diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index 945fbaf..c84411f 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "0.25.0"
+  ".": "0.26.0"
 }
diff --git a/.stats.yml b/.stats.yml
index 24fec55..794dabc 100644
--- a/.stats.yml
+++ b/.stats.yml
@@ -1,4 +1,4 @@
 configured_endpoints: 12
-openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/sequenzy/sequenzy-f997c1c36f6343f2751d98c206162e8685c98765b384edd5277543ddb24e52a3.yml
-openapi_spec_hash: 40ced574fa5887f40c827ea53267ffca
+openapi_spec_url: https://storage.googleapis.com/stainless-sdk-openapi-specs/sequenzy/sequenzy-c6fd81590d42e585def0ace329e14712c04163516175ce4a4abcb02a855e3c95.yml
+openapi_spec_hash: a802ba0889a22ce20cf282b1ba168c54
 config_hash: 51c1d1194ac58d8c8e3162839c8f84dd
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f0d089..6e36337 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.26.0 (2026-06-26)
+
+Full Changelog: [v0.25.0...v0.26.0](https://github.com/Sequenzy/sequenzy-typescript/compare/v0.25.0...v0.26.0)
+
+### Features
+
+* **api:** api update ([7a3d52e](https://github.com/Sequenzy/sequenzy-typescript/commit/7a3d52e03f858d9fd517a2dcbcde8d8983049614))
+
 ## 0.25.0 (2026-06-25)
 
 Full Changelog: [v0.24.0...v0.25.0](https://github.com/Sequenzy/sequenzy-typescript/compare/v0.24.0...v0.25.0)
diff --git a/package.json b/package.json
index 2e21dc4..599ca38 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sequenzy",
-  "version": "0.25.0",
+  "version": "0.26.0",
   "description": "The official TypeScript library for the Sequenzy API",
   "author": "Sequenzy <nic@sequenzy.com>",
   "types": "dist/index.d.ts",
diff --git a/src/resources/transactional.ts b/src/resources/transactional.ts
index 88e5330..663ba6e 100644
--- a/src/resources/transactional.ts
+++ b/src/resources/transactional.ts
@@ -51,9 +51,11 @@ export class Transactional extends APIResource {
    * profile exists, replies are captured in Sequenzy but are not forwarded
    * externally. Variables can be passed to customize the email content. Nested
    * objects and arrays are supported for repeat blocks, such as `items`. Returns
-   * immediately with a job ID. If a queued send references a required variable that
-   * is not provided and has no default, the worker records the send as failed during
-   * background rendering.
+   * immediately with a job ID. If Sequenzy detects likely missing or unused
+   * variables before queueing, the successful response includes a non-blocking
+   * `diagnostics` warning object. Missing values do not block queueing; if a queued
+   * send references a required variable that is not provided and has no default, the
+   * worker may record the send as failed during background rendering.
    *
    * @example
    * ```ts
@@ -97,6 +99,12 @@ export type TransactionalSendResponse =
 
 export namespace TransactionalSendResponse {
   export interface SlugBasedResponse {
+    /**
+     * Non-blocking warnings about likely template variable issues. The send is still
+     * queued when this object is present.
+     */
+    diagnostics?: SlugBasedResponse.Diagnostics;
+
     jobId?: string;
 
     success?: boolean;
@@ -107,6 +115,54 @@ export namespace TransactionalSendResponse {
   }
 
   export namespace SlugBasedResponse {
+    /**
+     * Non-blocking warnings about likely template variable issues. The send is still
+     * queued when this object is present.
+     */
+    export interface Diagnostics {
+      message: string;
+
+      missingRequiredVariables: Array<Diagnostics.MissingRequiredVariable>;
+
+      status: 'warning';
+
+      unusedVariables: Array<Diagnostics.UnusedVariable>;
+    }
+
+    export namespace Diagnostics {
+      export interface MissingRequiredVariable {
+        lookupName?: string;
+
+        message?: string;
+
+        name?: string;
+
+        suggestions?: Array<string>;
+
+        usedIn?: Array<MissingRequiredVariable.UsedIn>;
+      }
+
+      export namespace MissingRequiredVariable {
+        export interface UsedIn {
+          blockId?: string;
+
+          blockType?: string;
+
+          field?: string;
+
+          surface?: 'subject' | 'previewText' | 'body' | 'block';
+        }
+      }
+
+      export interface UnusedVariable {
+        message?: string;
+
+        name?: string;
+
+        suggestions?: Array<string>;
+      }
+    }
+
     export interface Transactional {
       id?: string;
 
@@ -117,12 +173,68 @@ export namespace TransactionalSendResponse {
   }
 
   export interface DirectContentResponse {
+    /**
+     * Non-blocking warnings about likely template variable issues. The send is still
+     * queued when this object is present.
+     */
+    diagnostics?: DirectContentResponse.Diagnostics;
+
     jobId?: string;
 
     success?: boolean;
 
     to?: string | Array<string>;
   }
+
+  export namespace DirectContentResponse {
+    /**
+     * Non-blocking warnings about likely template variable issues. The send is still
+     * queued when this object is present.
+     */
+    export interface Diagnostics {
+      message: string;
+
+      missingRequiredVariables: Array<Diagnostics.MissingRequiredVariable>;
+
+      status: 'warning';
+
+      unusedVariables: Array<Diagnostics.UnusedVariable>;
+    }
+
+    export namespace Diagnostics {
+      export interface MissingRequiredVariable {
+        lookupName?: string;
+
+        message?: string;
+
+        name?: string;
+
+        suggestions?: Array<string>;
+
+        usedIn?: Array<MissingRequiredVariable.UsedIn>;
+      }
+
+      export namespace MissingRequiredVariable {
+        export interface UsedIn {
+          blockId?: string;
+
+          blockType?: string;
+
+          field?: string;
+
+          surface?: 'subject' | 'previewText' | 'body' | 'block';
+        }
+      }
+
+      export interface UnusedVariable {
+        message?: string;
+
+        name?: string;
+
+        suggestions?: Array<string>;
+      }
+    }
+  }
 }
 
 export interface TransactionalSendParams {
@@ -207,8 +319,9 @@ export interface TransactionalSendParams {
    * scalars, nested objects, or arrays used by repeat blocks. Raw HTML templates can
    * use simple subscriber/custom-attribute conditionals such as
    * `{{#if subscriber.plan}}...{{else}}...{{/if}}` and
-   * `{{#unless subscriber.plan}}...{{/unless}}`. Missing required variables are
-   * recorded as failed sends during background rendering after the request is
+   * `{{#unless subscriber.plan}}...{{/unless}}`. Likely variable issues are returned
+   * as non-blocking diagnostics when possible; missing required variables may still
+   * be recorded as failed sends during background rendering after the request is
    * accepted.
    */
   variables?: { [key: string]: unknown };
diff --git a/src/version.ts b/src/version.ts
index 4931d4f..aa25151 100644
--- a/src/version.ts
+++ b/src/version.ts
@@ -1 +1 @@
-export const VERSION = '0.25.0'; // x-release-please-version
+export const VERSION = '0.26.0'; // x-release-please-version