From 48b422cba419827f0ac2825bd4c9cc5cbe5d10f3 Mon Sep 17 00:00:00 2001
From: Emil Lerch <emil@lerch.org>
Date: Mon, 6 Jul 2026 12:29:50 -0700
Subject: [PATCH] stock split handling

---
 src/PortfolioData.zig            |  14 +-
 src/analytics/performance.zig    |  11 +-
 src/cache/store.zig              |  16 ++
 src/commands/audit/hygiene.zig   |  21 +++
 src/commands/common.zig          |  15 +-
 src/commands/compare.zig         |   6 +
 src/commands/portfolio.zig       |  28 +++-
 src/commands/snapshot.zig        |   8 +
 src/compare.zig                  | 244 ++++++++++++++++++++++++++++-
 src/format.zig                   |  14 +-
 src/models/classification.zig    |  46 ++++++
 src/models/portfolio.zig         | 213 ++++++++++++++++++++++++-
 src/models/split.zig             |  87 +++++++++++
 src/portfolio_loader.zig         | 258 +++++++++++++++++++++++++++++++
 src/service.zig                  |  62 ++++++++
 src/tui/history_tab.zig          |   8 +
 src/tui/portfolio_tab.zig        |   8 +-
 src/views/compare.zig            |  43 ++++++
 src/views/portfolio_sections.zig |  22 ++-
 19 files changed, 1084 insertions(+), 40 deletions(-)

diff --git a/src/PortfolioData.zig b/src/PortfolioData.zig
index c4ea16f..b02f6a5 100644
--- a/src/PortfolioData.zig
+++ b/src/PortfolioData.zig
@@ -634,13 +634,19 @@ pub fn load(
 
     const pf = self.file.?;
 
-    // ── Compute positions + symbols ──────────────────────────
-    const positions = pf.positions(today, gpa) catch return error.NoAllocations;
-    defer gpa.free(positions);
-
+    // ── Compute symbols + positions ──────────────────────────
+    // Symbols first: the split corpus is fetched per-symbol.
     const syms = pf.stockSymbols(gpa) catch return error.NoAllocations;
     defer gpa.free(syms);
 
+    // Opt-in split adjustment before positions are aggregated, so the
+    // TUI's positions and valuation carry effective shares. No-op
+    // unless `splits_current_through` is set in metadata.srf.
+    portfolio_loader.enrichLotsSplits(self.svc, gpa, pf.lots, syms, self.paths[0], today);
+
+    const positions = pf.positions(today, gpa) catch return error.NoAllocations;
+    defer gpa.free(positions);
+
     // ── Compute watchlist symbols ────────────────────────────
     //
     // Union of caller-supplied watchlist syms (typically from
diff --git a/src/analytics/performance.zig b/src/analytics/performance.zig
index b4b4c20..fe3ee3a 100644
--- a/src/analytics/performance.zig
+++ b/src/analytics/performance.zig
@@ -3,6 +3,7 @@ const Date = @import("../Date.zig");
 const Candle = @import("../models/candle.zig").Candle;
 const Dividend = @import("../models/dividend.zig").Dividend;
 const Split = @import("../models/split.zig").Split;
+const cumulativeSplitRatio = @import("../models/split.zig").cumulativeSplitRatio;
 const portfolio = @import("../models/portfolio.zig");
 
 /// Minimum holding period (in years) before annualizing returns.
@@ -302,13 +303,9 @@ fn priceReturnSnap(
     // Cumulative split adjustment: for each split between start.date
     // (exclusive) and end.date (inclusive), the start price needs to
     // be divided by the cumulative ratio to make it post-split-
-    // equivalent with the end price.
-    var cum_ratio: f64 = 1.0;
-    for (splits) |s| {
-        if (s.date.lessThan(start.date) or s.date.eql(start.date)) continue;
-        if (end.date.lessThan(s.date)) continue;
-        cum_ratio *= s.ratio();
-    }
+    // equivalent with the end price. Shared with lot effective-share
+    // enrichment via `cumulativeSplitRatio` so the two never diverge.
+    const cum_ratio = cumulativeSplitRatio(splits, start.date, end.date);
 
     const adj_start_close = start.close / cum_ratio;
     if (adj_start_close == 0) return null;
diff --git a/src/cache/store.zig b/src/cache/store.zig
index c0443ec..bc0ad30 100644
--- a/src/cache/store.zig
+++ b/src/cache/store.zig
@@ -2879,6 +2879,22 @@ test "portfolio serialize/deserialize round-trip" {
     try std.testing.expectEqualStrings("VTI", portfolio.lots[2].symbol);
 }
 
+test "portfolio: derived split_factor is never serialized into portfolio.srf" {
+    const allocator = std.testing.allocator;
+    // A plain lot (default split_factor == 1.0), as `zfin import` writes.
+    const lots = [_]Lot{
+        .{ .symbol = "AAPL", .shares = 10, .open_date = Date.fromYmd(2024, 1, 2), .open_price = 180.0 },
+    };
+    const data = try serializePortfolio(allocator, &lots);
+    defer allocator.free(data);
+
+    // split_factor is a DERIVED, read-time-only field. At its 1.0 default
+    // it must be omitted from serialization so the user's hand-maintained
+    // portfolio.srf is never polluted with it. (This is the invariant the
+    // whole "immutable lots" design rests on.)
+    try std.testing.expect(std.mem.indexOf(u8, data, "split_factor") == null);
+}
+
 test "portfolio: cash lots without symbol get CASH placeholder" {
     const allocator = std.testing.allocator;
     // Raw SRF with a cash lot that has no symbol field
diff --git a/src/commands/audit/hygiene.zig b/src/commands/audit/hygiene.zig
index 355d53e..d325268 100644
--- a/src/commands/audit/hygiene.zig
+++ b/src/commands/audit/hygiene.zig
@@ -994,6 +994,27 @@ pub fn runHygieneCheck(
         }
     }
 
+    // ── Section 6: Unhandled stock splits ──
+    //
+    // Held symbols with a split AFTER a lot's purchase date that haven't
+    // opted into automatic split adjustment. Each needs a
+    // `splits_current_through` on its metadata.srf row, or its shares
+    // (and every value derived from them) are misstated across the
+    // split. Cache-only detection; silent when everything is handled.
+    if (portfolio.stockSymbols(allocator)) |split_syms| {
+        defer allocator.free(split_syms);
+        const unhandled = cli.findUnhandledSplits(svc, allocator, portfolio.lots, split_syms, portfolio_path, as_of);
+        defer allocator.free(unhandled);
+        if (unhandled.len > 0) {
+            try out.print("\n", .{});
+            try cli.printFg(out, color, cli.CLR_MUTED, "  Unhandled stock splits\n", .{});
+            for (unhandled) |nudge| {
+                try out.print("    {s}: stock split on {f}\n", .{ nudge.symbol, nudge.date });
+                try cli.printFg(out, color, cli.CLR_MUTED, "      Add 'splits_current_through::YYYY-MM-DD' (your reconcile date) to {s}'s metadata.srf row.\n", .{nudge.symbol});
+            }
+        }
+    } else |_| {}
+
     try out.print("\n", .{});
 }
 
diff --git a/src/commands/common.zig b/src/commands/common.zig
index f432ccf..07d8d04 100644
--- a/src/commands/common.zig
+++ b/src/commands/common.zig
@@ -398,6 +398,7 @@ pub const PortfolioData = portfolio_loader.PortfolioData;
 pub const loadPortfolioFromConfig = portfolio_loader.loadPortfolioFromConfig;
 pub const loadPortfolioFromPaths = portfolio_loader.loadPortfolioFromPaths;
 pub const buildPortfolioData = portfolio_loader.buildPortfolioData;
+pub const findUnhandledSplits = portfolio_loader.findUnhandledSplits;
 
 /// Resolve `-p`/`--portfolio` patterns through `ctx`, then load the
 /// union of all matched portfolio files. The one-stop loader for
@@ -414,13 +415,23 @@ pub const buildPortfolioData = portfolio_loader.buildPortfolioData;
 /// `loadPortfolioFromConfig`, so the resulting `LoadedPortfolio`
 /// is byte-identical regardless of which surface invoked it.
 pub fn loadPortfolio(ctx: *framework.RunCtx, as_of: zfin.Date) ?LoadedPortfolio {
-    return portfolio_loader.loadPortfolioFromConfig(
+    var loaded = portfolio_loader.loadPortfolioFromConfig(
         ctx.io,
         ctx.allocator,
         ctx.config,
         ctx.globals.portfolio_patterns,
         as_of,
-    );
+    ) orelse return null;
+
+    // Opt-in stock-split adjustment: makes `loaded.positions` (and the
+    // shared lot slice) carry effective shares when the user has set
+    // `splits_current_through` in metadata.srf. No-op otherwise, so
+    // every existing portfolio behaves exactly as before.
+    if (ctx.svc) |svc| {
+        portfolio_loader.applySplitAdjustment(svc, ctx.allocator, &loaded, as_of);
+    }
+
+    return loaded;
 }
 
 // ── As-of date parsing (shared by CLI --as-of and TUI date popup) ──
diff --git a/src/commands/compare.zig b/src/commands/compare.zig
index b888819..cb039ea 100644
--- a/src/commands/compare.zig
+++ b/src/commands/compare.zig
@@ -448,6 +448,12 @@ pub fn run(ctx: *framework.RunCtx, parsed: ParsedArgs) !void {
     else
         .{ .date_at_or_before = now_date_requested };
 
+    // Opt-in: bring the "then" snapshot into the current split basis so
+    // a split between the two dates doesn't read as a phantom position
+    // change against the (already effective-share) live side. No-op
+    // unless `splits_current_through` is set in metadata.srf.
+    compare_core.adjustThenForSplits(svc, allocator, &then_side.map, portfolio_path, then_date, now_date);
+
     if (now_is_live) {
         // Borrow the pre-loaded live_data to build the LiveSide
         // map. When `live_data` is null (loadLiveData returned
diff --git a/src/commands/portfolio.zig b/src/commands/portfolio.zig
index 30dc800..f2f7c7d 100644
--- a/src/commands/portfolio.zig
+++ b/src/commands/portfolio.zig
@@ -640,7 +640,7 @@ pub fn printLotRow(as_of: zfin.Date, out: *std.Io.Writer, color: bool, lot: zfin
     const acct_col: []const u8 = lot.account orelse "";
 
     const use_price = lot.close_price orelse current_price;
-    const gl = lot.shares * (use_price - lot.open_price);
+    const gl = lot.effectiveShares() * (use_price - lot.effectiveOpenPrice());
     const lot_gl_abs = if (gl >= 0) gl else -gl;
     const lot_sign: []const u8 = if (gl >= 0) "+" else "-";
 
@@ -651,14 +651,14 @@ pub fn printLotRow(as_of: zfin.Date, out: *std.Io.Writer, color: bool, lot: zfin
     try views.writeCol(out, status_str, w.symbol_w, false);
     try out.writeByte(' ');
     var shares_buf: [48]u8 = undefined;
-    const shares_str = std.fmt.bufPrint(&shares_buf, "{d:.1}", .{lot.shares}) catch "?";
+    const shares_str = std.fmt.bufPrint(&shares_buf, "{d:.1}", .{lot.effectiveShares()}) catch "?";
     try views.writeCol(out, shares_str, w.shares_w, true);
     try out.writeByte(' ');
-    try out.print("{f}", .{Money.from(lot.open_price).padRight(w.price_w)});
+    try out.print("{f}", .{Money.from(lot.effectiveOpenPrice()).padRight(w.price_w)});
     try out.writeByte(' ');
     try views.writeCol(out, "", w.price_w, true); // blank current-price cell
     try out.writeByte(' ');
-    try out.print("{f}", .{Money.from(lot.shares * use_price).padRight(w.value_w)});
+    try out.print("{f}", .{Money.from(lot.effectiveShares() * use_price).padRight(w.value_w)});
     try out.writeByte(' ');
     try cli.reset(out, color);
     // Colored gain/loss cell.
@@ -1293,3 +1293,23 @@ test "parseArgs: --expired without value errors" {
     const args = [_][]const u8{"--expired"};
     try std.testing.expectError(error.InvalidExpiredValue, parseArgs(&ctx, &args));
 }
+
+test "printLotRow: renders effective (split-adjusted) shares, cost, and value" {
+    var lots = [_]zfin.Lot{
+        .{ .symbol = "NVDA", .shares = 100, .open_date = zfin.Date.fromYmd(2020, 1, 1), .open_price = 40, .split_factor = 10.0 },
+    };
+    const no_allocs: []const zfin.valuation.Allocation = &.{};
+    const no_watch: []const []const u8 = &.{};
+    const widths = views.computeWidths(no_allocs, &lots, 0, 0, no_watch, null);
+
+    var buf: [512]u8 = undefined;
+    var w = std.Io.Writer.fixed(&buf);
+    try printLotRow(zfin.Date.fromYmd(2026, 1, 1), &w, false, lots[0], 120.0, widths);
+    const out = w.buffered();
+
+    // Effective shares 1000.0 (not raw 100.0), effective cost $4.00
+    // (40 / 10), market value 1000 * 120 = $120,000.
+    try std.testing.expect(std.mem.indexOf(u8, out, "1000.0") != null);
+    try std.testing.expect(std.mem.indexOf(u8, out, "$4.00") != null);
+    try std.testing.expect(std.mem.indexOf(u8, out, "120,000") != null);
+}
diff --git a/src/commands/snapshot.zig b/src/commands/snapshot.zig
index 726ea39..619b9e0 100644
--- a/src/commands/snapshot.zig
+++ b/src/commands/snapshot.zig
@@ -682,6 +682,14 @@ fn captureSnapshot(
     // Use `positionsAsOf(as_of)` rather than `positions()` so historical
     // backfills correctly count lots that were held on `as_of`
     // regardless of whether they're open today.
+
+    // Opt-in split adjustment, as-of the snapshot date so a back-dated
+    // capture applies only the splits that had occurred by then.
+    // Effective shares flow into the summary (via positionsAsOf) and
+    // into each per-lot `value` (via marketValue); the stored `.shares`
+    // field stays RAW - a snapshot is a frozen historical record.
+    portfolio_loader.enrichLotsSplits(svc, allocator, portfolio.lots, syms, portfolio_path, as_of);
+
     const positions = try portfolio.positionsAsOf(allocator, as_of);
     defer allocator.free(positions);
 
diff --git a/src/compare.zig b/src/compare.zig
index a2147a0..1a4c94d 100644
--- a/src/compare.zig
+++ b/src/compare.zig
@@ -37,6 +37,7 @@ const zfin = @import("root.zig");
 const history = @import("history.zig");
 const snapshot_model = @import("models/snapshot.zig");
 const view = @import("views/compare.zig");
+const cumulativeSplitRatio = @import("models/split.zig").cumulativeSplitRatio;
 
 pub const Date = zfin.Date;
 
@@ -88,9 +89,22 @@ pub fn loadSnapshotSide(
 // ── Stock aggregation (compare-view shape) ───────────────────
 
 /// Walk a snapshot's lot rows, filter to `security_type == "Stock"`,
-/// and group by symbol into `out_map`. Shares are summed; price is
-/// taken from the first lot seen (all stock lots of a symbol share
-/// the same `price` field in a given snapshot).
+/// and group by symbol into `out_map`.
+///
+/// Shares are the EFFECTIVE (split-adjusted) count, recovered as
+/// `value / price` rather than read from the raw `.shares` field. A
+/// snapshot stores `.shares` as the immutable as-transacted count but
+/// `.value` as the split-adjusted market value (see the "Share model"
+/// block in `models/portfolio.zig` and `snapshot.buildSnapshot`), so
+/// once a split has been applied at capture, `raw_shares * price` no
+/// longer equals the stored value. Deriving `value / price` keeps this
+/// side self-consistent (shares x price == value) and in the snapshot's
+/// own date-epoch effective basis, which `adjustThenForSplits` then
+/// brings forward. For a plain pre-feature snapshot `value == shares x
+/// price`, so this degrades exactly to the raw share count.
+///
+/// Price is taken from the first lot seen (all stock lots of a symbol
+/// share the same `price` field in a given snapshot).
 ///
 /// Lives here rather than in `history.zig` because it emits a
 /// `view.HoldingMap` - a compare-view-shaped type. The projection-
@@ -106,11 +120,15 @@ pub fn aggregateSnapshotStocks(
     for (snap.lots) |lot| {
         if (!std.mem.eql(u8, lot.security_type, "Stock")) continue;
         const price = lot.price orelse continue;
+        // Effective shares = value / price (split-adjusted). Guard a
+        // zero price (bad data) by falling back to the raw count so we
+        // never divide by zero.
+        const eff_shares = if (price != 0) lot.value / price else lot.shares;
         if (out_map.getPtr(lot.symbol)) |h| {
-            h.shares += lot.shares;
+            h.shares += eff_shares;
             // price is already set from first-seen; leave it.
         } else {
-            try out_map.put(lot.symbol, .{ .shares = lot.shares, .price = price });
+            try out_map.put(lot.symbol, .{ .shares = eff_shares, .price = price });
         }
     }
 }
@@ -137,13 +155,75 @@ pub fn aggregateLiveStocks(
         const raw_price = prices.get(sym) orelse continue;
         const eff_price = lot.effectivePrice(raw_price, false);
         if (out_map.getPtr(sym)) |h| {
-            h.shares += lot.shares;
+            h.shares += lot.effectiveShares();
         } else {
-            try out_map.put(sym, .{ .shares = lot.shares, .price = eff_price });
+            try out_map.put(sym, .{ .shares = lot.effectiveShares(), .price = eff_price });
         }
     }
 }
 
+/// Opt-in: bring a "then" snapshot map into the "now" split basis so a
+/// split between the two compared dates doesn't read as a phantom
+/// position change (or a phantom price crash) against the "now" side.
+///
+/// Both snapshot sides already carry EFFECTIVE shares in their own
+/// date-epoch (see `aggregateSnapshotStocks`), so all this does is
+/// bridge the epoch gap between `then_date` and `now_date`: it multiplies
+/// shares by, and divides price by, the cumulative split ratio in the
+/// window `(max(cutover, then_date), now_date]`. Starting at `then_date`
+/// (not the cutover) is what makes a snapshot captured AFTER a split a
+/// no-op instead of double-applying that split; the cutover only clamps
+/// the window so we never reach behind the user's reconcile baseline.
+/// A held-throughout position then nets to zero share change.
+///
+/// Per-symbol: only symbols that carry a `splits_current_through`
+/// cutover are adjusted; the rest are left untouched. No-op when nothing
+/// has opted in or no split applies. Shared by the CLI `compare` command
+/// and the TUI history tab. Only meaningful for a SNAPSHOT "then" side;
+/// when "then" is the live portfolio it is already in the current basis,
+/// so callers skip it.
+///
+/// Known limitation: a "then" snapshot from BEFORE the cutover, or a
+/// stale pre-feature snapshot that under-recorded value, can't be
+/// perfectly reconciled from recorded data - those fall back to
+/// cutover-basis / recorded value.
+pub fn adjustThenForSplits(
+    svc: *zfin.DataService,
+    allocator: std.mem.Allocator,
+    then_map: *view.HoldingMap,
+    portfolio_path: []const u8,
+    then_date: zfin.Date,
+    now_date: zfin.Date,
+) void {
+    var cutovers = svc.loadSplitsCutovers(allocator, portfolio_path);
+    defer {
+        var kit = cutovers.keyIterator();
+        while (kit.next()) |k| allocator.free(k.*);
+        cutovers.deinit();
+    }
+    if (cutovers.count() == 0) return;
+
+    var factors = std.StringHashMap(f64).init(allocator);
+    defer factors.deinit();
+    var it = then_map.iterator();
+    while (it.next()) |e| {
+        const sym = e.key_ptr.*;
+        const cutover = cutovers.get(sym) orelse continue; // per-symbol opt-in
+        const fr = svc.getSplits(sym, .{}) catch continue;
+        defer fr.deinit();
+        // Bring the "then" holdings forward from the snapshot's own date
+        // to `now_date`. Start the window at max(cutover, then_date): the
+        // snapshot already reflects every split up to then_date, and raw
+        // shares are current only through the cutover, so a split before
+        // either boundary must not be re-applied. Mirrors enrichSplits'
+        // max(cutover, open_date) clamp so the two never diverge.
+        const after = if (cutover.lessThan(then_date)) then_date else cutover;
+        const f = cumulativeSplitRatio(fr.data, after, now_date);
+        if (f != 1.0) factors.put(sym, f) catch continue;
+    }
+    view.forwardAdjustThen(then_map, &factors);
+}
+
 // ── Tests ────────────────────────────────────────────────────
 
 const testing = std.testing;
@@ -226,6 +306,52 @@ test "aggregateSnapshotStocks: sums shares, filters non-stock, takes first price
     try testing.expectEqual(@as(f64, 25), (map.get("MSFT") orelse unreachable).shares);
 }
 
