diff --git a/packages/das/src/api/repos/repos.controller.ts b/packages/das/src/api/repos/repos.controller.ts
index 98c001c..6f173ad 100644
--- a/packages/das/src/api/repos/repos.controller.ts
+++ b/packages/das/src/api/repos/repos.controller.ts
@@ -24,4 +24,23 @@ export class ReposController {
   ): Promise<unknown> {
     return this.repos.getMaintainers(owner, repo);
   }
+
+  @Get(":owner/:repo/installation")
+  @ApiOperation({
+    summary: "GitHub App installation status for a repo",
+    description:
+      "Returns whether the Gittensor Mirror GitHub App is installed on the " +
+      "repo (installation_id present), independent of whether the repo is " +
+      "registered. The registration UI uses this to verify the install step " +
+      "before a repo is registered. An unknown repo returns installed=false, " +
+      "not a 404.",
+  })
+  @ApiParam({ name: "owner", description: "Repository owner (org or user)" })
+  @ApiParam({ name: "repo", description: "Repository name" })
+  async getInstallationStatus(
+    @Param("owner") owner: string,
+    @Param("repo") repo: string,
+  ): Promise<unknown> {
+    return this.repos.getInstallationStatus(owner, repo);
+  }
 }
diff --git a/packages/das/src/api/repos/repos.service.ts b/packages/das/src/api/repos/repos.service.ts
index a16e496..d2a4f9d 100644
--- a/packages/das/src/api/repos/repos.service.ts
+++ b/packages/das/src/api/repos/repos.service.ts
@@ -1,10 +1,16 @@
 /* eslint-disable @typescript-eslint/no-unsafe-return, @typescript-eslint/no-unsafe-assignment */
 import { Injectable } from "@nestjs/common";
-import { DataSource } from "typeorm";
+import { InjectRepository } from "@nestjs/typeorm";
+import { DataSource, IsNull, Not, Raw, Repository } from "typeorm";
+import { Repo } from "../../entities";
 
 @Injectable()
 export class ReposService {
-  constructor(private readonly dataSource: DataSource) {}
+  constructor(
+    private readonly dataSource: DataSource,
+    @InjectRepository(Repo)
+    private readonly repoRepo: Repository<Repo>,
+  ) {}
 
   async getMaintainers(
     owner: string,
@@ -38,4 +44,26 @@ export class ReposService {
       maintainers: rows,
     };
   }
+
+  async getInstallationStatus(
+    owner: string,
+    repo: string,
+  ): Promise<{ repo_full_name: string; installed: boolean }> {
+    const repoFullName = `${owner}/${repo}`;
+
+    // Case-insensitive match (#120); installed regardless of `registered`.
+    const count = await this.repoRepo.count({
+      where: {
+        repoFullName: Raw((alias) => `LOWER(${alias}) = LOWER(:repoFullName)`, {
+          repoFullName,
+        }),
+        installationId: Not(IsNull()),
+      },
+    });
+
+    return {
+      repo_full_name: repoFullName.toLowerCase(),
+      installed: count > 0,
+    };
+  }
 }