diff --git a/languageserver/src/connection.ts b/languageserver/src/connection.ts
index d0a7ede3..8d19019e 100644
--- a/languageserver/src/connection.ts
+++ b/languageserver/src/connection.ts
@@ -1,8 +1,18 @@
-import {documentLinks, getInlayHints, hover, validate, ValidationConfig} from "@actions/languageservice";
+import {
+  documentLinks,
+  getCodeActions,
+  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";
 import {
+  CodeAction,
+  CodeActionKind,
+  CodeActionParams,
   CompletionItem,
   Connection,
   DocumentLink,
@@ -79,7 +89,10 @@ export function initConnection(connection: Connection) {
         documentLinkProvider: {
           resolveProvider: false
         },
-        inlayHintProvider: true
+        inlayHintProvider: true,
+        codeActionProvider: {
+          codeActionKinds: [CodeActionKind.QuickFix]
+        }
       }
     };
 
@@ -176,6 +189,17 @@ export function initConnection(connection: Connection) {
     });
   });
 
+  connection.onCodeAction((params: CodeActionParams): CodeAction[] => {
+    const document = getDocument(documents, params.textDocument);
+    return getCodeActions({
+      uri: params.textDocument.uri,
+      documentContent: document.getText(),
+      diagnostics: params.context.diagnostics,
+      only: params.context.only,
+      featureFlags
+    });
+  });
+
   // Make the text document manager listen on the connection
   // for open, change and close text document events
   documents.listen(connection);
diff --git a/languageservice/src/code-actions/code-actions.ts b/languageservice/src/code-actions/code-actions.ts
new file mode 100644
index 00000000..6e9f4330
--- /dev/null
+++ b/languageservice/src/code-actions/code-actions.ts
@@ -0,0 +1,55 @@
+import {FeatureFlags} from "@actions/expressions";
+import {CodeAction, CodeActionKind, Diagnostic} from "vscode-languageserver-types";
+import {CodeActionContext, CodeActionProvider} from "./types.js";
+import {getQuickfixProviders} from "./quickfix/quickfix-providers.js";
+
+export interface CodeActionParams {
+  uri: string;
+  documentContent: string;
+  diagnostics: Diagnostic[];
+  only?: string[];
+  featureFlags?: FeatureFlags;
+}
+
+export function getCodeActions(params: CodeActionParams): CodeAction[] {
+  const actions: CodeAction[] = [];
+  const context: CodeActionContext = {
+    uri: params.uri,
+    documentContent: params.documentContent,
+    featureFlags: params.featureFlags
+  };
+
+  // Build providers map based on feature flags
+  const providersByKind: Map<string, CodeActionProvider[]> = new Map([
+    [CodeActionKind.QuickFix, getQuickfixProviders(params.featureFlags)]
+    // [CodeActionKind.Refactor, getRefactorProviders(params.featureFlags)],
+    // [CodeActionKind.Source, getSourceProviders(params.featureFlags)],
+    // etc
+  ]);
+
+  // Filter to requested kinds, or use all if none specified
+  const requestedKinds = params.only;
+  const kindsToCheck = requestedKinds
+    ? [...providersByKind.keys()].filter(kind => requestedKinds.some(requested => kind.startsWith(requested)))
+    : [...providersByKind.keys()];
+
+  for (const diagnostic of params.diagnostics) {
+    for (const kind of kindsToCheck) {
+      const providers = providersByKind.get(kind) ?? [];
+      for (const provider of providers) {
+        if (provider.diagnosticCodes.includes(diagnostic.code)) {
+          const action = provider.createCodeAction(context, diagnostic);
+          if (action) {
+            action.kind = kind;
+            action.diagnostics = [diagnostic];
+            actions.push(action);
+          }
+        }
+      }
+    }
+  }
+
+  return actions;
+}
+
+export type {CodeActionContext, CodeActionProvider} from "./types.js";
diff --git a/languageservice/src/code-actions/quickfix/add-missing-inputs.ts b/languageservice/src/code-actions/quickfix/add-missing-inputs.ts
new file mode 100644
index 00000000..c416cccd
--- /dev/null
+++ b/languageservice/src/code-actions/quickfix/add-missing-inputs.ts
@@ -0,0 +1,245 @@
+import {isMapping} from "@actions/workflow-parser";
+import {MappingToken} from "@actions/workflow-parser/templates/tokens/mapping-token";
+import {ScalarToken} from "@actions/workflow-parser/templates/tokens/scalar-token";
+import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