+test "aggregateSnapshotStocks: derives effective shares from value/price (split-captured snapshot)" {
+    // A snapshot captured with split adjustment on stores RAW shares
+    // (100) but the split-adjusted market VALUE (1000 effective shares
+    // x $120 = $120,000). The compare map must reflect the effective
+    // 1000 shares (value / price), not the raw 100 - otherwise a split
+    // reads as a phantom 10x position change against the effective-share
+    // "now" side. For a plain (pre-feature) snapshot value == shares x
+    // price, so this degrades to raw shares and is backward-compatible.
+    var map: view.HoldingMap = .init(testing.allocator);
+    defer map.deinit();
+
+    const lots = [_]snapshot_model.LotRow{
+        .{
+            .symbol = "NVDA",
+            .lot_symbol = "NVDA",
+            .account = "Sample Brokerage",
+            .security_type = "Stock",
+            .shares = 100, // RAW, as transacted (immutable historical fact)
+            .open_price = 40,
+            .cost_basis = 4000,
+            .value = 120000, // effective: 1000 shares x $120
+            .price = 120.0,
+        },
+    };
+    const snap = snapshot_model.Snapshot{
+        .meta = .{
+            .snapshot_version = 1,
+            .as_of_date = Date.fromYmd(2024, 9, 1),
+            .captured_at = 0,
+            .zfin_version = "test",
+            .stale_count = 0,
+        },
+        .totals = &.{},
+        .tax_types = &.{},
+        .accounts = &.{},
+        .lots = @constCast(&lots),
+    };
+
+    try aggregateSnapshotStocks(&snap, &map);
+
+    const h = map.get("NVDA") orelse return error.TestUnexpectedResult;
+    // Effective shares = value / price = 120000 / 120 = 1000, not raw 100.
+    try testing.expectApproxEqAbs(@as(f64, 1000), h.shares, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 120.0), h.price, 0.001);
+}
+
 test "loadSnapshotSide: happy path builds a SnapshotSide with aggregated holdings" {
     const io = std.testing.io;
     var tmp = std.testing.tmpDir(.{});
@@ -417,3 +543,107 @@ test "aggregateLiveStocks: empty portfolio yields empty map" {
     try aggregateLiveStocks(today, &portfolio, &prices, &map);
     try testing.expectEqual(@as(u32, 0), map.count());
 }
+
+test "adjustThenForSplits: forward-adjusts then map from seeded cache + cutover" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    // metadata.srf with a per-symbol cutover before the split -> applied.
+    try tmp.dir.writeFile(io, .{
+        .sub_path = "metadata.srf",
+        .data = "#!srfv1\nsymbol::NVDA,splits_current_through::2024-01-01\n",
+    });
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const dir_len = try tmp.dir.realPathFile(io, ".", &path_buf);
+    const dir = path_buf[0..dir_len];
+
+    // Seed NVDA 10:1 (2024-06-10).
+    var store = zfin.cache.Store.init(io, allocator, dir);
+    var splits = [_]zfin.Split{.{ .date = zfin.Date.fromYmd(2024, 6, 10), .numerator = 10, .denominator = 1 }};
+    store.write(zfin.Split, "NVDA", splits[0..], .{ .seconds = zfin.cache.Ttl.splits });
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const anchor = try std.fs.path.join(allocator, &.{ dir, "portfolio.srf" });
+    defer allocator.free(anchor);
+
+    var then_map: view.HoldingMap = .init(allocator);
+    defer then_map.deinit();
+    try then_map.put("NVDA", .{ .shares = 100, .price = 600 });
+
+    // then snapshot taken 2024-03-01 (before the 2024-06-10 split);
+    // now_date after the split: factor 10 -> 100 -> 1000 shares, $600 -> $60.
+    adjustThenForSplits(&svc, allocator, &then_map, anchor, zfin.Date.fromYmd(2024, 3, 1), zfin.Date.fromYmd(2026, 1, 1));
+    try testing.expectApproxEqAbs(@as(f64, 1000), then_map.get("NVDA").?.shares, 0.01);
+    try testing.expectApproxEqAbs(@as(f64, 60.0), then_map.get("NVDA").?.price, 0.01);
+}
+
+test "adjustThenForSplits: no cutover leaves then map untouched" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+    // No metadata.srf at all -> opt-in off.
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const dir_len = try tmp.dir.realPathFile(io, ".", &path_buf);
+    const dir = path_buf[0..dir_len];
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const anchor = try std.fs.path.join(allocator, &.{ dir, "portfolio.srf" });
+    defer allocator.free(anchor);
+
+    var then_map: view.HoldingMap = .init(allocator);
+    defer then_map.deinit();
+    try then_map.put("NVDA", .{ .shares = 100, .price = 600 });
+
+    adjustThenForSplits(&svc, allocator, &then_map, anchor, zfin.Date.fromYmd(2024, 3, 1), zfin.Date.fromYmd(2026, 1, 1));
+    try testing.expectApproxEqAbs(@as(f64, 100), then_map.get("NVDA").?.shares, 0.01);
+    try testing.expectApproxEqAbs(@as(f64, 600.0), then_map.get("NVDA").?.price, 0.01);
+}
+
+test "adjustThenForSplits: then snapshot captured after the split is not double-applied" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    // Same opt-in + seeded 10:1 split (2024-06-10) as the forward case.
+    try tmp.dir.writeFile(io, .{
+        .sub_path = "metadata.srf",
+        .data = "#!srfv1\nsymbol::NVDA,splits_current_through::2024-01-01\n",
+    });
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const dir_len = try tmp.dir.realPathFile(io, ".", &path_buf);
+    const dir = path_buf[0..dir_len];
+
+    var store = zfin.cache.Store.init(io, allocator, dir);
+    var splits = [_]zfin.Split{.{ .date = zfin.Date.fromYmd(2024, 6, 10), .numerator = 10, .denominator = 1 }};
+    store.write(zfin.Split, "NVDA", splits[0..], .{ .seconds = zfin.cache.Ttl.splits });
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const anchor = try std.fs.path.join(allocator, &.{ dir, "portfolio.srf" });
+    defer allocator.free(anchor);
+
+    // A "then" snapshot captured 2024-08-01 - AFTER the split - already
+    // holds effective shares (1000) at the post-split price ($120). The
+    // split predates this snapshot, so bringing it forward to now must
+    // be a no-op: the window starts at the snapshot's own date, not the
+    // cutover. Applying the split again would 10x it into a phantom.
+    var then_map: view.HoldingMap = .init(allocator);
+    defer then_map.deinit();
+    try then_map.put("NVDA", .{ .shares = 1000, .price = 120 });
+
+    adjustThenForSplits(&svc, allocator, &then_map, anchor, zfin.Date.fromYmd(2024, 8, 1), zfin.Date.fromYmd(2026, 1, 1));
+    try testing.expectApproxEqAbs(@as(f64, 1000), then_map.get("NVDA").?.shares, 0.01);
+    try testing.expectApproxEqAbs(@as(f64, 120.0), then_map.get("NVDA").?.price, 0.01);
+}
diff --git a/src/format.zig b/src/format.zig
index 00f038f..cec3b0a 100644
--- a/src/format.zig
+++ b/src/format.zig
@@ -696,7 +696,7 @@ pub fn aggregateDripLots(as_of: Date, lots: []const Lot) DripAggregation {
         const is_lt = std.mem.eql(u8, capitalGainsIndicator(as_of, lot.open_date), "LT");
         const bucket: *DripSummary = if (is_lt) &result.lt else &result.st;
         bucket.lot_count += 1;
-        bucket.shares += lot.shares;
+        bucket.shares += lot.effectiveShares();
         bucket.cost += lot.costBasis();
         if (bucket.first_date == null or lot.open_date.days < bucket.first_date.?.days)
             bucket.first_date = lot.open_date;
@@ -1230,6 +1230,18 @@ test "aggregateDripLots empty" {
     try std.testing.expect(agg.lt.isEmpty());
 }
 
+test "aggregateDripLots: uses split-adjusted effective shares, raw cost basis" {
+    var lots = [_]Lot{
+        .{ .symbol = "NVDA", .shares = 2, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 40, .drip = true, .split_factor = 10.0 },
+    };
+    const agg = aggregateDripLots(Date.fromYmd(2026, 1, 1), &lots);
+    // Held > 1yr -> LT. Effective shares = 2 * 10 = 20; cost basis stays
+    // raw = 2 * 40 = 80; avgCost = 80/20 = 4.0 (effective per-share).
+    try std.testing.expectApproxEqAbs(@as(f64, 20), agg.lt.shares, 0.001);
+    try std.testing.expectApproxEqAbs(@as(f64, 80), agg.lt.cost, 0.001);
+    try std.testing.expectApproxEqAbs(@as(f64, 4.0), agg.lt.avgCost(), 0.01);
+}
+
 test "fmtContractLine" {
     var buf: [128]u8 = undefined;
     const contract = OptionContract{
diff --git a/src/models/classification.zig b/src/models/classification.zig
index cbc9fa4..a3fc18a 100644
--- a/src/models/classification.zig
+++ b/src/models/classification.zig
@@ -11,6 +11,7 @@
 ///   symbol::02315N600,asset_class::Bonds,pct:num:15
 const std = @import("std");
 const srf = @import("srf");
+const Date = @import("../Date.zig");
 
