Release extension version 0.3.30 (#274)

Co-authored-by: GitHub Actions <github-actions@github.com>

docs/esm-migration-plan.md

@@ -0,0 +1,299 @@
+# ESM Migration Plan: Add File Extensions to Imports
+
+## Overview
+
+This document outlines the plan to migrate from TypeScript's deprecated `"moduleResolution": "node"` (node10) to `"moduleResolution": "node16"` or `"nodenext"`. This change is necessary because the published ESM packages have extensionless imports that don't work correctly in modern ESM environments.
+
+## Issues Fixed
+
+This migration will resolve the following issues:
+
+- **#154** - Upgrade `moduleResolution` from `node` to `node16` or `nodenext` in tsconfig
+- **#110** - Published ESM code has imports without file extensions
+- **#64** - expressions: ERR_MODULE_NOT_FOUND attempting to run example demo script  
+- **#146** - Can not import `@actions/workflow-parser`
+
+## Problem Statement
+
+### Current State
+
+All packages use `"moduleResolution": "node"`:
+
+| Package | moduleResolution | TypeScript |
+|---------|------------------|------------|
+| expressions | `"node"` | ^4.7.4 |
+| workflow-parser | `"node"` | ^4.8.4 |
+| languageservice | `"node"` | ^4.8.4 |
+| languageserver | `"node"` | ^4.8.4 |
+| browser-playground | `"Node16"` ✅ | ^4.9.4 |
+
+This causes TypeScript to emit code like:
+```javascript
+// Published to npm - INVALID ESM
+export { Expr } from "./ast";  // Missing .js extension!
+```
+
+### Why This Fails
+
+ESM in Node.js 12+ **requires** explicit file extensions. When users try to import these packages:
+
+```javascript
+// User's code
+import { Expr } from "@actions/expressions";
+```
+
+Node.js fails with:
+```
+Error [ERR_MODULE_NOT_FOUND]: Cannot find module '.../node_modules/@actions/expressions/dist/ast'
+```
+
+## Migration Strategy
+
+### Option A: TypeScript 5.7+ with `rewriteRelativeImportExtensions` (Recommended)
+
+TypeScript 5.7 introduced a new compiler option that automatically rewrites `.ts` extensions to `.js` in output:
+
+```jsonc
+{
+  "compilerOptions": {
+    "moduleResolution": "node16",  // or "nodenext"
+    "rewriteRelativeImportExtensions": true
+  }
+}
+```
+
+**Source code:**
+```typescript
+import { Expr } from "./ast.ts";
+```
+
+**Compiled output:**
+```javascript
+export { Expr } from "./ast.js";
+```
+
+**Pros:**
+- Source uses `.ts` extensions (matches actual files)
+- Works with Deno (which requires `.ts` extensions)
+- TypeScript automatically transforms to `.js`
+- Modern, forward-looking approach
+
+**Cons:**
+- Requires TypeScript 5.7+
+- Relatively new feature
+- **BUG:** See "Known Issues" section below
+
+### Option B: Manual `.js` Extensions
+
+Use `.js` extensions in source TypeScript files:
+
+```typescript
+import { Expr } from "./ast.js";  // Points to .ts file, but use .js extension
+```
+
+**Pros:**
+- Works with TypeScript 4.7+ (with node16 moduleResolution)
+- Well-established pattern
+- No post-processing needed
+- Works with ts-jest without extra configuration
+
+**Cons:**
+- Confusing - `.js` files don't exist at write time
+- Doesn't work with Deno out of the box
+
+### Recommendation
+
+**Use Option B** (manual `.js` extensions). Option A with `rewriteRelativeImportExtensions` has compatibility issues with ts-jest and requires additional workarounds.
+
+---
+
+## Known Issues and Workarounds (December 2025)
+
+### 1. TypeScript Version Conflicts in Monorepo
+
+**Problem:** The root `node_modules/typescript` was version 4.9.5 (pulled in by `ts-node` and `tsutils` dependencies), while workspace packages specified `^5.8.3`.
+
+**Symptoms:** 
+- `npx tsc --version` showed 4.9.5
+- `require('typescript').version` in ts-jest showed 5.8.3
+- Confusing build failures
+
+**Solution:** Add npm overrides in root `package.json`:
+```json
+{
+  "overrides": {
+    "typescript": "5.8.3"
+  }
+}
+```
+
+### 2. ts-jest Compatibility with TypeScript 5.9+
+
+**Problem:** ts-jest 29.4.6 uses `typescript.JSDocParsingMode.ParseAll` which doesn't exist in TypeScript's ES module exports.
+
+**Error:**
+```
+TypeError: Cannot read properties of undefined (reading 'ParseAll')
+at Object.<anonymous> (node_modules/ts-jest/dist/compiler/ts-compiler.js:43:123)
+```
+
+**Root Cause:** ts-jest accesses `typescript_1.default.JSDocParsingMode.ParseAll` but TypeScript has no default export in ESM.
+
+**Solution:** 
+- Use ts-jest 29.0.3 (older version that doesn't use this API)
+- OR wait for ts-jest fix
+- **Stay on TypeScript 5.8.3, not 5.9+**
+
+### 3. TypeScript `rewriteRelativeImportExtensions` Bug with .d.ts Files
+
+**Problem:** TypeScript's `rewriteRelativeImportExtensions: true` correctly rewrites `.ts` → `.js` in `.js` output files, but **incorrectly keeps `.ts` extensions in `.d.ts` declaration files**.
+
+**Example:**
+- Source: `export { Expr } from "./ast.ts";`
+- Output `index.js`: `export { Expr } from "./ast.js";` ✅ Correct
+- Output `index.d.ts`: `export { Expr } from "./ast.ts";` ❌ Wrong (should be `.js`)
+
+**Upstream Issue:** https://github.com/microsoft/TypeScript/issues/61037 (marked "Help Wanted", in Backlog, NOT FIXED as of Dec 2025)
+
+**Workaround:** Post-process `.d.ts` files with a script. See `script/fix-dts-extensions.cjs`.
+
+**Note:** Since we use Option B (manual `.js` extensions), this bug does not affect our migration.
+
+### 4. yaml Package Internal Types Not Exported
+
+**Problem:** The `yaml` package does not export internal types like `LinePos` and `NodeBase` that are used in `workflow-parser/src/workflows/yaml-object-reader.ts`.
+
+**Error:**
+```
+error TS2305: Module '"yaml"' has no exported member 'LinePos'.
+error TS2305: Module '"yaml"' has no exported member 'NodeBase'.
+```
+
+**Solution:** Define local type aliases in the file that uses them:
+```typescript
+// Local type definitions to replace yaml internal imports
+type LinePos = { line: number; col: number };
+type NodeBase = { range?: [number, number, number] };
+```
+
+### 5. languageserver Blocked by vscode-languageserver Dependency
+
+**Problem:** The `vscode-languageserver` package (v8.0.2) does not have proper ESM exports. When using `moduleResolution: "node16"`, TypeScript requires packages to have an `exports` field in `package.json` for subpath imports to work.
+
+**Error:**
+```
+src/index.ts(6,8): error TS2307: Cannot find module 'vscode-languageserver/browser' or its corresponding type declarations.
+src/connection.ts(1,43): error TS2307: Cannot find module 'vscode-languageserver/node' or its corresponding type declarations.
+```
+
+**Root Cause:** The `vscode-languageserver` package.json only has `main` and `browser` fields, but no `exports` field:
+```json
+{
+  "main": "./lib/node/main.js",
+  "browser": {
+    "./lib/node/main.js": "./lib/browser/main.js"
+  }
+  // No "exports" field!
+}
+```
+
+With `moduleResolution: "node16"`, TypeScript follows Node.js ESM resolution rules which require explicit `exports` for subpath imports like `vscode-languageserver/browser` and `vscode-languageserver/node`.
+
+**Status:** Verified December 2025. Version 9.0.1 is available but ESM export support is not confirmed.
+
+**Current Decision:** The languageserver package is **deferred** from this migration until the upstream `vscode-languageserver` package adds proper ESM exports. It will continue using the old `moduleResolution: "node"` configuration.
+
+**Options to resolve:**
+- Wait for vscode-languageserver to add ESM exports
+- Try upgrading to vscode-languageserver v9.x to see if exports were added
+- Use a bundler to work around the module resolution
+- Fork or patch the dependency
+
+---
+
+## Migration Status
+
+| Package | Tests | ESM Status |
+|---------|-------|------------|
+| expressions | 1068 | ✅ Migrated |
+| workflow-parser | 292 | ✅ Migrated |
+| languageservice | 452 | ✅ Migrated |
+| languageserver | 6 files | ⏸️ Deferred (vscode-languageserver lacks ESM exports) |
+
+---
+
+## Required Configuration Changes
+
+### tsconfig.build.json (each migrated package)
+
+**Note:** We use **Option B** (manual `.js` extensions in source files) rather than `rewriteRelativeImportExtensions` because Option A caused ts-jest compatibility issues (tests would hang indefinitely).
+
+```json
+{
+  "compilerOptions": {
+    "module": "node16",
+    "moduleResolution": "node16",
+    "skipLibCheck": true,
+    "lib": ["ES2022"],
+    "target": "ES2022"
+  }
+}
+```
+
+The `skipLibCheck: true` is needed to work around @types/node compatibility issues with TypeScript 5.x (TS2386 overload signature errors).
+```
+
+### jest.config.js (each migrated package)
+
+```javascript
+/** @type {import('ts-jest').JestConfigWithTsJest} */
+export default {
+  preset: "ts-jest/presets/default-esm",
+  moduleNameMapper: {
+    "^(\\.{1,2}/.*)\\.js$": "$1",
+    "^(\\.{1,2}/.*)\\.ts$": "$1",
+  },
+  transform: {
+    "^.+\\.tsx?$": [
+      "ts-jest",
+      {
+        useESM: true,
+        isolatedModules: true,
+      },
+    ],
+  },
+  moduleFileExtensions: ["ts", "js"],
+};
+```
+
+### Root package.json
+
+```json
+{
+  "overrides": {
+    "typescript": "5.8.3"
+  }
+}
+```
+
+### Each workspace package.json
+
+```json
+{
+  "devDependencies": {
+    "typescript": "^5.8.3",
+    "ts-jest": "^29.0.3"
+  }
+}
+```
+
+---
+
+## References
+
+- [TypeScript moduleResolution reference](https://www.typescriptlang.org/docs/handbook/modules/reference.html)
+- [TypeScript 5.7 rewriteRelativeImportExtensions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-5-7.html#path-rewriting-for-relative-paths)
+- [TypeScript .d.ts extension bug #61037](https://github.com/microsoft/TypeScript/issues/61037)
+- [Node.js ESM mandatory extensions](https://nodejs.org/api/esm.html#mandatory-file-extensions)
+- [ts-jest ESM support](https://kulshekhar.github.io/ts-jest/docs/guides/esm-support)
+- [Community fork that works](https://github.com/boxbuild-io/actions-languageservices/commit/077fb2b58dfd2cca3d6e3df1fdf9e26e75db24ae)

expressions/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/expressions",
-  "version": "0.3.25",
+  "version": "0.3.30",
   "license": "MIT",
   "type": "module",
   "source": "./src/index.ts",
@@ -60,6 +60,6 @@
     "prettier": "^2.8.3",
     "rimraf": "^3.0.2",
     "ts-jest": "^29.0.3",
-    "typescript": "^4.7.4"
+    "typescript": "^5.8.3"
   }
 }

expressions/src/ast.ts

@@ -1,5 +1,5 @@
-import {ExpressionData} from "./data";
-import {Token} from "./lexer";
+import {ExpressionData} from "./data/index.js";
+import {Token} from "./lexer.js";
 
 export interface ExprVisitor<R> {
   visitLiteral(literal: Literal): R;

expressions/src/completion.test.ts

@@ -1,11 +1,11 @@
-import {complete, CompletionItem, trimTokenVector} from "./completion";
-import {DescriptionDictionary} from "./completion/descriptionDictionary";
-import {BooleanData} from "./data/boolean";
-import {Dictionary} from "./data/dictionary";
-import {StringData} from "./data/string";
-import {wellKnownFunctions} from "./funcs";
-import {FunctionDefinition, FunctionInfo} from "./funcs/info";
-import {Lexer, TokenType} from "./lexer";
+import {complete, CompletionItem, trimTokenVector} from "./completion.js";
+import {DescriptionDictionary} from "./completion/descriptionDictionary.js";
+import {BooleanData} from "./data/boolean.js";
+import {Dictionary} from "./data/dictionary.js";
+import {StringData} from "./data/string.js";
+import {wellKnownFunctions} from "./funcs.js";
+import {FunctionDefinition, FunctionInfo} from "./funcs/info.js";
+import {Lexer, TokenType} from "./lexer.js";
 
 const testContext = new Dictionary(
   {

expressions/src/completion.ts

@@ -1,11 +1,11 @@
-import {DescriptionPair} from "./completion/descriptionDictionary";
-import {Dictionary, isDictionary} from "./data/dictionary";
-import {ExpressionData} from "./data/expressiondata";
-import {Evaluator} from "./evaluator";
-import {wellKnownFunctions} from "./funcs";
-import {FunctionDefinition, FunctionInfo} from "./funcs/info";
-import {Lexer, Token, TokenType} from "./lexer";
-import {Parser} from "./parser";
+import {DescriptionPair} from "./completion/descriptionDictionary.js";
+import {Dictionary, isDictionary} from "./data/dictionary.js";
+import {ExpressionData} from "./data/expressiondata.js";
+import {Evaluator} from "./evaluator.js";
+import {wellKnownFunctions} from "./funcs.js";
+import {FunctionDefinition, FunctionInfo} from "./funcs/info.js";
+import {Lexer, Token, TokenType} from "./lexer.js";
+import {Parser} from "./parser.js";
 
