diff --git a/infra/cdk/README.md b/infra/cdk/README.md
index 93273f3..e32d030 100644
--- a/infra/cdk/README.md
+++ b/infra/cdk/README.md
@@ -42,13 +42,56 @@ The role grants only:
 - `elasticbeanstalk:UpdateEnvironment` on environment `shoc-backend-dev` only.
 - `s3:ListBucket` and `s3:GetBucketLocation` on
   `elasticbeanstalk-us-east-1-396287094661` (the official action's
-  ownership-safe bucket checks), plus `s3:CreateBucket` and
+  ownership-safe bucket checks), `s3:GetBucketPolicy` for the policy inspection
+  observed in attempt 11 of run `30448885838`, plus `s3:CreateBucket` and
   `s3:PutBucketOwnershipControls` on the same bucket-level ARN. Under the
   `shoc-backend/` object prefix only:
-  `s3:PutObject`, `s3:GetObject`, `s3:GetObjectAcl`, and
-  `s3:GetObjectVersion`, which the pinned official deployment action and
-  Elastic Beanstalk require to validate the `CreateApplicationVersion` source
-  bundle after upload.
+  `s3:PutObject`, `s3:GetObject`, and `s3:GetObjectVersion`, which the pinned
+  official deployment action requires to validate the
+  `CreateApplicationVersion` source bundle after upload.
+- `s3:PutObject`, `s3:GetObject`, `s3:GetObjectVersionAcl`,
+  `s3:PutObjectVersionAcl`, and `s3:DeleteObject` on only
+  `elasticbeanstalk-us-east-1-396287094661/resources/environments/e-hehnrqjjrt/_runtime/_versions/shoc-backend/*`.
+  Elastic Beanstalk copies each uploaded source bundle into this
+  environment-specific runtime prefix during `UpdateEnvironment`, verifies it
+  with `HeadObject` (authorized by `s3:GetObject`), and removes the temporary
+  copy after the version is registered. Attempts 1 through 4 of run
+  `30448885838` exposed the exact source, destination, cleanup, and verification
+  operations after the earlier ACL denial was resolved. CloudTrail recorded
+  the exact `s3:GetObject` denial on attempt 4; attempt 6 then exposed the
+  version-specific ACL read performed on the copied object; attempt 7 exposed
+  the matching version-ACL write. The grant does not cover another
+  environment, another application, source bundles, object content versions,
+  non-version ACL mutation, tags, or retention.
+- `s3:PutObject` on only the two embedded-extension prefixes
+  `elasticbeanstalk-us-east-1-396287094661/resources/_runtime/_embedded_extensions/shoc-backend/*`
+  and
+  `elasticbeanstalk-us-east-1-396287094661/resources/environments/e-hehnrqjjrt/_runtime/_embedded_extensions/shoc-backend/*`.
+  After the runtime bundle copy and version-ACL operations succeeded, attempt 8
+  of run `30448885838` showed Elastic Beanstalk materializing the application's
+  embedded-extension manifest at the application-specific shared prefix.
+  Attempt 9 then showed the matching write into the exact dev-environment
+  prefix. CloudTrail recorded both denied actions and object ARNs. The grant
+  does not include reads, deletes, ACL mutation, another application,
+  another environment, or another bucket.
+- `s3:GetObject` on only the environment-specific embedded-extension prefix
+  above. Attempt 10 showed that Elastic Beanstalk verifies the materialized
+  environment copy with `HeadObject`, which S3 authorizes through
+  `s3:GetObject`. The shared embedded-extension prefix remains write-only.
+- `s3:GetObject` and `s3:PutObject` on only
+  `elasticbeanstalk-us-east-1-396287094661/resources/environments/e-hehnrqjjrt/_runtime/versions/*`.
+  Attempt 12 showed Elastic Beanstalk reading the previous environment version
+  manifest and writing its replacement under this exact dev-environment
+  runtime prefix. The grant excludes deletes, ACL mutation, other environments,
+  and application bundle content.
+- `s3:GetObjectAcl` on objects under the service-wide
+  `arn:aws:s3:::elasticbeanstalk-*/*` namespace. AWS Support case
+  `178526484500047` confirmed that `UpdateEnvironment` uses the initiating
+  role to inspect objects in AWS-owned Elastic Beanstalk buckets, not only the
+  account-owned source-bundle bucket. The wildcard is limited to one read-only
+  ACL action and the Elastic Beanstalk bucket namespace; it grants no object
+  content read, write, delete, bucket-management, IAM, or `PassRole`
+  capability.
 
