The modernized Execute Tests screen (gui/templates/execute/execTest.html + api/execute/index.php) dropped the legacy test-case tester assignment feature entirely. On an unassigned test case the tester could previously:

• see a "No tester assigned" warning in the test-case header (execTCaseHeader.inc.tpl:58-66),
• tick an "Assign task to me" checkbox (inc_exec_controls.tpl:55-60), which on save created a user_assignments row (execSetResults.php:208-219) with type=testcase_execution, status=open,
• later see "Assigned to: " in the header.

The 2.0.1 rewrite rendered none of that: execTest.html contained zero assign/assigned references, the BFF tcDetails response had no assigned_user, and save never called assignment_mgr.

• gui/templates/tl-classic/execute/inc_exec_controls.tpl:55-60 — renders the assignTask checkbox when $tc_exec.assigned_user == '' (single-save mode).
• gui/templates/tl-classic/execute/execTCaseHeader.inc.tpl:58-66 — renders warning icon has_no_assignment, or the assigned_to label + assignee name.
• lib/execute/execSetResults.php:208-219 — on save with $args->assignTask: $fid = $tplan_mgr->getFeatureID($tplan_id, $platform_id, $version_id) (testplan.class.php:825 → the testplan_tcversions.id row) then assignment_mgr->assign([$fid => [user_id, assigner_id, build_id, type=testcase_execution, status=open]]).
• Assignment read back via testcase::get_version_exec_assignment($tcversion_id, $tplan_id, $build_id) (testcase.class.php:4623) joining user_assignments on feature_id = testplan_tcversions.id.

1. api/execute/index.php ?action=tcDetails (lines 1021-1040) built its response with keys status, tcase, linked_bugs, version, steps, prior_execution, prior_step_results, exec_history — no assignment query, no assigned_user/assigned_user_id. Verified live: the response had neither field.
2. ?action=save (lines 1047-1315) mapped the payload onto write_execution() but had no assign_task handling and no assignment_mgr usage anywhere in the file.
3. gui/templates/execute/execTest.html renderForm() (lines 699-864) never rendered an assignee line or checkbox; saveExecution() never sent the flag.

Blast radius: only this screen consumes assignment data on the Execute path; tcExecAssignment.html / tcAssignments.html have their own API routes and were unaffected. No other modernized screen touches assignment_mgr.

Backend — api/execute/index.php:

• ?action=tcDetails: resolves the assignment of the current version in the plan+build+platform context through the same lookup legacy uses (testcase::get_version_exec_assignment()), builds comma-joined display names and ids (via tlUser::getByID() + getDisplayName()), and returns assigned_user + assigned_user_id (both empty strings when unassigned). Wrapped in try/catch so assignment lookup can never break the details load.
• ?action=save: new optional assign_task payload (1/true/on/yes). When set, computes $fid = $tplanMgr->getFeatureID($tplanId, platformNorm, $tcversionId) and creates the row via assignment_mgr->assign() with type=testcase_execution, status=open, build_id, user_id=assigner_id= $userId — replicating execSetResults.php:208-219. assignment_mgr->assign() is idempotent (skips present rows), so re-checking on a later save cannot duplicate. Platform normalization: the frontend sends platform_id=-1 for no-platform plans while assignments store platform_id=0 → normalize before getFeatureID(). Assignment creation is wrapped in try/catch (best-effort side effect, never fails the execution write).

Frontend — gui/templates/execute/execTest.html:

• renderForm(): right under the form title/meta, if current.assigned_user is empty renders the warning box "⚠ No tester assigned" plus (writable mode only) an "Assign task to me" checkbox; otherwise renders "👤 Assigned to: ". Mirrors execTCaseHeader.inc.tpl:58-66.
• saveExecution(): appends assign_task=1 to the FormData payload when the box is checked (same pattern as copyAttFromLEXEC).

i18n: added exe.assignedTo ("Assigned to"), exe.assignTaskToMe ("Assign task to me") and exe.noTesterAssigned ("No tester assigned") to all 10 locale bundles (de,en,es,fr,it,ja,pt,ro,ru,zh); every bundle validated with python3 -m json.tool.

• Minimal / legacy-parity: reuse the exact legacy read and write helpers (get_version_exec_assignment, getFeatureID, assignment_mgr->assign) — no schema change, no new endpoint, no new classes.
• Idempotent by construction: assignment_mgr->assign() already skips existing rows, matching legacy's expectations.
• Alternatives rejected: adding assignment management UI (edit/remove assignees) belongs to the dedicated tcExecAssignment screen; the Execute form only needs the claim-or-display behavior legacy had.

• api/execute/index.php — tcDetails (assignment fields), save (assign_task handling).
• gui/templates/execute/execTest.html — assignee/warning display, checkbox, payload append.
• gui/templates/i18n/{de,en,es,fr,it,ja,pt,ro,ru,zh}.json — 3 new keys each.
• tmp/TLU_Test_Cases.md — TC-790.1–790.9 (9/9 PASS).

Unassigned test case before the fix — no warning, no checkbox:

After the fix, unassigned case: warning + "Assign task to me" checkbox:

After checking the box and saving, reopening shows the assignee:

• 946dde82b — fix(execute): restore assign-execution-task in tcDetails and save (Refs #790)
• 5ee0b8d4e — fix(execute): assign-task checkbox, assignee display and i18n keys (Refs #790)
• 80821e171 — test(execute): add regression suite TC-790.1-9 for assign-execution-task (Refs #790)

#	Case	Result
1	tcDetails returns assigned_user/assigned_user_id (empty when unassigned)	PASS
2	Unassigned case: "No tester assigned" warning + "Assign task to me" checkbox render	PASS
3	Check box + Passed + Save → one user_assignments row (user 1, build 1, type 1, status 1, feature_id = plan link)	PASS
4	Reopen → "Assigned to: Testlink Administrator", checkbox gone, API returns the names/ids	PASS
5	Save WITHOUT the box → no user_assignments row	PASS
6	Re-check and save twice → still exactly one row (idempotent)	PASS
7	No-platform plans (platform_id=-1) normalize to storage 0 for lookup + creation	PASS
8	All 10 i18n bundles valid JSON and contain the 3 new keys	PASS
9	Event Viewer events table: no new Error/Warning from the fix	PASS

Verified 2026-09-01 with fresh fixtures (project Demo Project id=1, plan Demo Plan id=2, case Login Test tcversion 5, build Build A id=1, testplan_tcversions.id=1), headless Chrome at http://localhost:8082, admin/admin. Browser console clean (only pre-existing a11y notices), events table only INFO audit rows.