Function getEffectiveApiHistory

src/core/condense/index.ts:546–640

(messages: ApiMessage[])

 * @returns The filtered history that should be sent to the API
 */
export function getEffectiveApiHistory(messages: ApiMessage[]): ApiMessage[] {
	// Find the most recent summary message
	const lastSummary = findLast(messages, (msg) => msg.isSummary === true)

	if (lastSummary) {
		// Fresh start model: return only messages from the summary onwards
		const summaryIndex = messages.indexOf(lastSummary)
		let messagesFromSummary = messages.slice(summaryIndex)

		// Collect all tool_use IDs from assistant messages in the result
		// This is needed to filter out orphan tool_result blocks that reference
		// tool_use IDs from messages that were condensed away
		const toolUseIds = new Set<string>()
		for (const msg of messagesFromSummary) {
			if (msg.role === "assistant" && Array.isArray(msg.content)) {
				for (const block of msg.content) {
					if (block.type === "tool_use" && (block as Anthropic.Messages.ToolUseBlockParam).id) {
						toolUseIds.add((block as Anthropic.Messages.ToolUseBlockParam).id)
					}
				}
			}
		}

		// Filter out orphan tool_result blocks from user messages
		messagesFromSummary = messagesFromSummary
			.map((msg) => {
				if (msg.role === "user" && Array.isArray(msg.content)) {
					const filteredContent = msg.content.filter((block) => {
						if (block.type === "tool_result") {
							return toolUseIds.has((block as Anthropic.Messages.ToolResultBlockParam).tool_use_id)
						}
						return true
					})
					// If all content was filtered out, mark for removal
					if (filteredContent.length === 0) {
						return null
					}
					// If some content was filtered, return updated message
					if (filteredContent.length !== msg.content.length) {
						return { ...msg, content: filteredContent }
					}
				}
				return msg
			})
			.filter((msg): msg is ApiMessage => msg !== null)

		// Still need to filter out any truncated messages within this range
		const existingTruncationIds = new Set<string>()
		for (const msg of messagesFromSummary) {
			if (msg.isTruncationMarker && msg.truncationId) {
				existingTruncationIds.add(msg.truncationId)
			}
		}

		return messagesFromSummary.filter((msg) => {
			// Filter out truncated messages if their truncation marker exists
			if (msg.truncationParent && existingTruncationIds.has(msg.truncationParent)) {
				return false