systeminit · stack72 · Mar 31, 2026 · Mar 31, 2026
diff --git a/packages/testing/datastore_types.ts b/packages/testing/datastore_types.ts
@@ -68,8 +68,8 @@ export interface DatastoreVerifier {
 
 /** Interface for datastore synchronization services. */
 export interface DatastoreSyncService {
-  pullChanged(): Promise<void>;
-  pushChanged(): Promise<void>;
+  pullChanged(): Promise<number | void>;
+  pushChanged(): Promise<number | void>;
 }
 
 /**

diff --git a/src/domain/datastore/datastore_sync_service.ts b/src/domain/datastore/datastore_sync_service.ts
@@ -25,7 +25,7 @@
  */
 export interface DatastoreSyncService {
   /** Pull changed files from the remote datastore to the local cache. */
-  pullChanged(): Promise<void>;
+  pullChanged(): Promise<number | void>;
   /** Push changed files from the local cache to the remote datastore. */
-  pushChanged(): Promise<void>;
+  pushChanged(): Promise<number | void>;
 }
diff --git a/src/infrastructure/persistence/default_datastore_path_resolver.ts b/src/infrastructure/persistence/default_datastore_path_resolver.ts
@@ -52,8 +52,12 @@ export class DefaultDatastorePathResolver implements DatastorePathResolver {
 
     // Determine the base path for the datastore
     if (isCustomDatastoreConfig(datastoreConfig)) {
-      // Custom: path was eagerly resolved during config resolution
-      this.datastoreBasePath = datastoreConfig.datastorePath;
+      // For remote datastores with a local cache (e.g. S3), use the cache
+      // path so reads/writes go to the same directory the sync service
+      // pushes from and pulls to.  Fall back to datastorePath for custom
+      // datastores that don't use a separate cache.
+      this.datastoreBasePath = datastoreConfig.cachePath ??
+        datastoreConfig.datastorePath;
     } else {
       this.datastoreBasePath = datastoreConfig.path;
     }

diff --git a/src/infrastructure/persistence/default_datastore_path_resolver_test.ts b/src/infrastructure/persistence/default_datastore_path_resolver_test.ts
@@ -147,6 +147,38 @@ Deno.test("DefaultDatastorePathResolver - default config (no external datastore)
   );
 });
 
+Deno.test("DefaultDatastorePathResolver - custom datastore prefers cachePath over datastorePath", () => {
+  const config: DatastoreConfig = {
+    type: "s3",
+    config: { bucket: "my-bucket" },
+    datastorePath: "/repo/.swamp",
+    cachePath: "/home/user/.swamp/repos/abc",
+  };
+  const resolver = new DefaultDatastorePathResolver("/repo", config);
+  // Data should go to cachePath so the sync service can find it
+  assertEquals(
+    resolver.datastorePath("data"),
+    "/home/user/.swamp/repos/abc/data",
+  );
+  assertEquals(
+    resolver.resolvePath("data", "foo"),
+    "/home/user/.swamp/repos/abc/data/foo",
+  );
+});
+
+Deno.test("DefaultDatastorePathResolver - custom datastore falls back to datastorePath without cachePath", () => {
+  const config: DatastoreConfig = {
+    type: "custom",
+    config: {},
+    datastorePath: "/shared/datastore",
+  };
+  const resolver = new DefaultDatastorePathResolver("/repo", config);
+  assertEquals(
+    resolver.datastorePath("data"),
+    "/shared/datastore/data",
+  );
+});
+
 Deno.test("DefaultDatastorePathResolver - config returns the stored config", () => {
   const config: DatastoreConfig = {
     type: "filesystem",

diff --git a/src/libswamp/datastores/sync.ts b/src/libswamp/datastores/sync.ts
@@ -93,17 +93,21 @@ export function createDatastoreSyncDeps(
       validateSyncSupport: () =>
         Promise.resolve({ supported: true, type: config.type }),
       pushSync: async () => {
-        await syncService.pushChanged();
-        return { filesPushed: 0 };
+        const count = await syncService.pushChanged();
+        return { filesPushed: typeof count === "number" ? count : 0 };
       },
       pullSync: async () => {
-        await syncService.pullChanged();
-        return { filesPulled: 0 };
+        const count = await syncService.pullChanged();
+        return { filesPulled: typeof count === "number" ? count : 0 };
       },
       fullSync: async () => {
-        await syncService.pullChanged();
-        await syncService.pushChanged();
-        return { filesPulled: 0, filesPushed: 0, errors: [] };
+        const pulled = await syncService.pullChanged();
+        const pushed = await syncService.pushChanged();
+        return {
+          filesPulled: typeof pulled === "number" ? pulled : 0,
+          filesPushed: typeof pushed === "number" ? pushed : 0,
+          errors: [],
+        };
       },
     };
   }