fix(execution): count the runtime payload as secret material in scope

An execution with no mounted files and no env secret still carries `params` and
`contextVariables` into the sandbox — the runtime payload is serialized into a
private-input file, so resolved block outputs and workflow variables land as
plaintext regardless of `_sandboxFiles`. The scope predicate only looked at
mounts and env secrets, so a binary derived from them was classified
exact-empty.

The route has no catalog for those values and cannot tell a secret-bearing one
from an ordinary one, so they count as in scope. Only an execution with nothing
at all in scope earns an exact-empty binary.

This narrows where the relaxation applies rather than regressing anything: every
binary export was unknown before this branch, so a workflow Function block
carrying block references keeps exactly the behavior it has today. The
mothership path is unaffected — its tool sets no contextVariables, blockData, or
workflowVariables, which is the case this branch exists to fix.

Values, not keys, for the params check: `executionParams._context` is set to
undefined before the context is built, so a key count reads every execution as
carrying params.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/sim/app/api/function/execute/route.test.ts

@@ -890,6 +890,40 @@ describe('Function Execute API Route', () => {
       )
     })
 
+    it('keeps a binary export unknown when resolved context variables reach the sandbox', async () => {
+      envFlagsMock.isRemoteSandboxEnabled = true
+      mockExecuteInSandbox.mockResolvedValueOnce({
+        result: 'done',
+        stdout: '',
+        sandboxId: 'sandbox-123',
+        exportedFiles: { '/home/user/small.jpg': '/9j/4AAQ' },
+      })
+
+      const response = await POST(
+        createMockRequest('POST', {
+          code: 'print("done")',
+          language: 'python',
+          workspaceId: 'workspace-1',
+          // Resolved upstream block output — the route has no catalog to classify it.
+          contextVariables: { upstreamValue: 'could-be-anything' },
+          outputs: {
+            files: [
+              {
+                path: 'files/small.jpg',
+                sandboxPath: '/home/user/small.jpg',
+                mimeType: 'image/jpeg',
+              },
+            ],
+          },
+        })
+      )
+
+      expect(response.status).toBe(200)
+      expect(mockWriteWorkspaceFileByPath).toHaveBeenCalledWith(
+        expect.objectContaining({ secretProvenance: { status: 'unknown' } })
+      )
+    })
+
     it('keeps a binary export unknown when files were mounted without a provenance envelope', async () => {
       envFlagsMock.isRemoteSandboxEnabled = true
       mockExecuteInSandbox.mockResolvedValueOnce({

apps/sim/app/api/function/execute/route.ts

@@ -990,6 +990,12 @@ interface FunctionRouteExecutionContext {
   outputSecretPlaintextsByName: Map<string, string>
   mountedFileSecretProvenanceScanner?: MountedFileSecretProvenanceScanner
   hasMountedSandboxFiles: boolean
+  /**
+   * Whether the serialized runtime payload carried `params` or `contextVariables` into the sandbox.
+   * Those are resolved block outputs and workflow variables — the route has no catalog for them, so
+   * it cannot tell a secret-bearing one from an ordinary value.
+   */
+  hasUnclassifiedRuntimeInputs: boolean
 }
 
 type ResolvedSecretNamesMetadataType =
@@ -1219,9 +1225,15 @@ function activateOutputSecretProvenance(
  * are unclassifiable rather than clean: absence of an envelope is absence of evidence, not evidence
  * the mount carried nothing. Those fail closed here so the classification can never be stronger
  * than what the caller actually attested to.
+ *
+ * The serialized runtime payload counts too. It carries `params` and `contextVariables` — resolved
+ * block outputs and workflow variables — into the sandbox as a private-input file, and the route
+ * has no catalog to tell a secret-bearing one from an ordinary value. Only an execution with
+ * nothing at all in scope earns an exact-empty binary.
  */
 function hasSecretMaterialInScope(context: FunctionRouteExecutionContext): boolean {
   if (context.outputSecretPlaintextsByName.size > 0) return true
+  if (context.hasUnclassifiedRuntimeInputs) return true
   const scanner = context.mountedFileSecretProvenanceScanner
   return scanner ? scanner.hasSecrets : context.hasMountedSandboxFiles
 }
@@ -2031,6 +2043,12 @@ export const POST = withRouteHandler(async (req: NextRequest) => {
       outputSecretPlaintextsByName: new Map(),
       mountedFileSecretProvenanceScanner,
       hasMountedSandboxFiles: (_sandboxFiles?.length ?? 0) > 0,
+      // Values, not keys: `executionParams._context` is explicitly set to undefined just above,
+      // so a key count would read every execution as carrying params. Raised below once the
+      // resolved context variables are known.
+      hasUnclassifiedRuntimeInputs: Object.values(executionParams).some(
+        (value) => value !== undefined
+      ),
     }
     for (const [name, plaintext] of Object.entries(envVars)) {
       if (!plaintext) continue
@@ -2074,6 +2092,11 @@ export const POST = withRouteHandler(async (req: NextRequest) => {
       ...codeResolution.contextVariables,
       ...preResolvedContextVariables,
     }
+    // Resolved block outputs and workflow variables ride into the sandbox inside the runtime
+    // payload, so an output file can carry them even with nothing mounted and no env secret.
+    if (Object.keys(contextVariables).length > 0) {
+      routeContext.hasUnclassifiedRuntimeInputs = true
+    }
     const compilation = await compileCodePlaceholders({
       code: codeResolution.resolvedCode,
       language: lang,