{"slug": "claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents", "title": "Claude Opus 5.5 vs GPT-6.1 Sol for coding agents", "summary": "A QuickSilver Pro benchmark comparing Claude Opus 5.5 and GPT-6.1 Sol in the OpenCode coding agent found both models passed every hidden test across six real coding tasks and 24 total runs, with no quality difference detected. Opus 5.5 finished tasks in 82 seconds on average versus 152 seconds for GPT-6.1 Sol, while per-task costs were nearly identical at $0.094 and $0.098 respectively. The faster times were attributed to Opus needing fewer requests per task (7.9 versus 12.1) and quicker individual requests.", "body_md": "*Originally published on the [QuickSilver Pro blog](https://quicksilverpro.io/blog/opus-5-5-vs-gpt-6-1-sol-coding/?utm_source=devto&utm_medium=referral&utm_campaign=opus-vs-gpt-sol).*\n\nOn QuickSilver Pro, Claude Opus 5.5 costs $1.00 / $5.00 per million tokens and GPT-6.1 Sol costs $2.00 / $10.00. Both are sold for agentic coding, so for anyone running a coding agent the question is which one gets the work done, how fast, and for how much.\n\nWe tested this on 2026-10-27. Both models ran in the same agent, OpenCode, on six small but real coding tasks, and we graded every run with tests the agent never saw. Short answer: both models passed every hidden test in every run. Opus finished a task in 82 seconds on average and Sol in 152. Per task they cost about the same: $0.094 for Opus and $0.098 for Sol.\n\n`opencode run --auto`), with QuickSilver Pro added as an OpenAI-compatible provider. The only thing that changed between runs was `-m quicksilverpro/claude-opus-5-5` or `-m quicksilverpro/gpt-6.1-sol`. We could not use Claude Code here. QuickSilver Pro serves GPT-6.1 Sol only on the OpenAI-compatible endpoints (`/v1/chat/completions` and `/v1/responses`), and Claude Code needs the Anthropic Messages API, so we used one agent that can drive both models.`edit` / `write` tools. With Sol it used a 5,100-character prompt and an `apply_patch` tool. Each model therefore ran the way OpenCode normally drives it.\nThe tasks:\n\n`\"1h30m\"`, `\"2 hours and 5 min\"`, `\"PT1H30M\"`) with a page of rules on separators, unit order and what must be rejected, including non-ASCII digits. 84 hidden tests.`${section.key}` references with cycle detection. 57 hidden tests.\nAverages over two runs per model and task. Cost is per run, at QuickSilver Pro prices on 2026-10-27.\n\n| Task | Opus 5.5: tests passed | Opus 5.5: time | Opus 5.5: cost | GPT-6.1 Sol: tests passed | GPT-6.1 Sol: time | GPT-6.1 Sol: cost | \n|---|---|---|---|---|---|---|\n| 1. Two-file bug fix | 18/18, both runs | 34 s | $0.049 | 18/18, both runs | 137 s | $0.066 | \n| 2. Duration parser | 84/84, both runs | 53 s | $0.063 | 84/84, both runs | 102 s | $0.080 | \n| 3. Refactor | 317/317, both runs | 85 s | $0.091 | 317/317, both runs | 148 s | $0.106 | \n| 4. Input validation | 84/84, both runs | 65 s | $0.075 | 84/84, both runs | 142 s | $0.085 | \n| 5. Config parser | 57/57, both runs | 116 s | $0.132 | 57/57, both runs | 177 s | $0.106 | \n| 6. Mustache renderer | 136/136, both runs | 139 s | $0.155 | 136/136, both runs | 205 s | $0.148 | \n| **Average** | **all passed** | **82 s** | **$0.094** | **all passed** | **152 s** | **$0.098** | \n\nWhere the tokens and the money went, averaged over all 12 runs per model:\n\n| Per run | Opus 5.5 | GPT-6.1 Sol | \n|---|---|---|\n| Requests (including one short title request from OpenCode) | 7.9 | 12.1 | \n| Input tokens | 107,000 | 101,000 | \n| ...of which read from the prompt cache | 54,000 (51%) | 82,000 (81%) | \n| Output tokens | 7,800 | 4,200 | \n| ...of which reasoning | 0 | 700 | \n| Cost of uncached input | $0.052 | $0.049 | \n| Cost of cached input | $0.003 | $0.008 | \n| Cost of output | $0.039 | $0.042 | \n| **Total cost per task** | **$0.094** | **$0.098** | \n\nSol's uncached-input line includes cache writes: QuickSilver Pro billed some of Sol's uncached input at the cache-write rate rather than the plain input rate. Opus's uncached input was billed at the plain input rate.\n\n**Quality was a tie.** Neither model failed a hidden test in 24 runs. That includes all 136 cases of the official Mustache suite and the 316 comparisons with the original function in the refactor. These tasks did not find a ceiling for either model.\n\n**Opus was faster on every task.** On average Sol took 1.9 times as long, from 1.5 times as long on the Mustache renderer to 4 times as long on the bug fix. Two things account for it. Opus used fewer requests per task (7.9 against 12.1), so it made fewer round trips. Its requests were also quicker, with a median of 7.6 seconds per request against 11.7 for Sol. Sol also split its work into more small steps. Over 12 runs it made 54 calls to OpenCode's file-read tool and 43 to-do-list updates. Opus made 6 and none.