Add sliding window context management

src/utils/context-management.ts

@@ -0,0 +1,42 @@
+import { Anthropic } from "@anthropic-ai/sdk"
+import { countTokens } from "@anthropic-ai/tokenizer"
+
+export function slidingWindowContextManagement(
+	contextWindow: number,
+	systemPrompt: string,
+	messages: Anthropic.Messages.MessageParam[],
+	tools: Anthropic.Messages.Tool[]
+): Anthropic.Messages.MessageParam[] {
+	const adjustedContextWindow = contextWindow - 10000 // Buffer to account for tokenizer differences
+	const systemPromptTokens = countTokens(systemPrompt)
+	const toolsTokens = countTokens(JSON.stringify(tools))
+	let availableTokens = adjustedContextWindow - systemPromptTokens - toolsTokens
+	let totalMessageTokens = messages.reduce((sum, message) => sum + countMessageTokens(message), 0)
+
+	if (totalMessageTokens <= availableTokens) {
+		return messages
+	}
+
+	// If over limit, remove messages starting from the third message onwards (task and claude's step-by-step thought process are important to keep in context)
+	const newMessages = [...messages]
+	while (totalMessageTokens > availableTokens && newMessages.length > 2) {
+		const removedMessage = newMessages.splice(2, 1)[0]
+		const removedTokens = countMessageTokens(removedMessage)
+		totalMessageTokens -= removedTokens
+	}
+
+	if (totalMessageTokens > availableTokens) {
+		// Over the limit due to the first two messages
+		throw new Error("Task exceeds available context window")
+	}
+
+	return newMessages
+}
+
+function countMessageTokens(message: Anthropic.Messages.MessageParam): number {
+	if (typeof message.content === "string") {
+		return countTokens(message.content)
+	} else {
+		return countTokens(JSON.stringify(message.content))
+	}
+}