diff --git a/CHANGELOG.md b/CHANGELOG.md
index c798a79..c52f7e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## unreleased
 
 - CLI: Fix YAML output to preserve x-version number formatting
+- Casing - Configure characters to keep
 
 ## [1.31.0] - 2026-04-12
 
diff --git a/openapi-format.js b/openapi-format.js
index 84101fa..31faf66 100644
--- a/openapi-format.js
+++ b/openapi-format.js
@@ -889,23 +889,24 @@ async function openapiChangeCase(oaObj, options) {
   let jsonObj = JSON.parse(JSON.stringify(oaObj)); // Deep copy of the schema object
   let defaultCasing = {}; // JSON.parse(fs.readFileSync(__dirname + "/defaultFilter.json", 'utf8'))
   let casingSet = Object.assign({}, defaultCasing, options.casingSet);
+  const getKeepChars = target => casingSet[`${target}KeepChars`];
 
   let debugCasingStep = ''; // uncomment // debugCasingStep below to see which sort part is triggered
 
   // Could add a default for all types pretty easily.
   const changeCasingKeyPlans = {
-    query: casingSet.componentsParametersQuery,
-    path: casingSet.componentsParametersPath,
-    header: casingSet.componentsParametersHeader,
-    cookie: casingSet.componentsParametersCookie
+    query: {case: casingSet.componentsParametersQuery, keep: getKeepChars('componentsParametersQuery')},
+    path: {case: casingSet.componentsParametersPath, keep: getKeepChars('componentsParametersPath')},
+    header: {case: casingSet.componentsParametersHeader, keep: getKeepChars('componentsParametersHeader')},
+    cookie: {case: casingSet.componentsParametersCookie, keep: getKeepChars('componentsParametersCookie')}
   };
 
   // Could add a default for all types pretty easily.
   const changeCasingNamePlans = {
-    query: casingSet.parametersQuery,
-    path: casingSet.parametersPath,
-    header: casingSet.parametersHeader,
-    cookie: casingSet.parametersCookie
+    query: {case: casingSet.parametersQuery, keep: getKeepChars('parametersQuery')},
+    path: {case: casingSet.parametersPath, keep: getKeepChars('parametersPath')},
+    header: {case: casingSet.parametersHeader, keep: getKeepChars('parametersHeader')},
+    cookie: {case: casingSet.parametersCookie, keep: getKeepChars('parametersCookie')}
   };
 