+import {CodeAction, Position, TextEdit} from "vscode-languageserver-types";
+import {error} from "../../log.js";
+import {findToken} from "../../utils/find-token.js";
+import {getOrParseWorkflow} from "../../utils/workflow-cache.js";
+import {DiagnosticCode, MissingInputsDiagnosticData} from "../../validate-action-reference.js";
+import {CodeActionContext, CodeActionProvider} from "../types.js";
+
+/**
+ * Information extracted from a step token needed to generate edits
+ */
+interface StepInfo {
+  /** Column where step keys start (1-indexed), e.g., the column of "uses:" */
+  stepKeyColumn: number;
+  /** End line of the step (1-indexed) */
+  stepEndLine: number;
+  /** Detected indent size (spaces per level) */
+  indentSize: number;
+  /** Information about existing with: block, if present */
+  withInfo?: {
+    keyColumn: number;
+    keyEndLine: number;
+    valueEndLine: number;
+    hasChildren: boolean;
+    /** Column of first child input (1-indexed), for indentation detection */
+    firstChildColumn?: number;
+  };
+}
+
+export const addMissingInputsProvider: CodeActionProvider = {
+  diagnosticCodes: [DiagnosticCode.MissingRequiredInputs],
+
+  createCodeAction(context: CodeActionContext, diagnostic): CodeAction | undefined {
+    const data = diagnostic.data as MissingInputsDiagnosticData | undefined;
+    if (!data) {
+      return undefined;
+    }
+
+    // Parse the document to get the step token
+    const stepInfo = getStepInfo(context, diagnostic.range.start);
+    if (!stepInfo) {
+      return undefined;
+    }
+
+    const edits = createInputEdits(data.missingInputs, stepInfo);
+    if (!edits || edits.length === 0) {
+      return undefined;
+    }
+
+    const inputNames = data.missingInputs.map(i => i.name).join(", ");
+
+    return {
+      title: `Add missing input${data.missingInputs.length > 1 ? "s" : ""}: ${inputNames}`,
+      edit: {
+        changes: {
+          [context.uri]: edits
+        }
+      }
+    };
+  }
+};
+
+/**
+ * Parse the document and extract step information needed for generating edits.
+ * Returns undefined if parsing fails or the step token cannot be found.
+ */
+function getStepInfo(context: CodeActionContext, diagnosticPosition: Position): StepInfo | undefined {
+  // Parse the document (uses cache if available from validation)
+  const file = {name: context.uri, content: context.documentContent};
+  const parseResult = getOrParseWorkflow(file, context.uri);
+
+  if (!parseResult.value) {
+    error("Failed to parse workflow for missing inputs quickfix");
+    return undefined;
+  }
+
+  // Find the token at the diagnostic position
+  const {path} = findToken(diagnosticPosition, parseResult.value);
+
+  // Walk up the path to find the step token (regular-step)
+  const stepToken = findStepInPath(path);
+  if (!stepToken) {
+    error("Could not find step token for missing inputs quickfix");
+    return undefined;
+  }
+
+  return extractStepInfo(stepToken);
+}
+
+/**
+ * Find the step token (regular-step) in the token path
+ */
+function findStepInPath(path: TemplateToken[]): MappingToken | undefined {
+  // Walk backwards through path to find the step
+  for (let i = path.length - 1; i >= 0; i--) {
+    if (path[i].definition?.key === "regular-step" && isMapping(path[i])) {
+      return path[i] as MappingToken;
+    }
+  }
+  return undefined;
+}
+
+/**
+ * Extract position and indentation info from a step token
+ */
+function extractStepInfo(stepToken: MappingToken): StepInfo | undefined {
+  if (!stepToken.range) {
+    return undefined;
+  }
+
+  // Get the column of the first key in the step
+  let stepKeyColumn = stepToken.range.start.column;
+  if (stepToken.count > 0) {
+    const firstEntry = stepToken.get(0);
+    if (firstEntry?.key.range) {
+      stepKeyColumn = firstEntry.key.range.start.column;
+    }
+  }
+
+  // Find the with: block if present
+  let withKey: ScalarToken | undefined;
+  let withToken: TemplateToken | undefined;
+  for (const {key, value} of stepToken) {
+    if (key.toString() === "with") {
+      withKey = key;
+      withToken = value;
+      break;
+    }
+  }
+
+  // Calculate indent size
+  let indentSize = 2; // Default
+  let withInfo: StepInfo["withInfo"];
+
+  if (withKey?.range && withToken?.range) {