 export type CompletionItem = {
   label: string;

expressions/src/completion/descriptionDictionary.test.ts

@@ -1,5 +1,5 @@
-import {StringData} from "../data";
-import {DescriptionDictionary} from "./descriptionDictionary";
+import {StringData} from "../data/index.js";
+import {DescriptionDictionary} from "./descriptionDictionary.js";
 
 describe("description dictionary", () => {
   it("pairs contains all values", () => {

expressions/src/completion/descriptionDictionary.ts

@@ -1,5 +1,5 @@
-import {Dictionary} from "../data/dictionary";
-import {ExpressionData, Kind, Pair} from "../data/expressiondata";
+import {Dictionary} from "../data/dictionary.js";
+import {ExpressionData, Kind, Pair} from "../data/expressiondata.js";
 
 export type DescriptionPair = Pair & {description?: string};
 

expressions/src/data/array.ts

@@ -1,4 +1,4 @@
-import {ExpressionData, ExpressionDataInterface, Kind, kindStr} from "./expressiondata";
+import {ExpressionData, ExpressionDataInterface, Kind, kindStr} from "./expressiondata.js";
 
 export class Array implements ExpressionDataInterface {
   private v: ExpressionData[] = [];

expressions/src/data/boolean.ts

@@ -1,4 +1,4 @@
-import {ExpressionDataInterface, Kind} from "./expressiondata";
+import {ExpressionDataInterface, Kind} from "./expressiondata.js";
 
 export class BooleanData implements ExpressionDataInterface {
   constructor(public readonly value: boolean) {}

expressions/src/data/dictionary.test.ts

@@ -1,5 +1,5 @@
-import {Dictionary} from "./dictionary";
-import {StringData} from "./string";
+import {Dictionary} from "./dictionary.js";
+import {StringData} from "./string.js";
 
 describe("dictionary", () => {
   it("pairs contains all values", () => {

expressions/src/data/dictionary.ts

@@ -1,4 +1,4 @@
-import {ExpressionData, ExpressionDataInterface, Kind, kindStr, Pair} from "./expressiondata";
+import {ExpressionData, ExpressionDataInterface, Kind, kindStr, Pair} from "./expressiondata.js";
 
 export class Dictionary implements ExpressionDataInterface {
   private keys: string[] = [];

expressions/src/data/expressiondata.ts

@@ -1,9 +1,9 @@
-import {Dictionary} from "./dictionary";
-import {Null} from "./null";
-import {Array} from "./array";
-import {StringData} from "./string";
-import {NumberData} from "./number";
-import {BooleanData} from "./boolean";
+import {Dictionary} from "./dictionary.js";
+import {Null} from "./null.js";
+import {Array} from "./array.js";
+import {StringData} from "./string.js";
+import {NumberData} from "./number.js";
+import {BooleanData} from "./boolean.js";
 
 export enum Kind {
   String = 0,

expressions/src/data/index.ts

@@ -1,9 +1,9 @@
-export {Array} from "./array";
-export {BooleanData} from "./boolean";
-export {Dictionary} from "./dictionary";
-export {ExpressionData, Kind} from "./expressiondata";
-export {Null} from "./null";
-export {NumberData} from "./number";
-export {replacer} from "./replacer";
-export {reviver} from "./reviver";
-export {StringData} from "./string";
+export {Array} from "./array.js";
+export {BooleanData} from "./boolean.js";
+export {Dictionary} from "./dictionary.js";
+export {ExpressionData, Kind} from "./expressiondata.js";
+export {Null} from "./null.js";
+export {NumberData} from "./number.js";
+export {replacer} from "./replacer.js";
+export {reviver} from "./reviver.js";
+export {StringData} from "./string.js";

expressions/src/data/null.ts

@@ -1,4 +1,4 @@
-import {ExpressionDataInterface, Kind} from "./expressiondata";
+import {ExpressionDataInterface, Kind} from "./expressiondata.js";
 
 export class Null implements ExpressionDataInterface {
   public readonly kind = Kind.Null;

expressions/src/data/number.test.ts

@@ -1,4 +1,4 @@
-import {NumberData} from "./number";
+import {NumberData} from "./number.js";
 
 describe("number", () => {
   it("coerces to string", () => {

expressions/src/data/number.ts

@@ -1,4 +1,4 @@
-import {ExpressionDataInterface, Kind} from "./expressiondata";
+import {ExpressionDataInterface, Kind} from "./expressiondata.js";
 
 export class NumberData implements ExpressionDataInterface {
   constructor(public readonly value: number) {}

expressions/src/data/replacer.test.ts

@@ -1,9 +1,9 @@
-import {Array} from "./array";
-import {Dictionary} from "./dictionary";
-import {Null} from "./null";
-import {NumberData} from "./number";
-import {replacer} from "./replacer";
-import {StringData} from "./string";
+import {Array} from "./array.js";
+import {Dictionary} from "./dictionary.js";
+import {Null} from "./null.js";
+import {NumberData} from "./number.js";
+import {replacer} from "./replacer.js";
+import {StringData} from "./string.js";
 
 describe("replacer", () => {
   it("null", () => {

expressions/src/data/replacer.ts

@@ -1,9 +1,9 @@
-import {Array} from "./array";
-import {BooleanData} from "./boolean";
-import {Dictionary} from "./dictionary";
-import {Null} from "./null";
-import {NumberData} from "./number";
-import {StringData} from "./string";
+import {Array} from "./array.js";
+import {BooleanData} from "./boolean.js";
+import {Dictionary} from "./dictionary.js";
+import {Null} from "./null.js";
+import {NumberData} from "./number.js";
+import {StringData} from "./string.js";
 
 /**
  * Replacer can be passed to JSON.stringify to convert an ExpressionData object into plain JSON

expressions/src/data/reviver.test.ts

@@ -1,11 +1,11 @@
-import {Array} from "./array";
-import {BooleanData} from "./boolean";
-import {Dictionary} from "./dictionary";
-import {ExpressionData} from "./expressiondata";
-import {Null} from "./null";
-import {NumberData} from "./number";
-import {reviver} from "./reviver";
-import {StringData} from "./string";
+import {Array} from "./array.js";
+import {BooleanData} from "./boolean.js";
+import {Dictionary} from "./dictionary.js";
+import {ExpressionData} from "./expressiondata.js";
+import {Null} from "./null.js";
+import {NumberData} from "./number.js";
+import {reviver} from "./reviver.js";
+import {StringData} from "./string.js";
 
 describe("reviver", () => {
   const tests: {

expressions/src/data/reviver.ts

@@ -1,10 +1,10 @@
-import {Array as dArray} from "./array";
-import {BooleanData} from "./boolean";
-import {Dictionary} from "./dictionary";
-import {ExpressionData} from "./expressiondata";
-import {Null} from "./null";
-import {NumberData} from "./number";
-import {StringData} from "./string";
+import {Array as dArray} from "./array.js";
+import {BooleanData} from "./boolean.js";
+import {Dictionary} from "./dictionary.js";
+import {ExpressionData} from "./expressiondata.js";
+import {Null} from "./null.js";
+import {NumberData} from "./number.js";
+import {StringData} from "./string.js";
 
 /**
  * Reviver can be passed to `JSON.parse` to convert plain JSON into an `ExpressionData` object.

expressions/src/data/string.ts

@@ -1,4 +1,4 @@
-import {ExpressionDataInterface, Kind} from "./expressiondata";
+import {ExpressionDataInterface, Kind} from "./expressiondata.js";
 
 export class StringData implements ExpressionDataInterface {
   constructor(public readonly value: string) {}

expressions/src/errors.ts

@@ -1,4 +1,4 @@
-import {Pos, Token, tokenString} from "./lexer";
+import {Pos, Token, tokenString} from "./lexer.js";
 
 export const MAX_PARSER_DEPTH = 50;
 export const MAX_EXPRESSION_LENGTH = 21000;

expressions/src/evaluator.test.ts

@@ -1,8 +1,8 @@
-import * as data from "./data";
-import {ExpressionEvaluationError} from "./errors";
-import {Evaluator} from "./evaluator";
-import {Lexer} from "./lexer";
-import {Parser} from "./parser";
+import * as data from "./data/index.js";
+import {ExpressionEvaluationError} from "./errors.js";
+import {Evaluator} from "./evaluator.js";
+import {Lexer} from "./lexer.js";
+import {Parser} from "./parser.js";
 
 describe("evaluator", () => {
   const lexAndParse = (input: string) => {

expressions/src/evaluator.ts

@@ -10,14 +10,14 @@ import {
   Logical,
   Star,
   Unary
-} from "./ast";
-import * as data from "./data";
-import {FilteredArray} from "./filtered_array";
-import {wellKnownFunctions} from "./funcs";
-import {FunctionDefinition} from "./funcs/info";
-import {idxHelper} from "./idxHelper";
-import {TokenType} from "./lexer";
-import {equals, falsy, greaterThan, lessThan, truthy} from "./result";
+} from "./ast.js";
+import * as data from "./data/index.js";
+import {FilteredArray} from "./filtered_array.js";
+import {wellKnownFunctions} from "./funcs.js";
+import {FunctionDefinition} from "./funcs/info.js";
+import {idxHelper} from "./idxHelper.js";
+import {TokenType} from "./lexer.js";
+import {equals, falsy, greaterThan, lessThan, truthy} from "./result.js";
 
 export class Evaluator implements ExprVisitor<data.ExpressionData> {
   /**

expressions/src/filtered_array.ts

@@ -1,3 +1,3 @@
-import * as data from "./data";
+import * as data from "./data/index.js";
 
 export class FilteredArray extends data.Array {}

expressions/src/funcs.ts

@@ -1,13 +1,13 @@
-import {ErrorType, ExpressionError} from "./errors";
-import {contains} from "./funcs/contains";
-import {endswith} from "./funcs/endswith";
-import {format} from "./funcs/format";
-import {fromjson} from "./funcs/fromjson";
-import {FunctionDefinition, FunctionInfo} from "./funcs/info";
-import {join} from "./funcs/join";
-import {startswith} from "./funcs/startswith";
-import {tojson} from "./funcs/tojson";
-import {Token} from "./lexer";
+import {ErrorType, ExpressionError} from "./errors.js";
+import {contains} from "./funcs/contains.js";
+import {endswith} from "./funcs/endswith.js";
+import {format} from "./funcs/format.js";
+import {fromjson} from "./funcs/fromjson.js";
+import {FunctionDefinition, FunctionInfo} from "./funcs/info.js";
+import {join} from "./funcs/join.js";
+import {startswith} from "./funcs/startswith.js";
+import {tojson} from "./funcs/tojson.js";
+import {Token} from "./lexer.js";
 
 export type ParseContext = {
   allowUnknownKeywords: boolean;

expressions/src/funcs/contains.ts

@@ -1,6 +1,6 @@
-import {BooleanData, ExpressionData, Kind} from "../data";
-import {equals} from "../result";
-import {FunctionDefinition} from "./info";
+import {BooleanData, ExpressionData, Kind} from "../data/index.js";
+import {equals} from "../result.js";
+import {FunctionDefinition} from "./info.js";
 
 export const contains: FunctionDefinition = {
   name: "contains",

expressions/src/funcs/endswith.ts

@@ -1,6 +1,6 @@
-import {BooleanData, ExpressionData} from "../data";
-import {toUpperSpecial} from "../result";
-import {FunctionDefinition} from "./info";
+import {BooleanData, ExpressionData} from "../data/index.js";
+import {toUpperSpecial} from "../result.js";
+import {FunctionDefinition} from "./info.js";
 
 export const endswith: FunctionDefinition = {
   name: "endsWith",

expressions/src/funcs/format.test.ts

@@ -1,5 +1,5 @@
-import {Null, NumberData, StringData} from "../data";
-import {format} from "./format";
+import {Null, NumberData, StringData} from "../data/index.js";
+import {format} from "./format.js";
 
 describe("format", () => {
   it("null", () => {

expressions/src/funcs/format.ts

@@ -1,5 +1,5 @@
-import {ExpressionData, StringData} from "../data";
-import {FunctionDefinition} from "./info";
+import {ExpressionData, StringData} from "../data/index.js";
+import {FunctionDefinition} from "./info.js";
 
 export const format: FunctionDefinition = {
   name: "format",

expressions/src/funcs/fromjson.ts

@@ -1,7 +1,7 @@
-import {ExpressionData} from "../data";
-import {reviver} from "../data/reviver";
-import {ExpressionEvaluationError} from "../errors";
-import {FunctionDefinition} from "./info";
+import {ExpressionData} from "../data/index.js";
+import {reviver} from "../data/reviver.js";
+import {ExpressionEvaluationError} from "../errors.js";
+import {FunctionDefinition} from "./info.js";
 
 export const fromjson: FunctionDefinition = {
   name: "fromJson",

expressions/src/funcs/info.ts

@@ -1,4 +1,4 @@
-import {ExpressionData} from "../data";
+import {ExpressionData} from "../data/index.js";
 
 export interface FunctionInfo {
   name: string;

expressions/src/funcs/join.ts

@@ -1,5 +1,5 @@
-import {ExpressionData, Kind, StringData} from "../data";
-import {FunctionDefinition} from "./info";
+import {ExpressionData, Kind, StringData} from "../data/index.js";
+import {FunctionDefinition} from "./info.js";
 
 export const join: FunctionDefinition = {
   name: "join",

expressions/src/funcs/startswith.ts

@@ -1,6 +1,6 @@
-import {BooleanData, ExpressionData} from "../data";
-import {toUpperSpecial} from "../result";
-import {FunctionDefinition} from "./info";
+import {BooleanData, ExpressionData} from "../data/index.js";
+import {toUpperSpecial} from "../result.js";
+import {FunctionDefinition} from "./info.js";
 
