From c465409aaa5672e3466b6f8744b737fa84993f2b Mon Sep 17 00:00:00 2001
From: Sam Scholten
Date: Wed, 7 Oct 2026 15:33:41 +1000
Subject: export: per-feed negative ceiling (--neg-feed-cap-pct)

No feed may hold more than 5% (floor 50) of the negative target, counting
existing history: uncapped, a few firehoses own the negative class because
the read+unstarred pool is sized by feed volume. Enforced by skipping
ceiling-full feeds mid seeded permutation walk; shortfall vs the ratio is
reported, neg_capped added to the run summary. Also makes bulk mark-read
of high-volume feeds safe for training data.
---
 cmds/negcap_test.go | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 cmds/negcap_test.go

(limited to 'cmds/negcap_test.go')

diff --git a/cmds/negcap_test.go b/cmds/negcap_test.go
new file mode 100644
index 0000000..5076163
--- /dev/null
+++ b/cmds/negcap_test.go
@@ -0,0 +1,25 @@
+// The shared per-feed negative ceiling: uncapped at pct 0, floored so a
+// young pool isn't strangled, and clamped to the target itself.
+package cmds
+
+import "testing"
+
+func TestFeedNegCap(t *testing.T) {
+	for _, tc := range []struct {
+		name                  string
+		pct, ratio, pos, want int
+	}{
+		{"uncapped at 0", 0, 20, 500, 0},
+		{"normal: 5% of 10000-target", 5, 20, 500, 500},
+		{"floor wins for young pools", 5, 20, 10, 50},    // target 200, 5% = 10 → floor 50
+		{"clamped to the target", 90, 20, 3, 54},         // target 60, 90% = 54
+		{"floor can exceed a tiny target", 5, 20, 1, 20}, // target 20 → clamp to 20
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := feedNegCap(tc.pct, tc.ratio, tc.pos); got != tc.want {
+				t.Errorf("feedNegCap(%d, %d, %d) = %d, want %d",
+					tc.pct, tc.ratio, tc.pos, got, tc.want)
+			}
+		})
+	}
+}
-- 
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