feat(chat): show agent message reactions (#1422)

app/src/main/java/com/m57/hermescontrol/data/model/MessageReaction.kt

@@ -0,0 +1,33 @@
+package com.m57.hermescontrol.data.model
+
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.JsonPrimitive
+
+/** One emoji reaction on a message. Tapback semantics: at most one per [author] per message. */
+data class MessageReaction(
+    val emoji: String,
+    val author: String,
+)
+
+/** Reactions carried by a live `message.reaction` event payload (`reactions` list of maps). */
+internal fun parseMessageReactions(raw: Any?): List<MessageReaction> =
+    (raw as? List<*>).orEmpty().mapNotNull { item ->
+        val map = item as? Map<*, *> ?: return@mapNotNull null
+        val emoji = (map["emoji"] as? String)?.takeIf { it.isNotBlank() } ?: return@mapNotNull null
+        MessageReaction(emoji = emoji, author = map["author"] as? String ?: "")
+    }
+
+/** Reactions persisted under `display_metadata.reactions` on a REST transcript row. */
+internal fun parseMessageReactions(displayMetadata: JsonElement?): List<MessageReaction> {
+    val list = (displayMetadata as? JsonObject)?.get("reactions") as? JsonArray ?: return emptyList()
+    return list.mapNotNull { item ->
+        val obj = item as? JsonObject ?: return@mapNotNull null
+        val emoji =
+            (obj["emoji"] as? JsonPrimitive)?.takeIf { it.isString }?.content?.takeIf { it.isNotBlank() }
+                ?: return@mapNotNull null
+        val author = (obj["author"] as? JsonPrimitive)?.takeIf { it.isString }?.content.orEmpty()
+        MessageReaction(emoji = emoji, author = author)
+    }
+}

app/src/main/java/com/m57/hermescontrol/data/model/SessionMessagesResponse.kt

@@ -75,6 +75,10 @@ data class SessionMessage(
     val timestampText: String?
         get() = (timestamp as? JsonPrimitive)?.content
 
+    /** Emoji reactions persisted on this row (`display_metadata.reactions`). */
+    val reactions: List<MessageReaction>
+        get() = parseMessageReactions(display_metadata)
+
     val tokenCount: Int?
         get() {
             val prim = token_count as? JsonPrimitive ?: return null

app/src/main/java/com/m57/hermescontrol/data/ws/EventParser.kt

@@ -1,6 +1,7 @@
 package com.m57.hermescontrol.data.ws
 
 import android.util.Log
+import com.m57.hermescontrol.data.model.parseMessageReactions
 import com.m57.hermescontrol.ui.chat.extractTodosFromMap
 import kotlinx.serialization.json.JsonObject
 
@@ -333,6 +334,20 @@ object EventParser {
                 WsEvent.ReactionEvent(kind)
             }
 
+            "message.reaction" -> {
+                val rowId = (payload?.get("row_id") as? Number)?.toLong()
+                if (rowId == null) {
+                    WsEvent.Unknown(rawJson)
+                } else {
+                    WsEvent.MessageReactionUpdated(
+                        rowId = rowId,
+                        reactions = parseMessageReactions(payload["reactions"]),
+                        role = payload["role"] as? String ?: "",
+                        sessionId = sessionId,
+                    )
+                }
+            }
+
             "approval.request" -> {
                 val command = payload?.get("command") as? String
                 val description = payload?.get("description") as? String

app/src/main/java/com/m57/hermescontrol/data/ws/WsEvent.kt

@@ -445,6 +445,18 @@ sealed class WsEvent {
         val kind: String = "",
     ) : WsEvent()
 
+    /**
+     * `message.reaction`: the agent (or another client) set/cleared a tapback on a stored
+     * message. [reactions] is the row's full list after the write; [rowId] is the gateway
+     * SQLite row id, matched against `ChatMessage.serverRowId`.
+     */
+    data class MessageReactionUpdated(
+        val rowId: Long,
+        val reactions: List<com.m57.hermescontrol.data.model.MessageReaction>,
+        val role: String,
+        val sessionId: String?,
+    ) : WsEvent()
+
     // ── Replay resync (internal) ──────────────────────────────────────────
 
     /** Internal: replay could not cover the reconnect gap (truncated or epoch change) — UI must refetch history. */

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

@@ -1,6 +1,7 @@
 package com.m57.hermescontrol.ui.chat
 
 import com.m57.hermescontrol.data.model.Attachment
+import com.m57.hermescontrol.data.model.MessageReaction
 import java.util.UUID
 
 /**
@@ -113,6 +114,8 @@ data class ChatMessage(
      * Scoped to the owning profile store; transient.
      */
     val serverRowId: Long? = null,
+    /** Emoji tapbacks on this message (REST `display_metadata` or live `message.reaction`); transient. */
+    val reactions: List<MessageReaction> = emptyList(),
 )
 
