Add semantic caching

src/knowledge_search_mcp/__main__.py

@@ -67,6 +67,23 @@ async def knowledge_search(
             {"time_ms": round((t_embed - t0) * 1000, 1)},
         )
 
+        # Check semantic cache before vector search
+        if app.semantic_cache is not None and source is None:
+            cached = await app.semantic_cache.check(embedding)
+            if cached is not None:
+                t_cache = time.perf_counter()
+                log_structured_entry(
+                    "knowledge_search completed from cache",
+                    "INFO",
+                    {
+                        "embedding_ms": f"{round((t_embed - t0) * 1000, 1)}ms",
+                        "cache_check_ms": f"{round((t_cache - t_embed) * 1000, 1)}ms",
+                        "total_ms": f"{round((t_cache - t0) * 1000, 1)}ms",
+                        "cache_hit": True,
+                    },
+                )
+                return cached
+
         # Perform vector search
         log_structured_entry("Performing vector search", "INFO")
         try:
@@ -98,16 +115,23 @@ async def knowledge_search(
                 "source_filter": source.value if source is not None else None,
                 "results_count": len(filtered_results),
                 "chunks": [s["id"] for s in filtered_results],
+                "cache_hit": False,
             },
         )
 
         # Format and return results
+        formatted = format_search_results(filtered_results)
+
         if not filtered_results:
             log_structured_entry(
                 "No results found for query", "INFO", {"query": query[:100]}
             )
 
-        return format_search_results(filtered_results)
+        # Store in semantic cache (only for unfiltered queries with results)
+        if app.semantic_cache is not None and source is None and filtered_results:
+            await app.semantic_cache.store(query, formatted, embedding)
+
+        return formatted
 
     except Exception as e:  # noqa: BLE001
         # Catch-all for any unexpected errors