refactor(session): make message ordering explicit

packages/opencode/src/session/message-v2.ts

@@ -579,9 +579,10 @@ export const cursor = {
   },
 }
 
-const messageOrder = new WeakMap<Info, number>()
+const chronologicalOrder = Symbol("chronologicalOrder")
 const messageRowID = sql<number>`rowid`
 type MessageRow = typeof MessageTable.$inferSelect & { sequence?: number }
+type Chronological = WithParts & { [chronologicalOrder]?: number }
 
 const info = (row: MessageRow) =>
   ({
@@ -1045,7 +1046,7 @@ export function filterCompacted(msgs: Iterable<WithParts>) {
       completed.add(msg.info.parentID)
   }
   result.reverse()
-  result.forEach((msg, index) => messageOrder.set(msg.info, index))
+  result.forEach((msg, index) => ((msg as Chronological)[chronologicalOrder] = index))
   const compactionIndex = result.findLastIndex(
     (msg) =>
       msg.info.role === "user" &&
@@ -1079,10 +1080,10 @@ export const filterCompactedEffect = Effect.fnUntraced(function* (sessionID: Ses
   return filterCompacted(stream(sessionID))
 })
 
-export function compare(a: Info, b: Info, indexA = -1, indexB = -1) {
-  if (a.time.created !== b.time.created) return a.time.created - b.time.created
-  const sequenceA = messageOrder.get(a)
-  const sequenceB = messageOrder.get(b)
+export function compare(a: WithParts, b: WithParts, indexA = -1, indexB = -1) {
+  if (a.info.time.created !== b.info.time.created) return a.info.time.created - b.info.time.created
+  const sequenceA = (a as Chronological)[chronologicalOrder]
+  const sequenceB = (b as Chronological)[chronologicalOrder]
   if (sequenceA !== undefined && sequenceB !== undefined && sequenceA !== sequenceB) return sequenceA - sequenceB
   return indexA - indexB
 }
@@ -1095,33 +1096,41 @@ export function compare(a: Info, b: Info, indexA = -1, indexB = -1) {
 // tasks are compaction/subtask parts attached to user messages newer than the
 // latest finished assistant — i.e. unprocessed work.
 export function latest(msgs: WithParts[]) {
-  let user: User | undefined
-  let assistant: Assistant | undefined
-  let finished: Assistant | undefined
+  let user: WithParts | undefined
+  let assistant: WithParts | undefined
+  let finished: WithParts | undefined
   let userIndex = -1
   let assistantIndex = -1
   let finishedIndex = -1
   for (const [index, msg] of msgs.entries()) {
     const info = msg.info
-    if (info.role === "user" && (!user || compare(info, user, index, userIndex) > 0)) {
-      user = info
+    if (info.role === "user" && (!user || compare(msg, user, index, userIndex) > 0)) {
+      user = msg
       userIndex = index
     }
-    if (info.role === "assistant" && (!assistant || compare(info, assistant, index, assistantIndex) > 0)) {
-      assistant = info
+    if (info.role === "assistant" && (!assistant || compare(msg, assistant, index, assistantIndex) > 0)) {
+      assistant = msg
       assistantIndex = index
     }
-    if (info.role === "assistant" && info.finish && (!finished || compare(info, finished, index, finishedIndex) > 0)) {
-      finished = info
+    if (info.role === "assistant" && info.finish && (!finished || compare(msg, finished, index, finishedIndex) > 0)) {
+      finished = msg
       finishedIndex = index
     }
   }
   const tasks = msgs.flatMap((m, index) =>
-    finished && compare(m.info, finished, index, finishedIndex) <= 0
+    finished && compare(m, finished, index, finishedIndex) <= 0
       ? []
       : m.parts.filter((p): p is CompactionPart | SubtaskPart => p.type === "compaction" || p.type === "subtask"),
   )
-  return { user, assistant, finished, tasks }
+  return {
+    user: user?.info.role === "user" ? user.info : undefined,
+    assistant: assistant?.info.role === "assistant" ? assistant.info : undefined,
+    finished: finished?.info.role === "assistant" ? finished.info : undefined,
+    userMessage: user,
+    assistantMessage: assistant,
+    finishedMessage: finished,
+    tasks,
+  }
 }
 
 export function fromError(

packages/opencode/src/session/prompt.ts

@@ -1250,14 +1250,18 @@ export const layer = Layer.effect(
 
           let msgs = yield* MessageV2.filterCompactedEffect(sessionID)
 
-          const { user: lastUser, assistant: lastAssistant, finished: lastFinished, tasks } = MessageV2.latest(msgs)
-          const before = (a: MessageV2.Info, b: MessageV2.Info) => MessageV2.compare(a, b) < 0
+          const latest = MessageV2.latest(msgs)
+          const { user: lastUser, assistant: lastAssistant, finished: lastFinished, tasks } = latest
 
           if (!lastUser) throw new Error("No user message found in stream. This should never happen.")
 
           const lastAssistantMsg = msgs.findLast(
             (msg) => msg.info.role === "assistant" && msg.info.id === lastAssistant?.id,
           )
+          const userBeforeAssistant =
+            latest.userMessage &&
+            latest.assistantMessage &&
+            MessageV2.compare(latest.userMessage, latest.assistantMessage) < 0
           // Some providers return "stop" even when the assistant message contains tool calls.
           // Keep the loop running so tool results can be sent back to the model.
           // Skip provider-executed tool parts — those were fully handled within the
@@ -1269,7 +1273,7 @@ export const layer = Layer.effect(
             lastAssistant?.finish &&
             !["tool-calls"].includes(lastAssistant.finish) &&
             !hasToolCalls &&
-            before(lastUser, lastAssistant)
+            userBeforeAssistant
           ) {
             yield* slog.info("exiting loop")
             break
@@ -1399,7 +1403,8 @@ export const layer = Layer.effect(
 
             if (step > 1 && lastFinished) {
               for (const m of msgs) {
-                if (m.info.role !== "user" || !before(lastFinished, m.info)) continue
+                const finishedBeforeMessage = latest.finishedMessage && MessageV2.compare(latest.finishedMessage, m) < 0
+                if (m.info.role !== "user" || !finishedBeforeMessage) continue
                 for (const p of m.parts) {
                   if (p.type !== "text" || p.ignored || p.synthetic) continue
                   if (!p.text.trim()) continue