 /// A single classification entry for a symbol.
 pub const ClassificationEntry = struct {
@@ -36,6 +37,16 @@ pub const ClassificationEntry = struct {
     asset_class: ?[]const u8 = null,
     /// Percentage weight for this entry (0-100). Default 100 for single-class assets.
     pct: f64 = 100.0,
+    /// Per-symbol opt-in for automatic stock-split adjustment. When set,
+    /// `enrichSplits` auto-applies splits for THIS symbol that occur
+    /// AFTER this date (splits on/before it are assumed already baked
+    /// into the recorded share counts - e.g. a lot entered post-split).
+    /// Null (the default, and the state of every metadata.srf that
+    /// predates this feature) means split adjustment is OFF for the
+    /// symbol - today's exact behavior. It lives per-symbol because
+    /// "when did I last make these shares current" is a fact about the
+    /// individual holding, not the whole portfolio.
+    splits_current_through: ?Date = null,
 };
 
 /// Parsed classification data for the entire portfolio.
@@ -95,6 +106,7 @@ pub fn parseClassificationFile(allocator: std.mem.Allocator, data: []const u8) !
             .geo = if (entry.geo) |g| try allocator.dupe(u8, g) else null,
             .asset_class = if (entry.asset_class) |a| try allocator.dupe(u8, a) else null,
             .pct = entry.pct,
+            .splits_current_through = entry.splits_current_through,
         });
     }
 
@@ -272,6 +284,40 @@ test "parse classification file: bucket round-trips" {
     try std.testing.expectEqualStrings("Equity / Corporate", cm.entries[0].sector.?);
 }
 
+test "parse classification file: per-symbol splits_current_through parses; absent stays null" {
+    const data =
+        \\#!srfv1
+        \\symbol::AMZN,name::Amazon,sector::Technology,geo::US,asset_class::US Large Cap,splits_current_through::2024-06-01
+        \\symbol::NVDA,sector::Technology,geo::US,asset_class::US Large Cap
+    ;
+    const allocator = std.testing.allocator;
+    var cm = try parseClassificationFile(allocator, data);
+    defer cm.deinit();
+
+    try std.testing.expectEqual(@as(usize, 2), cm.entries.len);
+
+    // AMZN carries a per-symbol cutover; NVDA (no field) stays null.
+    try std.testing.expectEqualStrings("AMZN", cm.entries[0].symbol);
+    try std.testing.expect(cm.entries[0].splits_current_through != null);
+    try std.testing.expect(cm.entries[0].splits_current_through.?.eql(Date.fromYmd(2024, 6, 1)));
+
+    try std.testing.expectEqualStrings("NVDA", cm.entries[1].symbol);
+    try std.testing.expect(cm.entries[1].splits_current_through == null);
+}
+
+test "parse classification file: legacy row without the field parses (backward compat)" {
+    const data =
+        \\#!srfv1
+        \\symbol::AMZN,sector::Technology,geo::US,asset_class::US Large Cap
+    ;
+    const allocator = std.testing.allocator;
+    var cm = try parseClassificationFile(allocator, data);
+    defer cm.deinit();
+
+    try std.testing.expectEqual(@as(usize, 1), cm.entries.len);
+    try std.testing.expect(cm.entries[0].splits_current_through == null);
+}
+
 test "resolveSecurityName: metadata name wins" {
     var entries = [_]ClassificationEntry{
         .{ .symbol = "AMZN", .name = "Amazon" },
diff --git a/src/models/portfolio.zig b/src/models/portfolio.zig
index fb48a8c..e785d8b 100644
--- a/src/models/portfolio.zig
+++ b/src/models/portfolio.zig
@@ -1,6 +1,8 @@
 const std = @import("std");
 const Date = @import("../Date.zig");
 const Candle = @import("candle.zig").Candle;
+const split = @import("split.zig");
+const Split = split.Split;
 
 // ── Pricing model ────────────────────────────────────────────
 //
@@ -64,6 +66,52 @@ const Candle = @import("candle.zig").Candle;
 // + `manual_set`, audit via inline `prices.get(sym) orelse avg_cost`
 // with a matching `is_preadjusted` flag per branch.
 
+// ── Share model (split adjustment) ──────────────────────────
+//
+// `lot.shares` and `lot.open_price` are IMMUTABLE HISTORICAL FACTS:
+// the count and per-share price exactly as the lot was transacted, as
+// written in portfolio.srf. We never rewrite them for a stock split
+// (that would corrupt the git history the contributions/compare/audit
+// commands read). Instead, `lot.split_factor` is a DERIVED multiplier,
+// populated on read by `enrichSplits` from the fetched split corpus:
+//
+//   effective_shares    = shares * split_factor
+//   effective_open_price = open_price / split_factor
+//
+// so cost basis stays split-invariant
+// (`effective_shares * effective_open_price == shares * open_price`).
+//
+// `split_factor` is analogous to `price_ratio`: a derived multiplier,
+// default 1.0 (no adjustment), applied via accessors. It is set ONLY
+// by `enrichSplits`, and ONLY for symbols the user has opted in with a
+// per-symbol `splits_current_through::DATE` on that symbol's
+// metadata.srf row. Symbols without it stay at 1.0 everywhere and every
+// path below behaves exactly as it did before this feature existed.
+//
+// ## The rule - when to use which
+//
+// Use `effectiveShares()` / `effectiveOpenPrice()` (NOT raw
+// `shares`/`open_price`) anywhere a share count is:
+//   - multiplied by a current-or-later price (market value, gain/loss
+//     vs current price),
+//   - summed into a current holdings/position total, or
+//   - shown on screen.
+// `marketValue` already routes through `effectiveShares()`, and
+// `positionsAsOf`/`positionsForAccount` sum `effectiveShares()`, so
+// anything flowing through positions or `marketValue` is correct for
+// free.
+//
+// Use RAW `shares`/`open_price` (they are correct precisely because
+// they are split-invariant or historical) for:
+//   - cost basis and realized P&L (`costBasis`, `realizedGainLoss`),
+//   - the contributions diff (a split must NOT read as a contribution;
+//     it diffs raw declared shares across git revisions),
+//   - the frozen `.shares` field written into a snapshot record (a
+//     historical fact; its `.value` is computed effective instead).
+//
+// If you are reading `lot.shares` directly in NEW code, you had
+// better be in the RAW list above - otherwise use `effectiveShares()`.
+
 // ── Money-market / stable-NAV classification ────────────────
 //
 // Centralized so that audit/, the Fidelity/Schwab parsers, and the
@@ -206,6 +254,16 @@ pub const Lot = struct {
     /// institutional NAV. E.g. if VTTHX (investor) is $27.78 and the institutional
     /// class trades at $144.04, price_ratio = 144.04 / 27.78 ≈ 5.185.
     price_ratio: f64 = 1.0,
+    /// DERIVED split-adjustment multiplier - NOT hand-edited, NOT a
+    /// pricing/classification key. Default 1.0 = no adjustment.
+    /// Populated on read by `enrichSplits` (opt-in via a per-symbol
+    /// `splits_current_through` on the symbol's metadata.srf row); see
+    /// the "Share model"
+    /// block at the top of this file. `effectiveShares()` multiplies by
+    /// it; `effectiveOpenPrice()` divides by it. Left at its 1.0 default
+    /// it is omitted from SRF serialization, so it never touches the
+    /// user's portfolio.srf (guarded by a round-trip test in store.zig).
+    split_factor: f64 = 1.0,
     /// Underlying stock symbol for option lots (e.g. "AMZN").
     underlying: ?[]const u8 = null,
     /// Strike price for option lots.
@@ -289,10 +347,28 @@ pub const Lot = struct {
         return true;
     }
 
+    /// Cost basis: RAW shares x RAW open_price. Split-invariant
+    /// (`effectiveShares * effectiveOpenPrice == shares * open_price`),
+    /// so this deliberately stays on the raw fields. See "Share model".
     pub fn costBasis(self: Lot) f64 {
         return self.shares * self.open_price;
     }
 
+    /// Split-adjusted share count: raw `shares` scaled by the derived
+    /// `split_factor`. Use this (never raw `shares`) anywhere shares get
+    /// multiplied by a current-or-later price, summed into current
+    /// holdings, or displayed. See the "Share model" block above.
+    pub fn effectiveShares(self: Lot) f64 {
+        return self.shares * self.split_factor;
+    }
+
+    /// Split-adjusted per-share cost: raw `open_price` divided by
+    /// `split_factor`. Pairs with `effectiveShares()` so cost basis is
+    /// preserved. Use for per-share cost display on a split-spanning lot.
+    pub fn effectiveOpenPrice(self: Lot) f64 {
+        return self.open_price / self.split_factor;
+    }
+
     /// Apply the share-class `price_ratio` to `raw_price`. See the
     /// "Pricing model" block at the top of this file for the full
     /// semantics of `is_preadjusted`.
@@ -300,13 +376,16 @@ pub const Lot = struct {
         return if (is_preadjusted) raw_price else raw_price * self.price_ratio;
     }
 
-    /// Market value of the lot at `raw_price`: `shares * effectivePrice`.
+    /// Market value of the lot at `raw_price`:
+    /// `effectiveShares * effectivePrice` (split- and share-class-aware).
     pub fn marketValue(self: Lot, raw_price: f64, is_preadjusted: bool) f64 {
-        return self.shares * self.effectivePrice(raw_price, is_preadjusted);
+        return self.effectiveShares() * self.effectivePrice(raw_price, is_preadjusted);
     }
 
