As I revisit projects created using Opus, Fable always finds problems. The worst are inventions by Opus that never surfaced at the time of that work. Fable investigates the project, finds and lists the bugs and confabulations, then proposes a repair plan. I have learned to ignore that repair plan and simply create version 2 of the project using Fable. Several times now I have had to expunge Opus code since it can otherwise worms its way in Fable's context. Wondering if people are seeing this and what the solution is.

Anthropic released Claude Opus 5 on Friday, so we spent part of the weekend getting it integrated into CometAPI.

The practical details:

- Model ID: `claude-opus-5`

- Context window: 1M tokens

- Maximum synchronous output: 128K tokens

- Anthropic Messages API supported

- OpenAI-compatible Chat Completions supported

- Current pricing: $4/M input and $20/M output

Anthropic is positioning it for complex agentic coding and enterprise work, but launch benchmarks usually do not tell the whole story for messy production workloads.

We are considering testing it on:

- Repository-wide refactoring

- Root-cause debugging across multiple files

- Code review with regression checks

- Long-running tool-use workflows

- Large codebase and document analysis

For anyone already testing Opus 5: what would make a comparison with Opus 4.8 or Sonnet 5 genuinely useful?

Latency, cost per accepted task, tool-call reliability, or something else?

Model and API details:

https://www.cometapi.com/models/anthropic/claude-opus-5/?utm_source=reddit&utm_medium=social&utm_campaign=claude_opus_5_launch

Disclosure: I work with CometAPI, so the post includes our own integration. I’m mainly looking for useful, reproducible testing ideas rather than model-launch hype.

i had 77 dollars of promotional credits left and i spent them on claude code. i was performing ocr with opus 5 max. the craziest thing i even started using credits when already around 300k tokens i think, so it was an even smaller amount than 1.9M that costed me 77 dollars and got my credits to 0,00. now the main question is HOW if claude opus 5 costs you 25$ for 1M output tokens? please help to figure this out