diff --git a/src/github/pr-actions.ts b/src/github/pr-actions.ts
index eb1a44465f..c3055d22a0 100644
--- a/src/github/pr-actions.ts
+++ b/src/github/pr-actions.ts
@@ -120,7 +120,8 @@ export async function getLastCloserLogin(env: Env, installationId: number, repoF
     const token = await createInstallationToken(env, installationId);
     const octokit = new Octokit({ auth: token });
     let lastCloser: string | null = null;
-    for (let page = 1; ; page += 1) {
+    // Cap at 10 pages (1 000 events) — enough for any real PR timeline without risking API rate exhaustion.
+    for (let page = 1; page <= 10; page += 1) {
       // issue-events are returned oldest-first; walk every page so the final `closed` entry is truly the latest.
       const response = await octokit.request("GET /repos/{owner}/{repo}/issues/{issue_number}/events", { owner, repo, issue_number: issueNumber, per_page: 100, page });
       const events = response.data as Array<{ event?: string; actor?: { login?: string | null } | null }>;
@@ -129,6 +130,7 @@ export async function getLastCloserLogin(env: Env, installationId: number, repoF
       }
       if (events.length < 100) return lastCloser;
     }
+    return lastCloser;
   } catch {
     return null;
   }
diff --git a/test/unit/github-pr-actions.test.ts b/test/unit/github-pr-actions.test.ts
index 8f31010e2c..e91514eb0e 100644
--- a/test/unit/github-pr-actions.test.ts
+++ b/test/unit/github-pr-actions.test.ts
@@ -127,6 +127,28 @@ describe("GitHub PR action primitives (#778)", () => {
     });
     await expect(getLastCloserLogin(envWithKey(), 123, "owner/repo", 19)).resolves.toBeNull();
   });
+
+  it("returns the best-known closer when the 10-page event cap is reached (page-cap exit path)", async () => {
+    const fetchedPages: number[] = [];
+    vi.stubGlobal("fetch", async (input: RequestInfo | URL) => {
+      const url = input.toString();
+      if (url.includes("/access_tokens")) return Response.json({ token: "t" });
+      if (url.includes("/issues/20/events")) {
+        const page = Number(new URL(url).searchParams.get("page") ?? "1");
+        fetchedPages.push(page);
+        // Page 5 contains the close event; all pages return exactly 100 entries so the loop never exits early.
+        const events = Array.from({ length: 100 }, (_, i) =>
+          page === 5 && i === 50 ? { event: "closed", actor: { login: "capped-closer" } } : { event: "labeled" },
+        );
+        return Response.json(events);
+      }
+      return new Response("unexpected", { status: 500 });
+    });
+    await expect(getLastCloserLogin(envWithKey(), 123, "owner/repo", 20)).resolves.toBe("capped-closer");
+    // Loop ran pages 1–10 and then exited via the cap, never requesting page 11.
+    expect(fetchedPages).toHaveLength(10);
+    expect(fetchedPages).not.toContain(11);
+  });
 });
 
 function generateRsaPrivateKeyPem(): string {
diff --git a/test/unit/scoring.test.ts b/test/unit/scoring.test.ts
index 44bec497e4..e532b42aae 100644
--- a/test/unit/scoring.test.ts
+++ b/test/unit/scoring.test.ts
@@ -531,6 +531,63 @@ NOVELTY_BONUS_SCALAR = 3
     expect(bootstrap.warnings.join(" ")).toMatch(/fetch failed/i);
   });
 
+  it("does not freeze a prior fallback snapshot — bootstraps fresh defaults instead", async () => {
+    const env = createTestEnv();
+    vi.stubGlobal("fetch", async () => new Response("gone", { status: 410 }));
+    // First refresh → fallback stored (no verified last-good yet).
+    const first = await refreshScoringModelSnapshot(env);
+    expect(first.sourceKind).toBe("fallback");
+    // Second refresh — constants still fail; lastGood exists but sourceKind === "fallback"
+    // → the guard (lastGood && sourceKind !== "fallback") is false → must NOT freeze → new fallback.
+    const second = await refreshScoringModelSnapshot(env);
+    expect(second.sourceKind).toBe("fallback");
+    expect(second.id).not.toBe(first.id);
+    expect(second.warnings.join(" ")).not.toMatch(/froze the last-good/i);
+  });
+
+  it("falls back to the mutable ref when the upstream SHA lookup throws (fetchUpstreamRefSha catch path)", async () => {
+    const env = createTestEnv({ GITTENSOR_UPSTREAM_REPO: "custom/upstream", GITTENSOR_UPSTREAM_REF: "test" });
+    vi.stubGlobal("fetch", async (input: RequestInfo | URL) => {
+      const url = input.toString();
+      if (url.includes("api.github.com") && url.includes("/commits/")) throw new Error("network failure");
+      if (url.includes("constants.py")) return new Response("MERGED_PR_BASE_SCORE = 25\n");
+      if (url.includes("programming_languages.json")) return Response.json({});
+      return new Response("not found", { status: 404 });
+    });
+    const snapshot = await refreshScoringModelSnapshot(env);
+    expect(snapshot.sourceUrl).toContain("/test/gittensor/constants.py");
+    expect((snapshot.payload as Record<string, unknown>).upstreamSourceSha).toBeUndefined();
+    expect(snapshot.sourceKind).toBe("raw-github");
+  });
+
+  it("falls back to the mutable ref when the SHA endpoint returns a non-string sha", async () => {
+    const env = createTestEnv({ GITTENSOR_UPSTREAM_REPO: "custom/upstream", GITTENSOR_UPSTREAM_REF: "test" });
+    vi.stubGlobal("fetch", async (input: RequestInfo | URL) => {
+      const url = input.toString();
+      if (url.includes("api.github.com") && url.includes("/commits/")) return Response.json({ sha: 42 });
+      if (url.includes("constants.py")) return new Response("MERGED_PR_BASE_SCORE = 25\n");
+      if (url.includes("programming_languages.json")) return Response.json({});
+      return new Response("not found", { status: 404 });
+    });
+    const snapshot = await refreshScoringModelSnapshot(env);
+    expect(snapshot.sourceUrl).toContain("/test/gittensor/constants.py");
+    expect((snapshot.payload as Record<string, unknown>).upstreamSourceSha).toBeUndefined();
+  });
+
+  it("falls back to the mutable ref when the SHA endpoint returns an empty sha string", async () => {
+    const env = createTestEnv({ GITTENSOR_UPSTREAM_REPO: "custom/upstream", GITTENSOR_UPSTREAM_REF: "test" });
+    vi.stubGlobal("fetch", async (input: RequestInfo | URL) => {
+      const url = input.toString();
+      if (url.includes("api.github.com") && url.includes("/commits/")) return Response.json({ sha: "" });
+      if (url.includes("constants.py")) return new Response("MERGED_PR_BASE_SCORE = 25\n");
+      if (url.includes("programming_languages.json")) return Response.json({});
+      return new Response("not found", { status: 404 });
+    });
+    const snapshot = await refreshScoringModelSnapshot(env);
+    expect(snapshot.sourceUrl).toContain("/test/gittensor/constants.py");
+    expect((snapshot.payload as Record<string, unknown>).upstreamSourceSha).toBeUndefined();
+  });
+
   it("uses saturation math as the active private preview model", () => {
     const saturationSnapshot: ScoringModelSnapshotRecord = {
       ...snapshot,