The Vibe Father
Model Comparison
Every team eventually draws a line in Anthropic's lineup and asks: where does "good enough" stop and "worth paying more" begin? Opus 4.8 versus Sonnet 5 is exactly that line. Opus is the premium builder — near the top of every board we run. Sonnet 5 is the workhorse — cheaper, notably faster, and strong enough that for a lot of real work you genuinely cannot feel the difference. We run both on our live board at /benchmarks, and this comparison is about finding your own value line, not ours.
What each one wins
Opus 4.8 wins on raw capability, especially on hard repository work. It posts 88.6 on SWE-bench Verified against Sonnet 5's 85.2 — a 3.4-point gap that sounds small but lands squarely on the cross-file refactors and subtle bugs where a wrong first attempt costs you real time. Opus also leads on LiveCodeBench, 87.8 to 82.4, a 5.4-point gap that shows up in contest-style and algorithmic problems. When the task is genuinely hard, Opus fails less often, and failing less often is where the money actually is.
Sonnet 5 wins on speed and price, and it wins decisively. It streams at 89 tokens per second against Opus's 60 — roughly 50% faster, which you feel in every interactive session and every fast agent loop. And it costs $3/$15 against Opus's $5/$25, a meaningful discount on both ends. Sonnet's 85.2 SWE-bench is not a weak number; it is a genuinely capable builder that happens to be cheaper and quicker. For a huge slice of everyday work, that combination is the smarter buy.
The numbers side by side
Our Vibe Coding Index weights SWE-bench Verified at 40%, Terminal-Bench and LiveCodeBench at 30% each. Note that Sonnet 5 does not yet have a published Terminal-Bench score on our board — we will not invent one.
| Model | SWE-bench Verified | Terminal-Bench | LiveCodeBench | Price (in/out per M) | Speed (tok/s) |
|---|---|---|---|---|---|
 Claude Opus 4.8 | 88.6 | 78.9 | 87.8 | $5 / $25 | 60 |
| Claude Sonnet 5 | 85.2 | not yet published | 82.4 | $3 / $15 | 89 |
Sonnet 5's Terminal-Bench number is simply not on our board yet, so we leave it blank rather than guess — agentic-shell strength is the one axis where we can't put a firm figure on the gap today. On the two axes we can measure, Opus leads by 3.4 and 5.4 points, and it costs about 67% more per output token while running a third slower.
The price math
Our reference heavy month is 50M input and 10M output tokens. Opus 4.8 runs 50 × $5 + 10 × $25 = $500/month. Sonnet 5 runs 50 × $3 + 10 × $15 = $300/month. That is $200 saved every month, or $2,400 a year, for choosing the workhorse — plus every session finishing faster. For teams whose work is mostly routine, that saving is close to free money. We put the full budget picture in our cheapest coding models guide.
Who should pick which
Pick Opus 4.8 when correctness on hard problems is the constraint. If your work leans toward repo surgery — deep refactors, multi-file changes, the bugs that hide across four files — the 88.6 SWE-bench is worth the premium because Opus lands more of those on the first try, and a first-try win beats three cheaper retries plus your afternoon. It is also the safer pick for contest-style and algorithmic work given the LiveCodeBench lead.
Pick Sonnet 5 when throughput and cost matter more than the last few points of hard-task accuracy — which, honestly, is most of the time. For UI wiring, endpoint scaffolding, test generation, and the steady stream of ordinary implementation tasks, 85.2 is plenty, and the 89 tok/s speed makes it a joy in interactive and fast-loop agent work. If your terminal-heavy agentic work is the priority, the honest note is that we don't have a Sonnet 5 Terminal-Bench figure to weigh yet, so lean on Opus there until one publishes.
The pattern we run in The Vibe Father: Sonnet 5 as the default builder for volume, Opus 4.8 promoted in for the genuinely hard tickets. Run both, let each win the seat it's suited for — that's cheaper and better than forcing one model to do everything. We break the roles down in the best model for each agent role.
Verdict
Opus 4.8 is the better model — 3.4 points on SWE-bench, 5.4 on LiveCodeBench — and if your work is genuinely hard, that gap earns its premium. But Sonnet 5 is where the value line sits for most teams: 85.2 SWE-bench, 89 tok/s, and $200/month cheaper. The right answer for most is "both" — Sonnet builds the volume, Opus handles the hard tickets. Read the full cases in our Opus 4.8 review and Sonnet 5 review, and watch where each lands on the live leaderboard.
