feat: add jam models set command, read default model from bridge file

Author: sunilp

src/commands/completion.ts

@@ -48,7 +48,7 @@ function generateBashCompletion(): string {
     '      return 0',
     '      ;;',
     '    models)',
-    '      COMPREPLY=( $(compgen -W "list" -- "${cur}") )',
+    '      COMPREPLY=( $(compgen -W "list set" -- "${cur}") )',
     '      return 0',
     '      ;;',
     '    history)',
@@ -85,7 +85,7 @@ function generateZshCompletion(): string {
     '  local -a auth_cmds config_cmds models_cmds history_cmds completion_cmds',
     "  auth_cmds=('login' 'logout')",
     "  config_cmds=('show' 'init')",
-    "  models_cmds=('list')",
+    "  models_cmds=('list' 'set')",
     "  history_cmds=('list' 'show')",
     "  completion_cmds=('install')",
     '',
@@ -127,7 +127,7 @@ function generatePowerShellCompletion(): string {
     '  $subcommands = @{',
     "    'auth' = @('login', 'logout')",
     "    'config' = @('show', 'init')",
-    "    'models' = @('list')",
+    "    'models' = @('list', 'set')",
     "    'history' = @('list', 'show')",
     "    'completion' = @('install')",
     '  }',

src/commands/models.ts

@@ -2,6 +2,58 @@ import { loadConfig, getActiveProfile } from '../config/loader.js';
 import { createProvider } from '../providers/factory.js';
 import { JamError } from '../utils/errors.js';
 import type { CliOverrides } from '../config/schema.js';
+import { readFile, writeFile, mkdir } from 'node:fs/promises';
+import { join } from 'node:path';
+import { homedir } from 'node:os';
+
+export async function runModelsSet(model: string, options: CliOverrides): Promise<void> {
+  try {
+    // Validate: list available models and check if the requested one exists
+    const config = await loadConfig(process.cwd(), options);
+    const profile = getActiveProfile(config);
+    const adapter = await createProvider(profile);
+
+    let available: string[];
+    try {
+      available = await adapter.listModels();
+    } catch {
+      available = [];
+    }
+
+    if (available.length > 0 && !available.includes(model)) {
+      process.stderr.write(`Warning: "${model}" not found in available models for ${profile.provider}.\n`);
+      process.stderr.write(`Available: ${available.join(', ')}\n\n`);
+      process.stderr.write(`Setting it anyway — it may work if the provider accepts it.\n\n`);
+    }
+
+    // Read or create ~/.jam/config.json
+    const configDir = join(homedir(), '.jam');
+    const configPath = join(configDir, 'config.json');
+
+    let existing: Record<string, unknown> = {};
+    try {
+      existing = JSON.parse(await readFile(configPath, 'utf-8')) as Record<string, unknown>;
+    } catch { /* file doesn't exist yet */ }
+
+    // Merge the model into the active profile
+    const profileName = (existing['defaultProfile'] as string) ?? 'default';
+    const profiles = (existing['profiles'] ?? {}) as Record<string, Record<string, unknown>>;
+    const activeProfile = profiles[profileName] ?? {};
+
+    profiles[profileName] = { ...activeProfile, model };
+    existing['profiles'] = profiles;
+
+    await mkdir(configDir, { recursive: true });
+    await writeFile(configPath, JSON.stringify(existing, null, 2) + '\n');
+
+    process.stdout.write(`Model set to "${model}" for profile "${profileName}".\n`);
+    process.stdout.write(`Config: ${configPath}\n`);
+  } catch (err) {
+    const jamErr = JamError.fromUnknown(err);
+    process.stderr.write(`Error: ${jamErr.message}\n`);
+    process.exit(1);
+  }
+}
 
 export async function runModelsList(options: CliOverrides): Promise<void> {
   try {

src/config/loader.ts

@@ -144,30 +144,35 @@ async function isCopilotCliInstalled(): Promise<boolean> {
  * The VSCode extension writes this file when the proxy starts.
  * Falls back to JAM_VSCODE_LM_PORT env var.
  */
-function readBridgePort(): string | null {
+interface BridgeInfo {
+  port: string;
+  model?: string;
+}
+
+function readBridgeInfo(): BridgeInfo | null {
   if (process.env['JAM_VSCODE_LM_PORT']) {
-    return process.env['JAM_VSCODE_LM_PORT'];
+    return { port: process.env['JAM_VSCODE_LM_PORT'] };
   }
   try {
     const bridgePath = join(homedir(), '.jam', 'copilot-bridge.json');
-    const data = JSON.parse(readFileSync(bridgePath, 'utf-8')) as { port?: number; pid?: number };
+    const data = JSON.parse(readFileSync(bridgePath, 'utf-8')) as { port?: number; pid?: number; model?: string };
     if (data.port) {
       // Verify the VSCode process is still running
       if (data.pid) {
         try { process.kill(data.pid, 0); } catch { return null; } // process gone
       }
-      return String(data.port);
+      return { port: String(data.port), model: data.model };
     }
   } catch { /* file doesn't exist or invalid */ }
   return null;
 }
 
 async function detectBestProvider(): Promise<{ provider: string; model?: string } | null> {
   // 1. VSCode Copilot proxy (env var or bridge file)
-  const bridgePort = readBridgePort();
-  if (bridgePort) {
-    process.env['JAM_VSCODE_LM_PORT'] = bridgePort; // propagate for downstream use
-    return { provider: 'copilot' };
+  const bridge = readBridgeInfo();
+  if (bridge) {
+    process.env['JAM_VSCODE_LM_PORT'] = bridge.port; // propagate for downstream use
+    return { provider: 'copilot', model: bridge.model };
   }
 
   // 2. Copilot CLI (@github/copilot)

src/index.ts

@@ -331,6 +331,15 @@ models
     await runModelsList({ profile: g.profile, provider: g.provider, baseUrl: g.baseUrl });
   });
 
+models
+  .command('set <model>')
+  .description('Set the default model for the current provider')
+  .action(async (model: string) => {
+    const g = globalOpts();
+    const { runModelsSet } = await import('./commands/models.js');
+    await runModelsSet(model, { profile: g.profile, provider: g.provider, baseUrl: g.baseUrl });
+  });
+
 // ── history ───────────────────────────────────────────────────────────────────
 const history = program.command('history').description('Manage chat session history');