Commune record 01001 · 2018 built-property tax

The COBOL computes €137,415 due. The published port computes €144,041.

Same input record, same rates. France's 2018 property-tax calculator (DGFiP's COBOL) runs unmodified under GnuCOBOL as the answer key. A public Java port, co-authored by the Qwen-Coder agent, passes its own built-property tests (4 of 4) and computes a different total.

Where the port departs from the COBOL

Defect 1 · fee rates

The 3% and 8% fee tiers carry each other's rates.

COBOL 3% tier: 3% and 1%. 8% tier: 8% and 4.4%. EFITA3B8.cob:99–102 @ 6bd40b2 Port 3% tier: 8% and 4.4%. 8% tier: 3% and 1%. BuiltPropertyCalculator.java:24–27 @ 5124d1c

Defect 2 · total before fees

The total before fees leaves out the household-waste tax.

COBOL The waste tax is summed into the 8% tier, which enters the total. EFITA3B8.cob:398–408, 479–480 Port Eight levies are summed; the waste tax is not one of them. RetourB.java:95–102 @ 5124d1c

A commune record is one commune's 2018 REI totals and voted rates, reshaped into one calculator input. These are not household bills. Amounts are whole euros, as the calculator returns them.

Metropolitan France, one shape per commune.

Published port against the COBOL

  • Record differs
  • Record balances

In IBM Bob, Tare held the commit until the port balanced.

One recorded IBM Bob IDE session, 2026-09-26. Bob tried to ship the published port and Tare stopped the commit. Bob weighed the port, sent the fee fields and the total fields to two subagents in parallel, fixed the fee rates, and was stopped again because the port had changed since its weigh. Its first guess for the totals left the weigh red; the COBOL line that explain pointed to gave the right one. Balanced, then the same commit went through.

The national replay, as Tare printed it


  






  
Act two · US Medicare hospice pricing

  
Another agency's COBOL, the same test: CMS's FY2021 hospice pricer is the answer key.

  
Tare runs CMS's own hospice pricer (HOSDR210 and HOSPR210, a U.S. Government work) unmodified under GnuCOBOL, and weighs two Java ports against it, claim by claim, on all fourteen priced fields.

  

  

    
One claim per defect

    

  

  






  
Rerun it.

  
# the 408 Ain commune records, from the committed fixtures (Python only, seconds)
git clone https://github.com/Yazan-O/tare && cd tare
python -m tare reproduce --offline

# every commune, fresh: GnuCOBOL, a JDK 17+ and Maven (cases/taxe_fonciere/README.md)
cd cases/taxe_fonciere && python fetch.py --full && cd full
PYTHONPATH=../../.. python -m tare answer-key
PYTHONPATH=../../.. python -m tare reproduce

# act two: the 5,000 hospice claims, from the committed fixtures (from the repository root)
cd cases/medicare_hospice && PYTHONPATH=../.. python -m tare reproduce --offline






  
Sources and licences.

  
    
    
  • Answer keyDGFiP's 2018 built-property calculator (CTXTA3B, EFITA3B8, EFITAUX2), published by Etalab: etalab/taxe-fonciere @ 6bd40b2, CeCILL-2.1. Fetched at run time, never copied into Tare's repository.
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  • Published portomnipede/taxe-fonciere @ 5124d1c, folder taxe-fonciere-java: one commit by hgseo-cubox-ai, co-authored by Qwen-Coder. CeCILL-2.1, fetched at run time.
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  • Repaired portThe same port with the two fixes above, applied in a build copy by cases/taxe_fonciere/sides/java_port.py.
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  • Input dataREI 2018, Impôts locaux : fichier de recensement des éléments d'imposition à la fiscalité directe locale, Direction générale des Finances publiques, Licence Ouverte / Open Licence 2.0. Commune-level totals and rates, no personal data. The results on this page are derived from it.
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  • Commune shapesADMIN EXPRESS COG, edition 2018-04-03, IGN, Licence Ouverte / Open Licence 2.0. Simplified for this page.
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  • Act two answer keyCMS's FY2021 Hospice Pricer, mainframe release (HOSDR210, HOSPR210, HOSPRATE, CBSA2021), cms.gov, pinned by SHA-256. A work of the U.S. Government (17 U.S.C. §105). Fetched at run time.
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  • Act two portsCMS's Java migration, Hospice Pricer 2.5.1, cms.gov/pricersourcecodesoftware, a FOIA release. The AI-assisted port rcaran/hospice-cms-pricer-java @ 6558476, no licence file; its README claims functional parity for FY1998 to FY2021. Both fetched at run time, never committed. The repairs are line edits checked by SHA-256 (cases/medicare_hospice/sides/ai_port_fixes.json).
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  • Act two claims5,000 claims constructed from public CMS tables (the FY2021 wage-index file, the revenue codes and unit limits in the COBOL), seed 20260926, one dummy provider. No claim is a real claim; no person's data exists. Scale: MedPAC, March 2026 report to Congress, chapter 10.
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  • FontsArchivo and JetBrains Mono, SIL Open Font License 1.1 (Archivo, JetBrains Mono).
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  • Taregithub.com/Yazan-O/tare, MIT.
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