fix(chat): stop prefix dedupe merging distinct messages (#1335) (#1340)

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatTranscriptMerge.kt

@@ -201,6 +201,9 @@ internal class TranscriptComparison(
         ) {
             return true
         }
+        // #842 / #1335: prefix drift only exists for sealed assistant narration; two REST
+        // rows already returned above, so user rows must never collapse by prefix.
+        if (a.role != MessageRole.ASSISTANT) return false
         return ta.length >= 40 && tb.length >= 40 && (tb.startsWith(ta) || ta.startsWith(tb))
     }
 }

app/src/test/java/com/m57/hermescontrol/ui/chat/ChatPrefixDedupeTest.kt

@@ -0,0 +1,162 @@
+package com.m57.hermescontrol.ui.chat
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * Issue #1335: prefix dedupe must not merge distinct messages.
+ */
+class ChatPrefixDedupeTest {
+    // ── Contract 1 ────────────────────────────────────────────────────────────
+    // Two USER messages, both >=40 chars, one a strict prefix of the other,
+    // different ids -> NOT the same logical message (both survive a merge).
+
+    @Test
+    fun contract1_userMessages_strictPrefixDistinctIds_notSameLogicalMessage() {
+        val prefixText = "Please write a comprehensive test suite for issue thirteen thirty five."
+        val fullText = "$prefixText It should cover all edge cases thoroughly."
+        val msg1 = ChatMessage(id = "user-msg-1", role = MessageRole.USER, content = prefixText)
+        val msg2 = ChatMessage(id = "user-msg-2", role = MessageRole.USER, content = fullText)
+
+        assertFalse(sameLogicalMessage(msg1, msg2))
+        assertFalse(sameLogicalMessage(msg2, msg1))
+
+        val merged = mergeTranscriptWithLive(listOf(msg2), listOf(msg1), preserveLiveIds = true)
+        assertEquals(2, merged.size)
+        assertTrue(merged.any { it.id == "user-msg-1" && it.content == prefixText })
+        assertTrue(merged.any { it.id == "user-msg-2" && it.content == fullText })
+    }
+
+    // ── Contract 2 ────────────────────────────────────────────────────────────
+    // Two ASSISTANT messages that are both canonical REST rows (distinct restIds /
+    // canonical ids), one a >=40-char prefix of the other -> NOT same.
+
+    @Test
+    fun contract2_assistantCanonicalRestRows_strictPrefix_notSameLogicalMessage() {
+        val prefixText = "I have inspected the project repository and verified the build files."
+        val fullText = "$prefixText Now proceeding with the implementation of the requested tests."
+        val restRow1 =
+            ChatMessage(
+                id = "rest-s-101",
+                role = MessageRole.ASSISTANT,
+                content = prefixText,
+                restId = "rest-s-101",
+            )
+        val restRow2 =
+            ChatMessage(
+                id = "rest-s-102",
+                role = MessageRole.ASSISTANT,
+                content = fullText,
+                restId = "rest-s-102",
+            )
+
+        assertFalse(sameLogicalMessage(restRow1, restRow2))
+        assertFalse(sameLogicalMessage(restRow2, restRow1))
+
+        val merged = mergeTranscriptWithLive(listOf(restRow2), listOf(restRow1), preserveLiveIds = true)
+        assertEquals(2, merged.size)
+    }
+
+    // ── Contract 3 ────────────────────────────────────────────────────────────
+    // TOOL rows never match by content prefix.
+
+    @Test
+    fun contract3_toolRows_neverMatchByContentPrefix() {
+        val prefixToolContent = """{"output":"build succeeded without any compiler errors or warnings during check"}"""
+        val fullToolContent =
+            """{"output":"build succeeded without any compiler errors or warnings during check and all tests pass"}"""
+        val tool1 =
+            ChatMessage(
+                id = "tool-1",
+                role = MessageRole.TOOL,
+                content = prefixToolContent,
+                toolName = "terminal",
+                toolCallId = "call-1",
+            )
+        val tool2 =
+            ChatMessage(
+                id = "tool-2",
+                role = MessageRole.TOOL,
+                content = fullToolContent,
+                toolName = "terminal",
+                toolCallId = "call-2",
+            )
+
+        assertFalse(sameLogicalMessage(tool1, tool2))
+        assertFalse(sameLogicalMessage(tool2, tool1))
+    }
+
+    // ── Contract 4 ────────────────────────────────────────────────────────────
+    // Exact-equal trimmed content still matches as before for a live vs REST pair
+    // of the same role (sanity).
+
+    @Test
+    fun contract4_exactEqualTrimmedContent_liveVsRest_matchesSameLogicalMessage() {
+        for (role in listOf(MessageRole.USER, MessageRole.ASSISTANT)) {
+            val live =
+                ChatMessage(
+                    id = "live-temp-id",
+                    role = role,
+                    content = "\n\nHello, this is an important message for testing.\n  ",
+                )
+            val rest =
+                ChatMessage(
+                    id = "rest-s-200",
+                    role = role,
+                    content = "Hello, this is an important message for testing.",
+                    restId = "rest-s-200",
+                )
+
+            assertTrue("Role $role exact-equal trimmed content must match", sameLogicalMessage(live, rest))
+            assertTrue(
+                "Role $role exact-equal trimmed content must match symmetrically",
+                sameLogicalMessage(rest, live),
+            )
+
+            val merged = mergeTranscriptWithLive(listOf(rest), listOf(live), preserveLiveIds = true)
+            assertEquals("Exact-equal trimmed pair should deduplicate into single message", 1, merged.size)
+        }
+    }
+
+    // ── Contract 5 ────────────────────────────────────────────────────────────
+    // Issue #842 scenario still dedupes: a live sealed interim assistant narration
+    // without completion/REST identity whose text (after trim) is a prefix of /
+    // equal-prefix to the persisted REST narration -> treated as same (reuse the
+    // shape used in ChatHistoryCommentaryTest if it exists).
+
+    @Test
+    fun contract5_issue842_liveSealedInterimAssistantNarration_prefixOfRestNarration_stillDedupes() {
+        // Issue #842 / ChatToolDedupeTest pattern:
+        // Live sealed interim bubble without REST identity raced flush and ends prematurely.
+        // Rest row contains the full/completed narration.
+        val liveOrphan =
+            ChatMessage(
+                id = "live-orphan-sealed",
+                role = MessageRole.ASSISTANT,
+                content =
+                    "\n\ntool's loaded! 🔍 now searchin' for the **best hummus recipe**" +
+                        " — gimme dat creamy dreamy chickpea",
+            )
+        val restRow =
+            ChatMessage(
+                id = "rest-s-842",
+                role = MessageRole.ASSISTANT,
+                content =
+                    "tool's loaded! 🔍 now searchin' for the **best hummus recipe**" +
+                        " — gimme dat creamy dreamy chickpea goodness:",
+                restId = "rest-s-842",
+            )
+
+        assertTrue(sameLogicalMessage(liveOrphan, restRow))
+        assertTrue(sameLogicalMessage(restRow, liveOrphan))
+
+        val merged = mergeTranscriptWithLive(listOf(restRow), listOf(liveOrphan), preserveLiveIds = true)
+        assertEquals(
+            "Live interim orphan should deduplicate against persisted REST narration",
+            1,
+            merged.size,
+        )
+    }
+}