extractOpenAiResponses only took response.usage from response.completed, so a
stream cut by max_output_tokens (response.incomplete) lost its usage and fell
back to estimateUsage over the whole SSE text, over-counting cost and budget.
Read response.usage from any event that carries it.
Gemini reports the tokens of tool results (Google Search, URL context) in usageMetadata.toolUsePromptTokenCount, separate from promptTokenCount. The extractor ignored it, so usage and cost were under-counted.
With prompt caching enabled, Bedrock reports inputTokens as the non-cached input only; cacheReadInputTokens and cacheWriteInputTokens are separate counters. Subtracting the cache reads again undercounted promptTokens (clamped to 0) in both the JSON and the stream-scan paths.
Alex Castillo
Owen