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+.worktrees/
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diff --git a/docs/superpowers/plans/2026-05-19-w4-runtime-validation-foundation.md b/docs/superpowers/plans/2026-05-19-w4-runtime-validation-foundation.md
new file mode 100644
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+++ b/docs/superpowers/plans/2026-05-19-w4-runtime-validation-foundation.md
@@ -0,0 +1,849 @@
+# W4 Runtime Validation Foundation Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
+
+**Goal:** Add a reusable runtime validation foundation for `apps/daemon` and apply it to `POST /api/chat` plus all `POST /api/proxy/*/stream` routes with shared `VALIDATION_FAILED` responses.
+
+**Architecture:** Keep runtime request schemas in `packages/contracts` so compile-time and runtime API shape stay aligned. Add one thin daemon-side parser helper that maps schema failures to the shared error envelope, then wire `server.ts` routes to validate before they enter chat/proxy execution or local capability checks.
+
+**Tech Stack:** TypeScript, Zod, Express, Vitest, pnpm workspaces
+
+---
+
+## File Structure
+
+- Modify: `packages/contracts/src/api/comments.ts`
+  - Add reusable Zod schemas for preview-comment position, selection kind, and pod members.
+- Modify: `packages/contracts/src/api/chat.ts`
+  - Add `ChatCommentAttachmentSchema` and `ChatRequestSchema`.
+- Modify: `packages/contracts/src/api/proxy.ts`
+  - Add `ProxyMessageRoleSchema`, `ProxyMessageSchema`, `ProxyStreamRequestSchema`, and `GoogleProxyStreamRequestSchema`.
+- Modify: `packages/contracts/src/index.ts`
+  - Re-export the new runtime schemas.
+- Create: `packages/contracts/tests/api-validation.test.ts`
+  - Lock request-schema behavior for chat and proxy contracts.
+- Create: `apps/daemon/src/validation.ts`
+  - Provide one focused helper that turns `schema.safeParse()` results into `{ ok, data }` or shared validation details.
+- Create: `apps/daemon/tests/validation.test.ts`
+  - Lock issue-path mapping and validation detail shape.
+- Modify: `apps/daemon/src/server.ts`
+  - Import contracts schemas and daemon validation helper, then validate `chat` and proxy route bodies before execution.
+- Modify: `apps/daemon/tests/chat-route.test.ts`
+  - Add route-level proof for malformed chat payloads returning `VALIDATION_FAILED`.
+- Modify: `apps/daemon/tests/proxy-routes.test.ts`
+  - Add route-level proof for malformed proxy payloads returning `VALIDATION_FAILED` while preserving existing happy-path proxy behavior.
+
+## Task 1: Add chat-side runtime schemas to contracts
+
+**Files:**
+- Create: `packages/contracts/tests/api-validation.test.ts`
+- Modify: `packages/contracts/src/api/comments.ts`
+- Modify: `packages/contracts/src/api/chat.ts`
+- Modify: `packages/contracts/src/index.ts`
+
+- [ ] **Step 1: Write the failing contracts test for chat request parsing**
+
+```ts
+import { describe, expect, it } from 'vitest';
+
+import {
+  ChatRequestSchema,
+  PreviewCommentMemberSchema,
+  PreviewCommentPositionSchema,
+} from '../src/index';
+
+describe('ChatRequestSchema', () => {
+  it('accepts a valid chat payload with nested comment attachments', () => {
+    const parsed = ChatRequestSchema.safeParse({
+      agentId: 'claude',
+      message: 'tighten the hero copy',
+      projectId: 'project-1',
+      commentAttachments: [
+        {
+          id: 'comment-1',
+          order: 1,
+          filePath: 'src/index.html',
+          elementId: 'hero-title',
+          selector: '#hero-title',
+          label: 'Hero title',
+          comment: 'Make this headline punchier.',
+          currentText: 'Build faster',
+          pagePosition: { x: 12, y: 24, width: 320, height: 72 },
