Both are Anthropic models. Claude Opus 5.5 is the newer, generally stronger default; reach for Claude Sonnet 4.6 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Claude Opus 5.5 and Claude Sonnet 4.6 are both Anthropic models, so the real question is not which lab to trust but which tier fits your workload and budget. Claude Opus 5.5 is anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching. Claude Sonnet 4.6 is opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). 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 4.6 is about 1.3× cheaper on input ($3/$15 per 1M tokens vs $4/$20 per 1M tokens) — modest, but it adds up at steady volume.
Context window: both advertise 1M tokens (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
Recency: Claude Opus 5.5 is the newer model by about 7 months (released September 22, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Opus 5.5
Claude Sonnet 4.6
Provider
Anthropic (US)
Anthropic (US)
Released
September 22, 2026
February 17, 2026
Context window
1M tokens (~1,500 pages)
1M (~1,500 pages)
Price (in/out)
$4/$20 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
79.6%
MRCR v2 @ 1M
Not published
Not published
Who wins what
Performs at roughly Claude Fable 5.1's level on most work, at 40% lower typical workload cost than Opus 5: Claude Opus 5.5 — Anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching — and it is the newer of the two.
Anthropic reports it surpasses Fable 5.1 on agentic coding, knowledge work, computer use, visual chart recognition, and multidisciplinary reasoning: Claude Opus 5.5 — Claude Sonnet 4.6 is comparatively weak here — trails Opus on the hardest agentic tasks
Pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok: Claude Opus 5.5 — Claude Opus 5.5 lists pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok among its strengths; Claude Sonnet 4.6 does not.
Best value in the Claude family: Claude Sonnet 4.6 — At $3/$15 per 1M tokens it undercuts Claude Opus 5.5 ($4/$20 per 1M tokens), and that gap compounds at volume.
Everyday professional work: Claude Sonnet 4.6 — Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026) — and it runs cheaper at $3/$15 per 1M tokens.
Long-document analysis: Claude Sonnet 4.6 — Claude Sonnet 4.6 lists long-document analysis among its strengths; Claude Opus 5.5 does not.
Lowest cost at scale: Claude Sonnet 4.6 — At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume: Claude Sonnet 4.6 — At $3/$15 per 1M tokens it undercuts Claude Opus 5.5, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is performs at roughly claude fable 5.1's level on most work, at 40% lower typical workload cost than opus 5: Claude Opus 5.5 — It is specifically built for that.
Anyone whose priority is best value in the claude family: Claude Sonnet 4.6 — That is its strongest area.
Claude Opus 5.5: where it fits
Anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching. Released September 22, 2026 by Anthropic, it is built for performs at roughly Claude Fable 5.1's level on most work, at 40% lower typical workload cost than Opus 5, anthropic reports it surpasses Fable 5.1 on agentic coding, knowledge work, computer use, visual chart recognition, and multidisciplinary reasoning, pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok, and output speed increased over 30% versus Opus 5.
Its trade-offs are real: not a reasoning-ceiling upgrade over Fable 5.1 — pitched as matching its performance at lower cost, not beating it outright, like Opus 5, the headline 1M-token context is not uniformly available across every platform and plan — some API paths default to a smaller window, and first model in the 5.5 line; Anthropic has signaled Sonnet 5.5 and Haiku 5.5 are still weeks away, so the lower tiers of the family aren't out yet. At $4 in / $20 out per million tokens, it sits in the mid price band.
Claude Sonnet 4.6: where it fits
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Released February 17, 2026 by Anthropic, it is built for best value in the Claude family, everyday professional work, long-document analysis, and coding at lower cost than Opus.
Its trade-offs: trails Opus on the hardest agentic tasks, and not an open-weight option. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Because Claude Opus 5.5 and Claude Sonnet 4.6 come from the same lab (Anthropic), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Claude Opus 5.5 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 Opus 5.5 and drop down only with a concrete reason.
Frequently asked questions
Is Claude Opus 5.5 or Claude Sonnet 4.6 better for coding?
Public SWE-Bench figures are not available for Claude Opus 5.5, so the honest test is your own repository — run an identical real bug through both. By design, Claude Opus 5.5 leans toward performs at roughly claude fable 5.1's level on most work, at 40% lower typical workload cost than opus 5 while Claude Sonnet 4.6 leans toward best value in the claude family, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Opus 5.5 or Claude Sonnet 4.6?
Claude Sonnet 4.6 is cheaper — $4/$20 per 1M tokens vs $3/$15 per 1M tokens, roughly 1.3× apart on input.
Which has the bigger context window?
Both advertise 1M tokens (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Should I upgrade from Claude Sonnet 4.6 to Claude Opus 5.5?
Since both are Anthropic models, the newer one (Claude Opus 5.5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Claude Opus 5.5 or Claude Sonnet 4.6?
Claude Opus 5.5 — released September 22, 2026, about 7 months after Claude Sonnet 4.6.