 export const startswith: FunctionDefinition = {
   name: "startsWith",

expressions/src/funcs/tojson.ts

@@ -1,6 +1,6 @@
-import {ExpressionData, StringData} from "../data";
-import {replacer} from "../data/replacer";
-import {FunctionDefinition} from "./info";
+import {ExpressionData, StringData} from "../data/index.js";
+import {replacer} from "../data/replacer.js";
+import {FunctionDefinition} from "./info.js";
 
 export const tojson: FunctionDefinition = {
   name: "toJson",

expressions/src/idxHelper.ts

@@ -1,4 +1,4 @@
-import {ExpressionData} from "./data";
+import {ExpressionData} from "./data/index.js";
 
 export class idxHelper {
   public readonly str: string | undefined;

expressions/src/index.ts

@@ -1,9 +1,9 @@
-export {Expr} from "./ast";
-export {complete, CompletionItem} from "./completion";
-export {DescriptionDictionary, DescriptionPair, isDescriptionDictionary} from "./completion/descriptionDictionary";
-export * as data from "./data";
-export {ExpressionError, ExpressionEvaluationError} from "./errors";
-export {Evaluator} from "./evaluator";
-export {wellKnownFunctions} from "./funcs";
-export {Lexer, Result} from "./lexer";
-export {Parser} from "./parser";
+export {Expr} from "./ast.js";
+export {complete, CompletionItem} from "./completion.js";
+export {DescriptionDictionary, DescriptionPair, isDescriptionDictionary} from "./completion/descriptionDictionary.js";
+export * as data from "./data/index.js";
+export {ExpressionError, ExpressionEvaluationError} from "./errors.js";
+export {Evaluator} from "./evaluator.js";
+export {wellKnownFunctions} from "./funcs.js";
+export {Lexer, Result} from "./lexer.js";
+export {Parser} from "./parser.js";

expressions/src/lexer.test.ts

@@ -1,4 +1,4 @@
-import {Lexer, Token, TokenType} from "./lexer";
+import {Lexer, Token, TokenType} from "./lexer.js";
 
 describe("lexer", () => {
   const tests: {

expressions/src/lexer.ts

@@ -1,5 +1,5 @@
-import {StringData} from "./data";
-import {MAX_EXPRESSION_LENGTH} from "./errors";
+import {StringData} from "./data/index.js";
+import {MAX_EXPRESSION_LENGTH} from "./errors.js";
 
 export enum TokenType {
   UNKNOWN,

expressions/src/parser.ts

@@ -1,9 +1,20 @@
-import {Binary, ContextAccess, Expr, FunctionCall, Grouping, IndexAccess, Literal, Logical, Star, Unary} from "./ast";
-import * as data from "./data";
-import {ErrorType, ExpressionError, MAX_PARSER_DEPTH} from "./errors";
-import {ParseContext, validateFunction} from "./funcs";
-import {FunctionInfo} from "./funcs/info";
-import {Token, TokenType} from "./lexer";
+import {
+  Binary,
+  ContextAccess,
+  Expr,
+  FunctionCall,
+  Grouping,
+  IndexAccess,
+  Literal,
+  Logical,
+  Star,
+  Unary
+} from "./ast.js";
+import * as data from "./data/index.js";
+import {ErrorType, ExpressionError, MAX_PARSER_DEPTH} from "./errors.js";
+import {ParseContext, validateFunction} from "./funcs.js";
+import {FunctionInfo} from "./funcs/info.js";
+import {Token, TokenType} from "./lexer.js";
 
 export class Parser {
   private extContexts: Map<string, boolean>;

expressions/src/result.test.ts

@@ -1,5 +1,5 @@
-import {BooleanData, ExpressionData, NumberData, StringData} from "./data";
-import {coerceTypes, toUpperSpecial} from "./result";
+import {BooleanData, ExpressionData, NumberData, StringData} from "./data/index.js";
+import {coerceTypes, toUpperSpecial} from "./result.js";
 
 describe("coerceTypes", () => {
   const tests: {

expressions/src/result.ts

@@ -1,4 +1,4 @@
-import * as data from "./data";
+import * as data from "./data/index.js";
 
 export function falsy(d: data.ExpressionData): boolean {
   switch (d.kind) {

expressions/src/xlang.test.ts

@@ -1,14 +1,14 @@
 import * as fs from "fs";
 import * as path from "path";
-import {Expr} from "./ast";
-import * as data from "./data";
-import {kindStr} from "./data/expressiondata";
-import {replacer} from "./data/replacer";
-import {reviver} from "./data/reviver";
-import {ExpressionError} from "./errors";
-import {Evaluator} from "./evaluator";
-import {Lexer, Result} from "./lexer";
-import {Parser} from "./parser";
+import {Expr} from "./ast.js";
+import * as data from "./data/index.js";
+import {kindStr} from "./data/expressiondata.js";
+import {replacer} from "./data/replacer.js";
+import {reviver} from "./data/reviver.js";
+import {ExpressionError} from "./errors.js";
+import {Evaluator} from "./evaluator.js";
+import {Lexer, Result} from "./lexer.js";
+import {Parser} from "./parser.js";
 
 interface TestResult {
   value: data.ExpressionData;

expressions/tsconfig.build.json

@@ -2,9 +2,12 @@
   "exclude": ["./src/**/*.test.ts"],
   "extends": "./tsconfig.json",
   "compilerOptions": {
+    "module": "node16",
+    "moduleResolution": "node16",
     "declaration": true,
     "declarationMap": true,
     "noEmit": false,
-    "outDir": "./dist"
+    "outDir": "./dist",
+    "skipLibCheck": true
   }
 }

languageserver/README.md

@@ -10,6 +10,14 @@ The [package](https://www.npmjs.com/package/@actions/languageserver) contains Ty
 npm install @actions/languageserver
 ```
 
+To install the language server as a standalone CLI:
+
+```bash
+npm install -g @actions/languageserver
+```
+
+This makes the `actions-languageserver` command available globally.
+
 ## Usage
 
 ### Basic usage using `vscode-languageserver-node`
@@ -92,6 +100,150 @@ const clientOptions: LanguageClientOptions = {
 const client = new LanguageClient("actions-language", "GitHub Actions Language Server", serverOptions, clientOptions);
 ```
 
+### Standalone CLI
+
+After installing globally, you can run the language server directly:
+
+```bash
+actions-languageserver --stdio
+```
+
+This starts the language server using stdio transport, which is the standard way for editors to communicate with language servers.
+
+### In Neovim
+
+#### 1. Install the language server
+
+```bash
+npm install -g @actions/languageserver
+```
+
+#### 2. Set up filetype detection
+
+Add this to your `init.lua` to detect GitHub Actions workflow files:
+
+```lua
+vim.filetype.add({
+  pattern = {
+    [".*/%.github/workflows/.*%.ya?ml"] = "yaml.ghactions",
+  },
+})
+```
+
+This sets the filetype to `yaml.ghactions` for YAML files in `.github/workflows/`, allowing you to keep separate YAML LSP configurations if needed.
+
+#### 3. Create the LSP configuration
+
+As of Neovim 0.11+ you can add this configuration in `~/.config/nvim/lsp/actionsls.lua`:
+
+```lua
+local function get_github_token()
+  local handle = io.popen("gh auth token 2>/dev/null")
+  if not handle then return nil end
+  local token = handle: read("*a"):gsub("%s+", "")
+  handle:close()
+  return token ~= "" and token or nil
+end
+
+local function parse_github_remote(url)
+  if not url or url == "" then return nil end
+
+  -- SSH format: git@github.com:owner/repo.git
+  local owner, repo = url:match("git@github%.com:([^/]+)/([^/%.]+)")
+  if owner and repo then
+    return owner, repo: gsub("%.git$", "")
+  end
+
+  -- HTTPS format: https://github.com/owner/repo.git
+  owner, repo = url:match("github%.com/([^/]+)/([^/%.]+)")
+  if owner and repo then
+    return owner, repo:gsub("%.git$", "")
+  end
+
+  return nil
+end
+
+local function get_repo_info(owner, repo)
+  local cmd = string.format(
+    "gh repo view %s/%s --json id,owner --template '{{.id}}\t{{.owner.type}}' 2>/dev/null",
+    owner,
+    repo
+  )
+  local handle = io.popen(cmd)
+  if not handle then return nil end
+  local result = handle: read("*a"):gsub("%s+$", "")
+  handle:close()
+
+  local id, owner_type = result:match("^(%d+)\t(.+)$")
+  if id then
+    return {
+      id = tonumber(id),
+      organizationOwned = owner_type == "Organization",
+    }
+  end
+  return nil
+end
+
+local function get_repos_config()
+  local handle = io.popen("git rev-parse --show-toplevel 2>/dev/null")
+  if not handle then return nil end
+  local git_root = handle: read("*a"):gsub("%s+", "")
+  handle:close()
+
+  if git_root == "" then return nil end
+
+  handle = io.popen("git remote get-url origin 2>/dev/null")
+  if not handle then return nil end
+  local remote_url = handle:read("*a"):gsub("%s+", "")
+  handle:close()
+
+  local owner, name = parse_github_remote(remote_url)
+  if not owner or not name then return nil end
+
+  local info = get_repo_info(owner, name)
+
+  return {
+    {
+      id = info and info.id or 0,
+      owner = owner,
+      name = name,
+      organizationOwned = info and info.organizationOwned or false,
+      workspaceUri = "file://" .. git_root,
+    },
+  }
+end
+
+return {
+  cmd = { "actions-languageserver", "--stdio" },
+  filetypes = { "yaml.ghactions" },
+  root_markers = { ".git" },
+  init_options = {
+    -- Optional: provide a GitHub token and repo context for added functionality
+    -- (e.g., repository-specific completions)
+    sessionToken = get_github_token(),
+    repos = get_repos_config(),
+  },
+}
+```
+
+#### 4. Enable the LSP
+
+Add to your `init.lua`:
+
+```lua
+vim.lsp.enable('actionsls')
+```
+
+#### 5. Verify it's working
+
+Open any `.github/workflows/*.yml` file and run:
+
+```vim
+:checkhealth vim.lsp
+```
+
+You should see `actionsls` in the list of attached clients.
+
 ## Contributing
 
 See [CONTRIBUTING.md](../CONTRIBUTING.md) at the root of the repository for general guidelines and recommendations.
@@ -110,6 +262,27 @@ or to watch for changes
 npm run watch
 ```
 
+### Running the language server locally
+
+After running
+
+```bash
+npm run build:cli
+npm link
+```
+
+`actions-languageserver` will be available globally. You can start it with:
+
+```bash
+actions-languageserver --stdio
+```
+
+Once linked you can also watch for changes and rebuild automatically:
+
+```bash
+npm run watch:cli
+```
+
 ### Test
 
 ```bash

languageserver/bin/actions-languageserver

@@ -0,0 +1,2 @@
+#!/usr/bin/env node
+import "../dist/cli.bundle.cjs";

languageserver/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/languageserver",
-  "version": "0.3.25",
+  "version": "0.3.30",
   "description": "Language server for GitHub Actions",
   "license": "MIT",
   "type": "module",
@@ -31,7 +31,8 @@
     "url": "https://github.com/actions/languageservices"
   },
   "scripts": {
-    "build": "tsc --build tsconfig.build.json",
+    "build": "tsc --build tsconfig.build.json && npm run build:cli",
+    "build:cli": "esbuild src/index.ts --bundle --platform=node --format=cjs --outfile=dist/cli.bundle.cjs",
     "clean": "rimraf dist",
     "format": "prettier --write '**/*.ts'",
     "format-check": "prettier --check '**/*.ts'",
@@ -40,11 +41,15 @@
     "prepublishOnly": "npm run build && npm run test",
     "test": "NODE_OPTIONS=\"--experimental-vm-modules\" jest",
     "test-watch": "NODE_OPTIONS=\"--experimental-vm-modules\" jest --watch",
-    "watch": "tsc --build tsconfig.build.json --watch"
+    "watch": "tsc --build tsconfig.build.json --watch",
+    "watch:cli": "esbuild src/index.ts --bundle --platform=node --format=cjs --outfile=dist/cli.bundle.cjs --watch"
+  },
+  "bin": {
+    "actions-languageserver": "./bin/actions-languageserver"
   },
   "dependencies": {
-    "@actions/languageservice": "^0.3.25",
-    "@actions/workflow-parser": "^0.3.25",
+    "@actions/languageservice": "^0.3.30",
+    "@actions/workflow-parser": "^0.3.30",
     "@octokit/rest": "^21.1.1",
     "@octokit/types": "^9.0.0",
     "vscode-languageserver": "^8.0.2",
@@ -55,12 +60,14 @@
     "node": ">= 18"
   },
   "files": [
-    "dist/**/*"
+    "dist/**/*",
+    "bin/**/*"
   ],
   "devDependencies": {
     "@types/jest": "^29.0.3",
     "@typescript-eslint/eslint-plugin": "^5.56.0",
     "@typescript-eslint/parser": "^5.56.0",
+    "esbuild": "^0.27.1",
     "eslint": "^8.36.0",
     "eslint-config-prettier": "^8.8.0",
     "eslint-plugin-prettier": "^4.2.1",

languageserver/src/connection.ts

@@ -1,4 +1,4 @@
-import {documentLinks, hover, validate, ValidationConfig} from "@actions/languageservice";
+import {documentLinks, getInlayHints, hover, validate, ValidationConfig} from "@actions/languageservice";
 import {registerLogger, setLogLevel} from "@actions/languageservice/log";
 import {clearCache, clearCacheEntry} from "@actions/languageservice/utils/workflow-cache";
 import {Octokit} from "@octokit/rest";
@@ -12,6 +12,8 @@ import {
   HoverParams,
   InitializeParams,
   InitializeResult,
+  InlayHint,
+  InlayHintParams,
   TextDocumentIdentifier,
   TextDocumentPositionParams,
   TextDocuments,
@@ -72,7 +74,8 @@ export function initConnection(connection: Connection) {
         hoverProvider: true,
         documentLinkProvider: {
           resolveProvider: false
-        }
+        },
+        inlayHintProvider: true
       }
     };
 
