diff --git a/lib/galaxy/tool_util/parameters/convert.py b/lib/galaxy/tool_util/parameters/convert.py
index f5e5970f769..b2d544c541c 100644
--- a/lib/galaxy/tool_util/parameters/convert.py
+++ b/lib/galaxy/tool_util/parameters/convert.py
@@ -195,14 +195,14 @@ def strictify(relaxed_state: RelaxedRequestToolState, input_models: ToolParamete
                 if not parameter.optional:
                     # restore legacy behavior of allowing empty string implicit default
                     # for these non-optional inputs.
-                    tool_state[parameter_name] = ""
+                    tool_state[parameter_name] = parameter.default_value if parameter.default_value is not None else ""
                 else:
-                    tool_state[parameter_name] = None
+                    tool_state[parameter_name] = parameter.default_value
             else:
                 # legacy behavior of converting explicit None into implicit null. We should introduce
                 # a layer somewhere to deal with this behavior further up the stack and clean up these models.
                 if not parameter.optional and tool_state[parameter_name] is None:
-                    tool_state[parameter_name] = ""
+                    tool_state[parameter_name] = parameter.default_value if parameter.default_value is not None else ""
 
     def _strictify_parameters(tool_state: Dict[str, Any], input_models: ToolParameterBundle) -> None:
         for parameter in input_models.parameters:
@@ -399,14 +399,14 @@ def _fill_default_for(tool_state: Dict[str, Any], parameter: ToolParameterT) ->
             if not parameter.optional:
                 # restore legacy behavior of allowing empty string implicit default
                 # for these non-optional inputs.
-                tool_state[parameter_name] = parameter.default_value or ""
+                tool_state[parameter_name] = parameter.default_value if parameter.default_value is not None else ""
             else:
-                tool_state[parameter_name] = parameter.default_value or None
+                tool_state[parameter_name] = parameter.default_value
         else:
             # legacy behavior of converting explicit None into implicit null. We should introduce
             # a layer somewhere to deal with this behavior further up the stack and clean up these models.
             if not parameter.optional and tool_state[parameter_name] is None:
-                tool_state[parameter_name] = parameter.default_value or ""
+                tool_state[parameter_name] = parameter.default_value if parameter.default_value is not None else ""
 
 
 def _initialize_section_state(parameter: SectionParameterModel, tool_state: Dict[str, Any]) -> Dict[str, Any]:
diff --git a/lib/galaxy_test/api/test_tool_execute.py b/lib/galaxy_test/api/test_tool_execute.py
index 8d776d74519..5a430c49e38 100644
--- a/lib/galaxy_test/api/test_tool_execute.py
+++ b/lib/galaxy_test/api/test_tool_execute.py
@@ -735,15 +735,58 @@ def test_null_to_text_tool_with_validation(required_tool: RequiredTool, tool_inp
     required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": ""})).assert_fails()
 
 
+@requires_tool_id("gx_text_optional_with_empty_default")
+def test_optional_text_with_empty_default(required_tool: RequiredTool, tool_input_format: DescribeToolInputs):
+    # absent — all formats resolve to value="" default
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": ""})
+
+    # explicit null
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": None}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": None})
+
+    # explicit empty string
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": ""}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": ""})
+
+    # provided value
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": "hello"}))
+    execute.assert_has_single_job.with_output("output").with_contents_stripped("hello")
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": "hello"})
+
+
 @requires_tool_id("gx_text_optional_regex_validation")
 def test_optional_text_with_regex_validation(required_tool: RequiredTool, tool_input_format: DescribeToolInputs):
-    # absent param — legacy/21.01 resolve to value="" default, runtime skips regex for empty optional
+    # absent — no value="" default so all formats treat as None
     execute = required_tool.execute().with_inputs(tool_input_format.when.any({}))
-    execute.assert_has_single_job.with_output("inputs_json").with_json(
-        {"parameter": None} if tool_input_format.is_request else {"parameter": ""}
-    )
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": None})
 
