diff --git a/apps/sim/app/api/tools/sap_concur/shared.ts b/apps/sim/app/api/tools/sap_concur/shared.ts
index 8c7adf82665..28800c6256d 100644
--- a/apps/sim/app/api/tools/sap_concur/shared.ts
+++ b/apps/sim/app/api/tools/sap_concur/shared.ts
@@ -1,10 +1,11 @@
-import { createHash } from 'node:crypto'
+import { createHmac } from 'node:crypto'
 import { createLogger } from '@sim/logger'
 import { isPrivateIpHost } from '@sim/security/ssrf'
 import { getErrorMessage } from '@sim/utils/errors'
 import { truncate } from '@sim/utils/string'
 import { z } from 'zod'
 import { coalesceLocally } from '@/lib/concurrency/singleflight'
+import { env } from '@/lib/core/config/env'
 import {
   MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithValidation,
@@ -226,11 +227,17 @@ function readCachedToken(key: string): SapConcurToken | undefined {
  *
  * The whole tuple is JSON-encoded before hashing rather than concatenated with a
  * separator, so a free-form field (clientId, companyUuid) cannot span a field boundary
- * and collide with a different tuple. The full sha256 digest is kept — truncating it
- * would lower the collision/forgery bar for no measurable gain.
+ * and collide with a different tuple.
+ *
+ * Keyed with a server-side secret rather than a bare digest. The inputs include a
+ * user-chosen password, which is low-entropy enough to brute-force from a plain SHA-256
+ * if a key ever reached a heap dump or a debug log; an HMAC makes the key useless without
+ * the secret. A password-hashing KDF would be the wrong tool — this runs on every token
+ * fetch and the goal is collision-free partitioning, not verification of a stored
+ * credential.
  */
 function tokenCacheKey(req: SapConcurAuth): string {
-  return createHash('sha256')
+  return createHmac('sha256', env.INTERNAL_API_SECRET)
     .update(
       JSON.stringify([
         req.datacenter,
diff --git a/apps/sim/blocks/blocks/sap_concur.ts b/apps/sim/blocks/blocks/sap_concur.ts
index 0641b80d334..46809164f5c 100644
--- a/apps/sim/blocks/blocks/sap_concur.ts
+++ b/apps/sim/blocks/blocks/sap_concur.ts
@@ -1007,6 +1007,18 @@ Return ONLY the YYYY-MM-DD date - no explanations, no extra text.`,
       condition: { field: 'operation', value: 'sap_concur_create_report_comment' },
       required: { field: 'operation', value: 'sap_concur_create_report_comment' },
     },
+    {
+      id: 'sendbackComment',
+      title: 'Sendback Comment',
+      type: 'long-input',
+      placeholder: 'Visible wherever Request comments are shown',
+      condition: {
+        field: 'operation',
+        value: 'sap_concur_move_travel_request',
+        and: { field: 'action', value: 'sendback' },
+      },
+      mode: 'advanced',
+    },
     {
       id: 'includeAllComments',
       title: 'Include All Comments',
@@ -1893,7 +1905,7 @@ Return ONLY the comma-separated travel config IDs - no explanations, no extra te
         enabled: true,
         prompt: `Generate the JSON request body for the selected SAP Concur operation from the user's request.
 
-Match the payload to the resource being written. Every family below is camelCase.
+Match the payload to the resource being written. Every family below is camelCase EXCEPT exchange rates, which is snake_case.
 
 Expense reports (v4): name, businessPurpose, comment, policyId, countryCode, countrySubDivisionCode, reportDate, startDate, endDate, and reportSource — reportSource is REQUIRED when updating a report and must be one of EA, MOB, OTHER, SE, TR, UI.
 
@@ -1905,6 +1917,8 @@ SCIM users (Identity v4.1): create and update payloads use schemas, userName, na
 
 List items: listId, level, value, shortCode. Cash advances: amountRequested as { currency, amount }, name and userId (all required), plus optional accountCode, comment and purpose.
 
+Exchange rates are the one snake_case family: currency_sets as an array of up to 100 entries, each { from_crn_code, to_crn_code, start_date as YYYY-MM-DD, rate }.
+
 Omit fields the user did not describe rather than inventing identifiers.
 
 Return ONLY the JSON object - no explanations, no extra text.`,
@@ -2262,6 +2276,8 @@ Return ONLY the JSON object - no explanations, no extra text.`,
               body: params.body || undefined,
               userId: params.travelRequestUserId || undefined,
               companyID: params.companyID || undefined,
+              comment:
+                params.action === 'sendback' ? params.sendbackComment || undefined : undefined,
             }
           case 'sap_concur_list_travel_request_comments':
             return { ...auth, requestUuid: params.requestUuid }
@@ -2532,6 +2548,11 @@ Return ONLY the JSON object - no explanations, no extra text.`,
       description:
         'Optional company identifier for a travel request workflow action (documented as companyID, distinct from companyUuid)',
     },
+    sendbackComment: {
+      type: 'string',
+      description:
+        'Optional comment on a travel request workflow action — Concur applies it only to the sendback action, and it is visible wherever Request comments are shown',
+    },
     travelRequestApprovedBefore: { type: 'string', description: 'Travel requests approved before' },
     travelRequestApprovedAfter: { type: 'string', description: 'Travel requests approved after' },
     travelRequestModifiedBefore: { type: 'string', description: 'Travel requests modified before' },