diff --git a/plugins/github/server.rpc.test.ts b/plugins/github/server.rpc.test.ts
index 9bf668fb76..742674cb92 100644
--- a/plugins/github/server.rpc.test.ts
+++ b/plugins/github/server.rpc.test.ts
@@ -348,4 +348,21 @@ describe("github plugin RPC behavior", () => {
       },
     });
   });
+  it("warns about an extraRepos entry that cannot track anything", async () => {
+    const host = createFakePluginHost({
+      pluginId: "github",
+      settings: { extraRepos: "acme/widgets, ACME/*" },
+    });
+    await plugin(host.bb);
+
+    // The valid sibling still syncs; the glob contributes no repo.
+    await expect(host.harness.callRpc("refresh")).resolves.toMatchObject({
+      repos: 1,
+    });
+    expect(
+      host.harness.logEntries.filter(
+        (entry) => entry.level === "warn" && entry.message.includes("ACME/*"),
+      ),
+    ).not.toHaveLength(0);
+  });
 });
diff --git a/plugins/github/server.test.ts b/plugins/github/server.test.ts
index cbe21f132e..bad0838f90 100644
--- a/plugins/github/server.test.ts
+++ b/plugins/github/server.test.ts
@@ -6,6 +6,7 @@ import {
   fetchRepoItems,
   githubRpcContract,
   parsePaginatedGhApi,
+  parseExtraRepos,
   validateGithubCliArgs,
 } from "./server";
 
@@ -141,6 +142,25 @@ describe("GitHub RPC contract", () => {
     );
   });
 
+  it("separates trackable extraRepos entries from wildcards and typos", () => {
+    expect(parseExtraRepos("get-bb/bb, owner/other")).toEqual({
+      valid: ["get-bb/bb", "owner/other"],
+      invalid: [],
+    });
+    // A glob parsed to nothing at all, with no warning and no tracked repo.
+    expect(parseExtraRepos("get-bb/*")).toEqual({
+      valid: [],
+      invalid: ["get-bb/*"],
+    });
+    expect(parseExtraRepos("get-bb/bb, get-bb/*, nope")).toEqual({
+      valid: ["get-bb/bb"],
+      invalid: ["get-bb/*", "nope"],
+    });
+    // Blank and separator-only settings are empty, not invalid.
+    expect(parseExtraRepos("")).toEqual({ valid: [], invalid: [] });
+    expect(parseExtraRepos("  ,  ")).toEqual({ valid: [], invalid: [] });
+  });
+
   it("infers parsed handler inputs and frontend results", () => {
     expectTypeOf<
       Parameters<GithubRpcHandlers["createIssue"]>[0]
diff --git a/plugins/github/server.ts b/plugins/github/server.ts
index 4b26ba1563..5d0d6cffdb 100644
--- a/plugins/github/server.ts
+++ b/plugins/github/server.ts
@@ -345,6 +345,25 @@ function isRepoName(value: unknown): value is string {
   return typeof value === "string" && /^[\w.-]+\/[\w.-]+$/.test(value);
 }
 
+/**
+ * Split the extraRepos setting into repository names this plugin can track and
+ * entries it cannot. The setting is an explicit list, so a wildcard such as
+ * "owner/*" is invalid rather than an owner-wide match.
+ */
+export function parseExtraRepos(raw: string): {
+  valid: string[];
+  invalid: string[];
+} {
+  const valid: string[] = [];
+  const invalid: string[] = [];
+  for (const entry of raw.split(/[\s,]+/)) {
+    if (entry.length === 0) continue;
+    if (isRepoName(entry)) valid.push(entry);
+    else invalid.push(entry);
+  }
+  return { valid, invalid };
+}
+
 function run(
   file: string,
   args: string[],
@@ -609,10 +628,17 @@ export default async function plugin(bb: BbPluginApi) {
       );
     }
     const { extraRepos } = await settings.get();
-    for (const raw of extraRepos.split(/[\s,]+/)) {
-      if (isRepoName(raw) && !byRepo.has(raw)) {
-        byRepo.set(raw, { repo: raw, projectId: null });
-      }
+    const extra = parseExtraRepos(extraRepos);
+    for (const raw of extra.valid) {
+      if (!byRepo.has(raw)) byRepo.set(raw, { repo: raw, projectId: null });
+    }
+    // An unusable entry used to be dropped in silence, so a typo or a glob
+    // looked identical to a setting that worked.
+    for (const bad of extra.invalid) {
+      bb.log.warn(
+        `extraRepos entry "${bad}" is not an owner/repo name and tracks nothing. ` +
+          "List each repository explicitly, for example \"owner/repo\".",
+      );
     }
     const repos = [...byRepo.values()];
     repoCache = { repos, fetchedAt: Date.now() };