[Init] Initial commit - NetMesh terminal manager

infrastructure/ai/harness/compactionPruner.ts

@@ -0,0 +1,107 @@
+import type { ModelMessage } from 'ai';
+import { estimateModelMessagesTokensWithKind } from './tokenEstimator';
+import { COMPACTION_PROMPT_RESERVE } from './contextBudget';
+
+function endsWithToolCall(message: ModelMessage | undefined): boolean {
+  if (!message || message.role !== 'assistant' || !Array.isArray(message.content)) return false;
+  return message.content.some((part) => {
+    return part && typeof part === 'object' && (part as { type?: string }).type === 'tool-call';
+  });
+}
+
+function startsWithToolResult(message: ModelMessage | undefined): boolean {
+  if (!message || message.role !== 'tool') return false;
+  if (!Array.isArray(message.content)) return true;
+  return message.content.some((part) => {
+    return part && typeof part === 'object' && (part as { type?: string }).type === 'tool-result';
+  });
+}
+
+function skipToolResultsForward(messages: ModelMessage[], startIndex: number): number {
+  let index = startIndex;
+  while (index < messages.length && startsWithToolResult(messages[index])) index += 1;
+  return index;
+}
+
+function findToolResultsStart(messages: ModelMessage[]): number {
+  let index = messages.length;
+  while (index > 0 && startsWithToolResult(messages[index - 1])) index -= 1;
+  return index;
+}
+
+/** Prune from the tail while preserving valid tool-call/tool-result pairing. */
+export function pruneLastModelMessage(messages: ModelMessage[]): ModelMessage[] {
+  if (messages.length === 0) return messages;
+  if (messages.length === 1) return [];
+
+  const trailingToolStart = findToolResultsStart(messages);
+  if (trailingToolStart < messages.length) {
+    const preceding = messages[trailingToolStart - 1];
+    return preceding?.role === 'assistant' && endsWithToolCall(preceding)
+      ? messages.slice(0, trailingToolStart - 1)
+      : messages.slice(0, trailingToolStart);
+  }
+
+  const secondToLastIndex = messages.length - 2;
+  const secondToLast = messages[secondToLastIndex];
+
+  if (secondToLast.role === 'assistant' && endsWithToolCall(secondToLast)) {
+    return messages.slice(0, -2);
+  }
+  if (secondToLast.role === 'user') {
+    return messages.slice(0, -2);
+  }
+  return messages.slice(0, -1);
+}
+
+/** Prune from the head while preserving valid tool-call/tool-result pairing. */
+export function pruneFirstModelMessage(messages: ModelMessage[]): ModelMessage[] {
+  if (messages.length === 0) return messages;
+  if (messages.length === 1) return [];
+
+  const first = messages[0];
+  const second = messages[1];
+
+  if (first.role === 'assistant' && endsWithToolCall(first)) {
+    return messages.slice(skipToolResultsForward(messages, 1));
+  }
+  if (first.role === 'user' && second?.role === 'assistant' && endsWithToolCall(second)) {
+    return messages.slice(skipToolResultsForward(messages, 2));
+  }
+  if (first.role === 'user' && second?.role === 'assistant') {
+    return messages.slice(2);
+  }
+  if (startsWithToolResult(first)) {
+    return messages.slice(skipToolResultsForward(messages, 0));
+  }
+
+  return messages.slice(1);
+}
+
+export function countMessagesTokens(messages: ModelMessage[], providerId?: string | null): number {
+  return estimateModelMessagesTokensWithKind({ messages, providerId }).tokens;
+}
+
+export interface PruneUntilFitsCompactionInput {
+  messages: ModelMessage[];
+  availableForInput: number;
+  providerId?: string | null;
+  compactionPromptTokens?: number;
+}
+
+export function pruneUntilFitsCompaction(input: PruneUntilFitsCompactionInput): ModelMessage[] {
+  const reserve = input.compactionPromptTokens ?? COMPACTION_PROMPT_RESERVE;
+  let working = input.messages;
+
+  while (working.length > 0) {
+    const tokens = countMessagesTokens(working, input.providerId) + reserve;
+    if (tokens <= input.availableForInput) {
+      return working;
+    }
+    const pruned = pruneFirstModelMessage(working);
+    if (pruned.length === working.length) break;
+    working = pruned;
+  }
+
+  return working;
+}