fix: improve merge verification and dashboard behavior

packages/engine/src/merger.test.ts

@@ -2152,6 +2152,57 @@ describe("aiMergeTask — deterministic merge verification", () => {
     );
   });
 
+  it("does not fail verification when verbose test output exceeds buffer after exit 0", async () => {
+    mockedExecSync.mockImplementation((cmd: any) => {
+      const cmdStr = String(cmd);
+      if (cmdStr.includes("rev-parse --verify")) return Buffer.from("abc123");
+      if (cmdStr.includes("git log")) return "- feat: something" as any;
+      if (cmdStr.includes("merge-base")) return Buffer.from("abc123");
+      if (cmdStr.includes("git diff") && cmdStr.includes("--stat")) return "1 file changed" as any;
+      if (cmdStr.includes("merge --squash")) return Buffer.from("");
+      if (cmdStr.includes("vitest run")) {
+        const error = new Error("stdout maxBuffer length exceeded") as any;
+        error.code = "ENOBUFS";
+        error.status = 0;
+        error.stdout = "tests passed but output was verbose";
+        error.stderr = "";
+        throw error;
+      }
+      if (cmdStr.includes("diff --cached --quiet")) return "1" as any;
+      if (cmdStr.includes("diff --cached") && !cmdStr.includes("--quiet")) return "" as any;
+      if (cmdStr.includes("branch -d") || cmdStr.includes("branch -D")) return Buffer.from("");
+      if (cmdStr.includes("worktree remove")) return Buffer.from("");
+      if (cmdStr === "git rev-parse HEAD" || cmdStr.startsWith("git rev-parse HEAD ")) return "mergedcommit123";
+      if (cmdStr.includes("show --shortstat")) return "1 file changed, 1 insertion(+)" as any;
+      return Buffer.from("");
+    });
+
+    mockedCreateHaiAgent.mockImplementation(async () => ({
+      session: {
+        prompt: vi.fn().mockResolvedValue(undefined),
+        dispose: vi.fn(),
+      },
+    }) as any);
+
+    const store = createMockStore(
+      { id: "FN-050", worktree: "/tmp/root/.worktrees/KB-050" },
+      [{ id: "FN-050", worktree: "/tmp/root/.worktrees/KB-050", column: "in-review" } as Task],
+    );
+    (store.getSettings as ReturnType<typeof vi.fn>).mockResolvedValue({
+      ...DEFAULT_SETTINGS,
+      testCommand: "vitest run",
+    });
+
+    const result = await aiMergeTask(store, "/tmp/root", "FN-050");
+
+    expect(result.merged).toBe(true);
+    expect(store.moveTask).toHaveBeenCalledWith("FN-050", "done");
+    expect(store.logEntry).toHaveBeenCalledWith(
+      "FN-050",
+      "[verification] test command succeeded (exit 0, output exceeded buffer)",
+    );
+  });
+
   it("fails merge when buildCommand fails and does not move task to done", async () => {
     // Setup exec mock that will be updated after agent commits
     mockedExecSync.mockImplementation((cmd: any) => {

packages/engine/src/merger.ts

@@ -63,6 +63,14 @@ const DEPENDENCY_SYNC_TRIGGER_PATTERNS = [
   "packages/*/package.json",
 ];
 
+const VERIFICATION_COMMAND_MAX_BUFFER = 50 * 1024 * 1024;
+const VERIFICATION_LOG_MAX_CHARS = 20_000;
+
+function truncateVerificationOutput(output: string): string {
+  if (output.length <= VERIFICATION_LOG_MAX_CHARS) return output;
+  return `... output truncated to last ${VERIFICATION_LOG_MAX_CHARS} characters ...\n${output.slice(-VERIFICATION_LOG_MAX_CHARS)}`;
+}
+
 /** Check if a path matches a glob pattern (simple glob support: * and **) */
 function matchGlob(path: string, pattern: string): boolean {
   // Handle ** which matches across directory boundaries (must do before single *)
@@ -306,6 +314,7 @@ async function runVerificationCommand(
     const output = execSync(command, {
       cwd: rootDir,
       encoding: "utf-8",
+      maxBuffer: VERIFICATION_COMMAND_MAX_BUFFER,
       timeout: 300_000, // 5 minute timeout for verification commands
       stdio: ["pipe", "pipe", "pipe"],
     });
@@ -318,10 +327,22 @@ async function runVerificationCommand(
     result.stdout = error.stdout?.toString() || "";
     result.stderr = error.stderr?.toString() || "";
     result.exitCode = error.status ?? null;
-    result.success = false;
+    const maxBufferExceeded = error.code === "ENOBUFS"
+      || error.code === "ERR_CHILD_PROCESS_STDIO_MAXBUFFER"
+      || error.message?.includes("maxBuffer");
+    result.success = maxBufferExceeded && result.exitCode === 0;
+
+    if (result.success) {
+      mergerLog.log(`${taskId}: ${type} command succeeded (exit 0, output exceeded buffer)`);
+      await store.logEntry(
+        taskId,
+        `[verification] ${type} command succeeded (exit 0, output exceeded buffer)`,
+      );
+      return result;
+    }
 
     // Build a useful error summary
-    const summary = result.stderr || result.stdout || error.message || "Unknown error";
+    const summary = truncateVerificationOutput(result.stderr || result.stdout || error.message || "Unknown error");
     mergerLog.error(`${taskId}: ${type} command failed (exit ${result.exitCode}): ${summary.trim()}`);
     await store.logEntry(
       taskId,