Rate sanity check, May 2026 (pre-2.0.0)

[lineoffligbot]

Pre-2.0.0 sanity check of v2 blended rates against Wise mid-market. Previous check was #213 (March 2026), before the beta.2 provider expansion.

Method: EUR base, api.frankfurter.dev/v2/rates vs Wise live mid-market, 2026-05-18. Deviation = abs(frankfurter - wise) / wise.

Summary: 156 currencies compared.

Deviation	Count	Share
< 0.1%	52	33%
0.1 to 0.5%	67	43%
0.5 to 1.0%	20	13%
1.0 to 3.0%	14	9%
> 3.0%	3	2%

76% within 0.5%, 89% within 1%.

Anchors (all within 0.12%):

Pair	Frankfurter	Wise	Dev
EUR/USD	1.1639	1.1628	+0.09%
EUR/GBP	0.8706	0.87105	-0.05%
EUR/JPY	184.69	184.795	-0.06%
EUR/CHF	0.91513	0.91415	+0.11%

Outliers. All in the tail are official or institutional rates that diverge from real-time market rates, not data errors. Multi-provider consensus on the same value confirms the rate is faithfully relayed, not a parsing fault.

• EUR/IRR: ~3030% off. Seven providers agree on the Iran official rate; CBR is excluded by consensus. Dual exchange rate system.
• EUR/SYP: ~99% off. Three independent providers (BDI, CBU, NBP) agree on ~133 SYP/EUR, the Syrian official rate. New to coverage since beta.2.
• EUR/BWP: ~3.5% off. Bank of Botswana official rate vs market.
• Caribbean USD-pegged set (BBD, BZD, BSD, XCD, KYD, ERN): ~2% off. Institutional vs market spread on thin pegged currencies.

Verdict: clean. The blend core is sound and the entire >1% tail is known-category official-rate divergence. No data issues found.