   // Initiate components tracking
@@ -920,17 +921,17 @@ async function openapiChangeCase(oaObj, options) {
       // Change components/schemas - names
       if (this.path[1] === 'schemas' && this.path.length === 2 && casingSet.componentsSchemas) {
         // debugCasingStep = 'Casing - components/schemas - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsSchemas));
+        this.update(changeObjKeysCase(node, casingSet.componentsSchemas, getKeepChars('componentsSchemas')));
       }
       // Change components/examples - names
       if (this.path[1] === 'examples' && this.path.length === 2 && casingSet.componentsExamples) {
         // debugCasingStep = 'Casing - components/examples - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsExamples));
+        this.update(changeObjKeysCase(node, casingSet.componentsExamples, getKeepChars('componentsExamples')));
       }
       // Change components/headers - names
       if (this.path[1] === 'headers' && this.path.length === 2 && casingSet.componentsHeaders) {
         // debugCasingStep = 'Casing - components/headers - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsHeaders));
+        this.update(changeObjKeysCase(node, casingSet.componentsHeaders, getKeepChars('componentsHeaders')));
       }
       // Change components/parameters - in:query/in:headers/in:path/in:cookie - key
       if (
@@ -945,7 +946,7 @@ async function openapiChangeCase(oaObj, options) {
             const changeCasingKeyPlan = changeCasingKeyPlans[parameterFoundIn];
             if (changeCasingKeyPlan) {
               // debugCasingStep = `Casing - components/parameters - in:${parameterFoundIn} - key`
-              const newKey = changeCase(key, changeCasingKeyPlan);
+              const newKey = changeCase(key, changeCasingKeyPlan.case, changeCasingKeyPlan.keep);
               comps.parameters[key] = newKey;
               return {[newKey]: orgObj[key]};
             }
@@ -957,9 +958,9 @@ async function openapiChangeCase(oaObj, options) {
       if (this.path[1] === 'parameters' && this.path.length === 3) {
         if (node.in && changeCasingNamePlans.hasOwnProperty(node.in)) {
           const changeCasingNamePlan = changeCasingNamePlans[node.in];
-          if (changeCasingNamePlan) {
+          if (changeCasingNamePlan.case) {
             // debugCasingStep = `Casing - path > parameters/${node.in} - name`
-            node.name = changeCase(node.name, changeCasingNamePlan);
+            node.name = changeCase(node.name, changeCasingNamePlan.case, changeCasingNamePlan.keep);
             this.update(node);
           }
         }
@@ -967,17 +968,21 @@ async function openapiChangeCase(oaObj, options) {
       // Change components/responses - names
       if (this.path[1] === 'responses' && this.path.length === 2 && casingSet.componentsResponses) {
         // debugCasingStep = 'Casing - components/responses - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsResponses));
+        this.update(changeObjKeysCase(node, casingSet.componentsResponses, getKeepChars('componentsResponses')));
       }
       // Change components/requestBodies - names
       if (this.path[1] === 'requestBodies' && this.path.length === 2 && casingSet.componentsRequestBodies) {
         // debugCasingStep = 'Casing - components/requestBodies - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsRequestBodies));
+        this.update(
+          changeObjKeysCase(node, casingSet.componentsRequestBodies, getKeepChars('componentsRequestBodies'))
+        );
       }
       // Change components/securitySchemes - names
       if (this.path[1] === 'securitySchemes' && this.path.length === 2 && casingSet.componentsSecuritySchemes) {
         // debugCasingStep = 'Casing - components/securitySchemes - names'
-        this.update(changeObjKeysCase(node, casingSet.componentsSecuritySchemes));
+        this.update(
+          changeObjKeysCase(node, casingSet.componentsSecuritySchemes, getKeepChars('componentsSecuritySchemes'))
+        );
       }
     }
   });
@@ -988,15 +993,29 @@ async function openapiChangeCase(oaObj, options) {
     if (this.key === '$ref') {
       if (node.startsWith('#/components/schemas/') && casingSet.componentsSchemas) {
         const compName = node.replace('#/components/schemas/', '');
-        this.update(`#/components/schemas/${changeCase(compName, casingSet.componentsSchemas)}`);
+        this.update(
+          `#/components/schemas/${changeCase(compName, casingSet.componentsSchemas, getKeepChars('componentsSchemas'))}`
+        );
       }
       if (node.startsWith('#/components/examples/') && casingSet.componentsExamples) {
         const compName = node.replace('#/components/examples/', '');
-        this.update(`#/components/examples/${changeCase(compName, casingSet.componentsExamples)}`);
+        this.update(
+          `#/components/examples/${changeCase(
+            compName,
+            casingSet.componentsExamples,
+            getKeepChars('componentsExamples')
+          )}`
+        );
       }
       if (node.startsWith('#/components/responses/') && casingSet.componentsResponses) {
         const compName = node.replace('#/components/responses/', '');
-        this.update(`#/components/responses/${changeCase(compName, casingSet.componentsResponses)}`);
+        this.update(
+          `#/components/responses/${changeCase(
+            compName,
+            casingSet.componentsResponses,
+            getKeepChars('componentsResponses')
+          )}`
+        );
       }
       if (node.startsWith('#/components/parameters/')) {
         const compName = node.replace('#/components/parameters/', '');
@@ -1006,37 +1025,51 @@ async function openapiChangeCase(oaObj, options) {
       }
       if (node.startsWith('#/components/headers/') && casingSet.componentsHeaders) {
         const compName = node.replace('#/components/headers/', '');
-        this.update(`#/components/headers/${changeCase(compName, casingSet.componentsHeaders)}`);
+        this.update(
+          `#/components/headers/${changeCase(compName, casingSet.componentsHeaders, getKeepChars('componentsHeaders'))}`
+        );
       }
       if (node.startsWith('#/components/requestBodies/') && casingSet.componentsRequestBodies) {
         const compName = node.replace('#/components/requestBodies/', '');
-        this.update(`#/components/requestBodies/${changeCase(compName, casingSet.componentsRequestBodies)}`);
+        this.update(
+          `#/components/requestBodies/${changeCase(
+            compName,
+            casingSet.componentsRequestBodies,
+            getKeepChars('componentsRequestBodies')
+          )}`
+        );
       }
       if (node.startsWith('#/components/securitySchemes/') && casingSet.componentsSecuritySchemes) {
         const compName = node.replace('#/components/securitySchemes/', '');
-        this.update(`#/components/securitySchemes/${changeCase(compName, casingSet.componentsSecuritySchemes)}`);
+        this.update(
+          `#/components/securitySchemes/${changeCase(
+            compName,
+            casingSet.componentsSecuritySchemes,
+            getKeepChars('componentsSecuritySchemes')
+          )}`
+        );
       }
     }
 
