Document gemini 3 thinking levels

documentation/docs/getting-started/providers.md

@@ -29,7 +29,7 @@ goose is compatible with a wide range of LLM providers, allowing you to choose a
 | [ChatGPT Codex](https://chatgpt.com/codex) | Access GPT-5 Codex models optimized for code generation and understanding. **Requires a ChatGPT Plus/Pro subscription.** | No manual key. Uses browser-based OAuth authentication for both CLI and Desktop. |
 | [Databricks](https://www.databricks.com/)                                   | Unified data analytics and AI platform for building and deploying models.                                                                                                                                                 | `DATABRICKS_HOST`, `DATABRICKS_TOKEN` |
 | [Docker Model Runner](https://docs.docker.com/ai/model-runner/)                             | Local models running in Docker Desktop or Docker CE with OpenAI-compatible API endpoints. **Because this provider runs locally, you must first [download a model](#local-llms).**                     | `OPENAI_HOST`, `OPENAI_BASE_PATH`   |
-| [Gemini](https://ai.google.dev/gemini-api/docs)                             | Advanced LLMs by Google with multimodal capabilities (text, images).                                                                                                                                                      | `GOOGLE_API_KEY`                                                                                                                                                                    |
+| [Gemini](https://ai.google.dev/gemini-api/docs)                             | Advanced LLMs by Google with multimodal capabilities (text, images). Gemini 3 models support configurable [thinking levels](#gemini-3-thinking-levels).                                                                                                | `GOOGLE_API_KEY`, `GEMINI3_THINKING_LEVEL` (optional)                                                                                                                              |
 | [GCP Vertex AI](https://cloud.google.com/vertex-ai)                         | Google Cloud's Vertex AI platform, supporting Gemini and Claude models. **Credentials must be [configured in advance](https://cloud.google.com/vertex-ai/docs/authentication).** Filters for allowed models by organization policy (if configured). | `GCP_PROJECT_ID`, `GCP_LOCATION` and optionally `GCP_MAX_RATE_LIMIT_RETRIES` (5), `GCP_MAX_OVERLOADED_RETRIES` (5), `GCP_INITIAL_RETRY_INTERVAL_MS` (5000), `GCP_BACKOFF_MULTIPLIER` (2.0), `GCP_MAX_RETRY_INTERVAL_MS` (320_000). |
 | [GitHub Copilot](https://docs.github.com/en/copilot/using-github-copilot/ai-models) | Access to AI models from OpenAI, Anthropic, Google, and other providers through GitHub's Copilot infrastructure. **GitHub account with Copilot access required.** | No manual key. Uses [device flow authentication](#github-copilot-authentication) for both CLI and Desktop. |
 | [Groq](https://groq.com/)                                                   | High-performance inference hardware and tools for LLMs.                                                                                                                                                                   | `GROQ_API_KEY`                                                                                                                                                                      |
@@ -1150,6 +1150,37 @@ Beyond single-model setups, goose supports [multi-model configurations](/docs/gu
 - **Lead/Worker Model** - Automatic switching between a lead model for initial turns and a worker model for execution tasks
 - **Planning Mode** - Manual planning phase using a dedicated model to create detailed project breakdowns before execution
 
+## Gemini 3 Thinking Levels
+
+Gemini 3 models support configurable thinking levels to balance response latency and reasoning depth:
+- **Low** (default) - Faster responses, lighter reasoning
+- **High** - Deeper reasoning, higher latency
+
+<Tabs groupId="interface">
+  <TabItem value="ui" label="goose Desktop" default>
+    When selecting a Gemini 3 model, a "Thinking Level" dropdown appears automatically. Select your preference and the setting persists across sessions.
+  </TabItem>
+
+  <TabItem value="cli" label="goose CLI">
+    **Interactive configuration:**
+
+    When you run `goose configure` and select a Gemini 3 model, you'll be prompted to choose a thinking level:
+
+    ```
+    ◆  Select thinking level for Gemini 3:
+    │  ● Low - Better latency, lighter reasoning
+    │  ○ High - Deeper reasoning, higher latency
+    ```
+  </TabItem>
+</Tabs>
+
+:::info Priority Order
+The thinking level is determined in this order (highest to lowest priority):
+1. `request_params.thinking_level` in model configuration (via `GOOSE_PREDEFINED_MODELS`)
+2. `GEMINI3_THINKING_LEVEL` environment variable
+3. Default value: `low`
+:::
+
 ---
 
 If you have any questions or need help with a specific provider, feel free to reach out to us on [Discord](https://discord.gg/goose-oss) or on the [goose repo](https://github.com/block/goose).

documentation/docs/guides/environment-variables.md

@@ -45,6 +45,7 @@ These variables are needed when using custom endpoints, enterprise deployments,
 | `GOOSE_PROVIDER__TYPE` | The specific type/implementation of the provider | [See available providers](/docs/getting-started/providers#available-providers) | Derived from GOOSE_PROVIDER |
 | `GOOSE_PROVIDER__HOST` | Custom API endpoint for the provider | URL (e.g., "https://api.openai.com") | Provider-specific default |
 | `GOOSE_PROVIDER__API_KEY` | Authentication key for the provider | API key string | None |
+| `GEMINI3_THINKING_LEVEL` | Sets the [thinking level](/docs/getting-started/providers#gemini-3-thinking-levels) for Gemini 3 models globally | `low`, `high` | `low` |
 
 **Examples**
 
@@ -116,6 +117,15 @@ export GOOSE_PREDEFINED_MODELS='[
     "context_limit": 500000
   }
 ]'
+
+# Gemini 3 with high thinking level
+export GOOSE_PREDEFINED_MODELS='[
+  {
+    "name": "gemini-3-pro",
+    "provider": "google",
+    "request_params": {"thinking_level": "high"}
+  }
+]'
 ```
 
 Custom context limits and request parameters are applied when the model is used. Custom context limits are displayed in goose CLI's [token usage indicator](/docs/guides/sessions/smart-context-management#token-usage).