "group": ["**/*.css", "!@v1/styles/**"],
+                    "message": "No component .css under src/v1; style with tokens and Tailwind. Global v1 styles live in @v1/styles/."
+                  }
+                ]
+              }
+            }
+          },
+          "suspicious": {
+            "noExplicitAny": "error"
+          }
+        }
+      }
+    },
+    {
+      "includes": ["src/**", "!src/v1/**"],
+      "linter": {
+        "rules": {
+          "style": {
+            "noRestrictedImports": {
+              "level": "error",
+              "options": {
+                "patterns": [
+                  {
+                    "group": ["@v1/**", "**/v1", "**/v1/**", "!@v1"],
+                    "message": "v0 may import only the v1 public entry, as '@v1'."
+                  }
+                ]
+              }
+            }
+          }
+        }
+      }
+    }
+  ]
 }
diff --git a/frontend/jsconfig.json b/frontend/jsconfig.json
index 082b33982c..63ea90da3d 100644
--- a/frontend/jsconfig.json
+++ b/frontend/jsconfig.json
@@ -2,9 +2,10 @@
   "compilerOptions": {
     "baseUrl": ".",
     "paths": {
-      "@/*": ["./src/*"]
+      "@/*": ["./src/*"],
+      "@v1": ["./src/v1/index.ts"]
     }
   },
   "include": ["src/**/*"],
-  "exclude": ["node_modules", "build"]
+  "exclude": ["node_modules", "build", "src/v1"]
 }
diff --git a/frontend/package.json b/frontend/package.json
index b4ab1e1bd5..3d7f579cc9 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -77,7 +77,10 @@
     "check:fix": "biome check --write src/",
     "lint:all": "biome check --write src/",
     "lint:changed": "(git diff --name-only --diff-filter=ACMR; git ls-files --others --exclude-standard) | grep -E '\\.[jt]sx?$' | sed 's|^frontend/||' | sort -u | xargs -r biome check --write",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "typecheck:v1": "node scripts/check-v1.mjs --files && tsc -p src/v1/tsconfig.json",
+    "lint:v1": "biome lint src/v1/ && node scripts/check-v1.mjs --code",
+    "test:v1": "vitest run --dir src/v1 --passWithNoTests && node --test test-fixtures/v1-boundary/boundary.fixtures.mjs"
   },
   "browserslist": {
     "production": [
diff --git a/frontend/scripts/check-v1.mjs b/frontend/scripts/check-v1.mjs
new file mode 100755
index 0000000000..3e842480c4
--- /dev/null
+++ b/frontend/scripts/check-v1.mjs
@@ -0,0 +1,463 @@
+#!/usr/bin/env node
+/*
+ * Guard for the v1 frontend (src/v1/): the rules Biome cannot express.
+ *
+ *   --files  TypeScript only (a .js under v1 is skipped by tsc, not failed,
+ *            because allowJs is off), style files only in styles/, and every
+ *            file inside the v1 folder taxonomy. Run by `typecheck:v1`.
+ *   --code   Imports: nothing outside src/v1 and the folder import contract
+ *            (which v1 folder may import which). No PropTypes, no antd `ant-`
+ *            class names. Also scans v0 (the rest of src/) for imports that
+ *            reach into v1 other than through `@v1`. Run by `lint:v1`.
+ *
+ * With neither flag, both run. It always checks the src/v1 beside this
+ * script; the fixtures in test-fixtures/v1-boundary/ copy it into each
+ * throwaway tree for that reason.
+ *
+ * The v0 <-> v1 boundary is also a Biome rule (biome.json `overrides`), so CI
+ * and editors report it. The script repeats both halves because it also reads
+ * template-literal imports, Vite globs, require() and CSS @import, which
+ * Biome does not. Biome overrides
+ * replace rule options rather than merge them, which is why the per-folder
+ * contract lives here and not as one override per folder.
+ *
+ * The `ant-` check exists only while antd markup survives in v0; drop it
+ * once the shadcn migration is complete.
+ */
+import fs from "node:fs";
+import path from "node:path";
+
+const SRC = path.join(import.meta.dirname, "..", "src");
+const ROOT = path.join(SRC, "v1");
+const args = new Set(process.argv.slice(2));
+const runFiles = args.has("--files") || !args.has("--code");
+const runCode = args.has("--code") || !args.has("--files");
+
+const ALL = "*";
+/*
+ * Folder -> folders it may import from, besides itself. `entry` is
+ * src/v1/index.ts. Pages may not import other pages, app/, test/ (except
+ * from test files) or the entry.
+ * Mirrors the table in src/v1/README.md; change both together.
+ */
+const CONTRACT = {
+  entry: ALL,
+  app: ALL,
+  plugins: ALL,
+  test: ALL,
+  pages: [
+    "components/ui",
+    "components/patterns",
+    "shell",
+    "services",
+    "stores",
+    "hooks",
+    "lib",
+    "styles",
+    "plugins",
+  ],
+  "components/ui": ["lib", "styles"],
+  "components/patterns": [
+    "components/ui",
+    "lib",
+    "services",
+    "stores",
+    "hooks",
+  ],
+  shell: [
+    "components/ui",
+    "components/patterns",
+    "services",
+    "stores",
+    "hooks",
+    "lib",
+  ],
+  services: ["lib"],
+  stores: ["lib"],
+  hooks: ["lib"],
+  lib: [],
+  styles: ["lib"],
+};
+const TOP_LEVEL = new Set([
+  "app",
+  "shell",
+  "services",
+  "stores",
+  "hooks",
+  "lib",
+  "styles",
+  "plugins",
+  "test",
+]);
+const ROOT_FILES = new Set(["index.ts", "tsconfig.json", "README.md"]);
+
+const CODE_EXT = /\.(ts|tsx|mts|cts)$/;
+const JS_EXT = /\.(js|jsx|mjs|cjs)$/;
+const STYLE_EXT = /\.(css|scss|sass|less)$/;
+const TEST_FILE = /\.(test|spec)\.(ts|tsx|mts|cts)$/;
+// Specifiers that leave src/v1: root-absolute, parent, the v0 alias, src/.
+const OUTSIDE = /^(\/|\.\.(\/|$)|@\/|src\/)/;
+
+/*
+ * The v1 folder a path (relative to src/v1, `/`-separated) belongs to, e.g.
+ * "components/ui" or "pages/settings"; null when it is outside the taxonomy.
+ * `isDir` is for import targets like "@v1/lib", which name a folder.
+ */
+function folderOf(rel, isDir = false) {
+  const segs = rel.split("/").filter(Boolean);
+  const depth = isDir ? segs.length + 1 : segs.length;
+  if (segs.length === 0 || (depth === 1 && segs[0] === "index.ts")) {
+    return "entry";
+  }
+  if (depth === 1) {
+    return null;
+  }
+  const [top, sub] = segs;
+  if (top === "components") {
+    return (sub === "ui" || sub === "patterns") && depth >= 3
+      ? `components/${sub}`
+      : null;
+  }
+  if (top === "pages") {
+    return sub && depth >= 3 ? `pages/${sub}` : null;
+  }
+  return TOP_LEVEL.has(top) ? top : null;
+}
+
+function contractKey(folder) {
+  return folder.startsWith("pages/") ? "pages" : folder;
+}
+
+function mayImport(from, to, isTestFile) {
+  if (from === to) {
+    return true;
+  }
+  if (isTestFile && to === "test") {
+    return true;
+  }
+  if (from.startsWith("pages/") && to.startsWith("pages/")) {
+    return false;
+  }
+  const allowed = CONTRACT[contractKey(from)];
+  return allowed === ALL || allowed.includes(to);
+}
+
+/*
+ * Blanks comments, keeping line numbers so matches can be reported. Tracks
+ * strings and template literals (including `${}` expressions), so a `/*` or
+ * `//` inside a string does not swallow the code after it. Regex literals are
+ * not tracked; a quote inside one is read as a string to the end of the line
+ * at most, so it can hide that line only.
