diff --git a/packages/das/src/api/admin.controller.ts b/packages/das/src/api/admin.controller.ts
index fb6437b..0766f55 100644
--- a/packages/das/src/api/admin.controller.ts
+++ b/packages/das/src/api/admin.controller.ts
@@ -14,6 +14,7 @@ import { ApiTags, ApiOperation, ApiSecurity, ApiBody } from "@nestjs/swagger";
 import { RequireApiKeyGuard } from "./require-api-key.guard";
 import { Repo } from "../entities";
 import { FETCH_QUEUE, FETCH_JOBS } from "../queue/constants";
+import { validateRepoFullName } from "../utils/repo-full-name";
 
 interface BackfillBody {
   repoFullName: string;
@@ -24,18 +25,6 @@ interface RegisterBody {
   repoFullName: string;
 }
 
-// GitHub owner/repo pattern: alphanum + `.`, `_`, `-`, length reasonable.
-const REPO_FULL_NAME_PATTERN = /^[\w.-]{1,100}\/[\w.-]{1,100}$/;
-
-function validateRepoFullName(value: unknown): string {
-  if (typeof value !== "string" || !REPO_FULL_NAME_PATTERN.test(value)) {
-    throw new BadRequestException(
-      'repoFullName must match "owner/repo" (alphanumerics, dot, dash, underscore)',
-    );
-  }
-  return value;
-}
-
 function validateDays(value: unknown): number | undefined {
   if (value === undefined || value === null) return undefined;
   if (typeof value !== "number" || !Number.isFinite(value) || value <= 0) {
diff --git a/packages/das/src/utils/repo-full-name.ts b/packages/das/src/utils/repo-full-name.ts
new file mode 100644
index 0000000..9805a8f
--- /dev/null
+++ b/packages/das/src/utils/repo-full-name.ts
@@ -0,0 +1,18 @@
+import { BadRequestException } from "@nestjs/common";
+
+/** GitHub owner/repo pattern: alphanum + `.`, `_`, `-`, length reasonable. */
+export const REPO_FULL_NAME_PATTERN = /^[\w.-]{1,100}\/[\w.-]{1,100}$/;
+
+/** GitHub treats repository identity as case-insensitive; canonical form is lowercase. */
+export function normalizeRepoFullName(value: string): string {
+  return value.toLowerCase();
+}
+
+export function validateRepoFullName(value: unknown): string {
+  if (typeof value !== "string" || !REPO_FULL_NAME_PATTERN.test(value)) {
+    throw new BadRequestException(
+      'repoFullName must match "owner/repo" (alphanumerics, dot, dash, underscore)',
+    );
+  }
+  return normalizeRepoFullName(value);
+}
diff --git a/packages/das/src/webhook/handlers/installation.handler.ts b/packages/das/src/webhook/handlers/installation.handler.ts
index 7eaf630..5cf2c19 100644
--- a/packages/das/src/webhook/handlers/installation.handler.ts
+++ b/packages/das/src/webhook/handlers/installation.handler.ts
@@ -3,6 +3,7 @@ import { Injectable, Logger } from "@nestjs/common";
 import { InjectRepository } from "@nestjs/typeorm";
 import { Repository } from "typeorm";
 import { Repo } from "../../entities";
+import { normalizeRepoFullName } from "../../utils/repo-full-name";
 
 @Injectable()
 export class InstallationHandler {
@@ -38,6 +39,7 @@ export class InstallationHandler {
       payload.repositories ?? payload.repositories_added ?? [];
 
     for (const repo of repos) {
+      const repoFullName = normalizeRepoFullName(String(repo.full_name));
       // Atomic upsert: insert with addedAt on first encounter; on conflict only
       // update installationId so addedAt is never overwritten on re-fires.
       await this.repoRepo
@@ -45,23 +47,35 @@ export class InstallationHandler {
         .insert()
         .into(Repo)
         .values({
-          repoFullName: repo.full_name,
+          repoFullName,
           installationId: String(installationId),
           addedAt: new Date().toISOString(),
         })
         .orUpdate(["installationId"], ["repoFullName"])
         .execute();
-      this.logger.log(`Tracking repo: ${repo.full_name}`);
+      this.logger.log(`Tracking repo: ${repoFullName}`);
     }
 
     // installation_repositories.removed — soft clear, preserve historical data.
+    // Match case-insensitively so rows stored via admin API (lowercase) or legacy
+    // webhook casing (GitHub's raw Owner/Repo) are all cleared (#120).
     const removed: any[] = payload.repositories_removed ?? [];
     for (const repo of removed) {
-      await this.repoRepo.update(repo.full_name, {
-        installationId: null,
-        registered: false,
-      });
-      this.logger.log(`Stopped tracking repo: ${repo.full_name}`);
+      const repoFullName = normalizeRepoFullName(String(repo.full_name));
+      const result = await this.repoRepo
+        .createQueryBuilder()
+        .update()
+        .set({ installationId: null, registered: false })
+        .where("LOWER(repo_full_name) = :repoFullName", { repoFullName })
+        .execute();
+
+      if (!result.affected) {
+        this.logger.warn(
+          `No repo row matched removal for ${repo.full_name} (canonical: ${repoFullName})`,
+        );
+      } else {
+        this.logger.log(`Stopped tracking repo: ${repoFullName}`);
+      }
     }
   }
 }