diff --git a/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.1.expected.json b/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.1.expected.json
index 8529b84ca1..ba1d2e415d 100644
--- a/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.1.expected.json
+++ b/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.1.expected.json
@@ -376,7 +376,7 @@
     },
     {
       "name": "str_replace_editor",
-      "description": "Custom editing tool for viewing, creating and editing files\n* State is persistent across command calls and discussions with the user\n* If `path` is a file, `view` displays the result of applying `cat -n`. If `path` is a directory, `view` lists non-hidden files and directories up to 2 levels deep\n* The `create` command cannot be used if the specified `path` already exists as a file\n* If a `command` generates a long output, it will be truncated and marked with `<response clipped>`\n\nNotes for using the `str_replace` command:\n* The `old_str` parameter should match EXACTLY one or more consecutive lines from the original file. Be mindful of whitespaces!\n* If the `old_str` parameter is not unique in the file, the replacement will not be performed. Make sure to include enough context in `old_str` to make it unique\n* The `new_str` parameter should contain the edited lines that should replace the `old_str`",
+      "description": "Custom editing tool for viewing, creating and editing files\n* State is persistent across command calls and discussions with the user\n* If `path` is a file, `view` displays the result of applying `cat -n`. If `path` is a directory, `view` lists non-hidden files and directories up to 2 levels deep\n* The `create` command cannot be used if the specified `path` already exists as a file\n* If a `command` generates a long output, it will be truncated and marked with `<response clipped>`\n* A null placeholder for a parameter unused by the selected command is treated as omitted. Required parameters still need values; omit `str_replace.new_str` rather than setting it to null when deleting a match\n\nNotes for using the `str_replace` command:\n* The `old_str` parameter should match EXACTLY one or more consecutive lines from the original file. Be mindful of whitespaces!\n* If the `old_str` parameter is not unique in the file, the replacement will not be performed. Make sure to include enough context in `old_str` to make it unique\n* The `new_str` parameter should contain the edited lines that should replace the `old_str`",
       "parameters": {
         "type": "object",
         "properties": {
@@ -395,27 +395,62 @@
             "description": "Absolute path to file or directory, e.g. `/repo/file.py` or `/repo`."
           },
           "file_text": {
-            "type": "string",
-            "description": "Required parameter of `create` command, with the content of the file to be created."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required string parameter of `create` command, with the content of the file to be created. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "insert_line": {
-            "type": "integer",
-            "description": "Required parameter of `insert` command. The `new_str` will be inserted AFTER the line `insert_line` of `path`."
+            "oneOf": [
+              {
+                "type": "integer"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required integer parameter of `insert` command. The `new_str` will be inserted AFTER the line `insert_line` of `path`. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "new_str": {
-            "type": "string",
-            "description": "Optional parameter of `str_replace` command containing the new string (if not given, no string will be added). Required parameter of `insert` command containing the string to insert."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Optional string parameter of `str_replace` command containing the new string (if omitted, no string will be added). Required string parameter of `insert` command containing the string to insert. A null placeholder is accepted only by commands that do not use this parameter."
           },
           "old_str": {
-            "type": "string",
-            "description": "Required parameter of `str_replace` command containing the string in `path` to replace."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required string parameter of `str_replace` command containing the string in `path` to replace. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "view_range": {
-            "type": "array",
-            "description": "Optional parameter of `view` command when `path` points to a file. If none is given, the full file is shown. If provided, the file will be shown in the indicated line number range, e.g. [11, 12] will show lines 11 and 12. Indexing at 1 to start. Setting `[start_line, -1]` shows all lines from `start_line` to the end of the file.",
-            "items": {
-              "type": "integer"
-            }
+            "oneOf": [
+              {
+                "type": "array",
+                "items": {
+                  "type": "integer"
+                }
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Optional parameter of `view` command when `path` points to a file. If omitted or null, the full file is shown. If provided, the file will be shown in the indicated line number range, e.g. [11, 12] will show lines 11 and 12. Indexing at 1 to start. Setting `[start_line, -1]` shows all lines from `start_line` to the end of the file."
