diff --git a/apps/server/src/core/base/query-cache/base-query-cache.service.ts b/apps/server/src/core/base/query-cache/base-query-cache.service.ts
index 1531362b..e01726dc 100644
--- a/apps/server/src/core/base/query-cache/base-query-cache.service.ts
+++ b/apps/server/src/core/base/query-cache/base-query-cache.service.ts
@@ -166,6 +166,18 @@ export class BaseQueryCacheService
       },
     });
 
+    if (this.env?.getBaseQueryCacheTrace?.() ?? false) {
+      console.log(
+        '[cache-trace]',
+        JSON.stringify({
+          phase: 'query.sql',
+          baseId: baseId.slice(0, 8),
+          sql,
+          params,
+        }),
+      );
+    }
+
     const prepared = await collection.connection.prepare(sql);
     for (let i = 0; i < params.length; i++) {
       const p = params[i];
@@ -296,6 +308,17 @@ export class BaseQueryCacheService
    */
   async applyChange(env: ChangeEnvelope): Promise<void> {
     const collection = this.collections.get(env.baseId);
+    if (this.env?.getBaseQueryCacheTrace?.() ?? false) {
+      console.log(
+        '[cache-trace]',
+        JSON.stringify({
+          phase: 'pubsub.apply',
+          baseId: env.baseId.slice(0, 8),
+          kind: env.kind,
+          resident: !!collection,
+        }),
+      );
+    }
     if (!collection) return;
 
     try {
diff --git a/apps/server/src/core/base/query-cache/base-query-cache.write-consumer.ts b/apps/server/src/core/base/query-cache/base-query-cache.write-consumer.ts
index 83198a04..1a818d3d 100644
--- a/apps/server/src/core/base/query-cache/base-query-cache.write-consumer.ts
+++ b/apps/server/src/core/base/query-cache/base-query-cache.write-consumer.ts
@@ -146,6 +146,21 @@ export class BaseQueryCacheWriteConsumer {
     envelope: ChangeEnvelope,
   ): Promise<void> {
     const channel = `base-query-cache:changes:${baseId}`;
+    if (this.configProvider.config.trace) {
+      console.log(
+        '[cache-trace]',
+        JSON.stringify({
+          phase: 'pubsub.publish',
+          baseId,
+          kind: envelope.kind,
+          // Include the row id or similar short discriminator where meaningful,
+          // but don't dump the full envelope — it can be large (row-upsert ships
+          // the whole row).
+          ...('rowId' in envelope ? { rowId: envelope.rowId } : {}),
+          ...('rowIds' in envelope ? { rowCount: envelope.rowIds.length } : {}),
+        }),
+      );
+    }
     try {
       await this.redis.publish(channel, JSON.stringify(envelope));
     } catch (err) {
diff --git a/apps/server/src/core/base/query-cache/base-query-router.ts b/apps/server/src/core/base/query-cache/base-query-router.ts
index 795ce8f7..c0540ebb 100644
--- a/apps/server/src/core/base/query-cache/base-query-router.ts
+++ b/apps/server/src/core/base/query-cache/base-query-router.ts
@@ -26,15 +26,34 @@ export class BaseQueryRouter {
 
   async decide(args: RouteDecideArgs): Promise<RouteDecision> {
     const { enabled, minRows } = this.configProvider.config;
-    if (!enabled) return 'postgres';
+    const trace = this.configProvider.config.trace ?? false;
+
+    const emit = (route: RouteDecision, reason: string): RouteDecision => {
+      if (trace) {
+        console.log(
+          '[cache-trace]',
+          JSON.stringify({
+            phase: 'router.decision',
+            baseId: args.baseId,
+            route,
+            reason,
+          }),
+        );
+      }
+      return route;
+    };
+
+    if (!enabled) return emit('postgres', 'flag disabled');
 
     const hasFilter = !!args.filter;
     const hasSorts = !!args.sorts && args.sorts.length > 0;
     const hasSearch = !!args.search;
-    if (!hasFilter && !hasSorts && !hasSearch) return 'postgres';
+    if (!hasFilter && !hasSorts && !hasSearch) {
+      return emit('postgres', 'no filter/sort/search');
+    }
 
     // v1: any search stays on Postgres — loader doesn't populate search_text yet.
-    if (hasSearch) return 'postgres';
+    if (hasSearch) return emit('postgres', 'search requires postgres');
 
