diff --git a/packages/@aws-cdk/cfnspec/build-tools/build.ts b/packages/@aws-cdk/cfnspec/build-tools/build.ts
index 5409134256ffb..094f2f5f13c1d 100644
--- a/packages/@aws-cdk/cfnspec/build-tools/build.ts
+++ b/packages/@aws-cdk/cfnspec/build-tools/build.ts
@@ -19,7 +19,7 @@ async function main() {
 
   // If this is a PR build check the spec for evolution (this is set in buildspec-pr.yaml)
   const outputFile = path.join(outDir, 'specification.json');
-  if (process.env.PR_BUILD) {
+  if (process.env.CODEBUILD_WEBHOOK_TRIGGER?.startsWith('pr/')) {
     await validateSpecificationEvolution(async () => {
       await generateResourceSpecification(inputDir, outputFile);
       return fs.readJson(outputFile);
diff --git a/packages/@aws-cdk/cfnspec/build-tools/massage-spec.ts b/packages/@aws-cdk/cfnspec/build-tools/massage-spec.ts
index fc7aee9466e2e..9be37cef28b80 100644
--- a/packages/@aws-cdk/cfnspec/build-tools/massage-spec.ts
+++ b/packages/@aws-cdk/cfnspec/build-tools/massage-spec.ts
@@ -17,6 +17,13 @@ export function massageSpec(spec: schema.Specification) {
  */
 function replaceIncompleteTypes(spec: schema.Specification) {
   for (const [name, definition] of Object.entries(spec.PropertyTypes)) {
+    if (!definition) {
+      // eslint-disable-next-line no-console
+      console.log(`[${name}] **ERROR** Nullish type definition: a patch probably copied a nonexistent value!`);
+      process.exitCode = 1;
+      continue;
+    }
+
     if (!schema.isRecordType(definition)
     && !schema.isCollectionProperty(definition)
     && !schema.isScalarProperty(definition)
diff --git a/packages/@aws-cdk/cfnspec/build-tools/validate-evolution.ts b/packages/@aws-cdk/cfnspec/build-tools/validate-evolution.ts
index 40296e225bd55..dd0cb2f21c8db 100644
--- a/packages/@aws-cdk/cfnspec/build-tools/validate-evolution.ts
+++ b/packages/@aws-cdk/cfnspec/build-tools/validate-evolution.ts
@@ -1,5 +1,8 @@
 /* eslint-disable no-console */
 import * as child_process from 'child_process';
+import * as fs from 'fs-extra';
+
+const SKIP_FILE = 'skip-evolution-check.txt';
 
 /**
  * Run validations on the spec evolution, on the pull request.
@@ -10,11 +13,24 @@ import * as child_process from 'child_process';
  * Expects and uses git.
  */
 export async function validateSpecificationEvolution(specProducer: () => Promise<any>) {
+  const prNumber = (process.env.CODEBUILD_WEBHOOK_TRIGGER ?? '').replace(/^pr\//, '');
+  const skips = (await fs.readFile(SKIP_FILE, { encoding: 'utf-8' })).split('\n');
+  if (prNumber && skips.includes(prNumber)) {
+    console.log(`Skipping evo check of PR ${prNumber} (${SKIP_FILE})`);
+    await specProducer();
+    return;
+  }
+
   const targetBranch = process.env.CODEBUILD_WEBHOOK_BASE_REF ?? 'main';
   console.log(`Comparing differences with ${targetBranch}`);
   const mergeBase = child_process.execSync(`git merge-base ${targetBranch} HEAD`).toString().trim();
   console.log(`Base commit ${mergeBase}`);
-  const currentCommit = child_process.execSync('git rev-parse --abbrev-ref HEAD').toString().trim();
+  // Find branch name if we have one
+  let currentCommit = child_process.execSync('git rev-parse --abbrev-ref HEAD').toString().trim();
+  if (currentCommit === 'HEAD') {
+    // No branch, just spec use commit
+    currentCommit = child_process.execSync('git rev-parse HEAD').toString().trim();
+  }
   console.log(`Current commit ${currentCommit}`);
 
   const specs = new Array<any>();
diff --git a/packages/@aws-cdk/cfnspec/skip-evolution-check.txt b/packages/@aws-cdk/cfnspec/skip-evolution-check.txt
new file mode 100644
index 0000000000000..725fe7f1f113e
--- /dev/null
+++ b/packages/@aws-cdk/cfnspec/skip-evolution-check.txt
@@ -0,0 +1,2 @@
+# to fully skip spec evolution checks, put the PR number in this file.
+25326
\ No newline at end of file
diff --git a/packages/@aws-cdk/cfnspec/spec-source/specification/000_cfn/911_Batch_JobDefinition_patch.json b/packages/@aws-cdk/cfnspec/spec-source/specification/000_cfn/911_Batch_JobDefinition_patch.json
deleted file mode 100644
index 90416d9a6c2e0..0000000000000
--- a/packages/@aws-cdk/cfnspec/spec-source/specification/000_cfn/911_Batch_JobDefinition_patch.json
+++ /dev/null
@@ -1,49 +0,0 @@
-{
-  "PropertyTypes": {
-    "patch": {
-      "description": "Undoing upstream property type renames of Batch.",
-      "operations": [
-        {
-          "op": "move",
-          "from": "/AWS::Batch::JobDefinition.EksEmptyDir",
-          "path": "/AWS::Batch::JobDefinition.EmptyDir"
-        },
-        {
-          "op": "replace",
-          "path": "/AWS::Batch::JobDefinition.EksVolume/Properties/EmptyDir/Type",
-          "value": "EmptyDir"
-        },
-        {
-          "op": "move",
-          "from": "/AWS::Batch::JobDefinition.EksHostPath",
-          "path": "/AWS::Batch::JobDefinition.HostPath"
-        },
-        {
-          "op": "replace",
-          "path": "/AWS::Batch::JobDefinition.EksVolume/Properties/HostPath/Type",
-          "value": "HostPath"
-        },
-        {
-          "op": "move",
-          "from": "/AWS::Batch::JobDefinition.EksContainerResourceRequirements",
-          "path": "/AWS::Batch::JobDefinition.Resources"
-        },
-        {
-          "op": "replace",
-          "path": "/AWS::Batch::JobDefinition.EksContainer/Properties/Resources/Type",
-          "value": "Resources"
-        },
-        {
-          "op": "move",
-          "from": "/AWS::Batch::JobDefinition.EksContainerSecurityContext",
-          "path": "/AWS::Batch::JobDefinition.SecurityContext"
-        },
-        {
-          "op": "replace",
-          "path": "/AWS::Batch::JobDefinition.EksContainer/Properties/SecurityContext/Type",
-          "value": "SecurityContext"
-        }
-      ]
-    }
-  }
-}