+    // Has with: block - extract its info
+    const hasChildren = isMapping(withToken) && withToken.count > 0;
+    let firstChildColumn: number | undefined;
+
+    if (hasChildren) {
+      const firstChild = (withToken as MappingToken).get(0);
+      if (firstChild?.key.range) {
+        firstChildColumn = firstChild.key.range.start.column;
+        // Detect indent size from with: children
+        indentSize = firstChildColumn - withKey.range.start.column;
+      }
+    }
+
+    withInfo = {
+      keyColumn: withKey.range.start.column,
+      keyEndLine: withKey.range.end.line,
+      valueEndLine: withToken.range.end.line,
+      hasChildren,
+      firstChildColumn
+    };
+  } else {
+    // No with: block - detect indent size using heuristics
+    // Based on the step key column position, estimate indent size
+    // 2-space indent files typically have step keys at column 7
+    // 4-space indent files typically have step keys at column 15
+    const zeroIndexedCol = stepKeyColumn - 1;
+    if (zeroIndexedCol >= 10) {
+      indentSize = 4;
+    }
+  }
+
+  return {
+    stepKeyColumn,
+    stepEndLine: stepToken.range.end.line,
+    indentSize,
+    withInfo
+  };
+}
+
+/**
+ * Generate text edits to add missing inputs
+ */
+function createInputEdits(missingInputs: MissingInputsDiagnosticData["missingInputs"], stepInfo: StepInfo): TextEdit[] {
+  const formatInputLines = (indent: string) =>
+    missingInputs.map(input => {
+      const value = input.default ?? '""';
+      return `${indent}${input.name}: ${value}`;
+    });
+
+  if (stepInfo.withInfo) {
+    // `with:` exists - add inputs to existing block
+    const withIndent = stepInfo.withInfo.keyColumn - 1; // 0-indexed
+    const inputIndentSize = stepInfo.withInfo.firstChildColumn
+      ? stepInfo.withInfo.firstChildColumn - stepInfo.withInfo.keyColumn
+      : stepInfo.indentSize;
+
+    const inputIndent = " ".repeat(withIndent + inputIndentSize);
+    const inputLines = formatInputLines(inputIndent);
+
+    // Calculate insert position
+    let insertLine: number;
+    if (stepInfo.withInfo.hasChildren) {
+      // Insert after the last child (at end of with: block)
+      // valueEndLine is 1-indexed, we want 0-indexed for Position
+      insertLine = stepInfo.withInfo.valueEndLine - 1;
+    } else {
+      // Empty with: block - insert on the next line after with:
+      // keyEndLine is 1-indexed, convert to 0-indexed and go to next line
+      insertLine = stepInfo.withInfo.keyEndLine;
+    }
+
+    const insertPosition: Position = {
+      line: insertLine,
+      character: 0
+    };
+
+    return [
+      {
+        range: {start: insertPosition, end: insertPosition},
+        newText: inputLines.map(line => line + "\n").join("")
+      }
+    ];
+  } else {
+    // No `with:` key - add `with:` at the same level as other step keys
+    const withKeyIndent = stepInfo.stepKeyColumn - 1; // 0-indexed (columns are 1-based)
+
+    const withIndent = " ".repeat(withKeyIndent);
+    const inputIndent = " ".repeat(withKeyIndent + stepInfo.indentSize);
+    const inputLines = formatInputLines(inputIndent);
+
+    const newText = `${withIndent}with:\n` + inputLines.map(line => `${line}\n`).join("");
+
+    // Insert at end of step
+    // stepEndLine is 1-indexed, we want 0-indexed and insert before the line after
+    const insertPosition: Position = {
+      line: stepInfo.stepEndLine - 1,
+      character: 0
+    };
+
+    return [
+      {
+        range: {start: insertPosition, end: insertPosition},
+        newText
+      }
+    ];
+  }
+}
diff --git a/languageservice/src/code-actions/quickfix/quickfix-providers.ts b/languageservice/src/code-actions/quickfix/quickfix-providers.ts
new file mode 100644
index 00000000..726cbac8
--- /dev/null
+++ b/languageservice/src/code-actions/quickfix/quickfix-providers.ts
@@ -0,0 +1,13 @@
+import {FeatureFlags} from "@actions/expressions";
+import {CodeActionProvider} from "../types.js";
+import {addMissingInputsProvider} from "./add-missing-inputs.js";
+
+export function getQuickfixProviders(featureFlags?: FeatureFlags): CodeActionProvider[] {
+  const providers: CodeActionProvider[] = [];
+
+  if (featureFlags?.isEnabled("missingInputsQuickfix")) {
+    providers.push(addMissingInputsProvider);
+  }
+
+  return providers;
+}
