diff --git a/eslint.config.mjs b/eslint.config.mjs
index 726de46d3c..12eee0bc1a 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -36,7 +36,7 @@ export default [
     },
   },
   {
-    ignores: ['node-modules'],
+    ignores: ['node_modules'],
   },
   {
     files: ['**/*.test.js'],
diff --git a/package.json b/package.json
index 8808e59d11..3f221d00f3 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
     "scripts": {
         "format": "npx prettier . --write",
         "format-check": "npx prettier . --check",
-        "lint-js": "npx eslint **/*.js",
+        "lint-js": "npx eslint .",
         "gen-ipa-docs": "node tools/spectral/ipa/scripts/generateRulesetReadme.js",
         "ipa-validation": "spectral lint  ./openapi/.raw/v2.yaml --ruleset=./tools/spectral/ipa/ipa-spectral.yaml",
         "ipa-filter-violations": "node tools/spectral/ipa/scripts/filter-ipa-violations.js",
diff --git a/tools/spectral/.spectral.yaml b/tools/spectral/.spectral.yaml
index 8e5a012fb9..28bf2b216f 100644
--- a/tools/spectral/.spectral.yaml
+++ b/tools/spectral/.spectral.yaml
@@ -15,7 +15,18 @@ aliases:
     - "#OperationObject.parameters[?(@ && @.in)]"
     - "$.components.schemas[*]..properties[?(@ && @.type)]"
 
+functions:
+  - acceptHeaderUpcomingVersionLimit
+
 rules:
+  accept-header-upcoming-version-limit:
+    description: Ensure that each operation has at most one upcoming API Accept header.
+    message: "An operation must not have more than one upcoming API Accept header (format: application/vnd.atlas.YYYY-MM-DD.upcoming+format)."
+    severity: error
+    given: $.paths[*][*]
+    then:
+      function: "acceptHeaderUpcomingVersionLimit"
+      
   xgen-schema-name-pascal-case:
     description: OpenAPI Schema names should use PascalCase. PascalCase ensures consistency with OpenAPI generated code.
     message: "`{{property}}` name must follow PascalCase. Please verify if you have provided valid @Schema(name='') annotation"
diff --git a/tools/spectral/.tool-versions b/tools/spectral/.tool-versions
new file mode 100644
index 0000000000..119cdc35fc
--- /dev/null
+++ b/tools/spectral/.tool-versions
@@ -0,0 +1 @@
+nodejs 24.0.2
diff --git a/tools/spectral/__tests__/acceptHeaderUpcomingVersionLimit.test.js b/tools/spectral/__tests__/acceptHeaderUpcomingVersionLimit.test.js
new file mode 100644
index 0000000000..2271a6cc94
--- /dev/null
+++ b/tools/spectral/__tests__/acceptHeaderUpcomingVersionLimit.test.js
@@ -0,0 +1,99 @@
+import { DiagnosticSeverity } from '@stoplight/types';
+import acceptHeaderUpcomingVersionLimit from '../functions/acceptHeaderUpcomingVersionLimit';
+
+describe('accept-header-upcoming-version-limit', () => {
+  it('valid: no upcoming Accept headers', () => {
+    const operation = {
+      operationId: 'getTest',
+      responses: {
+        200: {
+          content: {
+            'application/json': {},
+          },
+        },
+      },
+      requestBody: {
+        content: {
+          'application/json': {},
+        },
+      },
+    };
+
+    const result = acceptHeaderUpcomingVersionLimit(operation);
+    expect(result).toBeUndefined();
+  });
+
+  it('valid: one upcoming Accept header in response', () => {
+    const operation = {
+      operationId: 'getTest',
+      responses: {
+        200: {
+          content: {
+            'application/vnd.atlas.2024-06-01.upcoming+json': {},
+            'application/json': {},
+          },
+        },
+      },
+    };
+
+    const result = acceptHeaderUpcomingVersionLimit(operation);
+    expect(result).toBeUndefined();
+  });
+
+  it('invalid: two upcoming Accept headers in response', () => {
+    const operation = {
+      operationId: 'getTest',
+      responses: {
+        200: {
+          content: {
+            'application/vnd.atlas.2024-06-01.upcoming+json': {},
+            'application/vnd.atlas.2024-07-01.upcoming+json': {},
+            'application/json': {},
+          },
+        },
+      },
+    };
+
+    const result = acceptHeaderUpcomingVersionLimit(operation);
+    expect(result).toEqual([
+      {
+        message: expect.stringMatching(/Found 2 upcoming API Accept headers/),
+      },
+    ]);
+  });
+
+  it('invalid: two upcoming Accept headers in request', () => {
+    const operation = {
+      operationId: 'postTest',
+      requestBody: {
+        content: {
+          'application/vnd.atlas.2024-06-01.upcoming+json': {},
+          'application/vnd.atlas.2024-07-01.upcoming+json': {},
+          'application/json': {},
+        },
+      },
+    };
+
+    const result = acceptHeaderUpcomingVersionLimit(operation);
+    expect(result).toEqual([
+      {
+        message: expect.stringMatching(/Found 2 upcoming API Accept headers/),
+      },
+    ]);
+  });
+
+  it('invalid: missing operationId', () => {
+    const operation = {
+      responses: {
+        200: {
+          content: {
+            'application/vnd.atlas.2024-06-01.upcoming+json': {},
+          },
+        },
+      },
+    };
+
+    const result = acceptHeaderUpcomingVersionLimit(operation);
+    expect(result).toBeUndefined();
+  });
+});
diff --git a/tools/spectral/functions/acceptHeaderUpcomingVersionLimit.js b/tools/spectral/functions/acceptHeaderUpcomingVersionLimit.js
new file mode 100644
index 0000000000..ffe59b0699
--- /dev/null
+++ b/tools/spectral/functions/acceptHeaderUpcomingVersionLimit.js
@@ -0,0 +1,41 @@
+module.exports = function (input) {
+  // Get operationId from context, if this fails return an error
+  const operationId = input.operationId;
+  if (!operationId) {
+    return;
+  }
+
+  // List of errors
+  const errors = [];
+
+  // Validate versions in 200 responses
+  const responseErr = validateContent(operationId, 'response', input?.responses?.[200]?.content);
+  if (responseErr != null) errors.push(responseErr);
+
+  // Validate versions in requests
+  const requestErr = validateContent(operationId, 'request', input?.requestBody?.content);
+  if (requestErr != null) errors.push(requestErr);
+
+  return errors.length > 0 ? errors : undefined;
+};
+
+// Check for upcoming API Accept headers
+const upcomingRegex = /^application\/vnd\.atlas\.\d{4}-\d{2}-\d{2}\.upcoming\+.+$/;
+
+function validateContent(operationId, section, content) {
+  if (content == null) {
+    return null;
+  }
+
+  const contentTypes = Object.keys(content);
+  const upcomingContentTypes = contentTypes.filter((k) => upcomingRegex.test(k));
+  // If there's less than or equal to one upcoming header then the operation is valid
+  if (upcomingContentTypes.length <= 1) {
+    return null;
+  }
+
+  // Return an error message
+  return {
+    message: `OperationId: ${operationId} - Found ${upcomingContentTypes.length} upcoming API Accept headers (section: ${section}): ${upcomingContentTypes.join(', ')}`,
+  };
+}