diff --git a/apps/server/src/orchestration-v2/ProjectionStore.test.ts b/apps/server/src/orchestration-v2/ProjectionStore.test.ts
index aadd9ecc8be0..4076e9194212 100644
--- a/apps/server/src/orchestration-v2/ProjectionStore.test.ts
+++ b/apps/server/src/orchestration-v2/ProjectionStore.test.ts
@@ -2097,6 +2097,69 @@ it.layer(layerTest)("ProjectionStoreV2", (it) => {
         byteIds,
         Array.from({ length: 70 }, (_, index) => `turn-item:bounded-sql-history:${index + 1}`),
       );
+
+      // Selected message reads recover ordinals for only the loaded messages, while 69
+      // unloaded assistant messages remain in the thread's history.
+      const firstMessageId = MessageId.make("message:bounded-sql-history:1");
+      const lastMessageId = MessageId.make("message:bounded-sql-history:1000");
+      const insertMessageItem = (
+        suffix: string,
+        itemThreadId: string,
+        ordinal: number,
+        messageId: string | null | undefined,
+      ) => sql`
+        INSERT INTO orchestration_v2_projection_turn_items (
+          turn_item_id, thread_id, run_id, node_id, provider_thread_id, provider_turn_id,
+          parent_item_id, ordinal, type, status, updated_at, payload_json
+        ) VALUES (
+          ${`turn-item:bounded-sql-history:ordinal-${suffix}`}, ${itemThreadId}, NULL, NULL, NULL,
+          NULL, NULL, ${ordinal}, 'assistant_message', 'completed', ${nowIso},
+          ${encodeUnknownJsonString({ messageId })}
+        )
+      `;
+      yield* insertMessageItem("duplicate", threadId, 0, lastMessageId);
+      yield* insertMessageItem(
+        "other-thread",
+        "thread:bounded-sql-history:other",
+        -1,
+        firstMessageId,
+      );
+      yield* insertMessageItem("null-id", threadId, -2, null);
+      yield* insertMessageItem("missing-id", threadId, -3, undefined);
+      const readMessageIds = (filter?: ProjectionStore.ProjectionRecordFilter) =>
+        projectionStore
+          .getThreadRecords(threadId, ["messages"], filter)
+          .pipe(Effect.map(({ messages }) => messages.map((message) => message.id)));
+      assert.deepEqual(yield* readMessageIds(), [lastMessageId, firstMessageId]);
+      assert.deepEqual(yield* readMessageIds({ messageRoles: ["user", "assistant"] }), [
+        lastMessageId,
+        firstMessageId,
+      ]);
+      for (const filter of [
+        {
+          messageIds: [
+            firstMessageId,
+            lastMessageId,
+            MessageId.make("message:bounded-sql-history:absent"),
+          ],
+        },
+        { messageRoles: ["user" as const] },
+        {
+          messageRunIds: [
+            RunId.make("run:bounded-sql-history:1"),
+            RunId.make("run:bounded-sql-history:1000"),
+          ],
+        },
+      ]) {
+        assert.deepEqual(yield* readMessageIds(filter), [lastMessageId, firstMessageId]);
+      }
+      assert.deepEqual(yield* readMessageIds({ messageIds: [] }), []);
+      assert.deepEqual(yield* readMessageIds({ messageIds: [firstMessageId] }), [firstMessageId]);
+      yield* sql`
+        DELETE FROM orchestration_v2_projection_turn_items
+        WHERE turn_item_id LIKE 'turn-item:bounded-sql-history:ordinal-%'
+      `;
+
       yield* sql`
         UPDATE orchestration_v2_projection_turn_items
         SET type = 'command_execution', payload_json = json_set(payload_json, '$.type', 'command_execution')
diff --git a/apps/server/src/orchestration-v2/ProjectionStore.ts b/apps/server/src/orchestration-v2/ProjectionStore.ts
index 975ce7b0b9c5..4d22c7b60ae3 100644
--- a/apps/server/src/orchestration-v2/ProjectionStore.ts
+++ b/apps/server/src/orchestration-v2/ProjectionStore.ts
@@ -3602,10 +3602,19 @@ export const layer: Layer.Layer<ProjectionStoreV2, never, SqlClient.SqlClient> =
         ]);
         const messageOrdinals = new Map<string, number>();
         if (fields !== undefined && fields.includes("messages") && messages.length > 1) {
+          // Broad role reads keep the original query to avoid per-ID lookup overhead.
+          const loadedMessageIds =
+            filter?.messageIds === undefined &&
+            filter?.messageRunIds === undefined &&
+            (filter?.messageRoles === undefined ||
+              (filter.messageRoles.includes("user") && filter.messageRoles.includes("assistant")))
+              ? undefined
+              : messages.map((message) => message.id);
           const rows = yield* sql<{ message_id: string; ordinal: number }>`
             SELECT json_extract(payload_json, '$.messageId') AS message_id, MIN(ordinal) AS ordinal
             FROM orchestration_v2_projection_turn_items
             WHERE thread_id = ${threadId} AND type IN ('user_message', 'assistant_message')
+              ${loadedMessageIds === undefined ? sql`` : sql`AND json_extract(payload_json, '$.messageId') IN (SELECT value FROM json_each(${encodeIdList(loadedMessageIds)}))`}
             GROUP BY json_extract(payload_json, '$.messageId')
           `;
           for (const row of rows) messageOrdinals.set(row.message_id, row.ordinal);