[9.2] Adds initial agents.md file (#250833)

.github/CODEOWNERS

@@ -3063,6 +3063,9 @@ x-pack/plugins/observability_solution/synthetics/server/saved_objects/synthetics
 .moon         @elastic/kibana-operations
 /**/moon.yml  @elastic/kibana-operations
 
+# Leads approval
+/AGENTS.md @elastic/kibana-tech-leads
+
 ####
 ## These rules are always last so they take ultimate priority over everything else
 ####

AGENTS.md

@@ -0,0 +1,77 @@
+# Kibana
+
+## Setup
+- Run `yarn kbn bootstrap` for initial setup, after switching branches, or when encountering dependency errors
+
+## Overview
+- Kibana is organized into modules, each defined by a `kibana.jsonc`: core, packages, and plugin packages. Aside from tooling and testing, most code lives in these modules.
+- Packages are reusable units with explicit boundaries and a single public entry point (no subpath imports), usually with a focused purpose.
+- Plugins are a package type (`type: "plugin"`) that include a plugin class with setup/start/stop lifecycles, utilized by the core platform to enable applications.
+- Plugins that depend on other plugins rely on the contracts returned by those lifecycles, so circular dependencies must be avoided.
+- Module IDs (typically `@kbn/...`) live in `kibana.jsonc`; `package.json` names are derived where present.
+- Plugin IDs are additional camelCase IDs under `plugin.id` in `kibana.jsonc`, used by core platform and other plugins.
+- Modules are grouped by domain (platform vs solutions) with visibility rules (`shared` vs `private`) that limit cross-group access.
+- Utility scripts live in `scripts/` (e.g., `node scripts/generate.js`).
+
+## Critical Thinking
+- Fix root cause (not band-aid).
+- Unsure: read more code; if still stuck, ask w/ short options.
+- Conflicts: call out; pick safer path.
+- Unrecognized changes: assume other agent; keep going; focus your changes. If it causes issues, stop + ask user.
+
+## Testing
+
+### Jest unit
+`yarn test:jest [--config=<pathToConfigFile>] [TestPathPattern]`
+
+### Jest integration
+`yarn test:jest_integration [--config=<pathToConfigFile>] [TestPathPattern]`
+
+### Type check
+`yarn test:type_check [--project path/to/tsconfig.json]`
+
+### Function Test Runner (FTR)
+`yarn test:ftr [--config <file1> [--config <file2> ...]]`
+- For new tests, prefer using Scout
+
+### Scout (UI/API with Playwright)
+`node scripts/scout.js run-tests --stateful --config <scoutConfigPath>` (or `--testFiles <specPath1,specPath2>`)
+
+## Code Style Guidelines
+Follow existing patterns in the target area first; below are common defaults.
+
+### TypeScript & Types
+- Use TypeScript for all new code; avoid `any`.
+- Prefer explicit return types for public APIs and exported functions.
+- Use `import type` for type-only imports.
+- Avoid non-null assertions (`!`) unless locally justified.
+- Prefer `readonly` and `as const` for immutable structures.
+- Prefer const arrow functions
+- Prefer explicit import/exports over "*"
+- Prefer destructuring of variables, rather than property access
+
+### Formatting
+- Follow existing formatting in the file; do not reformat unrelated code.
+- `yarn llm` runs ESLint `--fix` on changed JS/TS files and may apply formatting-style fixes.
+- Prefer single quotes in TS/JS unless the file uses double quotes.
+
+### Naming
+- `PascalCase` for classes, types, and React components.
+- `camelCase` for functions, variables, and object keys.
+- New filenames must be `snake_case` (lowercase with underscores) unless an existing convention requires otherwise.
+- Use descriptive names; avoid single-letter names outside tight loops.
+
+### Control Flow & Error Handling
+- Prefer early returns and positive conditions.
+- Handle errors explicitly; return typed errors from APIs when possible.
+- Keep async logic linear; avoid nested `try` blocks when possible.
+
+### React / UI Conventions
+- Use functional components; type props explicitly.
+- Keep hooks at the top level; avoid conditional hooks.
+- Avoid inline styles unless consistent with the file’s conventions.
+- Use `@elastic/eui` components with Emotion (`@emotion/react`) for styling.
+
+## Contribution Hygiene
+- Make focused changes; avoid unrelated refactors.
+- Update docs when behavior or usage changes.