{
  "protocol": {
    "name": "CVP",
    "version": "1.0.0-proposed",
    "revision": "2026-09-13",
    "spec_sha256": "f62725968356c92930531cd6085db76e216da06e95be53d636b0d2cf3218b148",
    "spec": "https://www.calculatorx.com/developers/cvp/spec/1.0"
  },
  "document_status": "proposed",
  "calculator": {
    "id": "fractions",
    "version": "1.0.8",
    "title": "Fractions Calculator",
    "formula_family": "fractions",
    "capability_id": "math.fractions",
    "verification_revision": "2026-10-20.fractions-complete-contract-v2"
  },
  "profile": "core",
  "verified_scope": "operate (+/−/×/÷), simplify, to-dec and from-dec",
  "status": "STALE",
  "verification_status": "VERIFIED",
  "production_freshness": "STALE",
  "overall_trust": "VERIFIED_STALE",
  "runner": {
    "name": "cvp-runner",
    "version": "1.0.0"
  },
  "environment": {
    "runtime": "node",
    "runtime_version": "22.20.0",
    "numeric_model": "IEEE-754 binary64",
    "os": "darwin"
  },
  "suite": {
    "id": "fractions",
    "version": "1.0.8",
    "uri": "https://www.calculatorx.com/evidence/math.fractions/1.0.8.json",
    "verification_revision": "2026-10-20.fractions-complete-contract-v2"
  },
  "obligation_set": [
    "CVP-PROV-01",
    "CVP-MODEL-01",
    "CVP-SCOPE-01",
    "CVP-UNIT-01",
    "CVP-REF-01",
    "CVP-GOLD-01",
    "CVP-BND-01",
    "CVP-INV-01",
    "CVP-NUM-01",
    "CVP-COV-01",
    "CVP-CONTRACT-01",
    "CVP-DEP-01",
    "CVP-ART-01",
    "CVP-PROD-01",
    "CVP-PROP-01",
    "CVP-META-01",
    "CVP-ROUND-01",
    "CVP-IFACE-01"
  ],
  "provenance": {
    "mode": "direct",
    "sources": [
      {
        "label": "Margaret Stevens — The Maths Workbook (University of Oxford)",
        "kind": "other",
        "reference": "Chapter 1, §1: Algebraic Expressions and Fractions; §3: Equations",
        "url": "https://www.some.ox.ac.uk/wp-content/uploads/2024/08/Maths-Workbook.pdf"
      },
      {
        "label": "Python fractions — Rational numbers",
        "kind": "other",
        "reference": "Independent Fraction arithmetic, normalized positive denominator, and the distinction between decimal-string rational conversion and the exact binary fraction represented by a float.",
        "url": "https://docs.python.org/3/library/fractions.html"
      }
    ]
  },
  "controls": {
    "CVP-PROV-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "Sources present on evidence"
    },
    "CVP-MODEL-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "LCD add/sub; product; reciprocal divide"
    },
    "CVP-SCOPE-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "Four rational operations, simplify, rounded to-dec previews and from-dec exact base10 conversion of shortest normalized binary64 decimal. Safe integer inputs/intermediates; reduced from-dec n/d safe. Strict matching aliases, no silent zero/continued-fraction substitution. Independent CPython review fixtures plus separate BigInt fallback; full lexical/browser review recorded separately."
