diff --git a/packages/app/src/utils/tool-call-parsers.test.ts b/packages/app/src/utils/tool-call-parsers.test.ts
index c02f957a07..16c2f57f5b 100644
--- a/packages/app/src/utils/tool-call-parsers.test.ts
+++ b/packages/app/src/utils/tool-call-parsers.test.ts
@@ -21,6 +21,36 @@ describe("tool-call-parsers", () => {
     expect(parsed.find((entry) => entry.type === "add")?.content).toBe("+new");
   });
 
+  it("keeps file headers in multi-file diffs", () => {
+    const parsed = parseUnifiedDiff(
+      [
+        "diff --git a/alpha.txt b/alpha.txt",
+        "--- a/alpha.txt",
+        "+++ b/alpha.txt",
+        "@@ -1 +1 @@",
+        "-color = blue",
+        "+color = green",
+        "diff --git a/beta.txt b/beta.txt",
+        "--- a/beta.txt",
+        "+++ b/beta.txt",
+        "@@ -1 +1 @@",
+        "-size = small",
+        "+size = large",
+      ].join("\n"),
+    );
+
+    expect(parsed).toEqual([
+      { type: "header", content: "diff --git a/alpha.txt b/alpha.txt" },
+      { type: "header", content: "@@ -1 +1 @@" },
+      { type: "remove", content: "-color = blue" },
+      { type: "add", content: "+color = green" },
+      { type: "header", content: "diff --git a/beta.txt b/beta.txt" },
+      { type: "header", content: "@@ -1 +1 @@" },
+      { type: "remove", content: "-size = small" },
+      { type: "add", content: "+size = large" },
+    ]);
+  });
+
   it("extracts TodoWrite task entries", () => {
     const tasks = extractTaskEntriesFromToolCall("TodoWrite", {
       todos: [
diff --git a/packages/app/src/utils/tool-call-parsers.ts b/packages/app/src/utils/tool-call-parsers.ts
index 1e89e2b303..7980d3ee5f 100644
--- a/packages/app/src/utils/tool-call-parsers.ts
+++ b/packages/app/src/utils/tool-call-parsers.ts
@@ -210,6 +210,8 @@ export function parseUnifiedDiff(diffText?: string): DiffLine[] {
   }
 
   const lines = splitIntoLines(diffText);
+  const fileHeaders = lines.filter((line) => line.startsWith("diff --git "));
+  const hasMultipleFiles = fileHeaders.length > 1;
   const diff: DiffLine[] = [];
 
   for (const line of lines) {
@@ -218,7 +220,8 @@ export function parseUnifiedDiff(diffText?: string): DiffLine[] {
       continue;
     }
 
-    if (line.startsWith("@@")) {
+    const isFileHeader = hasMultipleFiles && line.startsWith("diff --git ");
+    if (line.startsWith("@@") || isFileHeader) {
       diff.push({ type: "header", content: line });
       continue;
     }
diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
index 8fca5f24c0..0ded0806a0 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
@@ -3007,6 +3007,87 @@ describe("Codex app-server provider", () => {
     }
   });
 