   `s3:CreateBucket` is part of the pinned
   `aws-actions/aws-elastic-beanstalk-deploy@cfad3e5e...` (v1.0.6) IAM
@@ -112,15 +155,11 @@ The role grants only:
   successful administrator deployment. AWS supports resource-level
   constraints for all three mutations, so replacement ASGs remain covered
   without granting access to another environment.
-- `s3:GetObjectAcl` under the existing
-  `elasticbeanstalk-us-east-1-396287094661/shoc-backend/*` object prefix.
-  Elastic Beanstalk emitted this read during the same attempt while validating
-  the uploaded application bundle. It grants no bucket-wide or cross-prefix
-  object access.
 It grants **no** IAM mutation or `PassRole`, **no** RDS / Secrets Manager
 access, no EC2 mutation, and **no** administrator policy. The only non-EB/S3
 mutations are the three deployment-process Auto Scaling calls, restricted to
-this environment's ASG name pattern. There are no wildcard mutation surfaces.
+this environment's ASG name pattern. There are no wildcard mutation surfaces;
+the only service-wide object grant is read-only ACL metadata.
 
 ## Prerequisites
 
@@ -160,13 +199,16 @@ All commands run from `infra/cdk/`.
 The workflow's `AWS_DEPLOY_ROLE_ARN` repository secret (environment `dev`) must
 hold the ARN output by this stack (`GithubDeployRoleArn`).
 
-The OIDC deployment is currently fail-closed, not repaired. Elastic Beanstalk
-still reports a generic `s3:GetObjectAcl` denial after the account-owned source
-prefix and every exact cross-account object referenced by the sanitized live
-stack were tested independently. The runtime-prefix, platform-assets, and
-launch-control hypotheses were disproved and are intentionally absent from the
-policy. Do not broaden `GetObjectAcl` without an exact principal/action/resource
-record from AWS Support or the AWS-owned bucket's diagnostic owner.
+The previous OIDC deployment remained fail-closed after Elastic Beanstalk
+reported a generic `s3:GetObjectAcl` denial outside the account-owned source
+prefix. AWS Support case `178526484500047` subsequently confirmed that
+`UpdateEnvironment` checks objects in AWS-owned Elastic Beanstalk buckets
+using the initiating role and requires the `elasticbeanstalk-*/*` resource
+namespace. This policy adds only the denied ACL-read action on that namespace;
+it intentionally does not copy the managed
+`AdministratorAccess-AWSElasticBeanstalk` policy's broad `s3:Get*`,
+`s3:Put*`, or `s3:Delete*` grants. Any later denial must be evaluated and
+granted independently.
 
 The pinned deployment action can return success after Elastic Beanstalk emits a
 fatal deployment event. The following workflow step therefore verifies that
diff --git a/infra/cdk/deploy-dev-stack.ts b/infra/cdk/deploy-dev-stack.ts
index 3575452..0cdef0c 100644
--- a/infra/cdk/deploy-dev-stack.ts
+++ b/infra/cdk/deploy-dev-stack.ts
@@ -18,6 +18,18 @@ export class DeployDevStack extends cdk.Stack {
     const applicationArn = `arn:aws:elasticbeanstalk:${REGION}:${ACCOUNT_ID}:application/${APPLICATION_NAME}`;
     const environmentArn = `arn:aws:elasticbeanstalk:${REGION}:${ACCOUNT_ID}:environment/${APPLICATION_NAME}/${ENVIRONMENT_NAME}`;
     const bucketArn = `arn:aws:s3:::${BUCKET_NAME}`;
+    const runtimeVersionArn =
+      `${bucketArn}/resources/environments/${ENVIRONMENT_ID}` +
+      `/_runtime/_versions/${APPLICATION_NAME}/*`;
+    const embeddedExtensionArn =
+      `${bucketArn}/resources/_runtime/_embedded_extensions/` +
+      `${APPLICATION_NAME}/*`;
+    const environmentEmbeddedExtensionArn =
+      `${bucketArn}/resources/environments/${ENVIRONMENT_ID}` +
+      `/_runtime/_embedded_extensions/${APPLICATION_NAME}/*`;
+    const runtimeManifestArn =
+      `${bucketArn}/resources/environments/${ENVIRONMENT_ID}` +
+      '/_runtime/versions/*';
     const oidcProviderArn = `arn:aws:iam::${ACCOUNT_ID}:oidc-provider/token.actions.githubusercontent.com`;
 
