Quick Answer
Claude Fable 5.1 is Anthropic's flagship: $10/$50 per million tokens, adaptive reasoning always on, 55.8% on Anthropic's long-task benchmark, and #1 on SWE-bench Pro at 81.2%. Claude Opus 5 is the value play at the top of the stack: $5/$25 — literally half price — with Artificial Analysis rating it narrowly most-intelligent on their index and calling it "near-Fable intelligence at half the price." Pick Opus 5 by default and budget; pick Fable 5.1 when you need the ceiling — the hardest long-horizon tasks, the cheapest agent-loop caching, or the full 1M-context reasoning depth.
Side by Side
| Claude Fable 5.1 | Claude Opus 5 | |
|---|---|---|
| API model ID | claude-fable-5-1 |
claude-opus-5 |
| Input / output per 1M | $10 / $50 | $5 / $25 |
| Fast mode | — | $10 / $50 |
| Cache read (per 1M) | $0.25 (75% cut from Fable 5) | ~$1.00 (Opus 4.8 carried that rate; confirm current) |
| Cache write (per 1M) | ~$12.50 | — |
| Context / max output | 1M / 128K | — / 128K (large context) |
| SWE-bench Verified | 95.0% | 96.0% |
| SWE-bench Pro | 81.2% (#1) | 79.2% |
| Speed | — | ~48.2 tok/s |
| Reasoning | Adaptive, always on; effort levels low→max | Standard |
Where Opus 5 Wins
- Half the price, period. $5/$25 vs $10/$50 — same rates Opus 4.8 carried. For workloads where both models clear the quality bar, Opus 5 halves the bill.
- Faster throughput. ~48.2 tok/s makes a visible difference in interactive coding sessions where you're watching output stream.
- The SWE-bench Verified edge. 96.0% vs Fable's 95.0% (per DataCamp's comparison) — on real-world GitHub-style bug fixes, Opus 5 is nominally ahead.
- Frontier-Bench v0.1 lead. Opus 5 tops that leaderboard, and Artificial Analysis rates it the most intelligent model on their aggregate index — by a hair, but ahead.
Where Fable 5.1 Wins
- Long-horizon tasks. 55.8% on Anthropic's long-task benchmark vs 42.0% for Fable 5 — and Fable 5.1 solves more of Anthropic's internal coding problems than either Fable 5 or Opus 5, per Anthropic's own announcement. Multi-hour agent runs are the gap that half price doesn't close.
- SWE-bench Pro #1. 81.2%, the top published score, ahead of Opus 5's 79.2%. On the harder, more realistic of the two SWE benchmarks, Fable 5.1 leads.
- Cache economics for agent loops. $0.25 per million cached tokens is 4x cheaper than Opus-class ~$1.00 cache reads — and Anthropic estimates ~25% typical (up to ~45% agentic) total-cost savings from that cut. In a long agent session where a 50K-token prefix re-reads every step, Fable 5.1's caching can erase a meaningful part of Opus 5's sticker advantage on its own.
- 1M context with adaptive reasoning tuned across low/medium/high/xhigh/max effort levels — changeable mid-conversation.
Which One for Which Workload
| Workload | Pick | Why |
|---|---|---|
| Everyday feature work, refactors | Opus 5 | Quality bar cleared at half price |
| Interactive pair programming | Opus 5 | ~48 tok/s + half price; fast mode ($10/$50) when you need bursts |
| Multi-hour autonomous agents | Fable 5.1 | Long-task benchmark gap (55.8% vs Opus-class) + $0.25 cache reads compound over long runs |
| Massive-repo / 1M-context analysis | Fable 5.1 | The full 1M window with the strongest reasoning |
| Hardest bug hunts, release-blocking defects | Fable 5.1 | SWE-bench Pro #1; the extra $5/$25 is cheap vs another failed attempt |
| High-volume batch pipelines | Opus 5 | Price-sensitive throughput |
The cheapest setup is usually both: route 80% of requests to Opus 5 and escalate the stubborn 20% to Fable 5.1. A gateway like TeamoRouter carries both behind one key with per-task routing.
The Third Corner: GPT-6 Astra
This comparison settles Anthropic's internal lineup, but the real 2026 decision is often three-way. GPT-6 Astra matches Fable 5.1's $10/$50 sticker, adds native multi-agent and best-in-class computer use, but its cache reads cost $1.00/M — 4x Fable 5.1's $0.25. The full triangle is in Fable 5.1 vs GPT-6 Astra.
Switching in Code
Both speak the Anthropic Messages protocol, so swapping is one string:
client = Anthropic() # or gateway base_url
resp = client.messages.create(
model="claude-opus-5", # or "claude-fable-5-1"
max_tokens=8192,
messages=[{"role": "user", "content": "..."}],
)
Effort levels (low → max) apply to Fable 5.1, defaulting to High on the API and Claude Code; if you're on Medium-workload tasks, dropping a level is often cheaper than switching models. Everything else — tools, streaming, caching headers — is identical between the two.
FAQ
Q: Is Opus 5 better than Fable 5.1 for coding? Honest answer: the benchmarks disagree with each other. SWE-bench Verified says Opus 5 by a point (96.0% vs 95.0%); SWE-bench Pro says Fable 5.1 by two (81.2% vs 79.2%); Anthropic's internal numbers say Fable 5.1 solves more real coding problems. Real-world results are close enough that neither is a clear winner — run your own evals on your actual codebase before standardizing on either.
Q: Why would I pay double for Fable 5.1 if Opus 5 is "near-Fable intelligence"? For the tasks at the ceiling. Near-Fable covers most work; the long-task benchmark gap (55.8% vs Opus-class performance) and SWE-bench Pro #1 show up specifically on long, hard, autonomous runs. If Opus 5 finishes your task successfully, it was the right pick — the question is what a failed Opus 5 session costs you in retries.
Q: Does Opus 5 have fast mode? Yes — $10/$50 per million tokens, double the standard $5/$25, for latency-sensitive bursts. Even fast-mode Opus 5 costs the same as standard Fable 5.1.
Q: Which is cheaper for long agent sessions? Less clear-cut than the sticker suggests. Opus 5's input is half price, but Fable 5.1's cache reads are $0.25/M vs Opus-class ~$1.00 — in cache-heavy agent loops, that 4x caching discount claws back much of the difference. Model both with your actual token profile.
Q: How does this compare to subscription access? Fable 5.1 is included in Claude Max plans and premium Team/Enterprise seats (up to half the weekly limit); for API economics and configuring either model in Claude Code, see the Claude Code pricing guide.
Summary
Fable 5.1 vs Opus 5 is ceiling vs value: Fable 5.1 ($10/$50) takes the hardest long-horizon tasks, SWE-bench Pro, and the cheapest caching; Opus 5 ($5/$25) delivers ~48 tok/s and near-flagship intelligence at half the price, with a nominal SWE-bench Verified edge. Default to Opus 5, escalate to Fable 5.1 — and route between them per task.
Get Started
TeamoRouter — one API key at https://api.teamorouter.com/v1, Fable 5.1 and Opus 5 side by side, pay-as-you-go with Alipay/WeChat, so the routing decision happens per task instead of per subscription.