fix(copilot): make user-message persistence idempotent on message_id

persistUserMessage appended to copilot_chats.messages unconditionally
(messages || [userMsg]::jsonb) with no check that the id already exists.
A repeated POST for the same userMessageId — network retry, double
submit, React double-effect, or a bypassed/expired send lock (Redis-down
no-op) — therefore tacked on a duplicate array entry. The assistant
append in terminal-state.ts is already guarded; this brings the user
append to parity. (Evidence: 100% of duplicated message_ids in prod are
role=user.)

Guard the append with a containment check so it only concatenates when
the array doesn't already hold a message with this id:

  CASE WHEN messages @> [{id}] THEN messages
       ELSE messages || [userMsg] END

The client mints a fresh id per distinct send (verified across all hook
revisions), so a repeated id is always the same message — skipping is
safe and never drops a distinct message. conversationId/updatedAt stay
unconditional so the stream marker still advances on a retry. The
dual-write to copilot_messages is already idempotent (ON CONFLICT).

Verified on Postgres: same id -> stays 1 element; different id -> 2.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/lib/copilot/chat/post.ts

@@ -326,10 +326,19 @@ async function persistUserMessage(params: {
         contexts,
       })
 
+      // Append the user message idempotently: only concatenate when the array
+      // doesn't already contain a message with this id. A repeated id here is
+      // always a retry/double-submit of the same message (the client mints a
+      // fresh id per distinct send), so skipping the append avoids duplicate
+      // entries while keeping the stream marker / updatedAt current.
       const [updated] = await db
         .update(copilotChats)
         .set({
-          messages: sql`${copilotChats.messages} || ${JSON.stringify([userMsg])}::jsonb`,
+          messages: sql`CASE
+            WHEN ${copilotChats.messages} @> ${JSON.stringify([{ id: userMessageId }])}::jsonb
+            THEN ${copilotChats.messages}
+            ELSE ${copilotChats.messages} || ${JSON.stringify([userMsg])}::jsonb
+          END`,
           conversationId: userMessageId,
           updatedAt: new Date(),
         })