Fix file creation

src/CodexEventHandler.ts

@@ -153,19 +153,33 @@ export class CodexEventHandler {
     }
 
     private async createPatchContent(change: FileUpdateChange): Promise<ToolCallContent | null> {
-        const oldContent = await readFile(change.path, { encoding: "utf8" });
+        if (change.kind.type === "add" && !this.isUnifiedDiff(change.diff)) {
+            // For new files, diff may contain raw file content instead of a patch
+            return {
+                type: "diff",
+                oldText: null,
+                newText: change.diff,
+                path: change.path,
+            }
+        }
+
+        const oldContent = change.kind.type === "add" ? "" : await readFile(change.path, { encoding: "utf8" });
         const newContent = applyPatch(oldContent, change.diff);
-        if (!newContent) {
+        if (newContent === false) {
             return null
         }
         return {
             type: "diff",
-            oldText: oldContent,
+            oldText: change.kind.type === "add" ? null : oldContent,
             newText: newContent,
             path: change.path,
         }
     }
 
+    private isUnifiedDiff(content: string): boolean {
+        return content.startsWith('--- ') || content.includes('\n--- ');
+    }
+
     private async createCommandEvent(item: ThreadItem & { "type": "commandExecution" }): Promise<UpdateSessionEvent> {
         const commandAction = item.commandActions.length === 1 ? item.commandActions[0] : undefined;
         if (commandAction) {

src/__tests__/CodexACPAgent/data/file-change-add-multiple-files.json

@@ -0,0 +1,29 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "tool_call",
+        "toolCallId": "file-change-2",
+        "title": "Editing files",
+        "kind": "edit",
+        "status": "completed",
+        "content": [
+          {
+            "type": "diff",
+            "oldText": null,
+            "newText": "class FileA\n",
+            "path": "/test/project/FileA.kt"
+          },
+          {
+            "type": "diff",
+            "oldText": null,
+            "newText": "class FileB\n",
+            "path": "/test/project/FileB.kt"
+          }
+        ]
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/file-change-add-new-file.json

@@ -0,0 +1,23 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "tool_call",
+        "toolCallId": "file-change-1",
+        "title": "Editing files",
+        "kind": "edit",
+        "status": "completed",
+        "content": [
+          {
+            "type": "diff",
+            "oldText": null,
+            "newText": "package test.project\n\nclass NewFile {\n    fun hello() = \"Hello\"\n}\n",
+            "path": "/test/project/NewFile.kt"
+          }
+        ]
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/file-change-add-raw-content.json

@@ -0,0 +1,23 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "tool_call",
+        "toolCallId": "file-change-raw",
+        "title": "Editing files",
+        "kind": "edit",
+        "status": "completed",
+        "content": [
+          {
+            "type": "diff",
+            "oldText": null,
+            "newText": "fun main() {\n    println(\"Hello, World!\")\n}\n",
+            "path": "/test/project/RawFile.kt"
+          }
+        ]
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/data/file-change-delete-file.json

@@ -0,0 +1,23 @@
+{
+  "method": "sessionUpdate",
+  "args": [
+    {
+      "sessionId": "test-session-id",
+      "update": {
+        "sessionUpdate": "tool_call",
+        "toolCallId": "file-change-3",
+        "title": "Editing files",
+        "kind": "edit",
+        "status": "completed",
+        "content": [
+          {
+            "type": "diff",
+            "oldText": "package test.project\n\nclass OldFile {}",
+            "newText": "",
+            "path": "/test/project/OldFile.kt"
+          }
+        ]
+      }
+    }
+  ]
+}

