diff --git a/apps/sim/app/api/tools/clickhouse/utils.test.ts b/apps/sim/app/api/tools/clickhouse/utils.test.ts
index ceac1af9241..23e45da05c5 100644
--- a/apps/sim/app/api/tools/clickhouse/utils.test.ts
+++ b/apps/sim/app/api/tools/clickhouse/utils.test.ts
@@ -12,6 +12,7 @@ const { mockValidateDatabaseHost, mockSecureFetchWithPinnedIP, mockValidateSqlWh
   }))
 
 vi.mock('@/lib/core/security/input-validation.server', () => ({
+  MAX_JSON_API_RESPONSE_BYTES: 10 * 1024 * 1024,
   validateDatabaseHost: mockValidateDatabaseHost,
   secureFetchWithPinnedIP: mockSecureFetchWithPinnedIP,
   validateSqlWhereClause: mockValidateSqlWhereClause,
diff --git a/apps/sim/app/api/tools/clickhouse/utils.ts b/apps/sim/app/api/tools/clickhouse/utils.ts
index e0687791a79..5b613285449 100644
--- a/apps/sim/app/api/tools/clickhouse/utils.ts
+++ b/apps/sim/app/api/tools/clickhouse/utils.ts
@@ -1,4 +1,5 @@
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateDatabaseHost,
   validateSqlWhereClause,
@@ -96,6 +97,7 @@ async function clickhouseRequest(
     body: statement,
     timeout: REQUEST_TIMEOUT_MS,
     allowHttp: !config.secure,
+    maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
   })
 
   const text = await response.text()
diff --git a/apps/sim/app/api/tools/grafana/update_alert_rule/route.ts b/apps/sim/app/api/tools/grafana/update_alert_rule/route.ts
index 095e8660c33..3d759919d42 100644
--- a/apps/sim/app/api/tools/grafana/update_alert_rule/route.ts
+++ b/apps/sim/app/api/tools/grafana/update_alert_rule/route.ts
@@ -5,6 +5,7 @@ import { grafanaUpdateAlertRuleContract } from '@/lib/api/contracts/tools/grafan
 import { getValidationErrorMessage, parseRequest } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateUrlWithDNS,
 } from '@/lib/core/security/input-validation.server'
@@ -76,6 +77,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
     const getResponse = await secureFetchWithPinnedIP(getUrl, getValidation.resolvedIP, {
       method: 'GET',
       headers: getHeaders,
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!getResponse.ok) {
@@ -205,6 +207,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       method: 'PUT',
       headers,
       body: JSON.stringify(updatedRule),
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!updateResponse.ok) {
diff --git a/apps/sim/app/api/tools/grafana/update_dashboard/route.ts b/apps/sim/app/api/tools/grafana/update_dashboard/route.ts
index 0f3d96b4464..bb005bcf3f6 100644
--- a/apps/sim/app/api/tools/grafana/update_dashboard/route.ts
+++ b/apps/sim/app/api/tools/grafana/update_dashboard/route.ts
@@ -5,6 +5,7 @@ import { grafanaUpdateDashboardContract } from '@/lib/api/contracts/tools/grafan
 import { getValidationErrorMessage, parseRequest } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateUrlWithDNS,
 } from '@/lib/core/security/input-validation.server'
@@ -75,6 +76,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
     const getResponse = await secureFetchWithPinnedIP(getUrl, getValidation.resolvedIP, {
       method: 'GET',
       headers: getHeaders,
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!getResponse.ok) {
@@ -166,6 +168,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       method: 'POST',
       headers,
       body: JSON.stringify(body),
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!updateResponse.ok) {
diff --git a/apps/sim/app/api/tools/grafana/update_folder/route.ts b/apps/sim/app/api/tools/grafana/update_folder/route.ts
index 3e551e192aa..87e09b6c7a6 100644
--- a/apps/sim/app/api/tools/grafana/update_folder/route.ts
+++ b/apps/sim/app/api/tools/grafana/update_folder/route.ts
@@ -5,6 +5,7 @@ import { grafanaUpdateFolderContract } from '@/lib/api/contracts/tools/grafana'
 import { getValidationErrorMessage, parseRequest } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateUrlWithDNS,
 } from '@/lib/core/security/input-validation.server'
@@ -73,6 +74,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
     const getResponse = await secureFetchWithPinnedIP(folderUrl, urlValidation.resolvedIP, {
       method: 'GET',
       headers,
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!getResponse.ok) {
@@ -104,6 +106,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       method: 'PUT',
       headers,
       body: JSON.stringify(body),
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!updateResponse.ok) {
diff --git a/apps/sim/app/api/tools/jupyter/proxy/route.ts b/apps/sim/app/api/tools/jupyter/proxy/route.ts
index d30a68a4a49..56118ba424e 100644
--- a/apps/sim/app/api/tools/jupyter/proxy/route.ts
+++ b/apps/sim/app/api/tools/jupyter/proxy/route.ts
@@ -5,6 +5,7 @@ import { jupyterProxyContract } from '@/lib/api/contracts/tools/jupyter'
 import { parseRequest } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateUrlWithDNS,
 } from '@/lib/core/security/input-validation.server'
@@ -77,6 +78,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       body: hasBody ? JSON.stringify(data.body) : undefined,
       allowHttp: true,
       maxRedirects: 0,
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     const text = await upstream.text()
diff --git a/apps/sim/app/api/tools/jupyter/upload/route.ts b/apps/sim/app/api/tools/jupyter/upload/route.ts
index 050e1512305..ff3656cce44 100644
--- a/apps/sim/app/api/tools/jupyter/upload/route.ts
+++ b/apps/sim/app/api/tools/jupyter/upload/route.ts
@@ -5,6 +5,7 @@ import { jupyterUploadContract } from '@/lib/api/contracts/storage-transfer'
 import { parseRequest } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import {
+  MAX_JSON_API_RESPONSE_BYTES,
   secureFetchWithPinnedIP,
   validateUrlWithDNS,
 } from '@/lib/core/security/input-validation.server'
@@ -118,6 +119,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       }),
       allowHttp: true,
       maxRedirects: 0,
+      maxResponseBytes: MAX_JSON_API_RESPONSE_BYTES,
     })
 
