{
  "tool_id": "art-617-m3p-monthly-cap-calculator",
  "note": "Fixture-oracle independence (FORMALVERIF-BUILD-SPEC.md 3d, preference #1): the first three rounding-mechanics vectors are the CLAUSE'S OWN worked examples -- 42 CFR 423.137(b)(2) (2000/12=166.67) and CMS Final Part Two Guidance section 50.2 + its footnote 38 (2000/3=666.67; 2000/11=181.82) -- reproduced under the CY2026 domain by choosing incurred_TrOOP_cents so the numerator equals the guidance's own 200000-cent figure; the shape of the reproduction is stated per-vector below. The CY2026-native, boundary, addend-split and invalid-domain vectors were hand-derived independently (closed-form: pick the inputs, then derive the expected cap by the declared half-up-cents rule) and cross-checked against build spec section 3's own named boundary_cases before the kernel was run. human_sign_off: PENDING.",
  "vectors": [
    {
      "name": "rounding-mechanics-166-67-2000-over-12",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 10000,
        "months_remaining": 12
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 200000,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 10000,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 12,
        "cap_cents": 16667,
        "cap_dollars_display": "166.67",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "CMS clause worked example 42 CFR 423.137(b)(2): 2000.00/12 = 166.666... rounds half-up to 166.67. Numerator is reproduced under the CY2026 threshold (210000) via incurred_TrOOP_cents=10000, leaving a 200000-cent numerator identical to the guidance example -- the rounding mechanics are what this vector pins, not the CY2025 threshold value itself, per build spec section 6 (the three inherited examples predate the CY2026 figure).",
      "golden_hash": "8de9edf758884c165aa20b31d263f20913a647c7f7a066576b36676c0e4f321d"
    },
    {
      "name": "rounding-mechanics-666-67-2000-over-3",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 10000,
        "months_remaining": 3
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 200000,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 10000,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 3,
        "cap_cents": 66667,
        "cap_dollars_display": "666.67",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "CMS Final Part Two Guidance section 50.2: 2000.00/3 = 666.666... rounds half-up to 666.67. Same 200000-cent numerator construction as the sibling vector, months_remaining=3.",
      "golden_hash": "dc0d199295c4d067c95bd50fe352a47b27a642e774f294295f1d8ac80b760847"
    },
    {
      "name": "rounding-mechanics-181-82-2000-over-11",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 10000,
        "months_remaining": 11
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 200000,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 10000,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 11,
        "cap_cents": 18182,
        "cap_dollars_display": "181.82",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "CMS Final Part Two Guidance section 50.2 footnote 38: 2000.00/11 = 181.818... rounds half-up to 181.82. Same 200000-cent numerator construction, months_remaining=11.",
      "golden_hash": "f1187242466e41242dcdcddfbec53fc1a6401dc9d82e7f22fea4f67b92be1f8c"
    },
    {
      "name": "cy2026-native-exact-175-00-2100-over-12",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 0,
        "months_remaining": 12
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 210000,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 0,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 12,
        "cap_cents": 17500,
        "cap_dollars_display": "175.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "CY2026-native control fixture: full annual threshold (210000 cents) over 12 months divides exactly, 210000/12=17500 cents=$175.00, no rounding hazard. Confirms the rounding step is a no-op when the division is exact rather than only ever exercising the non-terminating cases.",
      "golden_hash": "75731bb4fbaf3713c00a240530cfb1b2f83d1afacc48ead07ebf03a2e3ab1412"
    },
    {
      "name": "boundary-zero-numerator-one-month",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 210000,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 0,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 210000,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 1,
        "cap_cents": 0,