    },
    "CVP-UNIT-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "dimensionless rational"
    },
    "CVP-REF-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "O1 model + O2 expected_values + O2 numerical_behavior"
    },
    "CVP-GOLD-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "20/20 legacy golden; 10/10 oracle-backed numeric"
    },
    "CVP-BND-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "8/8 CVP boundary · 8/8 legacy Evidence boundary"
    },
    "CVP-INV-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "6 Evidence illegal-input + 3/3 oracle-backed error-code (exact_error_match, not ULP)"
    },
    "CVP-NUM-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "max_error_observed_ulp=0; policy declared a priori"
    },
    "CVP-COV-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "8/8 declared partitions (operate:add, operate:subtract, operate:multiply, operate:divide, to-dec, from-dec, simplify, invalid-domain) · 20 legacy golden / 8 CVP boundary unique cases · 6 Evidence invalid-input (may overlap boundary)"
    },
    "CVP-CONTRACT-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "6/6 CVP contract · release-artifacts-aligned=PASS · schema-output-required-declared=PASS · schema-valid-input-executes=PASS · engine-success-output-validates-schema=PASS · schema-rejects-incomplete-input=PASS · rest-success-payload-validates-schema=PASS"
    },
    "CVP-DEP-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "engine fractions; Node binary64"
    },
    "CVP-ART-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "release_integrity.status=verified · digests: artifact_evidence_sha256=Evidence core (Trust freshness) · cvp_evidence_digest=artifacts.evidence_digest (fingerprint v2) · evidence_bundle_sha256=legacy Evidence JSON bytes · evidence_catalog_digest=attested_catalog_sha256 · production_sha256=bound production report · see artifacts.digest_registry"
    },
    "CVP-PROD-01": {
      "result": "PASS",
      "applicability": "required",
      "notes": "Capability production binding: STALE · Site report: stale · STALE (freshness / digest drift after last PASS snapshot) · site report stale · local checks pass · local production checks PASS; capability production binding is not CURRENT — final status must stay STALE, not VERIFIED · attestation_id=28e8435434ae51e54792530f2ecf4b9919e5516fa9bc11e57ba611be3b6b35be · Capability production binding: STALE · Site report: STALE · Public schema 1.0.8 observed · production binding STALE · Semantic contract ✓ · Last attestation PASS · Evidence changed after the last successful production attestation. Re-attestation required. · Public/cache ✓ · Origin ✓ · schema_const=1.0.8 · report output-const=pass · evidence-sha256=pass · semantic-contract=pass · capability-html-public-origin-agree=pass · cvp-manifest-public-origin-agree=pass · cvp-latest-alias-agrees=pass · cvp-immutable-manifest-fetch=pass · cvp-immutable-manifest-sha256=pass · cvp-latest-alias-matches-immutable=pass · calculator-html-cvp-projection=pass · evidence-html-cvp-projection=pass · attested_evidence_sha256=08644336c62608c231689a81851d856365919292294793bf800424200129ec8f · verified_at=2026-10-20T13:37:26.364Z · evidence_attested_at=2026-10-20T13:37:26.364Z · last_confirmed_current_at=2026-10-20T13:37:26.364Z · rendered_at=2026-10-20T13:37:26.364Z · binds=cvp_core_sha256 · Capability production binding: STALE · Site report: STALE · Evidence changed after the last successful production attestation. Re-attestation required.",
      "check_result": "PASS",
      "production_state": "STALE",
      "binding_current": false
    },
    "CVP-DIM-01": {
      "result": "SKIP",
      "applicability": "not_applicable",
      "notes": "Unitless core calculator — no physical dimension algebra"
    },
    "CVP-PROP-01": {
      "result": "PASS",
      "applicability": "applicable",
      "notes": "2/2 property"
    },
    "CVP-META-01": {
      "result": "PASS",
      "applicability": "applicable",
      "notes": "1/1 metamorphic"
    },
    "CVP-ROUND-01": {
      "result": "PASS",
      "applicability": "applicable",
      "notes": "1/1 round-trips"
    },
    "CVP-XCAL-01": {
      "result": "SKIP",
      "applicability": "not_applicable",
      "notes": "No related calculator in the same formula family / no related-identity peers declared — control not in obligation set"
    },
    "CVP-IFACE-01": {
      "result": "PASS",
      "applicability": "applicable",
      "notes": "UI (SSR) · REST · MCP equivalent (MCP uses calc API handler). ui-ssr is query-result HTML, not a live browser session."
