sourcebot-dev · brendan-kellam · Feb 2, 2026 · Jan 28, 2026 · Feb 1, 2026 · Feb 1, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,12 +7,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- Added `/api/chat/blocking` endpoint that creates a blocking Ask thread, used by the MCP server. [#814](https://github.com/sourcebot-dev/sourcebot/pull/814)
+- Added `/api/models` endpoint to list configured language models. [#814](https://github.com/sourcebot-dev/sourcebot/pull/814)
+- Added additional telemetry for api requests. [#835](https://github.com/sourcebot-dev/sourcebot/pull/835)
+
 ### Fixed
 - Fixed issue where files with a comma would not render correctly in file tree. [#831](https://github.com/sourcebot-dev/sourcebot/pull/831)
 
 ### Changed
 - Changed `/api/source` api to support fetching source code for any revision, not just revisions that are indexed by zoekt. [#829](https://github.com/sourcebot-dev/sourcebot/pull/829)
-- Added additional telemetry for api requests. [#835](https://github.com/sourcebot-dev/sourcebot/pull/835)
+- Adjusted prompts and tools for Ask agent. [#814](https://github.com/sourcebot-dev/sourcebot/pull/814)
 
 ## [4.10.20] - 2026-01-28
 

diff --git a/docs/docs/features/mcp-server.mdx b/docs/docs/features/mcp-server.mdx
@@ -147,32 +147,84 @@ The [Model Context Protocol](https://modelcontextprotocol.io/introduction) (MCP)
 
 ### `search_code`
 
-Fetches code that matches the provided regex pattern in `query`.
+Searches for code that matches the provided search query as a substring by default, or as a regular expression if `useRegex` is true.
 
 Parameters:
-| Name                  | Required | Description                                                                                                                       |
-|:----------------------|:---------|:----------------------------------------------------------------------------------------------------------------------------------|
-| `query`               | yes      | Regex pattern to search for. Escape special characters and spaces with a single backslash (e.g., 'console\.log', 'console\ log'). |
-| `filterByRepoIds`     | no       | Restrict search to specific repository IDs (from 'list_repos'). Leave empty to search all.                                        |
-| `filterByLanguages`   | no       | Restrict search to specific languages (GitHub linguist format, e.g., Python, JavaScript).                                         |
-| `caseSensitive`       | no       | Case sensitive search (default: false).                                                                                           |
-| `includeCodeSnippets` | no       | Include code snippets in results (default: false).                                                                                |
-| `maxTokens`           | no       | Max tokens to return (default: env.DEFAULT_MINIMUM_TOKENS).                                                                       |
+| Name                  | Required | Description                                                                                                          |
+|:----------------------|:---------|:---------------------------------------------------------------------------------------------------------------------|
+| `query`               | yes      | The search pattern to match against code contents. Do not escape quotes in your query.                               |
+| `useRegex`            | no       | Whether to use regular expression matching. When false, substring matching is used (default: false).                 |
+| `filterByRepos`       | no       | Scope the search to specific repositories.                                                                           |
+| `filterByLanguages`   | no       | Scope the search to specific languages.                                                                              |
+| `filterByFilepaths`   | no       | Scope the search to specific filepaths.                                                                              |
+| `caseSensitive`       | no       | Whether the search should be case sensitive (default: false).                                                        |
+| `includeCodeSnippets` | no       | Whether to include code snippets in the response (default: false).                                                   |
+| `ref`                 | no       | Commit SHA, branch or tag name to search on. If not provided, defaults to the default branch.                        |
+| `maxTokens`           | no       | The maximum number of tokens to return (default: 10000).                                                             |
 
 
 ### `list_repos`
 
-Lists all repositories indexed by Sourcebot.
+Lists repositories indexed by Sourcebot with optional filtering and pagination.
 