diff --git a/languageservice/src/code-actions/tests/runner.test.ts b/languageservice/src/code-actions/tests/runner.test.ts
new file mode 100644
index 00000000..595515e3
--- /dev/null
+++ b/languageservice/src/code-actions/tests/runner.test.ts
@@ -0,0 +1,90 @@
+import * as path from "path";
+import {fileURLToPath} from "url";
+import {loadTestCases, runTestCase} from "./runner.js";
+import {ValidationConfig} from "../../validate.js";
+import {ActionMetadata, ActionReference} from "../../action.js";
+import {clearCache} from "../../utils/workflow-cache.js";
+
+// ESM-compatible __dirname
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+// Mock action metadata provider for tests
+const validationConfig: ValidationConfig = {
+  actionsMetadataProvider: {
+    fetchActionMetadata: (ref: ActionReference): Promise<ActionMetadata | undefined> => {
+      const key = `${ref.owner}/${ref.name}@${ref.ref}`;
+
+      const metadata: Record<string, ActionMetadata> = {
+        "actions/cache@v1": {
+          name: "Cache",
+          description: "Cache dependencies",
+          inputs: {
+            path: {
+              description: "A list of files to cache",
+              required: true
+            },
+            key: {
+              description: "Cache key",
+              required: true
+            },
+            "restore-keys": {
+              description: "Restore keys",
+              required: false
+            }
+          }
+        },
+        "actions/setup-node@v3": {
+          name: "Setup Node",
+          description: "Setup Node.js",
+          inputs: {
+            "node-version": {
+              description: "Node version",
+              required: true,
+              default: "16"
+            }
+          }
+        }
+      };
+
+      return Promise.resolve(metadata[key]);
+    }
+  }
+};
+
+// Point to the source testdata directory
+const testdataDir = path.join(__dirname, "testdata");
+
+beforeEach(() => {
+  clearCache();
+});
+
+describe("code action golden tests", () => {
+  const testCases = loadTestCases(testdataDir);
+
+  if (testCases.length === 0) {
+    it.todo("no test cases found - add .yml files to testdata/");
+    return;
+  }
+
+  for (const testCase of testCases) {
+    it(testCase.name, async () => {
+      const result = await runTestCase(testCase, validationConfig);
+
+      if (!result.passed) {
+        let errorMessage = result.error || "Test failed";
+
+        if (result.expected !== undefined && result.actual !== undefined) {
+          errorMessage += "\n\n";
+          errorMessage += "=== EXPECTED (golden file) ===\n";
+          errorMessage += result.expected;
+          errorMessage += "\n\n";
+          errorMessage += "=== ACTUAL ===\n";
+          errorMessage += result.actual;
+        }
+
+        throw new Error(errorMessage);
+      }
+    });
+  }
+});
diff --git a/languageservice/src/code-actions/tests/runner.ts b/languageservice/src/code-actions/tests/runner.ts
new file mode 100644
index 00000000..06a1598d
--- /dev/null
+++ b/languageservice/src/code-actions/tests/runner.ts
@@ -0,0 +1,231 @@
+import * as fs from "fs";
+import * as path from "path";
+import {TextEdit} from "vscode-languageserver-types";
+import {TextDocument} from "vscode-languageserver-textdocument";
+import {FeatureFlags} from "@actions/expressions";
+import {validate, ValidationConfig} from "../../validate.js";
+import {getCodeActions, CodeActionParams} from "../code-actions.js";
+
+// Marker pattern: # want "diagnostic message" fix="code-action-name"
+const MARKER_PATTERN = /#\s*want\s+"([^"]+)"(?:\s+fix="([^"]+)")?/;
+
+export interface TestCase {
+  name: string;
+  inputPath: string;
+  goldenPath: string;
+  input: string;
+  golden: string;
+  markers: Marker[];
+}
+
+export interface Marker {
+  line: number;
+  message: string;
+  fix?: string;
+}
+
+export interface TestResult {
+  name: string;
+  passed: boolean;
+  error?: string;
+  expected?: string;
+  actual?: string;
+}
+
+/**
+ * Parse markers from input file content
+ */
+export function parseMarkers(content: string): Marker[] {
+  const lines = content.split("\n");
+  const markers: Marker[] = [];
+
+  for (let i = 0; i < lines.length; i++) {
+    const match = lines[i].match(MARKER_PATTERN);
+    if (match) {