+ */
+function blankComments(src) {
+  let out = "";
+  let i = 0;
+  // "`" = inside a template literal; "{" = inside a `${}` or a brace in one.
+  const stack = [];
+  while (i < src.length) {
+    let end;
+    if (stack.at(-1) === "`") {
+      end = i + templateStep(src, i, stack);
+    } else if (src[i] === "/" && (src[i + 1] === "/" || src[i + 1] === "*")) {
+      end = commentEnd(src, i);
+      out += src.slice(i, end).replace(/[^\n]/g, " ");
+      i = end;
+      continue;
+    } else if (src[i] === '"' || src[i] === "'") {
+      end = stringEnd(src, i);
+    } else {
+      codeStep(src[i], stack);
+      end = i + 1;
+    }
+    out += src.slice(i, end);
+    i = end;
+  }
+  return out;
+}
+
+/* Index just past the line or block comment that starts at i. */
+function commentEnd(src, i) {
+  if (src[i + 1] === "/") {
+    const newline = src.indexOf("\n", i);
+    return newline === -1 ? src.length : newline;
+  }
+  const close = src.indexOf("*/", i + 2);
+  return close === -1 ? src.length : close + 2;
+}
+
+/* Index just past the '...' or "..." string that starts at i. An unclosed
+ * string ends at the newline. */
+function stringEnd(src, i) {
+  let j = i + 1;
+  while (j < src.length && src[j] !== src[i] && src[j] !== "\n") {
+    j += src[j] === "\\" ? 2 : 1;
+  }
+  return j + 1;
+}
+
+/* One step inside a template literal: how many characters to copy. Closing
+ * the literal or opening `${` updates the stack. */
+function templateStep(src, i, stack) {
+  if (src[i] === "\\") {
+    return 2;
+  }
+  if (src[i] === "`") {
+    stack.pop();
+    return 1;
+  }
+  if (src[i] === "$" && src[i + 1] === "{") {
+    stack.push("{");
+    return 2;
+  }
+  return 1;
+}
+
+/* Tracks template literals and the braces inside their `${}` expressions. */
+function codeStep(c, stack) {
+  if (c === "`") {
+    stack.push("`");
+  } else if (c === "{" && stack.length > 0) {
+    stack.push("{");
+  } else if (c === "}" && stack.length > 0) {
+    stack.pop();
+  }
+}
+
+// A specifier: a quoted or backtick string with no interpolation.
+const SPEC = "[\"'`]([^\"'`$]+)[\"'`]";
+const IMPORT_RES = [
+  new RegExp(
+    String.raw`\b(?:import|export)\s+(?:type\s+)?(?:[\w$*{}\s,]+?\s+from\s+)?${SPEC}`,
+    "g",
+  ),
+  new RegExp(String.raw`\bimport\s*\(\s*${SPEC}\s*[,)]`, "g"),
+  new RegExp(String.raw`\brequire\s*\(\s*${SPEC}\s*\)`, "g"),
+];
+// Vite globs: one pattern or an array of them. Every pattern is checked.
+const GLOB_RE = new RegExp(
+  String.raw`\bimport\.meta\.glob\s*(?:<[^>]*>)?\(\s*(\[[^\]]*\]|${SPEC})`,
+  "g",
+);
+const SPEC_RE = new RegExp(SPEC, "g");
+
+/* Every import specifier in comment-blanked source, with its offset. */
+function* importSpecs(text) {
+  for (const re of IMPORT_RES) {
+    for (const m of text.matchAll(re)) {
+      yield { spec: m[1], index: m.index };
+    }
+  }
+  for (const m of text.matchAll(GLOB_RE)) {
+    const start = m.index + m[0].indexOf(m[1]);
+    for (const s of m[1].matchAll(SPEC_RE)) {
+      yield { spec: s[1], index: start + s.index };
+    }
+  }
+}
+// CSS `@import` and `url()` targets, for the files in styles/.
+const CSS_IMPORT_RE = /(?:@import\s+(?:url\(\s*)?|url\(\s*)["']?([^"')\s;]+)/g;
+
+/*
+ * Classifies a specifier: "outside" when it leaves src/v1; the v1 folder it
+ * names; null for a v1 path outside the taxonomy; undefined for a package.
+ */
+function targetFolder(spec, fileRel) {
+  if (OUTSIDE.test(spec)) {
+    return "outside";
+  }
+  if (spec === "@v1" || /^@v1\/index(\.ts)?$/.test(spec)) {
+    return "entry";
+  }
+  let rel;
+  if (spec.startsWith("@v1/")) {
+    rel = path.posix.normalize(spec.slice(4));
+  } else if (spec.startsWith("./")) {
+    rel = path.posix.join(path.posix.dirname(fileRel), spec);
+  } else {
+    return undefined;
+  }
+  if (rel.startsWith("..")) {
+    return "outside";
+  }
+  // No extension on the last segment -> it may name a folder ("@v1/lib").
+  const isDir = !path.posix.extname(rel);
+  return folderOf(rel, isDir) ?? folderOf(rel) ?? null;
+}
+
+function lineAt(text, index) {
+  return text.slice(0, index).split("\n").length;
+}
+
+// Finder litter; never committed (.gitignore), so not worth reporting.
+const IGNORED = new Set([".DS_Store"]);
+
+/* Every file under dir, plus symlinks, which are reported rather than
+ * followed: a linked file would bring outside code in unchecked. */
+function walk(dir) {
+  return fs
+    .readdirSync(dir, { recursive: true, withFileTypes: true })
+    .filter((d) => (d.isFile() || d.isSymbolicLink()) && !IGNORED.has(d.name))
+    .map((d) =>
+      path
+        .relative(dir, path.join(d.parentPath, d.name))
+        .replaceAll(path.sep, "/"),
+    )
+    .toSorted((a, b) => a.localeCompare(b));
+}
+
+const problems = [];
+const report = (rel, line, msg) => {
+  const where = line ? `${rel}:${line}` : rel;
+  problems.push(`src/v1/${where}: ${msg}`);
+};
+
+if (!fs.existsSync(ROOT)) {
+  console.error(`check-v1: ${ROOT} does not exist`);
+  process.exit(2);
+}
+
+for (const rel of walk(ROOT)) {
+  const name = path.posix.basename(rel);
+  const isRootFile = !rel.includes("/");
+  const folder = folderOf(rel);
+
+  if (fs.lstatSync(path.join(ROOT, rel)).isSymbolicLink()) {
+    if (runFiles) {
+      report(rel, 0, "No symlinks under v1; they bypass these checks.");
+    }
+    continue;
+  }
+
+  if (runFiles) {
+    if (JS_EXT.test(name)) {
+      report(rel, 0, "v1 is TypeScript only; use .ts or .tsx.");
+    }
+    if (STYLE_EXT.test(name) && folder !== "styles") {
+      report(rel, 0, "No component style files; only styles/ holds CSS.");
+    }
+    if (
+      isRootFile
+        ? !ROOT_FILES.has(name)
+        : folder === null && name !== ".gitkeep"
+    ) {
+      report(rel, 0, "Outside the v1 folder taxonomy (see src/v1/README.md).");
+    }
+  }
+
+  if (runCode && STYLE_EXT.test(name) && folder === "styles") {
+    const css = blankComments(fs.readFileSync(path.join(ROOT, rel), "utf8"));
+    for (const m of css.matchAll(CSS_IMPORT_RE)) {
+      if (targetFolder(m[1], rel) === "outside") {
+        report(
+          rel,
+          lineAt(css, m.index),
+          `'${m[1]}' is outside src/v1; v1 styles import nothing outside it.`,
+        );
+      }
+    }
+    for (const m of css.matchAll(/(?<![\w$-])ant-/g)) {
+      report(rel, lineAt(css, m.index), "No antd 'ant-' class names under v1.");
+    }
+  }
+
+  if (!runCode || !CODE_EXT.test(name) || folder === null) {
+    continue;
+  }
+  const text = blankComments(fs.readFileSync(path.join(ROOT, rel), "utf8"));
+  const isTestFile = TEST_FILE.test(name);
+
+  for (const { spec, index } of importSpecs(text)) {
+    const to = targetFolder(spec, rel);
+    const line = lineAt(text, index);
+    if (to === undefined) {
+      continue;
+    }
+    if (to === "outside") {
+      report(
+        rel,
+        line,
+        `'${spec}' is outside src/v1; v1 imports nothing outside it.`,
+      );
+    } else if (to === null) {
+      report(rel, line, `'${spec}' is outside the v1 folder taxonomy.`);
+    } else if (!mayImport(folder, to, isTestFile)) {
+      report(
+        rel,
+        line,
+        `${folder}/ may not import from ${to}/ ('${spec}'); see the folder contract in src/v1/README.md.`,
+      );
+    }
+  }
+  for (const m of text.matchAll(/\.propTypes\b|\bpropTypes\s*[:=]/g)) {
+    report(
+      rel,
+      lineAt(text, m.index),
+      "No PropTypes under v1; type props with TypeScript.",
+    );
+  }
+  // Also catches built names (`ant-${x}`, "ant-" + x).