     const deployRole = new iam.Role(this, 'GithubDeployRole', {
@@ -134,6 +146,7 @@ export class DeployDevStack extends cdk.Stack {
           's3:CreateBucket',
           's3:PutBucketOwnershipControls',
           's3:GetBucketLocation',
+          's3:GetBucketPolicy',
         ],
         resources: [bucketArn],
       }),
@@ -142,11 +155,68 @@ export class DeployDevStack extends cdk.Stack {
     deployRole.addToPolicy(
       new iam.PolicyStatement({
         effect: iam.Effect.ALLOW,
-        actions: ['s3:GetObject', 's3:GetObjectAcl', 's3:GetObjectVersion', 's3:PutObject'],
+        actions: ['s3:GetObject', 's3:GetObjectVersion', 's3:PutObject'],
         resources: [`${bucketArn}/${APPLICATION_NAME}/*`],
       }),
     );
 
+    deployRole.addToPolicy(
+      new iam.PolicyStatement({
+        effect: iam.Effect.ALLOW,
+        actions: [
+          's3:DeleteObject',
+          's3:GetObject',
+          's3:GetObjectVersionAcl',
+          's3:PutObject',
+          's3:PutObjectVersionAcl',
+        ],
+        // UpdateEnvironment copies the uploaded source bundle into this
+        // environment-specific runtime prefix, verifies the temporary copy,
+        // preserves its version ACL, and removes it after registration.
+        resources: [runtimeVersionArn],
+      }),
+    );
+
+    deployRole.addToPolicy(
+      new iam.PolicyStatement({
+        effect: iam.Effect.ALLOW,
+        actions: ['s3:PutObject'],
+        // UpdateEnvironment materializes the application's embedded-extension
+        // manifest under the shared and environment-specific runtime prefixes.
+        resources: [embeddedExtensionArn, environmentEmbeddedExtensionArn],
+      }),
+    );
+
+    deployRole.addToPolicy(
+      new iam.PolicyStatement({
+        effect: iam.Effect.ALLOW,
+        actions: ['s3:GetObject'],
+        // Elastic Beanstalk verifies the environment copy with HeadObject.
+        resources: [environmentEmbeddedExtensionArn],
+      }),
+    );
+
+    deployRole.addToPolicy(
+      new iam.PolicyStatement({
+        effect: iam.Effect.ALLOW,
+        actions: ['s3:GetObject', 's3:PutObject'],
+        // UpdateEnvironment reads the prior environment version manifest and
+        // writes its replacement under this environment-only runtime prefix.
+        resources: [runtimeManifestArn],
+      }),
+    );
+
+    deployRole.addToPolicy(
+      new iam.PolicyStatement({
+        effect: iam.Effect.ALLOW,
+        actions: ['s3:GetObjectAcl'],
+        // UpdateEnvironment also checks objects in AWS-owned Elastic Beanstalk
+        // buckets. AWS Support case 178526484500047 confirmed that the caller's
+        // identity policy must cover the service-wide bucket namespace.
+        resources: ['arn:aws:s3:::elasticbeanstalk-*/*'],
+      }),
+    );
+
     new cdk.CfnOutput(this, 'GithubDeployRoleArn', {
       value: deployRole.roleArn,
       description: 'ARN of the GitHub OIDC deploy role for shoc-backend dev.',