+          htmlHint: '<h1 id="hero-title">Build faster</h1>',
+          selectionKind: 'pod',
+          memberCount: 1,
+          podMembers: [
+            {
+              elementId: 'hero-title',
+              selector: '#hero-title',
+              label: 'Hero title',
+              text: 'Build faster',
+              position: { x: 12, y: 24, width: 320, height: 72 },
+              htmlHint: '<h1 id="hero-title">Build faster</h1>',
+            },
+          ],
+          source: 'saved-comment',
+        },
+      ],
+    });
+
+    expect(parsed.success).toBe(true);
+  });
+
+  it('rejects malformed nested comment attachments with stable field paths', () => {
+    const parsed = ChatRequestSchema.safeParse({
+      agentId: 'claude',
+      message: 'hello',
+      commentAttachments: [
+        {
+          id: 'comment-1',
+          order: 'first',
+          filePath: 'src/index.html',
+        },
+      ],
+    });
+
+    expect(parsed.success).toBe(false);
+    expect(parsed.error.issues.map((issue) => issue.path.join('.'))).toContain(
+      'commentAttachments.0.order',
+    );
+  });
+});
+
+describe('preview comment schemas', () => {
+  it('accepts valid preview comment position and member payloads', () => {
+    expect(
+      PreviewCommentPositionSchema.safeParse({
+        x: 1,
+        y: 2,
+        width: 320,
+        height: 180,
+      }).success,
+    ).toBe(true);
+
+    expect(
+      PreviewCommentMemberSchema.safeParse({
+        elementId: 'cta',
+        selector: '#cta',
+        label: 'CTA',
+        text: 'Start now',
+        position: { x: 1, y: 2, width: 3, height: 4 },
+        htmlHint: '<button id="cta">Start now</button>',
+      }).success,
+    ).toBe(true);
+  });
+});
+```
+
+- [ ] **Step 2: Run the contracts test to verify it fails**
+
+Run:
+
+```bash
+pnpm --filter @open-design/contracts test -- tests/api-validation.test.ts
+```
+
+Expected: FAIL because `ChatRequestSchema`, `PreviewCommentPositionSchema`, and `PreviewCommentMemberSchema` do not exist yet.
+
+- [ ] **Step 3: Add reusable comment and chat request schemas**
+
+Update `packages/contracts/src/api/comments.ts`:
+
+```ts
+import { z } from 'zod';
+import type { OkResponse } from '../common';
+
+export const PreviewCommentPositionSchema = z.object({
+  x: z.number().finite(),
+  y: z.number().finite(),
+  width: z.number().finite(),
+  height: z.number().finite(),
+});
+export type PreviewCommentPosition = z.infer<typeof PreviewCommentPositionSchema>;
+
+export const PreviewCommentSelectionKindSchema = z.enum(['element', 'pod']);
+export type PreviewCommentSelectionKind = z.infer<
+  typeof PreviewCommentSelectionKindSchema
+>;
+
+export const PreviewCommentMemberSchema = z.object({
+  elementId: z.string().trim().min(1),
+  selector: z.string().trim().min(1),
+  label: z.string(),
+  text: z.string(),
+  position: PreviewCommentPositionSchema,
+  htmlHint: z.string(),
+});
+export type PreviewCommentMember = z.infer<typeof PreviewCommentMemberSchema>;
+```
+
+Update `packages/contracts/src/api/chat.ts`:
+
+```ts
+import { z } from 'zod';
+import type { ProjectFile } from './files';
+import type {
+  PreviewCommentMember,
+  PreviewCommentPosition,
+  PreviewCommentSelectionKind,
+} from './comments';
+import {
+  PreviewCommentMemberSchema,
+  PreviewCommentPositionSchema,
+  PreviewCommentSelectionKindSchema,
+} from './comments';
+
+const NullableIdSchema = z.string().trim().min(1).nullable().optional();
+
+export const ChatCommentAttachmentSchema = z.object({
+  id: z.string().trim().min(1),
+  order: z.number().int().min(1),
+  filePath: z.string().trim().min(1),
+  elementId: z.string().trim().min(1),
+  selector: z.string().trim().min(1),
+  label: z.string(),
+  comment: z.string().trim().min(1),
