Head-to-head · 2026
Claude Fable 5 vs Claude Opus 4.8
Verdict. Fable 5 takes agentic coding, constraint precision, and hard reasoning — at double the price. Opus 4.8 keeps situational judgment, code-craft quality, and the better $/token for human-read prose. Route by task shape, not by leaderboard.
| Claude Fable 5 | Claude Opus 4.8 | |
|---|---|---|
| Provider | Anthropic | Anthropic |
| Released | 2026-06-09 | 2026-05-28 |
| Context | 1M | 1M |
| Max output | 128K | 128K |
| Input /1M | $10.00 | $5.00 |
| Output /1M | $50.00 | $25.00 |
| Modalities | text, vision, code | text, vision, code |
The analysis
This is the rare comparison with first-party data behind it: we ran four head-to-head eval rounds inside Claude Code within 24 hours of the Fable 5 launch, with published JSON receipts. The split is consistent — Fable 5 was the most constraint-compliant model in every round (7/7 on a script-verified constraint stack Opus failed) and the only one to solve a hard no-tools reasoning task Opus got confidently wrong. Opus 4.8 flagged a governance-gated edit Fable executed silently, pushed back on a contradictory spec, and won the real-world component build on accessibility craft.
On vendor numbers, Fable 5 is the new agentic ceiling: 95.0% SWE-Bench Verified and ~80% SWE-Bench Pro at launch (vendor-claimed) against Opus 4.8’s well-corroborated 88.6% / 69.2%. Anthropic positions the gap as widening with task length — which matches the agentic shape of the launch card.
Pricing is the routing fork: Fable 5 at $10/$50 per million tokens is exactly double Opus 4.8’s unchanged $5/$25 (and equal to Opus fast mode). The 2× pays for itself in agentic pipelines where constraint precision and task length bind; it does not pay for itself in judgment-heavy review or prose — our blind style verdicts flipped between rounds.
Pick Claude Fable 5 if…
- Agentic pipelines feeding schemas, tools, and other agents
- Long-horizon, multi-file coding (the SWE-Bench Pro lead is this shape)
- Strict output contracts where a leaked preamble is a failed tool call
Pick Claude Opus 4.8 if…
- Ambiguous or possibly-wrong specs — it pushes back instead of executing
- Code review and accessibility-critical component work
- Human-read prose and deep single-shot analysis at half the price
Claude Fable 5
Mythos-class made generally available — the new agentic-coding ceiling, at 2× Opus pricing.
Claude Opus 4.8
Modest version bump, real frontier gains — tops the intelligence index at the same price as 4.7.