+      markers.push({
+        line: i,
+        message: match[1],
+        fix: match[2]
+      });
+    }
+  }
+
+  return markers;
+}
+
+/**
+ * Strip markers from content (for processing)
+ */
+export function stripMarkers(content: string): string {
+  return content
+    .split("\n")
+    .map(line => line.replace(MARKER_PATTERN, "").trimEnd())
+    .join("\n");
+}
+
+/**
+ * Load all test cases from a testdata directory
+ */
+export function loadTestCases(testdataDir: string): TestCase[] {
+  const testCases: TestCase[] = [];
+
+  function walkDir(dir: string) {
+    const entries = fs.readdirSync(dir, {withFileTypes: true});
+
+    for (const entry of entries) {
+      const fullPath = path.join(dir, entry.name);
+
+      if (entry.isDirectory()) {
+        walkDir(fullPath);
+      } else if (entry.isFile() && entry.name.endsWith(".yml") && !entry.name.endsWith(".golden.yml")) {
+        const goldenPath = fullPath.replace(".yml", ".golden.yml");
+
+        if (fs.existsSync(goldenPath)) {
+          const input = fs.readFileSync(fullPath, "utf-8");
+          const golden = fs.readFileSync(goldenPath, "utf-8");
+
+          testCases.push({
+            name: path.relative(testdataDir, fullPath),
+            inputPath: fullPath,
+            goldenPath,
+            input,
+            golden,
+            markers: parseMarkers(input)
+          });
+        }
+      }
+    }
+  }
+
+  walkDir(testdataDir);
+  return testCases;
+}
+
+/**
+ * Apply text edits to a document
+ */
+export function applyEdits(content: string, edits: TextEdit[]): string {
+  // Sort edits in reverse order by position to apply from bottom to top
+  const sortedEdits = [...edits].sort((a, b) => {
+    if (b.range.start.line !== a.range.start.line) {
+      return b.range.start.line - a.range.start.line;
+    }
+    return b.range.start.character - a.range.start.character;
+  });
+
+  const lines = content.split("\n");
+
+  for (const edit of sortedEdits) {
+    const startLine = edit.range.start.line;
+    const startChar = edit.range.start.character;
+    const endLine = edit.range.end.line;
+    const endChar = edit.range.end.character;
+
+    const before = lines[startLine].slice(0, startChar);
+    const after = lines[endLine].slice(endChar);
+
+    const newLines = edit.newText.split("\n");
+    newLines[0] = before + newLines[0];
+    newLines[newLines.length - 1] = newLines[newLines.length - 1] + after;
+
+    lines.splice(startLine, endLine - startLine + 1, ...newLines);
+  }
+
+  return lines.join("\n");
+}
+
+/**
+ * Run a single test case
+ */
+export async function runTestCase(testCase: TestCase, validationConfig: ValidationConfig): Promise<TestResult> {
+  const strippedInput = stripMarkers(testCase.input);
+  const document = TextDocument.create("file:///test.yml", "yaml", 1, strippedInput);
+
+  // 1. Validate and get diagnostics
+  const diagnostics = await validate(document, validationConfig);
+
+  // 2.  Verify all expected diagnostics are present
+  const missingDiagnostics: string[] = [];
+  for (const marker of testCase.markers) {
+    const found = diagnostics.find(d => d.range.start.line === marker.line && d.message.includes(marker.message));
+    if (!found) {
+      missingDiagnostics.push(`line ${marker.line}: "${marker.message}"`);
+    }
+  }
+
+  if (missingDiagnostics.length > 0) {
+    return {
+      name: testCase.name,
+      passed: false,
+      error: `Missing expected diagnostics:\n  ${missingDiagnostics.join(
+        "\n  "
+      )}\n\nActual diagnostics:\n  ${diagnostics.map(d => `line ${d.range.start.line}: "${d.message}"`).join("\n  ")}`
+    };
+  }
+
+  // 3.  Collect all edits from all matching code actions
+  const allEdits: TextEdit[] = [];
+
+  for (const marker of testCase.markers) {
+    if (!marker.fix) {
+      continue;
+    }
+
+    const diagnostic = diagnostics.find(d => d.range.start.line === marker.line && d.message.includes(marker.message));
+
+    if (!diagnostic) {
+      continue; // Already reported above
+    }
+
+    const params: CodeActionParams = {
+      uri: document.uri,
+      documentContent: strippedInput,
+      diagnostics: [diagnostic],
+      featureFlags: new FeatureFlags({all: true})
+    };
+
+    const actions = getCodeActions(params);