-### `get_file_source`
+Parameters:
+| Name        | Required | Description                                                                     |
+|:------------|:---------|:--------------------------------------------------------------------------------|
+| `query`     | no       | Filter repositories by name (case-insensitive).                                 |
+| `page`      | no       | Page number for pagination (min 1, default: 1).                                 |
+| `perPage`   | no       | Results per page for pagination (min 1, max 100, default: 30).                  |
+| `sort`      | no       | Sort repositories by 'name' or 'pushed' (most recent commit). Default: 'name'. |
+| `direction` | no       | Sort direction: 'asc' or 'desc' (default: 'asc').                               |
+
+
+### `read_file`
+
+Reads the source code for a given file.
+
+Parameters:
+| Name   | Required | Description                                                                                            |
+|:-------|:---------|:-------------------------------------------------------------------------------------------------------|
+| `repo` | yes      | The repository name.                                                                                   |
+| `path` | yes      | The path to the file.                                                                                  |
+| `ref`  | no       | Commit SHA, branch or tag name to fetch the source code for. If not provided, uses the default branch. |
+
+
+### `list_commits`
+
+Get a list of commits for a given repository.
+
+Parameters:
+| Name      | Required | Description                                                                                                            |
+|:----------|:---------|:-----------------------------------------------------------------------------------------------------------------------|
+| `repo`    | yes      | The name of the repository to list commits for.                                                                        |
+| `query`   | no       | Search query to filter commits by message content (case-insensitive).                                                  |
+| `since`   | no       | Show commits more recent than this date. Supports ISO 8601 (e.g., '2024-01-01') or relative formats (e.g., '30 days ago'). |
+| `until`   | no       | Show commits older than this date. Supports ISO 8601 (e.g., '2024-12-31') or relative formats (e.g., 'yesterday').     |
+| `author`  | no       | Filter commits by author name or email (case-insensitive).                                                             |
+| `ref`     | no       | Commit SHA, branch or tag name to list commits of. If not provided, uses the default branch.                           |
+| `page`    | no       | Page number for pagination (min 1, default: 1).                                                                        |
+| `perPage` | no       | Results per page for pagination (min 1, max 100, default: 50).                                                         |
+
+
+### `list_language_models`
+
+Lists the available language models configured on the Sourcebot instance. Use this to discover which models can be specified when calling `ask_codebase`.
+
+Parameters:
+
+This tool takes no parameters.
+
+
+### `ask_codebase`
 
-Fetches the source code for a given file.
+Ask a natural language question about the codebase. This tool uses an AI agent to autonomously search code, read files, and find symbol references/definitions to answer your question. Returns a detailed answer in markdown format with code references, plus a link to view the full research session in the Sourcebot web UI.
 
 Parameters:
-| Name         | Required | Description                                                      |
-|:-------------|:---------|:-----------------------------------------------------------------|
-| `fileName`   | yes      | The file to fetch the source code for.                           |
-| `repoId`     | yes      | The Sourcebot repository ID.                                     |
+| Name            | Required | Description                                                                                                                                    |
+|:----------------|:---------|:-----------------------------------------------------------------------------------------------------------------------------------------------|
+| `query`         | yes      | The query to ask about the codebase.                                                                                                           |
+| `repos`         | no       | The repositories that are accessible to the agent during the chat. If not provided, all repositories are accessible.                           |
+| `languageModel` | no       | The language model to use for answering the question. Object with `provider` and `model`. If not provided, defaults to the first model in the config. Use `list_language_models` to see available options. |
 
 
 ## Environment Variables

diff --git a/packages/mcp/CHANGELOG.md b/packages/mcp/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- Added `ask_codebase` tool that can invoke the Ask subagent to explore a set of codebases and return a summarized answer. [#814](https://github.com/sourcebot-dev/sourcebot/pull/814)
+- Added `list_language_models` tool to discover available language models configured on the Sourcebot instance. [#814](https://github.com/sourcebot-dev/sourcebot/pull/814)
+
 ## [1.0.14] - 2026-01-27
 
 ### Changed

diff --git a/packages/mcp/README.md b/packages/mcp/README.md
@@ -234,6 +234,32 @@ Get a list of commits for a given repository.
 
