tablet 55: the row that was a label — the Sanhedrin's example request crashed its own gate

Verified live 2026-10-19: Tamid's own example for POST /chatzer/sanhedrin
(a case with `sides`) answered 500. The router passed the sides LIST as
the case context; halt_monitor:check_avodah_zarah/1 reads a map, maps:get
raised, and the halt monitor and escalation gen_servers died with the
caller's input (supervisor restarted them; health stayed 8/8). The router
then matched {:ok, decision} on the error and made a 500 of its own.

- sanhedrin/src/halt_monitor.erl: do_check_case refuses a non-map
  context as {halt, malformed_case, _} and stays standing. EUnit 49/0
  with the new halt_malformed_context_test.
- router.ex process_sanhedrin: sides validated at the kiyor (422 on a bad
  shape), carried as context %{sides: sides}; a Sanhedrin refusal answers
  422 SANHEDRIN_HALTED, a failure 503 SANHEDRIN_UNAVAILABLE. Two new
  router tests, one asserting the gate processes survive the example.
  Elixir 624/0.
- specs/broken_tablets/README.md: tablet 55, including what is NOT fixed
  — a panel of one accepting on zero references under a grounded-
  sounding sentence, the ignored complexity hint, no panel manna spent,
  no L3 record. The row in Tamid is still larger than the thing behind it.

Doorpost pin unchanged (no @spec_files touched; scripts/doorpost_check.py
passes).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

vav_pipeline/lib/vav_pipeline/bigdei_kodesh/router.ex

@@ -1084,32 +1084,83 @@ defmodule VavPipeline.BigdeiKodesh.Router do
         resubmit: true
       })
     else
-      case_ref = generate_id()
+      # Tablet 55: the sides are the caller's arguments, not the halt
+      # gate's context. The gate reads a MAP (authority_source, action);
+      # handing it the sides list crashed the halt monitor and escalation
+      # with the Tamid's own example request. The sides ride inside the
+      # map, their shape checked at the door; and a refusal from the
+      # Sanhedrin is answered, not matched into a 500.
+      with {:ok, sides} <- sanhedrin_sides(params["sides"]) do
+        case_ref = generate_id()
 
-      {:ok, decision} =
-        VavPipeline.SanhedrinClient.submit_case(%{
-          case_ref: case_ref,
-          complexity: :simple,
-          question: case_text,
-          context: params["sides"] || %{},
-          requested_by: "chatzer"
-        })
+        case VavPipeline.SanhedrinClient.submit_case(%{
+               case_ref: case_ref,
+               complexity: :simple,
+               question: case_text,
+               context: %{sides: sides},
+               requested_by: "chatzer"
+             }) do
+          {:ok, decision} ->
+            send_json(conn, 200, %{
+              case_ref: decision.case_ref,
+              deliberation: %{
+                panel_size: decision.panel_size,
+                majority: decision.majority,
+                minority: decision.minority,
+                outcome: decision.outcome,
+                processing_time_ms: decision.deliberation_time_ms
+              },
+              note: "This is the system's reasoning, not a binding ruling. A human beit din may reach a different conclusion.",
+              disclosure: disclosure()
+            })
 
-      send_json(conn, 200, %{
-        case_ref: decision.case_ref,
-        deliberation: %{
-          panel_size: decision.panel_size,
-          majority: decision.majority,
-          minority: decision.minority,
-          outcome: decision.outcome,
-          processing_time_ms: decision.deliberation_time_ms
-        },
-        note: "This is the system's reasoning, not a binding ruling. A human beit din may reach a different conclusion.",
-        disclosure: disclosure()
-      })
+          {:error, "Halted" <> _ = reason} ->
+            send_error(conn, 422, "SANHEDRIN_HALTED", %{
+              issue: reason,
+              correction: "The case was refused at the gate before deliberation. Amend it and resubmit.",
+              resubmit: true
+            })
+
+          {:error, reason} ->
+            send_error(conn, 503, "SANHEDRIN_UNAVAILABLE", %{
+              issue: reason,
+              correction: "The Sanhedrin did not deliberate. Retry; if it recurs, the kohanim will find it in the log.",
+              resubmit: true
+            })
+        end
+      else
+        {:error, issue} ->
+          send_error(conn, 422, "KIYOR_VALIDATION_FAILED", %{
+            issue: issue,
+            correction: "'sides' is an optional list of {\"position\": string, \"evidence\": [string]}",
+            resubmit: true
+          })
+      end
     end
   end
 
+  # The optional sides: absent → []; a list of maps each with a string
+  # "position" and an optional list of string "evidence" → kept as given;
+  # anything else → refused at the kiyor.
+  defp sanhedrin_sides(nil), do: {:ok, []}
+
+  defp sanhedrin_sides(sides) when is_list(sides) do
+    if Enum.all?(sides, &side_ok?/1),
+      do: {:ok, sides},
+      else: {:error, "'sides' must be a list of {position, evidence[]} objects"}
+  end
+
+  defp sanhedrin_sides(_), do: {:error, "'sides' must be a list"}
+
+  defp side_ok?(%{"position" => p} = side) when is_binary(p) do
+    case Map.get(side, "evidence", []) do
+      ev when is_list(ev) -> Enum.all?(ev, &is_binary/1)
+      _ -> false
+    end
+  end
+
+  defp side_ok?(_), do: false
+
   # ============================================================
   # Internal — Health and Status
   # ============================================================