diff --git a/backend/src/workspaces/preprocessing-service.ts b/backend/src/workspaces/preprocessing-service.ts
index 094ba766..c8e4c876 100644
--- a/backend/src/workspaces/preprocessing-service.ts
+++ b/backend/src/workspaces/preprocessing-service.ts
@@ -584,9 +584,9 @@ export class WorkspacePreprocessingService {
   } | undefined {
     const evidence = workspace.evidence;
     if (!evidence) return undefined;
-    if (evidence.source.type === "filesystem") {
-      return { status: "blocked", code: "evidence_materialization_required" };
-    }
+    // P6: filesystem Evidence is materialized from the pinned commit at activation, so the
+    // engine may proceed directly against the immutable revision content root.
+    if (evidence.source.type === "filesystem") return undefined;
     if (evidence.source.type === "http") {
       for (const value of evidence.source.uris) {
         const host = new URL(value).hostname;
diff --git a/backend/test/workspace-preprocessing-service.test.ts b/backend/test/workspace-preprocessing-service.test.ts
index 18c2ff11..276cf5a8 100644
--- a/backend/test/workspace-preprocessing-service.test.ts
+++ b/backend/test/workspace-preprocessing-service.test.ts
@@ -289,11 +289,16 @@ test("index schema fails closed when semantic preflight refuses the collection",
   expect(runChild).not.toHaveBeenCalled();
 });
 
-test("evidence stops before child execution for filesystem sources and refuses private HTTP hosts outside the allowlist", async () => {
+test("filesystem Evidence proceeds after materialization and private HTTP hosts outside the allowlist are refused", async () => {
   const filesystem = fixture(filesystemWorkspace);
-  const blocked = await filesystem.service.preprocessEvidence({ workspaceId: "fs-workspace" });
-  expect(blocked).toMatchObject({ status: "blocked", code: "evidence_materialization_required" });
-  expect(filesystem.runChild).not.toHaveBeenCalled();
+  filesystem.runChild.mockResolvedValueOnce({
+    exitCode: 0,
+    stdout: JSON.stringify({ status: "succeeded", counts: { added: 1 } }),
+    stderr: "",
+  });
+  const materialized = await filesystem.service.preprocessEvidence({ workspaceId: "fs-workspace" });
+  expect(materialized).toMatchObject({ status: "succeeded", code: "ok" });
+  expect(filesystem.runChild).toHaveBeenCalledTimes(1);
 
   const httpDataRoot = mkdtempSync(join(tmpdir(), "tht-preprocessing-service-"));
   roots.push(httpDataRoot);