fix(web): object tool args crashed React #31 — normalize at derive boundary (argsText); contract scenario replays real-plugin frame shapes end-to-end (73/73)

web/src/derive.ts

@@ -44,6 +44,19 @@ export interface ChatDerivation {
   busy: boolean;
 }
 
+// The plugin mirrors pi extension events verbatim: tool args arrive as a raw
+// JSON object (or string in older frames). Normalizing at this boundary keeps
+// the render layer string-only; regression: object args crashed React (#31).
+export function argsText(args: unknown): string {
+  if (typeof args === "string") return args;
+  if (args === null || args === undefined) return "";
+  try {
+    return JSON.stringify(args, null, 2) ?? "";
+  } catch {
+    return String(args);
+  }
+}
+
 export function deriveChat(events: EventFrame[]): ChatDerivation {
   const messages: ChatMessage[] = [];
   const tools = new Map<string, ToolState>();
@@ -57,7 +70,7 @@ export function deriveChat(events: EventFrame[]): ChatDerivation {
           tools.set(e.toolCallId, {
             id: e.toolCallId,
             name: e.toolName ?? "tool",
-            args: e.args ?? "",
+            args: argsText(e.args),
             running: true,
             isError: false,
             preview: "",
@@ -148,10 +161,11 @@ export interface TaskDerivation {
 const TODO_TOOL = "todo";
 const SUBAGENT_TOOL = "subagent";
 
-function parseJson(text: string | undefined | null): unknown {
-  if (typeof text !== "string" || text.length === 0) return undefined;
+function parseJson(raw: unknown): unknown {
+  if (typeof raw === "object" && raw !== null) return raw; // already-decoded args
+  if (typeof raw !== "string" || raw.length === 0) return undefined;
   try {
-    return JSON.parse(text) as unknown;
+    return JSON.parse(raw) as unknown;
   } catch {
     return undefined;
   }
@@ -234,7 +248,7 @@ export function deriveTasks(events: EventFrame[]): TaskDerivation {
         runningTools.push({
           id: e.toolCallId,
           name,
-          args: e.args ?? "",
+          args: argsText(e.args),
           running: true,
           isError: false,
           preview: "",