@@ -158,6 +161,12 @@ export function initConnection(connection: Connection) {
     return documentLinks(getDocument(documents, textDocument), repoContext?.workspaceUri);
   });
 
+  connection.languages.inlayHint.on(async ({textDocument}: InlayHintParams): Promise<InlayHint[] | null> => {
+    return timeOperation("inlayHints", () => {
+      return getInlayHints(getDocument(documents, textDocument));
+    });
+  });
+
   // Make the text document manager listen on the connection
   // for open, change and close text document events
   documents.listen(connection);

languageservice/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@actions/languageservice",
-  "version": "0.3.25",
+  "version": "0.3.30",
   "description": "Language service for GitHub Actions",
   "license": "MIT",
   "type": "module",
@@ -47,8 +47,8 @@
     "watch": "tsc --build tsconfig.build.json --watch"
   },
   "dependencies": {
-    "@actions/expressions": "^0.3.25",
-    "@actions/workflow-parser": "^0.3.25",
+    "@actions/expressions": "^0.3.30",
+    "@actions/workflow-parser": "^0.3.30",
     "vscode-languageserver-textdocument": "^1.0.7",
     "vscode-languageserver-types": "^3.17.2",
     "vscode-uri": "^3.0.8",

languageservice/src/action.test.ts

@@ -1,4 +1,4 @@
-import {actionIdentifier, parseActionReference as parse} from "./action";
+import {actionIdentifier, parseActionReference as parse} from "./action.js";
 
 describe("parseActionReference", () => {
   it("basic action", () => {

languageservice/src/complete.expressions.test.ts

@@ -1,13 +1,13 @@
 /* eslint-disable @typescript-eslint/no-non-null-assertion */
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {CompletionItem, CompletionItemKind} from "vscode-languageserver-types";
-import {complete, getExpressionInput} from "./complete";
-import {ContextProviderConfig} from "./context-providers/config";
-import {registerLogger} from "./log";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {TestLogger} from "./test-utils/logger";
-import {testFileProvider} from "./test-utils/test-file-provider";
-import {clearCache} from "./utils/workflow-cache";
+import {complete, getExpressionInput} from "./complete.js";
+import {ContextProviderConfig} from "./context-providers/config.js";
+import {registerLogger} from "./log.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {testFileProvider} from "./test-utils/test-file-provider.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 const contextProviderConfig: ContextProviderConfig = {
   getContext: (context: string) => {
@@ -1110,7 +1110,7 @@ jobs:
 `;
 
       const result = await complete(...getPositionFromCursor(input), {contextProviderConfig});
-      expect(result.map(x => x.label)).toEqual(["container", "services", "status"]);
+      expect(result.map(x => x.label)).toEqual(["check_run_id", "container", "services", "status"]);
     });
 
     it("job context is suggested within a job output", async () => {

languageservice/src/complete.multiline-if.test.ts

@@ -1,7 +1,7 @@
-import {complete} from "./complete";
+import {complete} from "./complete.js";
 import {TextDocument} from "vscode-languageserver-textdocument";
-import {clearCache} from "./utils/workflow-cache";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
+import {clearCache} from "./utils/workflow-cache.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
 
 beforeEach(() => {
   clearCache();

languageservice/src/complete.reusable-workflows.test.ts

@@ -1,8 +1,8 @@
 import {CompletionItem, MarkupContent} from "vscode-languageserver-types";
-import {complete} from "./complete";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {testFileProvider} from "./test-utils/test-file-provider";
-import {clearCache} from "./utils/workflow-cache";
+import {complete} from "./complete.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {testFileProvider} from "./test-utils/test-file-provider.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 function mapResult(result: CompletionItem[]) {
   return result.map(x => {

languageservice/src/complete.test.ts

@@ -1,11 +1,11 @@
 /* eslint-disable @typescript-eslint/no-non-null-assertion */
 import {MarkupContent, TextEdit} from "vscode-languageserver-types";
-import {complete} from "./complete";
-import {registerLogger} from "./log";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {TestLogger} from "./test-utils/logger";
-import {clearCache} from "./utils/workflow-cache";
-import {ValueProviderConfig, ValueProviderKind} from "./value-providers/config";
+import {complete} from "./complete.js";
+import {registerLogger} from "./log.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {clearCache} from "./utils/workflow-cache.js";
+import {ValueProviderConfig, ValueProviderKind} from "./value-providers/config.js";
 
 registerLogger(new TestLogger());
 
@@ -19,9 +19,12 @@ describe("completion", () => {
     const result = await complete(...getPositionFromCursor(input));
 
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(12);
+    // 12 runner labels + 2 escape hatches (switch to list, switch to full syntax)
+    expect(result.length).toEqual(14);
     const labels = result.map(x => x.label);
     expect(labels).toContain("macos-latest");
+    expect(labels).toContain("(switch to list)");
+    expect(labels).toContain("(switch to mapping)");
   });
 
   it("needs", async () => {
@@ -44,7 +47,7 @@ jobs:
     const result = await complete(...getPositionFromCursor(input));
 
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(9);
+    expect(result.length).toEqual(13);
     expect(result[0].label).toEqual("concurrency");
   });
 
@@ -70,7 +73,7 @@ jobs:
     |`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(21);
+    expect(result.length).toEqual(30);
   });
 
   it("string definition completion in sequence", async () => {
@@ -95,6 +98,7 @@ jobs:
   release:
     types: |`;
     const result = await complete(...getPositionFromCursor(input));
+    // Expect string values plus escape hatch to switch to list form
     expect(result.map(x => x.label)).toEqual([
       "created",
       "deleted",
@@ -102,7 +106,8 @@ jobs:
       "prereleased",
       "published",
       "released",
-      "unpublished"
+      "unpublished",
+      "(switch to list)"
     ]);
   });
 
@@ -190,8 +195,11 @@ jobs:
     const result = await complete(...getPositionFromCursor(input), {valueProviderConfig: config});
 
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(1);
+    // Custom value plus escape hatches for list and full syntax
+    expect(result.length).toEqual(3);
     expect(result[0].label).toEqual("my-custom-label");
+    expect(result.map(x => x.label)).toContain("(switch to list)");
+    expect(result.map(x => x.label)).toContain("(switch to mapping)");
   });
 
   it("custom value providers for sequences", async () => {
@@ -212,7 +220,9 @@ jobs:
     expect(result[0].label).toEqual("my-custom-label");
   });
 
-  it("does not show parent mapping sibling keys", async () => {
+  it("does not show mapping keys or parent sibling keys in Key mode", async () => {
+    // At `container: |`, the scalar form is a string with no constants.
+    // Mapping keys should NOT be shown inline - but escape hatch to full syntax IS shown.
     const input = `on: push
 jobs:
   build:
@@ -220,20 +230,21 @@ jobs:
     runs-on: ubuntu-latest`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(6);
-    // Should not contain other top-level job keys like `if` and `runs-on`
-    expect(result.map(x => x.label)).not.toContain("if");
-    expect(result.map(x => x.label)).not.toContain("runs-on");
+    // Only escape hatch to full syntax (container has mapping form but no sequence)
+    expect(result.map(x => x.label)).toEqual(["(switch to mapping)"]);
   });
 
-  it("shows mapping keys within a new map ", async () => {
+  it("does not show mapping keys in Key mode when structure is uncommitted", async () => {
+    // At `concurrency: |`, user is in Key mode but hasn't committed to a structure.
+    // The scalar form is a string with no constants, so no scalar completions.
+    // But escape hatch to full syntax IS shown as a way out.
     const input = `on: push
 jobs:
   build:
     concurrency: |`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result.map(x => x.label).sort()).toEqual(["cancel-in-progress", "group"]);
+    expect(result.map(x => x.label)).toEqual(["(switch to mapping)"]);
   });
 
   it("job key", async () => {
@@ -243,7 +254,7 @@ jobs:
     runs-|`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result).toHaveLength(21);
+    expect(result).toHaveLength(30);
   });
 
   it("job key with comment afterwards", async () => {
@@ -254,7 +265,7 @@ jobs:
   #`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result).toHaveLength(21);
+    expect(result).toHaveLength(30);
   });
 
   it("job key with other values afterwards", async () => {
@@ -266,7 +277,10 @@ jobs:
     concurrency: 'group-name'`;
     const result = await complete(...getPositionFromCursor(input));
     expect(result).not.toBeUndefined();
-    expect(result).toHaveLength(20);
+    // Verify we get job-level completions, but concurrency is already present so excluded
+    expect(result.length).toBeGreaterThan(20);
+    expect(result.some(x => x.label === "runs-on")).toBe(true);
+    expect(result.some(x => x.label === "concurrency")).toBe(false);
   });
 
   it("step key without space after colon", async () => {
@@ -335,7 +349,9 @@ jobs:
     - uses: actions/checkout@v2
 `;
     const result = await complete(...getPositionFromCursor(input));
-    expect(result).toHaveLength(17);
+    // Verify we get job-level completions including runs-on variants
+    expect(result.length).toBeGreaterThan(20);
+    expect(result.some(x => x.label === "steps")).toBe(true);
   });
 
   it("complete from behind a colon will replace it", async () => {
@@ -348,7 +364,8 @@ jobs:
     - uses: actions/checkout@v2
 `;
     const result = await complete(...getPositionFromCursor(input));
-    expect(result).toHaveLength(17);
+    // Verify we get job-level completions
+    expect(result.length).toBeGreaterThan(20);
     const textEdit = result[0].textEdit as TextEdit;
     expect(textEdit.range).toEqual({
       start: {line: 5, character: 4},
@@ -447,8 +464,9 @@ jobs:
         "timeout-minutes: "
       ]);
 
-      // One-of
-      expect(result.filter(x => x.label === "concurrency").map(x => x.textEdit?.newText)).toEqual(["concurrency: "]);
+      // One-of (scalar variant)
+      const concurrencyScalar = result.find(x => x.label === "concurrency" && x.detail === undefined);
+      expect(concurrencyScalar?.textEdit?.newText).toEqual("concurrency: ");
     });
 
     it("custom indentation", async () => {
@@ -470,20 +488,21 @@ jobs:
         "timeout-minutes: "
       ]);
 
-      // One-of
-      expect(result.filter(x => x.label === "concurrency").map(x => x.textEdit?.newText)).toEqual(["concurrency: "]);
+      // One-of (scalar variant)
+      const concurrencyScalar = result.find(x => x.label === "concurrency" && x.detail === undefined);
+      expect(concurrencyScalar?.textEdit?.newText).toEqual("concurrency: ");
     });
   });
 
-  it("adds a new line and indentation for mapping keys when the key is given", async () => {
+  it("does not show mapping keys in Key mode for one-of with mapping variant", async () => {
+    // At `concurrency: |`, mapping keys should NOT be shown.
+    // Users who want the mapping form should use `concurrency (full syntax)` at parent level.
     const input = "concurrency: |";
 
     const result = await complete(...getPositionFromCursor(input));
 
-    expect(result.filter(x => x.label === "cancel-in-progress").map(x => x.textEdit?.newText)).toEqual([
-      "\n  cancel-in-progress: "
-    ]);
-    expect(result.filter(x => x.label === "group").map(x => x.textEdit?.newText)).toEqual(["\n  group: "]);
+    expect(result.filter(x => x.label === "cancel-in-progress")).toEqual([]);
+    expect(result.filter(x => x.label === "group")).toEqual([]);
   });
 
   it("does not add new line if no key in line", async () => {
@@ -494,12 +513,15 @@ jobs:
     expect(result.filter(x => x.label === "run-name").map(x => x.textEdit?.newText)).toEqual(["run-name: "]);
   });
 
-  it("adds new line for nested mapping", async () => {
+  it("does not show mapping keys when user has started typing a scalar value", async () => {
+    // User typed `workflow_dispatch: in` - they've committed to a scalar value
+    // Should not show mapping keys like `inputs`
     const input = "on:\n  workflow_dispatch: in|";
 
     const result = await complete(...getPositionFromCursor(input));
 
-    expect(result.filter(x => x.label === "inputs").map(x => x.textEdit?.newText)).toEqual(["\n  inputs:\n    "]);
+    // No mapping keys should be shown since user started typing a scalar
+    expect(result.filter(x => x.label === "inputs")).toEqual([]);
   });
 
   it("adds : for one-of", async () => {
@@ -507,14 +529,347 @@ jobs:
 
     const result = await complete(...getPositionFromCursor(input));
 
-    expect(result.filter(x => x.label === "types").map(x => x.textEdit?.newText)).toEqual(["types: "]);
+    // Scalar variant inserts "types: "
+    const scalarVariant = result.find(x => x.label === "types" && x.detail === undefined);
+    expect(scalarVariant?.textEdit?.newText).toEqual("types: ");
   });
 
-  it("does not add : for one-of in key mode", async () => {
+  it("does not show mapping keys for one-of when user has typed a scalar value", async () => {
+    // User typed `check_run: ty` - they've committed to scalar form
+    // The only valid value for check_run scalar is null, so no completions
     const input = "on:\n  check_run: ty|";
 
     const result = await complete(...getPositionFromCursor(input));
 