+  currentText: z.string(),
+  pagePosition: PreviewCommentPositionSchema,
+  htmlHint: z.string(),
+  selectionKind: PreviewCommentSelectionKindSchema.optional(),
+  memberCount: z.number().int().min(0).optional(),
+  podMembers: z.array(PreviewCommentMemberSchema).optional(),
+  source: z.enum(['saved-comment', 'board-batch']).optional(),
+});
+export type ChatCommentAttachment = z.infer<typeof ChatCommentAttachmentSchema>;
+
+export const ChatRequestSchema = z.object({
+  agentId: z.string().trim().min(1),
+  message: z.string().trim().min(1),
+  systemPrompt: z.string().optional(),
+  projectId: NullableIdSchema,
+  conversationId: NullableIdSchema,
+  assistantMessageId: NullableIdSchema,
+  clientRequestId: NullableIdSchema,
+  skillId: NullableIdSchema,
+  designSystemId: NullableIdSchema,
+  attachments: z.array(z.string().trim().min(1)).optional(),
+  commentAttachments: z.array(ChatCommentAttachmentSchema).optional(),
+  model: NullableIdSchema,
+  reasoning: z.string().nullable().optional(),
+});
+```
+
+Update `packages/contracts/src/index.ts`:
+
+```ts
+export * from './api/chat';
+export * from './api/comments';
+```
+
+- [ ] **Step 4: Run contracts tests and typecheck**
+
+Run:
+
+```bash
+pnpm --filter @open-design/contracts test -- tests/api-validation.test.ts
+pnpm --filter @open-design/contracts typecheck
+```
+
+Expected:
+
+- the new chat contracts tests PASS
+- contracts package typecheck PASS
+
+- [ ] **Step 5: Commit the chat contracts slice**
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design add -- packages/contracts/src/api/comments.ts packages/contracts/src/api/chat.ts packages/contracts/src/index.ts packages/contracts/tests/api-validation.test.ts
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design commit -m "feat(contracts): add chat request schemas"
+```
+
+## Task 2: Add proxy runtime schemas to contracts
+
+**Files:**
+- Modify: `packages/contracts/tests/api-validation.test.ts`
+- Modify: `packages/contracts/src/api/proxy.ts`
+- Modify: `packages/contracts/src/index.ts`
+
+- [ ] **Step 1: Extend the contracts test with proxy schema coverage**
+
+Add to `packages/contracts/tests/api-validation.test.ts`:
+
+```ts
+import {
+  GoogleProxyStreamRequestSchema,
+  ProxyStreamRequestSchema,
+} from '../src/index';
+
+describe('ProxyStreamRequestSchema', () => {
+  it('accepts a valid OpenAI-compatible proxy payload', () => {
+    const parsed = ProxyStreamRequestSchema.safeParse({
+      baseUrl: 'https://api.example.com/v1',
+      apiKey: 'sk-test',
+      model: 'gpt-5-mini',
+      messages: [{ role: 'user', content: 'hello' }],
+      maxTokens: 1024,
+    });
+
+    expect(parsed.success).toBe(true);
+  });
+
+  it('rejects malformed proxy messages with stable field paths', () => {
+    const parsed = ProxyStreamRequestSchema.safeParse({
+      baseUrl: 'https://api.example.com/v1',
+      apiKey: 'sk-test',
+      model: 'gpt-5-mini',
+      messages: [{ role: 'narrator', content: '' }],
+    });
+
+    expect(parsed.success).toBe(false);
+    expect(parsed.error.issues.map((issue) => issue.path.join('.'))).toEqual(
+      expect.arrayContaining(['messages.0.role', 'messages.0.content']),
+    );
+  });
+
+  it('allows Google proxy requests to omit baseUrl', () => {
+    const parsed = GoogleProxyStreamRequestSchema.safeParse({
+      apiKey: 'google-key',
+      model: 'gemini-2.0-flash',
+      messages: [{ role: 'user', content: 'hello' }],
+    });
+
+    expect(parsed.success).toBe(true);
+  });
+});
+```
+
+- [ ] **Step 2: Run the contracts test to verify proxy schema coverage fails**
+
+Run:
+
+```bash
+pnpm --filter @open-design/contracts test -- tests/api-validation.test.ts
+```
+
+Expected: FAIL because the proxy schemas are not exported yet.
