feat: de-risk agent loop — semantic tool schema + agent loop + real-WP spike harness

- api/agents: tool-schemas (semantic allowlist), agent-loop (multi-step + budget), circuit-breaker, llm-client/tool-executor interfaces
- api/agents: WpRestExecutor (real WP REST), OpenRouterLlmClient
- e2e/agent: multi-step prompts + run-agent-spike runner (scores rendered changes)
- ADR 0017; 101 unit tests green

api/src/agents/agent-loop.ts

@@ -0,0 +1,48 @@
+import type { LlmClient, LlmMessage } from './llm-client.ts';
+import type { ToolExecutor } from './tool-executor.ts';
+
+export type RunAgentOptions = {
+  systemPrompt: string;
+  userPrompt: string;
+  maxRounds: number;
+};
+
+export type RunAgentResult = {
+  rounds: number;
+  toolCalls: number;
+  finalContent: string | null;
+  halted: boolean;
+};
+
+export async function runAgent(
+  client: LlmClient,
+  executor: ToolExecutor,
+  opts: RunAgentOptions,
+): Promise<RunAgentResult> {
+  const messages: LlmMessage[] = [
+    { role: 'system', content: opts.systemPrompt },
+    { role: 'user', content: opts.userPrompt },
+  ];
+  let toolCalls = 0;
+
+  for (let round = 0; round < opts.maxRounds; round += 1) {
+    const response = await client.complete(messages);
+    const message = response.choices[0]?.message;
+    const calls = message?.tool_calls ?? [];
+
+    if (calls.length === 0) {
+      return { rounds: round + 1, toolCalls, finalContent: message?.content ?? null, halted: false };
+    }
+
+    messages.push({ role: 'assistant', content: message?.content ?? null, tool_calls: calls });
+
+    for (const call of calls) {
+      const args = JSON.parse(call.function.arguments) as Record<string, string>;
+      const result = await executor.execute(call.function.name, args);
+      toolCalls += 1;
+      messages.push({ role: 'tool', content: result.result, tool_call_id: call.id, name: call.function.name });
+    }
+  }
+
+  return { rounds: opts.maxRounds, toolCalls, finalContent: null, halted: true };
+}

api/src/agents/circuit-breaker.ts

@@ -0,0 +1,21 @@
+export type CircuitBreakerOptions = {
+  maxConsecutiveFailures: number;
+};
+
+export class CircuitBreaker {
+  private failures = 0;
+
+  constructor(private readonly opts: CircuitBreakerOptions) {}
+
+  recordFailure(): void {
+    this.failures += 1;
+  }
+
+  recordSuccess(): void {
+    this.failures = 0;
+  }
+
+  shouldHalt(): boolean {
+    return this.failures >= this.opts.maxConsecutiveFailures;
+  }
+}

api/src/agents/llm-client.ts

@@ -0,0 +1,23 @@
+export type LlmToolCall = {
+  id: string;
+  type: 'function';
+  function: { name: string; arguments: string };
+};
+
+export type LlmMessage = {
+  role: 'system' | 'user' | 'assistant' | 'tool';
+  content: string | null;
+  tool_calls?: LlmToolCall[];
+  tool_call_id?: string;
+  name?: string;
+};
+
+export type LlmResponse = {
+  choices: Array<{
+    message: { role: 'assistant'; content: string | null; tool_calls?: LlmToolCall[] };
+  }>;
+};
+
+export interface LlmClient {
+  complete(messages: LlmMessage[]): Promise<LlmResponse>;
+}

api/src/agents/openrouter-client.ts

@@ -0,0 +1,32 @@
+import { generateToolSchemas } from './tool-schemas.ts';
+import type { LlmClient, LlmMessage, LlmResponse } from './llm-client.ts';
+
+export type OpenRouterOptions = {
+  apiKey: string;
+  model?: string;
+};
+
+export class OpenRouterLlmClient implements LlmClient {
+  constructor(private readonly opts: OpenRouterOptions) {}
+
+  async complete(messages: LlmMessage[]): Promise<LlmResponse> {
+    const res = await fetch('https://openrouter.ai/api/v1/chat/completions', {
+      method: 'POST',
+      headers: {
+        Authorization: `Bearer ${this.opts.apiKey}`,
+        'Content-Type': 'application/json',
+        'HTTP-Referer': 'https://wursor.dev',
+        'X-Title': 'Wursor',
+      },
+      body: JSON.stringify({
+        model: this.opts.model ?? 'x-ai/grok-4.6',
+        messages,
+        tools: generateToolSchemas(),
+      }),
+    });
+    if (!res.ok) {
+      throw new Error(`LLM HTTP ${res.status}`);
+    }
+    return (await res.json()) as LlmResponse;
+  }
+}

api/src/agents/tool-executor.ts

@@ -0,0 +1,7 @@
+export type ToolResult = {
+  result: string;
+};
+
+export interface ToolExecutor {
+  execute(name: string, args: Record<string, string>): Promise<ToolResult>;
+}

