diff --git a/robot/coverage_threshold.robot b/robot/coverage_threshold.robot
index 2d4180f9f..0e952368f 100644
--- a/robot/coverage_threshold.robot
+++ b/robot/coverage_threshold.robot
@@ -8,11 +8,17 @@ Suite Teardown    Cleanup Test Environment
 
 *** Test Cases ***
 Noxfile Contains Coverage Threshold Constant
-    [Documentation]    Verify COVERAGE_THRESHOLD = 96.5 is defined in noxfile.py
+    [Documentation]    Verify COVERAGE_THRESHOLD resolves the floor (96.5) from
+    ...                pyproject's single source [tool.coverage.report].fail_under
     [Tags]    coverage    config    tdd_issue    tdd_issue_4305
 
+    # WS5: the noxfile delegates the constant to pyproject's single source
+    # (COVERAGE_THRESHOLD = _read_coverage_fail_under()), so assert the
+    # delegation plus the pyproject floor rather than a hardcoded literal.
     ${content}=    Get File    ${WORKSPACE}/noxfile.py
-    Should Contain    ${content}    COVERAGE_THRESHOLD = 96.5
+    Should Contain    ${content}    COVERAGE_THRESHOLD = _read_coverage_fail_under()
+    ${pyproject}=    Get File    ${WORKSPACE}/pyproject.toml
+    Should Contain    ${pyproject}    fail_under = 96.5
 
 Pyproject Contains Coverage Run Section
     [Documentation]    Verify [tool.coverage.run] section exists in pyproject.toml