 /** Cached REST rows already carry their canonical identity in the persisted primary key. */

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

@@ -274,6 +274,7 @@ internal fun mapServerMessages(
                 tokenCount = tokenCount,
                 completionId = completionId,
                 serverRowId = msg.id?.toLong()?.takeIf { it > 0L },
+                reactions = msg.reactions,
             ),
         )
     }

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

@@ -349,6 +349,7 @@ internal fun dedupeCachedMessages(
             message.copy(
                 restId = it.canonicalRestId,
                 serverRowId = message.serverRowId ?: it.serverRowId,
+                reactions = it.reactions.ifEmpty { message.reactions },
                 completionId = message.completionId ?: it.completionId,
                 displayKind = message.displayKind ?: it.displayKind,
                 isRestoredUnconfirmed = false,
@@ -419,6 +420,7 @@ internal fun mergeCachedTranscriptPage(
                         content = preservedContent ?: rich.content,
                         restId = match.canonicalRestId ?: message.canonicalRestId,
                         serverRowId = match.serverRowId ?: message.serverRowId,
+                        reactions = message.reactions.ifEmpty { match.reactions },
                         completionId = match.completionId ?: message.completionId,
                         displayKind = match.displayKind ?: message.displayKind,
                         isRestoredUnconfirmed =
@@ -457,6 +459,7 @@ internal fun mergeTranscriptWithLive(
                     match.copy(
                         restId = (message.canonicalRestId ?: match.canonicalRestId).takeUnless { it == match.id },
                         serverRowId = message.serverRowId ?: match.serverRowId,
+                        reactions = message.reactions.ifEmpty { match.reactions },
                         displayKind = message.displayKind ?: match.displayKind,
                         isHistoricalCache = false,
                         isRestoredUnconfirmed = false,
@@ -476,6 +479,7 @@ internal fun mergeTranscriptWithLive(
                     match.copy(
                         restId = message.canonicalRestId ?: match.canonicalRestId,
                         serverRowId = message.serverRowId ?: match.serverRowId,
+                        reactions = message.reactions.ifEmpty { match.reactions },
                         content = mergedContent,
                         timestamp = message.timestamp,
                         isStreaming = message.isStreaming,

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

@@ -129,6 +129,7 @@ object ChatWsEventReducer {
                 is WsEvent.BtwComplete -> event.sessionId
                 is WsEvent.SessionUsage -> event.sessionId
                 is WsEvent.TranscriptResyncRequired -> event.sessionId
+                is WsEvent.MessageReactionUpdated -> event.sessionId
                 is WsEvent.VaultUnlockRequest -> event.sessionId
                 is WsEvent.VaultUnlockExpire -> event.sessionId
                 is WsEvent.VaultSaveLoginRequest -> event.sessionId
@@ -252,6 +253,8 @@ object ChatWsEventReducer {
             // ReactionEvent is handled by the ViewModel — purely cosmetic animation
             is WsEvent.ReactionEvent -> ReducerResult(state = state, streamingState = streamingState)
 
+            is WsEvent.MessageReactionUpdated -> onMessageReaction(state, streamingState, event)
+
             // Change events (issue #784) are consumed by their screens' ViewModels
             is WsEvent.ChangeEvent -> ReducerResult(state = state, streamingState = streamingState)
 
@@ -1079,6 +1082,22 @@ object ChatWsEventReducer {
         }
     }
 
+    /** Paints a live tapback on the row whose gateway id matches; unmatched rows arrive with the next REST load. */
+    private fun onMessageReaction(
+        state: ChatUiState,
+        streamingState: StreamingState,
+        event: WsEvent.MessageReactionUpdated,
+    ): ReducerResult {
+        if (state.messages.none { it.serverRowId == event.rowId }) {
+            return ReducerResult(state = state, streamingState = streamingState)
+        }
+        val messages =
+            state.messages.map {
+                if (it.serverRowId == event.rowId) it.copy(reactions = event.reactions) else it
+            }
+        return ReducerResult(state = state.copy(messages = messages), streamingState = streamingState)
+    }
+
     private fun onUnknown(
         state: ChatUiState,
         streamingState: StreamingState,

