chat: surface OpenCode models in the picker (Phase 2)

list-models.ts now merges the OpenCode catalog (from `opencode models`, cached;
ids are providerID/modelID) with the static Claude tiers, so /chat/models returns
both. invalidateModelCache clears the OpenCode cache for real now.

Adds the 'opencode' → 'OpenCode Zen' provider label in the /models response and the
ModelSelector's PROVIDER_DISPLAY. The existing useModels visibility gates already
pass non-claude-code providers through, so no gate changes are needed — Super Admin
sees all models. Selecting any non-claude-code model routes the turn to the OpenCode
harness (Phase 1).

Default model stays 'claude-code'. 58 OpenCode Zen models currently list; curating to
a flagship subset is an easy follow-up if the full catalog is unwieldy.

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

src/servers/api/chat/chat.ts

@@ -62,7 +62,7 @@ chatRouter.patch('/sessions/:id/title', async (ctx) => {
 chatRouter.get('/models', async (ctx: Context) => {
   try {
     const models = await listChatModels();
-    const providerNames: Record<string, string> = { 'claude-code': 'Claude Code' };
+    const providerNames: Record<string, string> = { 'claude-code': 'Claude Code', opencode: 'OpenCode Zen' };
     return ctx.json({ models, providerNames, hostHome: process.env.HOME ?? '' });
   } catch (err) {
     logger.error('Failed to list models', { error: String(err) });

src/servers/api/chat/list-models.ts

@@ -1,16 +1,60 @@
 import type { ModelInfo } from './types';
+import { homedir } from 'os';
+import { join } from 'path';
 
-// Claude-only. The runner is the `claude` CLI, so the model list is a fixed set of Claude tiers.
+// The Claude harness runs the `claude` CLI, so its tiers are a fixed set.
 const CLAUDE_CODE_MODELS: ModelInfo[] = [
   { id: 'claude-code/opus', name: 'opus', provider: 'claude-code', contextWindow: 200000, maxTokens: 16000, reasoning: true, images: true },
   { id: 'claude-code/sonnet', name: 'sonnet', provider: 'claude-code', contextWindow: 200000, maxTokens: 16000, reasoning: true, images: true },
   { id: 'claude-code/haiku', name: 'haiku', provider: 'claude-code', contextWindow: 200000, maxTokens: 8192, reasoning: false, images: true },
 ];
 
+const OPENCODE_BIN = process.env.OPENCODE_BIN || join(homedir(), '.opencode', 'bin', 'opencode');
+
+// Cache the OpenCode catalog; it's stable for a session and `opencode models` costs a subprocess.
+let openCodeCache: ModelInfo[] | null = null;
+
 export function invalidateModelCache(): void {
-  // No-op: the Claude model list is static. Kept for call-site compatibility.
+  openCodeCache = null;
+}
+
+// Enumerate OpenCode models via `opencode models` (ids are `providerID/modelID`, e.g.
+// `opencode/claude-opus-4-8`). Metadata (context/tokens/modalities) is left at neutral defaults for
+// now — it can be enriched later from a serve's GET /config/providers.
+async function listOpenCodeModels(): Promise<ModelInfo[]> {
+  if (openCodeCache) return openCodeCache;
+  try {
+    const proc = Bun.spawn([OPENCODE_BIN, 'models'], { stdout: 'pipe', stderr: 'ignore' });
+    const out = await new Response(proc.stdout).text();
+    await proc.exited;
+
+    const models: ModelInfo[] = out
+      // eslint-disable-next-line no-control-regex
+      .replace(/\x1b\[[0-9;]*m/g, '')
+      .split('\n')
+      .map((line) => line.trim())
+      .filter((line) => line.includes('/'))
+      .map((full) => {
+        const slash = full.indexOf('/');
+        return {
+          id: full,
+          name: full.slice(slash + 1),
+          provider: full.slice(0, slash),
+          contextWindow: 200000,
+          maxTokens: 8192,
+          reasoning: false,
+          images: true,
+        } satisfies ModelInfo;
+      });
+
+    openCodeCache = models;
+    return models;
+  } catch {
+    return [];
+  }
 }
 
 export async function listChatModels(): Promise<ModelInfo[]> {
-  return [...CLAUDE_CODE_MODELS];
+  const openCode = await listOpenCodeModels();
+  return [...CLAUDE_CODE_MODELS, ...openCode];
 }