From 62104fbcabf811b6cd31db15f0f72db1f9d3c6e6 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Wed, 13 May 2026 10:25:07 +0300
Subject: cap filterStack undo history to 50 levels to prevent unbounded growth

Adds maxFilterHistory=50 and evicts the oldest entry from both the
history and label-stack slices in filterStack.push whenever the cap is
exceeded. Covers the fix with a new table-driven unit test.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 internal/tui/filterstack.go | 13 +++++++++++++
 internal/tui/tui_test.go    | 21 +++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/internal/tui/filterstack.go b/internal/tui/filterstack.go
index 016d845..28667d9 100644
--- a/internal/tui/filterstack.go
+++ b/internal/tui/filterstack.go
@@ -7,6 +7,11 @@ import (
 	"ior/internal/globalfilter/presenter"
 )
 
+// maxFilterHistory is the maximum number of undo levels retained by filterStack.
+// Once this cap is reached, the oldest entry is evicted so the slices never
+// grow without bound across long-running sessions or automated filter changes.
+const maxFilterHistory = 50
+
 // filterStack manages the trace filter chain: the active filter, the undo
 // history, and the human-readable label stack displayed in the status bar.
 // It owns all filter mutation and label-generation logic so the top-level
@@ -29,6 +34,8 @@ func (f *filterStack) current() globalfilter.Filter {
 
 // push records oldFilter in the history stack, sets global to newFilter, and
 // appends an action label. Returns true when the filter actually changed.
+// When the history depth would exceed maxFilterHistory the oldest entry is
+// evicted from both slices to keep memory usage bounded.
 func (f *filterStack) push(newFilter globalfilter.Filter, action string) bool {
 	next := newFilter.Clone()
 	if f.global.Equal(next) {
@@ -36,6 +43,12 @@ func (f *filterStack) push(newFilter globalfilter.Filter, action string) bool {
 	}
 	f.history = append(f.history, f.global.Clone())
 	f.stack = append(f.stack, globalFilterActionLabel(f.global, next, action))
+	// Evict the oldest undo level once the cap is exceeded so the slices
+	// never grow without bound across long-running sessions.
+	if len(f.history) > maxFilterHistory {
+		f.history = f.history[1:]
+		f.stack = f.stack[1:]
+	}
 	f.global = next
 	return true
 }
diff --git a/internal/tui/tui_test.go b/internal/tui/tui_test.go
index ba0f8ed..a685719 100644
--- a/internal/tui/tui_test.go
+++ b/internal/tui/tui_test.go
@@ -1725,6 +1725,27 @@ func TestDashboardFooterShowsGlobalFilterStack(t *testing.T) {
 	}
 }
 
+func TestFilterStackHistoryCapEvictsOldestEntries(t *testing.T) {
+	// Push maxFilterHistory+10 distinct filters and verify the slices never
+	// exceed the cap. The oldest entries must be evicted, and the most-recent
+	// maxFilterHistory entries must be retained.
+	fs := newFilterStack(globalfilter.Filter{})
+	for i := 0; i < maxFilterHistory+10; i++ {
+		f := globalfilter.Filter{}
+		f.FD = globalfilter.NewEqFilter(int64(i + 1)) // unique per iteration
+		fs.push(f, "")
+	}
+	if len(fs.history) > maxFilterHistory {
+		t.Fatalf("history exceeds cap: got %d, want <= %d", len(fs.history), maxFilterHistory)
+	}
+	if len(fs.stack) > maxFilterHistory {
+		t.Fatalf("stack exceeds cap: got %d, want <= %d", len(fs.stack), maxFilterHistory)
+	}
+	if len(fs.history) != len(fs.stack) {
+		t.Fatalf("history and stack lengths must match: history=%d stack=%d", len(fs.history), len(fs.stack))
+	}
+}
+
 func TestProcessesTabEnterAppliesSelectedProcessAsGlobalFilter(t *testing.T) {
 	m := NewModel(-1, func(context.Context) error { return nil })
 	m.screen = ScreenDashboard
-- 
cgit v1.2.3