     // Change operationId
     if (this.key === 'operationId' && casingSet.operationId && this.path[0] === 'paths' && this.path.length === 4) {
       // debugCasingStep = 'Casing - Single field - OperationId'
-      this.update(changeCase(node, casingSet.operationId));
+      this.update(changeCase(node, casingSet.operationId, getKeepChars('operationId')));
     }
     // Change summary
     if (this.key === 'summary' && casingSet.summary) {
       // debugCasingStep = 'Casing - Single field - summary'
-      this.update(changeCase(node, casingSet.summary));
+      this.update(changeCase(node, casingSet.summary, getKeepChars('summary')));
     }
     // Change description
     if (this.key === 'description' && casingSet.description) {
       // debugCasingStep = 'Casing - Single field - description'
-      this.update(changeCase(node, casingSet.description));
+      this.update(changeCase(node, casingSet.description, getKeepChars('description')));
     }
     // Change paths > examples - name
     if (this.path[0] === 'paths' && this.key === 'examples' && casingSet.componentsExamples) {
       // debugCasingStep = 'Casing - Single field - examples name'
-      this.update(changeObjKeysCase(node, casingSet.componentsExamples));
+      this.update(changeObjKeysCase(node, casingSet.componentsExamples, getKeepChars('componentsExamples')));
     }
     // Change components/schemas - properties
     if (
@@ -1048,12 +1081,12 @@ async function openapiChangeCase(oaObj, options) {
       this.parent.key !== 'value'
     ) {
       // debugCasingStep = 'Casing - components/schemas - properties name'
-      this.update(changeObjKeysCase(node, casingSet.properties));
+      this.update(changeObjKeysCase(node, casingSet.properties, getKeepChars('properties')));
     }
     // Change components/schemas - required properties
     if (this.path[1] === 'schemas' && this.parent.key === 'required' && casingSet.properties) {
       // debugCasingStep = 'Casing - components/schemas - required properties'
-      this.update(changeCase(node, casingSet.properties));
+      this.update(changeCase(node, casingSet.properties, getKeepChars('properties')));
     }
     // Change paths > schema - properties
     if (
@@ -1065,12 +1098,14 @@ async function openapiChangeCase(oaObj, options) {
       this.parent.key !== 'value'
     ) {
       // debugCasingStep = 'Casing - paths > schema - properties name'
-      this.update(changeObjKeysCase(node, casingSet.properties));
+      this.update(changeObjKeysCase(node, casingSet.properties, getKeepChars('properties')));
     }
     // Change security - keys
     if (this.path[0] === 'paths' && this.key === 'security' && isArray(node) && casingSet.componentsSecuritySchemes) {
       // debugCasingStep = 'Casing - path > - security'
-      this.update(changeArrayObjKeysCase(node, casingSet.componentsSecuritySchemes));
+      this.update(
+        changeArrayObjKeysCase(node, casingSet.componentsSecuritySchemes, getKeepChars('componentsSecuritySchemes'))
+      );
     }
     // Change parameters - name
     if (this.path[0] === 'paths' && this.key === 'parameters' && changeParametersCasingEnabled(casingSet)) {
@@ -1081,9 +1116,9 @@ async function openapiChangeCase(oaObj, options) {
       for (let i = 0; i < params.length; i++) {
         if (params[i].in && changeCasingNamePlans.hasOwnProperty(params[i].in)) {
           const changeCasingNamePlan = changeCasingNamePlans[params[i].in];
-          if (changeCasingNamePlan) {
+          if (changeCasingNamePlan.case) {
             // debugCasingStep = 'Casing - path > parameters/query- name'
-            params[i].name = changeCase(params[i].name, changeCasingNamePlan);
+            params[i].name = changeCase(params[i].name, changeCasingNamePlan.case, changeCasingNamePlan.keep);
           }
         }
       }
diff --git a/readme.md b/readme.md
index fbf69e8..57901e4 100644
--- a/readme.md
+++ b/readme.md
@@ -1327,11 +1327,17 @@ In this example, the customCasing.yaml file would contain the desired casing pre
 
 ```yaml
 operationId: snake_case
+operationIdKeepChars:
+  - .
 properties: camelCase
+propertiesKeepChars:
+  - .
 
 parametersQuery: kebab-case
 parametersHeader: kebab-case
 parametersPath: snake_case
+parametersQueryKeepChars:
+  - .
 
 componentsExamples: PascalCase
 componentsSchemas: camelCase
@@ -1343,14 +1349,20 @@ componentsSecuritySchemes: PascalCase
 componentsParametersQuery: snake_case
 componentsParametersHeader: kebab-case
 componentsParametersPath: camelCase
+componentsParametersQueryKeepChars:
+  - .
 ```
 
 **Casing Options:**
 In the customCasing.yaml, you can define the casing style for various OpenAPI properties, allowing you to customize the appearance of your document consistently.
 
 - `operationId`: Defines the casing for operation IDs. Example: snake_case, PascalCase, or camelCase.
+- `operationIdKeepChars`: Keeps selected characters while casing `operationId`. Example: `.` for dotted identifiers.
 - `properties`: Sets the casing for properties within components. Example: camelCase.
-- `parametersQuery`, `parametersHeader`, `parametersPath`: Define different casing styles for parameters based on their location (query, header, path). Example: snake_case, kebab-case.
+- `propertiesKeepChars`: Keeps selected characters while casing properties. Example: `.`.
+- `parametersQuery`, `parametersHeader`, `parametersPath`, `parametersCookie`: Define different casing styles for parameters based on their location (query, header, path, cookie). Example: snake_case, kebab-case.
+- `parametersQueryKeepChars`, `parametersHeaderKeepChars`, `parametersPathKeepChars`, `parametersCookieKeepChars`: Keep selected characters while casing inline parameters.
+- `componentsParametersQueryKeepChars`, `componentsParametersHeaderKeepChars`, `componentsParametersPathKeepChars`, `componentsParametersCookieKeepChars`: Keep selected characters while casing referenced parameters in `components.parameters`.
 - and many more
 
