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)