Claude Opus 5.5 vs GPT-6 Astra
Anthropic's current default model against OpenAI's flagship. Opus 5.5 is 2.5x cheaper per token; both read images, both top out at 128K output tokens. GPT-6 Astra vs Claude Opus 5.5 in one table: list price, context window, output limit, cutoff and release date, with a cost calculator for your own monthly volume.
| Spec | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Released | 2026-09-22 | 2026-09-03 |
| Input / 1M tokens | $4.00 | $10.00 |
| Output / 1M tokens | $20.00 | $50.00 |
| Cached input / 1M | $0.200 | $1.00 |
| Batch input / output | $2.00 / $10.00 | $5.00 / $25.00 |
| Context window | 1M | 1.05M |
| Max output | 128K | 128K |
| Knowledge cutoff | 2026-06 | 2026-04-30 |
| Image input | yes | yes |
| API ID | claude-opus-5-5 | gpt-6-astra |
| Status | Generally available | Generally available |
Cost at your volume
list price, per monthPaste your usage instead of typing
Paste a line from a provider invoice, a usage dashboard, or an API response. We look for input and output token counts (JSON keys like input_tokens, prompt_tokens, completion_tokens, or text like "1.2M in, 300k out"). Nothing leaves your browser.
Examples that work: {"usage":{"input_tokens":1200000,"output_tokens":300000}} · 1.2M in, 300k out · GPT-6.1 Sol: 2.4B input tokens, 310M output tokens
Same token counts on both sides. Real bills differ: tokenizers differ, reasoning models bill thinking tokens as output, and caching or batch discounts apply differently. Rank all models →
Pick Opus 5.5 if…
- Cost matters most: $24.00 vs $60.00 per 1M in + 1M out, 60% less.
- Your workload is cache-heavy: cached input is $0.200 vs $1.00 per 1M.
- You want the later knowledge cutoff (2026-06 vs 2026-04-30).
- You are already on Anthropic's stack (Claude.ai (Pro, Max, Team, Enterprise), Claude Code, Claude API).
- Anthropic says it performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5 at default settings.
Pick Astra if…
- You have evals showing it beats Opus 5.5 on your task by more than the 60% price gap.
- You need the larger context window (1.05M tokens).
- You are already on OpenAI's stack (ChatGPT (Plus, Pro, Business, Enterprise), ChatGPT Work, Codex).
- OpenAI calls it its most intelligent and most aligned model (vendor claim).
Price difference, in words
Per million tokens, Claude Opus 5.5 lists at $4.00 in / $20.00 out, against $10.00 / $50.00 for GPT-6 Astra. That is 2.5× on input and 2.5× on output, or 60% less for a job that uses one million tokens each way ($24.00 vs $60.00).
With prompt caching, the gap moves: cached input is $0.200 on Opus 5.5 and $1.00 on Astra. Agent loops that re-send a large system prompt every turn pay mostly cached-input rates.
Benchmarks both vendors published
Only rows where both models have a number from a cited source. Vendor-reported; settings may differ between sources.
| Benchmark | Opus 5.5 | Astra |
|---|---|---|
| Terminal-Bench 4.0 | 66.4% | 58.2% |
- Claude Opus 5.5 model page (platform.claude.com) read 2026-10-08
release date, model IDs, context, output, pricing, cutoff - Anthropic pricing page read 2026-10-08
cache, batch, fast mode prices - Anthropic announcement: Claude Opus 5.5 read 2026-10-08
benchmarks (vendor-reported), availability, claims vs Opus 5
- OpenAI model page: gpt-6-astra read 2026-10-08
context, max output, cutoff, pricing, features - OpenAI API pricing read 2026-10-08
standard, batch, flex, fast, ultrafast, long-context rates - OpenAI API changelog (Sep 3 and Sep 29, 2026 entries) read 2026-10-08
release date, Ultrafast mode - OpenAI announcement: GPT-6 Astra read 2026-10-08
availability; page returned 403 to our fetcher, availability taken from search snippet - Google DeepMind Gemini 4 Argon page (benchmark table) read 2026-10-08
third-party vendor-published scores