 See [OpenAPI formatting configuration options](#openapi-formatting-configuration-options) for the full list of casing options
@@ -1713,4 +1725,4 @@ The casing options available in `openapi-format` are powered by the excellent [c
 <img src="https://resources.jetbrains.com/storage/products/company/brand/logos/jetbrains.png" alt="JetBrains logo." width="200px">
 </a>
 
-Special thanks to [JetBrains](https://www.jetbrains.com/) for their continuous sponsorship of this project over the last 3 years, and for their support to open-source software (OSS) initiatives.
\ No newline at end of file
+Special thanks to [JetBrains](https://www.jetbrains.com/) for their continuous sponsorship of this project over the last 3 years, and for their support to open-source software (OSS) initiatives.
diff --git a/skills/openapi-format/references/feature-matrix.md b/skills/openapi-format/references/feature-matrix.md
index 82ddc6d..f0bfa53 100644
--- a/skills/openapi-format/references/feature-matrix.md
+++ b/skills/openapi-format/references/feature-matrix.md
@@ -4,20 +4,20 @@ This matrix summarizes CLI/config options, defaults, and notable interactions.
 
 ## Input and output
 
-| Option | Type | Default | Effect | Notes |
-|---|---|---|---|---|
-| `oaFile` | argument | required unless overlay `extends` | Input OpenAPI/AsyncAPI source | Supports local path and remote URL.
-| `--output`, `-o` | path | none | Write output to file or split root | Required for `--split`.
-| `--json` | boolean | false | Print stdout as JSON | Affects stdout formatting when no output file is given.
-| `--yaml` | boolean | false | Print stdout as YAML | Affects stdout formatting when no output file is given.
+| Option           | Type     | Default                           | Effect                             | Notes                                                   |
+|------------------|----------|-----------------------------------|------------------------------------|---------------------------------------------------------|
+| `oaFile`         | argument | required unless overlay `extends` | Input OpenAPI/AsyncAPI source      | Supports local path and remote URL.                     |
+| `--output`, `-o` | path     | none                              | Write output to file or split root | Required for `--split`.                                 |
+| `--json`         | boolean  | false                             | Print stdout as JSON               | Affects stdout formatting when no output file is given. |
+| `--yaml`         | boolean  | false                             | Print stdout as YAML               | Affects stdout formatting when no output file is given. |
 
 ## Config loading and precedence
 
-| Source | Applied when | Priority |
-|---|---|---|
-| `.openapiformatrc` in CWD | only when `--configFile` is absent | lowest |
-| `--configFile` | when provided | middle |
-| CLI flags | always | highest |
+| Source                    | Applied when                       | Priority |
+|---------------------------|------------------------------------|----------|
+| `.openapiformatrc` in CWD | only when `--configFile` is absent | lowest   |
+| `--configFile`            | when provided                      | middle   |
+| CLI flags                 | always                             | highest  |
 
 Normalization behavior:
 - `--no-sort` sets `sort=false`.
@@ -33,37 +33,37 @@ Defaults with explicit fallback logic:
 
 ## Sorting
 
-| Option | Type | Default | Effect | Notes |
-|---|---|---|---|---|
-| `--sortFile`, `-s` | path | `defaultSort.json` | Field order priorities | Used when `sort=true`.
-| `--no-sort` | boolean | false | Disable sorting | Skips sort stage entirely.
-| `--sortComponentsFile` | path | none | Alphabetize listed component groups | See `defaultSortComponents.json`.
-| `--sortComponentsProps` | boolean | false | Alphabetize schema properties in components | Scope is `components.schemas.*.properties`.
-| `sortSet.sortPathsBy` | enum | `original` | Path order mode | Values: `original`, `path`, `tags`.
+| Option                  | Type    | Default            | Effect                                      | Notes                                       |
+|-------------------------|---------|--------------------|---------------------------------------------|---------------------------------------------|
+| `--sortFile`, `-s`      | path    | `defaultSort.json` | Field order priorities                      | Used when `sort=true`.                      |
+| `--no-sort`             | boolean | false              | Disable sorting                             | Skips sort stage entirely.                  |
+| `--sortComponentsFile`  | path    | none               | Alphabetize listed component groups         | See `defaultSortComponents.json`.           |
+| `--sortComponentsProps` | boolean | false              | Alphabetize schema properties in components | Scope is `components.schemas.*.properties`. |
+| `sortSet.sortPathsBy`   | enum    | `original`         | Path order mode                             | Values: `original`, `path`, `tags`.         |
 