 </details>
 
+### list_language_models
+
+Lists the available language models configured on the Sourcebot instance. Use this to discover which models can be specified when calling `ask_codebase`.
+
+<details>
+<summary>Parameters</summary>
+
+This tool takes no parameters.
+
+</details>
+
+### ask_codebase
+
+Ask a natural language question about the codebase. This tool uses an AI agent to autonomously search code, read files, and find symbol references/definitions to answer your question. Returns a detailed answer in markdown format with code references, plus a link to view the full research session in the Sourcebot web UI.
+
+<details>
+<summary>Parameters</summary>
+
+| Name            | Required | Description                                                                                                                                    |
+|:----------------|:---------|:-----------------------------------------------------------------------------------------------------------------------------------------------|
+| `query`         | yes      | The query to ask about the codebase.                                                                                                           |
+| `repos`         | no       | The repositories that are accessible to the agent during the chat. If not provided, all repositories are accessible.                           |
+| `languageModel` | no       | The language model to use for answering the question. Object with `provider` and `model`. If not provided, defaults to the first model in the config. Use `list_language_models` to see available options. |
+
+</details>
+
 
 ## Supported Code Hosts
 Sourcebot supports the following code hosts:

diff --git a/packages/mcp/src/client.ts b/packages/mcp/src/client.ts
@@ -1,6 +1,6 @@
 import { env } from './env.js';
-import { listReposResponseSchema, searchResponseSchema, fileSourceResponseSchema, listCommitsResponseSchema } from './schemas.js';
-import { FileSourceRequest, ListReposQueryParams, SearchRequest, ListCommitsQueryParamsSchema } from './types.js';
+import { listReposResponseSchema, searchResponseSchema, fileSourceResponseSchema, listCommitsResponseSchema, askCodebaseResponseSchema, listLanguageModelsResponseSchema } from './schemas.js';
+import { AskCodebaseRequest, AskCodebaseResponse, FileSourceRequest, ListReposQueryParams, SearchRequest, ListCommitsQueryParamsSchema, ListLanguageModelsResponse } from './types.js';
 import { isServiceError, ServiceErrorException } from './utils.js';
 import { z } from 'zod';
 
@@ -106,4 +106,43 @@ export const listCommits = async (queryParams: ListCommitsQueryParamsSchema) =>
     const commits = await parseResponse(response, listCommitsResponseSchema);
     const totalCount = parseInt(response.headers.get('X-Total-Count') ?? '0', 10);
     return { commits, totalCount };
-}
+}
+
+/**
+ * Asks a natural language question about the codebase using the Sourcebot AI agent.
+ * This is a blocking call that runs the full agent loop and returns when complete.
+ *
+ * @param request - The question and optional repo filters
+ * @returns The agent's answer, chat URL, sources, and metadata
+ */
+export const askCodebase = async (request: AskCodebaseRequest): Promise<AskCodebaseResponse> => {
+    const response = await fetch(`${env.SOURCEBOT_HOST}/api/chat/blocking`, {
+        method: 'POST',
+        headers: {
+            'Content-Type': 'application/json',
+            'X-Sourcebot-Client-Source': 'mcp',
+            ...(env.SOURCEBOT_API_KEY ? { 'X-Sourcebot-Api-Key': env.SOURCEBOT_API_KEY } : {})
+        },
+        body: JSON.stringify(request),
+    });
+
+    return parseResponse(response, askCodebaseResponseSchema);
+}
+
+/**
+ * Lists the available language models configured on the Sourcebot instance.
+ *
+ * @returns Array of language model info objects
+ */
+export const listLanguageModels = async (): Promise<ListLanguageModelsResponse> => {
+    const response = await fetch(`${env.SOURCEBOT_HOST}/api/models`, {
+        method: 'GET',
+        headers: {
+            'Content-Type': 'application/json',
+            'X-Sourcebot-Client-Source': 'mcp',
+            ...(env.SOURCEBOT_API_KEY ? { 'X-Sourcebot-Api-Key': env.SOURCEBOT_API_KEY } : {})
+        },
+    });
+
+    return parseResponse(response, listLanguageModelsResponseSchema);
+}
diff --git a/packages/mcp/src/index.ts b/packages/mcp/src/index.ts
@@ -6,10 +6,10 @@ import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js'
 import _dedent from "dedent";
 import escapeStringRegexp from 'escape-string-regexp';
 import { z } from 'zod';
-import { getFileSource, listCommits, listRepos, search } from './client.js';
+import { askCodebase, getFileSource, listCommits, listLanguageModels, listRepos, search } from './client.js';
 import { env, numberSchema } from './env.js';
-import { fileSourceRequestSchema, listCommitsQueryParamsSchema, listReposQueryParamsSchema } from './schemas.js';
-import { FileSourceRequest, ListCommitsQueryParamsSchema, ListReposQueryParams, TextContent } from './types.js';
+import { askCodebaseRequestSchema, fileSourceRequestSchema, listCommitsQueryParamsSchema, listReposQueryParamsSchema } from './schemas.js';
+import { AskCodebaseRequest, FileSourceRequest, ListCommitsQueryParamsSchema, ListReposQueryParams, TextContent } from './types.js';
 
 const dedent = _dedent.withOptions({ alignValues: true });
 