    },
    "CVP-ORACLE-01": {
      "result": "SKIP",
      "applicability": "higher_assurance",
      "notes": "O2 present; O3 not required this wave"
    },
    "CVP-EXP-01": {
      "result": "SKIP",
      "applicability": "optional",
      "notes": "named expert review not performed"
    }
  },
  "interfaces": {
    "compared": [
      "ui-ssr",
      "rest",
      "mcp"
    ],
    "result": "PASS",
    "notes": "UI (SSR) · REST · MCP equivalent (MCP uses calc API handler). ui-ssr is query-result HTML, not a live browser session."
  },
  "artifacts": {
    "evidence_bundle_sha256": "6e59342d8afb48a3232d031338f49dc5385e0d71b9c4721068e9efce2d238eb9",
    "evidence_digest": "8059211bd24b2c1ad1066fb97fcb233d1a096ff1a52ea0996e4c522bd85c7df8",
    "production_sha256": "08644336c62608c231689a81851d856365919292294793bf800424200129ec8f",
    "attested_catalog_sha256": "ea3d150b6ba93a699d22c9af0b28bdb648537237c1123f70bb5225f72dbe7283",
    "production_checks": [
      {
        "id": "math.fractions:output-const",
        "status": "pass",
        "detail": "output const 1.0.6 vs capability 1.0.6",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:evidence-sha256",
        "status": "pass",
        "detail": "419407869c99",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:semantic-contract",
        "status": "pass",
        "detail": "32/32",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:capability-html-public-origin-agree",
        "status": "pass",
        "detail": "public 1.0.6 vs origin 1.0.6",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:cvp-manifest-public-origin-agree",
        "status": "pass",
        "detail": "math.fractions/1.0.8/2026-10-20.fractions-complete-contract-v2/core/8059211bd24b",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z",
        "projection_compared": false
      },
      {
        "id": "math.fractions:cvp-latest-alias-agrees",
        "status": "pass",
        "detail": "math.fractions/1.0.8/2026-10-20.fractions-complete-contract-v2/core/8059211bd24b",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z",
        "projection_compared": false
      },
      {
        "id": "math.fractions:cvp-immutable-manifest-fetch",
        "status": "pass",
        "detail": "public=200 origin=200",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:cvp-immutable-manifest-sha256",
        "status": "pass",
        "detail": "b2e72767e4a4",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:cvp-latest-alias-matches-immutable",
        "status": "pass",
        "detail": "math.fractions/1.0.8/2026-10-20.fractions-complete-contract-v2/core/8059211bd24b",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z",
        "projection_compared": false
      },
      {
        "id": "math.fractions:calculator-html-cvp-projection",
        "status": "pass",
        "detail": "matches Trust display",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      },
      {
        "id": "math.fractions:evidence-html-cvp-projection",
        "status": "pass",
        "detail": "matches Trust display",
        "scope": "last_attestation_snapshot",
        "current": false,
        "attestation_binding_current": false,
        "attested_at": "2026-10-20T13:37:26.364Z"
      }
    ],
    "digest_registry": {
      "digest_algorithm": "sha256",
      "canonicalization": "json-sorted-keys-utf8",
      "entries": [
        {
          "name": "cvp_core_sha256",
          "field": "artifacts.cvp_core_sha256",
          "digest_scope": "cvp_verification_fingerprint_v2",
          "value": "8059211bd24b2c1ad1066fb97fcb233d1a096ff1a52ea0996e4c522bd85c7df8",