 ## Filtering
 
-| Key | Type | Semantics |
-|---|---|---|
-| `methods` | string[] | Remove matching HTTP methods from path items |
-| `inverseMethods` | string[] | Keep only matching methods |
-| `tags` | string[] | Remove operations/tag entries with matching tags |
-| `inverseTags` | string[] | Keep operations/tag entries with matching tags |
-| `operationIds` | string[] | Remove matching operationIds |
-| `inverseOperationIds` | string[] | Keep only matching operationIds |
-| `operations` | string[] | Remove matching `path#method` patterns |
-| `flags` | string[] | Remove objects containing matching marker keys |
-| `inverseFlags` | string[] | Keep objects containing matching marker keys |
-| `flagValues` | object[] | Remove objects/values matching key-value markers |
-| `inverseFlagValues` | object[] | Keep objects matching marker key-values |
-| `responseContent` | string[] | Remove matching response media types |
-| `inverseResponseContent` | string[] | Keep only matching response media types |
-| `requestContent` | string[] | Remove matching request media types |
-| `inverseRequestContent` | string[] | Keep only matching request media types |
-| `unusedComponents` | string[] | Remove unreferenced components recursively |
-| `stripFlags` | string[] | Remove flag keys after filtering |
-| `textReplace` | object[] | Replace text in `description`, `summary`, and `url` |
-| `preserveEmptyObjects` | boolean/string[] | Preserve selected empty objects instead of pruning |
+| Key                      | Type             | Semantics                                           |
+|--------------------------|------------------|-----------------------------------------------------|
+| `methods`                | string[]         | Remove matching HTTP methods from path items        |
+| `inverseMethods`         | string[]         | Keep only matching methods                          |
+| `tags`                   | string[]         | Remove operations/tag entries with matching tags    |
+| `inverseTags`            | string[]         | Keep operations/tag entries with matching tags      |
+| `operationIds`           | string[]         | Remove matching operationIds                        |
+| `inverseOperationIds`    | string[]         | Keep only matching operationIds                     |
+| `operations`             | string[]         | Remove matching `path#method` patterns              |
+| `flags`                  | string[]         | Remove objects containing matching marker keys      |
+| `inverseFlags`           | string[]         | Keep objects containing matching marker keys        |
+| `flagValues`             | object[]         | Remove objects/values matching key-value markers    |
+| `inverseFlagValues`      | object[]         | Keep objects matching marker key-values             |
+| `responseContent`        | string[]         | Remove matching response media types                |
+| `inverseResponseContent` | string[]         | Keep only matching response media types             |
+| `requestContent`         | string[]         | Remove matching request media types                 |
+| `inverseRequestContent`  | string[]         | Keep only matching request media types              |
+| `unusedComponents`       | string[]         | Remove unreferenced components recursively          |
+| `stripFlags`             | string[]         | Remove flag keys after filtering                    |
+| `textReplace`            | object[]         | Replace text in `description`, `summary`, and `url` |
+| `preserveEmptyObjects`   | boolean/string[] | Preserve selected empty objects instead of pruning  |
 
 Important behavior:
 - Filter stage is recursive and may run multiple passes to remove now-unused components.
@@ -71,30 +71,38 @@ Important behavior:
 
 ## Casing
 
-| Option (`casingSet`) | Effect |
-|---|---|
-| `operationId` | Casing for operation IDs |
-| `properties` | Casing for schema/path property keys and required names |
-| `parametersQuery` / `parametersHeader` / `parametersPath` / `parametersCookie` | Casing for inline parameter names by location |
-| `componentsSchemas` / `componentsExamples` / `componentsHeaders` / `componentsResponses` / `componentsRequestBodies` / `componentsSecuritySchemes` | Casing for component keys |
-| `componentsParametersQuery` / `componentsParametersHeader` / `componentsParametersPath` / `componentsParametersCookie` | Casing for `components.parameters` keys by parameter `in` |
+| Option (`casingSet`)                                                                                                                                                                                     | Effect                                                                 |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------|
+| `operationId`                                                                                                                                                                                            | Casing for operation IDs                                               |
+| `operationIdKeepChars`                                                                                                                                                                                   | Extra characters to preserve while casing `operationId`                |
+| `summary` / `description`                                                                                                                                                                                | Casing for operation summaries and descriptions                        |
+| `summaryKeepChars` / `descriptionKeepChars`                                                                                                                                                              | Extra characters to preserve while casing summaries and descriptions   |
+| `properties`                                                                                                                                                                                             | Casing for schema/path property keys and required names                |
+| `propertiesKeepChars`                                                                                                                                                                                    | Extra characters to preserve while casing properties                   |
+| `parametersQuery` / `parametersHeader` / `parametersPath` / `parametersCookie`                                                                                                                           | Casing for inline parameter names by location                          |
+| `parametersQueryKeepChars` / `parametersHeaderKeepChars` / `parametersPathKeepChars` / `parametersCookieKeepChars`                                                                                       | Extra characters to preserve while casing inline parameter names       |
+| `componentsSchemas` / `componentsExamples` / `componentsHeaders` / `componentsResponses` / `componentsRequestBodies` / `componentsSecuritySchemes`                                                       | Casing for component keys                                              |
+| `componentsSchemasKeepChars` / `componentsExamplesKeepChars` / `componentsHeadersKeepChars` / `componentsResponsesKeepChars` / `componentsRequestBodiesKeepChars` / `componentsSecuritySchemesKeepChars` | Extra characters to preserve while casing component keys               |
+| `componentsParametersQuery` / `componentsParametersHeader` / `componentsParametersPath` / `componentsParametersCookie`                                                                                   | Casing for `components.parameters` keys by parameter `in`              |
+| `componentsParametersQueryKeepChars` / `componentsParametersHeaderKeepChars` / `componentsParametersPathKeepChars` / `componentsParametersCookieKeepChars`                                               | Extra characters to preserve while casing `components.parameters` keys |
 
 Reference behavior:
 - Related `$ref` values are updated for renamed component keys.
+- Custom keep chars are merged with the built-in defaults (`$`, `@`).
 
