diff --git a/packages/cli/src/migrations/mode-functions.ts b/packages/cli/src/migrations/mode-functions.ts
new file mode 100644
index 00000000..31f8c2e3
--- /dev/null
+++ b/packages/cli/src/migrations/mode-functions.ts
@@ -0,0 +1,274 @@
+/**
+ * Migration: move mode-scoped helpers out of legacy `ssr { functions { … } }`
+ * / `client { functions { … } }` blocks into the page-level `functions { }`
+ * block, tagged `shared`.
+ *
+ * IMPORTANT: this is a text-level transform, not a parse-and-rewrite, for the
+ * same reason as `apis-block.ts`: the `@wrnexus/syntax` parser deliberately
+ * THROWS a `ParseError` on `ssr { … }` / `client { … }` data blocks — that
+ * legacy syntax is exactly what this migration exists to read, so it cannot
+ * be reached by parsing first. Instead this scans the source with the same
+ * balanced-brace technique used throughout `update.ts` (`findMatching`), and
+ * only parses the RESULT, as a validity check.
+ */
+
+import { parse } from "@wrnexus/syntax";
+
+/** Balanced-brace scan: returns the index of the brace matching `open`, or -1. */
+function findMatching(source: string, open: number, openChar = "{", closeChar = "}"): number {
+  let depth = 0;
+  let quote = "";
+  for (let index = open; index < source.length; index++) {
+    const char = source[index]!;
+    if (quote) {
+      if (char === "\\") index++;
+      else if (char === quote) quote = "";
+      continue;
+    }
+    if (char === '"' || char === "'" || char === "`") quote = char;
+    else if (char === openChar) depth++;
+    else if (char === closeChar && --depth === 0) return index;
+  }
+  return -1;
+}
+
+interface ModeBlock {
+  mode: "ssr" | "client";
+  /** Start of the `ssr`/`client` keyword. */
+  start: number;
+  /** One past the block's closing `}`. */
+  end: number;
+  bodyStart: number;
+  bodyEnd: number;
+}
+
+/** Find page-level `ssr { … }` / `client { … }` data blocks (not `state`/hydrate forms). */
+function findModeBlocks(source: string): ModeBlock[] {
+  const blocks: ModeBlock[] = [];
+  const header = /\b(ssr|client)\s*\{/g;
+  let match: RegExpExecArray | null;
+  while ((match = header.exec(source))) {
+    const open = match.index + match[0].length - 1;
+    const close = findMatching(source, open);
+    if (close < 0) {
+      throw new Error(`unterminated "${match[1]} {" block at offset ${match.index}`);
+    }
+    blocks.push({
+      mode: match[1] as "ssr" | "client",
+      start: match.index,
+      end: close + 1,
+      bodyStart: open + 1,
+      bodyEnd: close,
+    });
+    header.lastIndex = close + 1;
+  }
+  return blocks;
+}
+
+interface FunctionsSubBlock {
+  /** Offsets relative to the mode block's body. */
+  localStart: number;
+  localEnd: number;
+  bodyStart: number;
+  bodyEnd: number;
+}
+
+/** Find `functions { … }` sub-blocks inside a mode-block body. */
+function findFunctionsSubBlocks(body: string): FunctionsSubBlock[] {
+  const blocks: FunctionsSubBlock[] = [];
+  const header = /\bfunctions\s*\{/g;
+  let match: RegExpExecArray | null;
+  while ((match = header.exec(body))) {
+    const open = match.index + match[0].length - 1;
+    const close = findMatching(body, open);
+    if (close < 0) {
+      throw new Error(`unterminated "functions {" block at offset ${match.index}`);
+    }
+    blocks.push({
+      localStart: match.index,
+      localEnd: close + 1,
+      bodyStart: open + 1,
+      bodyEnd: close,
+    });
+    header.lastIndex = close + 1;
+  }
+  return blocks;
+}
+
+interface FunctionEntry {
+  name: string;
+  /** `function name(...) { ... }` text, with any leading runtime keyword stripped. */
+  text: string;
+}
+
+/** Find `[client|server|shared] function <name>(...) { ... }` entries inside a functions-block body. */
+function findFunctionEntries(body: string): FunctionEntry[] {
+  const entries: FunctionEntry[] = [];
+  const header = /\b(?:(?:client|server|shared)\s+)?function\s+([A-Za-z_$][\w$]*)\s*\(/g;
+  let match: RegExpExecArray | null;
+  while ((match = header.exec(body))) {
+    const parenOpen = match.index + match[0].length - 1;
+    const parenClose = findMatching(body, parenOpen, "(", ")");
+    if (parenClose < 0) {
