fix: update thread persona_id on every message send

The frontend already passes personaId into acpSendMessage, but it was
only used for session tracker lookup — never forwarded to the backend.
After a mid-session persona switch and page reload, the session list
showed the stale persona from session creation.

Forward personaId in the prompt request's _meta field and extract it
in on_prompt to update the thread's persona_id metadata, mirroring
how model_id and provider_id are already kept in sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: matt2e

crates/goose/src/acp/server.rs

@@ -2227,6 +2227,21 @@ impl GooseAcpAgent {
         let t_start = std::time::Instant::now();
         debug!(target: "perf", sid = %sid, "perf: prompt start");
 
+        // Update persona_id on the thread if the client sent one in _meta.
+        let prompt_persona_id = args
+            .meta
+            .as_ref()
+            .and_then(|m| m.get("personaId"))
+            .and_then(|v| v.as_str())
+            .map(|s| s.to_string());
+        if let Some(ref pid) = prompt_persona_id {
+            let pid = pid.clone();
+            self.update_thread_metadata(&thread_id, move |meta| {
+                meta.persona_id = Some(pid);
+            })
+            .await?;
+        }
+
         let cancel_token = CancellationToken::new();
         let internal_session_id = self.internal_session_id(&thread_id).await?;
 

ui/goose2/src/shared/api/acp.ts

@@ -95,7 +95,13 @@ export async function acpSendMessage(
     `[perf:send] ${sid} acpSendMessage → prompt(len=${prompt.length}, imgs=${images?.length ?? 0})`,
   );
   const tPrompt = performance.now();
-  await directAcp.prompt(gooseSessionId, content);
+  const meta: Record<string, unknown> = {};
+  if (personaId) meta.personaId = personaId;
+  await directAcp.prompt(
+    gooseSessionId,
+    content,
+    Object.keys(meta).length > 0 ? meta : undefined,
+  );
   const tDone = performance.now();
   perfLog(
     `[perf:send] ${sid} prompt() resolved in ${(tDone - tPrompt).toFixed(1)}ms (total acpSendMessage ${(tDone - tStart).toFixed(1)}ms)`,

ui/goose2/src/shared/api/acpApi.ts

@@ -231,7 +231,8 @@ export async function loadSession(
 export async function prompt(
   sessionId: string,
   content: ContentBlock[],
+  meta?: Record<string, unknown>,
 ): Promise<PromptResponse> {
   const client = await getClient();
-  return client.prompt({ sessionId, prompt: content });
+  return client.prompt({ sessionId, prompt: content, _meta: meta });
 }