allow for configured max accumulation years

TODO.md

@@ -31,9 +31,6 @@ ranking; unlabeled items are "someday, if the mood strikes."
   earlier than the other would benefit from per-person
   `retirement_age` fields on each `type::birthdate` record, with
   contributions stopped per-person.
-- **Configurable max_accumulation_years - priority LOW.**
-  Hardcoded at 50 years. Route through `projections.srf` if anyone
-  hits the cap.
 - Multiple spending models: flat (current), decreasing (1-2% real annual decrease,
   Blanchett "spending smile"). Late-life healthcare better modeled as a life event.
 - **Historical projection overlay follow-ups.** The base

docs/explanation/projections-model.md

@@ -98,12 +98,15 @@ and longer horizons both lower the safe number.
 
 When you set a `target_spending` instead of a date, zfin inverts the
 question: for each (horizon x confidence) cell it searches for the
-**earliest** accumulation length (up to 50 years) that sustains your
-spending, and renders the grid of answers. One cell is promoted to the
+**earliest** accumulation length (up to `max_accumulation_years`, 50
+years by default) that sustains your spending, and renders the grid of
+answers. One cell is promoted to the
 headline (see
 [promotion rules](../reference/config/projections-srf.md#the-two-retirement-planning-inputs)).
 If no length within the cap works, the cell is **infeasible** -- shown
-honestly rather than fudged.
+honestly rather than fudged. A young saver with a runway longer than 50
+years can raise the cap via
+[`max_accumulation_years`](../reference/config/projections-srf.md#config-fields).
 
