Claude Sonnet 4.6 vs GPT-5.4 for Persona Consistency

Persona Consistency demands (per our benchmarkDescriptions) that a model maintain character and resist injection. Key capabilities that matter are: safety_calibration (refusing harmful or irrelevant persona overrides), long_context (tracking persona across 30K+ tokens), faithfulness (sticking to the defined character), tool_calling (preserving persona during tool interactions), and structured_output (ensuring persona-aligned fields in schemas). With no external benchmark provided, our internal task scores are primary evidence: both models scored 5/5 on persona_consistency and are tied at rank 1. Supporting internal signals show differences useful for deployment decisions: Sonnet 4.6 scores 5 on tool_calling (helpful when agent/tool sequences must preserve persona) while GPT-5.4 scores 5 on structured_output (helpful when strict schema compliance must reflect persona). Both models score 5 on safety_calibration, faithfulness, and long_context in our tests — all core abilities for resisting persona injection.

1. Multi-step agent with persona-bound tool calls — Sonnet 4.6 shines: persona_consistency 5 plus tool_calling 5 means it kept character across function selection and arguments in our tests. 2) API that must return strict JSON blocks with persona fields — GPT-5.4 shines: both models are 5/5 on persona_consistency, but GPT-5.4 has structured_output 5 (vs Sonnet's 4), so it performed better on schema adherence while preserving persona. 3) Long chat history and role-play — both models perform equally: persona_consistency 5 and long_context 5. 4) File-based onboarding of persona documents — prefer GPT-5.4 because its modality is text+image+file->text (Sonnet is text+image->text). 5) Cost-sensitive input-heavy workloads — GPT-5.4 has lower input cost (2.5 per mTok vs Sonnet 3 per mTok); both have equal output cost (15 per mTok). Use these concrete score differences when mapping to your product flow.

For Persona Consistency, choose Claude Sonnet 4.6 if you need best-in-class tool calling while preserving persona (Sonnet: persona_consistency 5, tool_calling 5). Choose GPT-5.4 if you need strict structured output or file-based persona onboarding (GPT-5.4: persona_consistency 5, structured_output 5, modality includes file inputs). Both models tie on core persona metrics in our tests, so pick by integration, schema, tool workflow, or input-cost tradeoffs.