\n\n**The cost came out even, for two different reasons.** Opus has the lower per-token prices, but it wrote almost twice as much output (7,800 tokens per task against 4,200). It also got less of its input from the prompt cache. On every Opus request the cache covered the same 8,028 tokens, about the size of OpenCode's system prompt and tool definitions. The rest of the conversation was billed at the full input rate each time. Sol's cache hits grew with the conversation and covered 81% of its input. Sol was cheaper on the two longest tasks, the config parser and the Mustache renderer. Opus was cheaper on the other four.\n\n**Both checked their own work the same way.** In both refactor runs, each model saved a copy of the original function and wrote a throwaway script that compared old and new output on random inputs. On the Mustache task, both models downloaded the official spec test files from GitHub in both runs and ran them before finishing: Opus with `curl`, Sol with OpenCode's web-fetch tool and a Python one-liner. Our hidden tests for that task are the same files, so neither model's Mustache score is independent of what it downloaded.\n\n**Opus 5.5** is the better default for interactive work on tasks like these. You wait about half as long for the same result, at the same price per task.\n\n**GPT-6.1 Sol** is just as good at these tasks and was the cheaper of the two on the two longest ones. If your agent runs unattended and wall time matters less than the bill, the two are close enough that your own workload should decide. We did not find a task in this set that either model failed, so we cannot tell you which one solves more on harder work.\n\nBoth models are on the same QuickSilver Pro key and balance, so trying the other one is a change of `-m`.\n\nThe OpenCode config we used, pointed at the public endpoint. Save it as `opencode.json` in your project:\n\n```\n{\n  \"$schema\": \"https://opencode.ai/config.json\",\n  \"provider\": {\n    \"quicksilverpro\": {\n      \"npm\": \"@ai-sdk/openai-compatible\",\n      \"name\": \"QuickSilver Pro\",\n      \"options\": {\n        \"baseURL\": \"https://api.quicksilverpro.io/v1\",\n        \"apiKey\": \"{env:QSP_API_KEY}\"\n      },\n      \"models\": {\n        \"claude-opus-5-5\": { \"name\": \"Claude Opus 5.5\", \"limit\": { \"context\": 1000000, \"output\": 64000 } },\n        \"gpt-6.1-sol\": { \"name\": \"GPT-6.1 Sol\", \"limit\": { \"context\": 1000000, \"output\": 64000 } }\n      }\n    }\n  }\n}\n```\n\nThen run the same prompt with each model:\n\n```\nexport QSP_API_KEY=YOUR_QSP_KEY\n\nopencode run --auto -m quicksilverpro/claude-opus-5-5 \"Fix the failing test in tests/\"\nopencode run --auto -m quicksilverpro/gpt-6.1-sol \"Fix the failing test in tests/\"\n```\n\n`--auto` approves the agent's file edits and shell commands without asking, so use it only in a project you can reset. OpenCode shows a cost of 0 for a custom provider. The real cost of each request, with its model and token counts, is in your QuickSilver Pro dashboard. For more on the setup, see [Use QuickSilver Pro in OpenCode and Crush](https://quicksilverpro.io/blog/opencode-crush-quicksilver-pro/?utm_source=devto&utm_medium=referral&utm_campaign=opus-vs-gpt-sol). For the same six-task method with Claude Code, see [Claude Opus 5.5 vs Sonnet 5.5 for coding agents](https://quicksilverpro.io/blog/claude-opus-5-5-vs-sonnet-5-5-coding/?utm_source=devto&utm_medium=referral&utm_campaign=opus-vs-gpt-sol). [Claude Opus 5.5](https://quicksilverpro.io/models/claude-opus-5-5/?utm_source=devto&utm_medium=referral&utm_campaign=opus-vs-gpt-sol) is 75% below Anthropic's list price of $4.00 / $20.00.", "url": "https://wpnews.pro/news/claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents", "canonical_source": "https://dev.to/xiun_xiao_6eae2df5c108c5f/claude-opus-55-vs-gpt-61-sol-for-coding-agents-310p", "published_at": "2026-11-09 01:11:48+00:00", "updated_at": "2026-11-09 02:03:04.067074+00:00", "lang": "en", "topics": ["large-language-models", "ai-agents", "ai-tools", "ai-products"], "entities": ["QuickSilver Pro", "Claude Opus 5.5", "GPT-6.1 Sol", "OpenCode", "Anthropic", "OpenAI"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents", "markdown": "https://wpnews.pro/news/claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents.md", "text": "https://wpnews.pro/news/claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents.txt", "jsonld": "https://wpnews.pro/news/claude-opus-5-5-vs-gpt-6-1-sol-for-coding-agents.jsonld"}}