Fix remote worktree diff compatibility

apps/server/src/environment/ServerEnvironment.test.ts

@@ -68,6 +68,7 @@ it.layer(NodeServices.layer)("ServerEnvironmentLive", (it) => {
       expect(first.environmentId).toBe(second.environmentId);
       expect(second.capabilities.repositoryIdentity).toBe(true);
       expect(second.capabilities.connectionProbe).toBe(true);
+      expect(second.capabilities.worktreeSourceControl).toBe(true);
     }),
   );
 

apps/server/src/environment/ServerEnvironment.ts

@@ -136,6 +136,7 @@ export const make = Effect.gen(function* () {
     capabilities: {
       repositoryIdentity: true,
       connectionProbe: true,
+      worktreeSourceControl: true,
     },
   };
 

apps/web/src/components/WorktreeSourceControl.logic.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from "vite-plus/test";
+
+import { resolveWorktreeDiffSource } from "./WorktreeSourceControl.logic";
+
+describe("resolveWorktreeDiffSource", () => {
+  it("uses the exact index-aware source when available", () => {
+    const sources = [
+      { id: "legacy", kind: "working-tree" as const },
+      { id: "staged", kind: "staged" as const },
+      { id: "unstaged", kind: "unstaged" as const },
+    ];
+
+    expect(resolveWorktreeDiffSource(sources, "unstaged")?.id).toBe("unstaged");
+    expect(resolveWorktreeDiffSource(sources, "staged")?.id).toBe("staged");
+  });
+
+  it("falls back to the legacy working-tree source for unstaged changes", () => {
+    const sources = [
+      { id: "legacy", kind: "working-tree" as const },
+      { id: "branch", kind: "branch-range" as const },
+    ];
+
+    expect(resolveWorktreeDiffSource(sources, "unstaged")?.id).toBe("legacy");
+  });
+
+  it("does not present a combined legacy diff as staged-only changes", () => {
+    const sources = [{ id: "legacy", kind: "working-tree" as const }];
+
+    expect(resolveWorktreeDiffSource(sources, "staged")).toBeUndefined();
+  });
+
+  it("does not mask a missing source in an index-aware response", () => {
+    const sources = [
+      { id: "legacy", kind: "working-tree" as const },
+      { id: "staged", kind: "staged" as const },
+    ];
+
+    expect(resolveWorktreeDiffSource(sources, "unstaged")).toBeUndefined();
+  });
+});

apps/web/src/components/WorktreeSourceControl.logic.ts

@@ -0,0 +1,23 @@
+import type { ReviewDiffPreviewSourceKind } from "@t3tools/contracts";
+
+export type WorktreeChangeScope = "staged" | "unstaged";
+
+/**
+ * Older environments only return the combined `working-tree` review source.
+ * Treat it as the unstaged source when no index-aware sources are present so
+ * mixed-version remote environments retain a useful read-only diff.
+ */
+export function resolveWorktreeDiffSource<T extends { readonly kind: ReviewDiffPreviewSourceKind }>(
+  sources: readonly T[],
+  selectedScope: WorktreeChangeScope,
+): T | undefined {
+  const exactSource = sources.find((source) => source.kind === selectedScope);
+  if (exactSource || selectedScope !== "unstaged") return exactSource;
+
+  const hasIndexAwareSources = sources.some(
+    (source) => source.kind === "staged" || source.kind === "unstaged",
+  );
+  return hasIndexAwareSources
+    ? undefined
+    : sources.find((source) => source.kind === "working-tree");
+}