diff --git a/src/validation/formats.ts b/src/validation/formats.ts
index dff5ad8..f9f9a54 100644
--- a/src/validation/formats.ts
+++ b/src/validation/formats.ts
@@ -3,6 +3,12 @@ import { FormatRegistry } from "@sinclair/typebox";
 /**
  * Registers the string formats this codebase uses with TypeBox.
  *
+ * Import this from any test that validates a schema carrying a `format`
+ * without standing up Elysia. `tests/edge_protocol.test.ts` did not, and so
+ * passed only because some *other* test file in the same run happened to
+ * import Elysia first and register the formats globally - run on its own it
+ * failed, which is the worst way for a contract test to behave.
+ *
  * TypeBox ships no format validators: `format` is a registry lookup, and an
  * *unregistered* format does not pass - it fails. So a schema written with
  * `format: "uuid"` and checked outside Elysia rejects every value, including
@@ -28,6 +34,24 @@ if (!FormatRegistry.Has("uuid")) {
   FormatRegistry.Set("uuid", (value) => UUID.test(value));
 }
 
+if (!FormatRegistry.Has("uri")) {
+  // `PrinterCommand.start_print.url` is the only user, and it carries a
+  // presigned object-store GET. Lenient on purpose: anything the platform
+  // parses as an absolute URL passes. A stricter pattern would have to
+  // anticipate whatever query parameters a signer adds, and rejecting a URL
+  // R2 would have honoured costs a print for no security - the command is
+  // minted by this backend, not submitted by a client.
+  FormatRegistry.Set("uri", (value) => {
+    try {
+      // Rejects a relative reference, which `format: "uri"` is supposed to:
+      // the two-argument form would happily resolve "../x" against a base.
+      return new URL(value).protocol.length > 0;
+    } catch {
+      return false;
+    }
+  });
+}
+
 if (!FormatRegistry.Has("date-time")) {
   // Deliberately lenient: anything `Date.parse` understands. The producers
   // are `new Date().toISOString()` in TypeScript and chrono's RFC 3339 in
diff --git a/tests/edge_protocol.test.ts b/tests/edge_protocol.test.ts
index 4fba01d..367cd23 100644
--- a/tests/edge_protocol.test.ts
+++ b/tests/edge_protocol.test.ts
@@ -1,6 +1,12 @@
 import { describe, expect, it } from "bun:test";
 import { Value } from "@sinclair/typebox/value";
 import { EdgeClientMessageSchema, EdgeServerMessageSchema } from "@continuum/ts-types";
+// Registers `uuid` and `uri`. Not optional: TypeBox treats an unregistered
+// format as a failure, so without this every `start_print` in this file is
+// rejected for its job_id and url. This file used to rely on another test
+// file importing Elysia first, which made it pass in a full run and fail on
+// its own.
+import "../src/validation/formats";
 
 import currentCapture from "./fixtures/gateway_frames.json";
 import legacyCapture from "./fixtures/gateway_frames_legacy_nulls.json";