Both are Anthropic models. Claude Fable 5 is the newer, generally stronger default; reach for Claude Sonnet 4.5 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Claude Fable 5 and Claude Sonnet 4.5 are both Anthropic models, so the real question is not which lab to trust but which tier fits your workload and budget. Claude Fable 5 is anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. Claude Sonnet 4.5 is september 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences
Price: Claude Sonnet 4.5 is about 3.3× cheaper on input ($3/$15 per 1M tokens vs $10/$50 per 1M tokens) — meaningful once you are processing millions of tokens a month.
Context window: Claude Fable 5 holds 5× more — 1M (~1,500 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: Claude Fable 5 is the newer model by about 8 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Fable 5
Claude Sonnet 4.5
Provider
Anthropic (US)
Anthropic (US)
Released
June 9, 2026
September 29, 2025
Context window
1M (~1,500 pages)
200K (~300 pages)
Price (in/out)
$10/$50 per 1M tokens
$3/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
Not published
77.2%
MRCR v2 @ 1M
Not published
Not published
Who wins what
The hardest reasoning and most complex problems: Claude Fable 5 — Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive — and it carries the larger 1M context.
Long-horizon, multi-step agentic work: Claude Fable 5 — Its 1M window holds about 5× more than Claude Sonnet 4.5's 200K in a single prompt.
Frontier-level analysis and research: Claude Fable 5 — Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive — and it is the newer of the two.
Agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch: Claude Sonnet 4.5 — September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded — and it runs cheaper at $3/$15 per 1M tokens.
Computer use and GUI automation (61.4% OSWorld at launch): Claude Sonnet 4.5 — Claude Sonnet 4.5 lists computer use and GUI automation (61.4% OSWorld at launch) among its strengths; Claude Fable 5 does not.
Long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks: Claude Sonnet 4.5 — Claude Sonnet 4.5 lists long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks among its strengths; Claude Fable 5 does not.
Lowest cost at scale: Claude Sonnet 4.5 — At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: Claude Fable 5 — Its 1M window is about 5× larger than Claude Sonnet 4.5's 200K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: Claude Sonnet 4.5 — At $3/$15 per 1M tokens it undercuts Claude Fable 5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Claude Fable 5 — Larger 1M window fits more in one prompt.
Anyone whose priority is the hardest reasoning and most complex problems: Claude Fable 5 — It is specifically built for that.
Anyone whose priority is agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch: Claude Sonnet 4.5 — That is its strongest area.
Claude Fable 5: where it fits
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. Released June 9, 2026 by Anthropic, it is built for the hardest reasoning and most complex problems, long-horizon, multi-step agentic work, frontier-level analysis and research, and work where maximum capability outweighs cost.
Its trade-offs are real: highest price in the Claude lineup, and tier access was temporarily suspended in June 2026 under a US export-control directive. At $10 in / $50 out per million tokens, it sits in the premium price band.
Claude Sonnet 4.5: where it fits
September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Released September 29, 2025 by Anthropic, it is built for agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch, computer use and GUI automation (61.4% OSWorld at launch), long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks, and tracking its own remaining token budget natively, which few models do.
Its trade-offs: superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price, capped at 200K since Anthropic retired its 1M beta in April 2026, while its successors ship 1M as standard, and missing the modern API surface: no adaptive thinking, no effort control, and half the max output of newer Sonnets. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Because Claude Fable 5 and Claude Sonnet 4.5 come from the same lab (Anthropic), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Claude Fable 5 is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to Claude Fable 5 and drop down only with a concrete reason.
Frequently asked questions
Is Claude Fable 5 or Claude Sonnet 4.5 better for coding?
Public SWE-Bench figures are not available for Claude Fable 5, so the honest test is your own repository — run an identical real bug through both. By design, Claude Fable 5 leans toward the hardest reasoning and most complex problems while Claude Sonnet 4.5 leans toward agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or Claude Sonnet 4.5?
Claude Sonnet 4.5 is cheaper — $10/$50 per 1M tokens vs $3/$15 per 1M tokens, roughly 3.3× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 200K, about 5× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from Claude Sonnet 4.5 to Claude Fable 5?
Since both are Anthropic models, the newer one (Claude Fable 5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Claude Fable 5 or Claude Sonnet 4.5?
Claude Fable 5 — released June 9, 2026, about 8 months after Claude Sonnet 4.5.
