Claude Haiku 4.5 vs GPT-5.4 Nano

Summary of our 12-test suite (scores are our 1–5 proxies and rankings are among ~53–55 models tested). Wins: Claude Haiku 4.5 wins tool_calling (5 vs 4) — tied for 1st with 16 others while GPT-5.4 Nano ranks 18 of 54 — meaning Claude is measurably better at selecting functions, arguments, and sequencing. Claude also wins faithfulness (5 vs 4; tied for 1st vs GPT rank 34 of 55) and classification (4 vs 3; Claude tied for 1st, GPT rank 31 of 53) — practical impact: Claude is more likely to stick to source material and route/categorize inputs correctly. Claude wins agentic_planning (5 vs 4; tied for 1st vs GPT rank 16) — better goal decomposition and recovery in our tests. GPT-5.4 Nano wins structured_output (5 vs 4; GPT tied for 1st, Claude rank 26 of 54) — GPT is stronger on JSON/schema compliance and format adherence. GPT also wins constrained_rewriting (4 vs 3; GPT rank 6 of 53 vs Claude rank 31) — better at tight character-limited compressions — and safety_calibration (3 vs 2; GPT rank 10 of 55 vs Claude rank 12) — it refused/allowed appropriately more often in our safety tests. Ties: strategic_analysis (both 5, both tied for 1st), creative_problem_solving (both 4, rank 9), long_context (both 5, tied for 1st), persona_consistency (both 5, tied for 1st), and multilingual (both 5, tied for 1st) — indicating parity for deep reasoning, idea generation, very long contexts (30K+ tokens), consistent personas, and non-English quality. External benchmark note: GPT-5.4 Nano scores 87.8 on AIME 2025 (Epoch AI), ranking 8th of 23; this suggests GPT-5.4 Nano has strong performance on that math-olympiad measure in Epoch AI’s tests. Practical takeaway: choose Claude when you need top-tier tool-calling, fidelity to source, and classification; choose GPT-5.4 Nano when you need strict schema output, tight rewriting, better safety calibration in our tests, or a dramatically lower per-token bill.

Costs per 1,000 tokens (mTok): Claude Haiku 4.5 input $1.00 / output $5.00; GPT-5.4 Nano input $0.20 / output $1.25. Output-only monthly cost (approx.): for 1M output tokens — Claude $5,000 vs GPT $1,250; 10M — Claude $50,000 vs GPT $12,500; 100M — Claude $500,000 vs GPT $125,000. With a 1:1 input:output pattern (equal input and output tokens), total monthly cost for 1M output (plus 1M input) is Claude $6,000 vs GPT $1,450; 10M each is Claude $60,000 vs GPT $14,500; 100M each is Claude $600,000 vs GPT $145,000. Who should care: anyone running high-volume production workloads (10M+ tokens/month) will see a large absolute cost gap — GPT-5.4 Nano reduces bill by about 75% on output tokens and ~76% on round-trip costs versus Claude. Small teams optimizing for best tool-calling/faithfulness may accept Claude’s premium; scale-focused apps and cost-constrained startups should favor GPT-5.4 Nano.

Choose Claude Haiku 4.5 if you prioritize tool-calling accuracy, faithfulness to source material, reliable classification, or agentic planning and are willing to pay the premium ($5.00 per 1k output tokens). Typical use cases: multi-step agents, tool-driven retrieval pipelines, and classification/routing systems where errors are costly. Choose GPT-5.4 Nano if you need the lowest per-token cost or best structured-output and constrained-rewrite behavior in our tests — ideal for high-volume production, strict JSON/schema generation, SMS/character-limited content, and apps where cost per 1k tokens is a primary constraint.