-    expect(result.filter(x => x.label === "types").map(x => x.textEdit?.newText)).toEqual(["types"]);
+    // check_run's scalar form only accepts null, so typing anything should show no completions
+    // (we don't show mapping keys like `types` anymore - user should use check_run with detail "full syntax" instead)
+    expect(result.filter(x => x.label === "types")).toEqual([]);
+  });
+
+  it("shows only scalar options for one-of in Key mode when user hasn't committed to a type", async () => {
+    // At `permissions: |` user hasn't typed anything yet - show only scalar options
+    // Mapping keys are NOT shown because they would require a newline
+    // Users who want the mapping form can use `permissions (full syntax)` at the parent level
+    const input = "on: push\npermissions: |";
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // String values (read-all, write-all) should be available
+    expect(result.filter(x => x.label === "read-all").map(x => x.textEdit?.newText)).toEqual(["read-all"]);
+    expect(result.filter(x => x.label === "write-all").map(x => x.textEdit?.newText)).toEqual(["write-all"]);
+
+    // Mapping keys should NOT be shown - they require a newline which is confusing inline
+    expect(result.filter(x => x.label === "actions")).toEqual([]);
+    expect(result.filter(x => x.label === "contents")).toEqual([]);
+  });
+
+  it("filters to scalar options when user has started typing a scalar", async () => {
+    // User typed `permissions: r` - they've committed to scalar form
+    const input = "on: push\npermissions: r|";
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // Only scalar values should be shown (filtering on 'r')
+    expect(result.some(x => x.label === "read-all")).toBe(true);
+    // Mapping keys should NOT be shown
+    expect(result.filter(x => x.label === "actions")).toEqual([]);
+    expect(result.filter(x => x.label === "contents")).toEqual([]);
+  });
+
+  it("shows both simple and full syntax for null+mapping one-of", async () => {
+    // check_run is a one-of: [null, mapping]. Show both:
+    // - check_run (simple, just the key with colon)
+    // - check_run with detail "full syntax" (ready to add mapping keys)
+    const input = "on:\n  |";
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // Should have both check_run (scalar) and check_run with detail "full syntax"
+    const checkRunVariants = result.filter(x => x.label === "check_run");
+    expect(checkRunVariants.some(x => x.detail === undefined)).toBe(true);
+    expect(checkRunVariants.some(x => x.detail === "full syntax")).toBe(true);
+  });
+
+  it("shows all three variants for scalar+sequence+mapping one-of", async () => {
+    // runs-on is a one-of: [string, sequence, mapping]
+    const input = `on: push
+jobs:
+  build:
+    |`;
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // Should have runs-on (scalar), runs-on with detail "list", and runs-on with detail "full syntax"
+    const runsOnVariants = result.filter(x => x.label === "runs-on");
+    expect(runsOnVariants.length).toBe(3);
+    expect(runsOnVariants.some(x => x.detail === undefined)).toBe(true);
+    expect(runsOnVariants.some(x => x.detail === "list")).toBe(true);
+    expect(runsOnVariants.some(x => x.detail === "full syntax")).toBe(true);
+  });
+
+  it("generates correct insertText for one-of variants in parent mode", async () => {
+    // runs-on is a one-of: [string, sequence, mapping]
+    const input = `on: push
+jobs:
+  build:
+    |`;
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    const runsOnVariants = result.filter(x => x.label === "runs-on");
+
+    // Scalar: just key with colon and space
+    expect(runsOnVariants.find(x => x.detail === undefined)?.textEdit?.newText).toEqual("runs-on: ");
+
+    // Sequence: key with colon, newline, and list item
+    expect(runsOnVariants.find(x => x.detail === "list")?.textEdit?.newText).toEqual("runs-on:\n  - ");
+
+    // Mapping: key with colon, newline, and indentation for nested keys
+    expect(runsOnVariants.find(x => x.detail === "full syntax")?.textEdit?.newText).toEqual("runs-on:\n  ");
+  });
+
+  it("generates correct insertText for one-of variants in parent mode", async () => {
+    // concurrency is a one-of: [string, mapping] - testing parent mode (inside mapping)
+    // At `concurrency:\n  |`, user HAS committed to mapping structure, so mapping keys are shown
+    const input = "concurrency:\n  |";
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // In parent mode: just key + colon + space (no leading newline)
+    expect(result.find(x => x.label === "group")?.textEdit?.newText).toEqual("group: ");
+
+    // Boolean in parent mode (cancel-in-progress): key + colon + space
+    expect(result.find(x => x.label === "cancel-in-progress")?.textEdit?.newText).toEqual("cancel-in-progress: ");
+  });
+
+  it("uses sortText for ordering qualified one-of variants", async () => {
+    // runs-on has multiple structural types, so variants need sorting
+    const input = `on: push
+jobs:
+  build:
+    |`;
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    const runsOnVariants = result.filter(x => x.label === "runs-on");
+
+    // Scalar: no sortText needed (sorts naturally first)
+    expect(runsOnVariants.find(x => x.detail === undefined)?.sortText).toBeUndefined();
+
+    // Sequence and mapping: sortText controls ordering
+    expect(runsOnVariants.find(x => x.detail === "list")?.sortText).toEqual("runs-on 1");
+    expect(runsOnVariants.find(x => x.detail === "full syntax")?.sortText).toEqual("runs-on 2");
+  });
+
+  it("scalar event completion inserts inline without newline", async () => {
+    // At `on: |` user is completing the value for 'on' key
+    // Scalar events like `push`, `check_run` should insert inline
+    const input = "on: |";
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // Scalar forms should NOT have newline - they insert inline
+    const push = result.find(x => x.label === "push");
+    expect(push?.textEdit?.newText).toEqual("push");
+
+    const checkRun = result.find(x => x.label === "check_run" && x.detail === undefined);
+    expect(checkRun?.textEdit?.newText).toEqual("check_run");
+
+    // Full syntax form should NOT be shown in Key mode - it requires a newline
+    // which is confusing when typing inline. Users who want the mapping form
+    // can use `on (full syntax)` at the parent level.
+    expect(result.find(x => x.label === "check_run" && x.detail === "full syntax")).toBeUndefined();
+  });
+
+  it("filters to sequence options when user has started a sequence", async () => {
+    // User started a sequence with `- ` syntax - they've committed to sequence form
+    const input = `on: push
+jobs:
+  build:
+    runs-on:
+      - |`;
+
+    const result = await complete(...getPositionFromCursor(input));
+
+    // Should show runner labels (sequence item values)
+    expect(result.some(x => x.label === "ubuntu-latest")).toBe(true);
+    expect(result.some(x => x.label === "macos-latest")).toBe(true);
+
+    // Should NOT show mapping keys like `group` or `labels` (those are for full syntax)
+    expect(result.filter(x => x.label === "group")).toEqual([]);
+    expect(result.filter(x => x.label === "labels")).toEqual([]);
+  });
+
+  describe("escape hatch completions", () => {
+    it("runs-on shows switch to list and full syntax", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Should have escape hatches at the end
+      const switchToList = result.find(x => x.label === "(switch to list)");
+      const switchToFull = result.find(x => x.label === "(switch to mapping)");
+
+      expect(switchToList).toBeDefined();
+      expect(switchToFull).toBeDefined();
+
+      // Escape hatches should sort last
+      expect(switchToList!.sortText).toEqual("zzz_switch_1");
+      expect(switchToFull!.sortText).toEqual("zzz_switch_2");
+
+      // Escape hatches should have textEdit that restructures the YAML
+      const listEdit = switchToList!.textEdit as TextEdit;
+      const fullEdit = switchToFull!.textEdit as TextEdit;
+
+      expect(listEdit.newText).toEqual("runs-on:\n  - ");
+      expect(fullEdit.newText).toEqual("runs-on:\n  ");
+
+      // TextEdit range should cover from key start to cursor position
+      expect(listEdit.range.start).toEqual({line: 3, character: 4});
+      expect(fullEdit.range.start).toEqual({line: 3, character: 4});
+    });
+
+    it("permissions shows only switch to full syntax (no sequence form)", async () => {
+      const input = `on: push
+permissions: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Should have full syntax escape hatch but NOT list (permissions has no sequence form)
+      expect(result.some(x => x.label === "(switch to mapping)")).toBe(true);
+      expect(result.some(x => x.label === "(switch to list)")).toBe(false);
+    });
+
+    it("escape hatches are not shown when value is non-empty", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on: ubuntu-|`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // User has started typing a scalar value, no escape hatches
+      expect(result.some(x => x.label === "(switch to list)")).toBe(false);
+      expect(result.some(x => x.label === "(switch to mapping)")).toBe(false);
+    });
+
+    it("escape hatches are not shown when inside a sequence", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on:
+      - |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // User is already in sequence form, no escape hatches
+      expect(result.some(x => x.label === "(switch to list)")).toBe(false);
+      expect(result.some(x => x.label === "(switch to mapping)")).toBe(false);
+    });
+
+    it("escape hatches are not shown when inside a mapping", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on:
+      group: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // User is in mapping form completing a value, no escape hatches for the parent
+      expect(result.some(x => x.label === "(switch to list)")).toBe(false);
+      expect(result.some(x => x.label === "(switch to mapping)")).toBe(false);
+    });
+
+    it("escape hatches ARE shown even when no scalar completions exist", async () => {
+      // concurrency: | has no scalar constants, but escape hatch provides a way out
+      const input = `on: push
+jobs:
+  build:
+    concurrency: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Escape hatch to mapping should be available even with no scalar completions
+      expect(result.map(x => x.label)).toEqual(["(switch to mapping)"]);
+    });
+
+    it("pure mapping type (strategy) shows switch to mapping", async () => {
+      const input = `on: push
+jobs:
+  build:
+    strategy: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      expect(result.some(x => x.label === "(switch to mapping)")).toBe(true);
+    });
+
+    it("pure sequence type (steps) shows switch to list", async () => {
+      const input = `on: push
+jobs:
+  build:
+    steps: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      expect(result.some(x => x.label === "(switch to list)")).toBe(true);
+    });
+
+    it("selecting switch to list restructures YAML", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      const switchToList = result.find(x => x.label === "(switch to list)");
+      const textEdit = switchToList!.textEdit as TextEdit;
+
+      // Applying this edit to "runs-on: " should produce "runs-on:\n  - "
+      expect(textEdit.newText).toEqual("runs-on:\n  - ");
+    });
+  });
+
+  describe("runs-on mapping syntax", () => {
+    it("provides label completions for labels as scalar", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on:
+      labels: |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Should show runner labels
+      expect(result.some(x => x.label === "ubuntu-latest")).toBe(true);
+      expect(result.some(x => x.label === "macos-latest")).toBe(true);
+      expect(result.some(x => x.label === "self-hosted")).toBe(true);
+    });
+
+    it("provides label completions for labels as sequence item", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on:
+      labels:
+        - |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Should show runner labels
+      expect(result.some(x => x.label === "ubuntu-latest")).toBe(true);
+      expect(result.some(x => x.label === "macos-latest")).toBe(true);
+      expect(result.some(x => x.label === "self-hosted")).toBe(true);
+    });
+
+    it("excludes already used labels in sequence", async () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on:
+      labels:
+        - ubuntu-latest
+        - |`;
+      const result = await complete(...getPositionFromCursor(input));
+
+      // Should NOT show ubuntu-latest since it's already in the list
+      expect(result.some(x => x.label === "ubuntu-latest")).toBe(false);
+      // But should show other labels
+      expect(result.some(x => x.label === "macos-latest")).toBe(true);
+    });
   });
 });

languageservice/src/complete.ts

@@ -2,6 +2,8 @@ import {complete as completeExpression, DescriptionDictionary} from "@actions/ex
 import {CompletionItem as ExpressionCompletionItem} from "@actions/expressions/completion";
 import {isBasicExpression, isSequence, isString} from "@actions/workflow-parser";
 import {ErrorPolicy} from "@actions/workflow-parser/model/convert";
+import {DefinitionType} from "@actions/workflow-parser/templates/schema/definition-type";
+import {OneOfDefinition} from "@actions/workflow-parser/templates/schema/one-of-definition";
 import {OPEN_EXPRESSION} from "@actions/workflow-parser/templates/template-constants";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/index";
 import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
@@ -9,22 +11,23 @@ import {TokenRange} from "@actions/workflow-parser/templates/tokens/token-range"
 import {TokenType} from "@actions/workflow-parser/templates/tokens/types";
 import {File} from "@actions/workflow-parser/workflows/file";
 import {FileProvider} from "@actions/workflow-parser/workflows/file-provider";
+import {getWorkflowSchema} from "@actions/workflow-parser/workflows/workflow-schema";
 import {Position, TextDocument} from "vscode-languageserver-textdocument";
 import {CompletionItem, CompletionItemKind, CompletionItemTag, Range, TextEdit} from "vscode-languageserver-types";
-import {ContextProviderConfig} from "./context-providers/config";
-import {getContext, Mode} from "./context-providers/default";
-import {getWorkflowContext, WorkflowContext} from "./context/workflow-context";
-import {validatorFunctions} from "./expression-validation/functions";
-import {error} from "./log";
-import {isPotentiallyExpression} from "./utils/expression-detection";
-import {findToken} from "./utils/find-token";
-import {guessIndentation} from "./utils/indentation-guesser";
-import {mapRange} from "./utils/range";
-import {isPlaceholder, transform} from "./utils/transform";
-import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache";
-import {Value, ValueProviderConfig} from "./value-providers/config";
-import {defaultValueProviders} from "./value-providers/default";
-import {DefinitionValueMode, definitionValues} from "./value-providers/definition";
+import {ContextProviderConfig} from "./context-providers/config.js";
+import {getContext, Mode} from "./context-providers/default.js";
+import {getWorkflowContext, WorkflowContext} from "./context/workflow-context.js";
+import {validatorFunctions} from "./expression-validation/functions.js";
+import {error} from "./log.js";
+import {isPotentiallyExpression} from "./utils/expression-detection.js";
+import {findToken} from "./utils/find-token.js";
+import {guessIndentation} from "./utils/indentation-guesser.js";
+import {mapRange} from "./utils/range.js";
+import {isPlaceholder, transform} from "./utils/transform.js";
+import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache.js";
+import {Value, ValueProviderConfig} from "./value-providers/config.js";
+import {defaultValueProviders} from "./value-providers/default.js";
+import {DefinitionValueMode, definitionValues, TokenStructure} from "./value-providers/definition.js";
 
 export function getExpressionInput(input: string, pos: number): string {
   // Find start marker around the cursor position
@@ -100,8 +103,17 @@ export async function complete(
 
   const values = await getValues(token, keyToken, parent, config?.valueProviderConfig, workflowContext, indentString);
 
