fix(git): keep handoff packs on the repository filesystem

Generated-By: PostHog Code
Task-Id: b73fc361-26b5-4bae-8c3c-6e4682d0db91

Author: tatoalo

packages/agent/src/handoff-checkpoint.test.ts

@@ -1,3 +1,5 @@
+import { readdir } from "node:fs/promises";
+import path from "node:path";
 import { afterEach, describe, expect, it } from "vitest";
 import { HandoffCheckpointTracker } from "./handoff-checkpoint";
 import {
@@ -147,6 +149,18 @@ describe("HandoffCheckpointTracker", () => {
     expect(checkpoint).not.toBeNull();
     if (!checkpoint) return;
     expect(Object.keys(store.artifacts).length).toBeGreaterThan(0);
+    const gitCommonDirRaw = await cloudRepo.git([
+      "rev-parse",
+      "--git-common-dir",
+    ]);
+    const gitCommonDir = path.isAbsolute(gitCommonDirRaw)
+      ? gitCommonDirRaw
+      : path.resolve(cloudRepo.path, gitCommonDirRaw);
+    expect(
+      (await readdir(gitCommonDir)).filter((entry) =>
+        entry.startsWith("posthog-code-handoff-"),
+      ),
+    ).toEqual([]);
 
     const applyTracker = createTracker(localRepo.path, apiClient);
     await applyTracker.applyFromHandoff(checkpoint);

packages/agent/src/handoff-checkpoint.ts

@@ -1,6 +1,6 @@
 import { mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
-import { dirname, join } from "node:path";
+import { join } from "node:path";
 import {
   type GitHandoffBranchDivergence,
   type GitHandoffCheckpoint,
@@ -101,12 +101,10 @@ export class HandoffCheckpointTracker {
         indexArtifactPath: uploads.index?.storagePath,
       };
     } finally {
-      const tempDir = capture.headPack?.path
-        ? dirname(capture.headPack.path)
-        : dirname(capture.indexFile.path);
-      await this.removeIfPresent(capture.headPack?.path);
-      await this.removeIfPresent(capture.indexFile.path);
-      await rm(tempDir, { recursive: true, force: true }).catch(() => {});
+      await rm(capture.artifactDirectory, {
+        recursive: true,
+        force: true,
+      }).catch(() => {});
     }
   }
 

packages/git/src/handoff.test.ts

@@ -103,10 +103,9 @@ async function makeCloudChanges(
 }
 
 async function cleanupCapture(capture: GitHandoffCaptureResult): Promise<void> {
-  if (capture.headPack?.path) {
-    await rm(capture.headPack.path, { force: true }).catch(() => {});
-  }
-  await rm(capture.indexFile.path, { force: true }).catch(() => {});
+  await rm(capture.artifactDirectory, { recursive: true, force: true }).catch(
+    () => {},
+  );
 }
 
 async function captureAndApply(
@@ -145,6 +144,41 @@ async function captureAndApply(
 }
 
 describe("GitHandoffTracker", () => {
+  it("stores capture artifacts beside the git object store", async () => {
+    await withRepos(async (repos) => {
+      await makeCloudChanges(repos.cloudRepo, repos.cloudGit);
+
+      const captureTracker = new GitHandoffTracker({
+        repositoryPath: repos.cloudRepo,
+      });
+      const capture = await captureTracker.captureForHandoff(
+        repos.localGitState,
+      );
+      const gitCommonDir = (
+        await repos.cloudGit.raw([
+          "rev-parse",
+          "--path-format=absolute",
+          "--git-common-dir",
+        ])
+      ).trim();
+
+      try {
+        expect(path.dirname(capture.artifactDirectory)).toBe(gitCommonDir);
+        expect(path.dirname(path.dirname(capture.indexFile.path))).toBe(
+          gitCommonDir,
+        );
+        if (!capture.headPack) {
+          throw new Error("Expected handoff capture to include a pack file");
+        }
+        expect(path.dirname(path.dirname(capture.headPack.path))).toBe(
+          gitCommonDir,
+        );
+      } finally {
+        await cleanupCapture(capture);
+      }
+    });
+  }, 15000);
+
   it("captures and reapplies head, worktree, and index state from local files", async () => {
     await withRepos(async (repos) => {
       await makeCloudChanges(repos.cloudRepo, repos.cloudGit);

packages/git/src/handoff.ts

@@ -1,6 +1,5 @@
 import { spawn } from "node:child_process";
 import { copyFile, mkdtemp, readFile, rm, stat } from "node:fs/promises";
-import { tmpdir } from "node:os";
 import path from "node:path";
 import type {
   GitHandoffCheckpoint,
@@ -26,6 +25,7 @@ export interface GitHandoffArtifactFile {
 
 export interface GitHandoffCaptureResult {
   checkpoint: GitHandoffCheckpoint;
+  artifactDirectory: string;
   headPack?: GitHandoffArtifactFile;
   indexFile: GitHandoffArtifactFile;
   totalBytes: number;
@@ -92,7 +92,7 @@ export class GitHandoffTracker {
 
     const checkpoint = result.data;
     const git = createGitClient(this.repositoryPath);
-    const tempDir = await this.createTempDir(checkpoint.checkpointId);
+    const tempDir = await this.createTempDir(git, checkpoint.checkpointId);
     const checkpointRef = `${CHECKPOINT_REF_PREFIX}${checkpoint.checkpointId}`;
 
     try {
@@ -137,10 +137,14 @@ export class GitHandoffTracker {
           upstreamMergeRef: tracking.upstreamMergeRef,
           remoteUrl: tracking.remoteUrl,
         },
+        artifactDirectory: tempDir,
         headPack,
         indexFile,
         totalBytes: (headPack?.rawBytes ?? 0) + indexFile.rawBytes,
       };
+    } catch (error) {
+      await rm(tempDir, { recursive: true, force: true }).catch(() => {});
+      throw error;
     } finally {
       await deleteCheckpoint(git, checkpoint.checkpointId).catch(() => {});
     }
@@ -544,8 +548,27 @@ export class GitHandoffTracker {
     return exitCode === 0;
   }
 
-  private async createTempDir(checkpointId: string): Promise<string> {
-    return mkdtemp(joinTempPrefix(checkpointId));
+  private async createTempDir(
+    git: GitClient,
+    checkpointId: string,
+  ): Promise<string> {
+    // Git stages packs in the object store, so the destination must share its filesystem.
+    const gitCommonDir = await this.resolveGitCommonDir(git);
+    return mkdtemp(
+      path.join(gitCommonDir, `posthog-code-handoff-${checkpointId}-`),
+    );
+  }
+
+  private async resolveGitCommonDir(git: GitClient): Promise<string> {
+    const raw = await git.raw([
+      "rev-parse",
+      "--path-format=absolute",
+      "--git-common-dir",
+    ]);
+    const resolved = raw.trim() || ".git";
+    return path.isAbsolute(resolved)
+      ? resolved
+      : path.resolve(this.repositoryPath, resolved);
   }
 
   private async getGitPath(git: GitClient, gitPath: string): Promise<string> {
@@ -669,10 +692,6 @@ export class GitHandoffTracker {
   }
 }
 
-function joinTempPrefix(checkpointId: string): string {
-  return path.join(tmpdir(), `posthog-code-handoff-${checkpointId}-`);
-}
-
 export async function readHandoffLocalGitState(
   repositoryPath: string,
 ): Promise<HandoffLocalGitState> {