fix: stabilize chat turn projection

packages/ui/src/lib/opencode/client.ts

@@ -27,6 +27,45 @@ import {
 // Can be overridden with VITE_OPENCODE_URL for absolute URLs in special deployments
 const DEFAULT_BASE_URL = import.meta.env.VITE_OPENCODE_URL || "/api";
 const ABSOLUTE_URL_PATTERN = /^[a-zA-Z][a-zA-Z\d+\-.]*:\/\//;
+const ID_RANDOM_CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+const ID_RANDOM_LENGTH = 14;
+
+let lastIdTimestamp = 0;
+let idCounter = 0;
+
+const randomBase62 = (length: number): string => {
+  const bytes = new Uint8Array(length);
+  if (typeof crypto !== "undefined" && typeof crypto.getRandomValues === "function") {
+    crypto.getRandomValues(bytes);
+  } else {
+    for (let index = 0; index < length; index += 1) {
+      bytes[index] = Math.floor(Math.random() * 256);
+    }
+  }
+
+  let result = "";
+  for (let index = 0; index < length; index += 1) {
+    result += ID_RANDOM_CHARS[bytes[index] % ID_RANDOM_CHARS.length];
+  }
+  return result;
+};
+
+const ascendingId = (prefix: "msg"): string => {
+  const timestamp = Date.now();
+  if (timestamp !== lastIdTimestamp) {
+    lastIdTimestamp = timestamp;
+    idCounter = 0;
+  }
+  idCounter += 1;
+
+  const sortable = BigInt(timestamp) * BigInt(0x1000) + BigInt(idCounter);
+  const timeBytes = new Uint8Array(6);
+  for (let index = 0; index < 6; index += 1) {
+    timeBytes[index] = Number((sortable >> BigInt(40 - 8 * index)) & BigInt(0xff));
+  }
+  const hex = Array.from(timeBytes, (byte) => byte.toString(16).padStart(2, "0")).join("");
+  return `${prefix}_${hex}${randomBase62(ID_RANDOM_LENGTH)}`;
+};
 
 const isRetryableFetchError = (error: unknown): boolean => {
   if (error instanceof DOMException && error.name === 'AbortError') return true;
@@ -631,10 +670,9 @@ class OpencodeService {
       retryCount?: number;
     };
   }): Promise<string> {
-    // Generate a temporary client-side ID for optimistic UI
-    // This ID won't be sent to the server - server will generate its own
-    const baseTimestamp = Date.now();
-    const tempMessageId = params.messageId ?? `temp_${baseTimestamp}_${Math.random().toString(36).substring(2, 9)}`;
+    // Reuse one client-side message ID across retries. The server accepts this
+    // as the real user message ID, making ambiguous network retries idempotent.
+    const messageId = params.messageId ?? ascendingId("msg");
 
     // Build parts array using SDK types (TextPartInput | FilePartInput) plus lightweight agent parts
     const parts: Array<TextPartInput | FilePartInput | AgentPartInputLite> = [];
@@ -757,7 +795,7 @@ class OpencodeService {
             },
             agent: params.agent,
             variant: params.variant,
-            ...(params.messageId ? { messageID: params.messageId } : {}),
+            messageID: messageId,
             ...(params.format ? { format: params.format } : {}),
             parts,
           }),
@@ -778,7 +816,7 @@ class OpencodeService {
 
       if (response.ok) {
         recordProviderSuccess(params.providerID);
-        return tempMessageId;
+        return messageId;
       }
 
       if (shouldRetry(params.providerID, response.status, attempt)) {
@@ -817,8 +855,7 @@ class OpencodeService {
     files?: Array<FileInputLite>;
     messageId?: string;
   }): Promise<string> {
-    const baseTimestamp = Date.now();
-    const tempMessageId = params.messageId ?? `temp_${baseTimestamp}_${Math.random().toString(36).substring(2, 9)}`;
+    const tempMessageId = params.messageId ?? ascendingId("msg");
 
     const parts: FilePartInput[] = [];
     if (params.files && params.files.length > 0) {
@@ -840,7 +877,7 @@ class OpencodeService {
       ...(params.agent ? { agent: params.agent } : {}),
       ...(params.variant ? { variant: params.variant } : {}),
       ...(parts.length > 0 ? { parts } : {}),
-      ...(params.messageId ? { messageID: params.messageId } : {}),
+      messageID: tempMessageId,
     };
 
     const response = await fetch(url.toString(), {