     /// Realized gain/loss for a closed lot: shares * (close_price - open_price).
-    /// Returns null if the lot is still open.
+    /// Returns null if the lot is still open. Stays on RAW shares - a
+    /// closed lot is a completed round-trip whose recorded open/close are
+    /// consistent; `enrichSplits` leaves closed lots at `split_factor 1.0`.
     pub fn realizedGainLoss(self: Lot) ?f64 {
         const cp = self.close_price orelse return null;
         return self.shares * (cp - self.open_price);
@@ -314,16 +393,49 @@ pub const Lot = struct {
 
     /// Unrealized gain/loss for an open lot at the given market price.
     pub fn unrealizedGainLoss(self: Lot, current_price: f64) f64 {
-        return self.shares * (current_price - self.open_price);
+        return self.effectiveShares() * (current_price - self.effectiveOpenPrice());
     }
 
     pub fn returnPct(self: Lot, current_price: f64) f64 {
         if (self.open_price == 0) return 0;
         const price = if (self.close_price) |cp| cp else current_price;
-        return (price / self.open_price) - 1.0;
+        return (price / self.effectiveOpenPrice()) - 1.0;
     }
 };
 
+/// Populate each open stock lot's `split_factor` from the fetched split
+/// `corpus` (keyed by `priceSymbol()`), in place.
+///
+/// OPT-IN, PER SYMBOL: `cutovers` maps a symbol to the date through
+/// which its recorded shares are already split-adjusted (the
+/// `splits_current_through` field on that symbol's metadata.srf row). A
+/// symbol ABSENT from `cutovers` is left untouched - `split_factor`
+/// stays 1.0 and valuation behaves exactly as it did before splits
+/// existed. For a symbol present, a split is applied to a lot only if it
+/// occurred AFTER both the lot's purchase and the symbol's cutover (so
+/// already-restated legacy lots, whose splits predate the cutover, are
+/// left alone) and on/before `as_of`. Closed lots are skipped - their
+/// realized P&L stays on raw shares. Non-stock lots never split.
+///
+/// `as_of` is the reference date: today for live valuation, the
+/// snapshot date for a back-dated snapshot capture.
+pub fn enrichSplits(
+    lots: []Lot,
+    corpus: *const std.StringHashMap([]const Split),
+    cutovers: *const std.StringHashMap(Date),
+    as_of: Date,
+) void {
+    for (lots) |*lot| {
+        if (lot.security_type != .stock) continue;
+        if (!lot.lotIsOpenAsOf(as_of)) continue;
+        const cutover = cutovers.get(lot.priceSymbol()) orelse continue; // per-symbol opt-in
+        const splits = corpus.get(lot.priceSymbol()) orelse continue;
+        // Apply splits after BOTH the purchase and the symbol's cutover.
+        const after = if (cutover.lessThan(lot.open_date)) lot.open_date else cutover;
+        lot.split_factor = split.cumulativeSplitRatio(splits, after, as_of);
+    }
+}
+
 /// Aggregated position for a single symbol across multiple lots.
 pub const Position = struct {
     symbol: []const u8,
@@ -529,7 +641,7 @@ pub const Portfolio = struct {
 
             const pos = found.?;
             if (lot.lotIsOpenAsOf(as_of)) {
-                pos.shares += lot.shares;
+                pos.shares += lot.effectiveShares();
                 pos.total_cost += lot.costBasis();
                 pos.open_lots += 1;
             } else {
@@ -594,7 +706,7 @@ pub const Portfolio = struct {
 
             const pos = found.?;
             if (lot.isOpen(as_of)) {
-                pos.shares += lot.shares;
+                pos.shares += lot.effectiveShares();
                 pos.total_cost += lot.costBasis();
                 pos.open_lots += 1;
             } else {
@@ -1553,3 +1665,90 @@ test "stableNavCandle: fills all fields at $1" {
     try std.testing.expectEqual(@as(f64, 1), c.adj_close);
     try std.testing.expectEqual(@as(u64, 0), c.volume);
 }
+
+// ── Split-adjustment (effectiveShares / enrichSplits) tests ──
+
+test "effectiveShares/effectiveOpenPrice default to raw at factor 1.0" {
+    const lot = Lot{ .symbol = "AAPL", .shares = 10, .open_date = Date.fromYmd(2024, 1, 2), .open_price = 180.0 };
+    try std.testing.expectApproxEqAbs(@as(f64, 10), lot.effectiveShares(), 0.0001);
+    try std.testing.expectApproxEqAbs(@as(f64, 180.0), lot.effectiveOpenPrice(), 0.0001);
+    // Cost basis is invariant under the split factor.
+    try std.testing.expectApproxEqAbs(lot.costBasis(), lot.effectiveShares() * lot.effectiveOpenPrice(), 0.0001);
+}
+
+test "enrichSplits: per-symbol opt-in gate, forward split, post-split lot, legacy already-restated" {
+    const allocator = std.testing.allocator;
+    const as_of = Date.fromYmd(2026, 1, 1);
+
+    var corpus = std.StringHashMap([]const Split).init(allocator);
+    defer corpus.deinit();
+    const nvda_splits = [_]Split{.{ .date = Date.fromYmd(2024, 6, 10), .numerator = 10, .denominator = 1 }};
+    const amzn_splits = [_]Split{.{ .date = Date.fromYmd(2022, 6, 6), .numerator = 20, .denominator = 1 }};
+    const tsla_splits = [_]Split{.{ .date = Date.fromYmd(2024, 8, 1), .numerator = 3, .denominator = 1 }};
+    try corpus.put("NVDA", &nvda_splits);
+    try corpus.put("AMZN", &amzn_splits);
+    try corpus.put("TSLA", &tsla_splits);
+
+    // Per-symbol opt-in: NVDA and AMZN carry a cutover; TSLA does NOT.
+    var cutovers = std.StringHashMap(Date).init(allocator);
+    defer cutovers.deinit();
+    try cutovers.put("NVDA", Date.fromYmd(2024, 1, 1));
+    try cutovers.put("AMZN", Date.fromYmd(2024, 1, 1));
+
+    var lots = [_]Lot{
+        // NVDA held across the post-cutover split -> factor 10.
+        .{ .symbol = "NVDA", .shares = 100, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 40.0 },
+        // NVDA opened AFTER the split -> already post-split -> factor 1.
+        .{ .symbol = "NVDA", .shares = 50, .open_date = Date.fromYmd(2024, 8, 1), .open_price = 110.0 },
+        // AMZN split predates its cutover (already restated) -> factor 1.
+        .{ .symbol = "AMZN", .shares = 30, .open_date = Date.fromYmd(2019, 3, 1), .open_price = 90.0 },
+        // TSLA has a real post-purchase split but is NOT opted in -> factor 1.
+        .{ .symbol = "TSLA", .shares = 20, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 30.0 },
+        // Non-stock never splits.
+        .{ .symbol = "CASH", .shares = 5000, .open_date = Date.fromYmd(2019, 1, 1), .open_price = 1.0, .security_type = .cash },
+    };
+
+    enrichSplits(&lots, &corpus, &cutovers, as_of);
+
+    try std.testing.expectApproxEqAbs(@as(f64, 1000), lots[0].effectiveShares(), 0.0001);
+    try std.testing.expectApproxEqAbs(@as(f64, 4.0), lots[0].effectiveOpenPrice(), 0.0001); // 40 / 10
+    try std.testing.expectApproxEqAbs(lots[0].costBasis(), lots[0].effectiveShares() * lots[0].effectiveOpenPrice(), 0.0001);
+    try std.testing.expectApproxEqAbs(@as(f64, 50), lots[1].effectiveShares(), 0.0001);
+    try std.testing.expectApproxEqAbs(@as(f64, 30), lots[2].effectiveShares(), 0.0001);
+    // TSLA not opted in -> untouched despite a real post-purchase split.
+    try std.testing.expectApproxEqAbs(@as(f64, 20), lots[3].effectiveShares(), 0.0001);
+    try std.testing.expectApproxEqAbs(@as(f64, 5000), lots[4].effectiveShares(), 0.0001);
+
+    // Empty cutovers map -> every factor stays 1.0 (today's behavior).
+    var lots2 = [_]Lot{
+        .{ .symbol = "NVDA", .shares = 100, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 40.0 },
+    };
+    var empty = std.StringHashMap(Date).init(allocator);
+    defer empty.deinit();
+    enrichSplits(&lots2, &corpus, &empty, as_of);
+    try std.testing.expectApproxEqAbs(@as(f64, 100), lots2[0].effectiveShares(), 0.0001);
+}
+
+test "positionsAsOf reflects split_factor: effective shares, invariant basis, effective market value" {
+    const allocator = std.testing.allocator;
+    var lots = [_]Lot{
+        .{ .symbol = "NVDA", .shares = 100, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 40.0, .account = "Sample Brokerage" },
+    };
+    // Simulate enrichment applying a 10:1 split.
+    lots[0].split_factor = 10.0;
+
+    const pf = Portfolio{ .lots = &lots, .allocator = allocator };
+    const positions = try pf.positionsAsOf(allocator, Date.fromYmd(2026, 1, 1));
+    defer allocator.free(positions);
+
+    try std.testing.expectEqual(@as(usize, 1), positions.len);
+    // Effective shares: 100 * 10 = 1000.
+    try std.testing.expectApproxEqAbs(@as(f64, 1000), positions[0].shares, 0.001);
+    // Cost basis stays raw/invariant: 100 * 40 = 4000.
+    try std.testing.expectApproxEqAbs(@as(f64, 4000), positions[0].total_cost, 0.001);
+    // avg_cost = total_cost / effective_shares = 4.0 (effective per-share).
+    try std.testing.expectApproxEqAbs(@as(f64, 4.0), positions[0].avg_cost, 0.001);
+    // Market value at the post-split price $120: 1000 * 120 = 120,000
+    // (the whole point - raw 100 * 120 would undercount 10x).
+    try std.testing.expectApproxEqAbs(@as(f64, 120000), positions[0].marketValue(120.0, false), 0.01);
+}
diff --git a/src/models/split.zig b/src/models/split.zig
index 5833ac5..ffaa5b3 100644
--- a/src/models/split.zig
+++ b/src/models/split.zig
@@ -14,6 +14,31 @@ pub const Split = struct {
     }
 };
 
