GPT-5.5 vs Claude Opus 4.8: The $5 Workhorse Head-to-Head

Last updated: June 11, 2026

When Anthropic shipped Claude Fable 5 at $10 input / $50 output per million tokens, the flagship pricing conversation moved up a tier - and quietly left a more interesting fight behind. GPT-5.5 and Claude Opus 4.8 now sit at exactly the same input price: $5.00 per million tokens (verified June 11, 2026 on OpenAI's pricing page and Anthropic's pricing page). These are the models most teams will actually run all day. We covered the flagship matchup in our Fable 5 vs GPT-5.5 benchmark comparison - this post is about the workhorse tier, where the prices finally meet and the decision gets genuinely close. Every number below was checked against the live source pages on June 11, 2026.

Why the Workhorse Tier Is the Real Fight

A quick framing note, because the naming is confusing. GPT-5.5 is OpenAI's mainline frontier model - the model page calls it "a new class of intelligence for coding and professional work," with GPT-5.5-pro above it at $30/$180. Claude Opus 4.8 is Anthropic's mainline Opus model, with Fable 5 above it at $10/$50.

Both vendors now run a two-tier structure: an expensive ceiling model and a $5-input workhorse. Anthropic's own models overview tells developers who are unsure which model to pick to "consider starting with Claude Opus 4.8," reserving Fable 5 for workloads that need the highest available capability. OpenAI's equivalent default for complex work is GPT-5.5 itself. That makes this the fair fight: the model each vendor expects you to use for most serious work, at the same input price.

Head-to-Head: Specs and Pricing

All pricing verified June 11, 2026 against developers.openai.com/api/docs/pricing and platform.claude.com/docs/en/about-claude/pricing. Benchmark figures are from Vellum's breakdown of Anthropic's launch materials.

The spec convergence is striking. Both models offer a 1M-class context window and an identical 128K max output. Knowledge cutoffs are a month apart. On raw capacity, these models are interchangeable. The differences live in three places: output price, benchmark profile, and ecosystem.

The Pricing Fine Print

The headline is simple: input is a tie, and Claude is cheaper on output - $25 versus $30 per million tokens, verified June 11, 2026. That is a 17% discount on the token type that dominates agentic workloads. A team generating 50 million output tokens a month pays $1,250 on Opus 4.8 versus $1,500 on GPT-5.5. The same ratio holds in batch mode, where both vendors apply a 50% discount: $12.50 versus $15.00 per million output tokens.

Caching is closer to a wash than it looks. Both vendors charge $0.50 per million tokens for cached input reads - a 90% discount off base input. The difference is on the write side: Anthropic bills cache writes at $6.25 per MTok (5-minute) or $10 (1-hour), while OpenAI's pricing page lists a single cached-input rate with no separate write charge. High cache churn adds real cost on the Claude side; stable system prompts read many times make it disappear into the noise.

Two honest caveats before declaring Claude the value winner:

• Tokenizers differ, so per-token prices are not directly comparable across providers. Anthropic's own pricing page notes that the tokenizer introduced with Opus 4.7 "may use up to 35% more tokens for the same fixed text" compared with earlier Claude models. Cross-provider, the only meaningful comparison is cost per completed task, measured on your own workload.
• Speed premiums cut both ways. Anthropic offers a fast mode research preview on Opus 4.8 at $10/$50 - double the price for roughly 2.5x the speed, per the Claude Code Week 22 digest. OpenAI sells a priority tier for GPT-5.5 at $12.50 input / $75.00 output - 2.5x base rates - per its pricing page. Note the structures differ: Anthropic's premium buys raw speed on the same requests, while OpenAI's buys prioritized processing.

One more structural note: Anthropic dropped its long-context premium, so a 900K-token request on Opus 4.8 bills at the same per-token rate as a 9K one. OpenAI's pricing page lists flat rates for GPT-5.5 as well, with a 10% uplift only for regional data-residency processing.

Benchmarks: Where Each Model Leads

The most complete public side-by-side comes from Vellum's analysis of the Fable 5 launch materials, which includes workhorse-tier numbers. On SWE-Bench Pro, the agentic coding benchmark built on real repository tasks, Opus 4.8 scores 69.2% against GPT-5.5's 58.6% - a 10.6-point gap. DataCamp's independent coverage cites the same 58.6% figure for GPT-5.5, which is a useful cross-check. On FrontierCode Diamond, a harder production-codebase split, Opus 4.8 leads 13.4% to 5.7%.

GPT-5.5 takes the vision-heavy document benchmark: 24.9% on GDP.pdf versus Opus 4.8's 22.5%. That is a small but real edge for knowledge work that runs through PDFs, charts, and scanned documents. On ExploitBench, a cybersecurity evaluation, Opus 4.8 scores 40% to GPT-5.5's 34% (the restricted Claude Mythos 5 scores far higher, but it is not generally available).

The usual caveats apply with full force. These numbers were compiled from Anthropic's launch materials, so treat the exact margins with skepticism even where third parties republish them. Benchmarks also compress latency, instruction-following style, and refusal behavior into single numbers. Our Claude vs GPT coding comparison goes deeper on how the two families behave in practice, and our look at Opus 4.8's agent honesty covers a dimension no leaderboard captures: how reliably the model reports what it actually did.

The fair summary: Opus 4.8 has the stronger published profile for agentic coding, GPT-5.5 edges ahead on vision-document work, and both are far enough above last year's models that either feels strong day to day.

Tooling: Claude Code Defaults and the OpenAI Surface Area

Model choice increasingly follows tooling choice. In the last week of May 2026, Opus 4.8 became the default model in Claude Code for Max, Team Premium, Enterprise pay-as-you-go, and Anthropic API accounts, defaulting to high effort, per the Week 22 digest. Even after Fable 5 shipped on June 9, Anthropic's models overview still points developers at Opus 4.8 as the starting point for complex tasks. If your team lives in Claude Code, Opus 4.8 is the path of least resistance.