 ## Generate
 
-| Key (`generateSet`) | Type | Default | Effect |
-|---|---|---|---|
-| `operationIdTemplate` | string | none | Template used to generate operationIds |
-| `overwriteExisting` | boolean | false | If true, regenerate even existing operationIds |
+| Key (`generateSet`)   | Type    | Default | Effect                                         |
+|-----------------------|---------|---------|------------------------------------------------|
+| `operationIdTemplate` | string  | none    | Template used to generate operationIds         |
+| `overwriteExisting`   | boolean | false   | If true, regenerate even existing operationIds |
 
 Template resolves against operation context using internal parse template utilities.
 
 ## Overlay
 
-| Option | Type | Effect |
-|---|---|---|
+| Option                | Type | Effect                                           |
+|-----------------------|------|--------------------------------------------------|
 | `--overlayFile`, `-l` | path | Load overlay actions and apply to input document |
 
 Notable behavior:
@@ -104,10 +112,10 @@ Notable behavior:
 
 ## Convert and rename
 
-| Option | Type | Effect |
-|---|---|---|
+| Option        | Type   | Effect                        |
+|---------------|--------|-------------------------------|
 | `--convertTo` | string | Convert OpenAPI to 3.1 or 3.2 |
-| `--rename` | string | Replace `info.title` |
+| `--rename`    | string | Replace `info.title`          |
 
 Convert stage details:
 - Converts nullable/exclusive limits/example/const forms as needed.
@@ -116,10 +124,10 @@ Convert stage details:
 
 ## Split and bundle
 
-| Option | Type | Default | Effect |
-|---|---|---|---|
-| `--split` | boolean | false | Write multi-file output structure |
-| `--no-bundle` | boolean | false | Disable local/remote `$ref` bundling during parse |
+| Option        | Type    | Default | Effect                                            |
+|---------------|---------|---------|---------------------------------------------------|
+| `--split`     | boolean | false   | Write multi-file output structure                 |
+| `--no-bundle` | boolean | false   | Disable local/remote `$ref` bundling during parse |
 