+  for (const m of text.matchAll(/(?<![\w$-])ant-/g)) {
+    report(rel, lineAt(text, m.index), "No antd 'ant-' class names under v1.");
+  }
+}
+
+/*
+ * The v0 -> v1 half: v0 (everything in src/ outside v1, including the cloud
+ * src/plugins/ overlay) reaches v1 only through the `@v1` entry.
+ */
+const V0_CODE_EXT = /\.(js|jsx|mjs|cjs|ts|tsx|mts|cts)$/;
+
+/* Whether a v0 specifier (fileRel is relative to src/) reaches into v1. */
+function intoV1(spec, fileRel) {
+  if (spec === "@v1" || /^@v1\/index(\.ts)?$/.test(spec)) {
+    return false;
+  }
+  if (spec.startsWith("@v1/") || /^(@\/|src\/)v1(\/|$)/.test(spec)) {
+    return true;
+  }
+  if (!spec.startsWith(".")) {
+    return false;
+  }
+  const rel = path.posix.join(path.posix.dirname(fileRel), spec);
+  return rel === "v1" || rel.startsWith("v1/");
+}
+
+function v0Specs(rel, text) {
+  if (!STYLE_EXT.test(rel)) {
+    return importSpecs(text);
+  }
+  return [...text.matchAll(CSS_IMPORT_RE)].map((m) => ({
+    spec: m[1],
+    index: m.index,
+  }));
+}
+
+function checkV0() {
+  for (const rel of walk(SRC)) {
+    const full = path.join(SRC, rel);
+    const inV1 = rel.startsWith("v1/");
+    const scanned = STYLE_EXT.test(rel) || V0_CODE_EXT.test(rel);
+    if (inV1 || !scanned || fs.lstatSync(full).isSymbolicLink()) {
+      continue;
+    }
+    const text = blankComments(fs.readFileSync(full, "utf8"));
+    for (const { spec, index } of v0Specs(rel, text)) {
+      if (intoV1(spec, rel)) {
+        problems.push(
+          `src/${rel}:${lineAt(text, index)}: '${spec}' reaches into src/v1; v0 may import only the v1 public entry, as '@v1'.`,
+        );
+      }
+    }
+  }
+}
+
+if (runCode) {
+  checkV0();
+}
+
+if (problems.length > 0) {
+  console.error(problems.join("\n"));
+  console.error(`\ncheck-v1: ${problems.length} problem(s).`);
+  process.exit(1);
+}
+console.log("check-v1: ok");
diff --git a/frontend/src/v1/README.md b/frontend/src/v1/README.md
new file mode 100644
index 0000000000..61fa459ac3
--- /dev/null
+++ b/frontend/src/v1/README.md
@@ -0,0 +1,50 @@
+# Frontend v1
+
+The v1 frontend, built alongside v0 (everything else under `src/`) until v0 is
+retired. The full guide is the Frontend Developer Guide for v1 (UN-4378); this
+file holds only the rules that tooling enforces.
+
+## Rules
+
+- **TypeScript only.** `.ts` / `.tsx`, `strict`, unused locals and parameters
+  are errors, no explicit `any`.
+- **Nothing outside `src/v1`.** No v0 component, store, hook, helper, CSS or
+  shim, and no symlinks. Import with `./` within a folder and `@v1/...` across
+  folders; `../`, `/src/...` and `src/...` are never used.
+- **v0 imports only the public entry**, `@v1` (`src/v1/index.ts`).
+- **No PropTypes, no component `.css`, no antd** (package, shim or `ant-`
+  class). Global v1 styles live in `styles/` and are imported as
+  `@v1/styles/...`, including from inside `styles/`.
+
+## Folders and what each may import
+
+Every folder may import from itself. Test files (`*.test.ts(x)`,
+`*.spec.ts(x)`) may also import `test/`.
+
+| Folder | Holds | May import from |
+| --- | --- | --- |
+| `index.ts` | Public entry; the version switch (UN-4271) will mount v1 through it | everything |
+| `app/` | Entry, providers, router, route registry | everything |
+| `components/ui/` | Core components | `lib/`, `styles/` |
+| `components/patterns/` | Composites built from core components | `components/ui/`, `lib/`, `services/`, `stores/`, `hooks/` |
+| `shell/` | Top bar, rail, context bar, tab bar | `components/ui/`, `components/patterns/`, `services/`, `stores/`, `hooks/`, `lib/` |
+| `pages/<page>/` | One folder per target page | `components/ui/`, `components/patterns/`, `shell/`, `services/`, `stores/`, `hooks/`, `lib/`, `styles/`, `plugins/` — not other pages, `app/`, `test/` or the entry |
+| `services/` | Typed service modules; the only place a URL appears | `lib/` |
+| `stores/` | Zustand stores | `lib/` |
+| `hooks/` | Shared hooks | `lib/` |
+| `lib/` | Pure helpers | — |
+| `styles/` | Tokens and global v1 styles | `lib/` |
+| `plugins/` | Cloud overlay target; empty in the public repository | everything |
+| `test/` | Render helpers, fixtures, network mocks | everything |
+
+## Scripts
+
+| Script | Checks |
+| --- | --- |
+| `bun run typecheck:v1` | TypeScript-only files, CSS only in `styles/`, no symlinks, folder taxonomy; then `tsc` with `src/v1/tsconfig.json` |
+| `bun run lint:v1` | Biome on `src/v1/`, then imports (nothing outside v1, folder contract, and v0 reaching v1 only through `@v1`), PropTypes and `ant-` checks |
+| `bun run test:v1` | v1 unit tests, then the guardrail fixtures in `test-fixtures/v1-boundary/` |
+
+The v0 ↔ v1 boundary and the banned imports are Biome rules in `biome.json`,
+so `biome ci src/` (CI) and editors report them too. The remaining checks are
+`src/v1/tsconfig.json` and `scripts/check-v1.mjs`.
diff --git a/frontend/src/v1/app/.gitkeep b/frontend/src/v1/app/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/components/patterns/.gitkeep b/frontend/src/v1/components/patterns/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/components/ui/.gitkeep b/frontend/src/v1/components/ui/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/hooks/.gitkeep b/frontend/src/v1/hooks/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/index.ts b/frontend/src/v1/index.ts
new file mode 100644
index 0000000000..48afca1c00
--- /dev/null
+++ b/frontend/src/v1/index.ts
@@ -0,0 +1,7 @@
+/*
+ * Public entry of the v1 frontend — the only v1 module v0 may import, as
+ * `@v1`. Lint rejects any other v0 → v1 import (see src/v1/README.md).