 ## The caveat that matters most
 

docs/guides/plan-retirement.md

@@ -151,7 +151,7 @@ configured date wins the headline; the grid is the comparison.
 `pre-retirement-spending-target` sets an aggressive
 `target_spending:num:2400000` and pins the headline to the
 longest-horizon, highest-confidence cell -- which turns out to be
-unreachable inside the 50-year search:
+unreachable inside the default 50-year search:
 
 ```bash
 ZFIN_HOME=examples/pre-retirement-spending-target zfin projections

docs/reference/config/projections-srf.md

@@ -45,6 +45,7 @@ type::event,name::Social Security,start_age:num:70,amount:num:38400
 | `contribution_inflation_adjusted`    | bool | If `true` (default), contributions grow with CPI year over year.                                                               |
 | `target_spending`                    | num  | Desired retirement spending, in today's dollars.                                                                               |
 | `target_spending_inflation_adjusted` | bool | If `true` (default), target spending grows with CPI during distribution.                                                       |
+| `max_accumulation_years`             | num  | Ceiling (in years) the earliest-retirement search scans when `target_spending` is set. Default `50`, capped at `100`.          |
 | `retirement_target`                  | num  | Annotation on a `horizon`/`horizon_age` line that overrides the earliest-retirement promotion rule. Allowed: `90`, `95`, `99`. |
 
 ### Choosing an `expense_ratio`
@@ -175,9 +176,10 @@ type::config,horizon:num:35,retirement_target:num:95
 
 At most one horizon may carry the annotation; configuring more than one
 drops them all and falls back to the default rule. If the promoted cell
-is infeasible (no accumulation length <= 50 years sustains the
-spending), the headline reads "not feasible" and the grid still renders
-so you can pick a workable anchor.
+is infeasible (no accumulation length within `max_accumulation_years`
+-- 50 years by default -- sustains the spending), the headline reads
+"not feasible" and the grid still renders so you can pick a workable
+anchor.
 
 ## The example configurations
 

src/analytics/projections.zig

@@ -242,6 +242,18 @@ pub const UserConfig = struct {
     /// If true, the target spending grows with CPI during the
     /// distribution phase (matches the existing SWR model).
     target_spending_inflation_adjusted: bool = true,
+    /// Ceiling on the accumulation years the earliest-retirement
+    /// search (`findEarliestRetirement`) will consider when
+    /// `target_spending` is set. Defaults to
+    /// `default_max_accumulation_years` (50). Override via
+    /// `type::config,max_accumulation_years:num:N` in projections.srf
+    /// for someone with a longer-than-50-year planning runway (a
+    /// young saver). Clamped at parse time to
+    /// `max_configurable_accumulation_years`. Only affects the
+    /// target-spending search path; an explicit `retirement_age` /
+    /// `retirement_at` derives its accumulation years directly and
+    /// ignores this cap.
+    max_accumulation_years: u16 = default_max_accumulation_years,
     /// Stock benchmark symbol used in the projection's
     /// benchmark-comparison table and bands. Defaults to "SPY".
     /// Override via `type::config,benchmark_stock::SYMBOL` in
@@ -468,6 +480,7 @@ const SrfConfig = struct {
     contribution_inflation_adjusted: ?bool = null,
     target_spending: ?f64 = null,
     target_spending_inflation_adjusted: ?bool = null,
+    max_accumulation_years: ?u16 = null,
     benchmark_stock: ?[]const u8 = null,
     benchmark_bond: ?[]const u8 = null,
 };
@@ -619,6 +632,22 @@ pub fn parseProjectionsConfig(data: ?[]const u8) UserConfig {
                 if (c.target_spending_inflation_adjusted) |b| {
                     config.target_spending_inflation_adjusted = b;
                 }
+                if (c.max_accumulation_years) |n| {
+                    if (n == 0) {
+                        // A zero-year search ceiling is degenerate (it
+                        // would only ever ask "can I retire today?").
+                        // Almost certainly a typo; keep the default.
+                        warnUser("projections: max_accumulation_years must be > 0; ignoring record", .{});
+                    } else if (n > max_configurable_accumulation_years) {
+                        // Respect the intent (the user wants a large
+                        // ceiling) but clamp to keep the search bounded
+                        // and inside the historical data span.
+                        warnUser("projections: max_accumulation_years capped at {d} (got {d})", .{ max_configurable_accumulation_years, n });
+                        config.max_accumulation_years = max_configurable_accumulation_years;
+                    } else {
+                        config.max_accumulation_years = n;
+                    }
+                }
                 if (c.benchmark_stock) |sym| {
                     if (sym.len == 0 or sym.len > config.benchmark_stock_buf.len) {
                         warnUser("projections: benchmark_stock must be 1..{d} chars (got {d}); ignoring record", .{ config.benchmark_stock_buf.len, sym.len });
@@ -1073,10 +1102,20 @@ pub const EarliestRetirement = struct {
     p90_at_retirement: f64,
 };
 
-/// Maximum accumulation years to search. 50 covers a 25-year-old
-/// planning to age 75. Hardcoded; if anyone hits this, route through
-/// projections.srf as a config field.
-pub const max_accumulation_years: u16 = 50;
+/// Default ceiling on the accumulation years the earliest-retirement
+/// search considers. 50 covers a 25-year-old planning to age 75.
+/// Overridable per-portfolio via
+/// `type::config,max_accumulation_years:num:N` in projections.srf -
+/// see `UserConfig.max_accumulation_years`.
+pub const default_max_accumulation_years: u16 = 50;
+
+/// Hard ceiling on a user-configured `max_accumulation_years`. A
+/// newborn planning to age 100 is the outer edge of anything sane;
+/// larger values are clamped (with a warning) to keep the search
+/// bounded and comfortably inside the Shiller data span. Mirrors
+/// `promotion_age_cap`'s "nobody is still accumulating past 100"
+/// reasoning.
+pub const max_configurable_accumulation_years: u16 = 100;
 
 /// Earliest-retirement search: given a target annual spending
 /// level, find the smallest `accumulation_years` N in [0, `max_years`]
@@ -2166,6 +2205,39 @@ test "parseProjectionsConfig rejects negative target_spending" {
     try std.testing.expectEqual(@as(?f64, null), config.target_spending);
 }
 
+test "parseProjectionsConfig max_accumulation_years defaults to 50" {
+    const config = parseProjectionsConfig("#!srfv1\n");
+    try std.testing.expectEqual(default_max_accumulation_years, config.max_accumulation_years);
+}
+
+test "parseProjectionsConfig parses max_accumulation_years override" {
+    const data =
+        \\#!srfv1
+        \\type::config,max_accumulation_years:num:65
+    ;
+    const config = parseProjectionsConfig(data);
+    try std.testing.expectEqual(@as(u16, 65), config.max_accumulation_years);
+}
+
+test "parseProjectionsConfig rejects zero max_accumulation_years" {
+    const data =
+        \\#!srfv1
+        \\type::config,max_accumulation_years:num:0
+    ;
+    const config = parseProjectionsConfig(data);
+    // Zero is degenerate; dropped, default retained.
+    try std.testing.expectEqual(default_max_accumulation_years, config.max_accumulation_years);
+}
+
+test "parseProjectionsConfig clamps oversized max_accumulation_years to ceiling" {
+    const data =
+        \\#!srfv1
+        \\type::config,max_accumulation_years:num:500
+    ;
+    const config = parseProjectionsConfig(data);
+    try std.testing.expectEqual(max_configurable_accumulation_years, config.max_accumulation_years);
+}
+
 test "parseProjectionsConfig return_cap defaults to null" {
     const config = parseProjectionsConfig("#!srfv1\n");
     try std.testing.expectEqual(@as(?f64, null), config.return_cap);

src/views/projections.zig

@@ -381,7 +381,7 @@ pub fn buildProjectionContext(
                     h,
                     conf,
                     events,
-                    projections.max_accumulation_years,
+                    config.max_accumulation_years,
                     sim_expense_ratio,
                 );
             }