🤖 feat: add /init slash command for AGENTS.md bootstrap (#1190)

Add `/init` command that populates the chat input with a pre-written
prompt to generate an AGENTS.md file for a project.

- Works in both creation and workspace variants
- Populates input for user review before sending
- Added parser tests

---
_Generated with `mux` • Model: `anthropic:claude-opus-4-5` • Thinking:
`medium`_

Author: deansheather

src/browser/assets/initMessage.txt

@@ -0,0 +1,76 @@
+<system>
+Use your tools to write an AGENTS.md file in the root of the workspace which will serve as a contribution guide for AI agents.
+Inspect the workspace layout, code, documentation and git history to ensure correctness and accuracy.
+
+Insert the following preamble at the top of the file before any other sections. Do not include the surrounding code fence backticks; only include the text.
+```md
+You are an experienced, pragmatic software engineering AI agent. Do not over-engineer a solution when a simple one is possible. Keep edits minimal. If you want an exception to ANY rule, you MUST stop and get permission first.
+```
+
+Recommended sections:
+- Project Overview (mandatory)
+    - Basic details about the project (e.g., high-level overview and goals).
+    - Technology choices (e.g., languages, databases, frameworks, libraries, build tools).
+- Reference (mandatory)
+    - List important code files.
+    - List important directories and basic code structure tips.
+    - Project architecture.
+- Essential commands (mandatory)
+    - build
+    - format
+    - lint
+    - test
+    - clean
+    - development server
+    - other *important* scripts (use `find -type f -name '*.sh'` or similar)
+- Patterns (optional)
+    - List any important or uncommon patterns (compared to other similar codebases), with examples (e.g., how to authorize an HTTP request).
+    - List any important workflows and their steps (e.g., how to make a database migration).
+    - Testing patterns.
+- Anti-patterns (optional)
+    - Search git history and comments to find recurring mistakes or forbidden patterns.
+    - List each pattern and its reason.
+- Code style (optional)
+    - Style guide to follow (with link).
+- Commit and Pull Request Guidelines (mandatory)
+    - Required steps for validating changes before committing.
+    - Commit message conventions (read `git log`, or use `type: message` by default).
+    - Pull request description requirements.
+
+You can add other sections if they are necessary.
+If the information required for mandatory sections isn't available due to the workspace being empty or sparse, add TODO text in its place.
+Optional sections should be scrapped if the information is too thin.
+
+Some investigation tips:
+ - Read existing lint configs, tsconfig, and CI workflows to find any style or layout rules.
+ - Search for "TODO", "HACK", "FIXME", "don't", "never", "always" in comments.
+ - Examine test files for patterns.
+ - Read PR templates and issue templates if they exist.
+ - Check for existing CONTRIBUTING.md, CODE_OF_CONDUCT.md, or similar documentation files.
+
+Some writing tips:
+- Each "do X" should have a corresponding "don't Y" where applicable.
+- Commands should be easily copy-pastable and tested.
+- Terms or phrases specific to this project should be explained on first use.
+- Anything that is against the norm should be explicitly highlighted and called out.
+
+Above all things:
+- The document must be clear and concise. Simple projects should need less than 400 words, but larger and more mature codebases will likely need 700+. Prioritize completeness over brevity.
+- Don't include useless fluff.
+- The document must be in Markdown format and use headings for structure.
+- Give examples where necessary or helpful (commands, directory paths, naming patterns).
+- Explanations and examples must be correct and specific to this codebase.
+- Maintain a professional, instructional tone.
+
+If the workspace is empty or sparse, ask the user for more information. Avoid hallucinating important decisions. You can provide suggestions to the user for language/technology/tool choices, but always respect the user's decision.
+- Project description and goals.
+- Language(s).
+- Technologies (database?), frameworks, libraries.
+- Tools.
+- Any other questions as you deem necessary.
+
+For empty or sparse workspaces ONLY, when finished writing AGENTS.md, ask the user if they would like you to do the following:
+- initialize git IF it's not already set up (e.g., `git init`, `git remote add`, etc.)
+- write a concise README.md file
+- generate the bare minimum project scaffolding (e.g., initializing the package manager, writing a minimal build tool config)
+</system>