           }
         },
         "required": [
diff --git a/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.expected.json b/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.expected.json
index 60fe799c43..3d92e885eb 100644
--- a/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.expected.json
+++ b/snapshots/sdk/subagent-dsh-sdk-dynamic-route/tool-schemas.expected.json
@@ -376,7 +376,7 @@
     },
     {
       "name": "str_replace_editor",
-      "description": "Custom editing tool for viewing, creating and editing files\n* State is persistent across command calls and discussions with the user\n* If `path` is a file, `view` displays the result of applying `cat -n`. If `path` is a directory, `view` lists non-hidden files and directories up to 2 levels deep\n* The `create` command cannot be used if the specified `path` already exists as a file\n* If a `command` generates a long output, it will be truncated and marked with `<response clipped>`\n\nNotes for using the `str_replace` command:\n* The `old_str` parameter should match EXACTLY one or more consecutive lines from the original file. Be mindful of whitespaces!\n* If the `old_str` parameter is not unique in the file, the replacement will not be performed. Make sure to include enough context in `old_str` to make it unique\n* The `new_str` parameter should contain the edited lines that should replace the `old_str`",
+      "description": "Custom editing tool for viewing, creating and editing files\n* State is persistent across command calls and discussions with the user\n* If `path` is a file, `view` displays the result of applying `cat -n`. If `path` is a directory, `view` lists non-hidden files and directories up to 2 levels deep\n* The `create` command cannot be used if the specified `path` already exists as a file\n* If a `command` generates a long output, it will be truncated and marked with `<response clipped>`\n* A null placeholder for a parameter unused by the selected command is treated as omitted. Required parameters still need values; omit `str_replace.new_str` rather than setting it to null when deleting a match\n\nNotes for using the `str_replace` command:\n* The `old_str` parameter should match EXACTLY one or more consecutive lines from the original file. Be mindful of whitespaces!\n* If the `old_str` parameter is not unique in the file, the replacement will not be performed. Make sure to include enough context in `old_str` to make it unique\n* The `new_str` parameter should contain the edited lines that should replace the `old_str`",
       "parameters": {
         "type": "object",
         "properties": {
@@ -395,27 +395,62 @@
             "description": "Absolute path to file or directory, e.g. `/repo/file.py` or `/repo`."
           },
           "file_text": {
-            "type": "string",
-            "description": "Required parameter of `create` command, with the content of the file to be created."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required string parameter of `create` command, with the content of the file to be created. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "insert_line": {
-            "type": "integer",
-            "description": "Required parameter of `insert` command. The `new_str` will be inserted AFTER the line `insert_line` of `path`."
+            "oneOf": [
+              {
+                "type": "integer"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required integer parameter of `insert` command. The `new_str` will be inserted AFTER the line `insert_line` of `path`. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "new_str": {
-            "type": "string",
-            "description": "Optional parameter of `str_replace` command containing the new string (if not given, no string will be added). Required parameter of `insert` command containing the string to insert."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Optional string parameter of `str_replace` command containing the new string (if omitted, no string will be added). Required string parameter of `insert` command containing the string to insert. A null placeholder is accepted only by commands that do not use this parameter."
           },
           "old_str": {
-            "type": "string",
-            "description": "Required parameter of `str_replace` command containing the string in `path` to replace."
+            "oneOf": [
+              {
+                "type": "string"
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Required string parameter of `str_replace` command containing the string in `path` to replace. A null placeholder is treated as omitted by commands that do not use this parameter."
           },
           "view_range": {
-            "type": "array",
-            "description": "Optional parameter of `view` command when `path` points to a file. If none is given, the full file is shown. If provided, the file will be shown in the indicated line number range, e.g. [11, 12] will show lines 11 and 12. Indexing at 1 to start. Setting `[start_line, -1]` shows all lines from `start_line` to the end of the file.",
-            "items": {
-              "type": "integer"
-            }
+            "oneOf": [
+              {
+                "type": "array",
+                "items": {
+                  "type": "integer"
+                }
+              },
+              {
+                "type": "null"
+              }
+            ],
+            "description": "Optional parameter of `view` command when `path` points to a file. If omitted or null, the full file is shown. If provided, the file will be shown in the indicated line number range, e.g. [11, 12] will show lines 11 and 12. Indexing at 1 to start. Setting `[start_line, -1]` shows all lines from `start_line` to the end of the file."
           }
         },
         "required": [