fix(chat): pin existing-session sends to captured target (#2424)

* fix(chat): pin sends to captured session

* fix(chat): handle runtime cancellation consistently

packages/ui/src/sync/session-ui-store.ts

@@ -122,6 +122,7 @@ export function expandSlashCommandGoalObjective(content: string, commands: GoalC
 // ---------------------------------------------------------------------------
 
 export function routeMessage(params: {
+  runtimeKey?: string
   sessionId: string
   directory?: string | null
   content: string
@@ -138,6 +139,7 @@ export function routeMessage(params: {
   const requestDirectory = params.directory ?? undefined
   if (params.inputMode === "shell") {
     return opencodeClient.shellSession({
+      runtimeKey: params.runtimeKey,
       sessionId: params.sessionId,
       directory: requestDirectory,
       agent: params.agent ?? "",
@@ -166,6 +168,7 @@ export function routeMessage(params: {
 
     if (isCommand) {
       return optimisticSend({
+        runtimeKey: params.runtimeKey,
         sessionId: params.sessionId,
         content: params.content,
         providerID: params.providerID,
@@ -174,6 +177,7 @@ export function routeMessage(params: {
         directory: requestDirectory,
         files: params.files,
         send: (messageID) => opencodeClient.sendCommand({
+          runtimeKey: params.runtimeKey,
           id: params.sessionId,
           providerID: params.providerID,
           modelID: params.modelID,
@@ -191,6 +195,7 @@ export function routeMessage(params: {
 
   // Normal prompt — optimistic insert so message appears instantly
   return optimisticSend({
+    runtimeKey: params.runtimeKey,
     sessionId: params.sessionId,
     content: params.content,
     providerID: params.providerID,
@@ -199,6 +204,7 @@ export function routeMessage(params: {
     directory: requestDirectory,
     files: params.files,
     send: (messageID) => opencodeClient.sendMessage({
+      runtimeKey: params.runtimeKey,
       id: params.sessionId,
       providerID: params.providerID,
       modelID: params.modelID,
@@ -215,7 +221,14 @@ export function routeMessage(params: {
   })
 }
 
+type CapturedSendTarget = {
+  runtimeKey: string
+  sessionId: string
+  directory: string
+}
+
 type SendMessageOptions = {
+  target?: CapturedSendTarget
   sessionId?: string
   directory?: string
   delivery?: 'steer'
@@ -1198,8 +1211,13 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
     inputMode?: "normal" | "shell",
     options?: SendMessageOptions,
   ) => {
+    const capturedTarget = options?.target
+    if (capturedTarget && capturedTarget.runtimeKey !== getRuntimeKey()) {
+      throw new Error("Message was not sent because the runtime changed.")
+    }
+
     // Clear non-Git changed-files bar on new user message for current session
-    const sid = options?.sessionId ?? get().currentSessionId;
+    const sid = capturedTarget?.sessionId ?? options?.sessionId ?? get().currentSessionId;
     if (sid) {
       const map = new Map(get().pendingChangesBarDismissed);
       map.delete(sid);
@@ -1258,7 +1276,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
     }
 
     // ---- New session from draft ----
-    if (!options?.sessionId && draft?.open) {
+    if (!capturedTarget && !options?.sessionId && draft?.open) {
       const createdDraftSession = await materializeOpenDraftSession({
         providerID,
         modelID,
@@ -1310,7 +1328,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
     }
 
     // ---- Existing session ----
-    const targetSessionId = options?.sessionId ?? get().currentSessionId
+    const targetSessionId = capturedTarget?.sessionId ?? options?.sessionId ?? get().currentSessionId
     const sessionAgentSelection = targetSessionId
       ? useSelectionStore.getState().getSessionAgentSelection(targetSessionId)
       : null
@@ -1345,7 +1363,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
     }
 
     const currentSessionDirectory = targetSessionId
-      ? normalizePath(options?.directory ?? get().getDirectoryForSession(targetSessionId))
+      ? normalizePath(capturedTarget?.directory ?? options?.directory ?? get().getDirectoryForSession(targetSessionId))
       : null
     if (targetSessionId) {
       notifyMessageSent(targetSessionId)
@@ -1366,6 +1384,7 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
       await applyArmedGoal(targetSessionId, currentSessionDirectory)
     }
     await routeMessage({
+      runtimeKey: capturedTarget?.runtimeKey,
       sessionId: targetSessionId || "",
       directory: currentSessionDirectory,
       content,