fix(issue-36): the loop passes every delegated prompt as a file; a wrapper that cannot start is a failed submit, on the first try and on the retry

delegate_job writes the prompt to a temp file under the control root's .mam/
and hands the wrapper --prompt-file; the file is removed once the wrapper
returns. An OSError from starting the wrapper becomes a failed submit (rc 126)
that the existing error branch logs, so the session-busy retry no longer
dereferences a missing result. A retry that yields no job id, and a
compliance job that cannot be registered, are now logged instead of silent.

The collector caps are documented as the size of the evidence a reviewer is
shown; delivery has no cap of its own any more. The loop skill notes that a
pipeline hides the loop's exit code.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/loop/runner.py

@@ -464,7 +464,17 @@ class LoopRunner:
         if not wrapper_script.exists():
             wrapper_script = Path(__file__).resolve().parent.parent / "multi-agent-mux-delegate-job" / "multi-agent-mux-delegate-job"
 
-        def _run_cmd(p_text: str):
+        def _run_cmd(p_text: str) -> subprocess.CompletedProcess:
+            # Issue #36: the prompt goes by file. One argv string is capped at
+            # MAX_ARG_STRLEN (131,072 bytes on Linux), and a review prompt
+            # carries the whole diff. The wrapper blocks until the job ends,
+            # so nothing reads the file after it returns.
+            self.mam_dir.mkdir(parents=True, exist_ok=True)
+            with tempfile.NamedTemporaryFile("w", encoding="utf-8", dir=self.mam_dir,
+                                             prefix=f"prompt-{self.loop_id}-", suffix=".md",
+                                             delete=False) as fh:
+                fh.write(p_text)
+                prompt_file = fh.name
             cmd = [
                 "bash", str(wrapper_script), "submit",
                 "--agent-session", self.session_label(agent_session),
@@ -472,12 +482,24 @@ class LoopRunner:
                 "--type", "direct",
                 "--role", role,
                 "--registry-dir", str(self.jobs_dir),
-                "--prompt", p_text,
+                "--prompt-file", prompt_file,
             ] + self.contract_args()
             env = dict(os.environ)
             if "DELEGATE_JOB_PYTHON" not in env:
                 env["DELEGATE_JOB_PYTHON"] = sys.executable
-            return subprocess.run(cmd, capture_output=True, text=True, cwd=str(self.workspace_root), env=env)
+            try:
+                return subprocess.run(cmd, capture_output=True, text=True, cwd=str(self.workspace_root), env=env)
+            except OSError as e:
+                # A wrapper that cannot start is a failed submit (126, the shell's
+                # "cannot execute"), on the first try and on the retry alike.
+                msg = (f"cannot start the wrapper: {e} "
+                       f"(prompt {len(p_text.encode('utf-8'))} bytes, wrapper {wrapper_script})")
+                return subprocess.CompletedProcess(cmd, 126, "", msg)
+            finally:
+                try:
+                    os.unlink(prompt_file)
+                except OSError:
+                    pass
 
         res = _run_cmd(prompt)
         match = re.search(r"registered job:\s*([A-Za-z0-9_-]+)", res.stdout)
@@ -500,6 +522,7 @@ class LoopRunner:
                         self.failed_submit_jobs.add(job_id_retry)
                         log_error(f"delegate_job retry failed (exit {res_retry.returncode}):\n{res_retry.stderr or res_retry.stdout}")
                     return job_id_retry
+                log_error(f"delegate_job retry failed (exit {res_retry.returncode}):\n{res_retry.stderr or res_retry.stdout}")
             if job_id:
                 self.created_jobs.append(job_id)
                 self.failed_submit_jobs.add(job_id)
@@ -1362,6 +1385,8 @@ class LoopRunner:
                             comp_jid = self._dispatch(self.creator, creator_type, "Worker", comply_prompt)
                             if comp_jid:
                                 self.wait_for_job(comp_jid)
+                            else:
+                                log_error("Failed to register Creator compliance job.")
 
         # Promotion
         if self.plan_mode and self.current_plan and self.plan_job_id: