[gemini] feat: Add Claude API fallback tier to cascade.py (#980) (#1119)

Co-authored-by: Google Gemini <gemini@hermes.local>
Co-committed-by: Google Gemini <gemini@hermes.local>

src/infrastructure/router/cascade.py

@@ -114,6 +114,7 @@ class Provider:
     type: str  # ollama, openai, anthropic
     enabled: bool
     priority: int
+    tier: str | None = None # e.g., "local", "standard_cloud", "frontier"
     url: str | None = None
     api_key: str | None = None
     base_url: str | None = None
@@ -267,6 +268,7 @@ class CascadeRouter:
                 type=p_data["type"],
                 enabled=p_data.get("enabled", True),
                 priority=p_data.get("priority", 99),
+                tier=p_data.get("tier"),
                 url=p_data.get("url"),
                 api_key=p_data.get("api_key"),
                 base_url=p_data.get("base_url"),
@@ -532,6 +534,7 @@ class CascadeRouter:
         model: str | None = None,
         temperature: float = 0.7,
         max_tokens: int | None = None,
+        cascade_tier: str | None = None,
     ) -> dict:
         """Complete a chat conversation with automatic failover.
 
@@ -545,6 +548,8 @@ class CascadeRouter:
             model: Preferred model (tries this first, then provider defaults)
             temperature: Sampling temperature
             max_tokens: Maximum tokens to generate
+            cascade_tier: If specified, filters providers by this tier.
+                - "frontier_required": Uses only Anthropic provider for top-tier models.
 
         Returns:
             Dict with content, provider_used, and metrics
@@ -558,7 +563,18 @@ class CascadeRouter:
 
         errors = []
 
-        for provider in self.providers:
+        providers = self.providers
+        if cascade_tier == "frontier_required":
+            providers = [p for p in self.providers if p.type == "anthropic"]
+            if not providers:
+                raise RuntimeError("No Anthropic provider configured for 'frontier_required' tier.")
+        elif cascade_tier:
+            providers = [p for p in self.providers if p.tier == cascade_tier]
+            if not providers:
+                raise RuntimeError(f"No providers found for tier: {cascade_tier}")
+
+
+        for provider in providers:
             if not self._is_provider_available(provider):
                 continue