diff --git a/apps/sim/lib/internal/file/delegated-caller-write.integration.ts b/apps/sim/lib/internal/file/delegated-caller-write.integration.ts
new file mode 100644
index 00000000000..d234c9c713f
--- /dev/null
+++ b/apps/sim/lib/internal/file/delegated-caller-write.integration.ts
@@ -0,0 +1,146 @@
+/**
+ * Mothership runs a file tool through `tools execute`, whose use case authorizes the chat's
+ * delegated principal for `sim:tool-execution`. The File write that follows must still reach the
+ * workspace-file use cases, which admit only `sim:workspace-files`, and must still refuse a
+ * subject or workspace the original delegation does not cover. Exercises the real handler,
+ * application authorization, metadata and local storage against Postgres.
+ */
+import { mkdtempSync } from 'node:fs'
+import { rm } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import path from 'node:path'
+import type { SubjectDelegatedPrincipal } from '@sim/auth/principal'
+import { db } from '@sim/db'
+import { auditLog, organization, user, workspace, workspaceFiles } from '@sim/db/schema'
+import { deleteWorkspaceFixture } from '@sim/db/testing/workspace-fixtures'
+import { createDelegatedPrincipal } from '@sim/testing/factories/principal.factory'
+import { setUploadDirServer, uploadsSetupMock } from '@sim/testing/mocks/uploads-setup.mock'
+import { generateId } from '@sim/utils/id'
+import { and, eq, inArray } from 'drizzle-orm'
+import { afterAll, beforeAll, describe, expect, it, vi } from 'vitest'
+
+vi.mock('@/lib/uploads/core/setup.server', () => uploadsSetupMock)
+
+import { executeFileTool } from '@/lib/internal/file/execute-tool'
+import {
+  createKnowledgeAclFixtureIds,
+  seedKnowledgeAclFixture,
+} from '@/lib/knowledge/__integration__/seed-source-access-fixture'
+import { uploadCopilotFile } from '@/lib/uploads/contexts/copilot/file-manager'
+
+const fixtures: ReturnType<typeof createKnowledgeAclFixtureIds>[] = []
+
+async function seed() {
+  const ids = createKnowledgeAclFixtureIds()
+  fixtures.push(ids)
+  await seedKnowledgeAclFixture(ids)
+  return ids
+}
+
+type Fixture = Awaited<ReturnType<typeof seed>>
+
+/** The chat principal `tools execute` hands to the tool layer. */
+function toolExecutionPrincipal(subjectUserId: string, workspaceId: string) {
+  return createDelegatedPrincipal({
+    subjectUserId,
+    workspaceId,
+    audience: 'sim:tool-execution',
+    resourceScope: { chatId: generateId() },
+  })
+}
+
+/** A generated image as `image_generate` stores it outside a workflow run. */
+async function generatedImage(ownerId: string) {
+  return uploadCopilotFile({
+    buffer: Buffer.from(`image bytes ${generateId()}`),
+    fileName: `${generateId()}.webp`,
+    contentType: 'image/webp',
+    userId: ownerId,
+  })
+}
+
+async function writeCopy(
+  ids: Fixture,
+  principal: SubjectDelegatedPrincipal,
+  fileInput: Awaited<ReturnType<typeof generatedImage>>
+) {
+  const fileName = `saved-${generateId()}.webp`
+  const response = await executeFileTool({
+    toolId: 'file_write',
+    input: { operation: 'write', workspaceId: ids.workspaceId, fileName, fileInput },
+    headers: new Headers(),
+    requestId: generateId(),
+    context: {
+      workflowId: '',
+      workspaceId: ids.workspaceId,
+      userId: principal.subjectUserId,
+      callerPrincipal: principal,
+    },
+  })
+  const [saved] = await db
+    .select({ id: workspaceFiles.id, sizeBytes: workspaceFiles.sizeBytes })
+    .from(workspaceFiles)
+    .where(
+      and(
+        eq(workspaceFiles.workspaceId, ids.workspaceId),
+        eq(workspaceFiles.originalName, fileName),
+        eq(workspaceFiles.context, 'workspace')
+      )
+    )
+  return { status: response.status, saved }
+}
+
+const uploadRoot = mkdtempSync(path.join(tmpdir(), 'sim-delegated-caller-write-'))
+
+beforeAll(() => {
+  setUploadDirServer(uploadRoot)
+})
+
+afterAll(async () => {
+  try {
+    for (const ids of fixtures) {
+      await db.delete(auditLog).where(eq(auditLog.workspaceId, ids.workspaceId))
+      await db
+        .delete(workspaceFiles)
+        .where(inArray(workspaceFiles.userId, [ids.aliceId, ids.bobId]))
+      await deleteWorkspaceFixture(db, eq(workspace.id, ids.workspaceId))
+      await db.delete(organization).where(eq(organization.id, ids.organizationId))
+      await db.delete(user).where(inArray(user.id, [ids.aliceId, ids.bobId]))
+    }
+    await rm(uploadRoot, { recursive: true, force: true })
+  } finally {
+    await db.$client.end()
+  }
+})
+
+describe('a File write run directly from a Mothership chat', () => {