        "cap_dollars_display": "0.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "Boundary case from build spec section 3: numerator_cents=0 (incurred equals the full threshold), months_remaining=1. cap_cents=0.",
      "golden_hash": "aeda02894388bc092a64db08ada32bb86ff925615805670525c4140f39f83a65"
    },
    {
      "name": "boundary-max-numerator-one-month",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 0,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 210000,
        "numerator_breakdown": {
          "incurred_TrOOP_cents": 0,
          "annual_oop_threshold_cents": 210000
        },
        "months_remaining": 1,
        "cap_cents": 210000,
        "cap_dollars_display": "2100.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "Boundary case from build spec section 3: numerator_cents=210000 (nothing yet incurred), months_remaining=1. cap_cents=210000 ($2100.00), the maximum single-month cap the CY2026 threshold can ever produce.",
      "golden_hash": "7a174902f6bd2a9931f7696445100e08dbc193b78d6cd3b6d9871b906f6fca9e"
    },
    {
      "name": "addend-split-a-all-newly",
      "policy_parameters": {
        "branch": "subsequent_month",
        "remaining_owed_cents": 0,
        "newly_incurred_cents": 150000,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "subsequent_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 150000,
        "numerator_breakdown": {
          "remaining_owed_cents": 0,
          "newly_incurred_cents": 150000
        },
        "months_remaining": 1,
        "cap_cents": 150000,
        "cap_dollars_display": "1500.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "Exact-arithmetic addend-split check (build spec section 3): numerator=150000 realized entirely from newly_incurred_cents. cap_cents must equal the other two split vectors, confirming cap_cents is invariant under how the numerator was split between the two addends.",
      "golden_hash": "1d4affca2ed91cacbd0f779bf339c3197fc17537ebf315d358be8934ec24b5a8"
    },
    {
      "name": "addend-split-b-even",
      "policy_parameters": {
        "branch": "subsequent_month",
        "remaining_owed_cents": 75000,
        "newly_incurred_cents": 75000,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "subsequent_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 150000,
        "numerator_breakdown": {
          "remaining_owed_cents": 75000,
          "newly_incurred_cents": 75000
        },
        "months_remaining": 1,
        "cap_cents": 150000,
        "cap_dollars_display": "1500.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "Same 150000-cent numerator split evenly across both addends. Must match the other two split vectors exactly.",
      "golden_hash": "e912a6c48f5c19b2cd87317dd303050e459f05a562828b0d26637d238c9b23f9"
    },
    {
      "name": "addend-split-c-all-remaining",
      "policy_parameters": {
        "branch": "subsequent_month",
        "remaining_owed_cents": 150000,
        "newly_incurred_cents": 0,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "subsequent_month",
        "valid_input": true,
        "domain_errors": [],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 150000,
        "numerator_breakdown": {
          "remaining_owed_cents": 150000,
          "newly_incurred_cents": 0
        },
        "months_remaining": 1,
        "cap_cents": 150000,
        "cap_dollars_display": "1500.00",
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "Same 150000-cent numerator realized entirely from remaining_owed_cents. Must match the other two split vectors exactly.",
      "golden_hash": "bad85e7505495cc13aefb838a0aff75b7813ad4997029e289930542013e4a943"
    },
    {
      "name": "invalid-branch-rejected",
      "policy_parameters": {
        "branch": "bogus",
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": null,
        "valid_input": false,
        "domain_errors": [
          "branch must be exactly \"first_month\" or \"subsequent_month\""
        ],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": null,
        "numerator_breakdown": null,
        "months_remaining": 1,
        "cap_cents": null,
        "cap_dollars_display": null,
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "branch outside the declared {first_month, subsequent_month} enum is rejected -- valid_input:false, no cap computed, never silently defaulted to a branch.",
      "golden_hash": "d06cae5b529835bdcf791566eb796076c69f00d679b00f69ef472fc64781a0b5"
