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MODEL SIGNAL · OPENAI

GPT-5.5

OpenAI's latest flagship with noticeably stronger reasoning and autonomy than GPT-5.4. Available in standard and Pro variants. 1M context window, $5/$30 per 1M tokens for standard.

CATEGORYReasoning
CONTEXT1M
RELEASEDApril 23, 2026
Key Features
  • Stronger reasoning vs GPT-5.4
  • GPT-5.5 Pro variant
  • 1M context window
  • Codex integration
  • $5/$30 API pricing

Provider announcement →

Read the Model Signal report →

MODEL SIGNAL

GPT-5.5

OpenAI evolves its reasoning flagship with standard and Pro tiers, native Codex integration, and a focus on advanced developer workflows.

Bottom line

OpenAI has launched GPT-5.5, updating its frontier reasoning category. By introducing a distinct "Pro" variant and explicitly integrating Codex, the release signals a bifurcated approach to high-end inference, separating heavy code-generation and multi-step logic from baseline flagship tasks.

Signal

The core confirmed signal is the structural split of the flagship model into standard and GPT-5.5 Pro variants, coupled with the re-emergence of Codex as a named, integrated capability. The operator read is clear: OpenAI is acknowledging that extreme reasoning and advanced software engineering tasks demand a specialized, heavier compute profile. By integrating Codex natively into the reasoning pipeline, operators can anticipate stronger performance on agentic coding tasks, complex refactoring, and multi-step logic that may have challenged GPT-5.4. This tiering requires teams to rethink their routing strategies, explicitly evaluating which workflows require the "Pro" overhead versus the standard 5.5 model.

Noise

The noise surrounds the unconfirmed operational limits of the new deployment. Early claims circulating about specific context window depths—often cited as hitting the 1M token mark—and hard API pricing bands remain unverified and quarantined from our confirmed assessment. Until production telemetry validates these figures at scale, operators should avoid locking in architectural budgets or relying on maximum context utilization assumptions based on preliminary chatter.

Where it fits

GPT-5.5 is positioned squarely at the top of the reasoning and code generation stack. The emerging pattern suggests this model is built for high-stakes, multi-step problem solving rather than low-latency, high-throughput chat. The standard variant is likely to slot into complex enterprise routing where GPT-5.4 previously lived, while the Pro variant targets autonomous software engineering workflows, rigorous data analysis, and agentic tasks where the cost of a logical failure heavily outweighs the cost of inference.

Model Signal · Signal + Noise · Isaiah Steinfeld