+ *
+ * Empty until the version switch (UN-4271) mounts v1 through it.
+ */
+export {};
diff --git a/frontend/src/v1/lib/.gitkeep b/frontend/src/v1/lib/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/pages/.gitkeep b/frontend/src/v1/pages/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/plugins/manifest.ts b/frontend/src/v1/plugins/manifest.ts
new file mode 100644
index 0000000000..c139d37fbf
--- /dev/null
+++ b/frontend/src/v1/plugins/manifest.ts
@@ -0,0 +1,6 @@
+/*
+ * Cloud overlay target. Empty in the public repository: the cloud build
+ * copies its v1 plugins into this folder. The manifest's shape and contents
+ * belong to UN-4285 and UN-4286.
+ */
+export const pluginManifest = [] as const;
diff --git a/frontend/src/v1/services/.gitkeep b/frontend/src/v1/services/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/shell/.gitkeep b/frontend/src/v1/shell/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/stores/.gitkeep b/frontend/src/v1/stores/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/styles/.gitkeep b/frontend/src/v1/styles/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/test/.gitkeep b/frontend/src/v1/test/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/frontend/src/v1/tsconfig.json b/frontend/src/v1/tsconfig.json
new file mode 100644
index 0000000000..0a10f9dbdb
--- /dev/null
+++ b/frontend/src/v1/tsconfig.json
@@ -0,0 +1,42 @@
+{
+  /*
+   * TypeScript config for the v1 frontend, checked by `bun run typecheck:v1`.
+   * It lives here rather than beside tsconfig.json so editors pick it up for
+   * files under src/v1; tsconfig.json and jsconfig.json exclude this folder.
+   *
+   * `allowJs: false` makes tsc skip a .js file rather than fail on it, so the
+   * "TypeScript only" rule is enforced by scripts/check-v1.mjs, which
+   * typecheck:v1 runs first.
+   */
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "jsx": "react-jsx",
+
+    "allowJs": false,
+    "noEmit": true,
+    /* Off so hand-written .d.ts under v1 are checked too; with it on, an
+     * unresolved name in one silently becomes `any`. */
+    "skipLibCheck": false,
+    "esModuleInterop": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "forceConsistentCasingInFileNames": true,
+
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+
+    /* Only `@v1` and `@v1/*` — deliberately no `@/*`, so an `@/` import
+     * fails typecheck as well as lint (`../` imports are caught by lint). The
+     * alias is also declared in vite.config.js and vitest.config.mjs. */
+    "paths": {
+      "@v1": ["./index.ts"],
+      "@v1/*": ["./*"]
+    }
+  },
+  "include": ["./**/*", "../../vite-env.d.ts"]
+}
diff --git a/frontend/test-fixtures/v1-boundary/boundary.fixtures.mjs b/frontend/test-fixtures/v1-boundary/boundary.fixtures.mjs
new file mode 100644
index 0000000000..c530319d89
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/boundary.fixtures.mjs
@@ -0,0 +1,422 @@
+/*
+ * Proves the v1 guardrails fail when they should and pass when they should.
+ * Run by `bun run test:v1` with `node --test`: it spawns the real tools, so it
+ * is not a vitest test (vitest.config.mjs excludes test-fixtures/).
+ *
+ * Each case builds a minimal throwaway copy of the frontend (biome.json,
+ * package.json, vite-env.d.ts, scripts/, the real src/v1 scaffold, a
+ * node_modules symlink and a git root), overlays the files under
+ * cases/<name>/ and runs the real package.json scripts, or a raw command,
+ * inside it. The known-bad files live here, outside src/, so CI lint, the
+ * pre-commit hook and typecheck never see them.
+ */
+import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { test } from "node:test";
+
+const FRONTEND = path.resolve(import.meta.dirname, "..", "..");
+const CASES_DIR = path.join(import.meta.dirname, "cases");
+const { scripts } = JSON.parse(
+  fs.readFileSync(path.join(FRONTEND, "package.json"), "utf8"),
+);
+
+/* Rows of "a | b | c" cells; blank lines and "#" comments are skipped. */
+function parseTable(text) {
+  return text
+    .split("\n")
+    .map((line) => line.trim())
+    .filter((line) => line && !line.startsWith("#"))
+    .map((line) => line.split("|").map((cell) => cell.trim()));
+}
+
+const sorted = (items) => items.toSorted((a, b) => a.localeCompare(b));
+
+/*
+ * One case per row: the folder under cases/ ("-" for the empty scaffold);
+ * the steps, joined by "+", each a package.json script name or a raw command
+ * (the v0 side has no v1 script); and a substring the tool output must
+ * contain, or "-" when the steps must pass.
+ */
+const CASES = parseTable(`
+  # The empty scaffold passes everything.
+  -                              | typecheck:v1 + lint:v1 | -
+  # Import boundary, v1 -> v0 (Biome).
+  v1-imports-v0-alias            | lint:v1         | v1 imports nothing outside src/v1
+  v1-imports-v0-relative         | lint:v1         | v1 imports nothing outside src/v1
+  v1-imports-root-absolute       | lint:v1         | v1 imports nothing outside src/v1
+  # Import boundary, v0 -> v1 (Biome).
+  v0-imports-v1-internal         | biome lint src/ | v0 may import only the v1 public entry
+  v0-imports-v1-relative         | biome lint src/ | v0 may import only the v1 public entry
+  v0-imports-v1-template         | lint:v1         | v0 may import only the v1 public entry
+  v0-imports-v1-entry            | biome lint src/ | -
+  # Banned under v1.
+  v1-prop-types                  | lint:v1         | PropTypes are not used
+  v1-prop-types-subpath          | lint:v1         | PropTypes are not used
+  v1-prop-types-assignment       | lint:v1         | No PropTypes under v1
+  v1-antd-import                 | lint:v1         | antd is not used under src/v1
+  v1-antd-subpath                | lint:v1         | antd is not used under src/v1
+  v1-styles-import-outside       | lint:v1         | v1 styles import nothing outside it
+  v1-styles-ant-class            | lint:v1         | No antd 'ant-' class names
+  v1-component-css-import        | lint:v1         | No component .css under src/v1
+  v1-component-css-file          | typecheck:v1    | No component style files
+  v1-ant-class-prefix            | lint:v1         | No antd 'ant-' class names
+  v1-ant-built-class             | lint:v1         | No antd 'ant-' class names
+  v1-explicit-any                | lint:v1         | noExplicitAny
+  # The v1 override must add to the shared rules, not replace them.
+  v1-base-rules-still-apply      | lint:v1         | noDoubleEquals
+  # TypeScript only, strict.
+  v1-js-file                     | typecheck:v1    | TypeScript only
+  v1-implicit-any                | typecheck:v1    | TS7006
+  v1-strict-null                 | typecheck:v1    | TS18048
+  v1-unused-local                | typecheck:v1    | TS6133
+  v1-unused-parameter            | typecheck:v1    | TS6133
+  # Folder taxonomy and contract (the full contract is the matrix below).
+  v1-outside-taxonomy            | typecheck:v1    | Outside the v1 folder taxonomy
+  v1-root-file                   | typecheck:v1    | Outside the v1 folder taxonomy
+  v1-ui-imports-services         | lint:v1         | components/ui/ may not import from services/
+  v1-page-imports-other-page     | lint:v1         | pages/projects/ may not import from pages/settings/
+  # Only test files may use test/, and being a test file allows nothing else.