+
+- [ ] **Step 3: Implement proxy request schemas**
+
+Update `packages/contracts/src/api/proxy.ts`:
+
+```ts
+import { z } from 'zod';
+
+export const ProxyMessageRoleSchema = z.enum([
+  'system',
+  'user',
+  'assistant',
+  'tool',
+]);
+export type ProxyMessageRole = z.infer<typeof ProxyMessageRoleSchema>;
+
+export const ProxyMessageSchema = z.object({
+  role: ProxyMessageRoleSchema,
+  content: z.string().trim().min(1),
+});
+export type ProxyMessage = z.infer<typeof ProxyMessageSchema>;
+
+const ProxyRequestBaseFields = {
+  apiKey: z.string().trim().min(1),
+  model: z.string().trim().min(1),
+  systemPrompt: z.string().optional(),
+  messages: z.array(ProxyMessageSchema).min(1),
+  maxTokens: z.number().int().positive().optional(),
+  apiVersion: z.string().trim().min(1).optional(),
+};
+
+export const ProxyStreamRequestSchema = z.object({
+  baseUrl: z.string().trim().url(),
+  ...ProxyRequestBaseFields,
+});
+export type ProxyStreamRequest = z.infer<typeof ProxyStreamRequestSchema>;
+
+export const GoogleProxyStreamRequestSchema = z.object({
+  baseUrl: z.string().trim().url().optional(),
+  ...ProxyRequestBaseFields,
+});
+```
+
+Update `packages/contracts/src/index.ts`:
+
+```ts
+export * from './api/proxy';
+```
+
+- [ ] **Step 4: Re-run contracts tests and typecheck**
+
+Run:
+
+```bash
+pnpm --filter @open-design/contracts test -- tests/api-validation.test.ts
+pnpm --filter @open-design/contracts typecheck
+```
+
+Expected:
+
+- proxy schema tests PASS
+- the combined contracts schema test file PASS
+- contracts typecheck PASS
+
+- [ ] **Step 5: Commit the proxy contracts slice**
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design add -- packages/contracts/src/api/proxy.ts packages/contracts/src/index.ts packages/contracts/tests/api-validation.test.ts
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design commit -m "feat(contracts): add proxy request schemas"
+```
+
+## Task 3: Add a daemon-side validation helper
+
+**Files:**
+- Create: `apps/daemon/src/validation.ts`
+- Create: `apps/daemon/tests/validation.test.ts`
+
+- [ ] **Step 1: Write the failing daemon validation helper test**
+
+Create `apps/daemon/tests/validation.test.ts`:
+
+```ts
+import { describe, expect, it } from 'vitest';
+import { z } from 'zod';
+
+import { parseRequest, zodPathToString } from '../src/validation.js';
+
+describe('zodPathToString', () => {
+  it('renders nested paths using dot + bracket notation', () => {
+    expect(zodPathToString(['commentAttachments', 0, 'order'])).toBe(
+      'commentAttachments[0].order',
+    );
+  });
+});
+
+describe('parseRequest', () => {
+  const schema = z.object({
+    message: z.string().trim().min(1),
+    nested: z.object({
+      count: z.number().int(),
+    }),
+  });
+
+  it('returns parsed data when validation succeeds', () => {
+    expect(
+      parseRequest(schema, {
+        message: 'hello',
+        nested: { count: 3 },
+      }),
+    ).toEqual({
+      ok: true,
+      data: { message: 'hello', nested: { count: 3 } },
+    });
+  });
+
+  it('returns shared validation details when validation fails', () => {
+    const result = parseRequest(schema, {
+      message: '',
+      nested: { count: 'nope' },
+    });
+
+    expect(result.ok).toBe(false);
+    if (result.ok) throw new Error('expected validation failure');
+
+    expect(result.details).toEqual({
+      kind: 'validation',
+      issues: expect.arrayContaining([
+        expect.objectContaining({ path: 'message' }),
+        expect.objectContaining({ path: 'nested.count' }),
+      ]),
+    });
+  });
+});
+```
+
+- [ ] **Step 2: Run the daemon helper test to verify it fails**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/validation.test.ts
+```
+
+Expected: FAIL because `apps/daemon/src/validation.ts` does not exist yet.
+
+- [ ] **Step 3: Implement the validation helper**
+
+Create `apps/daemon/src/validation.ts`:
+
+```ts
+import type { ApiValidationErrorDetails, ApiValidationIssue } from '@open-design/contracts';
+import { z, type ZodTypeAny } from 'zod';
+
+export function zodPathToString(path: (string | number)[]): string {
+  return path.reduce((acc, part) => {
+    if (typeof part === 'number') return `${acc}[${part}]`;
+    return acc ? `${acc}.${part}` : part;
+  }, '');
+}
+
+export function zodIssuesToValidationDetails(
+  error: z.ZodError,
+): ApiValidationErrorDetails {
+  const issues: ApiValidationIssue[] = error.issues.map((issue) => ({
+    path: zodPathToString(issue.path),
+    message: issue.message,
+    code: issue.code,
+  }));
+
+  return {
+    kind: 'validation',
+    issues,
+  };
+}
+
+export function parseRequest<S extends ZodTypeAny>(
+  schema: S,
+  input: unknown,
+): { ok: true; data: z.infer<S> } | { ok: false; details: ApiValidationErrorDetails } {
+  const parsed = schema.safeParse(input);
+  if (parsed.success) {
+    return { ok: true, data: parsed.data };
+  }
+
+  return {
+    ok: false,
+    details: zodIssuesToValidationDetails(parsed.error),
+  };
+}
+```
+
+- [ ] **Step 4: Re-run the daemon helper test**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/validation.test.ts
+pnpm --filter @open-design/daemon typecheck
+```
+
+Expected:
+