+      throw new Error(`unterminated function parameter list at offset ${match.index}`);
+    }
+    const braceOpen = body.indexOf("{", parenClose + 1);
+    if (braceOpen < 0) {
+      throw new Error(`unterminated function body at offset ${match.index}`);
+    }
+    const braceClose = findMatching(body, braceOpen);
+    if (braceClose < 0) {
+      throw new Error(`unterminated function body at offset ${match.index}`);
+    }
+    const localStart = match.index;
+    const localEnd = braceClose + 1;
+    const text = body.slice(localStart, localEnd).replace(/^(client|server|shared)\s+/, "");
+    entries.push({ name: match[1]!, text });
+    header.lastIndex = localEnd;
+  }
+  return entries;
+}
+
+interface Edit {
+  start: number;
+  end: number;
+  replacement: string;
+}
+
+function applyEdits(source: string, edits: Edit[]): string {
+  const sorted = [...edits].sort((a, b) => a.start - b.start);
+  let output = "";
+  let cursor = 0;
+  for (const edit of sorted) {
+    output += source.slice(cursor, edit.start) + edit.replacement;
+    cursor = edit.end;
+  }
+  output += source.slice(cursor);
+  return output;
+}
+
+export function migrateModeFunctions(
+  source: string,
+): { source: string; changed: boolean } | { skip: string } {
+  const blocks = findModeBlocks(source);
+  if (blocks.length === 0) return { source, changed: false };
+
+  const allEntries: FunctionEntry[] = [];
+  const nameMode = new Map<string, "ssr" | "client">();
+  const perBlockFuncBlocks = new Map<ModeBlock, FunctionsSubBlock[]>();
+
+  for (const block of blocks) {
+    const body = source.slice(block.bodyStart, block.bodyEnd);
+    const funcBlocks = findFunctionsSubBlocks(body);
+    if (funcBlocks.length === 0) continue;
+
+    for (const funcBlock of funcBlocks) {
+      const funcBody = body.slice(funcBlock.bodyStart, funcBlock.bodyEnd);
+      for (const entry of findFunctionEntries(funcBody)) {
+        const existingMode = nameMode.get(entry.name);
+        if (existingMode && existingMode !== block.mode) {
+          return {
+            skip: `function '${entry.name}' is declared in both ssr and client — merge them by hand before this migration can run`,
+          };
+        }
+        nameMode.set(entry.name, block.mode);
+        allEntries.push(entry);
+      }
+    }
+    perBlockFuncBlocks.set(block, funcBlocks);
+  }
+
+  if (allEntries.length === 0) return { source, changed: false };
+
+  // Locate an existing page-level `functions { }` block, i.e. one that is not
+  // inside any ssr/client mode block.
+  const insideAMode = (index: number) =>
+    blocks.some((block) => index >= block.start && index < block.end);
+
+  let existingFunctions: { bodyStart: number; bodyEnd: number } | null = null;
+  {
+    const header = /\bfunctions\s*\{/g;
+    let match: RegExpExecArray | null;
+    while ((match = header.exec(source))) {
+      if (insideAMode(match.index)) continue;
+      const open = match.index + match[0].length - 1;
+      const close = findMatching(source, open);
+      if (close < 0) throw new Error(`unterminated "functions {" block at offset ${match.index}`);
+      existingFunctions = { bodyStart: open + 1, bodyEnd: close };
+      break;
+    }
+  }
+
+  if (existingFunctions) {
+    const existingBody = source.slice(existingFunctions.bodyStart, existingFunctions.bodyEnd);
+    for (const entry of allEntries) {
+      if (new RegExp(`\\bfunction\\s+${entry.name}\\b`).test(existingBody)) {
+        return {
+          skip: `'${entry.name}' already exists in the page-level functions block`,
+        };
+      }
+    }
+  }
+
+  const designatedBlock = blocks.find((block) => perBlockFuncBlocks.has(block));
+  const edits: Edit[] = [];
+  // True when a mode block keeps non-function content (e.g. `api` entries)
+  // after its functions are extracted. The grammar rejects any `ssr {}` /
+  // `client {}` wrapper outright, regardless of what's inside, so such a
+  // leftover wrapper cannot parse until move-api-blocks removes it in the
+  // same `wrnexus update` run. Validating with `parse` here would therefore
+  // always fail on a case this migration is specifically meant to unblock.
