QUICK VERDICT — JULY 2026
● Better model: Claude Fable 5 — 80.4% SWE-bench Pro vs Opus 4.8's 69.2% — 11.2 percentage point gap
● Better price: Claude Opus 4.8 — $5/$25/M vs Fable 5's $10/$50/M — exactly half the price
● Context window: Both 1M tokens — tied
● In Claude Max ($100/month): Fable 5 permanently included at 50% weekly limits — the plan comparison changes
● The decision: If you are on Claude Max, use Fable 5 — it's already paid for. If on Claude Pro paying credits, the 11.2-point accuracy gap justifies Fable 5 only for hard correctness-critical tasks. For everything else, Opus 4.8 at half price is rational.
Full Comparison Table
| Model |
Input /1M |
Output /1M |
Context |
SWE-bench Pro |
SWE Marathon |
Cost/task (AA) |
| Claude Fable 5 |
$10 |
$50 |
1M |
80.4% #1 |
24.0% |
$11.80 |
| Claude Opus 4.8 |
$5 |
$25 |
1M |
69.2% |
26.0% |
~$7.20 |
Cost per task estimated from Artificial Analysis methodology. Fable 5 confirmed at $11.80/task. Opus 4.8 estimate based on same benchmark methodology and per-token pricing. Both models included in Claude Max at 50% of weekly usage limits.
The 11.2-Point SWE-bench Pro Gap — What It Means in Practice
Fable 5 completes 80.4% of SWE-bench Pro tasks correctly. Opus 4.8 completes 69.2%. For every 100 autonomous coding tasks, Fable 5 produces 11 more correct outputs. The value of those 11 extra correct outputs depends entirely on what happens when a task fails. If a failed coding task requires 30 minutes of developer time at $100/hour to identify, debug, and restart, each failure costs $50. At 100 tasks per month, Opus 4.8's 11 extra failures cost $550 in developer time. At that rate, the price difference to use Fable 5 instead — approximately $460 extra per 100 tasks at standard rates — is worth it. At lower failure costs or higher task volumes where human review is batched, the math shifts in Opus 4.8's favour.
The Subscription Dimension — Claude Max Changes the Calculation
The API-only comparison ignores the subscription context. After Anthropic's July 21 reversal, both Fable 5 and Opus 4.8 are included in Claude Max ($100/month) at 50% of weekly usage limits. If you are a Claude Max subscriber, the Fable 5 vs Opus 4.8 decision is not a cost question — both are covered by your subscription. Use Fable 5 for hard tasks and Opus 4.8 for tasks where its 69.2% accuracy is sufficient, preserving your Fable 5 50% weekly limit allocation for the work that specifically needs it.
Which to Use
Claude Max subscribers: Use Fable 5 for hard correctness-critical tasks (production refactors, security reviews, hard debugging). Use Opus 4.8 for standard coding and analysis to preserve your Fable 5 50% weekly allocation. Both are already in your plan.
API users (credits or direct): Default to Opus 4.8 ($5/$25/M) for standard work. Switch to Fable 5 ($10/$50/M) for tasks where the 11.2-point SWE-bench Pro accuracy gap is worth $5 extra per million tokens — typically production-critical code where incorrect output has real downstream cost.
Also consider: Claude Sonnet 5 ($2/$10/M intro through August 31) sits below both but provides 63.2% SWE-bench Pro with 1M context at the lowest Claude API price. For general-purpose work, Sonnet 5 at $2/$10/M is often the most economical choice in the Claude family until August 31.
Last updated July 21, 2026. Related: Fable 5 permanently returns to Max plans → · Fable 5 vs GPT-5.6 Sol → · Claude Sonnet 5 vs GPT-5.6 Terra →