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* fix(simplefin): treat Vanguard/Fidelity cost_basis as total when needed PR #1692 normalized SimpleFIN holdings cost_basis under the assumption that the `cost_basis` / `basis` keys carry a per-share value (per the SimpleFIN spec) and only `total_cost` / `value` carry a total position cost. Vanguard and Fidelity violate the spec — they populate `cost_basis` with the *total* (see the payload in #1182). After PR #1692 those holdings get stored with cost_basis = total, and Holding#calculate_trend then computes previous = qty × avg_cost, so the "previous" value is inflated by a factor of qty and an entire investment account renders a phantom return of roughly -(1 − 1/qty), i.e. -97% to -99%. Fix: sanity-check raw cost_basis against the holding's market share price. Let share_price = market_value / qty; the geometric midpoint between "raw is per-share" (raw ≈ share_price) and "raw is total" (raw ≈ qty × share_price) is share_price × √qty. If raw is above the midpoint it is divided by qty; otherwise it is kept as per-share. Falls back to the pre-fix behaviour (trust the spec) when market_value or qty is unavailable, so confidently-correct readings are never made worse. Verified against the reported Vanguard payload (qty=139, cost_basis= 22004.40, market_value=22626.42): normalize_cost_basis now returns $158.31/share, matching 22004.40 / 139, and the phantom -99% return collapses to a realistic ~+2.8%. Per-share readings ($45 cost on a $50 share price) remain untouched. Closes #1718. Refs #1182, #1692. * fixup: replace cost_basis heuristic with institution allowlist Codex and @EdeAbreu23 flagged a real false-positive in the previous geometric-midpoint heuristic: a legitimate per-share `cost_basis` on a holding with a large unrealized loss (e.g. 100 shares with $100/share basis now worth $5/share) trips `share_price × √qty` and gets divided to $1/share — corrupting any standards-compliant brokerage with a big loss. Adopt @EdeAbreu23's safer shape: - total_cost / value: always divide by qty (unchanged from #1692). - cost_basis / basis: keep as-is by default. - Only divide cost_basis / basis when the holding's SimpleFIN account is connected to a known-misbehaving institution. Allowlist starts with `vanguard` and `fidelity`, matched case-insensitively against the account's stored org name and domain. Easy to extend as more brokerages turn up. Trades a small maintenance cost (curated list) for zero risk of corrupting compliant providers. Verified against five scenarios (all expected): Vanguard total in cost_basis (allowlist) → +2.83% Fidelity total in basis (allowlist) → +33.33% Big-loss per-share (Codex case) → -95.0% (preserved) Honest per-share, small loss → +11.11% (unchanged) total_cost on any institution → +11.11% (unchanged) --------- Co-authored-by: plind-junior <plind-junior@users.noreply.github.com>