perf(web): long threads stream with 70% less work-row derivation (#29971)

Author: Entrpi

packages/client-runtime/src/work-log/presentation.ts

@@ -291,12 +291,31 @@ function workEntryIndicatesToolFailureFromOutput(
   return output.length > 0 && toolOutputIndicatesFailure(output);
 }
 
+// Rows are re-derived on every timeline update but entries are reused while
+// their item is unchanged, so these per-entry checks are computed once.
+const entryChecks = new WeakMap<
+  WorkLogPresentationEntry,
+  { failure?: boolean; displayFailure?: boolean; action?: ToolGroupAction }
+>();
+
+function checksFor(entry: WorkLogPresentationEntry) {
+  let checks = entryChecks.get(entry);
+  if (!checks) {
+    checks = {};
+    entryChecks.set(entry, checks);
+  }
+  return checks;
+}
+
 export function workEntryIndicatesToolFailure(entry: WorkLogPresentationEntry): boolean {
-  return workEntryIndicatesToolFailureFromOutput(entry, true);
+  return (checksFor(entry).failure ??= workEntryIndicatesToolFailureFromOutput(entry, true));
 }
 
 export function workEntryDisplayIndicatesToolFailure(entry: WorkLogPresentationEntry): boolean {
-  return workEntryIndicatesToolFailureFromOutput(entry, false);
+  return (checksFor(entry).displayFailure ??= workEntryIndicatesToolFailureFromOutput(
+    entry,
+    false,
+  ));
 }
 
 function workLogEntryIsLocalCodeSearch(entry: WorkLogPresentationEntry): boolean {
@@ -308,6 +327,10 @@ function workLogEntryIsLocalCodeSearch(entry: WorkLogPresentationEntry): boolean
 }
 
 export function toolGroupAction(entry: WorkLogPresentationEntry): ToolGroupAction {
+  return (checksFor(entry).action ??= computeToolGroupAction(entry));
+}
+
+function computeToolGroupAction(entry: WorkLogPresentationEntry): ToolGroupAction {
   if (entry.itemType === "thread_created") return "thread-create";
   const presentation = resolveWorkEntryToolPresentation(entry);
   if (presentation?.action !== undefined) return presentation.action;

packages/shared/src/t3McpToolPresentation.ts

@@ -380,8 +380,24 @@ function normalizeT3McpToolLabel(value: string): string {
   return value.replace(/\s+(?:complete|completed)\s*$/i, "").trim();
 }
 
-// ACP tool prefixes vary; match loosely but require a known display-name entry.
+// Timelines resolve every work row's tool name on each update; names repeat across updates.
+// ACP titles can carry whole commands, so long labels are parsed but not kept.
+const toolNameCache = new Map<string, string | null>();
+const TOOL_NAME_CACHE_LIMIT = 10_000;
+const TOOL_NAME_CACHE_MAX_KEY_LENGTH = 256;
+
 function resolveT3McpToolName(value: string): string | null {
+  if (value.length > TOOL_NAME_CACHE_MAX_KEY_LENGTH) return parseT3McpToolName(value);
+  const cached = toolNameCache.get(value);
+  if (cached !== undefined) return cached;
+  const name = parseT3McpToolName(value);
+  if (toolNameCache.size >= TOOL_NAME_CACHE_LIMIT) toolNameCache.clear();
+  toolNameCache.set(value, name);
+  return name;
+}
+
+// ACP tool prefixes vary; match loosely but require a known display-name entry.
+function parseT3McpToolName(value: string): string | null {
   const label = normalizeT3McpToolLabel(value);
   const mcpMatch = /^mcp__(?<server>.+?)__(?<tool>.+)$/i.exec(label);
   if (mcpMatch?.groups) {