+- validation helper tests PASS
+- daemon typecheck PASS
+
+- [ ] **Step 5: Commit the validation helper slice**
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design add -- apps/daemon/src/validation.ts apps/daemon/tests/validation.test.ts
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design commit -m "feat(daemon): add request validation helper"
+```
+
+## Task 4: Validate `/api/chat` before creating a run
+
+**Files:**
+- Modify: `apps/daemon/src/server.ts`
+- Modify: `apps/daemon/tests/chat-route.test.ts`
+
+- [ ] **Step 1: Add failing route tests for malformed chat payloads**
+
+Add to `apps/daemon/tests/chat-route.test.ts`:
+
+```ts
+  it('returns VALIDATION_FAILED for malformed chat payloads before creating a run', async () => {
+    const response = await fetch(`${baseUrl}/api/chat`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        agentId: 'claude',
+        commentAttachments: [
+          {
+            id: 'comment-1',
+            order: 'first',
+            filePath: 'src/index.html',
+          },
+        ],
+      }),
+    });
+
+    expect(response.status).toBe(400);
+    await expect(response.json()).resolves.toMatchObject({
+      error: {
+        code: 'VALIDATION_FAILED',
+        details: {
+          kind: 'validation',
+          issues: expect.arrayContaining([
+            expect.objectContaining({ path: 'message' }),
+            expect.objectContaining({ path: 'commentAttachments[0].order' }),
+          ]),
+        },
+      },
+    });
+  });
+```
+
+- [ ] **Step 2: Run the chat route test to verify it fails**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/chat-route.test.ts
+```
+
+Expected: FAIL because the route currently creates a run immediately and does not return a shared validation envelope.
+
+- [ ] **Step 3: Wire chat route validation into `server.ts`**
+
+Update imports near the top of `apps/daemon/src/server.ts`:
+
+```ts
+import { ChatRequestSchema } from '@open-design/contracts';
+import { parseRequest } from './validation.js';
+```
+
+Update the route:
+
+```ts
+  app.post('/api/chat', (req, res) => {
+    const parsedBody = parseRequest(ChatRequestSchema, req.body);
+    if (!parsedBody.ok) {
+      return sendApiError(
+        res,
+        400,
+        'VALIDATION_FAILED',
+        'Invalid request payload',
+        { details: parsedBody.details },
+      );
+    }
+
+    const run = design.runs.create();
+    design.runs.stream(run, req, res);
+    design.runs.start(run, () => startChatRun(parsedBody.data, run));
+  });
+```
+
+- [ ] **Step 4: Re-run chat route tests**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/chat-route.test.ts
+pnpm --filter @open-design/daemon typecheck
+```
+
+Expected:
+
+- chat route tests PASS
+- daemon typecheck PASS
+
+- [ ] **Step 5: Commit the chat route slice**
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design add -- apps/daemon/src/server.ts apps/daemon/tests/chat-route.test.ts
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design commit -m "feat(daemon): validate chat request bodies"
+```
+
+## Task 5: Validate all proxy stream routes before provider-specific security checks
+
+**Files:**
+- Modify: `apps/daemon/src/server.ts`
+- Modify: `apps/daemon/tests/proxy-routes.test.ts`
+
+- [ ] **Step 1: Add failing proxy route validation tests**
+
+Add to `apps/daemon/tests/proxy-routes.test.ts`:
+
+```ts
+  it('returns VALIDATION_FAILED for malformed OpenAI-compatible proxy payloads', async () => {
+    const res = await realFetch(`${baseUrl}/api/proxy/openai/stream`, {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({
+        baseUrl: 'https://api.example.com/v1',
+        apiKey: 'sk-test',
+        messages: [{ role: 'narrator', content: '' }],
+      }),
+    });
+
+    expect(res.status).toBe(400);
+    await expect(res.json()).resolves.toMatchObject({
+      error: {
+        code: 'VALIDATION_FAILED',
+        details: {
+          kind: 'validation',
+          issues: expect.arrayContaining([
+            expect.objectContaining({ path: 'model' }),
+            expect.objectContaining({ path: 'messages[0].role' }),
+            expect.objectContaining({ path: 'messages[0].content' }),
+          ]),
+        },
+      },
+    });
+  });
+
+  it('returns VALIDATION_FAILED when Google proxy payload omits apiKey', async () => {
+    const res = await realFetch(`${baseUrl}/api/proxy/google/stream`, {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({
+        model: 'gemini-2.0-flash',
+        messages: [{ role: 'user', content: 'hello' }],
+      }),
+    });
+
+    expect(res.status).toBe(400);
+    await expect(res.json()).resolves.toMatchObject({
+      error: {
+        code: 'VALIDATION_FAILED',
+        details: {
+          kind: 'validation',
+          issues: expect.arrayContaining([
+            expect.objectContaining({ path: 'apiKey' }),
+          ]),
+        },
+      },
+    });
+  });
+```
+
+- [ ] **Step 2: Run proxy route tests to verify they fail**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/proxy-routes.test.ts
+```
+
+Expected: FAIL because the proxy routes still return route-local `BAD_REQUEST` checks instead of shared validation errors.