src/__tests__/CodexACPAgent/file-change-events.test.ts

@@ -0,0 +1,204 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import type { SessionState } from '../../CodexAcpServer';
+import type { ServerNotification } from '../../app-server';
+import { createCodexMockTestFixture, type CodexMockTestFixture } from '../acp-test-utils';
+
+const { mockFiles, mockFileContent, clearMockFiles } = vi.hoisted(() => {
+    const files = new Map<string, string>();
+    return {
+        mockFiles: files,
+        mockFileContent: (path: string, content: string) => files.set(path, content),
+        clearMockFiles: () => files.clear(),
+    };
+});
+
+vi.mock('node:fs/promises', () => ({
+    readFile: (path: string) => {
+        const content = mockFiles.get(path);
+        if (content !== undefined) {
+            return Promise.resolve(content);
+        }
+        return Promise.reject(new Error(`ENOENT: no such file or directory, open '${path}'`));
+    },
+}));
+
+describe('CodexEventHandler - file change events', () => {
+    let mockFixture: CodexMockTestFixture;
+    const sessionId = 'test-session-id';
+
+    beforeEach(() => {
+        mockFixture = createCodexMockTestFixture();
+        clearMockFiles();
+        mockFileContent('/test/project/OldFile.kt', 'package test.project\n\nclass OldFile {}');
+    });
+
+    const sessionState: SessionState = {
+        pendingPrompt: null,
+        sessionMetadata: {
+            sessionId,
+            currentModelId: 'model-id',
+            models: [],
+        },
+    };
+
+    async function setupAndSendNotifications(notifications: ServerNotification[]) {
+        const codexAcpAgent = mockFixture.getCodexAcpAgent();
+
+        mockFixture.getCodexAppServerClient().turnStart = vi.fn().mockResolvedValue(undefined);
+        mockFixture.getCodexAppServerClient().awaitTurnCompleted = vi.fn().mockResolvedValue(undefined);
+
+        vi.spyOn(codexAcpAgent, 'getSessionState').mockReturnValue(sessionState);
+
+        await codexAcpAgent.prompt({
+            sessionId,
+            prompt: [{ type: 'text', text: 'test prompt' }],
+        });
+
+        mockFixture.clearAcpConnectionDump();
+
+        for (const notification of notifications) {
+            mockFixture.sendServerNotification(notification);
+        }
+
+        await vi.waitFor(() => {
+            const dump = mockFixture.getAcpConnectionDump([]);
+            expect(dump.length).toBeGreaterThan(0);
+        });
+    }
+
+    it('should handle new file creation', async () => {
+        const newFileNotification: ServerNotification = {
+            method: 'item/started',
+            params: {
+                threadId: 'thread-1',
+                turnId: 'turn-1',
+                item: {
+                    type: 'fileChange',
+                    id: 'file-change-1',
+                    changes: [
+                        {
+                            path: '/test/project/NewFile.kt',
+                            kind: { type: 'add' },
+                            diff: `--- /dev/null
++++ /test/project/NewFile.kt
+@@ -0,0 +1,5 @@
++package test.project
++
++class NewFile {
++    fun hello() = "Hello"
++}`,
+                        },
+                    ],
+                    status: 'completed',
+                },
+            },
+        };
+
+        await setupAndSendNotifications([newFileNotification]);
+
+        await expect(mockFixture.getAcpConnectionDump(['id'])).toMatchFileSnapshot(
+            'data/file-change-add-new-file.json'
+        );
+    });
+
+    it('should handle multiple new files in single change', async () => {
+        const multiFileNotification: ServerNotification = {
+            method: 'item/started',
+            params: {
+                threadId: 'thread-1',
+                turnId: 'turn-1',
+                item: {
+                    type: 'fileChange',
+                    id: 'file-change-2',
+                    changes: [
+                        {
+                            path: '/test/project/FileA.kt',
+                            kind: { type: 'add' },
+                            diff: `--- /dev/null
++++ /test/project/FileA.kt
+@@ -0,0 +1 @@
++class FileA`,
+                        },
+                        {
+                            path: '/test/project/FileB.kt',
+                            kind: { type: 'add' },
+                            diff: `--- /dev/null
++++ /test/project/FileB.kt
+@@ -0,0 +1 @@
++class FileB`,
+                        },
+                    ],
+                    status: 'completed',
+                },
+            },
+        };
+
+        await setupAndSendNotifications([multiFileNotification]);
+
+        await expect(mockFixture.getAcpConnectionDump(['id'])).toMatchFileSnapshot(
+            'data/file-change-add-multiple-files.json'
+        );
+    });
+
+    it('should handle new file creation with raw content', async () => {
+        // Codex sends raw file content (not unified diff) for new files
+        const newFileNotification: ServerNotification = {
+            method: 'item/started',
+            params: {
+                threadId: 'thread-1',
+                turnId: 'turn-1',
+                item: {
+                    type: 'fileChange',
+                    id: 'file-change-raw',
+                    changes: [
+                        {
+                            path: '/test/project/RawFile.kt',
+                            kind: { type: 'add' },
+                            diff: 'fun main() {\n    println("Hello, World!")\n}\n',
+                        },
+                    ],
+                    status: 'completed',
+                },
+            },
+        };
+
+        await setupAndSendNotifications([newFileNotification]);
+
+        await expect(mockFixture.getAcpConnectionDump(['id'])).toMatchFileSnapshot(
+            'data/file-change-add-raw-content.json'
+        );
+    });
+
+    it('should handle file deletion', async () => {
+        const deleteFileNotification: ServerNotification = {
+            method: 'item/started',
+            params: {
+                threadId: 'thread-1',
+                turnId: 'turn-1',
+                item: {
+                    type: 'fileChange',
+                    id: 'file-change-3',
+                    changes: [
+                        {
+                            path: '/test/project/OldFile.kt',
+                            kind: { type: 'delete' },
+                            diff: `--- /test/project/OldFile.kt
++++ /dev/null
+@@ -1,3 +0,0 @@
+-package test.project
+-
+-class OldFile {}`,
+                        },
+                    ],
+                    status: 'completed',
+                },
+            },
+        };
+
+        await setupAndSendNotifications([deleteFileNotification]);
+
+        await expect(mockFixture.getAcpConnectionDump(['id'])).toMatchFileSnapshot(
+            'data/file-change-delete-file.json'
+        );
+    });
+});