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

@@ -0,0 +1,44 @@
+package com.m57.hermescontrol.ui.chat.components
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.unit.dp
+import com.m57.hermescontrol.data.model.MessageReaction
+
+/**
+ * Tapback chips shown under a message. One reaction per author, so a short row is enough;
+ * renders nothing when [reactions] is empty.
+ */
+@Composable
+fun MessageReactionChips(
+    reactions: List<MessageReaction>,
+    modifier: Modifier = Modifier,
+) {
+    if (reactions.isEmpty()) return
+    Row(
+        modifier = modifier.testTag("message_reactions"),
+        horizontalArrangement = Arrangement.spacedBy(4.dp),
+    ) {
+        reactions.forEach { reaction ->
+            Surface(
+                shape = CircleShape,
+                color = MaterialTheme.colorScheme.surfaceContainerHigh,
+                tonalElevation = 0.dp,
+            ) {
+                Text(
+                    text = reaction.emoji,
+                    style = MaterialTheme.typography.bodySmall,
+                    modifier = Modifier.padding(horizontal = 6.dp, vertical = 2.dp),
+                )
+            }
+        }
+    }
+}

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

@@ -41,6 +41,7 @@ import com.m57.hermescontrol.ui.chat.InlineAttachment
 import com.m57.hermescontrol.ui.chat.MarkdownText
 import com.m57.hermescontrol.ui.chat.MessageSegment
 import com.m57.hermescontrol.ui.chat.TokenEstimator
+import com.m57.hermescontrol.ui.chat.components.MessageReactionChips
 import com.m57.hermescontrol.ui.chat.components.ReasoningCard
 import com.m57.hermescontrol.ui.chat.components.rememberCopyFeedback
 import com.m57.hermescontrol.ui.chat.splitByMedia
@@ -143,6 +144,10 @@ internal fun FullBleedAgentMessage(
             }
         }
 
+        if (!message.isStreaming) {
+            MessageReactionChips(message.reactions, Modifier.padding(top = 2.dp))
+        }
+
         if (!message.isStreaming && message.content.isNotBlank()) {
             val showTokenStat =
                 messageStatsEnabled && showAssistantMessageTokens &&

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

@@ -41,6 +41,7 @@ import com.m57.hermescontrol.ui.chat.UserBubble
 import com.m57.hermescontrol.ui.chat.components.ChatHistoryPrefetch
 import com.m57.hermescontrol.ui.chat.components.ChatScrollController
 import com.m57.hermescontrol.ui.chat.components.ClarifyBubble
+import com.m57.hermescontrol.ui.chat.components.MessageReactionChips
 import com.m57.hermescontrol.ui.chat.components.ReasoningCard
 import com.m57.hermescontrol.ui.chat.components.VaultCodeCard
 import com.m57.hermescontrol.ui.chat.components.VaultSaveLoginCard
@@ -311,6 +312,15 @@ fun FullBleedChatList(
                                             messageStatsEnabled = messageStatsEnabled,
                                             showUserMessageTokens = showUserMessageTokens,
                                         )
+                                        if (userMessage.reactions.isNotEmpty()) {
+                                            MessageReactionChips(
+                                                reactions = userMessage.reactions,
+                                                modifier =
+                                                    Modifier
+                                                        .align(Alignment.End)
+                                                        .padding(horizontal = 12.dp),
+                                            )
+                                        }
                                     }
                                 }
                             }

app/src/test/java/com/m57/hermescontrol/data/ws/EventParserTest.kt

@@ -1,5 +1,6 @@
 package com.m57.hermescontrol.data.ws
 
+import com.m57.hermescontrol.data.model.MessageReaction
 import io.mockk.every
 import io.mockk.mockkStatic
 import io.mockk.unmockkAll
@@ -928,6 +929,52 @@ class EventParserTest {
         )
     }
 
+    @Test
+    fun testParseMessageReaction_returnsMessageReactionUpdated() {
+        val response =
+            createJsonRpcResponse(
+                jsonrpc = "2.0",
+                id = null,
+                result = null,
+                error = null,
+                method = "event",
+                params =
+                    mapOf(
+                        "type" to "message.reaction",
+                        "session_id" to "s1",
+                        "payload" to
+                            mapOf(
+                                "row_id" to 42,
+                                "role" to "user",
+                                "reactions" to
+                                    listOf(
+                                        mapOf("emoji" to "\uD83D\uDE02", "author" to "agent", "at" to 1.0),
+                                        mapOf("emoji" to "", "author" to "user"),
+                                    ),
+                            ),
+                    ),
+            )
+        val event = EventParser.parse(response, "") as WsEvent.MessageReactionUpdated
+        assertEquals(42L, event.rowId)
+        assertEquals("user", event.role)
+        assertEquals("s1", event.sessionId)
+        assertEquals(listOf(MessageReaction("\uD83D\uDE02", "agent")), event.reactions)
+    }
+
+    @Test
+    fun testParseMessageReaction_withoutRowId_isUnknown() {
+        val response =
+            createJsonRpcResponse(
+                jsonrpc = "2.0",
+                id = null,
+                result = null,
+                error = null,
+                method = "event",
+                params = mapOf("type" to "message.reaction", "payload" to mapOf("reactions" to emptyList<Any>())),
+            )
+        assertTrue(EventParser.parse(response, "") is WsEvent.Unknown)
+    }
+
     @Test
     fun testParseUnknownType_returnsUnknownEvent() {
         val response =

