diff --git a/apps/sim/lib/copilot/tool-executor/executor.test.ts b/apps/sim/lib/copilot/tool-executor/executor.test.ts
index dff1fc1c42f..772cccc5ca7 100644
--- a/apps/sim/lib/copilot/tool-executor/executor.test.ts
+++ b/apps/sim/lib/copilot/tool-executor/executor.test.ts
@@ -242,7 +242,12 @@ describe('copilot tool executor fallback', () => {
     const runWorkflowHandler = vi.fn().mockResolvedValue({ success: true, output: { ran: true } })
     registerHandler('run_workflow', runWorkflowHandler)
 
-    const context = { userId: 'user-1', workflowId: 'workflow-1', workspaceId: 'ws-1' }
+    const context = {
+      userId: 'user-1',
+      workflowId: 'workflow-1',
+      workspaceId: 'ws-1',
+      userPermission: 'write',
+    }
     const result = await executeTool('run_workflow', { workflow_input: {} }, context)
 
     expect(runWorkflowHandler).toHaveBeenCalledWith({ workflow_input: {} }, context)
@@ -250,6 +255,35 @@ describe('copilot tool executor fallback', () => {
     expect(result).toEqual({ success: true, output: { ran: true } })
   })
 
+  /**
+   * `run_workflow` carries no catalog permission — the browser path authorizes it through the
+   * workflow APIs against the caller's own session. The headless fallback has no session, so
+   * without a bar of its own a deliberately capped run (an unattributed inbox message) would
+   * still execute workflows under the principal it was capped away from.
+   */
+  it.each([['read'], [undefined]] as const)(
+    'refuses the headless client fallback for a %s permission',
+    async (userPermission) => {
+      isKnownTool.mockReturnValue(true)
+      isSimExecuted.mockReturnValue(false)
+      isClientExecuted.mockReturnValue(true)
+
+      const runWorkflowHandler = vi.fn().mockResolvedValue({ success: true })
+      registerHandler('run_workflow', runWorkflowHandler)
+
+      const result = await executeTool(
+        'run_workflow',
+        { workflow_input: {} },
+        { userId: 'user-1', workflowId: 'workflow-1', workspaceId: 'ws-1', userPermission }
+      )
+
+      expect(result.success).toBe(false)
+      expect(result.error).toContain('requires write access')
+      expect(runWorkflowHandler).not.toHaveBeenCalled()
+      expect(executeAppTool).not.toHaveBeenCalled()
+    }
+  )
+
   it('falls back to app tool executor for client-routed tools with no registered handler', async () => {
     isKnownTool.mockReturnValue(true)
     isSimExecuted.mockReturnValue(false)
diff --git a/apps/sim/lib/copilot/tool-executor/executor.ts b/apps/sim/lib/copilot/tool-executor/executor.ts
index e934803dcfe..e4f7ba3a3ee 100644
--- a/apps/sim/lib/copilot/tool-executor/executor.ts
+++ b/apps/sim/lib/copilot/tool-executor/executor.ts
@@ -38,7 +38,26 @@ export async function executeTool(
   params: Record<string, unknown>,
   context: ToolExecutionContext
 ): Promise<ToolExecutionResult> {
-  const requiredPermission = getToolEntry(toolId)?.requiredPermission
+  // Client-routed tools (e.g. run_workflow) are normally executed in the browser and never
+  // reach this point in interactive mode. In headless mode (Mothership block, no browser) there
+  // is no client to delegate to, so fall back to the registered server-side handler when one
+  // exists — otherwise the call would route to executeAppTool and throw "Tool not found".
+  const usesHeadlessClientFallback = isClientExecuted(toolId) && hasHandler(toolId)
+
+  /**
+   * Client-routed tools carry no catalog `requiredPermission` because the browser runs them
+   * through the workflow APIs, which authorize the caller's own session. The headless fallback
+   * has no session to authorize against and runs under the request's principal instead, so it
+   * has to supply a bar of its own.
+   *
+   * Without one, a run whose permission was deliberately capped still reaches `run_workflow`,
+   * and `runWorkflowFromCopilot` executes with `enforceCredentialAccess` — resolving the
+   * principal's workspace and personal secrets. That is the hole an unattributed inbox message
+   * leaves open: `resolveInboxExecutionActor` refuses it a secret actor, but the run still
+   * carries the workspace owner as principal.
+   */
+  const requiredPermission =
+    getToolEntry(toolId)?.requiredPermission ?? (usesHeadlessClientFallback ? 'write' : undefined)
   if (
     requiredPermission &&
     !permissionSatisfies(
@@ -54,13 +73,8 @@ export async function executeTool(
 
   const normalizedParams = normalizeToolParams(toolId, params, context)
 