+
+- [ ] **Step 3: Wire proxy schemas into all proxy routes**
+
+Update imports near the top of `apps/daemon/src/server.ts`:
+
+```ts
+import {
+  GoogleProxyStreamRequestSchema,
+  ProxyStreamRequestSchema,
+} from '@open-design/contracts';
+import { parseRequest } from './validation.js';
+```
+
+Update Anthropic/OpenAI/Azure routes:
+
+```ts
+    const parsedBody = parseRequest(ProxyStreamRequestSchema, req.body);
+    if (!parsedBody.ok) {
+      return sendApiError(
+        res,
+        400,
+        'VALIDATION_FAILED',
+        'Invalid request payload',
+        { details: parsedBody.details },
+      );
+    }
+
+    const { baseUrl, apiKey, model, systemPrompt, messages, maxTokens } =
+      parsedBody.data;
+```
+
+Update Google route:
+
+```ts
+    const parsedBody = parseRequest(GoogleProxyStreamRequestSchema, req.body);
+    if (!parsedBody.ok) {
+      return sendApiError(
+        res,
+        400,
+        'VALIDATION_FAILED',
+        'Invalid request payload',
+        { details: parsedBody.details },
+      );
+    }
+
+    const {
+      baseUrl,
+      apiKey,
+      model,
+      systemPrompt,
+      messages,
+      maxTokens,
+    } = parsedBody.data;
+    const effectiveBaseUrl =
+      baseUrl || 'https://generativelanguage.googleapis.com';
+```
+
+Do not remove `validateExternalApiBaseUrl()`. Keep it after schema parsing so malformed shapes return `VALIDATION_FAILED` and valid-but-forbidden targets still return `FORBIDDEN`.
+
+- [ ] **Step 4: Re-run proxy route tests and daemon typecheck**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/proxy-routes.test.ts
+pnpm --filter @open-design/daemon typecheck
+```
+
+Expected:
+
+- proxy route tests PASS
+- existing proxy happy-path tests still PASS
+- daemon typecheck PASS
+
+- [ ] **Step 5: Commit the proxy route slice**
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design add -- apps/daemon/src/server.ts apps/daemon/tests/proxy-routes.test.ts
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design commit -m "feat(daemon): validate proxy request bodies"
+```
+
+## Task 6: Run full verification for the W4 first slice
+
+**Files:**
+- Modify: none
+
+- [ ] **Step 1: Run the focused contracts tests**
+
+Run:
+
+```bash
+pnpm --filter @open-design/contracts test -- tests/api-validation.test.ts
+```
+
+Expected: PASS
+
+- [ ] **Step 2: Run the focused daemon tests**
+
+Run:
+
+```bash
+pnpm --filter @open-design/daemon test -- tests/validation.test.ts tests/chat-route.test.ts tests/proxy-routes.test.ts
+```
+
+Expected: PASS
+
+- [ ] **Step 3: Run workspace-required checks**
+
+Run:
+
+```bash
+pnpm guard
+pnpm typecheck
+```
+
+Expected: PASS
+
+- [ ] **Step 4: Inspect working tree before handoff**
+
+Run:
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design --no-pager status --short
+```
+
+Expected: only the planned W4 validation files remain changed.
+
+- [ ] **Step 5: Inspect the final commit stack**
+
+Run:
+
+```bash
+git -C G:\AUDHOUSE\HOUSEDRAW\open-design --no-pager log --oneline -5
+```
+
+Expected: the recent history shows the contracts, helper, chat-route, and proxy-route commits created in Tasks 1-5.
diff --git a/docs/superpowers/specs/2026-05-19-w4-runtime-validation-design.md b/docs/superpowers/specs/2026-05-19-w4-runtime-validation-design.md
new file mode 100644
index 000000000..f1f5efe13
--- /dev/null
+++ b/docs/superpowers/specs/2026-05-19-w4-runtime-validation-design.md
@@ -0,0 +1,288 @@
+# W4 Runtime Validation Foundation Design
+
+## Status
+
+- Date: 2026-05-19
+- Scope: `apps/daemon` first validation slice
+- Target: `/api/chat` and `/api/proxy/*/stream`
+- Decision: approved
+
+## Purpose
+
+This design defines the first W4 slice from `specs/current/maintainability-roadmap.md`.