    },
    {
      "name": "invalid-incurred-out-of-range",
      "policy_parameters": {
        "branch": "first_month",
        "incurred_TrOOP_cents": 210001,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "first_month",
        "valid_input": false,
        "domain_errors": [
          "incurred_TrOOP_cents must be an integer in [0, 210000] (42 CFR 423.137(c)(1)(i))"
        ],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": null,
        "numerator_breakdown": null,
        "months_remaining": 1,
        "cap_cents": null,
        "cap_dollars_display": null,
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "incurred_TrOOP_cents=210001 exceeds the CY2026 annual threshold (210000) -- a real UI mistype possibility. Rejected, never clamped.",
      "golden_hash": "7d5ab17660d0bf9ff4d7b557d80b92cc979ed413b3c94f289e543a67bd6540bc"
    },
    {
      "name": "invalid-subsequent-sum-exceeds-threshold",
      "policy_parameters": {
        "branch": "subsequent_month",
        "remaining_owed_cents": 150000,
        "newly_incurred_cents": 100000,
        "months_remaining": 1
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "subsequent_month",
        "valid_input": false,
        "domain_errors": [
          "remaining_owed_cents + newly_incurred_cents (250000) exceeds the annual threshold (210000) -- every dollar counted in either counts once against the same annual threshold (42 CFR 423.137(c)(4))"
        ],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": null,
        "numerator_breakdown": null,
        "months_remaining": 1,
        "cap_cents": null,
        "cap_dollars_display": null,
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "remaining_owed_cents + newly_incurred_cents = 250000 exceeds the annual threshold (210000), violating 42 CFR 423.137(c)(4) (every dollar counts once against the same annual threshold). Rejected.",
      "golden_hash": "ec10f9774839c865353d7c90d3b0fbc78f621b4b3676b864f3fe56f064f02ebf"
    },
    {
      "name": "invalid-months-out-of-range-subsequent",
      "policy_parameters": {
        "branch": "subsequent_month",
        "remaining_owed_cents": 1000,
        "newly_incurred_cents": 0,
        "months_remaining": 12
      },
      "output_payload": {
        "plan_year": 2026,
        "branch": "subsequent_month",
        "valid_input": false,
        "domain_errors": [
          "months_remaining must be an integer in [1, 11] for branch \"subsequent_month\" (42 CFR 423.137(c)(3))"
        ],
        "annual_oop_threshold_cents": 210000,
        "annual_oop_threshold_source": "CMS Final CY 2026 Part D Redesign Program Instructions fact sheet",
        "annual_oop_threshold_source_digest": "sha256:6eb8797d77cf892afb41f9fb5be0889ccc7504e770f323f7295c66f3ee49ac2d",
        "numerator_cents": 1000,
        "numerator_breakdown": {
          "remaining_owed_cents": 1000,
          "newly_incurred_cents": 0
        },
        "months_remaining": 12,
        "cap_cents": null,
        "cap_dollars_display": null,
        "rounding_mode": "half_up",
        "rounding_precision": "cents",
        "rounding_oracle": "declared -- clause silent; 42 CFR 423.137 states no explicit rounding rule for the division step. Three independent CMS-sourced worked examples (423.137(b)(2): 2000/12=166.67; CMS Final Part Two Guidance section 50.2: 2000/3=666.67, 2000/11=181.82) are each consistent with round-half-up-to-the-cent and no other tested mode.",
        "regulatory_basis": "42 CFR 423.137(a) general; (b)(1)-(2) definitions; (c)(1)(i) first-month formula; (c)(1)(ii) subsequent-month formula; (c)(3) months-remaining includes the current month; (c)(4) impact on true out-of-pocket accumulation.",
        "note": "Verify-only recomputation of the CMS Medicare Prescription Payment Plan monthly cap formula from caller-declared inputs. It does not track a real enrollee's true out-of-pocket accumulation, does not enroll anyone in M3P, and does not assert that any actual participant's bill is correct. Estimate only -- not an official CMS or plan communication, and not financial or legal advice."
      },
      "fixture_oracle_note": "months_remaining=12 is outside the subsequent-month declared domain (1..11 -- a subsequent month can only ever follow a first month, so it never occurs in month 1 of the plan year). Rejected.",
      "golden_hash": "35e9fc697400964c32bdd3519c318dbc639281884ae7cddb4fc84d147b9cf095"
    }
  ]
}