Preserve valid agent retry progress

src/lai_automation/git.py

@@ -94,6 +94,15 @@ class GitWorkspace:
         self._git("reset", "--hard", "HEAD")
         self._git("clean", "-fd")
 
+    def checkpoint(self) -> str:
+        self._git("add", "--all")
+        return self._git("stash", "create").stdout.strip()
+
+    def restore_checkpoint(self, checkpoint: str | None) -> None:
+        self.discard_changes()
+        if checkpoint:
+            self._git("stash", "apply", checkpoint)
+
     def summary(self) -> ChangeSummary:
         self._git("add", "-N", "--all")
         output = self._git("diff", "--numstat").stdout

src/lai_automation/worker.py

@@ -55,6 +55,7 @@ class AutomationWorker:
             LOG.info("Report %s branch=%s workspace ready", report.id, workspace.branch)
             task = build_task(report)
             metadata["agent_output"] = []
+            valid_checkpoint: str | None = None
             for attempt in range(1, self.settings.max_agent_attempts + 1):
                 LOG.info(
                     "Report %s agent attempt %s/%s starting",
@@ -108,15 +109,22 @@ class AutomationWorker:
                         report.id,
                         attempt,
                     )
-                    workspace.discard_changes()
+                    workspace.restore_checkpoint(valid_checkpoint)
+                    restored_state = (
+                        "The last syntax-valid changes were restored. Correct them without recreating "
+                        "the malformed edit."
+                        if valid_checkpoint
+                        else "The malformed attempt was discarded. Start again from the clean repository."
+                    )
                     task = build_retry_task(
                         report,
                         RuntimeError(
-                            f"{exception}\nThe malformed attempt was discarded. Start again from the clean "
-                            "repository, make smaller edits, and run php -l on each changed PHP file."
+                            f"{exception}\n{restored_state} Make smaller edits and run php -l on each "
+                            "changed PHP file."
                         ),
                     )
                     continue
+                valid_checkpoint = workspace.checkpoint()
                 try:
                     metadata["tests"] = self._run_tests(workspace, report.id, attempt)
                     LOG.info("Report %s attempt %s validation passed", report.id, attempt)

tests/test_git.py

@@ -53,4 +53,34 @@ def test_discard_changes_restores_clean_disposable_workspace(tmp_path) -> None:
     workspace.discard_changes()
 
     assert tracked.read_text() == "<?php\nreturn [];\n"
-    assert not untracked.exists()
+    assert not untracked.exists()
+
+
+def test_checkpoint_restores_last_valid_changes(tmp_path) -> None:
+    workspace = GitWorkspace(settings(workspace_root=tmp_path), 4)
+    workspace.path.mkdir()
+    subprocess.run(["git", "init"], cwd=workspace.path, check=True, capture_output=True)
+    subprocess.run(
+        ["git", "config", "user.email", "test@example.invalid"],
+        cwd=workspace.path,
+        check=True,
+    )
+    subprocess.run(
+        ["git", "config", "user.name", "Test"],
+        cwd=workspace.path,
+        check=True,
+    )
+    tracked = workspace.path / "config.php"
+    tracked.write_text("<?php\nreturn [];\n")
+    subprocess.run(["git", "add", "."], cwd=workspace.path, check=True)
+    subprocess.run(["git", "commit", "-m", "base"], cwd=workspace.path, check=True, capture_output=True)
+    tracked.write_text("<?php\nreturn ['valid'];\n")
+    added = workspace.path / "test.php"
+    added.write_text("<?php\n")
+    checkpoint = workspace.checkpoint()
+    tracked.write_text("<?php\nreturn [broken;\n")
+
+    workspace.restore_checkpoint(checkpoint)
+
+    assert tracked.read_text() == "<?php\nreturn ['valid'];\n"
+    assert added.exists()

tests/test_worker.py

@@ -139,6 +139,7 @@ def test_php_syntax_failure_discards_attempt_before_full_validation() -> None:
         Mock(returncode=0, stdout="No syntax errors", stderr=""),
         Mock(returncode=0, stdout="No syntax errors", stderr=""),
     ]
+    workspace.checkpoint.return_value = "valid-checkpoint"
     workspace.commit.return_value = "commit-id"
 
     with patch("lai_automation.worker.GitWorkspace", return_value=workspace):
@@ -147,10 +148,58 @@ def test_php_syntax_failure_discards_attempt_before_full_validation() -> None:
     assert worker.agent.run.call_count == 2
     assert "unexpected token" in worker.agent.run.call_args_list[1].args[1]
     assert "clean repository" in worker.agent.run.call_args_list[1].args[1]
-    workspace.discard_changes.assert_called_once()
+    workspace.restore_checkpoint.assert_called_once_with(None)
     worker._run_tests.assert_called_once()
 
 
+def test_malformed_retry_restores_last_syntax_valid_attempt() -> None:
+    report = FailureReport(
+        id=56,
+        chat_message_id=1,
+        source="user_feedback",
+        category="incorrect_answer",
+        user_feedback="Wrong hours",
+        feedback_type="wrong_result",
+        expected_behavior="Use time registration",
+        prompt="Hours in April",
+        response="0 hours",
+        sql_query="SELECT 0",
+        error_message=None,
+        context={},
+    )
+    config = settings(mode="pr", dry_run=False, gitea_token="token", max_agent_attempts=3)
+    worker = AutomationWorker(config)
+    worker.reports = Mock()
+    worker.reports.claim_next.return_value = report
+    worker.agent = Mock()
+    worker.agent.run.side_effect = ["valid but failing", "broken retry", "corrected retry"]
+    worker.gitea = Mock()
+    worker._run_tests = Mock(side_effect=[RuntimeError("Expected hour rule"), []])
+    workspace = Mock()
+    workspace.path = Path("/tmp/nonexistent-workspace")
+    workspace.branch = "ai/failure-56"
+    workspace.summary.return_value = ChangeSummary(
+        ("config/erp_semantics.php", "tests/Unit/FixTest.php"), 20, 2
+    )
+    workspace.run_args.side_effect = [
+        Mock(returncode=0, stdout="No syntax errors", stderr=""),
+        Mock(returncode=0, stdout="No syntax errors", stderr=""),
+        Mock(returncode=255, stdout="Parse error", stderr="unexpected token"),
+        Mock(returncode=0, stdout="No syntax errors", stderr=""),
+        Mock(returncode=0, stdout="No syntax errors", stderr=""),
+    ]
+    workspace.checkpoint.side_effect = ["checkpoint-1", "checkpoint-3"]
+    workspace.commit.return_value = "commit-id"
+
+    with patch("lai_automation.worker.GitWorkspace", return_value=workspace):
+        assert worker.run_once()
+
+    assert worker.agent.run.call_count == 3
+    workspace.restore_checkpoint.assert_called_once_with("checkpoint-1")
+    assert "last syntax-valid changes were restored" in worker.agent.run.call_args_list[2].args[1]
+    assert worker._run_tests.call_count == 2
+
+
 def test_failed_validation_gets_one_correction_before_pr() -> None:
     report = FailureReport(
         id=13,