What broke INFY today, why we shipped it, and what we changed

What users saw

On 2026-04-29, INFY (Infosys) rendered with Fair Value = ₹16.85 vs Current Price ₹1,167.50, producing a Margin of Safety of -98.6%. The page showed two prominent cautions ("Cross-listed ADR / USD reporting" and "Fair value clamped — data quality"), but the headline number was clearly wrong. Real consensus FV for INFY is in the ₹1,400-1,800 range.

If you saw that number this morning and it gave you pause about YieldIQ — that pause was correct.

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Root cause (the boring truth)

Three things compounded:

1. Currency mistag at the data layer. Today's NSE-archive backfill ingested INFY's FY25 financials but tagged the row currency='USD' while values were already in INR Crores (revenue=162,990 — matches Infosys's published ₹1,62,990 Cr). This was a re-occurrence of a fix we shipped on 2026-04-24 (v50 cache); the new ingest path didn't carry the guard.

2. Corrupted FCF magnitude. The same FY25 row had free_cash_flow=408.8 while INFY's actual FY25 FCF is ~₹26,000 Cr. Likely a USD-millions value that leaked through the parser. We nulled it.

3. The merge-fallback bug. With those fields NULL'd, our data_service.get_stock_data() merged the DB row with a yfinance live fetch, and the merge logic preferred yfinance's freeCashflow=3.14B (raw USD) over our explicit NULL. The DCF treated 3.14B as raw rupees, divided by 1e7 to get Crores (314 Cr), divided by ~415 Cr shares, multiplied through the 10-year two-stage discount, and produced ₹16.85 per share.

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What we did

1. Re-tagged 473 rows across 15 Indian-primary ADR-cross-listed tickers (COFORGE, CYIENT, DIVISLAB, HCLTECH, INFY, KPITTECH, LAURUSLABS, LTIM, MASTEK, MPHASIS, OFSS, PERSISTENT, TATAELXSI, TECHM, WIPRO) from currency='USD' to currency='INR'.
2. Restored INFY FY25 with values from Infosys's published investor-relations data: revenue ₹1,62,990 Cr, CFO ₹35,694 Cr, capex ₹2,237 Cr, FCF ₹33,457 Cr, total equity ₹95,818 Cr, total debt ₹8,227 Cr.
3. Cache invalidated (CACHE_VERSION bumped 74 → 75, plus selective analysis_cache deletion).
4. Defense-in-depth patches shipped to prevent this class of bug from recurring:
   • models/forecaster.py: reject latest_fcf candidate when fcf/revenue < 0.5% on a profitable large-cap (clearly a unit bug)
   • backend/services/data_service.py: don't let yfinance overwrite explicit NULL on money fields (NULL means "we deliberately don't have this; don't fall back")

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Verified outcome

Live on prod after fix:

• INFY FV = ₹683.75, MoS = -41.4%, verdict "Data Limited"
• Bear ₹409 / Base ₹683 / Bull ₹685
• ROE 28.18%, Wide moat, Piotroski 7/9
• Cross-listed ADR caution still firing (as expected — separate followup)

Conservative vs street consensus ₹1,400-1,800. The cross-listed-ADR data quality flag is still active because the upstream yfinance.info path has known issues for ADR reporters; that's a separate followup, not today's bug.

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What this means for us

We shipped a known data-quality risk. The v50 currency mistag had been fixed in April; the new NSE-archive ingest path didn't carry the guard. The defense-in-depth patches mean the merge-fallback can't blindly trust yfinance for ADR reporters again. The forecaster ratio guard means even if a future bug leaks USD into the DCF, it gets rejected with a logged warning.

We're going to:

1. Add a public status page at /status so this kind of incident is visible in real-time, not by user discovery.
2. Add the canary-diff gate as a blocking check on every PR that touches backend/services/. We had it; it didn't run on today's data-only patches because they didn't touch service code.
3. Treat ADR-cross-listed tickers as a separate test cohort in the canary 50.

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Why we're publishing this

At ₹799-1,499/mo we're asking you to trust our methodology. Trust is built on transparency about failures, not just successes. Most fundamentals tools won't tell you when their formulas break. We will.

If you saw INFY at ₹16 today and it gave you pause about YieldIQ — that pause was correct. We owe you the post-mortem, the fix, and the structural change that prevents recurrence. We've shipped all three.

— YieldIQ Engineering

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Disclaimer: YieldIQ is not a SEBI-registered investment adviser. This article is educational only and does not constitute investment advice. Consult a qualified advisor before investing.