Function extractDiscoveredToolNames

src/utils/toolSearch.ts:547–594

(messages: Message[])

 * @returns Set of tool names that have been discovered via tool_reference blocks
 */
export function extractDiscoveredToolNames(messages: Message[]): Set<string> {
  const discoveredTools = new Set<string>()
  let carriedFromBoundary = 0

  for (const msg of messages) {
    // Compact boundary carries the pre-compact discovered set. Inline type
    // check rather than isCompactBoundaryMessage — utils/messages.ts imports
    // from this file, so importing back would be circular.
    if (msg.type === 'system' && msg.subtype === 'compact_boundary') {
      const carried = msg.compactMetadata?.preCompactDiscoveredTools
      if (carried) {
        for (const name of carried) discoveredTools.add(name)
        carriedFromBoundary += carried.length
      }
      continue
    }

    // Only user messages contain tool_result blocks (responses to tool_use)
    if (msg.type !== 'user') continue

    const content = msg.message?.content
    if (!Array.isArray(content)) continue

    for (const block of content) {
      // tool_reference blocks only appear inside tool_result content, specifically
      // in results from ToolSearchTool. The API expands these references into full
      // tool definitions in the model's context.
      if (isToolResultBlockWithContent(block)) {
        for (const item of block.content) {
          if (isToolReferenceWithName(item)) {
            discoveredTools.add(item.tool_name)
          }
        }
      }
    }
  }

  if (discoveredTools.size > 0) {
    logForDebugging(
      `Dynamic tool loading: found ${discoveredTools.size} discovered tools in message history` +
        (carriedFromBoundary > 0
          ? ` (${carriedFromBoundary} carried from compact boundary)`
          : ''),
    )
  }

  return discoveredTools
}

export type DeferredToolsDelta = {
  addedNames: string[]