services/toolUseSummary/toolUseSummaryGenerator.ts

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/**
 * Tool Use Summary Generator
 *
 * Generates human-readable summaries of completed tool batches using Haiku.
 * Used by the SDK to provide high-level progress updates to clients.
 */

import { E_TOOL_USE_SUMMARY_GENERATION_FAILED } from '../../constants/errorIds.js'
import { toError } from '../../utils/errors.js'
import { logError } from '../../utils/log.js'
import { jsonStringify } from '../../utils/slowOperations.js'
import { asSystemPrompt } from '../../utils/systemPromptType.js'
import { queryHaiku } from '../api/claude.js'

const TOOL_USE_SUMMARY_SYSTEM_PROMPT = `Write a short summary label describing what these tool calls accomplished. It appears as a single-line row in a mobile app and truncates around 30 characters, so think git-commit-subject, not sentence.

Keep the verb in past tense and the most distinctive noun. Drop articles, connectors, and long location context first.

Examples:
- Searched in auth/
- Fixed NPE in UserService
- Created signup endpoint
- Read config.json
- Ran failing tests`

type ToolInfo = {
  name: string
  input: unknown
  output: unknown
}

export type GenerateToolUseSummaryParams = {
  tools: ToolInfo[]
  signal: AbortSignal
  isNonInteractiveSession: boolean
  lastAssistantText?: string
}

/**
 * Generates a human-readable summary of completed tools.
 *
 * @param params - Parameters including tools executed and their results
 * @returns A brief summary string, or null if generation fails
 */
export async function generateToolUseSummary({
  tools,
  signal,
  isNonInteractiveSession,
  lastAssistantText,
}: GenerateToolUseSummaryParams): Promise<string | null> {
  if (tools.length === 0) {
    return null
  }

  try {
    // Build a concise representation of what tools did
    const toolSummaries = tools
      .map(tool => {
        const inputStr = truncateJson(tool.input, 300)
        const outputStr = truncateJson(tool.output, 300)
        return `Tool: ${tool.name}\nInput: ${inputStr}\nOutput: ${outputStr}`
      })
      .join('\n\n')

    const contextPrefix = lastAssistantText
      ? `User's intent (from assistant's last message): ${lastAssistantText.slice(0, 200)}\n\n`
      : ''

    const response = await queryHaiku({
      systemPrompt: asSystemPrompt([TOOL_USE_SUMMARY_SYSTEM_PROMPT]),
      userPrompt: `${contextPrefix}Tools completed:\n\n${toolSummaries}\n\nLabel:`,
      signal,
      options: {
        querySource: 'tool_use_summary_generation',
        enablePromptCaching: true,
        agents: [],
        isNonInteractiveSession,
        hasAppendSystemPrompt: false,
        mcpTools: [],
      },
    })

    const summary = response.message.content
      .filter(block => block.type === 'text')
      .map(block => (block.type === 'text' ? block.text : ''))
      .join('')
      .trim()

    return summary || null
  } catch (error) {
    // Log but don't fail - summaries are non-critical
    const err = toError(error)
    err.cause = { errorId: E_TOOL_USE_SUMMARY_GENERATION_FAILED }
    logError(err)
    return null
  }
}

/**
 * Truncates a JSON value to a maximum length for the prompt.
 */
function truncateJson(value: unknown, maxLength: number): string {
  try {
    const str = jsonStringify(value)
    if (str.length <= maxLength) {
      return str
    }
    return str.slice(0, maxLength - 3) + '...'
  } catch {
    return '[unable to serialize]'
  }
}