          "note": "Immutable verification core; excludes attestation/live-status and Evidence contract counts"
        },
        {
          "name": "cvp_evidence_digest",
          "field": "artifacts.evidence_digest",
          "digest_scope": "cvp_verification_fingerprint_v2",
          "value": "8059211bd24b2c1ad1066fb97fcb233d1a096ff1a52ea0996e4c522bd85c7df8",
          "note": "Alias of cvp_core_sha256 (historical field name)"
        },
        {
          "name": "artifact_evidence_sha256",
          "field": "release_integrity.digests.evidence_core_sha256",
          "digest_scope": "evidence_artifact_core",
          "value": "0b0c63acb50d3967532470d204eed573c80924b98a6a12c03432d52d23103cc1",
          "note": "Published Evidence JSON core — Trust freshness / production bind subject"
        },
        {
          "name": "evidence_catalog_digest",
          "field": "artifacts.attested_catalog_sha256",
          "digest_scope": "capability_catalog",
          "value": "ea3d150b6ba93a699d22c9af0b28bdb648537237c1123f70bb5225f72dbe7283",
          "note": "Capability catalog integrity; site-wide, not per-suite fingerprint"
        }
      ]
    },
    "cvp_core_sha256": "8059211bd24b2c1ad1066fb97fcb233d1a096ff1a52ea0996e4c522bd85c7df8"
  },
  "dependencies": [
    {
      "name": "fractions-engine",
      "version": "1.0.8"
    },
    {
      "name": "fractions-reference-oracle",
      "version": "1.0.0"
    },
    {
      "name": "node",
      "version": "22.20.0"
    }
  ],
  "attestation": {
    "status": "STALE",
    "href": "/.well-known/calculatorx-production-attestation.json",
    "id": "28e8435434ae51e54792530f2ecf4b9919e5516fa9bc11e57ba611be3b6b35be",
    "attested_at": "2026-10-20T13:37:26.364Z",
    "last_confirmed_current_at": "2026-10-20T13:37:26.364Z",
    "site_attestation_current": false,
    "capability_attestation_current": false,
    "bound_snapshot_status": "pass",
    "live_report_status": "stale",
    "bound_attested_at": "2026-10-20T06:48:44.084Z",
    "live_updated_at": "2026-10-20T13:33:37.869Z",
    "bound_snapshot": {
      "status": "pass",
      "attested_at": "2026-10-20T06:48:44.084Z",
      "site_stale_count": 3
    },
    "live_site_status": {
      "href": "/.well-known/calculatorx-production-attestation.json"
    },
    "bound_snapshot_site_stale_count": 3,
    "site_stale_capability_count": 3,
    "stale_reason": "Capability production binding: STALE · Site report: STALE · Evidence changed after the last successful production attestation. Re-attestation required.",
    "evidence_attested_at": "2026-10-20T13:37:26.364Z"
  },
  "domain_review": {
    "status": "ABSENT",
    "spec_version": "1.0.8",
    "external_third_party": false,
    "note": "Named expert review not performed"
  },
  "timestamps": {
    "verified_at": "2026-10-20T13:37:26.364Z",
    "generated_at": "2026-10-20T13:37:26.364Z",
    "rendered_at": "2026-10-20T13:37:26.364Z",
    "notes": "verified_at/generated_at mark the first publication of this cvp_core_sha256 (artifacts.evidence_digest alias) for suite verification. evidence_attested_at/attested_at is the first production bind of that core digest. last_confirmed_current_at is the latest site-wide report that still confirms CURRENT. rendered_at is this JSON serialization and is not part of cvp_core_sha256 / evidence_digest. Production attestation binds cvp_core_sha256 (binds evidence_digest). Causal order: verified_at ≤ evidence_attested_at ≤ last_confirmed_current_at. attestation.bound_snapshot.site_stale_count is the site-wide stale capability count at Manifest bind time — not a live value. Fetch attestation.live_site_status.href for the current site report."