+  // Add escape hatch completions when completing an empty scalar value for a one-of field.
+  // These provide a way out of "dead end" situations where no scalar completions exist
+  // but alternative structural forms (list, mapping) are available.
+  const escapeHatches = getEscapeHatchCompletions(token, keyToken, indentString, newPos);
+  values.push(...escapeHatches);
+
+  // Figure out what text to replace when the user picks a completion.
+  // For example, if they typed `runs-|` and pick `runs-on`, we need to replace `runs-`.
   let replaceRange: Range | undefined;
   if (token?.range) {
+    // Prefer the token's range since it accounts for YAML syntax like quotes
     replaceRange = mapRange(token.range);
   } else if (!token) {
     // Not a valid token, create a range from the current position
@@ -127,20 +139,44 @@ export async function complete(
   return values.map(value => {
     const newText = value.insertText || value.label;
 
+    // Escape hatches provide their own textEdit to restructure the YAML
+    let textEdit: TextEdit;
+    if (value.textEdit) {
+      textEdit = TextEdit.replace(value.textEdit.range, value.textEdit.newText);
+    } else if (replaceRange) {
+      textEdit = TextEdit.replace(replaceRange, newText);
+    } else {
+      textEdit = TextEdit.insert(position, newText);
+    }
+
     const item: CompletionItem = {
       label: value.label,
+      detail: value.detail,
+      filterText: value.filterText,
+      sortText: value.sortText,
       documentation: value.description && {
         kind: "markdown",
         value: value.description
       },
       tags: value.deprecated ? [CompletionItemTag.Deprecated] : undefined,
-      textEdit: replaceRange ? TextEdit.replace(replaceRange, newText) : TextEdit.insert(position, newText)
+      textEdit
     };
 
     return item;
   });
 }
 
+/**
+ * Retrieves completion values for a token based on value providers and definitions.
+ *
+ * This function determines which values to suggest for auto-completion by:
+ * 1. First checking for custom value providers configured for the token's definition key
+ * 2. Then checking for default value providers for the token's definition key
+ * 3. Finally falling back to values derived from the token's schema definition
+ *
+ * The results are filtered to exclude duplicates (e.g., keys already defined in a mapping
+ * or values already present in a sequence) and sorted alphabetically.
+ */
 async function getValues(
   token: TemplateToken | null,
   keyToken: TemplateToken | null,
@@ -180,10 +216,181 @@ async function getValues(
     return [];
   }
 
-  const values = definitionValues(def, indentation, keyToken ? DefinitionValueMode.Key : DefinitionValueMode.Parent);
+  // When a schema allows multiple formats (e.g., `runs-on` can be a string OR a mapping),
+  // only suggest completions that match what the user has already started typing.
+  // For example, if they've started a mapping, don't suggest string values.
+  const tokenStructure = getTokenStructure(token);
+  const values = definitionValues(
+    def,
+    indentation,
+    keyToken ? DefinitionValueMode.Key : DefinitionValueMode.Parent,
+    tokenStructure
+  );
   return filterAndSortCompletionOptions(values, existingValues);
 }
 
+/**
+ * Determines what YAML structure the user has committed to, if any.
+ *
+ * Returns:
+ * - "mapping" if the user has started a key-value structure (e.g., `runs-on:\n  group: |`)
+ * - "sequence" if the user has started a list (e.g., `runs-on:\n  - |`)
+ * - "scalar" if the user has started typing a plain value (e.g., `runs-on: ubuntu-|`)
+ * - undefined if the user hasn't committed yet (e.g., `runs-on: |` with nothing typed)
+ */
+function getTokenStructure(token: TemplateToken | null): TokenStructure {
+  if (!token) {
+    return undefined;
+  }
+
+  switch (token.templateTokenType) {
+    case TokenType.Mapping:
+      return "mapping";
+    case TokenType.Sequence:
+      return "sequence";
+    case TokenType.Null:
+      // Null means `key: ` with nothing - user hasn't committed to a type yet
+      return undefined;
+    case TokenType.String: {
+      // Empty string means `key: |` - user hasn't committed yet
+      // Non-empty string means user has started typing a scalar value
+      const stringToken = token.assertString("getTokenStructure expected string token");
+      if (stringToken.value === "") {
+        return undefined;
+      }
+      return "scalar";
+    }
+    case TokenType.Boolean:
+    case TokenType.Number:
+      return "scalar";
+    default:
+      return undefined;
+  }
+}
+
+/**
+ * Generates escape hatch completions that allow switching from scalar form to
+ * alternative structural forms (sequence or mapping) when the value is empty.
+ *
+ * For example, at `runs-on: |`, this adds "(switch to list)" and "(switch to full syntax)"
+ * completions that restructure the YAML to `runs-on:\n  - |` or `runs-on:\n  |`.
+ *
+ * Only shown when:
+ * - Completing in value position (keyToken exists)
+ * - Value is empty (user hasn't committed to a structure yet)
+ * - Definition allows sequence or mapping structure
+ */
+function getEscapeHatchCompletions(
+  token: TemplateToken | null,
+  keyToken: TemplateToken | null,
+  indentation: string,
+  position: Position
+): Value[] {
+  // Only show escape hatches when value is empty
+  const tokenStructure = getTokenStructure(token);
+  if (tokenStructure !== undefined) {
+    return [];
+  }
+
+  // Need a key token with a definition
+  if (!keyToken?.definition) {
+    return [];
+  }
+
+  // Determine which structural types are available from the definition
+  const def = keyToken.definition;
+  const schema = getWorkflowSchema();
+  const buckets = {
+    sequence: false,
+    mapping: false
+  };
+
+  if (def instanceof OneOfDefinition) {
+    // OneOf: check each variant
+    for (const variantKey of def.oneOf) {
+      const variantDef = schema.definitions[variantKey];
+      if (variantDef) {
+        switch (variantDef.definitionType) {
+          case DefinitionType.Sequence:
+            buckets.sequence = true;
+            break;
+          case DefinitionType.Mapping:
+            buckets.mapping = true;
+            break;
+        }
+      }
+    }
+  } else {
+    // Single definition type
+    switch (def.definitionType) {
+      case DefinitionType.Sequence:
+        buckets.sequence = true;
+        break;
+      case DefinitionType.Mapping:
+        buckets.mapping = true;
+        break;
+    }
+  }
+
+  const results: Value[] = [];
+  const keyName = isString(keyToken) ? keyToken.value : "";
+  const keyRange = keyToken.range;
+
+  if (!keyRange || !keyName) {
+    return [];
+  }
+
+  // Calculate the range from key start to current position
+  // This covers "key: " so we can replace it with "key:\n  - " or "key:\n  "
+  const editRange = {
+    start: {line: keyRange.start.line - 1, character: keyRange.start.column - 1},
+    end: {line: position.line, character: position.character}
+  };
+
+  if (buckets.sequence) {
+    results.push({
+      label: "(switch to list)",
+      sortText: "zzz_switch_1",
+      filterText: keyName, // Allow filtering by key name
+      textEdit: {
+        range: editRange,
+        newText: `${keyName}:\n${indentation}- `
+      }
+    });
+  }
+
+  if (buckets.mapping) {
+    results.push({
+      label: "(switch to mapping)",
+      sortText: "zzz_switch_2",
+      filterText: keyName, // Allow filtering by key name
+      textEdit: {
+        range: editRange,
+        newText: `${keyName}:\n${indentation}`
+      }
+    });
+  }
+
+  return results;
+}
+
+/**
+ * Collects values that are already present in the current context, so they can be
+ * excluded from completion suggestions.
+ *
+ * For sequences (lists), returns all existing items. For example, if the user has:
+ *   labels:
+ *     - bug
+ *     - |
+ * This returns {"bug"} so we don't suggest "bug" again.
+ *
+ * For mappings, returns all existing keys. For example, if the user has:
+ *   jobs:
+ *     build:
+ *       runs-on: ubuntu-latest
+ *       |
+ * This returns {"runs-on"} so we don't suggest "runs-on" again.
+ */
 export function getExistingValues(token: TemplateToken | null, parent: TemplateToken) {
   // For incomplete YAML, we may only have a parent token
   if (token) {
@@ -253,7 +460,7 @@ function getExpressionCompletionItems(
 
 function filterAndSortCompletionOptions(options: Value[], existingValues?: Set<string>) {
   options = options.filter(x => !existingValues?.has(x.label));
-  options.sort((a, b) => a.label.localeCompare(b.label));
+  options.sort((a, b) => (a.sortText ?? a.label).localeCompare(b.sortText ?? b.label));
   return options;
 }
 

languageservice/src/context-providers/config.ts

@@ -1,6 +1,6 @@
 import {DescriptionDictionary} from "@actions/expressions";
-import {WorkflowContext} from "../context/workflow-context";
-import {Mode} from "./default";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {Mode} from "./default.js";
 
 export type ContextProviderConfig = {
   getContext: (

languageservice/src/context-providers/default.test.ts

@@ -1,6 +1,6 @@
 import {DescriptionDictionary} from "@actions/expressions";
-import {WorkflowContext} from "../context/workflow-context";
-import {getContext, Mode} from "./default";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {getContext, Mode} from "./default.js";
 
 describe("getContext", () => {
   const emptyWorkflowContext: WorkflowContext = {

languageservice/src/context-providers/default.ts

@@ -1,18 +1,18 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {Kind} from "@actions/expressions/data/expressiondata";
-import {WorkflowContext} from "../context/workflow-context";
-import {ContextProviderConfig} from "./config";
-import {getDescription, RootContext} from "./descriptions";
-import {getEnvContext} from "./env";
-import {getGithubContext} from "./github";
-import {getInputsContext} from "./inputs";
-import {getJobContext} from "./job";
-import {getJobsContext} from "./jobs";
-import {getMatrixContext} from "./matrix";
-import {getNeedsContext} from "./needs";
-import {getSecretsContext} from "./secrets";
-import {getStepsContext} from "./steps";
-import {getStrategyContext} from "./strategy";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {ContextProviderConfig} from "./config.js";
+import {getDescription, RootContext} from "./descriptions.js";
+import {getEnvContext} from "./env.js";
+import {getGithubContext} from "./github.js";
+import {getInputsContext} from "./inputs.js";
+import {getJobContext} from "./job.js";
+import {getJobsContext} from "./jobs.js";
+import {getMatrixContext} from "./matrix.js";
+import {getNeedsContext} from "./needs.js";
+import {getSecretsContext} from "./secrets.js";
+import {getStepsContext} from "./steps.js";
+import {getStrategyContext} from "./strategy.js";
 
 // ContextValue is the type of the value returned by a context provider
 // Null indicates that the context provider doesn't have any value to provide

languageservice/src/context-providers/env.ts

@@ -1,7 +1,7 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {isScalar, isString} from "@actions/workflow-parser";
 import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
-import {WorkflowContext} from "../context/workflow-context";
+import {WorkflowContext} from "../context/workflow-context.js";
 
 export function getEnvContext(workflowContext: WorkflowContext): DescriptionDictionary {
   const d = new DescriptionDictionary();

languageservice/src/context-providers/events/eventPayloads.test.ts

@@ -1,5 +1,5 @@
 import {DescriptionDictionary} from "@actions/expressions";
-import {getEventPayload, getSupportedEventTypes} from "./eventPayloads";
+import {getEventPayload, getSupportedEventTypes} from "./eventPayloads.js";
 
 describe("eventPayloads", () => {
   describe("getSupportedEventTypes", () => {

languageservice/src/context-providers/github.test.ts

@@ -1,7 +1,7 @@
-import {DescriptionDictionary, isDescriptionDictionary} from "@actions/expressions/.";
-import {testGetWorkflowContext} from "../test-utils/test-workflow-context";
-import {Mode} from "./default";
-import {getGithubContext} from "./github";
+import {DescriptionDictionary, isDescriptionDictionary} from "@actions/expressions";
+import {testGetWorkflowContext} from "../test-utils/test-workflow-context.js";
+import {Mode} from "./default.js";
+import {getGithubContext} from "./github.js";
 
 describe("github context", () => {
   it("single event", async () => {

languageservice/src/context-providers/github.ts

@@ -1,11 +1,11 @@
 import {data, DescriptionDictionary, isDescriptionDictionary} from "@actions/expressions";
 import {ExpressionData} from "@actions/expressions/data/expressiondata";
 import {TypesFilterConfig} from "@actions/workflow-parser/model/workflow-template";
-import {WorkflowContext} from "../context/workflow-context";
-import {Mode} from "./default";
-import {getDescription} from "./descriptions";
-import {getEventPayload, getSupportedEventTypes} from "./events/eventPayloads";
-import {getInputsContext} from "./inputs";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {Mode} from "./default.js";
+import {getDescription} from "./descriptions.js";
+import {getEventPayload, getSupportedEventTypes} from "./events/eventPayloads.js";
+import {getInputsContext} from "./inputs.js";
 
 export function getGithubContext(workflowContext: WorkflowContext, mode: Mode): DescriptionDictionary {
   // https://docs.github.com/en/actions/learn-github-actions/contexts#github-context

languageservice/src/context-providers/inputs.ts

@@ -1,6 +1,6 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {InputConfig} from "@actions/workflow-parser/model/workflow-template";
-import {WorkflowContext} from "../context/workflow-context";
+import {WorkflowContext} from "../context/workflow-context.js";
 
 export function getInputsContext(workflowContext: WorkflowContext): DescriptionDictionary {
   const d = new DescriptionDictionary();

languageservice/src/context-providers/job.ts

@@ -1,7 +1,7 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {isMapping, isSequence} from "@actions/workflow-parser";
 import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
-import {WorkflowContext} from "../context/workflow-context";
+import {WorkflowContext} from "../context/workflow-context.js";
 
 export function getJobContext(workflowContext: WorkflowContext): DescriptionDictionary {
   // https://docs.github.com/en/actions/learn-github-actions/contexts#job-context
@@ -35,6 +35,9 @@ export function getJobContext(workflowContext: WorkflowContext): DescriptionDict
   // Status
   jobContext.add("status", new data.Null());
 
