Merge NeuroSploit v3.3.0 — Autonomous MD-Agent Engine into main

# Conflicts:
#	prompts/task_library.json

backend/core/smart_router/provider_registry.py

@@ -88,7 +88,7 @@ DEFAULT_PROVIDERS: List[Dict] = [
     {
         "id": "claude_code", "name": "Claude Code", "auth_type": "oauth",
         "api_format": "anthropic", "base_url": "https://api.anthropic.com",
-        "tier": 1, "default_model": "claude-sonnet-4-5-20250929",
+        "tier": 1, "default_model": "claude-sonnet-4-20250514",
     },
     {
         "id": "codex_cli", "name": "OpenAI Codex CLI", "auth_type": "oauth",
@@ -123,13 +123,13 @@ DEFAULT_PROVIDERS: List[Dict] = [
     {
         "id": "kiro", "name": "Kiro AI", "auth_type": "oauth",
         "api_format": "anthropic", "base_url": "https://api.anthropic.com",
-        "tier": 1, "default_model": "claude-sonnet-4-5-20250929",
+        "tier": 1, "default_model": "claude-sonnet-4-20250514",
     },
     # === API Key Providers (Tier 1 - Paid) ===
     {
         "id": "anthropic", "name": "Anthropic", "auth_type": "api_key",
         "api_format": "anthropic", "base_url": "https://api.anthropic.com",
-        "tier": 1, "default_model": "claude-sonnet-4-5-20250929",
+        "tier": 1, "default_model": "claude-sonnet-4-20250514",
         "env_key": "ANTHROPIC_API_KEY",
     },
     {
@@ -147,7 +147,7 @@ DEFAULT_PROVIDERS: List[Dict] = [
     {
         "id": "openrouter", "name": "OpenRouter", "auth_type": "api_key",
         "api_format": "openai_compat", "base_url": "https://openrouter.ai/api/v1",
-        "tier": 1, "default_model": "anthropic/claude-sonnet-4-5",
+        "tier": 1, "default_model": "anthropic/claude-sonnet-4-20250514",
         "env_key": "OPENROUTER_API_KEY",
     },
     # === API Key Providers (Tier 2 - Cheap) ===

backend/core/smart_router/router.py

@@ -173,41 +173,41 @@ class SmartRouter:
     ) -> List[Tuple[Provider, Account]]:
         """Build ordered list of (provider, account) candidates.
 
-        If preferred is set, ONLY that provider is used (no fallback to others).
-        This ensures the user's explicit choice is respected.
+        If preferred is set, that provider is tried FIRST, then falls back
+        to other providers of the same tier if all accounts fail.
         If preferred is not set, all providers are tried by tier.
         """
         candidates = []
+        seen_account_ids = set()
 
         if preferred:
-            # Strict mode: only the preferred provider
+            # Preferred provider goes first in candidate list
             provider = self.registry.get_provider(preferred)
             if provider:
                 accounts = self.registry.get_active_accounts(preferred)
                 for acct in accounts:
                     if self.quota.is_available(acct.id):
                         candidates.append((provider, acct))
+                        seen_account_ids.add(acct.id)
                 if not candidates:
                     logger.warning(
                         f"SmartRouter: Preferred provider '{preferred}' has no active accounts! "
                         f"Falling back to all providers."
                     )
-                else:
-                    return candidates  # Only preferred provider candidates
 
-        # Auto mode or preferred has no active accounts: try all by tier
+        # Add remaining providers as fallback (by tier)
         for tier in (1, 2, 3):
             providers = self.registry.get_providers_by_tier(tier)
             for provider in providers:
-                # Skip disabled providers
                 if not getattr(provider, "enabled", True):
                     continue
                 acct = self.quota.next_account(
                     provider.id,
                     self.registry.get_active_accounts(provider.id),
                 )
-                if acct:
+                if acct and acct.id not in seen_account_ids:
                     candidates.append((provider, acct))
+                    seen_account_ids.add(acct.id)
 
         return candidates