     // Fast path: if the collection is already resident, read the cached
     // row count instead of running a Postgres COUNT on every request.
@@ -52,8 +71,16 @@ export class BaseQueryRouter {
           }),
         );
       }
-      if (resident.rowCount < minRows) return 'postgres';
-      return 'cache';
+      if (resident.rowCount < minRows) {
+        return emit(
+          'postgres',
+          `rowCount=${resident.rowCount} below MIN_ROWS=${minRows}`,
+        );
+      }
+      return emit(
+        'cache',
+        `qualified: rowCount=${resident.rowCount}, hasFilter=${hasFilter}, hasSort=${hasSorts}`,
+      );
     }
 
     const debug = this.env?.getBaseQueryCacheDebug() ?? false;
@@ -73,8 +100,13 @@ export class BaseQueryRouter {
         }),
       );
     }
-    if (count < minRows) return 'postgres';
+    if (count < minRows) {
+      return emit('postgres', `rowCount=${count} below MIN_ROWS=${minRows}`);
+    }
 
-    return 'cache';
+    return emit(
+      'cache',
+      `qualified: rowCount=${count}, hasFilter=${hasFilter}, hasSort=${hasSorts}`,
+    );
   }
 }
diff --git a/apps/server/src/core/base/query-cache/collection-loader.ts b/apps/server/src/core/base/query-cache/collection-loader.ts
index 33b4852d..5ac18c88 100644
--- a/apps/server/src/core/base/query-cache/collection-loader.ts
+++ b/apps/server/src/core/base/query-cache/collection-loader.ts
@@ -50,6 +50,17 @@ export class CollectionLoader {
       // server-side via the base_cell_* helpers; DuckDB streams typed
       // columns over COPY BINARY into its vectorized insert path.
       const sql = buildLoaderSql(specs, baseId, workspaceId);
+      if (this.config.config.trace) {
+        console.log(
+          '[cache-trace]',
+          JSON.stringify({
+            phase: 'loader.sql',
+            baseId,
+            length: sql.length,
+            sql,
+          }),
+        );
+      }
       await connection.run(sql);
 
       // Release the PG connection held by the ATTACH — we're done with
@@ -60,9 +71,21 @@ export class CollectionLoader {
       for (const spec of specs) {
         if (!spec.indexable) continue;
         const safe = spec.column.replace(/[^a-zA-Z0-9_]/g, '_');
+        const tIdx = this.config.config.trace ? Date.now() : 0;
         await connection.run(
           `CREATE INDEX ${quoteIdent(`idx_${safe}`)} ON rows (${quoteIdent(spec.column)})`,
         );
+        if (this.config.config.trace) {
+          console.log(
+            '[cache-trace]',
+            JSON.stringify({
+              phase: 'loader.index',
+              baseId,
+              column: spec.column,
+              ms: Date.now() - tIdx,
+            }),
+          );
+        }
       }
 
       const countResult = await connection.runAndReadAll(
diff --git a/apps/server/src/core/base/query-cache/query-cache.config.ts b/apps/server/src/core/base/query-cache/query-cache.config.ts
index ffc78ac8..3dafbc89 100644
--- a/apps/server/src/core/base/query-cache/query-cache.config.ts
+++ b/apps/server/src/core/base/query-cache/query-cache.config.ts
@@ -8,6 +8,7 @@ export type QueryCacheConfig = {
   warmTopN: number;
   memoryLimit: string;
   threads: number;
+  trace: boolean;
 };
 
 @Injectable()
@@ -21,6 +22,7 @@ export class QueryCacheConfigProvider {
       warmTopN: env.getBaseQueryCacheWarmTopN(),
       memoryLimit: env.getBaseQueryCacheMemoryLimit(),
       threads: env.getBaseQueryCacheThreads(),
+      trace: env.getBaseQueryCacheTrace(),
     };
   }
 }
diff --git a/apps/server/src/integrations/environment/environment.service.ts b/apps/server/src/integrations/environment/environment.service.ts
index a53dbb7f..ffe96a15 100644
--- a/apps/server/src/integrations/environment/environment.service.ts
+++ b/apps/server/src/integrations/environment/environment.service.ts
@@ -344,6 +344,14 @@ export class EnvironmentService {
     );
   }
 
+  getBaseQueryCacheTrace(): boolean {
+    return (
+      this.configService
+        .get<string>('BASE_QUERY_CACHE_TRACE', 'false')
+        .toLowerCase() === 'true'
+    );
+  }
+
   getBaseQueryCacheMemoryLimit(): string {
     // Per-DuckDB-instance memory ceiling. DuckDB accepts human-readable sizes:
     // '32MB', '128MB', '1GB'. Default keeps a single instance from