-  // Client-routed tools (e.g. run_workflow) are normally executed in the browser and never
-  // reach this point in interactive mode. In headless mode (Mothership block, no browser) there
-  // is no client to delegate to, so fall back to the registered server-side handler when one
-  // exists — otherwise the call would route to executeAppTool and throw "Tool not found".
   const canUseRegisteredHandler =
-    isKnownTool(toolId) &&
-    (isSimExecuted(toolId) || (isClientExecuted(toolId) && hasHandler(toolId)))
+    isKnownTool(toolId) && (isSimExecuted(toolId) || usesHeadlessClientFallback)
   if (!canUseRegisteredHandler) {
     const appParams = buildAppToolParams(normalizedParams, context)
     const options = {
diff --git a/apps/sim/lib/mothership/inbox/executor.test.ts b/apps/sim/lib/mothership/inbox/executor.test.ts
index f8231124a92..eaaf105c0a9 100644
--- a/apps/sim/lib/mothership/inbox/executor.test.ts
+++ b/apps/sim/lib/mothership/inbox/executor.test.ts
@@ -119,7 +119,7 @@ const WORKSPACE = {
   inboxMountedSecrets: ['INBOX_KEY'],
 }
 
-describe('Inbox raw-secret actor', () => {
+describe('Inbox execution actor', () => {
   beforeEach(() => {
     vi.clearAllMocks()
     resetDbChainMock()
@@ -150,6 +150,8 @@ describe('Inbox raw-secret actor', () => {
       expect.objectContaining({
         userId: 'member-1',
         secretActorUserId: 'member-1',
+        /** Their own, so an emailed request reaches exactly what they could in the app. */
+        userPermission: 'write',
         secretMountPolicy: {
           secretScope: 'selected',
           mountedSecrets: ['INBOX_KEY'],
@@ -158,10 +160,33 @@ describe('Inbox raw-secret actor', () => {
     )
   })
 
-  it('keeps owner execution fallback but removes raw-secret authority for an external sender', async () => {
+  it('does not lend a read-only member write authority', async () => {
+    queueTableRows(schemaMock.mothershipInboxTask, [INBOX_TASK])
+    queueTableRows(schemaMock.workspace, [WORKSPACE])
+    queueTableRows(schemaMock.user, [{ id: 'member-1' }])
+    mockCheckWorkspaceAccess.mockResolvedValue({ permission: 'read' })
+    mockGetUserEntityPermissions.mockResolvedValue('read')
+
+    await executeInboxTask('task-1')
+
+    expect(mockRunHeadlessCopilotLifecycle).toHaveBeenCalledWith(
+      expect.any(Object),
+      expect.objectContaining({ userId: 'member-1', userPermission: 'read' })
+    )
+  })
+
+  /**
+   * The owner identity is there for billing and workspace reads, not to lend an unknown
+   * sender the owner's authority. Without the read ceiling the write-gated workflow tools
+   * would let an allowlisted external correspondent build and run a workflow as the owner,
+   * which resolves the owner's workspace and personal secrets — the same reach the null
+   * secret actor already refuses for a direct mount.
+   */
+  it('caps an external sender at read even when the owner is an admin', async () => {
     queueTableRows(schemaMock.mothershipInboxTask, [INBOX_TASK])
     queueTableRows(schemaMock.workspace, [WORKSPACE])
     queueTableRows(schemaMock.user, [])
+    mockCheckWorkspaceAccess.mockResolvedValue({ permission: 'admin' })
 
     await executeInboxTask('task-1')
 