@@ -238,7 +238,57 @@ server.tool(
     }
 );
 
+server.tool(
+    "list_language_models",
+    dedent`Lists the available language models configured on the Sourcebot instance. Use this to discover which models can be specified when calling ask_codebase.`,
+    {},
+    async () => {
+        const models = await listLanguageModels();
+
+        return {
+            content: [{
+                type: "text",
+                text: JSON.stringify(models),
+            }],
+        };
+    }
+);
+
+server.tool(
+    "ask_codebase",
+    dedent`
+    Ask a natural language question about the codebase. This tool uses an AI agent to autonomously search code, read files, and find symbol references/definitions to answer your question.
+
+    The agent will:
+    - Analyze your question and determine what context it needs
+    - Search the codebase using multiple strategies (code search, symbol lookup, file reading)
+    - Synthesize findings into a comprehensive answer with code references
 
+    Returns a detailed answer in markdown format with code references, plus a link to view the full research session (including all tool calls and reasoning) in the Sourcebot web UI.
+
+    This is a blocking operation that may take 30-60+ seconds for complex questions as the agent researches the codebase.
+    `,
+    askCodebaseRequestSchema.shape,
+    async (request: AskCodebaseRequest) => {
+        const response = await askCodebase(request);
+
+        // Format the response with the answer and a link to the chat
+        const formattedResponse = dedent`
+        ${response.answer}
+
+        ---
+        **View full research session:** ${response.chatUrl}
+        **Model used:** ${response.languageModel.model}
+        `;
+
+        return {
+            content: [{
+                type: "text",
+                text: formattedResponse,
+            }],
+        };
+    }
+);
 
 const runServer = async () => {
     const transport = new StdioServerTransport();

diff --git a/packages/mcp/src/schemas.ts b/packages/mcp/src/schemas.ts
@@ -272,3 +272,45 @@ export const listCommitsResponseSchema = z.array(z.object({
     author_name: z.string(),
     author_email: z.string(),
 }));
+
+export const languageModelInfoSchema = z.object({
+    provider: z.string().describe("The model provider (e.g., 'anthropic', 'openai')"),
+    model: z.string().describe("The model ID"),
+    displayName: z.string().optional().describe("Optional display name for the model"),
+});
+
+export const listLanguageModelsResponseSchema = z.array(languageModelInfoSchema);
+
+export const askCodebaseRequestSchema = z.object({
+    query: z
+        .string()
+        .describe("The query to ask about the codebase."),
+    repos: z
+        .array(z.string())
+        .optional()
+        .describe("The repositories that are accessible to the agent during the chat. If not provided, all repositories are accessible."),
+    languageModel: languageModelInfoSchema
+        .omit({ displayName: true })
+        .optional()
+        .describe("The language model to use for answering the question. If not provided, defaults to the first model in the config. Use list_language_models to see available options."),
+});
+
+export const sourceSchema = z.object({
+    type: z.literal('file'),
+    repo: z.string(),
+    path: z.string(),
+    name: z.string(),
+    language: z.string(),
+    revision: z.string(),
+});
+
+export const askCodebaseResponseSchema = z.object({
+    answer: z.string().describe("The agent's final answer in markdown format"),
+    chatId: z.string().describe("ID of the persisted chat session"),
+    chatUrl: z.string().describe("URL to view the chat in the web UI"),
+    languageModel: z.object({
+        provider: z.string().describe("The model provider (e.g., 'anthropic', 'openai')"),
+        model: z.string().describe("The model ID"),
+        displayName: z.string().optional().describe("Optional display name for the model"),
+    }).describe("The language model used to generate the response"),
+});