Function normalizeContentFromAPI

src/utils/messages.ts:2651–2751

(
  contentBlocks: BetaMessage['content'],
  tools: Tools,
  agentId?: AgentId,
)

// Sometimes the API returns empty messages (eg. "\n\n"). We need to filter these out,
// otherwise they will give an API error when we send them to the API next time we call query().
export function normalizeContentFromAPI(
  contentBlocks: BetaMessage['content'],
  tools: Tools,
  agentId?: AgentId,
): BetaMessage['content'] {
  if (!contentBlocks) {
    return []
  }
  return contentBlocks.map(contentBlock => {
    switch (contentBlock.type) {
      case 'tool_use': {
        if (
          typeof contentBlock.input !== 'string' &&
          !isObject(contentBlock.input)
        ) {
          // we stream tool use inputs as strings, but when we fall back, they're objects
          throw new Error('Tool use input must be a string or object')
        }

        // With fine-grained streaming on, we are getting a stringied JSON back from the API.
        // The API has strange behaviour, where it returns nested stringified JSONs, and so
        // we need to recursively parse these. If the top-level value returned from the API is
        // an empty string, this should become an empty object (nested values should be empty string).
        // TODO: This needs patching as recursive fields can still be stringified
        let normalizedInput: unknown
        if (typeof contentBlock.input === 'string') {
          const parsed = safeParseJSON(contentBlock.input)
          if (parsed === null && contentBlock.input.length > 0) {
            // TET/FC-v3 diagnostic: the streamed tool input JSON failed to
            // parse. We fall back to {} which means downstream validation
            // sees empty input. The raw prefix goes to debug log only — no
            // PII-tagged proto column exists for it yet.
            logEvent('tengu_tool_input_json_parse_fail', {
              toolName: sanitizeToolNameForAnalytics(contentBlock.name),
              inputLen: contentBlock.input.length,
            })
            if (process.env.USER_TYPE === 'ant') {
              logForDebugging(
                `tool input JSON parse fail: ${contentBlock.input.slice(0, 200)}`,
                { level: 'warn' },
              )
            }
          }
          normalizedInput = parsed ?? {}
        } else {
          normalizedInput = contentBlock.input
        }

        // Then apply tool-specific corrections
        if (typeof normalizedInput === 'object' && normalizedInput !== null) {
          const tool = findToolByName(tools, contentBlock.name)
          if (tool) {
            try {
              normalizedInput = normalizeToolInput(
                tool,
                normalizedInput as { [key: string]: unknown },
                agentId,
              )