From 65e288bb712e9221d28c2a10f2e97a80deb7b0eb Mon Sep 17 00:00:00 2001
From: Isaac Sanchez-Hawkins <266845420+isanchez404@users.noreply.github.com>
Date: Tue, 19 May 2026 10:39:37 -0400
Subject: [PATCH] fix: respect session prefetch page size (#1332)

Co-authored-by: Isaac Sanchez <isanchez-hawkins@arize.com>
---
 .../__tests__/session-prefetch-cache.test.ts  | 23 +++++++++++++++++++
 .../ui/src/sync/session-prefetch-cache.ts     |  1 +
 2 files changed, 24 insertions(+)
 create mode 100644 packages/ui/src/sync/__tests__/session-prefetch-cache.test.ts

diff --git a/packages/ui/src/sync/__tests__/session-prefetch-cache.test.ts b/packages/ui/src/sync/__tests__/session-prefetch-cache.test.ts
new file mode 100644
index 00000000..225d1d4a
--- /dev/null
+++ b/packages/ui/src/sync/__tests__/session-prefetch-cache.test.ts
@@ -0,0 +1,23 @@
+import { describe, expect, test } from "bun:test"
+
+import { shouldSkipSessionPrefetch } from "../session-prefetch-cache"
+
+describe("shouldSkipSessionPrefetch", () => {
+  test("does not skip a larger fetch when only a smaller partial prefetch is cached", () => {
+    expect(shouldSkipSessionPrefetch({
+      hasMessages: true,
+      info: { limit: 50, complete: false, at: 1_000 },
+      pageSize: 200,
+      now: 1_001,
+    })).toBe(false)
+  })
+
+  test("still skips a recent partial prefetch when cached coverage matches the request", () => {
+    expect(shouldSkipSessionPrefetch({
+      hasMessages: true,
+      info: { limit: 200, complete: false, at: 1_000 },
+      pageSize: 200,
+      now: 1_001,
+    })).toBe(true)
+  })
+})
diff --git a/packages/ui/src/sync/session-prefetch-cache.ts b/packages/ui/src/sync/session-prefetch-cache.ts
index 3ec66d86..16e70122 100644
--- a/packages/ui/src/sync/session-prefetch-cache.ts
+++ b/packages/ui/src/sync/session-prefetch-cache.ts
@@ -35,6 +35,7 @@ export function shouldSkipSessionPrefetch(input: {
     if (!input.info) return true
     if (input.info.complete) return true
     if (input.info.limit > input.pageSize) return true
+    if (input.info.limit < input.pageSize) return false
   } else {
     if (!input.info) return false
   }