fix(model): respect task_metadata.json model selection (#415)

Model selection from UI was ignored because cli/main.py always
defaulted to Opus when no CLI arg was provided. This caused
get_phase_model() to bypass task_metadata.json since it treats
any non-None cli_model as an explicit override.

Backend fixes:
- Remove DEFAULT_MODEL fallback in cli/main.py so model is None
  when not explicitly set
- Update planner.py to use get_phase_model() like other agents

Frontend fixes:
- Sync defaultModel with selectedAgentProfile on save
- Add migration for existing users to fix stuck defaultModel

Closes #414

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

apps/backend/agents/planner.py

@@ -9,7 +9,7 @@ import logging
 from pathlib import Path
 
 from core.client import create_client
-from phase_config import get_phase_thinking_budget
+from phase_config import get_phase_model, get_phase_thinking_budget
 from phase_event import ExecutionPhase, emit_phase
 from task_logger import (
     LogPhase,
@@ -91,12 +91,14 @@ async def run_followup_planner(
         task_logger.start_phase(LogPhase.PLANNING, "Starting follow-up planning...")
         task_logger.set_session(1)
 
-    # Create client (fresh context) with planning phase thinking budget
+    # Create client with phase-specific model and thinking budget
+    # Respects task_metadata.json configuration when no CLI override
+    planning_model = get_phase_model(spec_dir, "planning", model)
     planning_thinking_budget = get_phase_thinking_budget(spec_dir, "planning")
     client = create_client(
         project_dir,
         spec_dir,
-        model,
+        planning_model,
         max_thinking_tokens=planning_thinking_budget,
     )
 

apps/backend/cli/main.py

@@ -276,8 +276,9 @@ def main() -> None:
     project_dir = get_project_dir(args.project_dir)
     debug("run.py", f"Using project directory: {project_dir}")
 
-    # Get model (with env var fallback)
-    model = args.model or os.environ.get("AUTO_BUILD_MODEL", DEFAULT_MODEL)
+    # Get model from CLI arg or env var (None if not explicitly set)
+    # This allows get_phase_model() to fall back to task_metadata.json
+    model = args.model or os.environ.get("AUTO_BUILD_MODEL")
 
     # Handle --list command
     if args.list:

apps/frontend/src/main/ipc-handlers/settings-handlers.ts

@@ -3,7 +3,7 @@ import { existsSync, writeFileSync, mkdirSync, statSync } from 'fs';
 import { execFileSync } from 'node:child_process';
 import path from 'path';
 import { is } from '@electron-toolkit/utils';
-import { IPC_CHANNELS, DEFAULT_APP_SETTINGS } from '../../shared/constants';
+import { IPC_CHANNELS, DEFAULT_APP_SETTINGS, DEFAULT_AGENT_PROFILES } from '../../shared/constants';
 import type {
   AppSettings,
   IPCResult
@@ -111,6 +111,19 @@ export function registerSettingsHandlers(
         needsSave = true;
       }
 
+      // Migration: Sync defaultModel with selectedAgentProfile (#414)
+      // Fixes bug where defaultModel was stuck at 'opus' regardless of profile selection
+      if (!settings._migratedDefaultModelSync) {
+        if (settings.selectedAgentProfile) {
+          const profile = DEFAULT_AGENT_PROFILES.find(p => p.id === settings.selectedAgentProfile);
+          if (profile) {
+            settings.defaultModel = profile.model;
+          }
+        }
+        settings._migratedDefaultModelSync = true;
+        needsSave = true;
+      }
+
       // If no manual autoBuildPath is set, try to auto-detect
       if (!settings.autoBuildPath) {
         const detectedPath = detectAutoBuildSourcePath();
@@ -149,6 +162,15 @@ export function registerSettingsHandlers(
         const savedSettings = readSettingsFile();
         const currentSettings = { ...DEFAULT_APP_SETTINGS, ...savedSettings };
         const newSettings = { ...currentSettings, ...settings };
+
+        // Sync defaultModel when agent profile changes (#414)
+        if (settings.selectedAgentProfile) {
+          const profile = DEFAULT_AGENT_PROFILES.find(p => p.id === settings.selectedAgentProfile);
+          if (profile) {
+            newSettings.defaultModel = profile.model;
+          }
+        }
+
         writeFileSync(settingsPath, JSON.stringify(newSettings, null, 2));
 
         // Apply Python path if changed

apps/frontend/src/shared/types/settings.ts

@@ -255,6 +255,7 @@ export interface AppSettings {
   betaUpdates?: boolean;
   // Migration flags (internal use)
   _migratedAgentProfileToAuto?: boolean;
+  _migratedDefaultModelSync?: boolean;
   // Language preference for UI (i18n)
   language?: SupportedLanguage;
   // Developer tools preferences