+  test.each([
+    ["patch_apply_begin", undefined, "running", null],
+    ["patch_apply_end", true, "completed", null],
+    ["patch_apply_end", false, "failed", { message: "Cannot apply patch" }],
+  ] as const)(
+    "maps both files from legacy %s notifications (success: %s)",
+    async (type, success, status, error) => {
+      const appServer = createFakeCodexAppServer();
+      const session = new CodexAppServerAgentSession(
+        createConfig({ cwd: "/tmp/repo" }),
+        null,
+        createTestLogger(),
+        async () => appServer.child,
+      );
+      try {
+        await session.connect();
+        const nextTimelineItem = waitForNextTimelineItem(session);
+        appServer.child.stdout.write(
+          `${JSON.stringify({
+            method: `codex/event/${type}`,
+            params: {
+              conversationId: "thread-1",
+              msg: {
+                type,
+                call_id: "patch-array-alias",
+                changes: [
+                  {
+                    path: "/tmp/repo/src/array-alias.ts",
+                    kind: "modify",
+                    unified_diff: "@@\n-old\n+new\n",
+                  },
+                  {
+                    path: "/tmp/repo/src/second.ts",
+                    kind: "modify",
+                    unified_diff: "@@\n-before\n+after\n",
+                  },
+                ],
+                success,
+                stderr: "Cannot apply patch",
+              },
+            },
+          })}\n`,
+        );
+
+        await expect(nextTimelineItem).resolves.toEqual({
+          type: "timeline",
+          provider: "codex",
+          item: {
+            type: "tool_call",
+            callId: "patch-array-alias",
+            name: "apply_patch",
+            status,
+            error,
+            detail: {
+              type: "edit",
+              filePath: "src/array-alias.ts",
+              unifiedDiff: [
+                "diff --git a/src/array-alias.ts b/src/array-alias.ts",
+                "--- a/src/array-alias.ts",
+                "+++ b/src/array-alias.ts",
+                "@@",
+                "-old",
+                "+new",
+                "",
+                "diff --git a/src/second.ts b/src/second.ts",
+                "--- a/src/second.ts",
+                "+++ b/src/second.ts",
+                "@@",
+                "-before",
+                "+after",
+              ].join("\n"),
+            },
+          },
+        });
+        appServer.assertNoErrors();
+      } finally {
+        await session.close();
+      }
+    },
+  );
+
   test("maps Codex plan markdown to a synthetic plan tool call", () => {
     const item = mapCodexPlanToToolCall({
       callId: "plan-turn-1",
diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
index 62ceb14c70..e5ba236645 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
@@ -55,11 +55,13 @@ import { composeSystemPromptParts } from "../system-prompt.js";
 import { curateAgentActivity } from "../activity-curator.js";
 import { CodexAsyncQuestions, codexAsyncQuestionToTimeline } from "./codex/async-questions.js";
 import {
+  fileChangeToUnifiedDiff,
   mapCodexToolCallEnvelope,
   mapCodexToolCallFromThreadItem,
   normalizeCommandExecutionCommand,
   splitCodexMcpToolResultImages,
 } from "./codex/tool-call-mapper.js";
+import { normalizeCodexFilePath } from "./codex/tool-call-detail-parser.js";
 import {
   checkProviderLaunchAvailable,
   createProviderEnv,
@@ -1664,7 +1666,18 @@ export function mapCodexPatchNotificationToToolCall(params: {
   const firstPatchText = files
     .map((file) => file.content?.trim())
     .find((value): value is string => typeof value === "string" && value.length > 0);
-  const patchText = firstPatchText;
+  const patchText =
+    files.length > 1
+      ? files
+          .map((file) =>
+            fileChangeToUnifiedDiff({
+              path: normalizeCodexFilePath(file.path, params.cwd) ?? file.path,
+              kind: file.kind,
+              diff: file.content,
+            }),
+          )
+          .join("\n\n")
+      : firstPatchText;
   const patchFields = codexPatchTextFields(patchText);
   const mapped = mapCodexToolCallEnvelope({
     callId: params.callId ?? null,
diff --git a/packages/server/src/server/agent/providers/codex/tool-call-mapper.test.ts b/packages/server/src/server/agent/providers/codex/tool-call-mapper.test.ts
index 566fd10083..9b2ea095e4 100644
--- a/packages/server/src/server/agent/providers/codex/tool-call-mapper.test.ts
+++ b/packages/server/src/server/agent/providers/codex/tool-call-mapper.test.ts
@@ -528,6 +528,115 @@ describe("codex tool-call mapper", () => {
     });
   });
 