+  it('saves a generated image into Workspace Files', async () => {
+    const ids = await seed()
+    const image = await generatedImage(ids.aliceId)
+
+    const result = await writeCopy(ids, toolExecutionPrincipal(ids.aliceId, ids.workspaceId), image)
+
+    expect(result.status).toBe(200)
+    expect(result.saved?.sizeBytes).toBe(image.size)
+  })
+
+  it('still refuses a member whose role cannot write', async () => {
+    const ids = await seed()
+    const image = await generatedImage(ids.bobId)
+
+    const result = await writeCopy(ids, toolExecutionPrincipal(ids.bobId, ids.workspaceId), image)
+
+    expect(result.status).toBe(403)
+    expect(result.saved).toBeUndefined()
+  })
+
+  it('still refuses a delegation minted for another workspace', async () => {
+    const ids = await seed()
+    const image = await generatedImage(ids.aliceId)
+
+    const result = await writeCopy(ids, toolExecutionPrincipal(ids.aliceId, generateId()), image)
+
+    expect(result.status).toBe(403)
+    expect(result.saved).toBeUndefined()
+  })
+})
diff --git a/apps/sim/lib/internal/file/execute-tool.ts b/apps/sim/lib/internal/file/execute-tool.ts
index 88c3950d70b..15764b6d1db 100644
--- a/apps/sim/lib/internal/file/execute-tool.ts
+++ b/apps/sim/lib/internal/file/execute-tool.ts
@@ -1,4 +1,8 @@
-import { resolvePrincipalAttribution, resolvePrincipalSubject } from '@sim/auth/principal'
+import {
+  type Principal,
+  resolvePrincipalAttribution,
+  resolvePrincipalSubject,
+} from '@sim/auth/principal'
 import { createLogger } from '@sim/logger'
 import { getErrorMessage, toError } from '@sim/utils/errors'
 import { z } from 'zod'
@@ -25,6 +29,7 @@ import {
 import { parseInternalToolInput } from '@/lib/internal/tool-operations/parse-input'
 import type { InternalToolOperationHandler } from '@/lib/internal/tool-operations/types'
 import { WORKSPACE_FILES_DELEGATION_AUDIENCE } from '@/lib/workspace-files/application/authorization'
+import { rebindWorkspaceFileDelegatedPrincipal } from '@/lib/workspace-files/application/delegated-principal'
 import { searchWorkspaceFileContent } from '@/lib/workspace-files/application/search-workspace-file-content'
 import {
   FILE_SEARCH_DEFAULT_MAX_RESULTS,
@@ -79,6 +84,34 @@ const fileSearchInputSchema = z
   })
   .strict()
 
+/**
+ * A delegated caller arrives with its calling use case's audience (`sim:tool-execution`),
+ * but workspace-file use cases admit only `sim:workspace-files`; they still check the
+ * subject's access. A delegation for another workspace is left for them to refuse.
+ */
+function bindWorkspaceFilePrincipal(
+  principal: Principal,
+  workspaceId: string,
+  requestId: string
+): Principal {
+  if (
+    principal.kind !== 'delegated' ||
+    principal.audience === WORKSPACE_FILES_DELEGATION_AUDIENCE ||
+    principal.workspaceId !== workspaceId
+  ) {
+    return principal
+  }
+  const scope = principal.resourceScope
+  return rebindWorkspaceFileDelegatedPrincipal({
+    principal,
+    workspaceId,
+    delegationId: `file-tool:${requestId}`,
+    fileId: scope?.fileId,
+    chatId: scope?.chatId,
+    executionId: scope?.executionId,
+  })
+}
+
 export const executeFileTool: InternalToolOperationHandler = async (request) => {
   request.signal?.throwIfAborted()
   if (!FILE_MANAGE_TOOL_IDS.has(request.toolId)) {
@@ -117,7 +150,11 @@ export const executeFileTool: InternalToolOperationHandler = async (request) =>
   try {
     const principal =
       request.context.callerPrincipal && !request.context.executorDelegationOrigin
-        ? request.context.callerPrincipal
+        ? bindWorkspaceFilePrincipal(
+            request.context.callerPrincipal,
+            workspaceId,
+            request.requestId
+          )
         : await createExecutorPrincipalFromExecutionContext({
             context: request.context,
             audience: WORKSPACE_FILES_DELEGATION_AUDIENCE,
diff --git a/apps/sim/lib/internal/image/operations.ts b/apps/sim/lib/internal/image/operations.ts
index 82f61d11c66..0feef97bf1f 100644
--- a/apps/sim/lib/internal/image/operations.ts
+++ b/apps/sim/lib/internal/image/operations.ts
@@ -1,7 +1,7 @@
 import { createLogger } from '@sim/logger'
 import { getErrorMessage } from '@sim/utils/errors'
 import { interruptibleSleep } from '@sim/utils/helpers'
-import { isRecordLike } from '@sim/utils/object'
+import { isRecordLike, omit } from '@sim/utils/object'
 import { getUserFacingErrorMessage } from '@/lib/core/errors/database-query-error'
 import { getMaxExecutionTimeout } from '@/lib/core/execution-limits'
 import {