+  v1-non-test-imports-test       | lint:v1         | components/ui/ may not import from test/
+  v1-test-file-imports-services  | lint:v1         | components/ui/ may not import from services/
+  v1-allowed-imports             | typecheck:v1 + lint:v1 | -
+`).map(([name, run, fails]) => ({
+  name: name === "-" ? null : name,
+  run: run.split(" + "),
+  fails: fails === "-" ? null : fails,
+}));
+
+function makeTree(caseName) {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), "v1-boundary-"));
+  for (const file of ["biome.json", "package.json", "vite-env.d.ts"]) {
+    fs.copyFileSync(path.join(FRONTEND, file), path.join(dir, file));
+  }
+  // Copied, not linked: check-v1.mjs finds src/v1 relative to itself.
+  fs.cpSync(path.join(FRONTEND, "scripts"), path.join(dir, "scripts"), {
+    recursive: true,
+  });
+  fs.cpSync(path.join(FRONTEND, "src", "v1"), path.join(dir, "src", "v1"), {
+    recursive: true,
+  });
+  fs.symlinkSync(
+    path.join(FRONTEND, "node_modules"),
+    path.join(dir, "node_modules"),
+    "dir",
+  );
+  if (caseName) {
+    fs.cpSync(path.join(CASES_DIR, caseName), dir, { recursive: true });
+  }
+  // biome.json enables VCS integration with `useIgnoreFile`, which needs an
+  // ignore file at the root.
+  fs.writeFileSync(path.join(dir, ".gitignore"), "node_modules\n");
+  return dir;
+}
+
+function removeTree(dir) {
+  // Unlink first so the recursive delete can never walk into node_modules.
+  fs.unlinkSync(path.join(dir, "node_modules"));
+  fs.rmSync(dir, { recursive: true, force: true });
+}
+
+function writeFile(dir, rel, content) {
+  const file = path.join(dir, rel);
+  fs.mkdirSync(path.dirname(file), { recursive: true });
+  fs.writeFileSync(file, content);
+}
+
+/*
+ * Runs the steps in order, stopping at the first failure. `output` holds only
+ * what the tools printed, so an expected message can never match the command
+ * text. A command that could not start at all is an error, not a "failure".
+ */
+function runAll(dir, run) {
+  let output = "";
+  let log = "";
+  for (const step of run) {
+    const command = scripts[step] ?? step;
+    const result = spawnSync("/bin/sh", ["-c", command], {
+      cwd: dir,
+      encoding: "utf8",
+      env: {
+        ...process.env,
+        NO_COLOR: "1",
+        PATH: `${path.join(dir, "node_modules", ".bin")}${path.delimiter}${process.env.PATH}`,
+      },
+    });
+    if (result.error || result.status === null) {
+      throw new Error(
+        `could not run "${command}": ${result.error ?? result.signal}`,
+      );
+    }
+    // 127: sh could not find the command, e.g. a tool missing from PATH.
+    assert.notEqual(result.status, 127, `command not found: ${command}`);
+    output += result.stdout + result.stderr;
+    log += `$ ${command}\n${result.stdout}${result.stderr}`;
+    if (result.status !== 0) {
+      return { ok: false, output, log };
+    }
+  }
+  return { ok: true, output, log };
+}
+
+/* Runs `check-v1.mjs --code` over generated files; returns the reported lines. */
+function checkCode(files) {
+  const dir = makeTree(null);
+  try {
+    for (const [rel, content] of Object.entries(files)) {
+      writeFile(dir, rel, content);
+    }
+    const { output } = runAll(dir, ["node scripts/check-v1.mjs --code"]);
+    return output.split("\n").filter((l) => l.startsWith("src/"));
+  } finally {
+    removeTree(dir);
+  }
+}
+
+/*
+ * The repository's Python `lib/` ignore rule also matches src/v1/lib/ and the
+ * fixtures' lib/ folders; .gitignore re-includes them. `--no-index` checks the
+ * rules even for files already tracked.
+ */
+test("no v1 or fixture file is git-ignored", () => {
+  const files = ["src/v1", "test-fixtures"].flatMap((top) =>
+    fs
+      .readdirSync(path.join(FRONTEND, top), {
+        recursive: true,
+        withFileTypes: true,
+      })
+      .filter((d) => d.isFile() && d.name !== ".DS_Store")
+      .map((d) => path.relative(FRONTEND, path.join(d.parentPath, d.name))),
+  );
+  // A lib/ folder anywhere under v1, not only the top-level one.
+  files.push("src/v1/pages/projects/lib/x.ts", "src/v1/lib/sub/lib/x.ts");
+  const gitArgs = ["check-ignore", "--no-index", "--stdin"];
+  const options = { cwd: FRONTEND, encoding: "utf8", input: files.join("\n") };
+  // git from PATH on purpose: this is a developer/CI test, and git has no
+  // fixed location across macOS and Linux.
+  const result = spawnSync("git", gitArgs, options); // NOSONAR
+  // Exit 1 means "nothing matched"; 0 means some file is ignored.
+  assert.equal(result.status, 1, `git-ignored:\n${result.stdout}`);
+});
+
+test("every case folder is listed", () => {
+  const listed = new Set(CASES.map((c) => c.name).filter(Boolean));
+  assert.deepEqual(sorted(fs.readdirSync(CASES_DIR)), sorted([...listed]));
+});
+
+for (const { name, run, fails } of CASES) {
+  const label = `${name ?? "empty scaffold"}: ${fails ? "fails" : "passes"} ${run.join(", ")}`;
+  test(label, () => {
+    const dir = makeTree(name);
+    try {
+      const { ok, output, log } = runAll(dir, run);
+      if (fails) {
+        assert.equal(ok, false, `expected a failure, got:\n${log}`);
+        assert.ok(output.includes(fails), `expected "${fails}" in:\n${log}`);
+      } else {
+        assert.equal(ok, true, log);
+      }
+    } finally {
+      removeTree(dir);
+    }
+  });
+}
+
+/*
+ * The folder contract, written out independently of check-v1.mjs so a typo
+ * in either shows up here. Source: the table in src/v1/README.md. Folders
+ * may always import themselves; pages/a and pages/b stand for two pages.
+ */
+const FOLDERS = {
+  entry: "",
+  app: "app",
+  "components/ui": "components/ui",
+  "components/patterns": "components/patterns",
+  shell: "shell",
+  "pages/a": "pages/a",
+  "pages/b": "pages/b",
+  services: "services",
+  stores: "stores",
+  hooks: "hooks",
+  lib: "lib",
+  styles: "styles",
+  plugins: "plugins",
+  test: "test",
+};
+const EVERYTHING = Object.keys(FOLDERS);
+const MAY_IMPORT = Object.fromEntries(
+  parseTable(`
+    app                 | *
+    plugins             | *
+    test                | *
+    pages/a             | components/ui components/patterns shell services stores hooks lib styles plugins
+    components/ui       | lib styles
+    components/patterns | components/ui lib services stores hooks
+    shell               | components/ui components/patterns services stores hooks lib
+    services            | lib
+    stores              | lib
+    hooks               | lib
+    lib                 |
+    styles              | lib
+  `).map(([from, to]) => [from, to === "*" ? EVERYTHING : to.split(/\s+/)]),
+);
+
+/* The file for one folder pair: it imports the target by file and by folder.