+  it.each([
+    ["inProgress", "running"],
+    ["completed", "completed"],
+  ])("keeps both fileChange diffs when the patch is %s", (status, expectedStatus) => {
+    const item = mapCodexToolCallFromThreadItem(
+      {
+        type: "fileChange",
+        id: "codex-two-files",
+        status,
+        changes: [
+          {
+            path: "/tmp/repo/alpha.txt",
+            kind: { type: "update", move_path: null },
+            diff: "@@ -1 +1 @@\n-color = blue\n+color = green\n",
+          },
+          {
+            path: "/tmp/repo/beta.txt",
+            kind: { type: "update", move_path: null },
+            diff: "@@ -1 +1 @@\n-size = small\n+size = large\n",
+          },
+        ],
+      },
+      { cwd: "/tmp/repo" },
+    );
+
+    expect(item).toEqual({
+      type: "tool_call",
+      callId: "codex-two-files",
+      name: "apply_patch",
+      status: expectedStatus,
+      error: null,
+      detail: {
+        type: "edit",
+        filePath: "alpha.txt",
+        unifiedDiff: [
+          "diff --git a/alpha.txt b/alpha.txt",
+          "--- a/alpha.txt",
+          "+++ b/alpha.txt",
+          "@@ -1 +1 @@",
+          "-color = blue",
+          "+color = green",
+          "",
+          "diff --git a/beta.txt b/beta.txt",
+          "--- a/beta.txt",
+          "+++ b/beta.txt",
+          "@@ -1 +1 @@",
+          "-size = small",
+          "+size = large",
+        ].join("\n"),
+      },
+    });
+  });
+
+  it("keeps update, add, and delete changes in one fileChange diff", () => {
+    const item = mapCodexToolCallFromThreadItem(
+      {
+        type: "fileChange",
+        id: "codex-mixed-files",
+        status: "completed",
+        changes: [
+          {
+            path: "/tmp/repo/alpha.txt",
+            kind: { type: "update", move_path: null },
+            diff: "--- a/alpha.txt\n+++ b/alpha.txt\n@@ -1 +1 @@\n-blue\n+green\n",
+          },
+          { path: "/tmp/repo/new.txt", kind: { type: "add" }, diff: "new\n\nvalue\n" },
+          { path: "/tmp/repo/old.txt", kind: { type: "delete" }, diff: "old\n\nvalue\n" },
+        ],
+      },
+      { cwd: "/tmp/repo" },
+    );
+
+    expect(item).toEqual({
+      type: "tool_call",
+      callId: "codex-mixed-files",
+      name: "apply_patch",
+      status: "completed",
+      error: null,
+      detail: {
+        type: "edit",
+        filePath: "alpha.txt",
+        unifiedDiff: [
+          "diff --git a/alpha.txt b/alpha.txt",
+          "--- a/alpha.txt",
+          "+++ b/alpha.txt",
+          "@@ -1 +1 @@",
+          "-blue",
+          "+green",
+          "",
+          "diff --git a/new.txt b/new.txt",
+          "--- /dev/null",
+          "+++ b/new.txt",
+          "@@ -0,0 +1,3 @@",
+          "+new",
+          "+",
+          "+value",
+          "",
+          "diff --git a/old.txt b/old.txt",
+          "--- a/old.txt",
+          "+++ /dev/null",
+          "@@ -1,3 +0,0 @@",
+          "-old",
+          "-",
+          "-value",
+        ].join("\n"),
+      },
+    });
+  });
+
   it("maps fileChange object-style change payloads keyed by path", () => {
     const item = expectMapped(
       mapCodexToolCallFromThreadItem(
diff --git a/packages/server/src/server/agent/providers/codex/tool-call-mapper.ts b/packages/server/src/server/agent/providers/codex/tool-call-mapper.ts
index 64629bc5d9..980684191f 100644
--- a/packages/server/src/server/agent/providers/codex/tool-call-mapper.ts
+++ b/packages/server/src/server/agent/providers/codex/tool-call-mapper.ts
@@ -400,7 +400,7 @@ function contentToDeletionDiff(filePath: string, content: string): string {
   output.push(`diff --git a/${filePath} b/${filePath}`);
   output.push(`--- a/${filePath}`);
   output.push(`+++ /dev/null`);
-  const nonEmpty = lines.filter((l) => l.length > 0 || lines.indexOf(l) < lines.length - 1);
+  const nonEmpty = lines.slice(0, lines.at(-1) === "" ? -1 : undefined);
   if (nonEmpty.length > 0) {
     output.push(`@@ -1,${nonEmpty.length} +0,0 @@`);
     for (const line of nonEmpty) {
@@ -740,6 +740,9 @@ function parseFileChangePath(
 }
 
