diff --git a/.changeset/oauth-dcr-application-type.md b/.changeset/oauth-dcr-application-type.md
new file mode 100644
index 000000000..5581d2601
--- /dev/null
+++ b/.changeset/oauth-dcr-application-type.md
@@ -0,0 +1,9 @@
+---
+"executor": patch
+---
+
+**Fix: declare the OAuth application type during dynamic client registration**
+
+Dynamic OAuth registrations now identify HTTPS callbacks as web applications
+and loopback HTTP callbacks as native applications. This lets strict OAuth
+servers validate Executor's redirect URI against the correct client type.
diff --git a/packages/core/sdk/src/oauth-register-dynamic.test.ts b/packages/core/sdk/src/oauth-register-dynamic.test.ts
index 266c7cc4d..182c031c1 100644
--- a/packages/core/sdk/src/oauth-register-dynamic.test.ts
+++ b/packages/core/sdk/src/oauth-register-dynamic.test.ts
@@ -145,6 +145,7 @@ describe("oauth.registerDynamicClient", () => {
         expect(registerRequest!.body).toContain(FLOW_REDIRECT_URI);
         expect(registerRequest!.body).toContain("authorization_code");
         expect(registerRequest!.body).toContain("refresh_token");
+        expect(registerRequest!.body).toContain('"application_type":"web"');
         const authorizationRequest = requests.find(
           (r) => r.path === "/authorize" && r.method === "GET",
         );
@@ -160,6 +161,39 @@ describe("oauth.registerDynamicClient", () => {
     ),
   );
 
+  it.effect("registers loopback callbacks as native applications", () =>
+    Effect.scoped(
+      Effect.gen(function* () {
+        const server = yield* serveOAuthTestServer({ scopes: ["read"] });
+        const { executor } = yield* makeTestWorkspaceHarness({ plugins });
+        yield* executor.acme.seed();
+        const probe = yield* executor.oauth.probe({ url: server.mcpResourceUrl });
+
+        yield* executor.oauth.registerDynamicClient({
+          owner: "org",
+          slug: CLIENT,
+          issuer: probe.issuer,
+          registrationEndpoint: probe.registrationEndpoint!,
+          authorizationUrl: probe.authorizationUrl,
+          tokenUrl: probe.tokenUrl,
+          resource: probe.resource,
+          scopes: ["read"],
+          tokenEndpointAuthMethodsSupported: probe.tokenEndpointAuthMethodsSupported,
+          clientName: "Acme DCR",
+          redirectUri: "http://127.0.0.1:5394/api/oauth/callback",
+          originIntegration: INTEG,
+        });
+
+        const requests = yield* server.requests;
+        const registerRequest = requests.find(
+          (request) => request.path === "/register" && request.method === "POST",
+        );
+        expect(registerRequest).toBeDefined();
+        expect(registerRequest!.body).toContain('"application_type":"native"');
+      }),
+    ),
+  );
+
   it.effect("reuses an existing DCR client for the same owner and authorization server", () =>
     Effect.scoped(
       Effect.gen(function* () {
diff --git a/packages/core/sdk/src/oauth-service.ts b/packages/core/sdk/src/oauth-service.ts
index 742cf65ad..f7956b4ed 100644
--- a/packages/core/sdk/src/oauth-service.ts
+++ b/packages/core/sdk/src/oauth-service.ts
@@ -897,6 +897,7 @@ export const makeOAuthService = (deps: OAuthServiceDeps): OAuthService => {
             grant_types: ["authorization_code", "refresh_token"],
             response_types: ["code"],
             token_endpoint_auth_method: authMethod,
+            application_type: isLoopbackHttpUrl(flowRedirectUri) ? "native" : "web",
             scope: input.scopes.length > 0 ? input.scopes.join(" ") : undefined,
           },
         },