feat(api): companion SSE turn endpoint + per-Space history

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/api/index.js

@@ -22,6 +22,7 @@ import { router as auditRouter } from './routes/audit.js';
 import { router as searchRouter } from './routes/search.js';
 import { router as jobsRouter } from './routes/jobs.js';
 import { router as captureRouter } from './routes/capture.js';
+import { spacesScopedRouter as companionRouter } from './routes/companion.js';
 
 export function mountApi(app) {
   const api = Router();
@@ -32,6 +33,7 @@ export function mountApi(app) {
   api.use('/spaces/:space_id/tasks', tasksBySpaceRouter);
   api.use('/spaces/:space_id/pages', pagesBySpaceRouter);
   api.use('/spaces/:space_id/resources', resourcesBySpaceRouter);
+  api.use('/spaces/:space_id/companion', companionRouter);
   api.use('/projects', projectsRouter);
   api.use('/projects/:project_id/tasks', tasksByProjectRouter);
   api.use('/tasks', tasksRouter);

lib/api/routes/companion.js

@@ -0,0 +1,95 @@
+import { Router } from 'express';
+import { z } from 'zod';
+import { validate } from '../validate.js';
+import { asyncWrap } from '../errors.js';
+import * as conversations from '../../db/repos/conversations.js';
+import * as messages from '../../db/repos/messages.js';
+import * as agents from '../../db/repos/agents.js';
+import { companionRegistry } from '../../ai/agent/tools/index.js';
+import { runTurn } from '../../ai/agent/runtime.js';
+import { makeCallModel, getAnthropicClient, DEFAULT_MODEL } from '../../ai/anthropic.js';
+
+const COMPANION_SLUG = 'companion';
+
+const SYSTEM = `You are the Void companion — a concise, helpful assistant embedded in a personal knowledge system.
+Ground answers in the Void's content: call the context tool to see what the owner is looking at, and search/read before answering factual questions.
+When the owner asks you to change something, use propose_change — it creates a draft they approve; you cannot apply changes directly. Be brief.`;
+
+async function resolveConversation(space_id) {
+  const agent = await agents.getBySlug(COMPANION_SLUG);
+  const convo = await conversations.findOrCreateForSpace(space_id, agent.id, { kind: 'user', id: null });
+  return { agent, convo };
+}
+
+function toAnthropicHistory(rows) {
+  return rows
+    .filter(m => m.role === 'user' || m.role === 'assistant')
+    .map(m => ({ role: m.role, content: m.body }));
+}
+
+export const spacesScopedRouter = Router({ mergeParams: true });
+
+spacesScopedRouter.get('/', asyncWrap(async (req, res) => {
+  const { agent, convo } = await resolveConversation(req.params.space_id);
+  const rows = await messages.listByConversation(convo.id);
+  res.json({
+    conversation_id: convo.id,
+    agent: { id: agent.id, slug: agent.slug, name: agent.name },
+    messages: rows
+  });
+}));
+
+const turnSchema = z.object({
+  text: z.string().min(1),
+  view: z.object({ entityType: z.string(), entityId: z.string() }).partial().optional()
+});
+
+spacesScopedRouter.post('/turn',
+  validate({ body: turnSchema }),
+  asyncWrap(async (req, res) => {
+    const { agent, convo } = await resolveConversation(req.params.space_id);
+    const { text, view } = req.body;
+
+    await messages.append(convo.id, { role: 'user', body: text });
+
+    res.writeHead(200, {
+      'Content-Type': 'text/event-stream',
+      'Cache-Control': 'no-cache',
+      Connection: 'keep-alive'
+    });
+    const send = (event, data) => res.write(`event: ${event}\ndata: ${JSON.stringify(data)}\n\n`);
+
+    const callModel = req.app.locals.callModel
+      || makeCallModel({ client: getAnthropicClient(), model: agent.model || DEFAULT_MODEL });
+
+    const history = toAnthropicHistory(await messages.listByConversation(convo.id));
+
+    let result;
+    try {
+      result = await runTurn({
+        callModel,
+        registry: companionRegistry,
+        system: SYSTEM,
+        messages: history,
+        ctx: {
+          agent: { kind: 'agent', id: agent.id, capabilities: agent.capabilities, scopes: agent.scopes },
+          space_id: req.params.space_id,
+          view: view ?? null,
+          actor: req.actor
+        },
+        onEvent: (e) => send(e.type, e)
+      });
+    } catch (e) {
+      send('error', { message: String(e?.message || e) });
+      return res.end();
+    }
+
+    const assistant = await messages.append(convo.id, {
+      role: 'assistant', body: result.text, agent_id: agent.id,
+      metadata: { tool_trace: result.toolTrace, draft_ids: result.draftIds, usage: result.usage }
+    });
+
+    send('done', { assistant_message_id: assistant.id, draft_ids: result.draftIds, usage: result.usage });
+    res.end();
+  })
+);