+
+The goal is to add a reusable runtime validation foundation at the daemon boundary without prematurely doing W5 modularization. The first slice focuses on the highest-risk HTTP entry points:
+
+- `POST /api/chat`
+- `POST /api/proxy/anthropic/stream`
+- `POST /api/proxy/openai/stream`
+- `POST /api/proxy/azure/stream`
+- `POST /api/proxy/google/stream`
+
+## OPM Frame
+
+### Objects
+
+- **Contract Schemas**
+  - Runtime schemas defined in `packages/contracts`
+  - Own request-shape truth for `chat` and `proxy`
+- **Daemon Validation Layer**
+  - Thin helper layer in `apps/daemon`
+  - Parses raw route input and converts schema failures into shared API errors
+- **Route Handlers**
+  - Existing `server.ts` route bodies
+  - Remain responsible for orchestration and provider-specific behavior
+- **Security Checks**
+  - Local capability rules such as loopback/origin checks and private-network blocking
+  - Stay in the daemon, not in contracts
+- **Shared Validation Error Envelope**
+  - `ApiError` with `code: VALIDATION_FAILED`
+  - `details.kind = validation`
+  - `details.issues = [...]`
+
+### Processes
+
+1. A route receives raw `req.body`, `req.params`, or `req.query`.
+2. The daemon validation layer parses that input with a contracts schema.
+3. If parsing fails, the route returns a shared validation envelope.
+4. If parsing succeeds, the route runs daemon-only security checks.
+5. If a security check fails, the route returns explicit `FORBIDDEN` or `BAD_REQUEST`.
+6. Only validated and permitted input reaches the existing chat or proxy execution flow.
+
+### OPL Statements
+
+- Contract Schemas validate request shape.
+- Daemon Validation Layer translates schema failure into `VALIDATION_FAILED`.
+- Route Handlers execute business flow only after validation succeeds.
+- Security Checks constrain local execution even when request shape is valid.
+- This slice changes request validation behavior but does not change SSE success semantics.
+
+## Architectural Decision
+
+### Recommended approach
+
+Use a **contracts-first validator layer**.
+
+Runtime schemas are added beside existing API types in `packages/contracts`, and daemon routes consume those schemas through a small local helper. This keeps compile-time types and runtime validation aligned and creates a reusable base for later W5 modularization and W8 test expansion.
+
+### Rejected alternatives
+
+#### Daemon-local schemas only
+
+This would be faster to start but would keep contracts and runtime validation split across packages.
+
+#### Thin handwritten guards only
+
+This would reduce immediate risk but would not create a real validation foundation and would likely be replaced in the next slice.
+
+## File Design
+
+### `packages/contracts/src/api/chat.ts`
+
+Add runtime schemas for:
+
+- `ChatRequest`
+- `ChatCommentAttachment`
+- nested comment attachment position/member structures if required
+
+Keep the existing interfaces. The runtime schemas become the source for daemon parsing, not a replacement for the exported types.
+
+### `packages/contracts/src/api/proxy.ts`
+
+Add runtime schemas for:
+
+- `ProxyMessage`
+- `ProxyStreamRequest`
+
+The schema must cover:
+
+- `baseUrl`
+- `apiKey`
+- `model`
+- `systemPrompt`
+- `messages`
+- `maxTokens`
+- `apiVersion`
+
+### `packages/contracts/src/errors.ts`
+
+Reuse:
+
+- `ApiValidationIssue`
+- `ApiValidationErrorDetails`
+- `ApiError`
+
+If needed, add one small helper that maps runtime-schema issues into the shared `issues[]` shape.
+
+### `apps/daemon/src/server.ts`
+
+Keep routes in place for this slice.
+
+Replace scattered route-local input guards in `chat` and proxy routes with calls into a thin validation helper. Avoid opportunistic modularization here; W5 owns route extraction.
+
+### `apps/daemon/src/validation.ts` or equivalent focused helper
+
+Introduce one small helper module whose only responsibilities are:
+
+- parse raw input with a provided schema
+- map issues into the shared error detail format
+- send `VALIDATION_FAILED` in a consistent response shape
+
+This helper must not absorb route business logic, provider behavior, SSE behavior, or daemon-only authorization rules.