+/// Cumulative product of split ratios for splits in the window
+/// `(after, through]` - start-EXCLUSIVE, end-INCLUSIVE. Returns 1.0
+/// when no split falls in the window.
+///
+/// This is the single source of truth for the split-window walk. Two
+/// call sites depend on it and must never diverge:
+///   - price-return math (`analytics/performance.zig`) DIVIDES an
+///     earlier-epoch price by this to bring it into the later epoch.
+///   - lot effective-share enrichment (`enrichSplits` below) MULTIPLIES
+///     an earlier-epoch share count by this for the same reason.
+///
+/// The boundary convention matches the original inline walk in
+/// `performance.priceReturnSnap`: a split exactly on `after` is excluded
+/// (it predates the window's opening value) and one exactly on `through`
+/// is included.
+pub fn cumulativeSplitRatio(splits: []const Split, after: Date, through: Date) f64 {
+    var cum: f64 = 1.0;
+    for (splits) |s| {
+        if (s.date.lessThan(after) or s.date.eql(after)) continue; // after-exclusive
+        if (through.lessThan(s.date)) continue; // through-inclusive
+        cum *= s.ratio();
+    }
+    return cum;
+}
+
 const std = @import("std");
 
 test "split ratio" {
@@ -24,3 +49,65 @@ test "split ratio" {
     const two_for_one = Split{ .date = Date{ .days = 19000 }, .numerator = 2, .denominator = 1 };
     try std.testing.expectApproxEqAbs(@as(f64, 2.0), two_for_one.ratio(), 0.001);
 }
+
+test "cumulativeSplitRatio window boundaries and compounding" {
+    const s2021 = Split{ .date = Date.fromYmd(2021, 7, 20), .numerator = 4, .denominator = 1 };
+    const s2024 = Split{ .date = Date.fromYmd(2024, 6, 10), .numerator = 10, .denominator = 1 };
+    const reverse = Split{ .date = Date.fromYmd(2023, 5, 1), .numerator = 1, .denominator = 10 };
+
+    // No splits at all -> identity.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 1.0),
+        cumulativeSplitRatio(&.{}, Date.fromYmd(2020, 1, 1), Date.fromYmd(2026, 1, 1)),
+        0.0001,
+    );
+
+    // Single split strictly inside the window.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 4.0),
+        cumulativeSplitRatio(&.{s2021}, Date.fromYmd(2021, 1, 1), Date.fromYmd(2022, 1, 1)),
+        0.0001,
+    );
+
+    // Two splits inside -> product (bringing pre-2021 shares to today).
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 40.0),
+        cumulativeSplitRatio(&.{ s2021, s2024 }, Date.fromYmd(2020, 1, 1), Date.fromYmd(2026, 1, 1)),
+        0.0001,
+    );
+
+    // Split before the window is excluded.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 1.0),
+        cumulativeSplitRatio(&.{s2021}, Date.fromYmd(2022, 1, 1), Date.fromYmd(2026, 1, 1)),
+        0.0001,
+    );
+
+    // Split after the window is excluded.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 1.0),
+        cumulativeSplitRatio(&.{s2024}, Date.fromYmd(2020, 1, 1), Date.fromYmd(2023, 1, 1)),
+        0.0001,
+    );
+
+    // `after` boundary is EXCLUSIVE: split exactly on `after` is not applied.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 1.0),
+        cumulativeSplitRatio(&.{s2021}, Date.fromYmd(2021, 7, 20), Date.fromYmd(2026, 1, 1)),
+        0.0001,
+    );
+
+    // `through` boundary is INCLUSIVE: split exactly on `through` is applied.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 4.0),
+        cumulativeSplitRatio(&.{s2021}, Date.fromYmd(2020, 1, 1), Date.fromYmd(2021, 7, 20)),
+        0.0001,
+    );
+
+    // Reverse split composes correctly.
+    try std.testing.expectApproxEqAbs(
+        @as(f64, 0.1),
+        cumulativeSplitRatio(&.{reverse}, Date.fromYmd(2020, 1, 1), Date.fromYmd(2026, 1, 1)),
+        0.0001,
+    );
+}
diff --git a/src/portfolio_loader.zig b/src/portfolio_loader.zig
index 1f5bedc..23f84c7 100644
--- a/src/portfolio_loader.zig
+++ b/src/portfolio_loader.zig
@@ -59,6 +59,7 @@ const zfin = @import("root.zig");
 const framework = @import("commands/framework.zig");
 const stderr = @import("stderr.zig");
 const git = @import("git.zig");
+const enrichSplits = @import("models/portfolio.zig").enrichSplits;
 