Claude Opus 5.5 vs Claude Sonnet 4.6
Anthropic · US | Anthropic · US · Updated June 2026
Quick verdict
Both are Anthropic models. Claude Opus 5.5 is the newer, generally stronger default; reach for Claude Sonnet 4.6 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Claude Opus 5.5 and Claude Sonnet 4.6 are both Anthropic models, so the real question is not which lab to trust but which tier fits your workload and budget. Claude Opus 5.5 is anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching. Claude Sonnet 4.6 is opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). 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 4.6 is about 1.3× cheaper on input ($3/$15 per 1M tokens vs $4/$20 per 1M tokens) — modest, but it adds up at steady volume.
▸Context window: both advertise 1M tokens (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
▸Recency: Claude Opus 5.5 is the newer model by about 7 months (released September 22, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Opus 5.5
Claude Sonnet 4.6
Provider
Anthropic (US)
Anthropic (US)
Released
September 22, 2026
February 17, 2026
Context window
1M tokens (~1,500 pages)
1M (~1,500 pages)
Price (in/out)
$4/$20 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
79.6%
MRCR v2 @ 1M
Not published
Not published
Who wins what
Performs at roughly Claude Fable 5.1's level on most work, at 40% lower typical workload cost than Opus 5
Claude Opus 5.5
Anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching — and it is the newer of the two.
Anthropic reports it surpasses Fable 5.1 on agentic coding, knowledge work, computer use, visual chart recognition, and multidisciplinary reasoning
Claude Opus 5.5
Claude Sonnet 4.6 is comparatively weak here — trails Opus on the hardest agentic tasks
Pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok
Claude Opus 5.5
Claude Opus 5.5 lists pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok among its strengths; Claude Sonnet 4.6 does not.
Best value in the Claude family
Claude Sonnet 4.6
At $3/$15 per 1M tokens it undercuts Claude Opus 5.5 ($4/$20 per 1M tokens), and that gap compounds at volume.
Everyday professional work
Claude Sonnet 4.6
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026) — and it runs cheaper at $3/$15 per 1M tokens.
Long-document analysis
Claude Sonnet 4.6
Claude Sonnet 4.6 lists long-document analysis among its strengths; Claude Opus 5.5 does not.
Lowest cost at scale
Claude Sonnet 4.6
At $3/$15 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Claude Sonnet 4.6
At $3/$15 per 1M tokens it undercuts Claude Opus 5.5, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is performs at roughly claude fable 5.1's level on most work, at 40% lower typical workload cost than opus 5
→ Claude Opus 5.5
It is specifically built for that.
Anyone whose priority is best value in the claude family
→ Claude Sonnet 4.6
That is its strongest area.
Claude Opus 5.5: where it fits
Anthropic's September 22, 2026 update: Fable 5.1-level performance at 40% lower cost than Opus 5, with faster output and cheaper caching. Released September 22, 2026 by Anthropic, it is built for performs at roughly Claude Fable 5.1's level on most work, at 40% lower typical workload cost than Opus 5, anthropic reports it surpasses Fable 5.1 on agentic coding, knowledge work, computer use, visual chart recognition, and multidisciplinary reasoning, pricing cut to $4/$20 per million tokens (20% below Opus 5's $5/$25), cache reads down 60% to $0.20/MTok, and output speed increased over 30% versus Opus 5.
Its trade-offs are real: not a reasoning-ceiling upgrade over Fable 5.1 — pitched as matching its performance at lower cost, not beating it outright, like Opus 5, the headline 1M-token context is not uniformly available across every platform and plan — some API paths default to a smaller window, and first model in the 5.5 line; Anthropic has signaled Sonnet 5.5 and Haiku 5.5 are still weeks away, so the lower tiers of the family aren't out yet. At $4 in / $20 out per million tokens, it sits in the mid price band.
Claude Sonnet 4.6: where it fits
Opus-class quality at lower cost; superseded as the default Sonnet by Claude Sonnet 5 (June 2026). Released February 17, 2026 by Anthropic, it is built for best value in the Claude family, everyday professional work, long-document analysis, and coding at lower cost than Opus.
Its trade-offs: trails Opus on the hardest agentic tasks, and not an open-weight option. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
Because Claude Opus 5.5 and Claude Sonnet 4.6 come from the same lab (Anthropic), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Claude Opus 5.5 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 Opus 5.5 and drop down only with a concrete reason.
Want both Claude Opus 5.5 and Claude Sonnet 4.6 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 Opus 5.5 or Claude Sonnet 4.6 better for coding?
Public SWE-Bench figures are not available for Claude Opus 5.5, so the honest test is your own repository — run an identical real bug through both. By design, Claude Opus 5.5 leans toward performs at roughly claude fable 5.1's level on most work, at 40% lower typical workload cost than opus 5 while Claude Sonnet 4.6 leans toward best value in the claude family, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Opus 5.5 or Claude Sonnet 4.6?
Claude Sonnet 4.6 is cheaper — $4/$20 per 1M tokens vs $3/$15 per 1M tokens, roughly 1.3× apart on input.
Which has the bigger context window?
Both advertise 1M tokens (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Should I upgrade from Claude Sonnet 4.6 to Claude Opus 5.5?
Since both are Anthropic models, the newer one (Claude Opus 5.5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Claude Opus 5.5 or Claude Sonnet 4.6?
Claude Opus 5.5 — released September 22, 2026, about 7 months after Claude Sonnet 4.6.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.