Issue: #434 Branch: fix/issue-434 (verification + documentation) Status: FIXED & VERIFIED (2026-08-23) — fix itself landed upstream in commit 9eba4f88f (credited to sibling issue #431, filed ~3h before #434); this run re-verified every render path live and closed the ticket.

Pages rendered through the dashio workAreaSimple.tpl template (e.g. Code Tracker Management flows) showed two stacked TestLink headers: the shell's own header (rendered around the mainframe iframe by lib/general/main.php) plus a second, full HTML head/header injected inside the iframe content.

1. Pre-9eba4f88f, gui/templates/dashio/workAreaSimple.tpl:6 began with {include file="inc_head.tpl"}.
2. gui/templates/dashio/include/inc_head.tpl:11-24 emits a FULL <head>: charset meta, <base href>, <title>TestLink</title>, favicon, jQuery, testlink_library.js, all CSS.
3. In the dashio layout this template renders as iframe content, so its head duplicated the chrome the parent page already draws → stacked headers.

The tl-classic theme uses workAreaSimple.tpl as a standalone page where the include is correct; the dashio port reused it verbatim without dropping the head.

Commit 9eba4f88f: replace {include file="inc_head.tpl"} with a minimal <!DOCTYPE html><html><body> skeleton. Rejected alternatives: conditional include via Smarty variable (coupling for zero benefit — no dashio consumer needs a standalone head); stripping inc_head.tpl itself (breaks the many templates that legitimately use it).

Blast radius — 4 render paths display this template, all fixed identically:

Path	Trigger
firstLogin.php:29	self-signup disabled notice
lib/general/frmWorkArea.php:234	no-active-build warning
lib/functions/common.php:180	DB connect fatal
lib/functions/info.inc.php:34	displayInfo() ← displayMgr.php:76

Render path exercised through firstLogin.php with $tlCfg->user_self_signup = FALSE set temporarily (untracked fixture, removed afterwards):

State	bytes	<head> tags	<title>	inc_head artifacts (testlink_library.js / <base href> / favicon.ico)
PRE-fix (template restored locally from 9eba4f88f~1)	3165	1	TestLink	ALL present — duplicate reproduced
POST-fix (current tree)	234	0	0	NONE

Post-fix output is the minimal document: single <h1 class="title">, one .workBack block, back-link. Compiled Smarty cache (gui/templates_c/) contains no workAreaSimple artifact referencing inc_head.

Browser checks:

• Legacy /lib/codetrackers/codeTrackerView.php — single <h1>Code Trackers</h1>, no stacking.
• Modernized /gui/templates/codetracker/codetrackerView.html — clean single layout, 1 <head>.

Regression matrix R1–R4 recorded as Suite 434 — 7/7 PASS in tmp/TLU_Test_Cases.md; Event Viewer delta during testing: only 2 AUDIT-level rows (login + self-signup fixture), zero new Error/Warning events.

• Missing template gui/templates/dashio/login/firstLogin.tpl → plain GET /firstLogin.php fatals HTTP 500 under dashio (Smarty "Unable to load template").
• Locale key error_self_signup_disabled missing from all bundles → literal "LOCALIZE:" marker rendered on that notice page.