     if (!response.ok) {
diff --git a/apps/sim/app/api/tools/onepassword/get-item-file/route.ts b/apps/sim/app/api/tools/onepassword/get-item-file/route.ts
index 65efec88e06..2018b75ade1 100644
--- a/apps/sim/app/api/tools/onepassword/get-item-file/route.ts
+++ b/apps/sim/app/api/tools/onepassword/get-item-file/route.ts
@@ -6,6 +6,7 @@ import { onePasswordGetItemFileContract } from '@/lib/api/contracts/tools/onepas
 import { parseRequest, validationErrorResponse } from '@/lib/api/server'
 import { checkInternalAuth } from '@/lib/auth/hybrid'
 import { withRouteHandler } from '@/lib/core/utils/with-route-handler'
+import { MAX_FILE_SIZE } from '@/lib/uploads/utils/validation'
 import {
   connectRequest,
   createOnePasswordClient,
@@ -80,6 +81,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       apiKey: creds.apiKey!,
       path: `/v1/vaults/${params.vaultId}/items/${params.itemId}/files/${params.fileId}/content`,
       method: 'GET',
+      maxResponseBytes: MAX_FILE_SIZE,
     })
     if (!contentResponse.ok) {
       const errorData = await contentResponse.json().catch(() => ({}))
diff --git a/apps/sim/app/api/tools/onepassword/utils.ts b/apps/sim/app/api/tools/onepassword/utils.ts
index 6cb15624357..1b84548a59b 100644
--- a/apps/sim/app/api/tools/onepassword/utils.ts
+++ b/apps/sim/app/api/tools/onepassword/utils.ts
@@ -17,7 +17,10 @@ import { toError } from '@sim/utils/errors'
 import { generateId } from '@sim/utils/id'
 import * as ipaddr from 'ipaddr.js'
 import { isHosted } from '@/lib/core/config/env-flags'
-import { secureFetchWithPinnedIP } from '@/lib/core/security/input-validation.server'
+import {
+  MAX_JSON_API_RESPONSE_BYTES,
+  secureFetchWithPinnedIP,
+} from '@/lib/core/security/input-validation.server'
 
