diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fea560..23a2d2e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `--bterminal-pane-padding-inline: clamp(0.75rem, 3.5cqi, 2rem)` shared CSS variable for responsive pane padding (catppuccin.css)
 
 ### Fixed
+- FilesTab invalid HTML nesting: file tab bar used `<button>` inside `<button>` which Svelte/browser rejects — changed outer element to `<div role="tab">` (FilesTab.svelte)
 - ClaudeSession type errors: cast `last_session_id` to UUID template literal type, add missing `timestamp` field (from `created_at`) to restored AgentMessage records (ClaudeSession.svelte)
 - Cost bar shows only last turn's cost instead of cumulative session total: `updateAgentCost()` changed from assignment to accumulation (`+=`) so continued sessions properly sum costs across all turns (agents.svelte.ts)
 - ProjectBox tab switch destroys running agent sessions: changed `{#if activeTab}` conditional rendering to CSS `style:display` (flex/none) for all three content panes and terminal section — ClaudeSession now stays mounted across tab switches, preserving session ID, message history, and running agents (ProjectBox.svelte)