-    # explicit null — all formats treat as "not provided" for optional
+    # explicit null
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": None}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": None})
+
+    # explicit empty string — optional so skip regex validation, "" stays as ""
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": ""}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": ""})
+
+    # valid value
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": "0.5"}))
+    execute.assert_has_single_job.with_output("output").with_contents_stripped("0.5")
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": "0.5"})
+
+    # invalid value should fail regardless of format
+    required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": "abc"})).assert_fails()
+
+
+@requires_tool_id("gx_text_optional_with_empty_default_regex_validation")
+def test_optional_text_with_empty_default_with_regex_validation(
+    required_tool: RequiredTool, tool_input_format: DescribeToolInputs
+):
+    # absent — all formats resolve to value="" default
+    execute = required_tool.execute().with_inputs(tool_input_format.when.any({}))
+    execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": ""})
+
+    # explicit null
     execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": None}))
     execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": None})
 
@@ -751,7 +794,7 @@ def test_optional_text_with_regex_validation(required_tool: RequiredTool, tool_i
     execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": ""}))
     execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": ""})
 
-    # valid value should pass all formats
+    # valid value
     execute = required_tool.execute().with_inputs(tool_input_format.when.any({"parameter": "0.5"}))
     execute.assert_has_single_job.with_output("output").with_contents_stripped("0.5")
     execute.assert_has_single_job.with_output("inputs_json").with_json({"parameter": "0.5"})
diff --git a/test/functional/tools/parameters/gx_text_optional_regex_validation.xml b/test/functional/tools/parameters/gx_text_optional_regex_validation.xml
index 514b8c5389c..0c0d432092d 100644
--- a/test/functional/tools/parameters/gx_text_optional_regex_validation.xml
+++ b/test/functional/tools/parameters/gx_text_optional_regex_validation.xml
@@ -7,7 +7,7 @@ cat '$inputs' >> $inputs_json;
         <inputs name="inputs" filename="inputs.json" />
     </configfiles>
     <inputs>
-        <param name="parameter" type="text" value="" optional="true">
+        <param name="parameter" type="text" optional="true">
             <validator type="regex">[0-9.:]+</validator>
         </param>
     </inputs>
diff --git a/test/functional/tools/parameters/gx_text_optional_with_empty_default.xml b/test/functional/tools/parameters/gx_text_optional_with_empty_default.xml
new file mode 100644
index 00000000000..2c9ae2fd65c
--- /dev/null
+++ b/test/functional/tools/parameters/gx_text_optional_with_empty_default.xml
@@ -0,0 +1,18 @@
+<tool id="gx_text_optional_with_empty_default" name="gx_text_optional_with_empty_default" version="1.0.0">
+    <command><![CDATA[
+echo '$parameter' >> '$output';
+cat '$inputs' >> $inputs_json;
+    ]]></command>
+    <configfiles>
+        <inputs name="inputs" filename="inputs.json" />
+    </configfiles>
+    <inputs>
+        <param name="parameter" type="text" value="" optional="true" />
+    </inputs>
+    <outputs>
+        <data name="output" format="txt" />
+        <data name="inputs_json" format="json" />
+    </outputs>
+    <tests>
+    </tests>
+</tool>
diff --git a/test/functional/tools/parameters/gx_text_optional_with_empty_default_regex_validation.xml b/test/functional/tools/parameters/gx_text_optional_with_empty_default_regex_validation.xml
new file mode 100644
index 00000000000..936e5d7ac72
--- /dev/null
+++ b/test/functional/tools/parameters/gx_text_optional_with_empty_default_regex_validation.xml
@@ -0,0 +1,20 @@
+<tool id="gx_text_optional_with_empty_default_regex_validation" name="gx_text_optional_with_empty_default_regex_validation" version="1.0.0">
+    <command><![CDATA[
+echo '$parameter' >> '$output';
+cat '$inputs' >> $inputs_json;
+    ]]></command>
+    <configfiles>
+        <inputs name="inputs" filename="inputs.json" />
+    </configfiles>
+    <inputs>
+        <param name="parameter" type="text" value="" optional="true">
+            <validator type="regex">[0-9.:]+</validator>
+        </param>
+    </inputs>
+    <outputs>
+        <data name="output" format="txt" />
+        <data name="inputs_json" format="json" />
+    </outputs>
+    <tests>
+    </tests>
+</tool>