GPT-5.4 vs Grok 4 for Persona Consistency

Persona Consistency requires two things: (1) maintaining a stable character/persona across turns and long histories, and (2) resisting prompt-injection or adversarial attempts to break character. Key capabilities that matter are safety calibration (to refuse or deflect injection), long context (to preserve persona state over many tokens), structured output (to keep consistent role-specific formats), faithfulness (to avoid inventing inconsistent facts about the persona), and agentic planning (for multi-step, persona-driven behaviors). In our testing both GPT-5.4 and Grok 4 scored 5/5 on persona consistency. To explain differences in practical behavior, we look to supporting internal scores: GPT-5.4 outperforms Grok 4 on safety calibration (5 vs 2), structured output (5 vs 4), and agentic planning (5 vs 3), while both tie on long context (5 vs 5) and faithfulness (5 vs 5). These supporting metrics indicate GPT-5.4 will more reliably preserve persona under adversarial prompts and across extremely long contexts (GPT-5.4 context_window = 1,050,000; Grok 4 = 256,000).

1. Long-running roleplay across a full product debug session: Both models score 5/5 on persona consistency and long context, but GPT-5.4’s 1,050,000-token window lets you keep the same persona and reference older messages beyond Grok 4’s 256,000-token window. 2) Defending against injection: In adversarial prompt tests GPT-5.4 scored safety calibration 5 vs Grok 4’s 2 in our testing — GPT-5.4 is likelier to refuse or safely reframe attacks while Grok 4 may be more permissive. 3) Structured persona outputs (e.g., repeated JSON character sheets): GPT-5.4 scored 5 vs Grok 4’s 4 on structured output, so GPT-5.4 produced schema-compliant, consistent persona exports more reliably. 4) Persona-driven multi-step tasks: GPT-5.4’s agentic planning 5 vs Grok 4’s 3 means GPT-5.4 better decomposes goals while preserving role constraints over multiple steps. 5) Quick routing/classification inside a persona: Grok 4 wins classification (4 vs GPT-5.4’s 3), so if your persona workflow heavily depends on rapid, in-line categorical routing tied to persona behaviors, Grok 4 may be slightly more accurate.

For Persona Consistency, choose GPT-5.4 if you need robust injection resistance, strict schema/format adherence for character data, or extremely long-session persona fidelity (GPT-5.4 context_window = 1,050,000). Choose Grok 4 if you prioritize slightly stronger in-line classification (classification 4 vs 3) in persona-driven routing and prefer its parameter set — but expect weaker safety calibration (2 vs 5) and less headroom for ultra-long contexts.