+
+### `apps/daemon/tests/chat-route.test.ts`
+
+Extend route tests to cover:
+
+- missing required fields
+- empty-string required fields
+- invalid field types
+- invalid nested comment attachment data
+- assertion of shared validation envelope
+
+### `apps/daemon/tests/proxy-routes.test.ts`
+
+Extend route tests to cover:
+
+- missing required fields
+- invalid `baseUrl`
+- invalid or empty `messages`
+- invalid message role/content shapes
+- assertion of shared validation envelope
+
+## Scope
+
+### In scope
+
+- reusable validation helper for daemon HTTP boundary parsing
+- contracts runtime schemas for `chat` and `proxy`
+- shared validation error envelope for the targeted routes
+- route tests proving failure shape and success preservation
+
+### Out of scope
+
+- upload, files, deploy, media, config, and other daemon routes
+- `server.ts` route extraction or service decomposition
+- SSE event-contract redesign
+- provider-specific semantic validation beyond basic field shape and range
+- broader cross-platform hardening beyond existing checks
+
+## Validation Rules
+
+### Chat route
+
+`POST /api/chat` must require:
+
+- `agentId`: non-empty string
+- `message`: non-empty string
+
+Optional fields may be absent or explicitly `null` where the current contract allows nullability, but when provided they must conform to their expected string or array shape.
+
+`commentAttachments`, when present, must validate nested fields rather than relying on silent normalization.
+
+### Proxy routes
+
+All proxy routes must validate common request structure first.
+
+Common requirements:
+
+- `apiKey`: non-empty string, except only existing route behavior may decide defaults elsewhere
+- `apiKey`: non-empty string
+- `model`: non-empty string
+- `messages`: array of valid `{ role, content }` items
+
+Provider notes:
+
+- Anthropic/OpenAI/Azure require `baseUrl`
+- Google may omit `baseUrl`, in which case the existing public default URL is applied before daemon security checks
+- `maxTokens` receives only basic numeric validation in this slice
+- `apiVersion` receives basic string validation in this slice
+
+### Security boundary rule
+
+Base URL network policy remains a daemon concern.
+
+Schema validation answers **"is the shape valid?"**
+
+Daemon security answers **"may this valid request access this target?"**
+
+## Error Model
+
+### Validation failure
+
+Validation failures return:
+
+- HTTP status: `400`
+- `error.code = VALIDATION_FAILED`
+- `error.message = Invalid request payload` or a similarly stable shared message
+- `error.details.kind = validation`
+- `error.details.issues = [...]`
+
+Each issue must include a stable `path` and human-readable `message`. A schema issue may also include a normalized `code`.
+
+### Security failure
+
+Security failures continue to use explicit route-level codes, for example:
+
+- `FORBIDDEN` for private-network or local-origin rejection
+- `BAD_REQUEST` for provider-specific request problems that are not generic schema failures
+
+### Upstream/provider failure
+
+Proxy SSE error behavior stays unchanged in this slice. Validation happens before the upstream call path starts.
+
+## Testing Strategy
+
+### Route-level proof
+
+Primary proof lives in daemon route tests because this slice protects HTTP boundaries.
+
+Required assertions:
+
+1. invalid input returns `400`
+2. error shape matches shared `ApiError`
+3. `error.code` is `VALIDATION_FAILED`
+4. `details.kind` is `validation`
+5. `details.issues` includes stable field paths
+
+### Behavior-preservation proof
+
+Existing happy-path tests for `chat` and `proxy` must remain green to prove the slice adds guardrails without changing successful streaming behavior.
+
+### Verification commands
+
+- `pnpm --filter @open-design/daemon test`
+- `pnpm --filter @open-design/daemon typecheck`
+- `pnpm guard`
+- `pnpm typecheck`
+
+## Success Criteria
+
+- `chat` and proxy stream routes stop relying on scattered ad hoc input checks
+- targeted routes return one shared validation envelope for malformed input
+- daemon-only security checks remain explicit and separate from schema parsing
+- the new schemas are reusable by later W4 slices and W5/W8 work
+
+## Risks and Guards
+
+### Risk: contracts schemas drift from existing route behavior
+
+Guard: add route tests for current accepted valid payloads before tightening optionality.
+
+### Risk: route behavior changes accidentally while adding validation
+
+Guard: preserve existing success-path tests and limit changes to boundary parsing plus error mapping.
+
+### Risk: helper grows into premature route framework
+
+Guard: keep helper responsibilities narrow and leave route decomposition to W5.
+
+## Implementation Handoff
+
+The next planning phase should create a bounded implementation plan that:
+
+1. adds contracts schemas
+2. adds one daemon validation helper
+3. migrates `chat` and proxy routes to that helper
+4. expands daemon tests
+5. verifies no regression in current successful flows