Anthropic released Claude Opus 4 as a major generational upgrade over Opus 3.5. The jump in coding ability alone makes this one of the most significant model releases in recent memory. Here’s everything that changed, what stayed the same, and whether upgrading makes sense for your workflow.
For context on how Opus 4 fits into the broader Claude lineup, see the Claude Opus 4.7 complete guide.
Key Changes
| Opus 3.5 | Opus 4 | |
|---|---|---|
| Context window | 200K | 200K |
| SWE-bench score | ~49% | ~76.8% |
| Agentic capabilities | Limited | Strong (tool use, multi-step) |
| Instruction following | Good | Excellent |
| Input price | $15 / 1M tokens | $15 / 1M tokens |
| Output price | $75 / 1M tokens | $75 / 1M tokens |
| Multimodal | Text + images | Text + images |
Coding Performance
The biggest improvement by far. Opus 4 nearly doubled the SWE-bench score, jumping from approximately 49% to 76.8%. This isn’t a marginal improvement — it represents a fundamental leap in the model’s ability to understand and modify real-world codebases.
Opus 4 handles complex multi-file refactoring with architectural awareness. It understands project structure, respects existing patterns, and produces more complete solutions on the first attempt. Where Opus 3.5 would often generate partial fixes or miss edge cases, Opus 4 delivers production-ready changes more consistently.
For developers using Claude Code or similar agentic coding tools, this improvement is immediately noticeable. Tasks that required multiple back-and-forth iterations with Opus 3.5 often complete in a single pass with Opus 4. Learn more in our how to use Claude Code guide.
Agentic Workflows
Opus 4 introduced genuinely strong agentic capabilities. It can plan multi-step tasks, use tools reliably, and execute complex workflows autonomously. Opus 3.5 had basic tool use support, but it frequently lost track of goals during multi-step operations or made errors when chaining tool calls.
The improvement here matters for anyone building AI agents, automation pipelines, or using Claude in autonomous coding workflows. Opus 4 maintains coherence across long task chains and recovers more gracefully when individual steps fail.
Instruction Following
Opus 4 is measurably better at following detailed, multi-constraint instructions. When given a complex prompt with specific formatting requirements, content constraints, and structural rules, Opus 4 hits more of those requirements consistently. Opus 3.5 would occasionally drop constraints or take shortcuts, especially on longer prompts.
This improvement is particularly valuable for structured output generation, API response formatting, and any workflow where the model needs to follow a precise specification.
What Stayed the Same
Several things didn’t change between versions:
- Context window remains at 200K tokens. No expansion here.
- Pricing is identical at $15/$75 per million tokens for input/output. Anthropic kept the same price point.
- Multimodal support covers text and images in both versions. No video or audio additions.
- API compatibility is maintained. Switching from Opus 3.5 to Opus 4 requires only changing the model identifier.
What Didn’t Improve Enough
While Opus 4 is a major upgrade, it’s worth noting some areas where the improvement is less dramatic:
- Simple chat and summarization — For basic conversational tasks, the difference between Opus 3.5 and 4 is subtle. Both handle these well.
- Creative writing — Opus 4 is slightly better at following style constraints, but the raw creative output quality is similar.
- Speed — Opus 4 is not noticeably faster than Opus 3.5 for most tasks. The improvements are in quality, not latency.
How Opus 4 Compares to the Current Lineup
Opus 4 was the foundation, but Anthropic has since released Opus 4.5, 4.6, and 4.7. Each version brought incremental improvements. For a comparison of the more recent versions, see our Claude Opus 4.6 vs 4.5 breakdown.
If you’re still on Opus 3.5, jumping to the latest version (Opus 4.7) rather than Opus 4 makes more sense, since pricing hasn’t changed and each version is strictly better. Check the full AI model comparison to see where each version ranks.
Should You Upgrade?
Yes, if you use Claude for coding, agentic tasks, or complex analysis. The improvement from Opus 3.5 to Opus 4 is substantial and immediately noticeable. The SWE-bench score nearly doubling tells the story — this is a meaningfully better model for technical work.
Yes, if you build AI agents or automation pipelines. The agentic capabilities in Opus 4 are a generation ahead of what Opus 3.5 offered.
It matters less if you mainly use Claude for simple chat, summarization, or basic writing tasks. The difference is less pronounced for straightforward work, though Opus 4 is still the better model.
There’s no reason not to upgrade since pricing is identical. Opus 4 costs the same as Opus 3.5 and is better at everything. The only consideration is if you have workflows that depend on specific Opus 3.5 output patterns, in which case you should test before switching.
The Bottom Line
Opus 3.5 to Opus 4 was one of the largest single-generation improvements in the Claude model family. The coding leap alone justifies the upgrade. Combined with stronger agentic capabilities and better instruction following at the same price point, there’s no practical reason to stay on Opus 3.5.
If you haven’t upgraded yet, do it. And if you’re evaluating Claude for the first time, start with the latest version available rather than Opus 4 — the improvements have continued with each subsequent release.
FAQ
Is Claude Opus 4 better than 3.5?
Yes, significantly. Opus 4 nearly doubled the SWE-bench coding score (from ~49% to ~76.8%), added strong agentic capabilities, and improved instruction following. It’s better at every task category while maintaining the same pricing.
Is Opus 3.5 still available?
Opus 3.5 may still be accessible through the API for backward compatibility, but Anthropic has moved focus to Opus 4 and later versions. There’s no reason to use Opus 3.5 since Opus 4 is the same price and strictly better. Check Anthropic’s documentation for current model availability.
How much does Opus 4 cost?
Opus 4 costs $15 per million input tokens and $75 per million output tokens — the same pricing as Opus 3.5. This makes it one of the more expensive models available, but the pricing reflects its flagship-tier capabilities.
Should I upgrade from Opus 3.5?
Absolutely. Since pricing is identical, there’s no cost penalty for upgrading. The improvements in coding (nearly 2x on SWE-bench), agentic workflows, and instruction following are substantial. Test your existing workflows to ensure compatibility, then switch.