GPT-5.3-Codex vs Mercury 2.5
Detailed technical comparison between GPT-5.3-Codex (OpenAI) and Mercury 2.5 (Inception AI). Review live API token pricing, context window capabilities, time-to-first-token latency, and verified benchmark scores side-by-side.
Comparison Snapshot
GPT-5.3-Codex
400,000 tokensTie
Equal CapabilityTie
Equal SpeedMercury 2.5
$0.04 / MTokGPT-5.3-Codex
GPT-5.3-Codex is an advanced artificial intelligence model engineered by OpenAI. Tailored for complex multi-step reasoning, programming synthesis, and extended document comprehension, GPT-5.3-Codex represents a key architectural iteration in the OpenAI model family. First released in 2026-02-24, it serves enterprise developers, research teams, and autonomous system architects requiring strict instruction compliance. Featuring an input capacity of 400,000 tokens (approximately 533 words), GPT-5.3-Codex processes multi-file code repositories, lengthy technical reports, and complex prompts in a single inference call.
Mercury 2.5
Mercury 2.5 is an advanced artificial intelligence model engineered by Inception AI. Tailored for complex multi-step reasoning, programming synthesis, and extended document comprehension, Mercury 2.5 represents a key architectural iteration in the Inception AI model family. First released in 2026-09-08, it serves enterprise developers, research teams, and autonomous system architects requiring strict instruction compliance. Featuring an input capacity of 260,000 tokens (approximately 347 words), Mercury 2.5 processes multi-file code repositories, lengthy technical reports, and complex prompts in a single inference call.
Technical Specifications
🏆 = Superior Spec| Specification | GPT-5.3-Codex | Mercury 2.5 |
|---|---|---|
| Provider | OpenAI | Inception AI |
| Context Window | 400,000 tokens🏆 | 260,000 tokens |
| Agent Suitability | Not yet benchmarked | Not yet benchmarked |
| Time to First Token (TTFT) | No public TTFT data | No public TTFT data |
| Deployment Model | managed api | managed api |
| Production Stability | Stable GA (est.) | Stable GA (est.) |
| API Available | Yes | Yes |
| Released Date | 2026-02-24 | 2026-09-08 |
API Pricing Comparison
Input Price per Million Tokens
GPT-5.3-Codex
$1.75
Mercury 2.5
$0.04
Output Price per Million Tokens
GPT-5.3-Codex
$14.00
Mercury 2.5
$0.15
💡 Cost Ratio: Mercury 2.5 is 43.8x cheaper per input token than GPT-5.3-Codex.
Want to test both models live?
Run side-by-side prompt benchmarks in our dynamic multi-model Sandbox. Compare execution speeds, latency metrics, and compute actual costs in real-time.
Benchmark Performance Metrics
Standardized Scores (0–100%)Scores show verified raw accuracy percentages across standardized AI evaluation suites. Higher bars indicate superior performance in that domain.
GPT-5.3-Codex Quirks & Gotchas
No developer gotchas reported.
Mercury 2.5 Quirks & Gotchas
No developer gotchas reported.
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