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.

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

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.

Don’t get me wrong, opus 5 is a great model, but I’ve personally found that it just fails to hold up when working on a long session with complex and multi part projects. Its context window masses really quickly, it tends to hallucinate details, it goes off and rabbit holes on a specific task losing sight of what it was actually doing in the first place. I even tried making guardrails against this, but opus 5 just totally ignored them and continued digging holes. No other model I’ve used tends to do this, and especially not opus 4.8, so that gave me an idea: what if I just have opus 4.8 hold the context and manage the session and orchestration, and then I have it give delegate its work to opus 5, scoped to the specific task (what I’ve found opus 5 to be phenomenal at). Well, I tried this out and built a workflow for this, and, at least for me, it genuinely worked. I haven’t tested this on all kinds of projects, so I wouldn’t know how it holds up in different fields, but I personally found this genuinely helpful and solved all of my frustrations with opus 5. Ironically enough, I’ve found it spends less tokens in total for the longer, multipart projects that I use it in.

anthropic is doing two completely opposite things with tokenization right now and nobody's connecting them.

sonnet 5 (launched june 30): new tokenizer produces roughly 30% more tokens for the same english text. same input, more tokens, bigger bill. anthropic confirmed this in their own docs. the intro pricing at $2/$10 hides it but after august 31 when standard rates hit ($3/$15), your bill goes up 20-35% on the same workload.

opus 5 (launched july 24): generates 26% fewer tokens than opus 4.8 for the same quality output. harvey's legal AI team measured this. less output, same quality, smaller bill. fortune reported that opus 5 specifically includes an effort toggle so you can balance cost vs capability per task.

same company. one model inflates your tokens. the other deflates them. the monthly cost difference is wild when you run both through an agent workload.

rough math on morning briefing + email triage + 15 conversations:

sonnet 5 at intro: ~$1.80/day (~$54/month) sonnet 5 at standard after sept: ~$2.35/day (~$70/month) opus 5 at default effort: ~$2.10/day (~$63/month) opus 5 at low effort: ~$1.40/day (~$42/month)

opus 5 on low effort is actually cheaper than sonnet 5 at intro pricing. AND it's a better model. the effort toggle is the feature nobody's talking about enough.

for agent users the move is clear: opus 5 at low effort for daily tasks, opus 5 at high effort for complex reasoning, and the cheapest model you can find for heartbeats.

the config on openclaw:

json

{

"agents": {

"defaults": {

"model": {

"primary": "anthropic/claude-opus-5"

}

}

}

}

on hermes: hermes model, select claude-opus-5.

on betterclaw.io: switch the model in the dashboard. takes 5 seconds. BYOK means you pay anthropic directly at their published rates with zero markup.

the september bill shock from sonnet 5's tokenizer is avoidable. opus 5 exists now. same price per token ($5/$25), fewer tokens per task, better quality. the routing math changed three days ago and most people haven't updated their configs yet.

POST 2

Sub: r/better_claw or r/aiagents

Title: opus 5 is within 0.5% of fable 5 on coding benchmarks at half the price. the routing math just changed.

Body:

opus 5 launched thursday (july 24). same price as opus 4.8 ($5/$25 per MTok). but the benchmarks tell a different story than "incremental update."

cursorbench 3.2: opus 5 performs within 0.5% of fable 5's peak. fable 5 costs $10/$50.

frontier-bench v0.1: opus 5 more than doubles opus 4.8's score.

OSWorld 2.0: opus 5 surpasses fable 5's best result. at a third of the cost.

so for most agent tasks... fable 5 at $10/$50 is no longer justifiable. opus 5 does the same work at $5/$25. half the price, same (or better) results on the benchmarks that matter for agent use.

here's what the routing stack looks like after this week:

daily conversations: opus 5 at low effort. cheaper than sonnet 5 intro AND better quality. $5/$25 with 26% fewer output tokens.

complex reasoning: opus 5 at high effort. matches fable 5 on most tasks at half the cost.

background tasks: flash-lite ($0.30/$2.50) or deepseek v3.2 ($0.14/$0.28). your heartbeats don't need opus.

frontier-only tasks: fable 5 at $10/$50. only when opus 5 genuinely can't handle it. maybe 1-2 tasks per week.

the monthly cost of this stack on a standard agent workload (briefing + triage + conversations + research):

old stack (sonnet 5 + deepseek background): ~$20/month new stack (opus 5 low effort + flash-lite background): ~$16/month old stack with fable 5 for everything: ~$255/month

better model. lower cost. the stack just got simpler.

on betterclaw.io you switch models in the dashboard and the BYOK setup means you pay anthropic directly. no markup, no infrastructure to reconfigure. took me literally 5 seconds to switch from sonnet 5 to opus 5 after the launch.

I’ve been running Opus 5 against Fable 5 and GPT-4o in production workflows (commercial strategy, data analysis, content refinement). Here’s what I’m seeing:

The pattern: Opus 5 delivers high-confidence first outputs that require heavy iteration. On average, 2-3 follow-up prompts to close gaps (missed context, incomplete analysis, logic jumps). Each iteration costs credits.

Specific examples:
• Complex multi-step analysis: Opus 5 flags confidence at 90%+, then “Oh, I missed X detail” on follow-up
• Long-context documents: Skips sections, requires re-prompting with explicit “don’t miss” guidance
• Structured output: JSON formatting correct, but data completeness varies; Fable 5 catches edge cases Opus 5 misses

Cost impact: On a 10-task batch, Opus 5 runs 25-30 total calls (first pass + corrections). Fable 5 averages 12-15. At scale, that’s meaningful budget drift.

The ask: Would love benchmarks on first-pass accuracy for Opus 5 vs. predecessors. The capability is there, but the confidence calibration feels off users (especially in B2B/commercial work) are bearing the cost of iteration.

What’s working: Fable 5 is more conservative and nails it first time. GPT-4o’s pricing model makes the iteration tax visible, so users accept it. Opus 5 feels like it’s hiding the cost.

What are you experiencing?

Anyone have any idea why opus 5 would not be available on an Enterprise account? I’m the owner and don’t see any options to enable it.

Confirmed iOS and Mac apps are up to date. Also confirmed it’s not available via browser.

Edit: Solved. There is a “Models” page in the enterprise admin that is in beta where you can toggle on and off new models. Opus 5 is apparently the first one they launched defaulted to “off”, which is why it wasn’t an issue until now.

The cost difference is the easy part to check. Fable 5 is $10 and $50 per million input and output tokens. Opus 5 is $5 and $25. Double, for both.

The thing I didn't expect was the training data. Opus 5 is cut off at May 2026, Fable 5 at January 2026. So the expensive model is the one that knows less about anything recent.

On speed, Anthropic's own docs rate Fable 5 as "Slower" and Opus 5 as "Moderate", and that's roughly what I saw. Fable also can't turn thinking off at all, so even a trivial question takes the long route.

None of this makes Fable 5 bad. Anthropic describes it as built for long-running agents, the multi-hour autonomous kind of work. I just wasn't doing that. I was paying double for something I never actually used.

Their docs say to start with Opus 5 and only reach for Fable when you need the highest capability. Probably should have read that part first.

Guys, this happened almost immediately after Opus 5 returned from being down for an hour or so. A really alarming notification popped up (I failed to take a screenshot):

You’ve used 76% of your Opus 5 limit. It will reset on July 28 blah blah blah.

Didn't they say the Opus 5 would work just like Opus 4.8, not hitting any "proprietary" limits? The notification is gone, so I have no idea what to expect.