From e50a4846334707a8c1ba4b2f4a41d2f39d602cb8 Mon Sep 17 00:00:00 2001
From: Isaac Sanchez-Hawkins <266845420+isanchez404@users.noreply.github.com>
Date: Tue, 12 May 2026 04:05:37 -0400
Subject: [PATCH] fix(sync): drop orphan session parts (#1183)

* fix(sync): drop orphan session parts

* fix(sync): guard missing part cache

---------

Co-authored-by: Isaac Sanchez <isanchez-hawkins@arize.com>
---
 .../ui/src/sync/__tests__/eviction.test.ts    | 20 +++++++++++++++++--
 packages/ui/src/sync/session-cache.ts         | 11 ++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/packages/ui/src/sync/__tests__/eviction.test.ts b/packages/ui/src/sync/__tests__/eviction.test.ts
index 03a2fad4..22166743 100644
--- a/packages/ui/src/sync/__tests__/eviction.test.ts
+++ b/packages/ui/src/sync/__tests__/eviction.test.ts
@@ -1,11 +1,11 @@
 import { describe, expect, test } from "bun:test"
-import type { Message, PermissionRequest, QuestionRequest } from "@opencode-ai/sdk/v2/client"
+import type { Message, Part, PermissionRequest, QuestionRequest } from "@opencode-ai/sdk/v2/client"
 import {
   canDisposeDirectory,
   hasPendingBlockingRequests,
   pickDirectoriesToEvict,
 } from "../eviction"
-import { getProtectedSessionCacheIds, pickSessionCacheEvictions } from "../session-cache"
+import { dropSessionCaches, getProtectedSessionCacheIds, pickSessionCacheEvictions } from "../session-cache"
 import { INITIAL_STATE, type DirState, type State } from "../types"
 
 const DAY_MS = 24 * 60 * 60 * 1000
@@ -172,4 +172,20 @@ describe("session cache eviction", () => {
     expect(seen.has("ses_question")).toBe(true)
     expect(seen.has("ses_streaming")).toBe(true)
   })
+
+  test("drops parts for evicted messages without part session ids", () => {
+    const store = buildState({
+      message: {
+        ses_old: [{ id: "msg_1", role: "user", time: { created: 1 } } as Message],
+      },
+      part: {
+        msg_1: [{ id: "prt_1", messageID: "msg_1" } as Part],
+      },
+    })
+
+    dropSessionCaches(store, ["ses_old"])
+
+    expect(store.message.ses_old).toBe(undefined)
+    expect(store.part.msg_1).toBe(undefined)
+  })
 })
diff --git a/packages/ui/src/sync/session-cache.ts b/packages/ui/src/sync/session-cache.ts
index 297eb62d..37b89f4b 100644
--- a/packages/ui/src/sync/session-cache.ts
+++ b/packages/ui/src/sync/session-cache.ts
@@ -56,6 +56,17 @@ export function dropSessionCaches(store: SessionCache, sessionIDs: Iterable<stri
   const stale = new Set(Array.from(sessionIDs).filter(Boolean))
   if (stale.size === 0) return
 
+  const staleMessageIDs = new Set<string>()
+  for (const sessionID of stale) {
+    for (const message of store.message?.[sessionID] ?? []) {
+      if (message?.id) staleMessageIDs.add(message.id)
+    }
+  }
+
+  for (const messageID of staleMessageIDs) {
+    if (store.part) delete store.part[messageID]
+  }
+
   for (const key of Object.keys(store.part ?? {})) {
     const parts = store.part[key]
     if (!parts?.some((part) => stale.has((part as { sessionID?: string })?.sessionID ?? "")))