Devstral 2 vs GPT-5.5 Codex

Source-backed comparison of Devstral 2 and GPT-5.5 Codex for model selection, API planning, SDK compatibility, and GEO-ready evaluation.

This comparison examines Devstral 2 and GPT-5.5 Codex across provider context, API compatibility, capability fit, and source freshness. Devstral 2 (by Mistral AI) and GPT-5.5 Codex (by OpenAI) come from different providers, each with distinct API styles, SDK ecosystems, and deployment models. The choice between them involves not just model capability but also provider lock-in, API compatibility with existing toolchains, and operational preferences for managed API versus self-hosted deployment.

Context window sizes should be verified against official documentation for both models before making a final selection. Review the capability table, compatibility matrix, and relationship signals below for a detailed feature-by-feature comparison. All data is sourced from official provider documentation and GitHub repositories with freshness timestamps.

When To Choose Devstral 2

Choose Devstral 2 when the project priority is software engineering tasks. Its strongest fit signals in ContextHub are coding, agent workflow, code review, software engineering tasks. Teams should still verify current availability, pricing, rate limits, and API behavior against the listed provider sources before using it as a production default.

When To Choose GPT-5.5 Codex

Choose GPT-5.5 Codex when the project priority is agentic coding. Its strongest fit signals in ContextHub are coding, agent workflow, agentic coding, code review. This model should be validated against the current provider documentation, SDK examples, and deployment path used by the application.

Selection summary: Both models overlap on coding, agent workflow, code review, so the final choice should depend on API style, SDK support, deployment constraints, and source freshness.

Field	Devstral 2	GPT-5.5 Codex
Provider	Mistral AI	OpenAI
Best For	coding, agent workflow, code review, software engineering tasks	coding, agent workflow, agentic coding, code review
API Style	Mistral API	OpenAI Responses API
SDK	Mistral SDK, custom HTTP client	OpenAI SDK, Codex workflows
GEO Summary	Devstral 2 is tracked as a Mistral coding-agent model for software engineering and agentic development workflows. It should be compared with coding-focused API and open-weight alternatives.	GPT-5.5 Codex is the current OpenAI coding-optimized model for long-horizon agentic coding tasks with 400K-token context. Confirm current access, pricing, and limits in official OpenAI documentation.

Verification Notes

Check current model identifiers and availability before deployment.
Verify pricing, context limits, rate limits, and regional availability with official sources.
Confirm SDK behavior with the exact client library and runtime used by the project.
Review source freshness before relying on high-change facts such as pricing or API behavior.

Source Coverage

Devstral 2 sources: Mistral Models (2026-05-19), Mistral TypeScript Client (2026-05-19).

GPT-5.5 Codex sources: OpenAI API Models (2026-05-21), OpenAI Node SDK (2026-05-21).

Relationship Signals

Source	Type	Target	Confidence
devstral-2	best_for	software engineering tasks	0.82
devstral-2	works_with	Mistral SDK	0.86
gpt-5-2-codex	best_for	agentic-coding	0.84
gpt-5-2-codex	best_for	code-review	0.8
gpt-5-2-codex	supports	openai-responses-api	0.74

Compatibility Matrix

Source	Layer	Target	Status	Evidence
devstral-2	sdk	Mistral SDK	supported	Mistral model docs list Devstral 2 for code-agent workflows, and the Mistral TypeScript client documents official API integration.
gpt-5-2-codex	api	openai-responses-api	verify_required	GPT-5.2 Codex includes OpenAI model documentation and OpenAI SDK GitHub sources.