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion -- marker.fix is checked at the start of the loop
+    const matchingAction = actions.find(a => a.title.toLowerCase().includes(marker.fix!.toLowerCase()));
+
+    if (!matchingAction) {
+      return {
+        name: testCase.name,
+        passed: false,
+        error: `Code action "${marker.fix}" not found for diagnostic on line ${marker.line}.\nAvailable actions: ${
+          actions.map(a => a.title).join(", ") || "(none)"
+        }`
+      };
+    }
+
+    if (!matchingAction.edit?.changes) {
+      return {
+        name: testCase.name,
+        passed: false,
+        error: `Code action "${marker.fix}" has no edits`
+      };
+    }
+
+    const edits = matchingAction.edit.changes[document.uri] || [];
+    allEdits.push(...edits);
+  }
+
+  // 4. Apply all edits and compare to golden file
+  const actualOutput = applyEdits(strippedInput, allEdits);
+  const expectedOutput = testCase.golden;
+
+  if (actualOutput.trim() !== expectedOutput.trim()) {
+    return {
+      name: testCase.name,
+      passed: false,
+      error: "Output does not match golden file",
+      expected: expectedOutput,
+      actual: actualOutput
+    };
+  }
+
+  return {
+    name: testCase.name,
+    passed: true
+  };
+}
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.golden.yml b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.golden.yml
new file mode 100644
index 00000000..c6f6411b
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.golden.yml
@@ -0,0 +1,9 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1
+        with:
+          path: ""
+          key: ""
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.yml b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.yml
new file mode 100644
index 00000000..50fa2f12
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key-without-inputs.yml
@@ -0,0 +1,7 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1
+        with: # want "Missing required inputs: `path`, `key`" fix="Add missing inputs: path, key"
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.golden.yml b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.golden.yml
new file mode 100644
index 00000000..81bca135
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.golden.yml
@@ -0,0 +1,10 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1
+        with:
+          restore-keys: ${{ runner.os }}-
+          path: ""
+          key: ""
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.yml b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.yml
new file mode 100644
index 00000000..a8f993d5
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/existing-with-key.yml
@@ -0,0 +1,8 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1
+        with: # want "Missing required inputs: `path`, `key`" fix="Add missing inputs: path, key"
+          restore-keys: ${{ runner.os }}-
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.golden.yml b/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.golden.yml
new file mode 100644
index 00000000..fd6ca855
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.golden.yml
@@ -0,0 +1,9 @@
+on: push
+jobs:
+    build:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/cache@v1
+              with:
+                  path: ""
+                  key: ""
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.yml b/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.yml
new file mode 100644
index 00000000..9fb635da
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/four-space-indent.yml
@@ -0,0 +1,6 @@
+on: push
+jobs:
+    build:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/cache@v1 # want "Missing required inputs: `path`, `key`" fix="Add missing inputs: path, key"
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.golden.yml b/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.golden.yml
new file mode 100644
index 00000000..c6f6411b
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.golden.yml
@@ -0,0 +1,9 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1
+        with:
+          path: ""
+          key: ""
diff --git a/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.yml b/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.yml
new file mode 100644
index 00000000..bf3fff23
--- /dev/null