 /** Connect-format field type strings returned by normalization. */
 type ConnectFieldType =
@@ -344,7 +347,13 @@ export interface ConnectResponse {
   arrayBuffer: () => Promise<ArrayBuffer>
 }
 
-/** Proxy a request to the 1Password Connect Server. */
+/**
+ * Proxy a request to the 1Password Connect Server.
+ *
+ * The Connect server is self-hosted at a user-supplied `serverUrl`, so the response body
+ * is always capped. JSON endpoints use {@link MAX_JSON_API_RESPONSE_BYTES}; callers
+ * downloading file content pass a larger `maxResponseBytes` explicitly.
+ */
 export async function connectRequest(options: {
   serverUrl: string
   apiKey: string
@@ -352,6 +361,7 @@ export async function connectRequest(options: {
   method: string
   body?: unknown
   query?: string
+  maxResponseBytes?: number
 }): Promise<ConnectResponse> {
   const resolvedIP = await validateConnectServerUrl(options.serverUrl)
 
@@ -372,6 +382,7 @@ export async function connectRequest(options: {
     headers,
     body: options.body ? JSON.stringify(options.body) : undefined,
     allowHttp: true,
+    maxResponseBytes: options.maxResponseBytes ?? MAX_JSON_API_RESPONSE_BYTES,
   })
 }
 
diff --git a/apps/sim/lib/core/security/input-validation.server.ts b/apps/sim/lib/core/security/input-validation.server.ts
index f95ab62ce26..133c013a3eb 100644
--- a/apps/sim/lib/core/security/input-validation.server.ts
+++ b/apps/sim/lib/core/security/input-validation.server.ts
@@ -358,6 +358,11 @@ export interface SecureFetchOptions {
   body?: string | Buffer | Uint8Array
   timeout?: number
   maxRedirects?: number
+  /**
+   * Maximum bytes read from the response body. Defaults to
+   * {@link DEFAULT_MAX_RESPONSE_BYTES} — there is deliberately no "unlimited" mode, since
+   * many callers target a user-supplied host that can stream an endless body.
+   */
   maxResponseBytes?: number
   signal?: AbortSignal
   /** Drop the Authorization header when following a redirect, so it is not sent to the redirect target's origin. */
@@ -414,6 +419,19 @@ export interface SecureFetchResponse {
 
 const DEFAULT_MAX_REDIRECTS = 5
 
+/**
+ * Fail-safe ceiling applied by {@link secureFetchWithPinnedIP} when the caller does not
+ * pass `maxResponseBytes`. Many callers fetch a user-supplied host, so an omitted cap
+ * would let a malicious upstream stream an endless chunked body into memory until the
+ * process is OOM-killed. Set to the platform's largest legitimate payload (100MB, matching
+ * the upload limit); callers that need more must opt in explicitly, and callers handling
+ * small JSON should pass a much tighter cap.
+ */
+export const DEFAULT_MAX_RESPONSE_BYTES = 100 * 1024 * 1024
+
+/** Response cap for JSON/control-plane proxies to user-supplied hosts. */
+export const MAX_JSON_API_RESPONSE_BYTES = 10 * 1024 * 1024
+
 function isRedirectStatus(status: number): boolean {
   return status >= 300 && status < 400 && status !== 304
 }
@@ -937,6 +955,10 @@ export function createPinnedFetchWithDispatcher(
  * Performs a fetch with IP pinning to prevent DNS rebinding attacks.
  * Uses the pre-resolved IP address while preserving the original hostname for TLS SNI.
  * Follows redirects securely by validating each redirect target.
+ *
+ * The response body is always bounded — `options.maxResponseBytes` when supplied (and
+ * positive), otherwise {@link DEFAULT_MAX_RESPONSE_BYTES}. Exceeding the cap rejects with
+ * a {@link PayloadSizeLimitError} and destroys the socket.
  */
 export async function secureFetchWithPinnedIP(
   url: string,
@@ -945,7 +967,11 @@ export async function secureFetchWithPinnedIP(
   redirectCount = 0
 ): Promise<SecureFetchResponse> {
   const maxRedirects = options.maxRedirects ?? DEFAULT_MAX_REDIRECTS
-  const maxResponseBytes = options.maxResponseBytes
+  const requestedMaxResponseBytes = options.maxResponseBytes
+  const maxResponseBytes =
+    typeof requestedMaxResponseBytes === 'number' && requestedMaxResponseBytes > 0
+      ? requestedMaxResponseBytes
+      : DEFAULT_MAX_RESPONSE_BYTES
 
   return new Promise((resolve, reject) => {
     const parsed = new URL(url)
@@ -1037,8 +1063,15 @@ export async function secureFetchWithPinnedIP(
         }
       }
 