api/src/agents/tool-schemas.ts

@@ -0,0 +1,97 @@
+export type ToolSchema = {
+  type: 'function';
+  function: {
+    name: string;
+    description: string;
+    parameters: Record<string, unknown>;
+  };
+};
+
+export const ALLOWED_TOOL_NAMES = [
+  'read_page',
+  'update_post',
+  'update_option',
+  'create_page',
+  'update_theme_json',
+] as const;
+
+export type AllowedToolName = (typeof ALLOWED_TOOL_NAMES)[number];
+
+const TOOLS: ToolSchema[] = [
+  {
+    type: 'function',
+    function: {
+      name: 'read_page',
+      description: 'Read the raw content and title of a page by its slug.',
+      parameters: {
+        type: 'object',
+        properties: { page: { type: 'string', description: 'Page slug' } },
+        required: ['page'],
+      },
+    },
+  },
+  {
+    type: 'function',
+    function: {
+      name: 'update_post',
+      description: 'Update the title and/or content of an existing page or post.',
+      parameters: {
+        type: 'object',
+        properties: {
+          page: { type: 'string', description: 'Page slug' },
+          title: { type: 'string' },
+          content: { type: 'string' },
+        },
+        required: ['page'],
+      },
+    },
+  },
+  {
+    type: 'function',
+    function: {
+      name: 'update_option',
+      description: 'Update a WordPress option such as blogname or blogdescription.',
+      parameters: {
+        type: 'object',
+        properties: {
+          key: { type: 'string' },
+          value: { type: 'string' },
+        },
+        required: ['key', 'value'],
+      },
+    },
+  },
+  {
+    type: 'function',
+    function: {
+      name: 'create_page',
+      description: 'Create a new page with a title and content.',
+      parameters: {
+        type: 'object',
+        properties: {
+          title: { type: 'string' },
+          content: { type: 'string' },
+        },
+        required: ['title', 'content'],
+      },
+    },
+  },
+  {
+    type: 'function',
+    function: {
+      name: 'update_theme_json',
+      description: 'Apply a JSON patch to theme.json (colors, fonts, layout).',
+      parameters: {
+        type: 'object',
+        properties: {
+          patch: { type: 'string', description: 'JSON patch object as a string' },
+        },
+        required: ['patch'],
+      },
+    },
+  },
+];
+
+export function generateToolSchemas(): ToolSchema[] {
+  return TOOLS;
+}

api/src/agents/wp-executor.ts

@@ -0,0 +1,90 @@
+import type { ToolExecutor, ToolResult } from './tool-executor.ts';
+
+export type WpRestCredentials = {
+  baseUrl: string;
+  username: string;
+  appPassword: string;
+};
+
+function basicAuth(username: string, password: string): string {
+  return `Basic ${Buffer.from(`${username}:${password}`).toString('base64')}`;
+}
+
+export class WpRestExecutor implements ToolExecutor {
+  private readonly base: string;
+  private readonly auth: string;
+
+  constructor(private readonly creds: WpRestCredentials) {
+    this.base = creds.baseUrl.replace(/\/$/, '');
+    this.auth = basicAuth(creds.username, creds.appPassword);
+  }
+
+  async execute(name: string, args: Record<string, string>): Promise<ToolResult> {
+    switch (name) {
+      case 'read_page':
+        return this.readPage(args.page);
+      case 'update_post':
+        return this.updatePost(args);
+      case 'create_page':
+        return this.createPage(args);
+      case 'update_option':
+        return this.updateOption(args);
+      default:
+        throw new Error(`unsupported tool: ${name}`);
+    }
+  }
+
+  private async json(url: string, init?: RequestInit): Promise<unknown> {
+    const res = await fetch(url, { ...init, headers: { Authorization: this.auth, ...(init?.headers ?? {}) } });
+    if (!res.ok) {
+      throw new Error(`WP HTTP ${res.status} ${url}`);
+    }
+    return res.json();
+  }
+
+  private async readPage(page: string): Promise<ToolResult> {
+    const data = await this.json(`${this.base}/wp-json/wp/v2/pages?slug=${encodeURIComponent(page)}&_fields=id,title,content`);
+    return { result: JSON.stringify(data) };
+  }
+
+  private async pageIdBySlug(slug: string): Promise<number | undefined> {
+    const data = (await this.json(
+      `${this.base}/wp-json/wp/v2/pages?slug=${encodeURIComponent(slug)}&_fields=id`,
+    )) as Array<{ id: number }>;
+    return data[0]?.id;
+  }
+
+  private async updatePost(args: Record<string, string>): Promise<ToolResult> {
+    const id = await this.pageIdBySlug(args.page ?? '');
+    if (id === undefined) {
+      return { result: `no page with slug ${args.page}` };
+    }
+    const body: Record<string, string> = {};
+    if (args.title !== undefined) body.title = args.title;
+    if (args.content !== undefined) body.content = args.content;
+    const updated = await this.json(`${this.base}/wp-json/wp/v2/pages/${id}`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(body),
+    });
+    return { result: JSON.stringify(updated) };
+  }
+
+  private async createPage(args: Record<string, string>): Promise<ToolResult> {
+    const created = await this.json(`${this.base}/wp-json/wp/v2/pages`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ title: args.title, content: args.content, status: 'publish' }),
+    });
+    return { result: JSON.stringify(created) };
+  }
+
+  private async updateOption(args: Record<string, string>): Promise<ToolResult> {
+    const updated = await this.json(`${this.base}/wp-json/wp/v2/settings`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ [args.key ?? '']: args.value }),
+    });
+    return { result: JSON.stringify(updated) };
+  }
+}