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

@@ -1,8 +1,12 @@
 package com.m57.hermescontrol.ui.chat
 
+import com.m57.hermescontrol.data.model.MessageReaction
 import com.m57.hermescontrol.data.model.SessionMessage
 import com.m57.hermescontrol.notification.ReplyNotificationTarget
 import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.buildJsonArray
+import kotlinx.serialization.json.buildJsonObject
+import kotlinx.serialization.json.put
 import org.junit.Assert.assertEquals
 import org.junit.Assert.assertNull
 import org.junit.Test
@@ -59,4 +63,35 @@ class ChatServerMessageMapperPurityTest {
 
         assertEquals(42L, mapped.single().timestamp)
     }
+
+    @Test
+    fun persistedReactionsHydrateFromDisplayMetadata() {
+        val row =
+            SessionMessage(
+                id = 5,
+                role = "user",
+                content = JsonPrimitive("hello"),
+                display_metadata =
+                    buildJsonObject {
+                        put(
+                            "reactions",
+                            buildJsonArray {
+                                add(
+                                    buildJsonObject {
+                                        put("emoji", "\uD83D\uDE02")
+                                        put("author", "agent")
+                                    },
+                                )
+                                add(buildJsonObject { put("author", "user") })
+                            },
+                        )
+                    },
+            )
+        val mapped = mapServerMessages("s", listOf(row), 0, true, emptyList()).single()
+        assertEquals(listOf(MessageReaction("\uD83D\uDE02", "agent")), mapped.reactions)
+        assertEquals(
+            emptyList<MessageReaction>(),
+            mapServerMessages("s", listOf(assistant(6, "x")), 0, true, emptyList()).single().reactions,
+        )
+    }
 }

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

@@ -1,5 +1,6 @@
 package com.m57.hermescontrol.ui.chat
 
+import com.m57.hermescontrol.data.model.MessageReaction
 import com.m57.hermescontrol.data.model.UsageSnapshotResponse
 import com.m57.hermescontrol.data.ws.WsEvent
 import org.junit.Assert.assertEquals
@@ -1642,4 +1643,60 @@ class ChatWsEventReducerTest {
         assertEquals("idle", result.state.compressionStatus)
         assertEquals(initialMessages, result.state.messages)
     }
+
+    @Test
+    fun messageReactionPaintsOnlyTheRowWithTheMatchingServerId() {
+        val target = ChatMessage(id = "a", role = MessageRole.USER, content = "hi", serverRowId = 7L)
+        val other = ChatMessage(id = "b", role = MessageRole.ASSISTANT, content = "yo", serverRowId = 8L)
+        val state = ChatUiState(currentSessionId = "s", messages = listOf(target, other))
+        val reactions = listOf(MessageReaction("\u2764\uFE0F", "agent"))
+        val result =
+            ChatWsEventReducer.reduce(
+                state,
+                StreamingState(),
+                WsEvent.MessageReactionUpdated(7L, reactions, "user", "s"),
+                "s",
+            )
+        assertEquals(reactions, result.state.messages[0].reactions)
+        assertTrue(
+            result.state.messages[1]
+                .reactions
+                .isEmpty(),
+        )
+        val retracted =
+            ChatWsEventReducer.reduce(
+                result.state,
+                result.streamingState,
+                WsEvent.MessageReactionUpdated(7L, emptyList(), "user", "s"),
+                "s",
+            )
+        assertTrue(
+            retracted.state.messages[0]
+                .reactions
+                .isEmpty(),
+        )
+    }
+
+    @Test
+    fun messageReactionForUnknownRowOrOtherSessionIsIgnored() {
+        val msg = ChatMessage(id = "a", role = MessageRole.USER, content = "hi", serverRowId = 7L)
+        val state = ChatUiState(currentSessionId = "s", messages = listOf(msg))
+        val reactions = listOf(MessageReaction("\uD83D\uDC4D", "agent"))
+        val unknownRow =
+            ChatWsEventReducer.reduce(
+                state,
+                StreamingState(),
+                WsEvent.MessageReactionUpdated(99L, reactions, "user", "s"),
+                "s",
+            )
+        assertEquals(state, unknownRow.state)
+        val otherSession =
+            ChatWsEventReducer.reduce(
+                state,
+                StreamingState(),
+                WsEvent.MessageReactionUpdated(7L, reactions, "user", "zzz"),
+                "s",
+            )
+        assertEquals(state, otherSession.state)
+    }
 }