+  let leavesModeWrapper = false;
+
+  for (const block of blocks) {
+    const funcBlocks = perBlockFuncBlocks.get(block);
+    if (!funcBlocks) continue; // block had no functions sub-block; leave it untouched entirely
+
+    const body = source.slice(block.bodyStart, block.bodyEnd);
+    let remainder = body;
+    for (const funcBlock of [...funcBlocks].reverse()) {
+      remainder = remainder.slice(0, funcBlock.localStart) + remainder.slice(funcBlock.localEnd);
+    }
+    const isEmpty = remainder.trim() === "";
+    if (!isEmpty) leavesModeWrapper = true;
+
+    if (block === designatedBlock && !existingFunctions) {
+      const funcsBody = allEntries.map((entry) => `    shared ${entry.text}`).join("\n\n");
+      const funcsBlockText = `functions {\n${funcsBody}\n  }`;
+      const replacement = isEmpty
+        ? funcsBlockText
+        : `${funcsBlockText}\n\n  ${block.mode} {${remainder}}`;
+      edits.push({ start: block.start, end: block.end, replacement });
+    } else {
+      const replacement = isEmpty ? "" : `${block.mode} {${remainder}}`;
+      edits.push({ start: block.start, end: block.end, replacement });
+    }
+  }
+
+  if (existingFunctions) {
+    const existingBody = source.slice(existingFunctions.bodyStart, existingFunctions.bodyEnd);
+    const additions = allEntries.map((entry) => `    shared ${entry.text}`).join("\n\n");
+    const mergedBody = `${existingBody.replace(/\s*$/, "")}\n\n${additions}\n  `;
+    edits.push({
+      start: existingFunctions.bodyStart,
+      end: existingFunctions.bodyEnd,
+      replacement: mergedBody,
+    });
+  }
+
+  let after = applyEdits(source, edits);
+  after = after.replace(/[ \t]+\n/g, "\n").replace(/\n{3,}/g, "\n\n");
+
+  if (after === source) return { source, changed: false };
+
+  if (!leavesModeWrapper) {
+    try {
+      parse(after);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      throw new Error(`mode-functions migration produced source that failed to parse: ${message}`);
+    }
+  }
+
+  return { source: after, changed: true };
+}
diff --git a/packages/cli/src/update.ts b/packages/cli/src/update.ts
index 342ba661..57aa5b23 100644
--- a/packages/cli/src/update.ts
+++ b/packages/cli/src/update.ts
@@ -35,6 +35,7 @@ import { formatWrn, parse } from "@wrnexus/syntax";
 import { AI_GUIDE, CLAUDE_MD } from "./ai-guide.ts";
 import { inspectProject, type DoctorCheck } from "./doctor.ts";
 import { migrateApisBlock } from "./migrations/apis-block.ts";
+import { migrateModeFunctions } from "./migrations/mode-functions.ts";
 import { generateApplicationTypes } from "./types.ts";
 
 /** The version of the CLI currently running (its own package.json). */
@@ -869,6 +870,43 @@ const MIGRATIONS: Migration[] = [
       if (!ctx.dryRun) writeFileSync(file, after, "utf8");
     },
   },
+  {
+    version: "0.9.0",
+    id: "move-mode-functions",
+    description:
+      "Move mode-scoped helpers out of legacy ssr/client functions blocks into a page-level shared functions block",
+    apply(ctx) {
+      const appDirectory = join(ctx.appRoot, "app");
+      if (!existsSync(appDirectory)) return;
+
+      for (const file of walkProjectFiles(appDirectory, ".wrn")) {
+        const relativeFile = relative(ctx.appRoot, file).replace(/\\/g, "/");
+        const before = readFileSync(file, "utf8");
+
+        let result: ReturnType<typeof migrateModeFunctions>;
+        try {
+          result = migrateModeFunctions(before);
+        } catch (error) {
+          const message = error instanceof Error ? error.message.split("\n", 1)[0] : String(error);
+          ctx.report.parseFailures.push(`${relativeFile}: ${message}`);
+          ctx.log(`! ${relativeFile}: left unchanged because the mode-functions migration failed`);
+          continue;
+        }
+
+        if ("skip" in result) {
+          ctx.report.needsReview.push(`${relativeFile}: ${result.skip}`);
+          continue;
+        }
+        if (!result.changed) continue;
+
+        ctx.report.changedAutomatically.push(
+          `${relativeFile}: moved mode-scoped helpers into functions { shared … }`,
+        );
+        ctx.log(`~ ${relativeFile}: moved mode-scoped helpers into functions { shared … }`);
