diff --git a/.changeset/login-source-backed-gateway-model.md b/.changeset/login-source-backed-gateway-model.md
index 247ff0ce5..a83e34f1d 100644
--- a/.changeset/login-source-backed-gateway-model.md
+++ b/.changeset/login-source-backed-gateway-model.md
@@ -2,4 +2,4 @@
 "eve": patch
 ---
 
-`/login` now connects a Vercel account or AI Gateway key to an agent whose `model` is a gateway SDK call (such as `gateway(...)`) without trying to rewrite `agent.ts`. Previously the failed source edit discarded the connection and returned to the connection picker, leaving the agent unusable.
+`/login` now works for agents whose `model` is a gateway SDK call such as `gateway("anthropic/claude-sonnet-5")`. In `eve dev`, a gateway-routed model instance is served through the connection saved by `/login` (Vercel account, AI Gateway key, or project), the same way a string model id is, and `/login` no longer tries to rewrite `agent.ts` for it. Previously the failed source edit sent you back to the connection picker after every sign-in.
diff --git a/packages/eve/src/runtime/agent/resolve-model.test.ts b/packages/eve/src/runtime/agent/resolve-model.test.ts
index 9e14674d0..65e7c07f0 100644
--- a/packages/eve/src/runtime/agent/resolve-model.test.ts
+++ b/packages/eve/src/runtime/agent/resolve-model.test.ts
@@ -1,5 +1,5 @@
 import type { LanguageModel } from "ai";
-import { afterEach, describe, expect, it, vi } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import { ROOT_COMPILED_AGENT_NODE_ID } from "#compiler/manifest.js";
 import type { CompiledModuleMap } from "#compiler/module-map.js";
@@ -72,6 +72,58 @@ describe("dynamic runtime model resolution", () => {
     expect(model.modelId).toBe("eve-mock/dynamic-subagent");
   });
 
+  describe("source-backed models", () => {
+    const source = {
+      logicalPath: "agent.ts",
+      sourceId: "agent-config",
+      sourceKind: "module" as const,
+    };
+    const resolve = (model: LanguageModel) =>
+      resolveRuntimeModelReference(
+        { id: typeof model === "string" ? model : `${model.provider}/${model.modelId}`, source },
+        { moduleMap: createModuleMap({ default: { model } }), nodeId: undefined },
+      );
+
+    beforeEach(() => vi.stubEnv("NODE_ENV", "production"));
+
+    it("serves a gateway SDK instance through the /login connection in eve dev", async () => {
+      vi.stubEnv("EVE_DEV", "1");
+      vi.stubEnv("EVE_MODEL_CONNECTION", "vercel");
+      const authored = createLanguageModel("gateway", "anthropic/claude-sonnet-5");
+
+      const model = await resolve(authored);
+
+      expect(model).not.toBe(authored);
+      if (typeof model === "string") throw new Error("expected a model instance");
+      expect(model.provider).toBe("gateway");
+      expect(model.modelId).toBe("anthropic/claude-sonnet-5");
+    });
+
+    it("returns the authored gateway instance when no connection is active", async () => {
+      vi.stubEnv("EVE_DEV", "1");
+      vi.stubEnv("EVE_MODEL_CONNECTION", "");
+      const authored = createLanguageModel("gateway", "anthropic/claude-sonnet-5");
+
+      expect(await resolve(authored)).toBe(authored);
+    });
+
+    it("returns the authored gateway instance outside eve dev", async () => {
+      vi.stubEnv("EVE_DEV", "");
+      vi.stubEnv("EVE_MODEL_CONNECTION", "vercel");
+      const authored = createLanguageModel("gateway", "anthropic/claude-sonnet-5");
+
+      expect(await resolve(authored)).toBe(authored);
+    });
+
+    it("leaves a direct provider instance untouched", async () => {
+      vi.stubEnv("EVE_DEV", "1");
+      vi.stubEnv("EVE_MODEL_CONNECTION", "vercel");
+      const authored = createLanguageModel("openai.responses", "gpt-5.5");
+
+      expect(await resolve(authored)).toBe(authored);
+    });
+  });
+
   it("loads resolver-only definitions and normalizes explicit metadata", async () => {
     const moduleMap = createModuleMap({
       default: {
diff --git a/packages/eve/src/runtime/agent/resolve-model.ts b/packages/eve/src/runtime/agent/resolve-model.ts
index 356eb0a92..21b5a6a70 100644
--- a/packages/eve/src/runtime/agent/resolve-model.ts
+++ b/packages/eve/src/runtime/agent/resolve-model.ts
@@ -110,7 +110,23 @@ async function loadSourceBackedRuntimeModelReference(
     );
   }
 
-  return model;
+  return withLocalGatewayConnection(model);
+}
+
+/**
+ * A gateway-routed SDK instance (`gateway("openai/gpt-5.6")`) authenticates
+ * from `AI_GATEWAY_API_KEY`/`VERCEL_OIDC_TOKEN` and never sees the connection
+ * `/login` saved. While such a connection is active, serve the same model id
+ * through it, as a string model would be. Outside `eve dev` the authored
+ * instance is returned untouched.
+ */
+function withLocalGatewayConnection(model: LanguageModel): LanguageModel {
+  if (typeof model === "string") return model;
+  if (typeof model.provider !== "string" || model.provider.split(".")[0] !== "gateway") {
+    return model;
+  }
+  if (typeof model.modelId !== "string" || model.modelId === "") return model;
+  return localGatewayModel(model.modelId) ?? model;
 }
 
 function isSourceBackedRuntimeModelReference(