diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16c601359..508717c71 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -37,6 +37,7 @@
 - Signal: accept UUID-only senders for pairing/allowlists/routing when sourceNumber is missing. (#523) — thanks @neist
 - Agent system prompt: avoid automatic self-updates unless explicitly requested.
 - Onboarding: tighten QuickStart hint copy for configuring later.
+- Onboarding: set Gemini 3 Pro as the default model for Gemini API key auth. (#489) — thanks @jonasjancarik
 - Onboarding: avoid “token expired” for Codex CLI when expiry is heuristic.
 - Onboarding: QuickStart jumps straight into provider selection with Telegram preselected when unset.
 - Onboarding: QuickStart auto-installs the Gateway daemon with Node (no runtime picker).
diff --git a/src/commands/auth-choice.ts b/src/commands/auth-choice.ts
index 9407be5d9..42eba1ad3 100644
--- a/src/commands/auth-choice.ts
+++ b/src/commands/auth-choice.ts
@@ -25,6 +25,10 @@ import {
   isRemoteEnvironment,
   loginAntigravityVpsAware,
 } from "./antigravity-oauth.js";
+import {
+  applyGoogleGeminiModelDefault,
+  GOOGLE_GEMINI_DEFAULT_MODEL,
+} from "./google-gemini-model-default.js";
 import {
   applyAuthProfileConfig,
   applyMinimaxConfig,
@@ -427,6 +431,19 @@ export async function applyAuthChoice(params: {
       provider: "google",
       mode: "api_key",
     });
+    if (params.setDefaultModel) {
+      const applied = applyGoogleGeminiModelDefault(nextConfig);
+      nextConfig = applied.next;
+      if (applied.changed) {
+        await params.prompter.note(
+          `Default model set to ${GOOGLE_GEMINI_DEFAULT_MODEL}`,
+          "Model configured",
+        );
+      }
+    } else {
+      agentModelOverride = GOOGLE_GEMINI_DEFAULT_MODEL;
+      await noteAgentModel(GOOGLE_GEMINI_DEFAULT_MODEL);
+    }
   } else if (params.authChoice === "apiKey") {
     const key = await params.prompter.text({
       message: "Enter Anthropic API key",
diff --git a/src/commands/configure.ts b/src/commands/configure.ts
index 3c747f316..08bf0598a 100644
--- a/src/commands/configure.ts
+++ b/src/commands/configure.ts
@@ -50,6 +50,10 @@ import {
   GATEWAY_DAEMON_RUNTIME_OPTIONS,
   type GatewayDaemonRuntime,
 } from "./daemon-runtime.js";
+import {
+  applyGoogleGeminiModelDefault,
+  GOOGLE_GEMINI_DEFAULT_MODEL,
+} from "./google-gemini-model-default.js";
 import { healthCommand } from "./health.js";
 import {
   applyAuthProfileConfig,
@@ -529,6 +533,14 @@ async function promptAuthConfig(
       provider: "google",
       mode: "api_key",
     });
+    const applied = applyGoogleGeminiModelDefault(next);
+    next = applied.next;
+    if (applied.changed) {
+      note(
+        `Default model set to ${GOOGLE_GEMINI_DEFAULT_MODEL}`,
+        "Model configured",
+      );
+    }
   } else if (authChoice === "apiKey") {
     const key = guardCancel(
       await text({
diff --git a/src/commands/google-gemini-model-default.test.ts b/src/commands/google-gemini-model-default.test.ts
new file mode 100644
index 000000000..9dff42e8c
--- /dev/null
+++ b/src/commands/google-gemini-model-default.test.ts
@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+
+import type { ClawdbotConfig } from "../config/config.js";
+import {
+  applyGoogleGeminiModelDefault,
+  GOOGLE_GEMINI_DEFAULT_MODEL,
+} from "./google-gemini-model-default.js";
+
+describe("applyGoogleGeminiModelDefault", () => {
+  it("sets gemini default when model is unset", () => {
+    const cfg: ClawdbotConfig = { agent: {} };
+    const applied = applyGoogleGeminiModelDefault(cfg);
+    expect(applied.changed).toBe(true);
+    expect(applied.next.agent?.model).toEqual({
+      primary: GOOGLE_GEMINI_DEFAULT_MODEL,
+    });
+  });
+
+  it("overrides existing model", () => {
+    const cfg: ClawdbotConfig = {
+      agent: { model: "anthropic/claude-opus-4-5" },
+    };
+    const applied = applyGoogleGeminiModelDefault(cfg);
+    expect(applied.changed).toBe(true);
+    expect(applied.next.agent?.model).toEqual({
+      primary: GOOGLE_GEMINI_DEFAULT_MODEL,
+    });
+  });
+
+  it("no-ops when already gemini default", () => {
+    const cfg: ClawdbotConfig = {
+      agent: { model: GOOGLE_GEMINI_DEFAULT_MODEL },
+    };
+    const applied = applyGoogleGeminiModelDefault(cfg);
+    expect(applied.changed).toBe(false);
+    expect(applied.next).toEqual(cfg);
+  });
+});
diff --git a/src/commands/google-gemini-model-default.ts b/src/commands/google-gemini-model-default.ts
new file mode 100644
index 000000000..6ae4917db
--- /dev/null
+++ b/src/commands/google-gemini-model-default.ts
@@ -0,0 +1,38 @@
+import type { ClawdbotConfig } from "../config/config.js";
+import type { AgentModelListConfig } from "../config/types.js";
+
+export const GOOGLE_GEMINI_DEFAULT_MODEL = "google/gemini-3-pro-preview";
+
+function resolvePrimaryModel(
+  model?: AgentModelListConfig | string,
+): string | undefined {
+  if (typeof model === "string") return model;
+  if (model && typeof model === "object" && typeof model.primary === "string") {
+    return model.primary;
+  }
+  return undefined;
+}
+
+export function applyGoogleGeminiModelDefault(cfg: ClawdbotConfig): {
+  next: ClawdbotConfig;
+  changed: boolean;
+} {
+  const current = resolvePrimaryModel(cfg.agent?.model)?.trim();
+  if (current === GOOGLE_GEMINI_DEFAULT_MODEL) {
+    return { next: cfg, changed: false };
+  }
+
+  return {
+    next: {
+      ...cfg,
+      agent: {
+        ...cfg.agent,
+        model:
+          cfg.agent?.model && typeof cfg.agent.model === "object"
+            ? { ...cfg.agent.model, primary: GOOGLE_GEMINI_DEFAULT_MODEL }
+            : { primary: GOOGLE_GEMINI_DEFAULT_MODEL },
+      },
+    },
+    changed: true,
+  };
+}
diff --git a/src/commands/onboard-non-interactive.ts b/src/commands/onboard-non-interactive.ts
index 8fbc12e72..51bb6ee84 100644
--- a/src/commands/onboard-non-interactive.ts
+++ b/src/commands/onboard-non-interactive.ts
@@ -23,6 +23,7 @@ import {
   DEFAULT_GATEWAY_DAEMON_RUNTIME,
   isGatewayDaemonRuntime,
 } from "./daemon-runtime.js";
+import { applyGoogleGeminiModelDefault } from "./google-gemini-model-default.js";
 import { healthCommand } from "./health.js";
 import {
   applyAuthProfileConfig,
@@ -133,6 +134,7 @@ export async function runNonInteractiveOnboarding(
       provider: "google",
       mode: "api_key",
     });
+    nextConfig = applyGoogleGeminiModelDefault(nextConfig).next;
   } else if (authChoice === "claude-cli") {
     const store = ensureAuthProfileStore(undefined, {
       allowKeychainPrompt: false,