{
  "schema_version": "1.3.0",
  "slug": "when-does-a-nan-propagate-through-aggregation-and-silently-zero-a-sum",
  "title": "When does a NaN propagate through aggregation and silently void a sum?",
  "date_of_record": "2026 November 2",
  "scope": "Applies to floating-point aggregates (sum, mean, min, max) over data that may contain NaN, where the aggregate is reported without an accompanying count of valid inputs. Excludes aggregates that explicitly reject NaN or count non-numeric inputs separately.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-does-a-nan-propagate-through-aggregation-and-silently-zero-a-sum.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-does-a-nan-propagate-through-aggregation-and-silently-zero-a-sum.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-does-a-nan-propagate-through-aggregation-and-silently-zero-a-sum.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 793,
    "python_slice_tokens": 126,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "**Predicate.** NaN is absorbing under IEEE-754 arithmetic: once any term is NaN, the sum, mean, and most aggregates are NaN. The aggregate is sound if and only if NaN either cannot enter or is surfaced as a distinct count rather than baked into the result. **Failure.** A single null numeric — from a join miss, a failed parse, or a division by zero — is coerc...",
    "what_was_observed": "**Signature.** Aggregate value NaN or zero on days when a single input was malformed. Valid input counts unchanged. Recomputation over a filtered set yields a plausible number, which makes the failure look like intermittent data corruption. **Trace.** Daily revenue = sum(line_items). One line has a null price from a partial upstream record. `sum([1.0, 2.0, NaN, 3.0])` is NaN. Serialized to JSON, NaN is not valid JSON...",
    "condition_of_validity": "Aggregates are sound only while at least one holds: 1. **Rejection.** NaN inputs are rejected before aggregation, and the rejection is alerted. 2. **Counting.** The aggregate is accompanied by a count of valid inputs, and any mismatch between expected and valid counts is an alert. 3. **Representation.** Null numerics are represented as absent (null / optiona...",
    "decision_boundary": "- Rejection at input: aggregate reflects only valid data. - Counting alongside aggregate: NaN cannot hide. - No rejection, no counting: a single NaN voids the aggregate. - Rejection plus counting: robust and diagnosable.",
    "operational_effect": "The defect lives in the coercion step between typed inputs and untyped aggregates, which is often implicit in a query engine. Remediation is to make NaN-ness explicit at the boundary and to report counts alongside aggregates. The trap is to wrap the aggregate in a NaN check that substitutes 0. That converts a NaN into a plausible-looking number, which is str..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "8d50af42ead3ea94389267a5b15e0cf4230dc3f5d5c828b340b848e03fa15e8a",
    "verified_classes": [
      "NanPropagationError",
      "AggregateGate"
    ],
    "verified_functions": [
      "dispatch_aggregate_mode",
      "verify"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "NanPropagationError"
    ],
    "sample_fail_closed_invariants": [
      "NaN present and not rejected: aggregate becomes NaN silently",
      "NaN present and no valid-input count: aggregate hides the defect"
    ],
    "stdlib_dependencies": [
      "dataclasses",
      "math"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}