Claude Opus 4.5: Anthropic's Coding Lead Widens
Claude Opus 4.5 arrived November 2025 as Anthropic's refresh of the Opus 4 line — better tool use, stronger agentic performance, and Terminal-Bench Hard scores that pushed the coding agent leaderboard to new heights.
Six months after Claude 4 Opus, Anthropic ships the refresh. The headline: agentic coding gets better. Again.
Opus 4.5 isn't a dramatic architectural change — it's a continued refinement of the same hybrid (instant + thinking) model, with focused improvements on the things Anthropic cares most about: tool use, multi-step reasoning, and coding agent reliability.
What Improved
- Terminal-Bench Hard — Scores near the top of the agentic coding leaderboard at launch. Multiple third-party agents using Opus 4.5 as their model core debut in the top 10.
- Tool use reliability — Fewer dropped tool calls, better recovery from tool errors mid-task. This matters a lot in long-running agentic workflows.
- Extended thinking + tool use — The combination is more stable. Opus 4.5 maintains coherent context over longer chains of think → call → observe → think.
- Instruction following — Continued reduction in unnecessary refusals. Follows precise technical instructions without defaulting to hedged responses.
How It Compares at Launch
| Model | Terminal-Bench Hard | Agentic Tool Use | Notes |
|---|---|---|---|
| Claude Opus 4.5 | top 3 | ★★★★★ | Best coding agent at launch |
| Gemini 3 Pro | competitive | ★★★★☆ | Better general reasoning |
| GPT-5 | solid | ★★★★☆ | Better broad capability |
| Llama 4 Maverick | strong open-wt | ★★★★☆ | Best open-weight option |
| Opus 4.0 | previous leader | ★★★★☆ | Replaced by 4.5 |
Best For
- Everything you'd use Claude Code for — this is the engine underneath
- Multi-step coding tasks with file system access, test runs, iteration
- Any agentic workflow that needs reliable tool use over 10+ steps
Not For
- General conversation — Sonnet 4.5 (also updated) is faster and cheaper for this
- Multimodal-first tasks — Gemini 3 Pro is stronger here
- Open-weight deployments — still closed
Verdict
Opus 4.5 cements Anthropic's position as the leader for agentic software development. The gap on Terminal-Bench Hard between Anthropic's stack and everyone else is meaningful. If you're building AI coding workflows, there's still not a better model.
Part of our Model Watch series.