+ * The entry is a file, so it has only the one form. */
+function pairFile(to) {
+  const target = FOLDERS[to];
+  return to === "entry"
+    ? ['import "@v1";']
+    : [`import "@v1/${target}/target";`, `import "@v1/${target}";`];
+}
+
+/* One file per folder pair, and the problems check-v1 must report for them. */
+function contractMatrix() {
+  const files = {};
+  const expected = [];
+  for (const [from, allowed] of Object.entries(MAY_IMPORT)) {
+    for (const to of EVERYTHING) {
+      const rel = `src/v1/${FOLDERS[from]}/m-${to.replace("/", "-")}.ts`;
+      const imports = pairFile(to);
+      files[rel] = `${imports.join("\n")}\n`;
+      const denied = from !== to && !allowed.includes(to);
+      expected.push(
+        ...(denied ? imports : []).map(
+          (_, i) => `${rel}:${i + 1}: ${from}/ may not import from ${to}/`,
+        ),
+      );
+    }
+  }
+  return { files, expected };
+}
+
+test("folder contract: every folder pair, by file and by folder", () => {
+  const { files, expected } = contractMatrix();
+  const reported = checkCode(files).map((l) => l.replace(/ \(.*$/, ""));
+  assert.deepEqual(sorted(reported), sorted(expected));
+});
+
+test("folder contract: every import form is read", () => {
+  // Each file breaks the contract once (components/ui -> services).
+  const forms = {
+    static: 'import { a } from "@v1/services/a";',
+    multiline: 'import {\n  a,\n  b,\n} from "@v1/services/a";',
+    type: 'import type { A } from "@v1/services/a";',
+    inlineType: 'import { type A } from "@v1/services/a";',
+    sideEffect: 'import "@v1/services/a";',
+    namespace: 'import * as a from "@v1/services/a";',
+    exportFrom: 'export { a } from "@v1/services/a";',
+    exportStar: 'export * from "@v1/services/a";',
+    exportStarAs: 'export * as a from "@v1/services/a";',
+    dynamic: 'export const a = () => import("@v1/services/a");',
+    dynamicTemplate: "export const a = () => import(`@v1/services/a`);",
+    require: 'export const a = require("@v1/services/a");',
+    relative: 'import { a } from "./../../services/a";',
+    afterSlashStarInString:
+      'export const route = "/projects/*";\nimport { a } from "@v1/services/a";\n/** doc */',
+    afterSlashStarInComment:
+      '// matches /api/*\nimport { a } from "@v1/services/a";\n/** doc */',
+    afterDoubleSlashInString:
+      'const u = "a//b"; export { a } from "@v1/services/a";',
+    glob: 'export const a = import.meta.glob("@v1/services/*.ts");',
+    globArrayLater:
+      'export const a = import.meta.glob(["@v1/components/ui/*.tsx", "@v1/services/*.ts"]);',
+    afterTemplateExpression:
+      // biome-ignore lint/suspicious/noTemplateCurlyInString: source text containing a template literal.
+      'const t = `${"}"}/*`;\nimport { a } from "@v1/services/a";\n/** doc */',
+  };
+  const files = {};
+  for (const [form, code] of Object.entries(forms)) {
+    files[`src/v1/components/ui/${form}.ts`] = `${code}\n`;
+  }
+  const reported = checkCode(files);
+  for (const form of Object.keys(forms)) {
+    const file = `src/v1/components/ui/${form}.ts:`;
+    assert.ok(
+      reported.some((l) => l.startsWith(file)),
+      `${form}: not reported\n${reported.join("\n")}`,
+    );
+  }
+});
+
+test("a symlinked file under v1 fails typecheck:v1", () => {
+  const dir = makeTree(null);
+  try {
+    fs.symlinkSync(
+      path.join(dir, "vite-env.d.ts"),
+      path.join(dir, "src", "v1", "lib", "linked.d.ts"),
+    );
+    const { ok, output, log } = runAll(dir, ["typecheck:v1"]);
+    assert.equal(ok, false, log);
+    assert.ok(output.includes("No symlinks under v1"), log);
+  } finally {
+    removeTree(dir);
+  }
+});
+
+test("v1 imports nothing outside src/v1, in any spelling", () => {
+  const specs = [
+    "@/helpers/x",
+    "../helpers/x",
+    "..",
+    "./../../helpers/x",
+    "/src/assets/logo.svg",
+    "src/helpers/x",
+  ];
+  const files = {};
+  specs.forEach((spec, i) => {
+    files[`src/v1/lib/outside-${i}.ts`] =
+      `export const a = () => import(\`${spec}\`);\n`;
+  });
+  const reported = checkCode(files);
+  specs.forEach((spec, i) => {
+    assert.ok(
+      reported.some(
+        (l) =>
+          l.startsWith(`src/v1/lib/outside-${i}.ts:`) &&
+          l.includes("is outside src/v1"),
+      ),
+      `'${spec}': not reported\n${reported.join("\n")}`,
+    );
+  });
+});
+
+test("v0 reaches v1 only through @v1, in any form", () => {
+  const denied = {
+    "static.jsx": 'import x from "@v1/lib/x";',
+    "template.jsx": "export const a = () => import(`@v1/plugins/manifest`);",
+    "glob.jsx": 'export const a = import.meta.glob("@v1/pages/*/index.ts");',
+    "globArrayLater.jsx":
+      'export const a = import.meta.glob(["./*.jsx", "../v1/lib/*.ts"]);',
+    "require.jsx": 'export const a = require("../v1/lib/x");',
+    "aliasV0.jsx": 'export const a = () => import("@/v1/lib/x");',
+    "srcPath.jsx": 'export const a = () => import("src/v1/lib/x");',
+    "relativeEntry.jsx": 'import "../v1";',
+    "styles.css": '@import "../v1/styles/tokens.css";',
+  };
+  const allowed = {
+    "entry.jsx": 'import "@v1";',
+    "entryTemplate.jsx": "export const a = () => import(`@v1`);",
+    "v0Only.jsx": 'import x from "../helpers/x";\nexport const y = x;',
+  };
+  const files = {};
+  for (const [name, code] of Object.entries({ ...denied, ...allowed })) {
+    files[`src/pages/${name}`] = `${code}\n`;
+  }
+  const reported = checkCode(files);
+  const v0Lines = reported.filter((l) => l.startsWith("src/pages/"));
+  for (const name of Object.keys(denied)) {
+    assert.ok(
+      v0Lines.some((l) => l.startsWith(`src/pages/${name}:`)),
+      `${name}: not reported\n${reported.join("\n")}`,
+    );
+  }
+  for (const name of Object.keys(allowed)) {
+    assert.ok(
+      !v0Lines.some((l) => l.startsWith(`src/pages/${name}:`)),
+      `${name}: reported but allowed\n${reported.join("\n")}`,
+    );
+  }
+});
diff --git a/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-entry/src/pages/Ok.jsx b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-entry/src/pages/Ok.jsx
new file mode 100644
index 0000000000..8e96182e95
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-entry/src/pages/Ok.jsx
@@ -0,0 +1 @@
+import "@v1";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-internal/src/pages/Bad.jsx b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-internal/src/pages/Bad.jsx
new file mode 100644
index 0000000000..ecddfc6910
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-internal/src/pages/Bad.jsx
@@ -0,0 +1,3 @@
+import { pluginManifest } from "@v1/plugins/manifest";
+
+export const manifestSize = () => pluginManifest.length;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-relative/src/pages/Bad.jsx b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-relative/src/pages/Bad.jsx
new file mode 100644
index 0000000000..953cb550c6
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-relative/src/pages/Bad.jsx
@@ -0,0 +1,3 @@
+import { pluginManifest } from "../v1/plugins/manifest";
+
+export const manifestSize = () => pluginManifest.length;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-template/src/pages/Bad.jsx b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-template/src/pages/Bad.jsx
new file mode 100644
index 0000000000..278db55314
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v0-imports-v1-template/src/pages/Bad.jsx
@@ -0,0 +1 @@
+export const loadManifest = () => import(`@v1/plugins/manifest`);
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.test.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.test.ts
new file mode 100644
index 0000000000..1cb7e9a430
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.test.ts
@@ -0,0 +1,4 @@
+import { renderLabel } from "@v1/test/render";
+import { label } from "./Label";
+
+export const rendered = renderLabel(label("ok"));
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.ts
new file mode 100644
index 0000000000..ef8a7487be
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Label.ts
@@ -0,0 +1,3 @@
+import { upper } from "@v1/lib/format";
+
+export const label = (text: string): string => upper(text);
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Tag.tsx b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Tag.tsx
new file mode 100644
index 0000000000..07afb25230
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/components/ui/Tag.tsx
@@ -0,0 +1,7 @@
+import { upper } from "@v1/lib/format";
+
