What “best AI coder” actually means
Search results still sell a single winner. Real teams split the job: a default model for daily edits, a heavier model for refactors, and an agent that can touch many files without wrecking the branch. AICoder tracks those layers separately — model price, coding benchmarks, and agents — so the pick is a stack, not a mascot.
The default: Claude Sonnet 5
Claude Sonnet 5 is the practical default. It is $2 / $10 per million tokens, 1M context, and strong on the coding-oriented boards we mirror. Pair it with Claude Code or Cursor when you want the model to edit the tree, not just chat. That combination is what most “best AI for coding” threads are actually describing.
When to pay for Opus, GPT-5.6 Sol, or DeepSeek
Claude Opus 5 currently leads our LMArena Agent board, but it is $15 / $75 per million tokens — use it as a specialist, not a tab-complete engine. GPT-5.6 Sol is close on agent score at $5 / $30 if your toolchain is already OpenAI. DeepSeek-V4-Pro sits near the same cluster of scores at $0.66 / $1.98, which is why it wins the cost conversation without being a toy model.
How to choose in 30 seconds
Solo app or feature work: Sonnet 5 + Cursor or Claude Code. Hard multi-file change: Opus 5 for the plan, Sonnet 5 to implement. High volume or local-friendly cost: DeepSeek-V4-Pro or V4-Flash. Recheck the live leaderboard before you lock a quarter — these boards move.