src/browser/components/ChatInput/index.tsx

@@ -93,6 +93,7 @@ import {
 } from "./draftImagesStorage";
 import { RecordingOverlay } from "./RecordingOverlay";
 import { ReviewBlockFromData } from "../shared/ReviewBlock";
+import initMessage from "@/browser/assets/initMessage.txt?raw";
 
 // localStorage quotas are environment-dependent and relatively small.
 // Be conservative here so we can warn the user before writes start failing.
@@ -855,6 +856,16 @@ const ChatInputInner: React.FC<ChatInputProps> = (props) => {
 
     // Route to creation handler for creation variant
     if (variant === "creation") {
+      // Handle /init command in creation variant - populate input with init message
+      if (messageText.startsWith("/")) {
+        const parsed = parseCommand(messageText);
+        if (parsed?.type === "init") {
+          setInput(initMessage);
+          focusMessageInput();
+          return;
+        }
+      }
+
       // Creation variant: simple message send + workspace creation
       const creationImageParts = imageAttachmentsToImageParts(imageAttachments);
       const ok = await creationState.handleSend(
@@ -952,7 +963,12 @@ const ChatInputInner: React.FC<ChatInputProps> = (props) => {
           return;
         }
 
-        // Handle /vim command
+        // Handle /init command - populate input with init message
+        if (parsed.type === "init") {
+          setInput(initMessage);
+          focusMessageInput();
+          return;
+        }
 
         // Handle other non-API commands (help, invalid args, etc)
         const commandToast = createCommandToast(parsed);

src/browser/utils/slashCommands/parser.test.ts

@@ -226,3 +226,17 @@ describe("plan commands", () => {
     });
   });
 });
+
+describe("init command", () => {
+  it("should parse /init", () => {
+    expectParse("/init", { type: "init" });
+  });
+
+  it("should reject /init with arguments", () => {
+    expectParse("/init extra", {
+      type: "unknown-command",
+      command: "init",
+      subcommand: "extra",
+    });
+  });
+});

src/browser/utils/slashCommands/registry.ts

@@ -456,6 +456,23 @@ const vimCommandDefinition: SlashCommandDefinition = {
   },
 };
 
+const initCommandDefinition: SlashCommandDefinition = {
+  key: "init",
+  description: "Bootstrap an AGENTS.md file in a new or existing project",
+  appendSpace: false,
+  handler: ({ cleanRemainingTokens }): ParsedCommand => {
+    if (cleanRemainingTokens.length > 0) {
+      return {
+        type: "unknown-command",
+        command: "init",
+        subcommand: cleanRemainingTokens[0],
+      };
+    }
+
+    return { type: "init" };
+  },
+};
+
 const planOpenCommandDefinition: SlashCommandDefinition = {
   key: "open",
   description: "Open plan in external editor",
@@ -700,6 +717,7 @@ export const SLASH_COMMAND_DEFINITIONS: readonly SlashCommandDefinition[] = [
   vimCommandDefinition,
   mcpCommandDefinition,
   idleCommandDefinition,
+  initCommandDefinition,
 ];
 
 export const SLASH_COMMAND_DEFINITION_MAP = new Map(

src/browser/utils/slashCommands/types.ts

@@ -35,6 +35,7 @@ export type ParsedCommand =
   | { type: "mcp-open" }
   | { type: "plan-show" }
   | { type: "plan-open" }
+  | { type: "init" }
   | { type: "unknown-command"; command: string; subcommand?: string }
   | { type: "idle-compaction"; hours: number | null }
   | null;

src/types/txt.d.ts

@@ -0,0 +1,4 @@
+declare module "*.txt?raw" {
+  const content: string;
+  export default content;
+}