Claude Sonnet 5 API Pricing: OpenRouter vs OneMux Cost Breakdown

The short answer

If your main decision is token cost, the supplied catalogue makes OneMux the lower-cost route for Claude Sonnet 5: $1.10 per million input tokens and $5.50 per million output tokens, compared with OpenRouter's listed $2.00 and $10.00 rates. Both input and output are 45% lower on the listed OneMux pricing.

That difference matters most for agentic workloads, where a request may repeatedly send large instructions, tool context, files, or conversation history and then generate a substantial response. It matters less to teams whose architecture depends on provider-specific prompt-cache behavior, because the supplied OneMux catalogue does not include cache-read or cache-write rates.

Claude Sonnet 5 pricing at a glance

The following comparison uses the supplied model catalogue and the Claude Sonnet 5 page on OpenRouter. OpenRouter's page summary lists $2.00/M input tokens, $10.00/M output tokens, $0.20/M cache-read tokens, and $2.50/M cache-write tokens.

These are token rates, not a performance benchmark. No independent latency, quality, throughput, or task-accuracy benchmark is provided here, so price should be evaluated alongside your own production measurements.

What the price difference means in real workloads

A simple mixed workload makes the gap easier to budget. Suppose an application processes 1 million input tokens and generates 250,000 output tokens.

• OpenRouter: (1 × $2.00) + (0.25 × $10.00) = $4.50
• OneMux: (1 × $1.10) + (0.25 × $5.50) = $2.475

At that volume, the listed OneMux cost is $2.025 lower. The same 45% reduction applies because both OneMux rates are 55% of the supplied OpenRouter rates.

For a larger monthly workload of 10 million input tokens and 2 million output tokens:

• OpenRouter: (10 × $2.00) + (2 × $10.00) = $40.00
• OneMux: (10 × $1.10) + (2 × $5.50) = $22.00

The difference is $18.00 per workload unit at those volumes. Multiply the calculation by your actual traffic, then include any applicable provider-specific cache treatment, taxes, or account terms that are not specified in the supplied data.

Why output tokens deserve special attention

Claude Sonnet 5's listed output rate is five times its OpenRouter input rate and exactly five times its OneMux input rate. That makes response length a central cost lever for:

• Coding agents: tool results, patches, test output, and explanations can expand the completion.
• Support teams: long, overly detailed answers increase spend across high ticket volumes.
• Marketing workflows: research, drafts, revisions, and channel variations can create large outputs.
• Operators and founders: autonomous planning loops may produce multiple completions per task.

Cost controls should therefore measure input and output separately. Set practical output-token limits, ask for structured responses where appropriate, and track completion length by workflow rather than relying only on an account-wide average. Shorter answers are not automatically better; the objective is to prevent unnecessary generation while preserving the information your application needs.

Cache pricing changes the calculation

The supplied OpenRouter summary distinguishes cache reads from cache writes. Its listed cache-read price is $0.20/M tokens, while cache writes are $2.50/M tokens. Those categories can materially affect the economics of applications that repeatedly reuse a large system prompt, policy bundle, codebase context, or long conversation prefix.

Do not assume that the same cache semantics or rates apply when moving the workload to OneMux. The supplied OneMux model entry lists input and output prices only. Before switching a cache-heavy application, confirm how caching is exposed through the OneMux documentation, whether your integration preserves the relevant behavior, and how those tokens are billed under your account.

This is especially important for international buyers and distributed teams: budget comparisons should use one consistent currency, token unit, and accounting period. The prices above are expressed in U.S. dollars per million tokens because that is how the supplied rates are stated.

Using Claude Sonnet 5 through OneMux

OneMux gives users access to leading AI models through one OpenAI-compatible API. For a team already integrating against an OpenAI-style client, that can make model access easier to centralize: keys, routing, spend visibility, and credit top-ups are handled around a common access layer rather than separate application integrations.

Start with the Claude Sonnet 5 model page on OneMux, then review the OneMux quickstart before changing production traffic. Validate three things in a small controlled rollout:

1. Request compatibility: confirm that your messages, tool calls, files, vision inputs, and response handling work with the model features your application uses.
2. Cost telemetry: record input and output tokens per request and compare the observed mix with your budget model.
3. Operational behavior: test retries, timeouts, streaming, and any cache-dependent workflow under your own traffic pattern.

OneMux's model catalogue describes Claude Sonnet 5 as an everyday Claude agent model for coding, planning, browsing, and general work, with Reasoning, Tools, Files, Vision, and 1M tags. Treat those catalogue labels as capability context, not as a substitute for testing your specific prompts and tools.

Should you choose Claude Sonnet 5 or another model?

Claude Sonnet 5 is a sensible candidate when one model needs to cover general work, coding, planning, browsing, and tool use. But token price alone should not determine every route. OneMux also lists lower-cost options such as DeepSeek V4 Flash at $0.25/M input and $0.50/M output, while higher-priced options include Claude Opus 5 at $2.70/M input and $13.50/M output.

A practical routing policy might reserve Sonnet 5 for tasks that benefit from its stated agent-oriented feature set, use a less expensive model for straightforward classification or extraction, and evaluate a higher-priced model only where your tests show a meaningful quality benefit. Compare complete task cost, including retries and output length, rather than comparing input rates in isolation.

For current account and usage information, consult the OneMux pricing page alongside your measured token consumption.

Conclusion

For the rates supplied here, OneMux is the cheaper path to Claude Sonnet 5 on both input and output tokens: $1.10/M and $5.50/M versus OpenRouter's $2.00/M and $10.00/M. That is a straightforward 45% listed reduction and can produce a meaningful difference in agent, support, coding, and content workflows.

The qualification is cache accounting. OpenRouter's supplied summary includes cache-read and cache-write prices, while the supplied OneMux entry does not. Teams with large reusable prompts should verify cache behavior before treating the headline comparison as a complete cost model. For everyone else, the next step is simple: calculate your input/output mix, test the model through the OneMux Claude Sonnet 5 listing, and monitor spend by workflow.

Sources

• OpenRouter: Claude Sonnet 5 — source for the supplied OpenRouter input, output, cache-read, and cache-write rates.
• OneMux: Claude Sonnet 5 — source for the supplied OneMux model pricing and catalogue context.
• OneMux pricing — account and usage reference.