OpenAI's pitch is surface area. The GPT-5.5 model page lists support across Chat Completions, Responses, Realtime, Batch, fine-tuning, image generation, and speech endpoints - a breadth the Opus 4.8 docs pages do not match. If your product needs one model id wired into voice, vision, and fine-tuning pipelines, GPT-5.5's ecosystem argument is real. Our GPT-5.5 developer guide walks through that surface in detail.

Decision Guide by Persona

The agent builder. Opus 4.8. The published agentic coding gap (69.2% vs 58.6% on SWE-Bench Pro) plus 17% cheaper output - the token type agents burn most - stacks two advantages on the same side.

The high-volume output shop. Opus 4.8 on the Batch API: $12.50 per million output tokens versus $15.00. At volume, that 17% compounds. Just re-baseline token counts first, since the Opus 4.7+ tokenizer can inflate counts for identical text.

The document and vision knowledge team. GPT-5.5. It posts the better GDP.pdf score and pairs it with native image and speech endpoints if your pipeline goes multimodal.

The platform consolidator. GPT-5.5. One model id across Realtime, fine-tuning, and generation endpoints is an operational simplification Anthropic does not offer at this tier.

The undecided. Run both at $5 input on a two-week pilot against your real tasks. The pricing symmetry makes this the cheapest A/B test this tier has ever offered. Our OpenAI vs Anthropic 2026 comparison covers the platform-level factors beyond this matchup.

When to Skip Both - or Stay Put

Neither model is the right call for everything.

• Routine tasks do not need a $5 model. Claude Sonnet 4.6 ($3/$15) and GPT-5.4 ($2.50/$15) sit one tier down at roughly half the cost, verified June 11, 2026 on the same pricing pages. Classification, summarization, and well-scoped edits rarely justify workhorse rates.
• The hardest problems may justify the ceiling tier. If Opus 4.8 fails repeatedly on a long-horizon task, Fable 5 at $10/$50 can be cheaper per completed task. That math is in our flagship comparison.
• Budget-constrained workloads have a floor far below this. DataCamp's DeepSeek V4 analysis positions open-weights models a few months behind the closed frontier at a fraction of the price - V4 Pro lists at $1.74 input / $3.48 output.
• If you are already on Opus 4.7, the upgrade is cheap but not mandatory. Opus 4.7 and 4.8 share the same $5/$25 pricing, so the switch costs nothing on rates - but a tuned pipeline with stable evals does not need to move the same week.

FAQ

Is Claude Opus 4.8 cheaper than GPT-5.5?

On input, no - both cost $5.00 per million tokens (verified June 11, 2026). On output, yes: Opus 4.8 charges $25 versus GPT-5.5's $30, about 17% less, and the gap persists in batch mode ($12.50 vs $15.00). The caveat is tokenizer differences: compare cost per completed task, not per-token rates.

Which is better for coding, GPT-5.5 or Claude Opus 4.8?

On published benchmarks, Opus 4.8 leads agentic coding: 69.2% versus 58.6% on SWE-Bench Pro and 13.4% versus 5.7% on FrontierCode Diamond, per Vellum's compilation of Anthropic's launch data. Those figures originate from one vendor's materials, so run your own evaluation - but the direction matches Opus 4.8's role as the default model in Claude Code.

Do GPT-5.5 and Claude Opus 4.8 have the same context window?

Effectively yes. GPT-5.5 lists 1,050,000 tokens and Opus 4.8 lists 1M, both with 128K max output. One exception: Opus 4.8 is limited to 200K context on Microsoft Foundry. Neither vendor charges a long-context premium at this tier.

When does GPT-5.5 make more sense than Opus 4.8?

When your workload is vision-document heavy (GPT-5.5 scores 24.9% vs 22.5% on GDP.pdf), when you need one model across Realtime, fine-tuning, speech, and image endpoints, or when your stack is already built on OpenAI's APIs and the 17% output-price difference does not move your bill enough to justify a migration.

Should I use Claude Fable 5 instead of Opus 4.8?

Only for workloads that need the highest available capability. Fable 5 costs exactly double ($10/$50), and Anthropic's own models overview still directs most complex work to Opus 4.8 first. Start at the workhorse tier and escalate only when you have evidence the cheaper model is failing.

Sources

• OpenAI API pricing - GPT-5.5, GPT-5.5-pro, and GPT-5.4 family rates, batch discounts (accessed June 11, 2026)
• OpenAI GPT-5.5 model page - context window, max output, knowledge cutoff, supported endpoints (accessed June 11, 2026)
• Anthropic pricing - Opus 4.8 and Fable 5 rates, caching, batch, fast mode, long-context policy, tokenizer note (accessed June 11, 2026)
• Anthropic models overview - Opus 4.8 positioning, specs, knowledge cutoffs, Foundry context limit (accessed June 11, 2026)
• Claude Code What's New, Week 22 - Opus 4.8 as Claude Code default, fast mode pricing (accessed June 11, 2026)
• Vellum: Claude Fable 5 and Mythos 5 benchmarks explained - SWE-Bench Pro, FrontierCode Diamond, GDP.pdf, ExploitBench figures (accessed June 11, 2026)
• DataCamp: DeepSeek V4 - independent GPT-5.5 SWE-Bench Pro figure, open-weights pricing context (accessed June 11, 2026)

Note: OpenAI's GPT-5.5 launch announcement page could not be fetched directly (it returns an error to automated requests), so launch-post-only claims are not cited in this comparison. Priority-tier rates come from the API pricing page, which loads normally.