+type TagProps = Readonly<{ label: string }>;
+
+export function Tag({ label }: TagProps) {
+  return <span>{upper(label)}</span>;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/lib/format.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/lib/format.ts
new file mode 100644
index 0000000000..ee479a8063
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/lib/format.ts
@@ -0,0 +1 @@
+export const upper = (value: string): string => value.toUpperCase();
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.test.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.test.ts
new file mode 100644
index 0000000000..73138391d0
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.test.ts
@@ -0,0 +1,4 @@
+import { renderLabel } from "@v1/test/render";
+import { title } from "./title";
+
+export const rendered = renderLabel(title);
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.ts
new file mode 100644
index 0000000000..b902577b52
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/title.ts
@@ -0,0 +1 @@
+export const title = "Projects";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/view/heading.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/view/heading.ts
new file mode 100644
index 0000000000..671f792f33
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/pages/projects/view/heading.ts
@@ -0,0 +1,4 @@
+import { label } from "@v1/components/ui/Label";
+import { title } from "@v1/pages/projects/title";
+
+export const heading = label(title);
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/index.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/index.ts
new file mode 100644
index 0000000000..7ab5ff7d43
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/index.ts
@@ -0,0 +1,3 @@
+import "@v1/styles/tokens.css";
+
+export const themed = true;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/tokens.css b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/tokens.css
new file mode 100644
index 0000000000..ac38c30204
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/styles/tokens.css
@@ -0,0 +1,3 @@
+:root {
+  --v1-accent: #000;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/test/render.ts b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/test/render.ts
new file mode 100644
index 0000000000..858e72d057
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-allowed-imports/src/v1/test/render.ts
@@ -0,0 +1 @@
+export const renderLabel = (text: string): string => text;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-ant-built-class/src/v1/components/ui/Tag.ts b/frontend/test-fixtures/v1-boundary/cases/v1-ant-built-class/src/v1/components/ui/Tag.ts
new file mode 100644
index 0000000000..758e2c7350
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-ant-built-class/src/v1/components/ui/Tag.ts
@@ -0,0 +1 @@
+export const tagClass = (kind: string): string => `ant-${kind}`;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-ant-class-prefix/src/v1/components/ui/Button.ts b/frontend/test-fixtures/v1-boundary/cases/v1-ant-class-prefix/src/v1/components/ui/Button.ts
new file mode 100644
index 0000000000..a87d0cde10
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-ant-class-prefix/src/v1/components/ui/Button.ts
@@ -0,0 +1 @@
+export const buttonClass = "ant-btn primary";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-antd-import/src/v1/components/ui/Button.ts b/frontend/test-fixtures/v1-boundary/cases/v1-antd-import/src/v1/components/ui/Button.ts
new file mode 100644
index 0000000000..1973bc6c11
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-antd-import/src/v1/components/ui/Button.ts
@@ -0,0 +1,3 @@
+import { Button } from "antd";
+
+export const buttonName = Button.name;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-antd-subpath/src/v1/components/ui/Button.ts b/frontend/test-fixtures/v1-boundary/cases/v1-antd-subpath/src/v1/components/ui/Button.ts
new file mode 100644
index 0000000000..be5137ace6
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-antd-subpath/src/v1/components/ui/Button.ts
@@ -0,0 +1,3 @@
+import Button from "antd/es/button";
+
+export const AntButton = Button;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-base-rules-still-apply/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-base-rules-still-apply/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..32f9a0a998
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-base-rules-still-apply/src/v1/lib/bad.ts
@@ -0,0 +1 @@
+export const same = (a: number, b: number): boolean => a == b;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-component-css-file/src/v1/components/ui/Badge.css b/frontend/test-fixtures/v1-boundary/cases/v1-component-css-file/src/v1/components/ui/Badge.css
new file mode 100644
index 0000000000..63bd92461e
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-component-css-file/src/v1/components/ui/Badge.css
@@ -0,0 +1,3 @@
+.badge {
+  color: red;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-component-css-import/src/v1/components/ui/Badge.tsx b/frontend/test-fixtures/v1-boundary/cases/v1-component-css-import/src/v1/components/ui/Badge.tsx
new file mode 100644
index 0000000000..be8a92895c
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-component-css-import/src/v1/components/ui/Badge.tsx
@@ -0,0 +1,3 @@
+import "./Badge.css";
+
+export const badge = "badge";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-explicit-any/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-explicit-any/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..6724498208
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-explicit-any/src/v1/lib/bad.ts
@@ -0,0 +1 @@
+export const value: any = 1;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-implicit-any/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-implicit-any/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..cf9f27088d
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-implicit-any/src/v1/lib/bad.ts
@@ -0,0 +1,3 @@
+export function identity(value) {
+  return value;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-imports-root-absolute/src/v1/lib/logo.ts b/frontend/test-fixtures/v1-boundary/cases/v1-imports-root-absolute/src/v1/lib/logo.ts
new file mode 100644
index 0000000000..b306ec899d
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-imports-root-absolute/src/v1/lib/logo.ts
@@ -0,0 +1,3 @@
+import logo from "/src/assets/logo.svg";
+
+export const logoUrl = logo;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-alias/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-alias/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..4f64a2f1e2
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-alias/src/v1/lib/bad.ts
@@ -0,0 +1,3 @@
+import { getBaseUrl } from "@/helpers/GetStaticData";
+
+export const base = () => getBaseUrl();
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-relative/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-relative/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..acba160b3c
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-imports-v0-relative/src/v1/lib/bad.ts
@@ -0,0 +1,3 @@
+import { getBaseUrl } from "../../helpers/GetStaticData";
+
+export const base = () => getBaseUrl();
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-js-file/src/v1/lib/legacy.js b/frontend/test-fixtures/v1-boundary/cases/v1-js-file/src/v1/lib/legacy.js
new file mode 100644
index 0000000000..7e15a4a640
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-js-file/src/v1/lib/legacy.js
@@ -0,0 +1 @@
+export const legacy = 1;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/components/ui/Helper.ts b/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/components/ui/Helper.ts
new file mode 100644
index 0000000000..3ae7c334e1
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/components/ui/Helper.ts
@@ -0,0 +1,3 @@
+import { render } from "@v1/test/render";
+
+export const helper = render("x");
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/test/render.ts b/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/test/render.ts
new file mode 100644
index 0000000000..a70ecac7f4
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-non-test-imports-test/src/v1/test/render.ts
@@ -0,0 +1 @@
+export const render = (text: string): string => text;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-outside-taxonomy/src/v1/widgets/thing.ts b/frontend/test-fixtures/v1-boundary/cases/v1-outside-taxonomy/src/v1/widgets/thing.ts
new file mode 100644
index 0000000000..61483b3477
