diff --git a/apps/loopover-ui/src/lib/maintainer-settings-preview.test.ts b/apps/loopover-ui/src/lib/maintainer-settings-preview.test.ts
new file mode 100644
index 0000000000..e0c4a29074
--- /dev/null
+++ b/apps/loopover-ui/src/lib/maintainer-settings-preview.test.ts
@@ -0,0 +1,152 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  buildSettingsPreviewRequest,
+  extractPreviewRepoOptions,
+  findPreviewScenario,
+  parseLinkedIssues,
+  parsePreviewLabels,
+  PREVIEW_SCENARIOS,
+  splitRepoFullName,
+  splitReviewabilityPr,
+  type PreviewFormState,
+} from "@/lib/maintainer-settings-preview";
+
+describe("splitRepoFullName", () => {
+  it("accepts a well-formed owner/repo pair", () => {
+    expect(splitRepoFullName("acme/repo")).toEqual({ owner: "acme", repo: "repo" });
+  });
+
+  it("trims surrounding whitespace before splitting", () => {
+    expect(splitRepoFullName("  acme/repo  ")).toEqual({ owner: "acme", repo: "repo" });
+  });
+
+  // Regression (#7783): the old `[owner, repo, extra]` destructuring only looked at the 3rd segment,
+  // so any input whose 3rd `/`-segment was empty slipped through as a truncated owner/repo pair.
+  it("rejects a trailing slash instead of silently truncating", () => {
+    expect(splitRepoFullName("acme/repo/")).toBeNull();
+  });
+
+  it("rejects a double slash with a trailing segment", () => {
+    expect(splitRepoFullName("acme/repo//x")).toBeNull();
+  });
+
+  it("rejects a pasted stale-copy suffix that the old guard accepted", () => {
+    expect(splitRepoFullName("owner/repo//stale-copy")).toBeNull();
+  });
+
+  it("rejects any input with more than two segments", () => {
+    expect(splitRepoFullName("a/b/c")).toBeNull();
+    expect(splitRepoFullName("a/b/c/d")).toBeNull();
+  });
+
+  it("rejects fewer than two segments", () => {
+    expect(splitRepoFullName("acme")).toBeNull();
+    expect(splitRepoFullName("")).toBeNull();
+    expect(splitRepoFullName("   ")).toBeNull();
+  });
+
+  it("rejects an empty owner or empty repo segment", () => {
+    expect(splitRepoFullName("/repo")).toBeNull();
+    expect(splitRepoFullName("acme/")).toBeNull();
+    expect(splitRepoFullName("/")).toBeNull();
+  });
+});
+
+describe("splitReviewabilityPr", () => {
+  it("parses owner/repo#number into its parts", () => {
+    expect(splitReviewabilityPr("acme/repo#123")).toEqual({
+      owner: "acme",
+      repo: "repo",
+      number: 123,
+    });
+  });
+
+  it("inherits splitRepoFullName's stricter validation for the repo half", () => {
+    expect(splitReviewabilityPr("acme/repo//stale#123")).toBeNull();
+  });
+
+  it("rejects a missing, zero, negative, or non-integer issue number", () => {
+    expect(splitReviewabilityPr("acme/repo")).toBeNull();
+    expect(splitReviewabilityPr("acme/repo#0")).toBeNull();
+    expect(splitReviewabilityPr("acme/repo#-1")).toBeNull();
+    expect(splitReviewabilityPr("acme/repo#1.5")).toBeNull();
+  });
+});
+
+describe("extractPreviewRepoOptions", () => {
+  it("returns unique, sorted, well-formed repos and drops malformed rows", () => {
+    expect(
+      extractPreviewRepoOptions([
+        { pr: "beta/two#5" },
+        { pr: "alpha/one#1" },
+        { pr: "alpha/one#2" },
+        { pr: "not-a-repo#3" },
+        { pr: "has space/repo#4" },
+      ]),
+    ).toEqual(["alpha/one", "beta/two"]);
+  });
+});
+
+describe("parsePreviewLabels", () => {
+  it("splits on commas, trims, drops blanks, and de-duplicates case-insensitively", () => {
+    expect(parsePreviewLabels(" bug , Bug ,, feature ")).toEqual(["bug", "feature"]);
+  });
+
+  it("caps the result at 50 labels", () => {
+    const many = Array.from({ length: 60 }, (_, index) => `label-${index}`).join(",");
+    expect(parsePreviewLabels(many)).toHaveLength(50);
+  });
+});
+
+describe("parseLinkedIssues", () => {
+  it("parses hash-prefixed and whitespace/comma-separated positive integers, de-duplicated", () => {
+    expect(parseLinkedIssues("#12, 34 12  56")).toEqual([12, 34, 56]);
+  });
+
+  it("drops zero, negative, and non-numeric tokens", () => {
+    expect(parseLinkedIssues("#0, -3, abc, 7")).toEqual([7]);
+  });
+});
+
+describe("findPreviewScenario", () => {
+  it("returns the matching scenario", () => {
+    expect(findPreviewScenario("bot-author").id).toBe("bot-author");
+  });
+
+  it("falls back to the first scenario for an unknown id", () => {
+    expect(findPreviewScenario("nope" as never)).toBe(PREVIEW_SCENARIOS[0]);
+  });
+});
+
+describe("buildSettingsPreviewRequest", () => {
+  const baseForm: PreviewFormState = {
+    repoFullName: "acme/repo",
+    scenarioId: "confirmed-miner",
+    title: "  My PR  ",
+    labels: "bug, feature",
+    linkedIssues: "#1 2",
+    body: "  hello  ",
+  };
+
+  it("assembles the sample from the scenario, trimmed title/body, and parsed labels/issues", () => {
+    expect(buildSettingsPreviewRequest(baseForm)).toEqual({
+      sample: {
+        authorLogin: "sample-miner",
+        authorType: "User",
+        authorAssociation: "CONTRIBUTOR",
+        minerStatus: "confirmed",
+        title: "My PR",
+        labels: ["bug", "feature"],
+        linkedIssues: [1, 2],
+        body: "hello",
+      },
+    });
+  });
+
+  it("defaults a blank title and omits an empty body", () => {
+    const result = buildSettingsPreviewRequest({ ...baseForm, title: "   ", body: "   " });
+    expect(result.sample.title).toBe("Sample pull request");
+    expect(result.sample).not.toHaveProperty("body");
+  });
+});
diff --git a/apps/loopover-ui/src/lib/maintainer-settings-preview.ts b/apps/loopover-ui/src/lib/maintainer-settings-preview.ts
index 628c6e2a2b..ff0201198d 100644
--- a/apps/loopover-ui/src/lib/maintainer-settings-preview.ts
+++ b/apps/loopover-ui/src/lib/maintainer-settings-preview.ts
@@ -116,8 +116,13 @@ export function extractPreviewRepoOptions(reviewability: Array<{ pr: string }>):
 }
 
 export function splitRepoFullName(repoFullName: string): { owner: string; repo: string } | null {
-  const [owner, repo, extra] = repoFullName.trim().split("/");
-  if (!owner || !repo || extra) return null;
+  // Split into exactly two non-empty segments. The old `[owner, repo, extra]` destructuring only
+  // inspected the 3rd segment, so any input whose 3rd `/`-segment was empty ("owner/repo/",
+  // "owner/repo//stale") slipped through as a truncated owner/repo pair (#7783).
+  const parts = repoFullName.trim().split("/");
+  if (parts.length !== 2) return null;
+  const [owner, repo] = parts;
+  if (!owner || !repo) return null;
   return { owner, repo };
 }