perf(core): reduce queue head churn

extensions/discord/src/internal/event-queue.ts

@@ -31,6 +31,7 @@ const DEFAULT_SLOW_LISTENER_THRESHOLD_MS = 30_000;
 export class DiscordEventQueue {
   private readonly options: Required<DiscordEventQueueOptions>;
   private readonly queue: DiscordEventQueueJob[] = [];
+  private queueHead = 0;
   private processing = 0;
   private processedCount = 0;
   private droppedCount = 0;
@@ -52,7 +53,7 @@ export class DiscordEventQueue {
   }
 
   enqueue(params: Omit<DiscordEventQueueJob, "resolve" | "reject">): Promise<void> {
-    if (this.queue.length >= this.options.maxQueueSize) {
+    if (this.pendingQueueSize >= this.options.maxQueueSize) {
       this.droppedCount += 1;
       return Promise.reject(
         new Error(
@@ -68,7 +69,7 @@ export class DiscordEventQueue {
 
   getMetrics(): DiscordEventQueueMetrics {
     return {
-      queueSize: this.queue.length,
+      queueSize: this.pendingQueueSize,
       processing: this.processing,
       processed: this.processedCount,
       dropped: this.droppedCount,
@@ -78,9 +79,31 @@ export class DiscordEventQueue {
     };
   }
 
+  private get pendingQueueSize(): number {
+    return Math.max(0, this.queue.length - this.queueHead);
+  }
+
+  private takeNextJob(): DiscordEventQueueJob | undefined {
+    if (this.queueHead >= this.queue.length) {
+      this.queue.length = 0;
+      this.queueHead = 0;
+      return undefined;
+    }
+    const job = this.queue[this.queueHead];
+    this.queueHead += 1;
+    if (this.queueHead >= this.queue.length) {
+      this.queue.length = 0;
+      this.queueHead = 0;
+    } else if (this.queueHead > 256 && this.queueHead * 2 > this.queue.length) {
+      this.queue.splice(0, this.queueHead);
+      this.queueHead = 0;
+    }
+    return job;
+  }
+
   private processNext(): void {
-    while (this.processing < this.options.maxConcurrency && this.queue.length > 0) {
-      const job = this.queue.shift();
+    while (this.processing < this.options.maxConcurrency && this.pendingQueueSize > 0) {
+      const job = this.takeNextJob();
       if (!job) {
         return;
       }

extensions/mattermost/src/mattermost/client.ts

@@ -394,16 +394,24 @@ function isRetryableError(error: Error): boolean {
     return false;
   }
 
-  const codes = candidates
-    .map((candidate) => readErrorCode(candidate))
-    .filter((code): code is string => Boolean(code));
+  const codes: string[] = [];
+  for (const candidate of candidates) {
+    const code = readErrorCode(candidate);
+    if (code) {
+      codes.push(code);
+    }
+  }
   if (codes.some((code) => RETRYABLE_NETWORK_ERROR_CODES.has(code))) {
     return true;
   }
 
-  const names = candidates
-    .map((candidate) => readErrorName(candidate))
-    .filter((name): name is string => Boolean(name));
+  const names: string[] = [];
+  for (const candidate of candidates) {
+    const name = readErrorName(candidate);
+    if (name) {
+      names.push(name);
+    }
+  }
   if (names.some((name) => RETRYABLE_NETWORK_ERROR_NAMES.has(name))) {
     return true;
   }
@@ -415,11 +423,13 @@ function isRetryableError(error: Error): boolean {
 
 function collectErrorCandidates(error: unknown): unknown[] {
   const queue: unknown[] = [error];
+  let queueIndex = 0;
   const seen = new Set<unknown>();
   const candidates: unknown[] = [];
 
-  while (queue.length > 0) {
-    const current = queue.shift();
+  while (queueIndex < queue.length) {
+    const current = queue[queueIndex];
+    queueIndex += 1;
     if (!current || seen.has(current)) {
       continue;
     }

src/agents/bash-process-registry.ts

@@ -247,9 +247,17 @@ function capPendingBuffer(buffer: string[], pendingChars: number, cap: number) {
     buffer.push(last.slice(last.length - cap));
     return cap;
   }
-  while (buffer.length && pendingChars - buffer[0].length >= cap) {
-    pendingChars -= buffer[0].length;
-    buffer.shift();
+  let dropCount = 0;
+  while (dropCount < buffer.length) {
+    const chunk = buffer[dropCount];
+    if (chunk === undefined || pendingChars - chunk.length < cap) {
+      break;
+    }
+    pendingChars -= chunk.length;
+    dropCount += 1;
+  }
+  if (dropCount > 0) {
+    buffer.splice(0, dropCount);
   }
   if (buffer.length && pendingChars > cap) {
     const overflow = pendingChars - cap;

src/agents/pi-embedded-runner/transcript-file-state.ts

@@ -114,9 +114,10 @@ export class TranscriptFileState {
     const branch: SessionEntry[] = [];
     let current = (fromId ?? this.leafId) ? this.byId.get((fromId ?? this.leafId)!) : undefined;
     while (current) {
-      branch.unshift(current);
+      branch.push(current);
       current = current.parentId ? this.byId.get(current.parentId) : undefined;
     }
+    branch.reverse();
     return branch;
   }
 

src/agents/tool-loop-detection.ts

@@ -660,7 +660,7 @@ export function recordToolCall(
   });
 
   if (state.toolCallHistory.length > resolvedConfig.historySize) {
-    state.toolCallHistory.shift();
+    state.toolCallHistory.splice(0, state.toolCallHistory.length - resolvedConfig.historySize);
   }
 }