Claude Sonnet 5.5 vs GPT-6 Sol: Which Should You Use?

Specifications at a glance

Dimension	Claude Sonnet 5.5	GPT-6 Sol
Public status	Released September 28, 2026; Anthropic ID claude-sonnet-5-5, APIMaster ID claude-sonnet-5.5	Available as gpt-6-sol
Context window	1,000,000 tokens	1,050,000 tokens; maximum input 922,000
Maximum output	128,000 tokens in the OpenRouter provider listing	128,000 tokens
Standard input / output	$2 / $10 per 1M tokens	$2 / $10 per 1M tokens up to 272K input
Cache read	$0.20 per 1M tokens	$0.20 per 1M cached input tokens
Cache write	$2.50 per 1M tokens	1.25x normal uncached input
Thinking	Effort control; Medium default in apps and Claude Code, High on Claude Platform	none, low, medium (default), high, xhigh, max
Best fit	Claude-native coding, agents and knowledge work	Controllable coding and agent pipelines available through APIMaster now

The matching headline rates do not imply matching bills. Long-context multipliers, cache writes, reasoning tokens, tool calls, retries and task completion quality all affect cost per accepted result.

Context, output and thinking controls

Both models can work with a large repository or multi-document corpus and produce long outputs. Sonnet 5.5's official product page advertises a 1M context window; OpenRouter lists 128K maximum output. Sol's 1.05M context includes a 922K maximum input, so the advertised window is not entirely available for source material.

Sol also has a 272K-input billing threshold. Above it, OpenAI charges 2x input and cache rates and 1.5x output for the entire request. That makes prompt length a first-class budget control.

Sonnet 5.5 uses effort to balance speed, token use and checking depth. Anthropic sets Medium in Claude apps and Claude Code and High on the Claude Platform. Integrations that previously disabled thinking must migrate to between_tools, which keeps up-front thinking off but permits thinking between tool calls. Sol's six explicit levels make it easier to route routine edits at none or low and reserve max for genuinely hard work.

Coding: speed versus explicit control

Anthropic says Sonnet 5.5 generates output 30%+ faster than Sonnet 5 and costs up to 30% less per typical task because it uses fewer tokens. Its coding positioning emphasizes quickly understanding a codebase, scoping changes and keeping edits reviewable. For Claude Code users, that makes it the natural direct upgrade from Sonnet 5.

GPT-6 Sol is easier to operationalize on APIMaster today. Its model ID is routable, its reasoning budget is explicit, and teams can select among 12 active routes. Use lower effort for routine transformations and raise it only after tests or review show that a task needs more reasoning. For tool-heavy Sol tasks, prefer the Responses API; Chat Completions function calling is limited to reasoning_effort=none.

Neither provider's benchmark establishes a universal coding winner. Hold the repository snapshot, prompt, tools, tests and effort budget constant. Measure merged or accepted changes, not code volume.

Agent execution and long-horizon work

Sonnet 5.5 is designed for well-defined agent tasks such as investigation, review and drafting. Anthropic describes it as its strongest Sonnet on long-horizon work, while positioning Opus 5.5 as the higher tier for tasks that need deeper deliberation.

Sol is suited to pipelines that need predictable escalation. A router can start at low, retry at medium, and send only unresolved work to high, xhigh or max. That approach makes reasoning spend visible, but it introduces orchestration logic that Sonnet's product defaults handle differently.

The important metrics are accepted tasks per dollar and time to accepted result. Include retries, tool failures, cache behavior and human review. A faster first response is not a win if the agent needs another run.

Cache economics

Both models list $0.20 / 1M token cache reads, one tenth of their $2 uncached input rate. Sonnet 5.5 cache writes cost $2.50 / 1M tokens. Sol cache writes cost 1.25x normal uncached input before any long-context multiplier.

Caching only saves money when the request preserves a stable prefix and the provider reports a hit. Record cache writes and reads separately. For Sonnet 5.5, Anthropic also advertises up to 50% savings from batch processing; for Sol, account for its long-prompt pricing threshold before comparing total cost.

Which one should you choose?

If you need…	Start with…	Why
Claude Code and Claude-native behavior	Claude Sonnet 5.5	Direct Sonnet upgrade with official ecosystem support
A production APIMaster route today	GPT-6 Sol	12 active routes and live discounted pricing
Explicit per-request reasoning budgets	GPT-6 Sol	Six effort levels from none to max
Fast everyday coding and well-scoped agents	Claude Sonnet 5.5	Anthropic's main Sonnet 5.5 positioning
The hardest Claude or GPT-6 tasks	Claude Opus 5.5 or GPT-6 Astra	Both are higher tiers than the models compared here

If you choose a third-party Sonnet route, read how to verify a real Claude Sonnet 5.5 API. APIMaster's fingerprint tester now supports Sonnet 5.5; a matching response model string alone is not independent identity evidence.

FAQ

Is Claude Sonnet 5.5 released?

Yes. Anthropic released it on September 28, 2026 with the API model ID claude-sonnet-5-5.

Is Claude Sonnet 5.5 cheaper than GPT-6 Sol?

Their standard token rates are both $2 input / $10 output per 1M tokens. Sonnet 5.5 may use fewer tokens for some tasks, while Sol's current APIMaster routes start at $0.1071 / $0.5353. Compare total cost per accepted task.

Can I call Sonnet 5.5 on APIMaster today?

Yes. APIMaster listed eight active claude-sonnet-5.5 routes on September 29, 2026 at $0.6691 / $3.34548 per 1M input/output tokens. Use the exact ID shown on the live card.

Do both support million-token context and 128K output?

Yes at the catalog level: Sonnet 5.5 has 1M context and a provider-listed 128K output maximum; Sol has 1.05M context, 922K maximum input and 128K output. Confirm the exact limits on the selected route.

Which is better for coding agents?

Choose Sonnet 5.5 for Claude-native workflows and Sol for explicit reasoning budgets. Both are callable through APIMaster now; Sonnet 5.5 uses the APIMaster ID claude-sonnet-5.5. Benchmark both with the same tools and acceptance tests before deciding.

Sources and check date

Checked September 29, 2026.

• Anthropic: Introducing Claude Sonnet 5.5 and Claude Sonnet product page — release, pricing, 1M context, effort defaults, coding and agent positioning.
• Anthropic Sonnet 5.5 migration guide — between_tools migration behavior.
• OpenRouter Claude Sonnet 5.5 catalog — 128K maximum output and modalities.
• OpenAI GPT-6 Sol model page and pricing — limits, effort settings and long-context billing.
• APIMaster live marketplace data checked September 29, 2026 — 12 Sol routes from $0.1071 / $0.5353 and eight claude-sonnet-5.5 routes at $0.6691 / $3.34548. Live cards take precedence.

Start with a working API

Create an APIMaster account → create an API key → send requests to https://apimaster.ai/v1. Use gpt-6-sol or claude-sonnet-5.5 now, and open the live Sonnet 5.5 card before routing production traffic.