@@ -170,6 +195,7 @@ describe('Inbox raw-secret actor', () => {
       expect.objectContaining({
         userId: 'owner-1',
         secretActorUserId: null,
+        userPermission: 'read',
         secretMountPolicy: {
           secretScope: 'selected',
           mountedSecrets: ['INBOX_KEY'],
@@ -178,4 +204,16 @@ describe('Inbox raw-secret actor', () => {
     )
     expect(mockGetUserEntityPermissions).not.toHaveBeenCalled()
   })
+
+  it('leaves an external sender with no permission at none rather than promoting to read', async () => {
+    queueTableRows(schemaMock.mothershipInboxTask, [INBOX_TASK])
+    queueTableRows(schemaMock.workspace, [WORKSPACE])
+    queueTableRows(schemaMock.user, [])
+    mockCheckWorkspaceAccess.mockResolvedValue({ permission: null })
+
+    await executeInboxTask('task-1')
+
+    const [, options] = mockRunHeadlessCopilotLifecycle.mock.calls[0]
+    expect(options.userPermission).toBeUndefined()
+  })
 })
diff --git a/apps/sim/lib/mothership/inbox/executor.ts b/apps/sim/lib/mothership/inbox/executor.ts
index 02eb799d218..35d21df8cb0 100644
--- a/apps/sim/lib/mothership/inbox/executor.ts
+++ b/apps/sim/lib/mothership/inbox/executor.ts
@@ -27,7 +27,11 @@ import type { AgentMailAttachment } from '@/lib/mothership/inbox/types'
 import { buildStorageKeySegment } from '@/lib/uploads/core/storage-key'
 import { uploadFile } from '@/lib/uploads/core/storage-service'
 import { createFileContent, type MessageContent } from '@/lib/uploads/utils/file-utils'
-import { checkWorkspaceAccess, getUserEntityPermissions } from '@/lib/workspaces/permissions/utils'
+import {
+  checkWorkspaceAccess,
+  getUserEntityPermissions,
+  type PermissionType,
+} from '@/lib/workspaces/permissions/utils'
 import { getWorkspaceBilledAccountUserId } from '@/lib/workspaces/utils'
 
 const logger = createLogger('InboxExecutor')
@@ -216,7 +220,7 @@ export async function executeInboxTask(taskId: string): Promise<void> {
     }
 
     const workspaceAccess = await checkWorkspaceAccess(ws.id, userId)
-    const userPermission = workspaceAccess.permission
+    const userPermission = inboxToolPermission(actor, workspaceAccess.permission)
     const secretMountPolicy = normalizeSecretMountPolicy({
       secretScope: ws.inboxSecretScope,
       mountedSecrets: ws.inboxMountedSecrets,
@@ -343,12 +347,49 @@ export async function executeInboxTask(taskId: string): Promise<void> {
  * Resolve the execution and raw-secret actors independently. Workspace members
  * execute and mount secrets as themselves. External senders retain the existing
  * owner execution fallback but receive no raw-secret actor.
+ *
+ * The owner fallback exists because billing attribution and workspace reads need
+ * a real user, not because an unknown sender should act as the owner. A null
+ * `secretActorUserId` is therefore the run's "no caller" signal, and callers must
+ * treat it as one everywhere authority is derived — see
+ * {@link inboxToolPermission}.
  */
 interface InboxExecutionActor {
   executionUserId: string
+  /** Null when no workspace member owns this message. */
   secretActorUserId: string | null
 }
 
+/**
+ * How far an inbox run's tools may reach.
+ *
+ * An attributed message uses the sender's own workspace permission, which makes an
+ * emailed request equivalent to that member performing it in the app — a read-only
+ * member still cannot run or edit anything.
+ *
+ * An unattributed message resolves to the workspace owner so the run has a real
+ * user for billing and workspace reads, and the owner is typically an admin. Left
+ * alone, that hands an allowlisted external correspondent the owner's write
+ * authority: `create_workflow` and `edit_workflow` gate on
+ * `requiredPermission: 'write'`, and `run_workflow` is gated by the headless
+ * client-fallback bar in `executeTool` — it carries no catalog permission of its
+ * own. A workflow built or run through any of them executes with
+ * `enforceCredentialAccess`, resolving the owner's workspace *and personal*
+ * secrets. That is the same reach `secretActorUserId: null` already refuses for a
+ * direct mount, so refusing it here keeps one answer rather than two.
+ *
+ * Read is the ceiling rather than no permission at all because answering an
+ * external correspondent from workspace context is the point of the inbox; only
+ * mutation and execution are withheld.
+ */
+function inboxToolPermission(
+  actor: InboxExecutionActor,
+  workspacePermission: PermissionType | null
+): PermissionType | null {
+  if (actor.secretActorUserId !== null) return workspacePermission
+  return workspacePermission === null ? null : 'read'
+}
+
 async function resolveInboxExecutionActor(
   senderEmail: string,
   ws: { id: string; ownerId: string }