fix(ai): clamp MiniMax shared budget max tokens

closes #6061
2026-06-25 12:00:37 +02:00
parent 8c9dbffa36
commit b940c52e7e
9 changed files with 356 additions and 0 deletions
@@ -0,0 +1,127 @@
+import type { AssistantMessage, Context, ImageContent, Message, TextContent, Usage } from "../types.ts";
+
+export interface ContextUsageEstimate {
+	/** Estimated total context tokens. */
+	tokens: number;
+	/** Tokens reported by the most recent assistant usage block. */
+	usageTokens: number;
+	/** Estimated tokens after the most recent assistant usage block. */
+	trailingTokens: number;
+	/** Index of the message that provided usage, or null when none exists. */
+	lastUsageIndex: number | null;
+}
+
+const CHARS_PER_TOKEN = 4;
+const ESTIMATED_IMAGE_CHARS = 4800;
+
+export function calculateContextTokens(usage: Usage): number {
+	return usage.totalTokens || usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+}
+
+function safeJsonStringify(value: unknown): string {
+	try {
+		return JSON.stringify(value) ?? "undefined";
+	} catch {
+		return "[unserializable]";
+	}
+}
+
+function estimateTextAndImageContentChars(content: string | Array<TextContent | ImageContent>): number {
+	if (typeof content === "string") return content.length;
+
+	let chars = 0;
+	for (const block of content) {
+		chars += block.type === "text" ? block.text.length : ESTIMATED_IMAGE_CHARS;
+	}
+	return chars;
+}
+
+export function estimateTextTokens(text: string): number {
+	return Math.ceil(text.length / CHARS_PER_TOKEN);
+}
+
+export function estimateTextAndImageContentTokens(content: string | Array<TextContent | ImageContent>): number {
+	return Math.ceil(estimateTextAndImageContentChars(content) / CHARS_PER_TOKEN);
+}
+
+export function estimateMessageTokens(message: Message): number {
+	let chars = 0;
+
+	switch (message.role) {
+		case "user":
+			return estimateTextAndImageContentTokens(message.content);
+		case "assistant":
+			for (const block of message.content) {
+				if (block.type === "text") {
+					chars += block.text.length;
+				} else if (block.type === "thinking") {
+					chars += block.thinking.length;
+				} else {
+					chars += block.name.length + safeJsonStringify(block.arguments).length;
+				}
+			}
+			break;
+		case "toolResult":
+			chars = estimateTextAndImageContentChars(message.content);
+			break;
+	}
+
+	return Math.ceil(chars / CHARS_PER_TOKEN);
+}
+
+function getLastAssistantUsageInfo(messages: readonly Message[]): { usage: Usage; index: number } | undefined {
+	for (let i = messages.length - 1; i >= 0; i--) {
+		const message = messages[i];
+		if (message.role !== "assistant") continue;
+		const assistant = message as AssistantMessage;
+		if (assistant.stopReason === "aborted" || assistant.stopReason === "error") continue;
+		if (calculateContextTokens(assistant.usage) > 0) return { usage: assistant.usage, index: i };
+	}
+	return undefined;
+}
+
+function estimateMessages(messages: readonly Message[]): ContextUsageEstimate {
+	const usageInfo = getLastAssistantUsageInfo(messages);
+
+	if (!usageInfo) {
+		let estimated = 0;
+		for (const message of messages) estimated += estimateMessageTokens(message);
+		return { tokens: estimated, usageTokens: 0, trailingTokens: estimated, lastUsageIndex: null };
+	}
+
+	const usageTokens = calculateContextTokens(usageInfo.usage);
+	let trailingTokens = 0;
+	for (let i = usageInfo.index + 1; i < messages.length; i++) {
+		trailingTokens += estimateMessageTokens(messages[i]);
+	}
+
+	return {
+		tokens: usageTokens + trailingTokens,
+		usageTokens,
+		trailingTokens,
+		lastUsageIndex: usageInfo.index,
+	};
+}
+
+function isMessageArray(value: Context | readonly Message[]): value is readonly Message[] {
+	return Array.isArray(value);
+}
+
+export function estimateContextTokens(context: Context | readonly Message[]): ContextUsageEstimate {
+	if (isMessageArray(context)) return estimateMessages(context);
+
+	const estimate = estimateMessages(context.messages);
+	if (estimate.lastUsageIndex !== null) return estimate;
+
+	let prefixTokens = context.systemPrompt ? estimateTextTokens(context.systemPrompt) : 0;
+	if (context.tools && context.tools.length > 0) {
+		prefixTokens += estimateTextTokens(safeJsonStringify(context.tools));
+	}
+
+	return {
+		tokens: estimate.tokens + prefixTokens,
+		usageTokens: estimate.usageTokens,
+		trailingTokens: estimate.trailingTokens + prefixTokens,
+		lastUsageIndex: estimate.lastUsageIndex,
+	};
+}