 // ── Portfolio loading ────────────────────────────────────────
 
@@ -543,6 +544,138 @@ pub fn buildPortfolioData(
     };
 }
 
+/// Opt-in stock-split adjustment: set each open stock lot's
+/// `split_factor` from the per-symbol metadata.srf `splits_current_through`
+/// cutovers and the fetched split corpus. A no-op (and skips the corpus
+/// fetch entirely) when no symbol has opted in.
+///
+/// This mutates only `lots[].split_factor`; callers that hold an
+/// already-computed positions slice must recompute it afterward (the
+/// CLI wrapper `applySplitAdjustment` does this). Used directly by the
+/// TUI, snapshot, and audit paths, which recompute positions on their own.
+///
+/// Failures degrade gracefully to raw shares. Contributions never
+/// calls this (it diffs raw declared shares from git), so a split can
+/// never masquerade as a contribution.
+pub fn enrichLotsSplits(
+    svc: *zfin.DataService,
+    allocator: std.mem.Allocator,
+    lots: []zfin.Lot,
+    syms: []const []const u8,
+    anchor_path: []const u8,
+    as_of: zfin.Date,
+) void {
+    var cutovers = svc.loadSplitsCutovers(allocator, anchor_path);
+    defer freeCutovers(allocator, &cutovers);
+    if (cutovers.count() == 0) return; // nothing opted in -> skip the corpus fetch
+
+    var corpus = svc.loadAllSplits(allocator, syms, .{});
+    defer {
+        var it = corpus.valueIterator();
+        while (it.next()) |v| allocator.free(v.*);
+        corpus.deinit();
+    }
+
+    enrichSplits(lots, &corpus, &cutovers, as_of);
+}
+
+/// Free a `symbol -> cutover` map produced by `loadSplitsCutovers`
+/// (owned keys, then the map itself).
+fn freeCutovers(allocator: std.mem.Allocator, cutovers: *std.StringHashMap(zfin.Date)) void {
+    var it = cutovers.keyIterator();
+    while (it.next()) |k| allocator.free(k.*);
+    cutovers.deinit();
+}
+
+/// A held stock symbol that split AFTER a lot was purchased while that
+/// symbol has NOT opted into split adjustment - i.e. an unhandled split
+/// that would change the position once the user enables the feature for
+/// it. Surfaced as an `audit` hygiene finding. `symbol` borrows from the
+/// caller's lots; use before the portfolio is freed.
+pub const SplitNudge = struct {
+    symbol: []const u8,
+    date: zfin.Date,
+};
+
+/// Collect every held stock symbol that has NOT opted into split
+/// adjustment yet has a split after a lot's purchase date, in the CACHED
+/// split data (no network). One entry per symbol (first qualifying
+/// split). Powers the `audit` hygiene "unhandled stock splits" section.
+///
+/// Caller owns the returned slice (`allocator.free` it); each `symbol`
+/// borrows from `lots`, so use the result before the portfolio is freed.
+/// Cheap: cache-only reads. Returns an empty slice on any allocation
+/// failure (hygiene is best-effort).
+pub fn findUnhandledSplits(
+    svc: *zfin.DataService,
+    allocator: std.mem.Allocator,
+    lots: []const zfin.Lot,
+    syms: []const []const u8,
+    anchor_path: []const u8,
+    as_of: zfin.Date,
+) []SplitNudge {
+    var cutovers = svc.loadSplitsCutovers(allocator, anchor_path);
+    defer freeCutovers(allocator, &cutovers);
+
+    var corpus = svc.loadAllSplits(allocator, syms, .{ .skip_network = true });
+    defer {
+        var it = corpus.valueIterator();
+        while (it.next()) |v| allocator.free(v.*);
+        corpus.deinit();
+    }
+
+    var found: std.ArrayList(SplitNudge) = .empty;
+    defer found.deinit(allocator);
+
+    for (lots) |lot| {
+        if (lot.security_type != .stock) continue;
+        if (!lot.lotIsOpenAsOf(as_of)) continue;
+        const sym = lot.priceSymbol();
+        if (cutovers.contains(sym)) continue; // this symbol already opted in
+        // Dedup: one finding per symbol. Findings are rare, so a linear
+        // scan over what we've collected is cheaper than a side map.
+        var already = false;
+        for (found.items) |f| {
+            if (std.mem.eql(u8, f.symbol, sym)) {
+                already = true;
+                break;
+            }
+        }
+        if (already) continue;
+        const splits = corpus.get(sym) orelse continue;
+        for (splits) |s| {
+            // Split strictly after purchase and on/before the as-of date.
+            if (lot.open_date.lessThan(s.date) and !as_of.lessThan(s.date)) {
+                found.append(allocator, .{ .symbol = sym, .date = s.date }) catch break;
+                break;
+            }
+        }
+    }
+    return found.toOwnedSlice(allocator) catch &.{};
+}
+
+/// CLI wrapper: enrich a freshly loaded `LoadedPortfolio` in place and
+/// recompute `positions` from the (possibly) enriched lots so every
+/// downstream consumer (summary, per-lot rows, account breakdown) sees
+/// effective shares. The recompute is unconditional and cheap
+/// (in-memory, no I/O); it yields identical positions when nothing has
+/// opted in.
+pub fn applySplitAdjustment(
+    svc: *zfin.DataService,
+    allocator: std.mem.Allocator,
+    loaded: *LoadedPortfolio,
+    as_of: zfin.Date,
+) void {
+    enrichLotsSplits(svc, allocator, loaded.portfolio.lots, loaded.syms, loaded.anchor(), as_of);
+
+    // Positions were aggregated from raw lots at load time; recompute
+    // from the (now possibly enriched) lots. On failure, keep the
+    // existing positions.
+    const new_positions = loaded.portfolio.positions(as_of, allocator) catch return;
+    allocator.free(loaded.positions);
+    loaded.positions = new_positions;
+}
+
 // ── loadFromBytes tests (in-memory; no disk I/O) ─────────────
 //
 // All tests here construct synthetic SRF byte literals and route
@@ -884,3 +1017,128 @@ test "loadPortfolioFromPathsAtRev: file added later is silently skipped at earli
     try testing.expectEqual(@as(usize, 1), loaded.portfolio.lots.len);
     try testing.expectEqualStrings("AAPL", loaded.portfolio.lots[0].symbol);
 }
+
+// ── Split adjustment wiring (seeded cache + metadata) ────────
+
+/// Write a portfolio file, a metadata.srf (optionally with a per-symbol
+/// cutover row), and seed one NVDA 10:1 split into the cache under
+/// `dir`. Returns the realpath of the temp dir (borrows `path_buf`).
+fn seedSplitFixture(io: std.Io, tmp: *std.testing.TmpDir, path_buf: []u8, cutover_line: []const u8) ![]const u8 {
+    try tmp.dir.writeFile(io, .{
+        .sub_path = "zfintest_split_pf.srf",
+        .data =
+        \\#!srfv1
+        \\symbol::NVDA,shares:num:100,open_date::2020-01-01,open_price:num:40.00,account::Sample Brokerage
+        \\
+        ,
+    });
+    var meta_buf: [128]u8 = undefined;
+    const meta = try std.fmt.bufPrint(&meta_buf, "#!srfv1\n{s}", .{cutover_line});
+    try tmp.dir.writeFile(io, .{ .sub_path = "metadata.srf", .data = meta });
+
+    const dir_len = try tmp.dir.realPathFile(io, ".", path_buf);
+    const dir = path_buf[0..dir_len];
+
+    // Seed an NVDA 10:1 split (2024-06-10) into the split cache.
+    var store = zfin.cache.Store.init(io, testing.allocator, dir);
+    var splits = [_]zfin.Split{.{ .date = zfin.Date.fromYmd(2024, 6, 10), .numerator = 10, .denominator = 1 }};
+    store.write(zfin.Split, "NVDA", splits[0..], .{ .seconds = zfin.cache.Ttl.splits });
+    return dir;
+}
+
+test "applySplitAdjustment: end-to-end enriches loaded positions from seeded cache + cutover" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    // Per-symbol cutover before the 2024 split -> the split IS applied.
+    const dir = try seedSplitFixture(io, &tmp, &path_buf, "symbol::NVDA,splits_current_through::2024-01-01\n");
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const pf_path = try std.fs.path.join(allocator, &.{ dir, "zfintest_split_pf.srf" });
+    defer allocator.free(pf_path);
+    const paths = try allocator.dupe([]const u8, &.{pf_path});
+    defer allocator.free(paths);
+    var loaded = loadPortfolioFromPaths(io, allocator, paths, zfin.Date.fromYmd(2026, 1, 1)) orelse
+        return error.TestUnexpectedResult;
+    defer loaded.deinit(allocator);
+
+    // Before enrichment: raw 100 shares.
+    try testing.expectApproxEqAbs(@as(f64, 100), loaded.positions[0].shares, 0.001);
+
+    applySplitAdjustment(&svc, allocator, &loaded, zfin.Date.fromYmd(2026, 1, 1));
+
+    // After: 100 * 10 = 1000 effective shares; factor stamped on the lot;
+    // cost basis stays invariant (100 * 40 = 4000).
+    try testing.expectApproxEqAbs(@as(f64, 10.0), loaded.portfolio.lots[0].split_factor, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 1000), loaded.positions[0].shares, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 4000), loaded.positions[0].total_cost, 0.001);
+}
+
+test "applySplitAdjustment: no cutover is a no-op (raw shares preserved)" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    // metadata.srf with NO cutover row -> opt-in off.
+    const dir = try seedSplitFixture(io, &tmp, &path_buf, "");
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const pf_path = try std.fs.path.join(allocator, &.{ dir, "zfintest_split_pf.srf" });
+    defer allocator.free(pf_path);
+    const paths = try allocator.dupe([]const u8, &.{pf_path});
+    defer allocator.free(paths);
+    var loaded = loadPortfolioFromPaths(io, allocator, paths, zfin.Date.fromYmd(2026, 1, 1)) orelse
+        return error.TestUnexpectedResult;
+    defer loaded.deinit(allocator);
+
+    applySplitAdjustment(&svc, allocator, &loaded, zfin.Date.fromYmd(2026, 1, 1));
+
+    // Opt-in off -> factor stays 1.0, shares stay raw.
+    try testing.expectApproxEqAbs(@as(f64, 1.0), loaded.portfolio.lots[0].split_factor, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 100), loaded.positions[0].shares, 0.001);
+}
+
+test "findUnhandledSplits: flags post-purchase splits for un-opted-in symbols only" {
+    const allocator = testing.allocator;
+    const io = testing.io;
+    var tmp = std.testing.tmpDir(.{});
+    defer tmp.cleanup();
+
+    var path_buf: [std.fs.max_path_bytes]u8 = undefined;
+    const dir = try seedSplitFixture(io, &tmp, &path_buf, ""); // opt-in OFF
+
+    var svc = zfin.DataService.init(io, allocator, .{ .cache_dir = dir });
+    defer svc.deinit();
+
+    const anchor = try std.fs.path.join(allocator, &.{ dir, "zfintest_split_pf.srf" });
+    defer allocator.free(anchor);
+
+    var lots = [_]zfin.Lot{
+        .{ .symbol = "NVDA", .shares = 100, .open_date = zfin.Date.fromYmd(2020, 1, 1), .open_price = 40 },
+    };
+    const syms = [_][]const u8{"NVDA"};
+
+    // Opt-in off + a split after purchase -> one finding.
+    const found = findUnhandledSplits(&svc, allocator, &lots, &syms, anchor, zfin.Date.fromYmd(2026, 1, 1));
+    defer allocator.free(found);
+    try testing.expectEqual(@as(usize, 1), found.len);
+    try testing.expectEqualStrings("NVDA", found[0].symbol);
+    try testing.expect(found[0].date.eql(zfin.Date.fromYmd(2024, 6, 10)));
+
+    // A lot opened AFTER the split -> no finding for it.
+    var lots_after = [_]zfin.Lot{
+        .{ .symbol = "NVDA", .shares = 5, .open_date = zfin.Date.fromYmd(2025, 1, 1), .open_price = 120 },
+    };
+    const none = findUnhandledSplits(&svc, allocator, &lots_after, &syms, anchor, zfin.Date.fromYmd(2026, 1, 1));
+    defer allocator.free(none);
+    try testing.expectEqual(@as(usize, 0), none.len);
+}
diff --git a/src/service.zig b/src/service.zig
index 45b300d..9ba89f3 100644
--- a/src/service.zig
+++ b/src/service.zig
@@ -3176,6 +3176,68 @@ pub const DataService = struct {
 
         return transaction_log.parseTransactionLogFile(self.allocator, data) catch null;
     }
+
+    /// Read the per-symbol `splits_current_through` opt-in from the
+    /// metadata.srf sibling of `portfolio_path` into a `symbol -> cutover`
+    /// map. A symbol absent from the map has NOT opted in - its lots keep
+    /// `split_factor` 1.0 (today's behavior). An empty map (no file, no
+    /// symbol carries the field) means split adjustment is fully off.
+    /// Caller owns the map AND each key: free every key, then `deinit`.
+    /// See the "Share model" block in models/portfolio.zig.
+    pub fn loadSplitsCutovers(self: *DataService, allocator: std.mem.Allocator, portfolio_path: []const u8) std.StringHashMap(Date) {
+        var map = std.StringHashMap(Date).init(allocator);
+
+        const dir_end = if (std.mem.lastIndexOfScalar(u8, portfolio_path, std.fs.path.sep)) |idx| idx + 1 else 0;
+        const path = std.fmt.allocPrint(self.allocator, "{s}metadata.srf", .{portfolio_path[0..dir_end]}) catch return map;
+        defer self.allocator.free(path);
+
+        const data = std.Io.Dir.cwd().readFileAlloc(self.io, path, self.allocator, .limited(1024 * 1024)) catch return map;
+        defer self.allocator.free(data);
+
+        var cm = classification.parseClassificationFile(self.allocator, data) catch return map;
+        defer cm.deinit();
+
+        for (cm.entries) |e| {
+            const cutover = e.splits_current_through orelse continue;
+            // A symbol can repeat across blended-fund rows; keep the first
+            // cutover and dupe its key exactly once (no leak on repeats).
+            const gop = map.getOrPut(e.symbol) catch continue;
+            if (!gop.found_existing) {
+                gop.key_ptr.* = allocator.dupe(u8, e.symbol) catch {
+                    _ = map.remove(e.symbol);
+                    continue;
+                };
+                gop.value_ptr.* = cutover;
+            }
+        }
+        return map;
+    }
+
+    /// Fetch split history for each symbol into a corpus keyed by
+    /// symbol, for lot effective-share enrichment (`enrichSplits`).
+    /// Symbols whose fetch fails or carry no splits are simply absent
+    /// (their lots keep `split_factor` 1.0 - a safe no-adjustment
+    /// fallback). Caller owns the returned map AND each value slice:
+    /// free every value, then `deinit` the map.
+    pub fn loadAllSplits(
+        self: *DataService,
+        allocator: std.mem.Allocator,
+        syms: []const []const u8,
+        opts: FetchOptions,
+    ) std.StringHashMap([]const Split) {
+        var corpus = std.StringHashMap([]const Split).init(allocator);
+        for (syms) |sym| {
+            const fr = self.getSplits(sym, opts) catch continue;
+            defer fr.deinit();
+            if (fr.data.len == 0) continue;
+            const owned = allocator.dupe(Split, fr.data) catch continue;
+            corpus.put(sym, owned) catch {
+                allocator.free(owned);
+                continue;
+            };
+        }
+        return corpus;
+    }
 };
 
