Claude Sonnet 4.5 vs GPT-5.2 Codex

Claude Sonnet 4.5 (2025) and GPT-5.2 Codex (2025) compare a standalone API model against a coding-specialized model. Claude Sonnet 4.5 ships a 200k-token context window, while GPT-5.2 Codex ships a 400k-token context window. On SWE-bench Verified, Claude Sonnet 4.5 leads by 4.4 pts. On pricing, Claude Sonnet 4.5 ranges from $3 to $6/1M input tokens by tier; GPT-5.2 Codex costs $1.75/1M input tokens. This page treats the result as workflow and deployment fit, not a universal model winner.

Treat this as a product-type comparison: Claude Sonnet 4.5 is standalone API model, while GPT-5.2 Codex is coding-specialized model. Choose based on workflow fit before reading any benchmark or price row as decisive.

Decision scorecard

Local evidence first

Signal	Claude Sonnet 4.5	GPT-5.2 Codex	How to read it
Product type	Standalone API model	Coding-specialized model	Read downstream rows through the product-type lens before comparing benchmarks, prices, or provider availability.
Best for	reasoning-heavy apps, multimodal apps, and tool-calling agents	custom coding agents, code generation, and tool loops	Use-case synthesis from product type, capability flags, context, and provider data.
Decision fit	Coding, RAG, and Agents	Coding, RAG, and Agents	Primary workload tags from local decision data.
Context window	200k	400k	Higher is better when prompts, retrieval chunks, or transcripts are large.
Cheapest output	$15/1M tokens	$14/1M tokens	Cheapest tracked provider route; verify your exact region and tier.
Provider routes	8 tracked	2 tracked	Broader coverage can reduce vendor lock-in and fallback risk.
Shared benchmarks	SWE-bench Verified leader	1 shared	Visible benchmark lead is 4.4 points on SWE-bench Verified.

Decision tradeoffs

Choose Claude Sonnet 4.5 when...

Claude Sonnet 4.5 holds a shared-benchmark lead on SWE-bench Verified, ahead by 4.4 points.
Claude Sonnet 4.5 has broader tracked provider coverage for fallback and route flexibility.
Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.

Choose GPT-5.2 Codex when...

GPT-5.2 Codex has the larger context window for long prompts, retrieval packs, or transcript analysis.
GPT-5.2 Codex has the lower cheapest tracked output price at $14/1M tokens.
GPT-5.2 Codex uniquely exposes Code execution in local model data.
Local decision data tags GPT-5.2 Codex for Coding, RAG, and Agents.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate GPT-5.2 Codex

Requests / monthInput tokens / requestOutput tokens / request

Claude Sonnet 4.5

$6,150

Cheapest tracked route/tier: Microsoft Foundry

GPT-5.2 Codex

$4,900

Cheapest tracked route/tier: Vercel AI Gateway

Estimated monthly gap: $1,250. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Sonnet 4.5 -> GPT-5.2 Codex

Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
GPT-5.2 Codex is $1/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
GPT-5.2 Codex adds Code execution in local capability data.

GPT-5.2 Codex -> Claude Sonnet 4.5

Provider overlap exists on Vercel AI Gateway; start route-level A/B tests there.
Claude Sonnet 4.5 is $1/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
Check replacement coverage for Code execution before moving production traffic.

Specs

Specification	Claude Sonnet 4.5 Anthropic	GPT-5.2 Codex OpenAI
Released	2025-09-29	2025-12-18
Context window	200k	400k
Parameters	—	—
Architecture	Decoder Only	Decoder Only
License	Proprietary	Proprietary
Openness	Proprietary	Proprietary
Weights	Not released	Not released
Code	Unknown	Unknown
Commercial use	Commercial use: conditional	Commercial use: conditional
Knowledge cutoff	2025-12	2025-08

Pricing and availability

Pricing attribute	Claude Sonnet 4.5	GPT-5.2 Codex
Input price	0-200,001t $3/1M tokens 200,001t+ $6/1M tokens	$1.75/1M tokens
Output price	0-200,001t $15/1M tokens 200,001t+ $22.50/1M tokens	$14/1M tokens
Providers	Microsoft Foundry Anthropic Snowflake Cortex GCP Vertex AI AWS Bedrock Replicate API	Vercel AI Gateway OpenAI API

Capabilities

Capability	Claude Sonnet 4.5	GPT-5.2 Codex
Vision	Yes	Yes
Multimodal	Yes	Yes
Reasoning	Yes	Yes
JSON / Tool use	Yes	Yes
Structured outputs	Yes	Yes
Code execution	No	Yes
IDE integration	No	No
Computer use	No	No
Parallel agents	No	No

Benchmarks

Benchmark	Claude Sonnet 4.5	GPT-5.2 Codex
SWE-bench Verified	77.2	72.8

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Model pages

Labs and families

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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.

Both models

Claude Sonnet 4.5 GPT-5.2 Codex