+++ b/languageservice/src/code-actions/tests/testdata/quickfix/no-with-key.yml
@@ -0,0 +1,6 @@
+on: push
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/cache@v1 # want "Missing required inputs: `path`, `key`" fix="Add missing inputs: path, key"
diff --git a/languageservice/src/code-actions/types.ts b/languageservice/src/code-actions/types.ts
new file mode 100644
index 00000000..98fd351b
--- /dev/null
+++ b/languageservice/src/code-actions/types.ts
@@ -0,0 +1,23 @@
+import {FeatureFlags} from "@actions/expressions";
+import {CodeAction, Diagnostic} from "vscode-languageserver-types";
+
+export interface CodeActionContext {
+  uri: string;
+  documentContent: string;
+  featureFlags?: FeatureFlags;
+}
+
+/**
+ * A provider that can produce a code action for a given diagnostic
+ */
+export interface CodeActionProvider {
+  /**
+   * The diagnostic codes this provider handles
+   */
+  diagnosticCodes: (string | number | undefined)[];
+
+  /**
+   * Create a code action for the diagnostic, if applicable
+   */
+  createCodeAction(context: CodeActionContext, diagnostic: Diagnostic): CodeAction | undefined;
+}
diff --git a/languageservice/src/index.ts b/languageservice/src/index.ts
index 20c5c76d..c3f252c3 100644
--- a/languageservice/src/index.ts
+++ b/languageservice/src/index.ts
@@ -6,3 +6,4 @@ 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";
+export {getCodeActions, CodeActionParams} from "./code-actions/code-actions.js";
diff --git a/languageservice/src/validate-action-reference.test.ts b/languageservice/src/validate-action-reference.test.ts
index 46a39a90..1be5f478 100644
--- a/languageservice/src/validate-action-reference.test.ts
+++ b/languageservice/src/validate-action-reference.test.ts
@@ -249,7 +249,21 @@ jobs:
             line: 7
           }
         },
-        severity: DiagnosticSeverity.Error
+        severity: DiagnosticSeverity.Error,
+        code: "missing-required-inputs",
+        data: {
+          action: {
+            name: "cache",
+            owner: "actions",
+            ref: "v1"
+          },
+          missingInputs: [
+            {
+              default: undefined,
+              name: "path"
+            }
+          ]
+        }
       }
     ]);
   });
@@ -294,7 +308,25 @@ jobs:
             line: 7
           }
         },
-        severity: DiagnosticSeverity.Error
+        severity: DiagnosticSeverity.Error,
+        code: "missing-required-inputs",
+        data: {
+          action: {
+            name: "cache",
+            owner: "actions",
+            ref: "v1"
+          },
+          missingInputs: [
+            {
+              default: undefined,
+              name: "path"
+            },
+            {
+              default: undefined,
+              name: "key"
+            }
+          ]
+        }
       }
     ]);
   });
@@ -323,7 +355,25 @@ jobs:
             line: 6
           }
         },
-        severity: DiagnosticSeverity.Error
+        severity: DiagnosticSeverity.Error,
+        code: "missing-required-inputs",
+        data: {
+          action: {
+            name: "cache",
+            owner: "actions",
+            ref: "v1"
+          },
+          missingInputs: [
+            {
+              default: undefined,
+              name: "path"
+            },
+            {
+              default: undefined,
+              name: "key"
+            }
+          ]
+        }
       }
     ]);
   });
diff --git a/languageservice/src/validate-action-reference.ts b/languageservice/src/validate-action-reference.ts
index fd35e58f..7c106587 100644
--- a/languageservice/src/validate-action-reference.ts
+++ b/languageservice/src/validate-action-reference.ts
@@ -4,10 +4,22 @@ 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.js";
+import {ActionReference, parseActionReference} from "./action.js";
 import {mapRange} from "./utils/range.js";
 import {ValidationConfig} from "./validate.js";
 
+export const DiagnosticCode = {
+  MissingRequiredInputs: "missing-required-inputs"
+} as const;
+
+export interface MissingInputsDiagnosticData {
+  action: ActionReference;
+  missingInputs: Array<{
+    name: string;
+    default?: string;
+  }>;
+}
+
 /**
  * Validates action references in workflow steps, checking for valid inputs and required inputs.