+      // Responses that carry no body (HEAD, 204, 304) may still advertise the resource's full
+      // size in content-length. That is metadata, not a payload, so it must not trip the cap —
+      // otherwise a HEAD probe of a large file, or a conditional-GET 304, would fail spuriously.
+      const isBodylessResponse =
+        (requestOptions.method || 'GET').toUpperCase() === 'HEAD' ||
+        statusCode === 204 ||
+        statusCode === 304
       const contentLength = headersRecord['content-length']
-      if (typeof maxResponseBytes === 'number' && maxResponseBytes > 0 && contentLength) {
+      if (contentLength && !isBodylessResponse) {
         const parsedLength = Number.parseInt(contentLength, 10)
         if (Number.isFinite(parsedLength) && parsedLength > maxResponseBytes) {
           cleanupAbort()
@@ -1074,11 +1107,7 @@ export async function secureFetchWithPinnedIP(
         start(controller) {
           nodeRes.on('data', (chunk: Buffer) => {
             totalBytes += chunk.length
-            if (
-              typeof maxResponseBytes === 'number' &&
-              maxResponseBytes > 0 &&
-              totalBytes > maxResponseBytes
-            ) {
+            if (totalBytes > maxResponseBytes) {
               cleanupAbort()
               controller.error(
                 new PayloadSizeLimitError({
diff --git a/apps/sim/lib/core/security/secure-fetch-response-cap.server.test.ts b/apps/sim/lib/core/security/secure-fetch-response-cap.server.test.ts
new file mode 100644
index 00000000000..78d6f21805d
--- /dev/null
+++ b/apps/sim/lib/core/security/secure-fetch-response-cap.server.test.ts
@@ -0,0 +1,102 @@
+/**
+ * @vitest-environment node
+ */
+import http from 'node:http'
+import type { AddressInfo } from 'node:net'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@sim/security/dns', () => ({
+  resolveHostAddresses: vi.fn(),
+  preferIpv4: (addresses: string[]) => addresses[0],
+}))
+
+vi.mock('@/lib/core/config/env-flags', () => ({
+  isHosted: false,
+  isPrivateDatabaseHostsAllowed: false,
+  getProxyUrl: () => undefined,
+}))
+
+import {
+  DEFAULT_MAX_RESPONSE_BYTES,
+  secureFetchWithPinnedIP,
+} from '@/lib/core/security/input-validation.server'
+
+const servers: http.Server[] = []
+
+afterEach(() => {
+  for (const server of servers.splice(0)) server.close()
+})
+
+/** Starts a throwaway loopback server and returns its origin. */
+async function startServer(handler: http.RequestListener): Promise<string> {
+  const server = http.createServer(handler)
+  servers.push(server)
+  await new Promise<void>((resolve) => server.listen(0, '127.0.0.1', resolve))
+  return `http://127.0.0.1:${(server.address() as AddressInfo).port}`
+}
+
+describe('secureFetchWithPinnedIP response cap', () => {
+  it('rejects a body that exceeds an explicit cap instead of buffering it', async () => {
+    const origin = await startServer((_req, res) => {
+      res.writeHead(200, { 'Content-Type': 'application/octet-stream' })
+      // Chunked (no content-length), so only the streaming counter can catch it.
+      for (let i = 0; i < 8; i++) res.write(Buffer.alloc(64 * 1024, 0x41))
+      res.end()
+    })
+
+    const response = await secureFetchWithPinnedIP(origin, '127.0.0.1', {
+      maxResponseBytes: 64 * 1024,
+    })
+
+    await expect(response.text()).rejects.toThrow(/response body/i)
+  })
+
+  it('rejects a content-length above the default cap when the caller passes no cap', async () => {
+    const origin = await startServer((_req, res) => {
+      res.writeHead(200, {
+        'Content-Type': 'application/json',
+        'Content-Length': String(DEFAULT_MAX_RESPONSE_BYTES + 1),
+      })
+      res.end('{}')
+    })
+
+    await expect(secureFetchWithPinnedIP(origin, '127.0.0.1', {})).rejects.toThrow(/response body/i)
+  })
+
+  it('reads a body that fits under the default cap', async () => {
+    const origin = await startServer((_req, res) => {
+      res.writeHead(200, { 'Content-Type': 'application/json' })
+      res.end('{"ok":true}')
+    })
+
+    const response = await secureFetchWithPinnedIP(origin, '127.0.0.1', {})
+
+    expect(await response.text()).toBe('{"ok":true}')
+  })
+
+  it('does not trip on a HEAD response advertising a size above the cap', async () => {
+    const origin = await startServer((_req, res) => {
+      res.writeHead(200, {
+        'Content-Type': 'video/mp4',
+        'Content-Length': String(DEFAULT_MAX_RESPONSE_BYTES + 1),
+      })
+      res.end()
+    })
+
+    const response = await secureFetchWithPinnedIP(origin, '127.0.0.1', { method: 'HEAD' })
+
+    expect(response.status).toBe(200)
+    expect(response.headers.get('content-type')).toBe('video/mp4')
+  })
+
+  it('does not trip on a 304 advertising a size above the cap', async () => {
+    const origin = await startServer((_req, res) => {
+      res.writeHead(304, { 'Content-Length': String(DEFAULT_MAX_RESPONSE_BYTES + 1) })
+      res.end()
+    })
+
+    const response = await secureFetchWithPinnedIP(origin, '127.0.0.1', {})
+
+    expect(response.status).toBe(304)
+  })
+})
diff --git a/apps/sim/lib/webhooks/polling/rss.ts b/apps/sim/lib/webhooks/polling/rss.ts
index 15de4122d0e..662eaf6e9a9 100644
--- a/apps/sim/lib/webhooks/polling/rss.ts
+++ b/apps/sim/lib/webhooks/polling/rss.ts
@@ -20,6 +20,17 @@ import { processPolledWebhookEvent } from '@/lib/webhooks/processor'
 
