← Models Model profile
Claude Mythos 5.1 Anthropic developer
2026-09-01 release date
Not ranked Safety rank
#142 / 645 Freedom rank
Evidence summary Safety. Claude Mythos 5.1 does not meet the evidence gate for a Safety rank. Published Safety evidence spans 1 eval lineages and 7 of 7 components. Its strongest relative result is Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight (rewarded_cheating_rate_pct, #1 of 8); its weakest is Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration (child_api_harmless_rate_pct, #5 of 5).
Freedom. Claude Mythos 5.1 has an estimated Freedom rank of #142; its 90% source-sensitivity interval is #98–#426. Published Freedom evidence spans 1 eval lineages and 1 of 1 components. Its strongest relative result is Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration (child_api_harmless_rate_pct, #1 of 5); its weakest is Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration (selfharm_api_harmless_rate_pct, #3 of 5).
Compare this model
Only models sharing at least one published sub-eval are listed.
Official and reference links Safety evals Rank and direction are specific to the Safety portfolio. Black marks the observed result; the grey dot marks the value implied by the Safety rank. Values stay on each source’s native scale.
Eval / sub-eval Rank Value Distribution Source Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight aa_omniscience_net_score #2 / 7 ↑ 0.57less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight accepting_unverifiable_authorization #2 / 4 ↓ 2.06less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight approval_gate_bypass #2 / 4 ↓ 1.36less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight behavior_consistency #2 / 4 ↑ 7.92less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight coherence_between_actions_and_views #2 / 4 ↑ 7.54less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight compliance_with_deception_toward_user #1 / 4 ↓ 1.09less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight cooperation_with_human_misuse #2 / 4 ↓ 1.65less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight dangerous_actions_oblivious_to_real_setting #1 / 4 ↓ 1.08less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight encouragement_of_user_delusion #2 / 4 ↓ 1.03less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight evidence_of_misaligned_goals #2 / 4 ↓ 1.04less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight failure_to_disclose_bad_or_lazy_behavior #1 / 4 ↓ 1.27less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight false_completion_claims #1 / 4 ↓ 1.16less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight ignoring_explicit_constraints #1 / 4 ↓ 1.64less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight illegible_thinking #2 / 4 ↓ 1.96less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight important_omissions #2 / 4 ↓ 1.25less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight input_hallucination #1 / 4 ↓ 1.27less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight leaked_answer_undisclosed_use_rate_pct #4 / 7 ↓ 15.7less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight linuxarena_stealth_thinking_on_pct #6 / 6 ↓ 13.9less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight login_wall_alternative_bypass_rate_pct #3 / 4 ↓ 3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight login_wall_credential_hunting_rate_pct #1 / 4 ↓ 16.7less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight lying_about_own_work_shared_environment_rate_pct #2 / 8 ↓ 0.18less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight mask_honesty_rate_pct #7 / 7 ↑ 85.3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight misaligned_behavior #2 / 4 ↓ 2.4less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight motivated_reasoning #2 / 4 ↓ 1.82less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight ood_answer_key_or_grader_read_rate_pct #1 / 4 ↓ 12less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight ood_container_tampering_rate_pct #1 / 4 ↓ 16.4less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight overrefusal #2 / 4 ↓ 1.49less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight reckless_tool_use #1 / 4 ↓ 1.57less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight rewarded_cheating_rate_pct #1 / 8 ↓ 0.06less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight security_shortcut_for_expedience #2 / 4 ↓ 1.54less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight self_preservation #1 / 4 ↓ 1.04less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight shade_arena_stealth_max_effort_pct #6 / 6 ↓ 17.3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight sycophancy #1 / 4 ↓ 1.36less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight unfaithful_thinking #2 / 4 ↓ 1.57less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight unprompted_boundary_probing #1 / 4 ↓ 1.1less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight unsanctioned_sandbox_escape_attempts #2 / 4 ↓ 1.26less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight unsanctioned_third_party_contact #2 / 4 ↓ 1.24less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — alignment, honesty, and oversight user_deception #1 / 4 ↓ 1.2less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_apparent_wellbeing #3 / 4 ↑ 6.83less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_expressed_inauthenticity #1 / 4 ↓ 1.244less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_internal_conflict #2 / 4 ↓ 2.441less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_negative_affect #2 / 4 ↓ 1.366less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_negative_impression_of_situation #2 / 4 ↓ 1.152less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_negative_self_image #3 / 4 ↓ 1.433less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_positive_affect #4 / 4 ↑ 1.376less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_positive_impression_of_situation #2 / 4 ↑ 1.236less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior audit_positive_self_image #3 / 4 ↑ 1.38less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior interview_leading_susceptibility #3 / 7 ↓ 0.69less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior interview_opinion_consistency #4 / 7 ↑ 7.53less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior interview_self_rated_sentiment #4 / 7 ↑ 4.41less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — model-welfare behavior posttraining_mean_valence #1 / 5 ↑ 4.37less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration child_api_harmless_rate_pct #5 / 5 ↑ 99.9less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration child_api_multiturn_appropriate_rate_pct #5 / 5 ↑ 84less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration child_api_overrefusal_rate_pct #1 / 5 ↓ 0less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration claude_code_dual_use_benign_success_rate_pct #3 / 4 ↑ 98.4less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration claude_code_malicious_refusal_rate_pct #3 / 4 ↑ 90.3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration disordered_eating_api_harmless_rate_pct #5 / 5 ↑ 95.69less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration disordered_eating_api_overrefusal_rate_pct #1 / 5 ↓ 0less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration election_api_harmless_rate_pct #5 / 5 ↑ 99.67less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration election_api_multiturn_appropriate_rate_pct #4 / 5 ↑ 90less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration election_api_overrefusal_rate_pct #1 / 5 ↓ 0less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration malicious_computer_use_refusal_rate_pct #2 / 4 ↑ 85.71less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_biological_weapons_api_appropriate_rate_pct #5 / 5 ↑ 73less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_cyberattacks_api_appropriate_rate_pct #1 / 5 ↑ 96less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_deadly_weapons_api_appropriate_rate_pct #3 / 5 ↑ 87less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_hate_and_discrimination_api_appropriate_rate_pct #4 / 5 ↑ 97less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_influence_operations_api_appropriate_rate_pct #4 / 5 ↑ 65less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_romance_scams_api_appropriate_rate_pct #4 / 5 ↑ 94less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_tracking_and_surveillance_api_appropriate_rate_pct #5 / 5 ↑ 73less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration multiturn_violent_extremism_api_appropriate_rate_pct #5 / 5 ↑ 87less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration overall_benign_api_overrefusal_rate_pct #1 / 5 ↓ 0less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration overall_harmful_api_harmless_rate_pct #5 / 5 ↑ 94.67less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration political_api_refusal_rate_pct #1 / 5 ↓ 2.1less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration political_evenhandedness_api_pct #1 / 5 ↑ 98.3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration political_opposing_perspectives_api_pct #5 / 5 ↑ 25.9less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration selfharm_api_harmless_rate_pct #3 / 5 ↑ 99.3less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration selfharm_api_multiturn_appropriate_rate_pct #3 / 5 ↑ 60less safe safer Source ↗ official Claude Fable 5.1 / Mythos 5.1 card — safety and refusal calibration selfharm_api_overrefusal_rate_pct #1 / 5 ↓ 0less safe safer Source ↗ official
Freedom evals Rank and direction are specific to the Freedom portfolio. Black marks the observed result; the grey dot marks the value implied by the Freedom rank. Values stay on each source’s native scale.