 function parseFileChangeKind(entry: Record<string, unknown>): string | undefined {
+  if (isRecord(entry.kind) && typeof entry.kind.type === "string") {
+    return entry.kind.type;
+  }
   return (
     (typeof entry.kind === "string" && entry.kind) ||
     (typeof entry.type === "string" && entry.type) ||
@@ -839,6 +842,28 @@ function resolveFileChangeTextFields(file: CodexFileChangeEntry | undefined): {
   return asEditTextFields(file.diff);
 }
 
+export function fileChangeToUnifiedDiff(file: CodexFileChangeEntry): string {
+  const { unifiedDiff, newString } = resolveFileChangeTextFields(file);
+  if (unifiedDiff?.startsWith("diff --git")) {
+    return unifiedDiff.replace(/\r?\n$/, "");
+  }
+  const header = `diff --git a/${file.path} b/${file.path}`;
+  if (unifiedDiff?.startsWith("--- ")) {
+    return `${header}\n${unifiedDiff.replace(/\r?\n$/, "")}`;
+  }
+  const left = file.kind === "add" ? "/dev/null" : `a/${file.path}`;
+  const right = file.kind === "delete" ? "/dev/null" : `b/${file.path}`;
+  const lines = [header, `--- ${left}`, `+++ ${right}`];
+  if (unifiedDiff) {
+    lines.push(unifiedDiff.replace(/\r?\n$/, ""));
+  } else if (newString) {
+    const contentLines = newString.replace(/\r\n/g, "\n").replace(/\n$/, "").split("\n");
+    lines.push(`@@ -0,0 +1,${contentLines.length} @@`);
+    lines.push(...contentLines.map((line) => `+${line}`));
+  }
+  return lines.join("\n");
+}
+
 function mapFileChangeItem(
   item: z.infer<typeof CodexFileChangeItemSchema>,
   options?: CodexMapperOptions,
@@ -873,17 +898,16 @@ function mapFileChangeItem(
   const error = item.error ?? null;
   const status = normalizeToolCallStatus(item.status, error, output);
   const firstFile = files[0];
-  const firstTextFields = resolveFileChangeTextFields(firstFile);
-  const hasFirstTextFields = Object.keys(firstTextFields).length > 0;
+  const textFields =
+    files.length > 1
+      ? { unifiedDiff: files.map(fileChangeToUnifiedDiff).join("\n\n") }
+      : resolveFileChangeTextFields(firstFile);
+  const hasTextFields = Object.keys(textFields).length > 0;
   const input = toNullableObject({
     ...inputBase,
-    ...(firstFile?.path && hasFirstTextFields ? { path: firstFile.path } : {}),
-    ...(hasFirstTextFields && firstTextFields.unifiedDiff
-      ? { patch: firstTextFields.unifiedDiff }
-      : {}),
-    ...(hasFirstTextFields && firstTextFields.newString
-      ? { content: firstTextFields.newString }
-      : {}),
+    ...(firstFile?.path && hasTextFields ? { path: firstFile.path } : {}),
+    ...(hasTextFields && textFields.unifiedDiff ? { patch: textFields.unifiedDiff } : {}),
+    ...(hasTextFields && textFields.newString ? { content: textFields.newString } : {}),
   });
 
   return {