 Split behavior:
 - Requires `--output`.
diff --git a/test/casing.test.js b/test/casing.test.js
index d61ecae..9587c72 100644
--- a/test/casing.test.js
+++ b/test/casing.test.js
@@ -165,8 +165,17 @@ describe('openapi-format CLI casing tests', () => {
     it('casing should keep default @$ characters', async () => {
       expect(of.changeCase('@openapi-format$}}', 'snake_case')).toBe('@openapi_format$');
     });
-    it('casing should remove all custom characters', async () => {
+    it('casing should keep custom dot characters and defaults', async () => {
+      expect(of.changeCase('cursor.created_at', 'camelCase', ['.'])).toBe('cursor.createdAt');
+    });
+    it('casing should merge custom characters with built-in defaults', async () => {
+      expect(of.changeCase('@openapi-$format.v2', 'camelCase', ['.'])).toBe('@openapi$format.v2');
+    });
+    it('casing should allow callers to disable built-in defaults with an empty array', async () => {
       expect(of.changeCase('@openapi-$format}}', 'snake_case', [])).toBe('openapi_format');
     });
+    it('casing should keep default @$ characters when no custom keep chars are provided', async () => {
+      expect(of.changeCase('@openapi-$format}}', 'snake_case')).toBe('@openapi$format');
+    });
   });
 });
diff --git a/test/openapi-core.test.js b/test/openapi-core.test.js
index e842441..27f7bd5 100644
--- a/test/openapi-core.test.js
+++ b/test/openapi-core.test.js
@@ -123,6 +123,111 @@ describe('openapi-format core API', () => {
     expect(result.data.paths['/pets'].get.summary).toBe('list-pets');
     expect(result.data.paths['/pets'].get.description).toBe('returns-all-pets');
   });
+
+  it('openapiChangeCase should keep configured separator characters for parameter names', async () => {
+    const doc = {
+      openapi: '3.0.0',
+      info: {title: 'API', version: '1.0.0'},
+      paths: {
+        '/pets': {
+          get: {
+            parameters: [
+              {
+                name: 'cursor.created_at',
+                in: 'query',
+                schema: {type: 'string'}
+              }
+            ],
+            responses: {200: {description: 'ok'}}
+          }
+        }
+      }
+    };
+
+    const result = await openapiChangeCase(doc, {
+      casingSet: {
+        parametersQuery: 'camelCase',
+        parametersQueryKeepChars: ['.']
+      }
+    });
+
+    expect(result.data.paths['/pets'].get.parameters[0].name).toBe('cursor.createdAt');
+  });
+
+  it('openapiChangeCase should keep configured separator characters for component schema keys and refs', async () => {
+    const doc = {
+      openapi: '3.0.0',
+      info: {title: 'API', version: '1.0.0'},
+      paths: {
+        '/pets': {
+          get: {
+            responses: {
+              200: {
+                description: 'ok',
+                content: {'application/json': {schema: {$ref: '#/components/schemas/Pet.v1'}}}
+              }
+            }
+          }
+        }
+      },
+      components: {
+        schemas: {
+          'Pet.v1': {type: 'object'}
+        }
+      }
+    };
+
+    const result = await openapiChangeCase(doc, {
+      casingSet: {
+        componentsSchemas: 'camelCase',
+        componentsSchemasKeepChars: ['.']
+      }
+    });
+
+    expect(Object.keys(result.data.components.schemas)).toContain('pet.v1');
+    expect(result.data.paths['/pets'].get.responses[200].content['application/json'].schema.$ref).toBe(
+      '#/components/schemas/pet.v1'
+    );
+  });
+
+  it('openapiChangeCase should keep configured separator characters for component parameter keys and refs', async () => {
+    const doc = {
+      openapi: '3.0.0',
+      info: {title: 'API', version: '1.0.0'},
+      paths: {
+        '/pets': {
+          get: {
+            parameters: [
+              {
+                $ref: '#/components/parameters/Cursor.v1'
+              }
+            ],
+            responses: {200: {description: 'ok'}}
+          }
+        }
+      },
+      components: {
+        parameters: {
+          'Cursor.v1': {
+            name: 'cursor.v1',
+            in: 'query',
+            schema: {type: 'string'}
+          }
+        }
+      }
+    };
+
+    const result = await openapiChangeCase(doc, {
+      casingSet: {
+        componentsParametersQuery: 'camelCase',
+        componentsParametersQueryKeepChars: ['.']
+      }
+    });
+
+    expect(Object.keys(result.data.components.parameters)).toContain('cursor.v1');
+    expect(result.data.components.parameters['cursor.v1'].name).toBe('cursor.v1');
+    expect(result.data.paths['/pets'].get.parameters[0].$ref).toBe('#/components/parameters/cursor.v1');
+  });
 });
 
 describe('openapiSplit API', () => {
diff --git a/test/yaml-casing-parameters/customCasing.yaml b/test/yaml-casing-parameters/customCasing.yaml
index 4c86767..5a94116 100644
--- a/test/yaml-casing-parameters/customCasing.yaml
+++ b/test/yaml-casing-parameters/customCasing.yaml
@@ -1,3 +1,5 @@
-parametersQuery: snake_case
+parametersQuery: camelCase
+parametersQueryKeepChars:
+  - .
 parametersHeader: snake_case
 parametersPath: snake_case
diff --git a/test/yaml-casing-parameters/input.yaml b/test/yaml-casing-parameters/input.yaml
index 8fd9cc0..d5651ea 100644
--- a/test/yaml-casing-parameters/input.yaml
+++ b/test/yaml-casing-parameters/input.yaml
@@ -121,7 +121,7 @@ paths:
           schema:
             type: integer
             format: int64
-        - name: limitItems
+        - name: cursor.created_at
           in: query
           description: ID of pet to return
           required: true
diff --git a/test/yaml-casing-parameters/output.yaml b/test/yaml-casing-parameters/output.yaml
index 14a8e59..9b9e1e8 100644
--- a/test/yaml-casing-parameters/output.yaml
+++ b/test/yaml-casing-parameters/output.yaml
@@ -121,7 +121,7 @@ paths:
           schema:
             type: integer
             format: int64
-        - name: limit_items
+        - name: cursor.createdAt
           in: query
           description: ID of pet to return
           required: true
@@ -604,7 +604,7 @@ components:
       summary: A payload example for a notification
   parameters:
     skipParam:
-      name: skip_items
+      name: skipItems
       in: query
       description: number of items to skip
       required: true
@@ -612,7 +612,7 @@ components:
         type: integer
         format: int32
     limitParam:
-      name: $limit_param
+      name: $limitParam
       in: query
       description: max records to return
       required: true
diff --git a/types/openapi-format.d.ts b/types/openapi-format.d.ts
index 71ccc07..29ff985 100644
--- a/types/openapi-format.d.ts
+++ b/types/openapi-format.d.ts
@@ -69,19 +69,41 @@ declare module 'openapi-format' {
 