 // ── Tests ─────────────────────────────────────────────────────────
diff --git a/src/tui/history_tab.zig b/src/tui/history_tab.zig
index 573d8cf..ee89fd6 100644
--- a/src/tui/history_tab.zig
+++ b/src/tui/history_tab.zig
@@ -726,6 +726,14 @@ fn buildCompareFromSelections(state: *State, app: *App, sel_a: usize, sel_b: usi
     // "now is live" only when the NEWER endpoint is the live row.
     const now_is_live = newer.is_live;
 
+    // Opt-in: bring a snapshot "then" side into the current split basis
+    // (mirrors the CLI). Skipped when "then" is the live portfolio,
+    // which is already effective-share. No-op unless the split opt-in
+    // is set in metadata.srf.
+    if (!older.is_live) {
+        compare_core.adjustThenForSplits(app.svc, app.allocator, then_map_ptr, portfolio_path, older.date, newer.date);
+    }
+
     const cv = try compare_view.buildCompareView(
         app.allocator,
         older.date,
diff --git a/src/tui/portfolio_tab.zig b/src/tui/portfolio_tab.zig
index 4759eb6..9ca67e1 100644
--- a/src/tui/portfolio_tab.zig
+++ b/src/tui/portfolio_tab.zig
@@ -1874,18 +1874,18 @@ pub fn drawContent(state: *State, app: *App, arena: std.mem.Allocator, buf: []va
                         if (row.pos_idx < s.allocations.len) {
                             const price = s.allocations[row.pos_idx].current_price;
                             const use_price = lot.close_price orelse price;
-                            const gl = lot.shares * (use_price - lot.open_price);
+                            const gl = lot.effectiveShares() * (use_price - lot.effectiveOpenPrice());
                             lot_positive = gl >= 0;
                             lot_gl_str = try std.fmt.allocPrint(arena, "{s}{f}", .{
                                 if (gl >= 0) @as([]const u8, "+") else @as([]const u8, "-"),
                                 Money.from(if (gl >= 0) gl else -gl),
                             });
-                            lot_mv_str = try std.fmt.allocPrint(arena, "{f}", .{Money.from(lot.shares * use_price)});
+                            lot_mv_str = try std.fmt.allocPrint(arena, "{f}", .{Money.from(lot.effectiveShares() * use_price)});
                         }
                     }
 
                     var price_str2: [24]u8 = undefined;
-                    const lot_price_str = std.fmt.bufPrint(&price_str2, "{f}", .{Money.from(lot.open_price)}) catch "$?";
+                    const lot_price_str = std.fmt.bufPrint(&price_str2, "{f}", .{Money.from(lot.effectiveOpenPrice())}) catch "$?";
                     const status_str: []const u8 = if (lot.isOpen(app.today)) "open" else "closed";
                     const indicator = fmt.capitalGainsIndicator(app.today, lot.open_date);
                     const lot_date_col = try std.fmt.allocPrint(arena, "{s} {s}", .{ date_str, indicator });
@@ -1897,7 +1897,7 @@ pub fn drawContent(state: *State, app: *App, arena: std.mem.Allocator, buf: []va
                         break :blk fmt.padRightToCols(&lot_sym_buf, sym_src, cw.symbol_w);
                     };
                     var lot_shr_raw: [48]u8 = undefined;
-                    const lot_shr_raw_s = std.fmt.bufPrint(&lot_shr_raw, "{d:.1}", .{lot.shares}) catch "?";
+                    const lot_shr_raw_s = std.fmt.bufPrint(&lot_shr_raw, "{d:.1}", .{lot.effectiveShares()}) catch "?";
                     var lot_shr_buf: [64]u8 = undefined;
                     const lot_shr_cell = fmt.padLeftToCols(&lot_shr_buf, lot_shr_raw_s, cw.shares_w);
                     var lot_cost_pad: [64]u8 = undefined;
diff --git a/src/views/compare.zig b/src/views/compare.zig
index f4e3e1e..0bcc644 100644
--- a/src/views/compare.zig
+++ b/src/views/compare.zig
@@ -278,6 +278,29 @@ pub fn buildTotalsRow(then: f64, now: f64) TotalsRow {
     };
 }
 
+/// Bring a "then" snapshot's holdings into the "now" split basis, in
+/// place. For each symbol present in `factors`, multiplies shares by
+/// and divides price by the cumulative split ratio, so a split between
+/// the two epochs doesn't read as a phantom share-count jump or a
+/// price crash in `buildSymbolChange`.
+///
+/// Pure: the caller resolves `factors` (symbol -> cumulative split
+/// ratio in the window `(max(cutover, then_date), now_date]`) from the
+/// split corpus. This bridges the epoch gap between the "then" snapshot
+/// and "now" so a held-throughout position nets to zero share change
+/// across the split. A factor of 1.0 (or a symbol absent from `factors`)
+/// is a no-op, so this is inert unless the split opt-in is on and a
+/// split actually applies.
+pub fn forwardAdjustThen(then_map: *HoldingMap, factors: *const std.StringHashMap(f64)) void {
+    var it = then_map.iterator();
+    while (it.next()) |e| {
+        const f = factors.get(e.key_ptr.*) orelse continue;
+        if (f == 1.0 or f == 0.0) continue;
+        e.value_ptr.shares *= f;
+        e.value_ptr.price /= f;
+    }
+}
+
 /// Primary view builder. Intersects `then_map` with `now_map`, computes
 /// per-symbol changes for held-throughout symbols, counts added/removed,
 /// and sorts descending by `pct_change`.
@@ -521,6 +544,26 @@ test "buildTotalsRow: zero then doesn't NaN" {
     try testing.expectEqual(StyleIntent.positive, t.style); // delta > 0 so positive
 }
 
+test "forwardAdjustThen: split factor scales shares up, price down; absent symbols untouched" {
+    var then_map: HoldingMap = .init(testing.allocator);
+    defer then_map.deinit();
+    try then_map.put("NVDA", .{ .shares = 100, .price = 600.0 });
+    try then_map.put("AAPL", .{ .shares = 50, .price = 180.0 });
+
+    var factors = std.StringHashMap(f64).init(testing.allocator);
+    defer factors.deinit();
+    try factors.put("NVDA", 10.0); // 10:1 split between then and now
+
+    forwardAdjustThen(&then_map, &factors);
+
+    // NVDA brought into the post-split basis: 100 -> 1000 shares, $600 -> $60.
+    try testing.expectApproxEqAbs(@as(f64, 1000), then_map.get("NVDA").?.shares, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 60.0), then_map.get("NVDA").?.price, 0.001);
+    // AAPL absent from factors -> untouched.
+    try testing.expectApproxEqAbs(@as(f64, 50), then_map.get("AAPL").?.shares, 0.001);
+    try testing.expectApproxEqAbs(@as(f64, 180.0), then_map.get("AAPL").?.price, 0.001);
+}
+
 test "buildCompareView: intersection with added and removed" {
     var then_map: HoldingMap = .init(testing.allocator);
     defer then_map.deinit();
diff --git a/src/views/portfolio_sections.zig b/src/views/portfolio_sections.zig
index 010937b..4aa626b 100644
--- a/src/views/portfolio_sections.zig
+++ b/src/views/portfolio_sections.zig
@@ -115,11 +115,11 @@ pub fn computeWidths(
 
     for (lots) |lot| {
         if (lot.security_type != .stock) continue;
-        w.shares_w = @max(w.shares_w, sharesCols(lot.shares));
-        w.price_w = @max(w.price_w, moneyCols(lot.open_price));
+        w.shares_w = @max(w.shares_w, sharesCols(lot.effectiveShares()));
+        w.price_w = @max(w.price_w, moneyCols(lot.effectiveOpenPrice()));
         const use_price = lot.close_price orelse currentPriceFor(allocations, lot.priceSymbol());
-        w.value_w = @max(w.value_w, moneyCols(lot.shares * use_price));
-        w.gainloss_w = @max(w.gainloss_w, gainLossCols(lot.shares * (use_price - lot.open_price)));
+        w.value_w = @max(w.value_w, moneyCols(lot.effectiveShares() * use_price));
+        w.gainloss_w = @max(w.gainloss_w, gainLossCols(lot.effectiveShares() * (use_price - lot.effectiveOpenPrice())));
     }
 
     w.value_w = @max(w.value_w, moneyCols(total_value));
@@ -729,3 +729,17 @@ test "writeHeader / writeSeparator render the same column count as the widths" {
         fmt.displayCols(sep[0 .. sep.len - 1]),
     );
 }
+
+test "computeWidths: lot columns size to effective (split-adjusted) shares" {
+    // A pre-split lot enriched with a 10:1 factor renders 1000 shares,
+    // so the shares column must be sized for the effective count, not
+    // the raw 100.
+    var lots = [_]Lot{
+        .{ .symbol = "NVDA", .shares = 100, .open_date = Date.fromYmd(2020, 1, 1), .open_price = 40, .split_factor = 10.0 },
+    };
+    const no_allocs: []const Allocation = &.{};
+    const no_watch: []const []const u8 = &.{};
+    const w = computeWidths(no_allocs, &lots, 0, 0, no_watch, null);
+    try testing.expectEqual(sharesCols(1000.0), w.shares_w);
+    try testing.expect(w.shares_w >= sharesCols(100.0));
+}