From 2a49c25e1b1b2491e5afbd5891989e2ccb1c05de Mon Sep 17 00:00:00 2001
From: AskaEth <i@yeij.top>
Date: Sun, 4 Oct 2026 14:05:38 +0800
Subject: [PATCH] =?UTF-8?q?fix(chat):=20WS=20history=20=E5=B8=A7=E6=8C=89?=
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WS 首帧 history 是**主会话**最近 50 条的回放，但连接是全局的、帧会被投给任意
ChatViewModel；onEvent 此前把它**原样**并进当前消息列表，导致进次级会话会看到
主会话的消息混在一起——是数据串台，不是显示问题。

- data/repository/PagedMessages.kt：新增纯函数 historyForSession(messages, sessionId)，
  按**消息自身的 sessionId** 过滤；sessionId 为空的帧视为「无法判定」放行，
  不因缺一个字段就整段丢掉历史（保持既有行为）
- ui/chat/ChatViewModel.kt：history 分支先收敛到本会话再合并

为什么按 sessionId 而不是「只有主会话才收 history」：前者更耐将来——
服务端哪天开始给次级会话回放，这里无需改动。

测试：178 全绿（175 → +3），新增三条：主会话回放不得泄漏进次级会话、
缺 sessionId 的帧放行、过滤不修改入参。
---
 .../cyrene/data/repository/PagedMessages.kt   | 18 ++++++++++
 .../top/yeij/cyrene/ui/chat/ChatViewModel.kt  |  5 ++-
 .../data/repository/MessageMergeTest.kt       | 34 +++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/app/src/main/kotlin/top/yeij/cyrene/data/repository/PagedMessages.kt b/app/src/main/kotlin/top/yeij/cyrene/data/repository/PagedMessages.kt
index 013b2ae..40ea402 100644
--- a/app/src/main/kotlin/top/yeij/cyrene/data/repository/PagedMessages.kt
+++ b/app/src/main/kotlin/top/yeij/cyrene/data/repository/PagedMessages.kt
@@ -38,3 +38,21 @@ fun mergeMessages(
     incoming.forEach { byId[it.id] = it }
     return byId.values.sortedWith(MessageOrder)
 }
+
+/**
+ * 把一帧 `history` 收敛到**本会话**。
+ *
+ * WS 首帧 `history` 是**主会话**最近 50 条的回放，但连接是全局的、帧会被投给任意
+ * `ChatViewModel`——不过滤就会把主会话的消息混进次级会话。
+ *
+ * 判定以**消息自身的 `sessionId`** 为准，而不是「只有主会话才收 history」：前者更耐将来，
+ * 服务端哪天开始给次级会话回放，这里无需改动。
+ *
+ * `sessionId` 为空的帧视为「无法判定」**放行**——不因缺一个字段就整段丢掉历史（保持既有行为）。
+ *
+ * 纯函数，不修改入参。
+ */
+fun historyForSession(
+    messages: List<HistoryMessageDto>,
+    sessionId: String,
+): List<HistoryMessageDto> = messages.filter { it.sessionId.isBlank() || it.sessionId == sessionId }
diff --git a/app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatViewModel.kt b/app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatViewModel.kt
index 6d5da62..6ff0419 100644
--- a/app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatViewModel.kt
+++ b/app/src/main/kotlin/top/yeij/cyrene/ui/chat/ChatViewModel.kt
@@ -11,6 +11,7 @@ import top.yeij.cyrene.app.AppContainer
 import top.yeij.cyrene.data.api.CyreneException
 import top.yeij.cyrene.data.api.dto.HistoryMessageDto
 import top.yeij.cyrene.data.repository.MessageRepository
+import top.yeij.cyrene.data.repository.historyForSession
 import top.yeij.cyrene.data.repository.mergeMessages
 import top.yeij.cyrene.data.ws.ChatSocket
 import top.yeij.cyrene.data.ws.WsEvent
@@ -173,7 +174,9 @@ class ChatViewModel(
     private fun onEvent(event: WsEvent) {
         when (event) {
             is WsEvent.History -> {
-                val incoming = event.messages
+                // 这一帧是**主会话**的回放，却会被投给任意 ChatViewModel——必须先收敛到本会话，
+                // 否则进次级会话会看到主会话的消息混进来。
+                val incoming = historyForSession(event.messages, sessionId)
                 if (incoming.isEmpty()) {
                     _state.update { it.copy(loading = false) }
                 } else {
diff --git a/app/src/test/kotlin/top/yeij/cyrene/data/repository/MessageMergeTest.kt b/app/src/test/kotlin/top/yeij/cyrene/data/repository/MessageMergeTest.kt
index c8ca355..17d7f39 100644
--- a/app/src/test/kotlin/top/yeij/cyrene/data/repository/MessageMergeTest.kt
+++ b/app/src/test/kotlin/top/yeij/cyrene/data/repository/MessageMergeTest.kt
@@ -85,4 +85,38 @@ class MessageMergeTest {
         assertEquals(listOf("m2", "m1"), idsOf(existing))
         assertEquals(listOf("m3"), idsOf(incoming))
     }
+
+    private fun msgIn(sessionId: String, id: String) = HistoryMessageDto(
+        id = id,
+        sessionId = sessionId,
+        role = "user",
+        content = id,
+        createdAt = 0L,
+    )
+
+    @Test
+    fun `the main session's history replay cannot leak into a sub session`() {
+        // 真实缺陷：WS 首帧 history 是主会话的回放，却会被并进每一个 ChatViewModel。
+        val replay = listOf(msgIn("web", "m1"), msgIn("web:abc", "m2"))
+
+        assertEquals(listOf("m2"), idsOf(historyForSession(replay, "web:abc")))
+        assertEquals(listOf("m1"), idsOf(historyForSession(replay, "web")))
+    }
+
+    @Test
+    fun `a frame without a sessionId is kept rather than dropping history`() {
+        // 缺字段时无法判定归属，放行以保持既有行为——不因缺一个字段整段丢掉历史。
+        val replay = listOf(msgIn("", "m1"))
+
+        assertEquals(listOf("m1"), idsOf(historyForSession(replay, "web:abc")))
+    }
+
+    @Test
+    fun `history filtering does not mutate the input`() {
+        val replay = listOf(msgIn("web", "m1"), msgIn("web:abc", "m2"))
+
+        historyForSession(replay, "web")
+
+        assertEquals(listOf("m1", "m2"), idsOf(replay))
+    }
 }