   export interface OpenAPICasingSet {
     operationId?: string;
+    operationIdKeepChars?: string[];
+    summary?: string;
+    summaryKeepChars?: string[];
+    description?: string;
+    descriptionKeepChars?: string[];
     properties?: string;
+    propertiesKeepChars?: string[];
     parametersQuery?: string;
+    parametersQueryKeepChars?: string[];
     parametersHeader?: string;
+    parametersHeaderKeepChars?: string[];
     parametersPath?: string;
+    parametersPathKeepChars?: string[];
+    parametersCookie?: string;
+    parametersCookieKeepChars?: string[];
     componentsExamples?: string;
+    componentsExamplesKeepChars?: string[];
     componentsSchemas?: string;
+    componentsSchemasKeepChars?: string[];
     componentsHeaders?: string;
+    componentsHeadersKeepChars?: string[];
     componentsResponses?: string;
+    componentsResponsesKeepChars?: string[];
     componentsRequestBodies?: string;
+    componentsRequestBodiesKeepChars?: string[];
     componentsSecuritySchemes?: string;
+    componentsSecuritySchemesKeepChars?: string[];
     componentsParametersQuery?: string;
+    componentsParametersQueryKeepChars?: string[];
     componentsParametersHeader?: string;
+    componentsParametersHeaderKeepChars?: string[];
     componentsParametersPath?: string;
+    componentsParametersPathKeepChars?: string[];
+    componentsParametersCookie?: string;
+    componentsParametersCookieKeepChars?: string[];
     [key: string]: unknown;
   }
 
@@ -199,7 +221,7 @@ declare module 'openapi-format' {
   export function detectFormat(input: string): Promise<'json' | 'yaml' | 'unknown'>;
   export function analyzeOpenApi(oaObj: OpenApiDocument): AnalyzeOpenApiResult;
 
-  export function changeCase(valueAsString: string, caseType: string): string;
+  export function changeCase(valueAsString: string, caseType: string, customKeepChars?: string[]): string;
   export function resolveJsonPath(obj: Record<string, unknown> | unknown[], path: string): JsonPathNode[];
   export function resolveJsonPathValue(obj: Record<string, unknown> | unknown[], path: string): unknown[];
 }
diff --git a/utils/casing.js b/utils/casing.js
index 69200b3..4d26287 100644
--- a/utils/casing.js
+++ b/utils/casing.js
@@ -46,14 +46,15 @@ function changeParametersCasingEnabled(casingSet) {
  * Change Object keys case function
  * @param {object} obj
  * @param {string} caseType
+ * @param {string[]} customKeepChars Custom characters to keep
  * @returns {*}
  */
-function changeObjKeysCase(obj, caseType) {
+function changeObjKeysCase(obj, caseType, customKeepChars = null) {
   if (!isObject(obj)) return obj;
 
   const orgObj = JSON.parse(JSON.stringify(obj)); // Deep copy of the object
   let replacedItems = Object.keys(orgObj).map(key => {
-    const newKey = changeCase(key, caseType);
+    const newKey = changeCase(key, caseType, customKeepChars);
     return {[newKey]: orgObj[key]};
   });
   return Object.assign({}, ...replacedItems);
@@ -63,18 +64,47 @@ function changeObjKeysCase(obj, caseType) {
  * Change object keys case in array function
  * @param {object} node
  * @param {string} caseType
+ * @param {string[]} customKeepChars Custom characters to keep
  * @returns {*}
  */
-function changeArrayObjKeysCase(node, caseType) {
+function changeArrayObjKeysCase(node, caseType, customKeepChars = null) {
   if (!isArray(node)) return node;
 
   const casedNode = JSON.parse(JSON.stringify(node)); // Deep copy of the schema object
   for (let i = 0; i < casedNode.length; i++) {
-    casedNode[i] = changeObjKeysCase(casedNode[i], caseType);
+    casedNode[i] = changeObjKeysCase(casedNode[i], caseType, customKeepChars);
   }
   return casedNode;
 }
 
+/**
+ * Build the keep character list for case-anything.
+ * Always preserves the built-in defaults and appends any custom characters.
+ * @param {string[]} customKeepChars Custom characters to keep
+ * @returns {string[]}
+ */
+function normalizeKeepChars(customKeepChars = null) {
+  if (customKeepChars == null) {
+    return ['$', '@'];
+  }
+
+  if (!isArray(customKeepChars)) {
+    return customKeepChars;
+  }
+
+  if (customKeepChars.length === 0) {
+    return [];
+  }
+
+  const keepChars = ['$', '@'];
+  customKeepChars.forEach(char => {
+    if (!keepChars.includes(char)) {
+      keepChars.push(char);
+    }
+  });
+  return keepChars;
+}
+
 /**
  * Change case function
  * @param {string} valueAsString The value to change
@@ -84,7 +114,7 @@ function changeArrayObjKeysCase(node, caseType) {
  */
 function changeCase(valueAsString, caseType, customKeepChars = null) {
   if (!isString(valueAsString) || valueAsString === '') return valueAsString;
-  const keepChars = customKeepChars || ['$', '@'];
+  const keepChars = normalizeKeepChars(customKeepChars);
   const cleanedString = valueAsString.replace(/\[(.*?)]/g, (match, p1) => {
     return ' ' + p1.replace(/([A-Z])/g, ' $1') + ' ';
   });