Claude Fable 5 vs Claude Sonnet 4.5
Anthropic · US | Anthropic · US · Updated June 2026
Quick verdict
Both are Anthropic models. Claude Fable 5 is the newer, generally stronger default; reach for Claude Sonnet 4.5 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Claude Fable 5 and Claude Sonnet 4.5 are both Anthropic models, so the real question is not which lab to trust but which tier fits your workload and budget. Claude Fable 5 is anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. Claude Sonnet 4.5 is september 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences at a glance
▸Price: Claude Sonnet 4.5 is about 3.3× cheaper on input ($3/$15 per 1M tokens vs $10/$50 per 1M tokens) — meaningful once you are processing millions of tokens a month.
▸Context window: Claude Fable 5 holds 5× more — 1M (~1,500 pages) vs 200K (~300 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: Claude Fable 5 is the newer model by about 8 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Fable 5
Claude Sonnet 4.5
Provider
Anthropic (US)
Anthropic (US)
Released
June 9, 2026
September 29, 2025
Context window
1M (~1,500 pages)
200K (~300 pages)
Price (in/out)
$10/$50 per 1M tokens
$3/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
Not published
77.2%
MRCR v2 @ 1M
Not published
Not published
Who wins what
The hardest reasoning and most complex problems
Claude Fable 5
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive — and it carries the larger 1M context.
Long-horizon, multi-step agentic work
Claude Fable 5
Its 1M window holds about 5× more than Claude Sonnet 4.5's 200K in a single prompt.
Frontier-level analysis and research
Claude Fable 5
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive — and it is the newer of the two.
Agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch
Claude Sonnet 4.5
September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded — and it runs cheaper at $3/$15 per 1M tokens.
Computer use and GUI automation (61.4% OSWorld at launch)
Claude Sonnet 4.5
Claude Sonnet 4.5 lists computer use and GUI automation (61.4% OSWorld at launch) among its strengths; Claude Fable 5 does not.
Long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks
Claude Sonnet 4.5
Claude Sonnet 4.5 lists long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks among its strengths; Claude Fable 5 does not.
Lowest cost at scale
Claude Sonnet 4.5
At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
Claude Fable 5
Its 1M window is about 5× larger than Claude Sonnet 4.5's 200K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Claude Sonnet 4.5
At $3/$15 per 1M tokens it undercuts Claude Fable 5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Claude Fable 5
Larger 1M window fits more in one prompt.
Anyone whose priority is the hardest reasoning and most complex problems
→ Claude Fable 5
It is specifically built for that.
Anyone whose priority is agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch
→ Claude Sonnet 4.5
That is its strongest area.
Claude Fable 5: where it fits
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. Released June 9, 2026 by Anthropic, it is built for the hardest reasoning and most complex problems, long-horizon, multi-step agentic work, frontier-level analysis and research, and work where maximum capability outweighs cost.
Its trade-offs are real: highest price in the Claude lineup, and tier access was temporarily suspended in June 2026 under a US export-control directive. At $10 in / $50 out per million tokens, it sits in the premium price band.
Claude Sonnet 4.5: where it fits
September 2025's coding state of the art at $3/$15 — still supported, but 200K-capped and twice superseded. Released September 29, 2025 by Anthropic, it is built for agentic coding — 77.2% on SWE-Bench Verified, the best score any model had posted at its launch, computer use and GUI automation (61.4% OSWorld at launch), long-horizon autonomy — Anthropic reported 30+ hours of sustained focus on multi-step tasks, and tracking its own remaining token budget natively, which few models do.
Its trade-offs: superseded twice — Sonnet 4.6 and Sonnet 5 match or beat it at the same or lower price, capped at 200K since Anthropic retired its 1M beta in April 2026, while its successors ship 1M as standard, and missing the modern API surface: no adaptive thinking, no effort control, and half the max output of newer Sonnets. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Because Claude Fable 5 and Claude Sonnet 4.5 come from the same lab (Anthropic), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Claude Fable 5 is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to Claude Fable 5 and drop down only with a concrete reason.
Want both Claude Fable 5 and Claude Sonnet 4.5 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is Claude Fable 5 or Claude Sonnet 4.5 better for coding?
Public SWE-Bench figures are not available for Claude Fable 5, so the honest test is your own repository — run an identical real bug through both. By design, Claude Fable 5 leans toward the hardest reasoning and most complex problems while Claude Sonnet 4.5 leans toward agentic coding — 77.2% on swe-bench verified, the best score any model had posted at its launch, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or Claude Sonnet 4.5?
Claude Sonnet 4.5 is cheaper — $10/$50 per 1M tokens vs $3/$15 per 1M tokens, roughly 3.3× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 200K, about 5× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from Claude Sonnet 4.5 to Claude Fable 5?
Since both are Anthropic models, the newer one (Claude Fable 5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Claude Fable 5 or Claude Sonnet 4.5?
Claude Fable 5 — released June 9, 2026, about 8 months after Claude Sonnet 4.5.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.