@@ -23,6 +23,7 @@ import { recordServiceMeteringFailure } from '@/lib/mothership/billing/service-o
 import { type FalAICostMetadata, getFalAICostMetadata } from '@/lib/tools/falai-pricing'
 import { uploadCopilotFile } from '@/lib/uploads/contexts/copilot'
 import { uploadExecutionFile } from '@/lib/uploads/contexts/execution'
+import { resolveStoredFileMetadata } from '@/lib/uploads/utils/stored-file-metadata'
 
 const logger = createLogger('ImageOperations')
 const MAX_IMAGE_BYTES = MAX_REMOTE_IMAGE_BYTES
@@ -595,8 +596,11 @@ async function storeGeneratedImage(
   context: ImageOperationContext
 ): Promise<StoredImageResponse> {
   context.signal?.throwIfAborted()
-  const timestamp = Date.now()
-  const safeFileName = imageResult.fileName || `image-${imageResult.provider}-${timestamp}.png`
+  const { fileName, mimeType: contentType } = resolveStoredFileMetadata(
+    imageResult.fileName || `image-${imageResult.provider}-${Date.now()}.png`,
+    imageResult.contentType,
+    imageResult.buffer
+  )
   const executionContext =
     context.workspaceId && context.workflowId && context.executionId
       ? {
@@ -606,56 +610,32 @@ async function storeGeneratedImage(
         }
       : null
 
-  if (executionContext) {
-    const imageFile = await uploadExecutionFile(
-      executionContext,
-      imageResult.buffer,
-      safeFileName,
-      imageResult.contentType,
-      context.userId
-    )
-    context.signal?.throwIfAborted()
-
-    return {
-      content: imageFile.url,
-      imageUrl: imageFile.url,
-      imageFile,
-      fileName: safeFileName,
-      contentType: imageResult.contentType,
-      provider: imageResult.provider,
-      model: imageResult.model,
-      metadata: {
-        provider: imageResult.provider,
-        model: imageResult.model,
-        description: imageResult.description,
-        revisedPrompt: imageResult.revisedPrompt,
-        seed: imageResult.seed,
-        jobId: imageResult.jobId,
-        contentType: imageResult.contentType,
-      },
-      __falaiCostDollars: imageResult.falaiCost?.costDollars,
-      __falaiBilling: imageResult.falaiCost,
-    }
-  }
-
-  const fileInfo = await uploadCopilotFile({
-    buffer: imageResult.buffer,
-    fileName: safeFileName,
-    contentType: imageResult.contentType,
-    userId: context.userId,
-  })
+  // A stored file output is kept as is; a bare URL would be downloaded and stored again.
+  const imageFile = executionContext
+    ? await uploadExecutionFile(
+        executionContext,
+        imageResult.buffer,
+        fileName,
+        contentType,
+        context.userId
+      )
+    : omit(
+        await uploadCopilotFile({
+          buffer: imageResult.buffer,
+          fileName,
+          contentType,
+          userId: context.userId,
+        }),
+        ['mimeType']
+      )
   context.signal?.throwIfAborted()
-  const imageUrl = fileInfo.url
-  logger.info(`[${context.requestId}] Stored generated image fallback`, {
-    fileName: safeFileName,
-    size: imageResult.buffer.length,
-  })
 
   return {
-    content: imageUrl,
-    imageUrl,
-    fileName: safeFileName,
-    contentType: imageResult.contentType,
+    content: imageFile.url,
+    imageUrl: imageFile.url,
+    imageFile,
+    fileName,
+    contentType,
     provider: imageResult.provider,
     model: imageResult.model,
     metadata: {
@@ -665,7 +645,7 @@ async function storeGeneratedImage(
       revisedPrompt: imageResult.revisedPrompt,
       seed: imageResult.seed,
       jobId: imageResult.jobId,
-      contentType: imageResult.contentType,
+      contentType,
     },
     __falaiCostDollars: imageResult.falaiCost?.costDollars,
     __falaiBilling: imageResult.falaiCost,
diff --git a/apps/sim/lib/internal/tool-operations/types.ts b/apps/sim/lib/internal/tool-operations/types.ts
index 605899e1adf..9a6db19cab7 100644
--- a/apps/sim/lib/internal/tool-operations/types.ts
+++ b/apps/sim/lib/internal/tool-operations/types.ts
@@ -22,7 +22,10 @@ export interface InternalToolOperationContext {
   executorDelegationOrigin?: ExecutorDelegationOrigin
   /** Trusted source block for saved MCP operation restrictions. */
   mcpBlockId?: string
-  /** Authenticated direct caller, supplied by an authorized use case, never tool input. */
+  /**
+   * Authenticated direct caller, supplied by an authorized use case, never tool input. A
+   * delegated principal carries that use case's audience; rebind it before another use case.
+   */
   callerPrincipal?: Principal
   copilotToolExecution?: boolean
   copilotInteractionMode?: 'interactive' | 'headless'