diff --git a/packages/server/package.json b/packages/server/package.json
index bc74e1f..469be4a 100644
--- a/packages/server/package.json
+++ b/packages/server/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@relayauth/server",
-  "version": "0.2.23",
+  "version": "0.2.24",
   "type": "module",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/packages/server/src/__tests__/create-identity.test.ts b/packages/server/src/__tests__/create-identity.test.ts
index 295da1d..e877c7e 100644
--- a/packages/server/src/__tests__/create-identity.test.ts
+++ b/packages/server/src/__tests__/create-identity.test.ts
@@ -3,6 +3,7 @@ import crypto from "node:crypto";
 import test from "node:test";
 import type { AgentIdentity, CreateIdentityInput, RelayAuthTokenClaims } from "@relayauth/types";
 import { FixedWindowRateLimiter, RateLimitExceededError } from "../lib/rate-limit.js";
+import { StorageCapacityExhaustedError } from "../lib/storage-retry.js";
 import type { IdentityBudget, StoredIdentity } from "../storage/identity-types.js";
 import {
   assertJsonResponse,
@@ -398,3 +399,37 @@ test("the global error handler preserves rate-limit errors as 429 responses", as
   assert.equal(response.headers.get("Retry-After"), "60");
   assert.equal(response.headers.get("RateLimit-Remaining"), "0");
 });
+
+test("POST /v1/identities returns 503 with capacity envelope when storage.identities.create throws StorageCapacityExhaustedError", async () => {
+  // Verifies that StorageCapacityExhaustedError thrown from storage.identities.create()
+  // propagates correctly: the route catch block re-throws it (not swallowed as 500),
+  // and app.onError handles it via storageCapacityResponse → 503 with Retry-After.
+  // This is the server-side assertion that the 503 route mapping fix is correct.
+  const storage = createTestStorage();
+  storage.identities.create = async () => {
+    throw new StorageCapacityExhaustedError("post-auth mint capacity exhausted (status 429)");
+  };
+  const app = createTestApp({}, { storage });
+
+  const response = await app.request(
+    createTestRequest(
+      "POST",
+      "/v1/identities",
+      { name: "capacity-probe", sponsorId: "user_sponsor_1" },
+      { Authorization: `Bearer ${createAuthToken()}` },
+    ),
+    undefined,
+    app.bindings,
+  );
+
+  const body = await assertJsonResponse<{
+    code?: string;
+    retryable?: boolean;
+    retryAfterMs?: number;
+    requestId?: string;
+  }>(response, 503);
+  assert.equal(body.code, "storage_capacity_exhausted", "capacity envelope code");
+  assert.equal(body.retryable, true, "capacity envelope must be retryable");
+  assert.ok(response.headers.get("Retry-After"), "Retry-After header must be present");
+  assert.equal(response.headers.get("Cache-Control"), "no-store", "Cache-Control must be no-store");
+});
diff --git a/packages/server/src/routes/identities.ts b/packages/server/src/routes/identities.ts
index 624afee..9282a2f 100644
--- a/packages/server/src/routes/identities.ts
+++ b/packages/server/src/routes/identities.ts
@@ -11,6 +11,7 @@ import type { AppEnv } from "../env.js";
 import { authenticateAndAuthorizeFromContext, authenticateBearerOrApiKey, authorizeClaims, decodeBase64UrlJson } from "../lib/auth.js";
 import { emitObserverEvent, now as observerNow } from "../lib/events.js";
 import {
+  isStorageCapacityExhausted,
   isTransientStorageOverload,
   isStorageOverloadedError,
   StorageOverloadedError,
@@ -502,6 +503,10 @@ identities.post("/", async (c) => {
     });
     return c.json(createdIdentity, 201);
   } catch (error) {
+    if (isStorageCapacityExhausted(error)) {
+      throw error;
+    }
+
     if (isStorageOverloadedError(error)) {
       return storageOverloadResponse(c, error);
     }