feat: wire OpenCode as selectable agent backend via AGENT_BACKEND env var

- Add AGENT_BACKEND config ('container' default, 'opencode' to use OpenCode runtime)
- Wire OpenCodeRuntime into runAgent() with fallback to container runner
- Skip container system check when using OpenCode backend
- Update README and CLAUDE.md with AGENT_BACKEND docs

src/index.ts

@@ -3,6 +3,7 @@ import fs from 'fs';
 import path from 'path';
 
 import {
+  AGENT_BACKEND,
   ASSISTANT_NAME,
   DATA_DIR,
   DISCORD_BOT_TOKEN,
@@ -16,7 +17,107 @@ import { DiscordChannel } from './channels/discord.js';
 import { WhatsAppChannel } from './channels/whatsapp.js';
 import {
   ContainerOutput,
-  runContainerAgent,
+  async function runAgent(
+    group: RegisteredGroup,
+    prompt: string,
+    chatJid: string,
+    onOutput?: (output: ContainerOutput) => Promise<void>,
+  ): Promise<'success' | 'error'> {
+    // --- OpenCode backend ---
+    if (opencode) {
+      try {
+        const response = await opencode.chat(prompt, chatJid);
+        if (response.error) {
+          logger.error({ group: group.name, error: response.error }, 'OpenCode agent error');
+          if (onOutput) {
+            await onOutput({ status: 'error', error: response.error, result: null, newSessionId: response.sessionId });
+          }
+          return 'error';
+        }
+        if (onOutput && response.text) {
+          await onOutput({ status: 'success', result: response.text, error: null, newSessionId: response.sessionId });
+        }
+        return 'success';
+      } catch (err) {
+        logger.error({ group: group.name, err }, 'OpenCode agent error');
+        return 'error';
+      }
+    }
+
+    // --- Container backend (Claude Agent SDK) ---
+    const isMain = group.folder === MAIN_GROUP_FOLDER;
+    const sessionId = sessions[group.folder];
+
+    // Update tasks snapshot for container to read (filtered by group)
+    const tasks = getAllTasks();
+    writeTasksSnapshot(
+      group.folder,
+      isMain,
+      tasks.map((t) => ({
+        id: t.id,
+        groupFolder: t.group_folder,
+        prompt: t.prompt,
+        schedule_type: t.schedule_type,
+        schedule_value: t.schedule_value,
+        status: t.status,
+        next_run: t.next_run,
+      })),
+    );
+
+    // Update available groups snapshot (main group only can see all groups)
+    const availableGroups = getAvailableGroups();
+    writeGroupsSnapshot(
+      group.folder,
+      isMain,
+      availableGroups,
+      new Set(Object.keys(registeredGroups)),
+    );
+
+    // Wrap onOutput to track session ID from streamed results
+    const wrappedOnOutput = onOutput
+      ? async (output: ContainerOutput) => {
+          if (output.newSessionId) {
+            sessions[group.folder] = output.newSessionId;
+            setSession(group.folder, output.newSessionId);
+          }
+          await onOutput(output);
+        }
+      : undefined;
+
+    try {
+      const output = await runContainerAgent(
+        group,
+        {
+          prompt,
+          sessionId,
+          groupFolder: group.folder,
+          chatJid,
+          isMain,
+        },
+        (proc, containerName) => queue.registerProcess(chatJid, proc, containerName, group.folder),
+        wrappedOnOutput,
+      );
+
+      if (output.newSessionId) {
+        sessions[group.folder] = output.newSessionId;
+        setSession(group.folder, output.newSessionId);
+      }
+
+      if (output.status === 'error') {
+        logger.error(
+          { group: group.name, error: output.error },
+          'Container agent error',
+        );
+        return 'error';
+      }
+
+      return 'success';
+    } catch (err) {
+      logger.error({ group: group.name, err }, 'Agent error');
+      return 'error';
+    }
+  }
+,
   writeGroupsSnapshot,
   writeTasksSnapshot,
 } from './container-runner.js';
@@ -41,6 +142,7 @@ import { findChannel, formatMessages, formatOutbound } from './router.js';
 import { startSchedulerLoop } from './task-scheduler.js';
 import { Channel, NewMessage, RegisteredGroup } from './types.js';
 import { logger } from './logger.js';
+import { OpenCodeRuntime } from './opencode/runtime.js';
 
 // Re-export for backwards compatibility during refactor
 export { escapeXml, formatMessages } from './router.js';
@@ -54,6 +156,7 @@ let messageLoopRunning = false;
 let whatsapp: WhatsAppChannel;
 const channels: Channel[] = [];
 const queue = new GroupQueue();
+const opencode = AGENT_BACKEND === 'opencode' ? new OpenCodeRuntime() : null;
 
 function loadState(): void {
   lastTimestamp = getRouterState('last_timestamp') || '';
@@ -221,6 +324,28 @@ async function runAgent(
   chatJid: string,
   onOutput?: (output: ContainerOutput) => Promise<void>,
 ): Promise<'success' | 'error'> {
+  // --- OpenCode backend ---
+  if (opencode) {
+    try {
+      const response = await opencode.chat(prompt, chatJid);
+      if (response.error) {
+        logger.error({ group: group.name, error: response.error }, 'OpenCode agent error');
+        if (onOutput) {
+          await onOutput({ status: 'error', error: response.error, result: null, newSessionId: response.sessionId });
+        }
+        return 'error';
+      }
+      if (onOutput && response.text) {
+        await onOutput({ status: 'success', result: response.text, error: null, newSessionId: response.sessionId });
+      }
+      return 'success';
+    } catch (err) {
+      logger.error({ group: group.name, err }, 'OpenCode agent error');
+      return 'error';
+    }
+  }
+
+  // --- Container backend (Claude Agent SDK) ---
   const isMain = group.folder === MAIN_GROUP_FOLDER;
   const sessionId = sessions[group.folder];
 
@@ -464,7 +589,11 @@ function ensureContainerSystemRunning(): void {
 }
 
 async function main(): Promise<void> {
-  ensureContainerSystemRunning();
+  if (AGENT_BACKEND === 'container') {
+    ensureContainerSystemRunning();
+  } else {
+    logger.info({ backend: AGENT_BACKEND }, 'Using OpenCode agent backend, skipping container system check');
+  }
   initDatabase();
   logger.info('Database initialized');
   loadState();