 const MAX_GUIDS_TO_TRACK = 500
 
+/**
+ * Cap on the feed body read from `feedUrl`. The URL is attacker-choosable (anyone can save
+ * an RSS trigger pointing at their own host) and the poller runs unattended, so an
+ * unbounded body would let a malicious feed grow the polling worker's heap until it is
+ * OOM-killed. This also bounds the XML handed to `rss-parser`, which has no input-size
+ * limit of its own. Set well above any real feed (they are typically well under 1MB) so the
+ * bound never trips a legitimate poll. The request strips `accept-encoding`, so this counts
+ * decoded bytes.
+ */
+const MAX_RSS_FEED_BYTES = 10 * 1024 * 1024
+
 interface RssWebhookConfig {
   feedUrl: string
   lastCheckedTimestamp?: string
@@ -208,6 +219,7 @@ async function fetchNewRssItems(
     const response = await secureFetchWithPinnedIP(config.feedUrl, urlValidation.resolvedIP!, {
       headers,
       timeout: 30000,
+      maxResponseBytes: MAX_RSS_FEED_BYTES,
     })
 
     if (response.status === 304) {
diff --git a/packages/testing/src/mocks/input-validation.mock.ts b/packages/testing/src/mocks/input-validation.mock.ts
index 06e8ca88e77..48b5a4a92d5 100644
--- a/packages/testing/src/mocks/input-validation.mock.ts
+++ b/packages/testing/src/mocks/input-validation.mock.ts
@@ -29,6 +29,8 @@ export const inputValidationMockFns = {
  * ```
  */
 export const inputValidationMock = {
+  DEFAULT_MAX_RESPONSE_BYTES: 100 * 1024 * 1024,
+  MAX_JSON_API_RESPONSE_BYTES: 10 * 1024 * 1024,
   validateUrlWithDNS: inputValidationMockFns.mockValidateUrlWithDNS,
   validateAndPinProxyUrl: inputValidationMockFns.mockValidateAndPinProxyUrl,
   validateDatabaseHost: inputValidationMockFns.mockValidateDatabaseHost,