Emergency Fund Sizer mechanism

Model scope

The honest-label statement appropriately identifies this as rule-of-thumb educational guidance and not personalized advice. The specification needs an explicit low/high definition, a months-to-build formula, a required current_save_rate input, validation rules, and a documented role for income stability before implementation.

• The stated formula defines only fund = monthly_expenses × months; it does not explicitly define how low_fund and high_fund are derived, although 3 months and 6 months are implied.
• No formula is provided for months_to_build. A standard interpretation would be target_fund ÷ current_save_rate, but that formula is absent.
• The relationship between the target_months input and the parenthetical typical range of 3–6 months is ambiguous: target_months may be intended to select one value, while low/high appears to require fixed 3- and 6-month endpoints.
• Income stability flag is listed as an input but has no defined effect on the calculation or target-month selection.

Units and conventions

• monthly_essential_expenses is a nonnegative currency amount per month.
• target_months is dimensionless and, for the displayed range, is constrained to 3 through 6 months; low and high use fixed 3-month and 6-month endpoints.
• current_save_rate is required for months_to_build and is a nonnegative currency amount per month.
• All currency inputs must use the same currency and time basis; a weekly or annual saving rate must be converted to a monthly rate before use.
• The test vectors assume the missing standard formula months_to_build = target_fund ÷ current_save_rate.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "monthly_essential_expenses": 2800,
    "target_months": 4,
    "current_save_rate": 700,
    "income_stability_flag": "stable"
  },
  "expected_outputs": {
    "low_fund": 8400,
    "high_fund": 16800,
    "target_fund": 11200,
    "months_to_build": 16
  },
  "working": "low_fund = 2,800 × 3 = 8,400. high_fund = 2,800 × 6 = 16,800. target_fund = 2,800 × 4 = 11,200. months_to_build = 11,200 ÷ 700 = 16 months."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

A zero current save rate produces division by zero for months_to-build and must be rejected or represented as undefined/infinite. The instrument also has a material unit-convention hazard: treating dollar inputs as cents changes every fund target by a factor of 100.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json