+  // Check run ID
+  jobContext.add("check_run_id", new data.Null());
+
   return jobContext;
 }
 

languageservice/src/context-providers/jobs.ts

@@ -1,8 +1,8 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {StringData} from "@actions/expressions/data/string";
 import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
-import {WorkflowContext} from "../context/workflow-context";
-import {getDescription} from "./descriptions";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {getDescription} from "./descriptions.js";
 
 export function getJobsContext(workflowContext: WorkflowContext): DescriptionDictionary {
   // https://docs.github.com/en/actions/learn-github-actions/contexts#jobs-context

languageservice/src/context-providers/matrix.test.ts

@@ -6,9 +6,9 @@ import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-to
 import {SequenceToken} from "@actions/workflow-parser/templates/tokens/sequence-token";
 import {StringToken} from "@actions/workflow-parser/templates/tokens/string-token";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
-import {WorkflowContext} from "../context/workflow-context";
-import {Mode} from "./default";
-import {getMatrixContext} from "./matrix";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {Mode} from "./default.js";
+import {getMatrixContext} from "./matrix.js";
 
 type MatrixMap = {
   [key: string]: Array<string> | Array<{[key: string]: string}>;

languageservice/src/context-providers/matrix.ts

@@ -3,8 +3,8 @@ import {isBasicExpression, isMapping, isSequence, isString} from "@actions/workf
 import {KeyValuePair} from "@actions/workflow-parser/templates/tokens/key-value-pair";
 import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
 import {SequenceToken} from "@actions/workflow-parser/templates/tokens/sequence-token";
-import {WorkflowContext} from "../context/workflow-context";
-import {ContextValue, Mode} from "./default";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {ContextValue, Mode} from "./default.js";
 
 export function getMatrixContext(workflowContext: WorkflowContext, mode: Mode): ContextValue {
   // https://docs.github.com/en/actions/learn-github-actions/contexts#matrix-context

languageservice/src/context-providers/needs.test.ts

@@ -1,8 +1,8 @@
 import {DescriptionDictionary} from "@actions/expressions";
 import {StringData} from "@actions/expressions/data/string";
-import {WorkflowContext} from "../context/workflow-context";
-import {testGetWorkflowContext} from "../test-utils/test-workflow-context";
-import {getNeedsContext} from "./needs";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {testGetWorkflowContext} from "../test-utils/test-workflow-context.js";
+import {getNeedsContext} from "./needs.js";
 
 describe("needs context", () => {
   describe("invalid workflow context", () => {

languageservice/src/context-providers/needs.ts

@@ -3,7 +3,7 @@ import {isMapping, isScalar, isString} from "@actions/workflow-parser";
 import {isJob} from "@actions/workflow-parser/model/type-guards";
 import {WorkflowJob} from "@actions/workflow-parser/model/workflow-template";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
-import {WorkflowContext} from "../context/workflow-context";
+import {WorkflowContext} from "../context/workflow-context.js";
 
 export function getNeedsContext(workflowContext: WorkflowContext): DescriptionDictionary {
   const d = new DescriptionDictionary();

languageservice/src/context-providers/secrets.ts

@@ -1,8 +1,8 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {StringData} from "@actions/expressions/data/string";
-import {WorkflowContext} from "../context/workflow-context";
-import {Mode} from "./default";
-import {getDescription} from "./descriptions";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {Mode} from "./default.js";
+import {getDescription} from "./descriptions.js";
 
 export function getSecretsContext(workflowContext: WorkflowContext, mode: Mode): DescriptionDictionary {
   const d = new DescriptionDictionary({

languageservice/src/context-providers/steps.test.ts

@@ -1,7 +1,7 @@
 /* eslint-disable @typescript-eslint/no-non-null-assertion */
 import {DescriptionDictionary, isDescriptionDictionary} from "@actions/expressions";
-import {WorkflowContext} from "../context/workflow-context";
-import {getStepsContext} from "./steps";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {getStepsContext} from "./steps.js";
 
 function createWorkflowContext(stepIds: string[], currentStepId?: string): WorkflowContext {
   return {

languageservice/src/context-providers/steps.ts

@@ -1,7 +1,7 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {Step} from "@actions/workflow-parser/model/workflow-template";
-import {WorkflowContext} from "../context/workflow-context";
-import {getDescription} from "./descriptions";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {getDescription} from "./descriptions.js";
 
 export function getStepsContext(workflowContext: WorkflowContext): DescriptionDictionary {
   const d = new DescriptionDictionary();

languageservice/src/context-providers/strategy.test.ts

@@ -5,8 +5,8 @@ import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-to
 import {NumberToken} from "@actions/workflow-parser/templates/tokens/number-token";
 import {StringToken} from "@actions/workflow-parser/templates/tokens/string-token";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
-import {WorkflowContext} from "../context/workflow-context";
-import {getStrategyContext} from "./strategy";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {getStrategyContext} from "./strategy.js";
 
 function stringToToken(value: string) {
   return new StringToken(undefined, undefined, value, undefined);

languageservice/src/context-providers/strategy.ts

@@ -1,7 +1,7 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {isMapping, isScalar, isString} from "@actions/workflow-parser";
-import {WorkflowContext} from "../context/workflow-context";
-import {scalarToData} from "../utils/scalar-to-data";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {scalarToData} from "../utils/scalar-to-data.js";
 
 // Default strategy values when no strategy block is defined
 const DEFAULT_STRATEGY = {

languageservice/src/context/workflow-context.test.ts

@@ -1,5 +1,5 @@
 import {ActionStep, RunStep} from "@actions/workflow-parser/model/workflow-template";
-import {testGetWorkflowContext} from "../test-utils/test-workflow-context";
+import {testGetWorkflowContext} from "../test-utils/test-workflow-context.js";
 
 describe("getWorkflowContext", () => {
   it("context for workflow", async () => {

languageservice/src/description-providers/reusable-job-inputs.ts

@@ -1,7 +1,7 @@
 import {isMapping, isString} from "@actions/workflow-parser";
 import {DESCRIPTION} from "@actions/workflow-parser/templates/template-constants";
-import {WorkflowContext} from "../context/workflow-context";
-import {TokenResult} from "../utils/find-token";
+import {WorkflowContext} from "../context/workflow-context.js";
+import {TokenResult} from "../utils/find-token.js";
 
 export function isReusableWorkflowJobInput(tokenResult: TokenResult): boolean {
   return (

languageservice/src/document-links.test.ts

@@ -1,6 +1,6 @@
-import {documentLinks} from "./document-links";
-import {createDocument} from "./test-utils/document";
-import {clearCache} from "./utils/workflow-cache";
+import {documentLinks} from "./document-links.js";
+import {createDocument} from "./test-utils/document.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 beforeEach(() => {
   clearCache();

languageservice/src/document-links.ts

@@ -5,9 +5,9 @@ import {parseFileReference} from "@actions/workflow-parser/workflows/file-refere
 import {TextDocument} from "vscode-languageserver-textdocument";
 import {DocumentLink} from "vscode-languageserver-types";
 import * as vscodeURI from "vscode-uri";
-import {actionUrl, parseActionReference} from "./action";
-import {mapRange} from "./utils/range";
-import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache";
+import {actionUrl, parseActionReference} from "./action.js";
+import {mapRange} from "./utils/range.js";
+import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache.js";
 
 export async function documentLinks(document: TextDocument, workspace: string | undefined): Promise<DocumentLink[]> {
   const file: File = {

languageservice/src/e2e.test.ts

@@ -1,9 +1,9 @@
-import {complete} from "./complete";
-import {hover} from "./hover";
-import {registerLogger} from "./log";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {TestLogger} from "./test-utils/logger";
-import {clearCache} from "./utils/workflow-cache";
+import {complete} from "./complete.js";
+import {hover} from "./hover.js";
+import {registerLogger} from "./log.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 registerLogger(new TestLogger());
 
@@ -21,17 +21,21 @@ describe("end-to-end", () => {
     const result = await complete(...getPositionFromCursor(input));
 
     expect(result).not.toBeUndefined();
-    expect(result.length).toEqual(9);
-    const labels = result.map(x => x.label);
-    expect(labels).toEqual([
+    expect(result.length).toEqual(13);
+    const labelsWithDetails = result.map(x => (x.detail ? `${x.label} (${x.detail})` : x.label));
+    expect(labelsWithDetails).toEqual([
       "concurrency",
+      "concurrency (full syntax)",
       "defaults",
       "description",
       "env",
       "jobs",
       "name",
       "on",
+      "on (list)",
+      "on (full syntax)",
       "permissions",
+      "permissions (full syntax)",
       "run-name"
     ]);
   });

languageservice/src/expression-hover/expression-pos.test.ts

@@ -1,9 +1,9 @@
 import {parseWorkflow} from "@actions/workflow-parser";
 import {File} from "@actions/workflow-parser/workflows/file";
-import {nullTrace} from "../nulltrace";
-import {getPositionFromCursor} from "../test-utils/cursor-position";
-import {findToken} from "../utils/find-token";
-import {ExpressionPos, mapToExpressionPos} from "./expression-pos";
+import {nullTrace} from "../nulltrace.js";
+import {getPositionFromCursor} from "../test-utils/cursor-position.js";
+import {findToken} from "../utils/find-token.js";
+import {ExpressionPos, mapToExpressionPos} from "./expression-pos.js";
 
 describe("mapToExpressionPos", () => {
   it("simple expression", () => {

languageservice/src/expression-hover/expression-pos.ts

@@ -3,8 +3,8 @@ import {ensureStatusFunction} from "@actions/workflow-parser/model/converter/if-
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
 import {isBasicExpression, isString} from "@actions/workflow-parser/templates/tokens/type-guards";
 import {Position, Range as LSPRange} from "vscode-languageserver-textdocument";
-import {mapRange} from "../utils/range";
-import {posWithinRange} from "./pos-range";
+import {mapRange} from "../utils/range.js";
+import {posWithinRange} from "./pos-range.js";
 
 export type ExpressionPos = {
   /** The expression that includes the position */

languageservice/src/expression-hover/visitor.test.ts

@@ -2,13 +2,13 @@ import {data, DescriptionDictionary, Lexer, Parser} from "@actions/expressions";
 import {convertWorkflowTemplate, parseWorkflow} from "@actions/workflow-parser";
 import {ErrorPolicy} from "@actions/workflow-parser/model/convert";
 import {File} from "@actions/workflow-parser/workflows/file";
-import {ContextProviderConfig} from "../context-providers/config";
-import {getContext, Mode} from "../context-providers/default";
-import {getWorkflowContext} from "../context/workflow-context";
-import {validatorFunctions} from "../expression-validation/functions";
-import {nullTrace} from "../nulltrace";
-import {getPositionFromCursor} from "../test-utils/cursor-position";
-import {HoverVisitor} from "./visitor";
+import {ContextProviderConfig} from "../context-providers/config.js";
+import {getContext, Mode} from "../context-providers/default.js";
+import {getWorkflowContext} from "../context/workflow-context.js";
+import {validatorFunctions} from "../expression-validation/functions.js";
+import {nullTrace} from "../nulltrace.js";
+import {getPositionFromCursor} from "../test-utils/cursor-position.js";
+import {HoverVisitor} from "./visitor.js";
 
 const contextProviderConfig: ContextProviderConfig = {
   getContext: (context: string) => {

languageservice/src/expression-hover/visitor.ts

@@ -13,7 +13,7 @@ import {
 } from "@actions/expressions/ast";
 import {FunctionDefinition} from "@actions/expressions/funcs/info";
 import {Pos, Range} from "@actions/expressions/lexer";
-import {posWithinRange} from "./pos-range";
+import {posWithinRange} from "./pos-range.js";
 
 export type HoverResult =
   | undefined

languageservice/src/expression-validation/evaluator.ts

@@ -3,7 +3,7 @@ import {Expr, Logical} from "@actions/expressions/ast";
 import {ExpressionData} from "@actions/expressions/data/expressiondata";
 import {TokenType} from "@actions/expressions/lexer";
 import {falsy, truthy} from "@actions/expressions/result";
-import {AccessError} from "./error-dictionary";
+import {AccessError} from "./error-dictionary.js";
 
 export type ValidationError = {
   message: string;

languageservice/src/hover.expressions.test.ts

@@ -1,12 +1,12 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {format} from "@actions/expressions/funcs/format";
 import {Hover} from "vscode-languageserver-types";
-import {ContextProviderConfig} from "./context-providers/config";
-import {hover} from "./hover";
-import {registerLogger} from "./log";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {TestLogger} from "./test-utils/logger";
-import {clearCache} from "./utils/workflow-cache";
+import {ContextProviderConfig} from "./context-providers/config.js";
+import {hover} from "./hover.js";
+import {registerLogger} from "./log.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 const contextProviderConfig: ContextProviderConfig = {
   getContext: (context: string) => {