+        if (!ctx.dryRun) writeFileSync(file, result.source, "utf8");
+      }
+    },
+  },
   {
     version: "0.9.0",
     id: "move-api-blocks",
diff --git a/packages/cli/test/migrate-mode-functions.test.ts b/packages/cli/test/migrate-mode-functions.test.ts
new file mode 100644
index 00000000..e15dc885
--- /dev/null
+++ b/packages/cli/test/migrate-mode-functions.test.ts
@@ -0,0 +1,132 @@
+import { afterEach, expect, test } from "bun:test";
+import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { migrateModeFunctions } from "../src/migrations/mode-functions.ts";
+import { updateApp } from "../src/update.ts";
+
+const SOURCE = `page Hello {
+  ssr {
+    functions {
+      function userNames(users) {
+        return users.map((user) => user.name).join(", ")
+      }
+    }
+  }
+
+  view { <main>x</main> }
+}
+`;
+
+test("a mode helper becomes a shared function", () => {
+  const result = migrateModeFunctions(SOURCE) as { source: string; changed: boolean };
+
+  expect(result.changed).toBe(true);
+  expect(result.source).toContain("shared function userNames");
+  expect(result.source).not.toContain("ssr {");
+});
+
+test("running it again changes nothing", () => {
+  const once = (migrateModeFunctions(SOURCE) as { source: string }).source;
+  const twice = migrateModeFunctions(once) as { changed: boolean; source: string };
+
+  expect(twice.changed).toBe(false);
+  expect(twice.source).toBe(once);
+});
+
+test("a name that already exists at page level is skipped with a reason", () => {
+  const clash = `page P {
+  functions { shared function userNames() { return "" } }
+  ssr { functions { function userNames(users) { return "" } } }
+  view { <main>x</main> }
+}
+`;
+  const result = migrateModeFunctions(clash) as { skip: string };
+
+  expect(result.skip).toContain("userNames");
+});
+
+test("a helper body containing a brace inside a string literal survives", () => {
+  const source = `page Hello {
+  ssr {
+    functions {
+      function label(user) {
+        return user.name + " {tag}"
+      }
+    }
+  }
+
+  view { <main>x</main> }
+}
+`;
+  const result = migrateModeFunctions(source) as { source: string; changed: boolean };
+
+  expect(result.changed).toBe(true);
+  expect(result.source).toContain("shared function label");
+  expect(result.source).toContain('" {tag}"');
+});
+
+test("both ssr and client declaring the same helper name is skipped with a reason", () => {
+  const clash = `page P {
+  ssr { functions { function helper() { return 1 } } }
+  client { functions { function helper() { return 2 } } }
+  view { <main>x</main> }
+}
+`;
+  const result = migrateModeFunctions(clash) as { skip: string };
+
+  expect(result.skip).toContain("helper");
+});
+
+const roots: string[] = [];
+afterEach(() => {
+  for (const root of roots.splice(0)) rmSync(root, { recursive: true, force: true });
+});
+
+function project(): string {
+  const root = mkdtempSync(join(tmpdir(), "wrnexus-migrate-mode-functions-"));
+  roots.push(root);
+  mkdirSync(join(root, "app"), { recursive: true });
+  writeFileSync(
+    join(root, "package.json"),
+    JSON.stringify({
+      name: "mode-functions-migrate-app",
+      dependencies: { "@wrnexus/core": "^0.8.0" },
+      wrnexus: { version: "0.8.0" },
+    }),
+  );
+  return root;
+}
+
+test("one update run fully migrates a page mixing api entries and mode functions", () => {
+  const root = project();
+  writeFileSync(
+    join(root, "app", "P.wrn"),
+    `page P {
+  ssr {
+    api getUsers GET /api/users { response { return data } }
+    functions { function label(u) { return u.name } }
+  }
+  view { <main>x</main> }
+}
+`,
+  );
+
+  const report = {
+    changedAutomatically: [] as string[],
+    needsReview: [] as string[],
+    unresolvedImports: [] as string[],
+    ambiguousFunctions: [] as string[],
+    legacyOutputPayloads: [] as string[],
+    parseFailures: [] as string[],
+  };
+
+  updateApp(root, "0.9.0", false, { report });
+
+  const migrated = readFileSync(join(root, "app", "P.wrn"), "utf8");
+
+  expect(migrated).toContain("apis {");
+  expect(migrated).toContain("shared function label");
+  expect(migrated).not.toContain("ssr {");
+  expect(report.needsReview).toEqual([]);
+});