GPT-5.5 vs DeepSeek V4 Pro: Which Is Better for Coding? (2026)

head-to-head

Metric	GPT-5.5	DeepSeek V4 Pro
SWE-bench Verified	82.6%	80.6%
SWE-bench Pro	58.6%	55.4%
Terminal-Bench	82.7% (TB2.0)	67.9% (TB2.0)
Input $ / 1M	—	$0.435
Context	—	1M
Open weights	No	Yes
Maker	OpenAI	DeepSeek

when to pick each

Pick GPT-5.5 if

OpenAI's strongest agentic coder, with the deepest tooling and ecosystem breadth of the closed labs.

Pick DeepSeek V4 Pro if

The cheapest frontier-class coder — top open-weights score at ~11× less than Opus. Best pick when cost or self-hosting rules.

Ranked on our AI Coding Leaderboard, updated 2026-07-02. Scores are confirmed against primary sources; prices are per 1M input tokens and can change.

Primary sources

OpenAIvals.ai — SWE-bench Verified (independent) — Verified score from vals.ai independent eval; Pro is OpenAI-reported (rivals flag possible memorization on Pro).
DeepSeekDeepSeek V4 — specs & benchmarks — Independent tracker (llm-stats, June 2026); tied with Gemini 3.1 Pro on Verified, ahead on Pro.
BenchmarkSWE-bench — the real-GitHub-issue benchmark

$ quick-answers

Is GPT-5.5 better than DeepSeek V4 Pro for coding?

GPT-5.5 scores higher on SWE-bench Verified (82.6% vs 80.6%) and SWE-bench Pro, so it is the stronger coder on current benchmarks.

Which is cheaper, GPT-5.5 or DeepSeek V4 Pro?

Public per-token pricing isn't confirmed for both, so we don't print a price comparison yet.

Should I use GPT-5.5 or DeepSeek V4 Pro?

GPT-5.5 for the hardest, highest-stakes coding; DeepSeek V4 Pro when you want the best value or are running high volume. Both are frontier-class in 2026.