languageservice/src/hover.reusable-workflow.test.ts

@@ -1,7 +1,7 @@
-import {hover} from "./hover";
-import {testHoverConfig} from "./hover.test";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {clearCache} from "./utils/workflow-cache";
+import {hover} from "./hover.js";
+import {testHoverConfig} from "./hover.test.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 beforeEach(() => {
   clearCache();

languageservice/src/hover.test.ts

@@ -1,8 +1,8 @@
 import {isString} from "@actions/workflow-parser";
-import {DescriptionProvider, hover, HoverConfig} from "./hover";
-import {getPositionFromCursor} from "./test-utils/cursor-position";
-import {testFileProvider} from "./test-utils/test-file-provider";
-import {clearCache} from "./utils/workflow-cache";
+import {DescriptionProvider, hover, HoverConfig} from "./hover.js";
+import {getPositionFromCursor} from "./test-utils/cursor-position.js";
+import {testFileProvider} from "./test-utils/test-file-provider.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 export function testHoverConfig(tokenValue: string, tokenKey: string, description?: string) {
   return {

languageservice/src/hover.ts

@@ -9,21 +9,21 @@ import {File} from "@actions/workflow-parser/workflows/file";
 import {FileProvider} from "@actions/workflow-parser/workflows/file-provider";
 import {Position, TextDocument} from "vscode-languageserver-textdocument";
 import {Hover} from "vscode-languageserver-types";
-import {ContextProviderConfig} from "./context-providers/config";
-import {getContext, Mode} from "./context-providers/default";
-import {getFunctionDescription} from "./context-providers/descriptions";
-import {getWorkflowContext, WorkflowContext} from "./context/workflow-context";
+import {ContextProviderConfig} from "./context-providers/config.js";
+import {getContext, Mode} from "./context-providers/default.js";
+import {getFunctionDescription} from "./context-providers/descriptions.js";
+import {getWorkflowContext, WorkflowContext} from "./context/workflow-context.js";
 import {
   getReusableWorkflowInputDescription,
   isReusableWorkflowJobInput
-} from "./description-providers/reusable-job-inputs";
-import {ExpressionPos, mapToExpressionPos} from "./expression-hover/expression-pos";
-import {HoverVisitor} from "./expression-hover/visitor";
-import {info} from "./log";
-import {isPotentiallyExpression} from "./utils/expression-detection";
-import {findToken} from "./utils/find-token";
-import {mapRange} from "./utils/range";
-import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache";
+} from "./description-providers/reusable-job-inputs.js";
+import {ExpressionPos, mapToExpressionPos} from "./expression-hover/expression-pos.js";
+import {HoverVisitor} from "./expression-hover/visitor.js";
+import {info} from "./log.js";
+import {isPotentiallyExpression} from "./utils/expression-detection.js";
+import {findToken} from "./utils/find-token.js";
+import {mapRange} from "./utils/range.js";
+import {fetchOrConvertWorkflowTemplate, fetchOrParseWorkflow} from "./utils/workflow-cache.js";
 
 export type HoverConfig = {
   descriptionProvider?: DescriptionProvider;

languageservice/src/index.ts

@@ -1,7 +1,8 @@
-export {complete} from "./complete";
-export {ContextProviderConfig} from "./context-providers/config";
-export {documentLinks} from "./document-links";
-export {hover} from "./hover";
-export {Logger, LogLevel, registerLogger, setLogLevel} from "./log";
-export {validate, ValidationConfig, ActionsMetadataProvider} from "./validate";
-export {ValueProviderConfig, ValueProviderKind} from "./value-providers/config";
+export {complete} from "./complete.js";
+export {ContextProviderConfig} from "./context-providers/config.js";
+export {documentLinks} from "./document-links.js";
+export {hover} from "./hover.js";
+export {getInlayHints} from "./inlay-hints.js";
+export {Logger, LogLevel, registerLogger, setLogLevel} from "./log.js";
+export {validate, ValidationConfig, ActionsMetadataProvider} from "./validate.js";
+export {ValueProviderConfig, ValueProviderKind} from "./value-providers/config.js";

languageservice/src/inlay-hints.test.ts

@@ -0,0 +1,116 @@
+import {InlayHintKind} from "vscode-languageserver-types";
+import {getInlayHints} from "./inlay-hints.js";
+import {registerLogger} from "./log.js";
+import {createDocument} from "./test-utils/document.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {clearCache} from "./utils/workflow-cache.js";
+
+registerLogger(new TestLogger());
+
+beforeEach(() => {
+  clearCache();
+});
+
+describe("inlay-hints", () => {
+  describe("cron expressions", () => {
+    it("returns inlay hint for valid cron expression", () => {
+      const input = `on:
+  schedule:
+    - cron: '0 * * * *'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(1);
+      expect(hints[0].label).toBe("→ Runs every hour");
+      expect(hints[0].kind).toBe(InlayHintKind.Parameter);
+      expect(hints[0].paddingLeft).toBe(true);
+    });
+
+    it("returns correct position at end of cron value", () => {
+      const input = `on:
+  schedule:
+    - cron: '0 3 * * 1'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(1);
+      // Position should be at the end of the cron string value (after the closing quote)
+      // Line 3 (0-indexed: 2), end of '0 3 * * 1'
+      expect(hints[0].position.line).toBe(2);
+    });
+
+    it("returns no hint for invalid cron expression", () => {
+      const input = `on:
+  schedule:
+    - cron: 'invalid cron'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(0);
+    });
+
+    it("returns multiple hints for multiple cron expressions", () => {
+      const input = `on:
+  schedule:
+    - cron: '0 * * * *'
+    - cron: '0 0 * * *'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(2);
+      expect(hints[0].label).toBe("→ Runs every hour");
+      expect(hints[1].label).toBe("→ Runs at 00:00");
+    });
+
+    it("returns hint with descriptive label for weekly cron", () => {
+      const input = `on:
+  schedule:
+    - cron: '0 3 * * 1'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(1);
+      expect(hints[0].label).toContain("Monday");
+    });
+
+    it("returns no hints for empty workflow", () => {
+      const input = ``;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(0);
+    });
+
+    it("returns no hints for workflow without schedule", () => {
+      const input = `on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo hello
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(0);
+    });
+
+    it("returns hint for frequent cron that triggers warning", () => {
+      // Even crons that trigger the <5min warning should still get inlay hints
+      const input = `on:
+  schedule:
+    - cron: '* * * * *'
+`;
+      const document = createDocument("test.yaml", input);
+      const hints = getInlayHints(document);
+
+      expect(hints).toHaveLength(1);
+      expect(hints[0].label).toBe("→ Runs every minute");
+    });
+  });
+});

languageservice/src/inlay-hints.ts

@@ -0,0 +1,56 @@
+import {isString} from "@actions/workflow-parser";
+import {getCronDescription} from "@actions/workflow-parser/model/converter/cron";
+import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
+import {File} from "@actions/workflow-parser/workflows/file";
+import {TextDocument} from "vscode-languageserver-textdocument";
+import {InlayHint, InlayHintKind} from "vscode-languageserver-types";
+import {fetchOrParseWorkflow} from "./utils/workflow-cache.js";
+
+/**
+ * Returns inlay hints for a workflow document.
+ * Currently supports cron expressions, showing a human-readable description
+ * of the schedule inline after the cron value.
+ *
+ * @param document Text document to get inlay hints for
+ * @returns Array of inlay hints
+ */
+export function getInlayHints(document: TextDocument): InlayHint[] {
+  const file: File = {
+    name: document.uri,
+    content: document.getText()
+  };
+
+  const result = fetchOrParseWorkflow(file, document.uri);
+  if (!result?.value) {
+    return [];
+  }
+
+  const hints: InlayHint[] = [];
+
+  // Traverse the workflow AST to find cron expressions
+  for (const [parent, token, key] of TemplateToken.traverse(result.value)) {
+    const validationToken = key || parent || token;
+    const validationDefinition = validationToken.definition;
+
+    // Check for cron-pattern tokens
+    if (isString(token) && token.range && validationDefinition?.key === "cron-pattern") {
+      const cronValue = token.value;
+      const description = getCronDescription(cronValue);
+
+      if (description) {
+        // Position the hint at the end of the cron value
+        hints.push({
+          position: {
+            line: token.range.end.line - 1, // Convert from 1-based to 0-based
+            character: token.range.end.column - 1 // Convert from 1-based to 0-based
+          },
+          label: `→ ${description}`,
+          kind: InlayHintKind.Parameter,
+          paddingLeft: true
+        });
+      }
+    }
+  }
+
+  return hints;
+}

languageservice/src/test-utils/cursor-position.test.ts

@@ -1,5 +1,5 @@
-import {clearCache} from "../utils/workflow-cache";
-import {getPositionFromCursor} from "./cursor-position";
+import {clearCache} from "../utils/workflow-cache.js";
+import {getPositionFromCursor} from "./cursor-position.js";
 
 beforeEach(() => {
   clearCache();

languageservice/src/test-utils/cursor-position.ts

@@ -1,5 +1,5 @@
 import {Position, TextDocument} from "vscode-languageserver-textdocument";
-import {createDocument} from "./document";
+import {createDocument} from "./document.js";
 
 /**
  * Calculates the position of the cursor and the document without that cursor

languageservice/src/test-utils/logger.ts

@@ -1,4 +1,4 @@
-import {Logger} from "../log";
+import {Logger} from "../log.js";
 
 export class TestLogger implements Logger {
   error(message: string): void {

languageservice/src/test-utils/test-workflow-context.ts

@@ -1,9 +1,9 @@
 import {convertWorkflowTemplate, parseWorkflow, WorkflowTemplate} from "@actions/workflow-parser";
-import {getWorkflowContext, WorkflowContext} from "../context/workflow-context";
-import {nullTrace} from "../nulltrace";
-import {findToken} from "../utils/find-token";
-import {getPositionFromCursor} from "./cursor-position";
-import {testFileProvider} from "./test-file-provider";
+import {getWorkflowContext, WorkflowContext} from "../context/workflow-context.js";
+import {nullTrace} from "../nulltrace.js";
+import {findToken} from "../utils/find-token.js";
+import {getPositionFromCursor} from "./cursor-position.js";
+import {testFileProvider} from "./test-file-provider.js";
 
 export async function testGetWorkflowContext(input: string): Promise<WorkflowContext> {
   const [textDocument, pos] = getPositionFromCursor(input);

languageservice/src/utils/find-token.test.ts

@@ -1,9 +1,9 @@
 import {isScalar, parseWorkflow} from "@actions/workflow-parser";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
 import {TokenType} from "@actions/workflow-parser/templates/tokens/types";
-import {nullTrace} from "../nulltrace";
-import {getPositionFromCursor} from "../test-utils/cursor-position";
-import {findToken} from "./find-token";
+import {nullTrace} from "../nulltrace.js";
+import {getPositionFromCursor} from "../test-utils/cursor-position.js";
+import {findToken} from "./find-token.js";
 
 type testTokenInfo = [definitionKey: string | null, tokenType: TokenType, literalValue?: string];
 

languageservice/src/utils/transform.test.ts

@@ -1,5 +1,5 @@
-import {getPositionFromCursor} from "../test-utils/cursor-position";
-import {transform} from "./transform";
+import {getPositionFromCursor} from "../test-utils/cursor-position.js";
+import {transform} from "./transform.js";
 
 describe("transform", () => {
   it("adds : at end of line", () => {

languageservice/src/utils/workflow-cache.ts

@@ -4,8 +4,8 @@ import {TemplateContext} from "@actions/workflow-parser/templates/template-conte
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
 import {File} from "@actions/workflow-parser/workflows/file";
 
-import {CompletionConfig} from "../complete";
-import {nullTrace} from "../nulltrace";
+import {CompletionConfig} from "../complete.js";
+import {nullTrace} from "../nulltrace.js";
 
 const parsedWorkflowCache = new Map<string, ParseWorkflowResult>();
 const workflowTemplateCache = new Map<string, WorkflowTemplate>();

languageservice/src/validate-action.ts

@@ -4,9 +4,9 @@ import {Step} from "@actions/workflow-parser/model/workflow-template";
 import {ScalarToken} from "@actions/workflow-parser/templates/tokens/scalar-token";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
 import {Diagnostic, DiagnosticSeverity} from "vscode-languageserver-types";
-import {parseActionReference} from "./action";
-import {mapRange} from "./utils/range";
-import {ValidationConfig} from "./validate";
+import {parseActionReference} from "./action.js";
+import {mapRange} from "./utils/range.js";
+import {ValidationConfig} from "./validate.js";
 
 export async function validateAction(
   diagnostics: Diagnostic[],

languageservice/src/validate.actions.test.ts

@@ -1,11 +1,11 @@
 import {DiagnosticSeverity} from "vscode-languageserver-types";
-import {ActionMetadata, ActionReference} from "./action";
-import {registerLogger} from "./log";
-import {createDocument} from "./test-utils/document";
-import {TestLogger} from "./test-utils/logger";
-import {validate, ValidationConfig} from "./validate";
-import {ValueProviderKind} from "./value-providers/config";
-import {clearCache} from "./utils/workflow-cache";
+import {ActionMetadata, ActionReference} from "./action.js";
+import {registerLogger} from "./log.js";
+import {createDocument} from "./test-utils/document.js";
+import {TestLogger} from "./test-utils/logger.js";
+import {validate, ValidationConfig} from "./validate.js";
+import {ValueProviderKind} from "./value-providers/config.js";
+import {clearCache} from "./utils/workflow-cache.js";
 
 registerLogger(new TestLogger());