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-outside-taxonomy/src/v1/widgets/thing.ts
@@ -0,0 +1 @@
+export const thing = 1;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/projects/index.ts b/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/projects/index.ts
new file mode 100644
index 0000000000..f6e2ea9482
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/projects/index.ts
@@ -0,0 +1,3 @@
+import { settingsTitle } from "@v1/pages/settings";
+
+export const title = `Projects · ${settingsTitle}`;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/settings/index.ts b/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/settings/index.ts
new file mode 100644
index 0000000000..317694fcb8
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-page-imports-other-page/src/v1/pages/settings/index.ts
@@ -0,0 +1 @@
+export const settingsTitle = "Settings";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-assignment/src/v1/components/ui/Box.ts b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-assignment/src/v1/components/ui/Box.ts
new file mode 100644
index 0000000000..e6e9ef769a
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-assignment/src/v1/components/ui/Box.ts
@@ -0,0 +1,4 @@
+export function Box(): null {
+  return null;
+}
+Box.propTypes = {};
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-subpath/src/v1/components/ui/Badge.ts b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-subpath/src/v1/components/ui/Badge.ts
new file mode 100644
index 0000000000..cec0f63a16
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types-subpath/src/v1/components/ui/Badge.ts
@@ -0,0 +1,3 @@
+import PropTypes from "prop-types/index";
+
+export const badgeShape = PropTypes.string;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-prop-types/src/v1/components/ui/Badge.tsx b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types/src/v1/components/ui/Badge.tsx
new file mode 100644
index 0000000000..64c5471dfb
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-prop-types/src/v1/components/ui/Badge.tsx
@@ -0,0 +1,3 @@
+import PropTypes from "prop-types";
+
+export const badgeShape = PropTypes.string;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-root-file/src/v1/main.ts b/frontend/test-fixtures/v1-boundary/cases/v1-root-file/src/v1/main.ts
new file mode 100644
index 0000000000..c8d21f3f94
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-root-file/src/v1/main.ts
@@ -0,0 +1 @@
+export const main = 1;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-strict-null/src/v1/lib/length.ts b/frontend/test-fixtures/v1-boundary/cases/v1-strict-null/src/v1/lib/length.ts
new file mode 100644
index 0000000000..b42e7ba01f
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-strict-null/src/v1/lib/length.ts
@@ -0,0 +1 @@
+export const length = (value: string | undefined): number => value.length;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-styles-ant-class/src/v1/styles/global.css b/frontend/test-fixtures/v1-boundary/cases/v1-styles-ant-class/src/v1/styles/global.css
new file mode 100644
index 0000000000..d077e5ea0f
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-styles-ant-class/src/v1/styles/global.css
@@ -0,0 +1,3 @@
+.ant-btn {
+  color: red;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-styles-import-outside/src/v1/styles/global.css b/frontend/test-fixtures/v1-boundary/cases/v1-styles-import-outside/src/v1/styles/global.css
new file mode 100644
index 0000000000..e5971a61a2
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-styles-import-outside/src/v1/styles/global.css
@@ -0,0 +1 @@
+@import "../../index.css";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/components/ui/Link.test.ts b/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/components/ui/Link.test.ts
new file mode 100644
index 0000000000..a84d47e627
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/components/ui/Link.test.ts
@@ -0,0 +1,3 @@
+import { projectsUrl } from "@v1/services/projects";
+
+export const url = projectsUrl;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/services/projects.ts b/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/services/projects.ts
new file mode 100644
index 0000000000..934524c2f4
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-test-file-imports-services/src/v1/services/projects.ts
@@ -0,0 +1 @@
+export const projectsUrl = "/api/v1/projects";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/components/ui/ProjectLink.tsx b/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/components/ui/ProjectLink.tsx
new file mode 100644
index 0000000000..8024a7c0bb
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/components/ui/ProjectLink.tsx
@@ -0,0 +1,3 @@
+import { projectsUrl } from "@v1/services/projects";
+
+export const href = `${projectsUrl}/`;
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/services/projects.ts b/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/services/projects.ts
new file mode 100644
index 0000000000..934524c2f4
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-ui-imports-services/src/v1/services/projects.ts
@@ -0,0 +1 @@
+export const projectsUrl = "/api/v1/projects";
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-unused-local/src/v1/lib/bad.ts b/frontend/test-fixtures/v1-boundary/cases/v1-unused-local/src/v1/lib/bad.ts
new file mode 100644
index 0000000000..ac320e04db
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-unused-local/src/v1/lib/bad.ts
@@ -0,0 +1,4 @@
+export function double(value: number): number {
+  const unused = 1;
+  return value * 2;
+}
diff --git a/frontend/test-fixtures/v1-boundary/cases/v1-unused-parameter/src/v1/lib/one.ts b/frontend/test-fixtures/v1-boundary/cases/v1-unused-parameter/src/v1/lib/one.ts
new file mode 100644
index 0000000000..58bdb81c4e
--- /dev/null
+++ b/frontend/test-fixtures/v1-boundary/cases/v1-unused-parameter/src/v1/lib/one.ts
@@ -0,0 +1 @@
+export const one = (value: number): number => 1;
diff --git a/frontend/tsconfig.json b/frontend/tsconfig.json
index f7e7014f49..779791063e 100644
--- a/frontend/tsconfig.json
+++ b/frontend/tsconfig.json
@@ -40,9 +40,12 @@
      * `baseUrl` was removed in TypeScript 6, so the paths are relative to
      * this file's directory. */
     "paths": {
-      "@/*": ["./src/*"]
+      "@/*": ["./src/*"],
+      /* v0 may import only the v1 public entry, so only that is mapped. */
+      "@v1": ["./src/v1/index.ts"]
     }
   },
   "include": ["src/**/*.ts", "src/**/*.tsx", "src/**/*.d.ts"],
-  "exclude": ["node_modules", "build", "dist"]
+  /* src/v1 is checked by src/v1/tsconfig.json under stricter settings. */
+  "exclude": ["node_modules", "build", "dist", "src/v1"]
 }
diff --git a/frontend/vite.config.js b/frontend/vite.config.js
index af124153fc..fecc6b40f5 100644
--- a/frontend/vite.config.js
+++ b/frontend/vite.config.js
@@ -184,6 +184,9 @@ export default defineConfig(({ mode }) => {
     resolve: {
       alias: {
         "@": path.resolve(import.meta.dirname, "./src"),
+        // v1 frontend. Also in src/v1/tsconfig.json and vitest.config.mjs;
+        // tsconfig.json/jsconfig.json map only the entry, for v0.
+        "@v1": path.resolve(import.meta.dirname, "./src/v1"),
       },
     },
 
diff --git a/frontend/vitest.config.mjs b/frontend/vitest.config.mjs
index 128c7f042f..25cbe07f68 100644
--- a/frontend/vitest.config.mjs
+++ b/frontend/vitest.config.mjs
@@ -94,6 +94,8 @@ export default defineConfig({
   resolve: {
     alias: {
       "@": path.resolve(import.meta.dirname, "./src"),
+      // Mirror of the `@v1` alias in vite.config.js.
+      "@v1": path.resolve(import.meta.dirname, "./src/v1"),
     },
   },
   test: {
@@ -107,8 +109,16 @@ export default defineConfig({
      * The Playwright suite (the rig's `ui` group) lives in `tests/e2e/ui`, out
      * of this tree entirely, so vitest's default glob no longer reaches it.
      * `build/` is listed because a production build lands there and its
-     * bundled chunks would otherwise be walked.
+     * bundled chunks would otherwise be walked. `test-fixtures/` holds
+     * known-good and known-bad trees (some with `*.test.ts` files) that
+     * test-fixtures/v1-boundary/boundary.fixtures.mjs lints and type-checks;
+     * they are inputs, not tests.
      */
-    exclude: ["**/node_modules/**", "**/dist/**", "**/build/**"],
+    exclude: [
+      "**/node_modules/**",
+      "**/dist/**",
+      "**/build/**",
+      "test-fixtures/**",
+    ],
   },
 });