  */
@@ -94,10 +106,22 @@ export async function validateActionReference(
       missingRequiredInputs.length === 1
         ? `Missing required input \`${missingRequiredInputs[0][0]}\``
         : `Missing required inputs: ${missingRequiredInputs.map(input => `\`${input[0]}\``).join(", ")}`;
+
+    // Build minimal diagnostic data - position calculation happens in the quickfix
+    const diagnosticData: MissingInputsDiagnosticData = {
+      action,
+      missingInputs: missingRequiredInputs.map(([name, input]) => ({
+        name,
+        default: input.default
+      }))
+    };
+
     diagnostics.push({
       severity: DiagnosticSeverity.Error,
-      range: mapRange((withKey || stepToken).range), // Highlight the whole step if we don't have a with key
-      message: message
+      range: mapRange((withKey || stepToken).range),
+      message: message,
+      code: DiagnosticCode.MissingRequiredInputs,
+      data: diagnosticData
     });
   }
 }
diff --git a/package-lock.json b/package-lock.json
index d3df8286..f7a1f2b1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -480,6 +480,7 @@
       "resolved": "https://registry.npmjs.org/@octokit/core/-/core-6.1.5.tgz",
       "integrity": "sha512-vvmsN0r7rguA+FySiCsbaTTobSftpIDIpPW81trAmsv9TGxg3YCujAxRYp/Uy8xmDgYCzzgulG62H7KYUFmeIg==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@octokit/auth-token": "^5.0.0",
         "@octokit/graphql": "^8.2.2",
@@ -1276,6 +1277,7 @@
       "version": "7.20.2",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@ampproject/remapping": "^2.1.0",
         "@babel/code-frame": "^7.18.6",
@@ -4118,6 +4120,7 @@
       "integrity": "sha512-dKYCMuPO1bmrpuogcjQ8z7ICCH3FP6WmxpwC03yjzGfZhj9fTJg6+bS1+UAplekbN2C+M61UNllGOOoAfGCrdQ==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@octokit/auth-token": "^4.0.0",
         "@octokit/graphql": "^7.1.0",
@@ -4645,6 +4648,7 @@
       "integrity": "sha512-sn1OZmBxUsgxMmR8a8U5QM/Wl+tyqlH//jTqCg8daTAmhAk26L2PFhcqPLlYBhYUJMZJK276qLXlHN3a83o2cg==",
       "dev": true,
       "license": "BSD-2-Clause",
+      "peer": true,
       "dependencies": {
         "@typescript-eslint/scope-manager": "5.56.0",
         "@typescript-eslint/types": "5.56.0",
@@ -4881,6 +4885,7 @@
       "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -5321,6 +5326,7 @@
         }
       ],
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "baseline-browser-mapping": "^2.9.0",
         "caniuse-lite": "^1.0.30001759",
@@ -6522,6 +6528,7 @@
       "version": "7.32.0",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@babel/code-frame": "7.12.11",
         "@eslint/eslintrc": "^0.4.3",
@@ -8390,6 +8397,7 @@
       "version": "29.3.1",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@jest/core": "^29.3.1",
         "@jest/types": "^29.3.1",
@@ -10270,6 +10278,7 @@
       "version": "2.6.7",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "whatwg-url": "^5.0.0"
       },
@@ -10625,6 +10634,7 @@
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@napi-rs/wasm-runtime": "0.2.4",
         "@yarnpkg/lockfile": "^1.1.0",
@@ -11262,6 +11272,7 @@
       "version": "2.8.3",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "bin": {
         "prettier": "bin-prettier.js"
       },
@@ -12740,7 +12751,8 @@
       "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
       "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
       "dev": true,
-      "license": "0BSD"
+      "license": "0BSD",
+      "peer": true
     },
     "node_modules/tsutils": {
       "version": "3.21.0",