  },
  "tests": {
    "golden": {
      "passed": 10,
      "total": 10,
      "failed": 0
    },
    "boundary": {
      "passed": 8,
      "total": 8,
      "failed": 0
    },
    "invalid": {
      "passed": 9,
      "total": 9,
      "failed": 0,
      "comparison": "exact_error_match"
    },
    "property": {
      "passed": 2,
      "total": 2,
      "failed": 0
    },
    "round_trip": {
      "passed": 1,
      "total": 1,
      "failed": 0
    },
    "metamorphic": {
      "passed": 1,
      "total": 1,
      "failed": 0
    },
    "contract": {
      "passed": 6,
      "total": 6,
      "failed": 0
    },
    "cross_interface": {
      "passed": 7,
      "total": 7,
      "failed": 0
    }
  },
  "numerical": {
    "representation": "exact safe-integer rational; decimal preview is rounded binary64",
    "tolerance": {
      "type": "absolute",
      "value": 0,
      "declared_before_evaluation": true,
      "rationale": "Exact n/d, mixed/result type and complete metadata validation. Decimal preview relative budget6e-12 or6e-9 for9-significant-digit scientific text; zero exact. Independent CPython fractions.Fraction fixtures and separate BigInt fallback."
    },
    "max_error_observed": 0
  },
  "coverage": {
    "partitions": [
      {
        "id": "operate:add",
        "description": "Operate +",
        "exercised": true,
        "case_count": 10
      },
      {
        "id": "operate:subtract",
        "description": "Operate -",
        "exercised": true,
        "case_count": 2
      },
      {
        "id": "operate:multiply",
        "description": "Operate *",
        "exercised": true,
        "case_count": 5
      },
      {
        "id": "operate:divide",
        "description": "Operate /",
        "exercised": true,
        "case_count": 2
      },
      {
        "id": "to-dec",
        "description": "Rounded decimal preview",
        "exercised": true,
        "case_count": 2
      },
      {
        "id": "from-dec",
        "description": "Exact normalized decimal conversion",
        "exercised": true,
        "case_count": 6
      },
      {
        "id": "simplify",
        "description": "Simplify",
        "exercised": true,
        "case_count": 8
      },
      {
        "id": "invalid-domain",
        "description": "Invalid inputs",
        "exercised": true,
        "case_count": 9
      }
    ]
  },
  "reference": {
    "items": [
      {
        "class": "O1",
        "reference_scope": "model",
        "scope": "model",
        "label": "Fraction arithmetic with LCD reduction"
      },
      {
        "class": "O2",
        "reference_scope": "expected_values",
        "scope": "expected_values",
        "label": "CPython fractions.Fraction private fixtures plus independent BigInt rational fallback",
        "engine": {
          "name": "fractions-review-cpython",
          "library": "CPython standard-library fractions.Fraction",
          "independent_of_iut": true
        }
      },
      {
        "class": "O2",
        "reference_scope": "numerical_behavior",
        "scope": "numerical_behavior",
        "label": "CPython fractions.Fraction private fixtures plus independent BigInt rational fallback",
        "engine": {
          "name": "fractions-review-cpython",
          "library": "CPython standard-library fractions.Fraction",
          "independent_of_iut": true
        }
      }
    ]
  },
  "links": {
    "legacy_evidence": "https://www.calculatorx.com/evidence/math.fractions/1.0.8.json",
    "evidence_page": "https://www.calculatorx.com/evidence/math.fractions/1.0.8",
    "calculator": "https://www.calculatorx.com/calc/math/fractions",
    "schema": "https://www.calculatorx.com/developers/cvp/schema/cvp-evidence-1.0.json",
    "protocol": "https://www.calculatorx.com/developers/cvp/spec/1.0",
    "manifest": "https://www.calculatorx.com/evidence/math.fractions/1.0.8.cvp.json",
    "manifest_immutable": "https://www.calculatorx.com/evidence/math.fractions/1.0.8/2026-10-20.fractions-complete-contract-v2.cvp.json",
    "manifest_core": "https://www.calculatorx.com/evidence/math.fractions/1.0.8/2026-10-20.fractions-complete-contract-v2.8059211bd24b.cvp.json"
  },
  "disclosure": {
    "policy": "calculatorx-public-evidence-v1",
    "full_validation": "private",
    "representation": "summary"
  }
}