feat(chat,seahorse): persist and display model_name across history (#2897)

* feat(chat,seahorse): persist and display model_name across history

* test(seahorse): fix lint regressions in repair coverage

* fix(pico): preserve model_name in live updates

* fix(pico): preserve model_name through live stream wrappers

web/frontend/src/features/chat/history.ts

@@ -50,6 +50,7 @@ export async function loadSessionMessages(
     role: message.role,
     content: message.content,
     kind: message.role === "assistant" ? (message.kind ?? "normal") : undefined,
+    modelName: message.model_name,
     toolCalls:
       message.role === "assistant"
         ? parseToolCallsValue(message.tool_calls)
@@ -86,7 +87,7 @@ function messageSignature(message: ChatMessage): string {
 
   return `${message.role}\u0000${message.content}\u0000${normalizeMessageTimestamp(
     message.timestamp,
-  )}\u0000${message.kind ?? ""}\u0000${attachmentSignature}\u0000${toolCallsSignature(
+  )}\u0000${message.kind ?? ""}\u0000${message.modelName ?? ""}\u0000${attachmentSignature}\u0000${toolCallsSignature(
     message.toolCalls,
   )}`
 }

web/frontend/src/features/chat/protocol.ts

@@ -83,6 +83,14 @@ function parseContextUsage(
   }
 }
 
+function parseModelName(payload: Record<string, unknown>): string | undefined {
+  if (typeof payload.model_name !== "string") {
+    return undefined
+  }
+  const modelName = payload.model_name.trim()
+  return modelName || undefined
+}
+
 export function handlePicoMessage(
   message: PicoMessage,
   expectedSessionId: string,
@@ -102,6 +110,7 @@ export function handlePicoMessage(
       const attachments = parseAttachments(payload)
       const contextUsage = parseContextUsage(payload)
       const isPlaceholder = payload.placeholder === true
+      const modelName = parseModelName(payload)
       const timestamp =
         message.timestamp !== undefined &&
         Number.isFinite(Number(message.timestamp))
@@ -116,6 +125,7 @@ export function handlePicoMessage(
             role: "assistant",
             content,
             kind,
+            ...(modelName ? { modelName } : {}),
             ...(toolCalls ? { toolCalls } : {}),
             attachments,
             timestamp,
@@ -135,6 +145,7 @@ export function handlePicoMessage(
       const messageId = payload.message_id as string
       const attachments = parseAttachments(payload)
       const contextUsage = parseContextUsage(payload)
+      const modelName = parseModelName(payload)
       const timestamp =
         message.timestamp !== undefined &&
         Number.isFinite(Number(message.timestamp))
@@ -160,6 +171,7 @@ export function handlePicoMessage(
               content,
               kind,
               toolCalls,
+              ...(modelName ? { modelName } : {}),
               ...(attachments ? { attachments } : {}),
             }
           })
@@ -178,6 +190,7 @@ export function handlePicoMessage(
               content,
               kind,
               toolCalls,
+              ...(modelName ? { modelName } : {}),
               ...(attachments ? { attachments } : {}),
               timestamp,
             },