fix(rectification): preserve assistant turns in dossier

docs/BUG_HISTORY.md

@@ -3005,3 +3005,18 @@
 - 防复发：服务器确认路径与额外对话轮次必须分开建模；任何 pending 状态不得隐式参与正式候选评分。
 - 相关记录：BUG-170、BUG-174
 - 修复版本：本次提交（staging 精确 SHA 以发布记录为准）
+
+## BUG-176 | V9 普通 Turn 的 Agent 回复在刷新后消失
+
+- 状态：resolved（本地候选）
+- 首次发现：2026-08-12
+- 最近更新：2026-08-12
+- 影响面：V9 生时校正历史消息、持久化 Activity 与 Agent 下一轮上下文。
+- 用户现象：事件提交后当轮可以看到 Agent 回复和 Activity，但刷新或重新进入 Case 后只剩用户事件；opening Agent 消息仍可显示。
+- 触发条件：一条物理 `agentic_rectification_turns` 记录同时保存非空 `user_message` 与 `assistant_message`。
+- 根因：`get_agentic_rectification_case_dossier()` 把每条物理 Turn 只投影成一条逻辑消息，并用 `coalesce(user_message, assistant_message)` 优先返回用户文本，导致同一行已持久化的 Agent 回复和 receipt 关联在恢复 API 中丢失。
+- 修复：新增向前业务迁移，将每条物理 Turn 通过 lateral values 展开为按 user、assistant 排序的最多两条逻辑消息；保留同一真实 Turn ID，使 assistant 消息继续读取对应 Activity receipt。
+- 验证：迁移契约测试锁定双消息展开、空消息过滤、顺序、迁移唯一性和禁止复制到 identity migration tree；staging 需继续验证 Case GET、页面刷新、下一轮上下文及计费不变量。
+- 防复发：持久化行与对话消息不是一对一时，恢复投影必须显式展开全部逻辑消息，不得用 `coalesce` 静默舍弃其中一侧。
+- 相关记录：BUG-173、BUG-174、BUG-175
+- 修复版本：本次提交（staging 精确 SHA 以发布记录为准）

frontend/supabase/migrations/20260813030000_rectification_turn_message_projection.sql

@@ -0,0 +1,133 @@
+-- Preserve both logical messages stored by a completed rectification turn.
+-- A normal turn stores user_message and assistant_message on the same physical
+-- row; the dossier must expose both in conversational order. Business schema
+-- only: do not copy this migration into frontend/db/migrations.
+
+begin;
+
+create or replace function public.get_agentic_rectification_case_dossier(
+  p_user_id uuid,
+  p_case_id uuid
+)
+returns jsonb
+language plpgsql
+security definer
+set search_path = ''
+as $$
+declare
+  v_case public.agentic_rectification_cases%rowtype;
+  v_turns jsonb;
+  v_evidence jsonb;
+  v_result public.agentic_rectification_results%rowtype;
+  v_evidence_count bigint;
+  v_turn_count bigint;
+begin
+  if p_user_id is null or p_case_id is null then
+    raise exception 'agentic_rectification_invalid_input' using errcode = 'P0001';
+  end if;
+  select * into v_case
+  from public.agentic_rectification_cases
+  where id = p_case_id and user_id = p_user_id;
+  if not found then
+    raise exception 'agentic_rectification_case_not_found' using errcode = 'P0001';
+  end if;
+
+  select coalesce(jsonb_agg(
+    jsonb_build_object(
+      'id', t.id,
+      'role', message.role,
+      'text', message.text,
+      'status', t.status,
+      'created_at', t.created_at,
+      'completed_at', t.completed_at
+    ) order by t.created_at, message.ordinal
+  ), '[]'::jsonb) into v_turns
+  from public.agentic_rectification_turns t
+  cross join lateral (
+    values
+      (1, 'user'::text, t.user_message),
+      (2, 'assistant'::text, t.assistant_message)
+  ) as message(ordinal, role, text)
+  where t.case_id = v_case.id
+    and message.text is not null;
+
+  select coalesce(jsonb_agg(
+    jsonb_build_object(
+      'id', e.id,
+      'source_turn_id', e.source_turn_id,
+      'subject', e.subject,
+      'event_kind', e.event_kind,
+      'domain', e.domain,
+      'occurred_from', e.occurred_from,
+      'occurred_to', e.occurred_to,
+      'date_precision', e.date_precision,
+      'summary', e.summary,
+      'status', e.status,
+      'supersedes_evidence_id', e.supersedes_evidence_id,
+      'created_at', e.created_at
+    ) order by e.created_at
+  ), '[]'::jsonb) into v_evidence
+  from public.agentic_rectification_evidence e
+  where e.case_id = v_case.id;
+
+  select count(*) into v_evidence_count
+  from public.agentic_rectification_evidence
+  where case_id = v_case.id;
+  select count(*) into v_turn_count
+  from public.agentic_rectification_turns
+  where case_id = v_case.id;
+
+  select * into v_result
+  from public.agentic_rectification_results
+  where case_id = v_case.id
+    and invalidated_at is null
+  order by created_at desc
+  limit 1;
+
+  return jsonb_build_object(
+    'case', jsonb_build_object(
+      'case_id', v_case.id,
+      'session_id', v_case.session_id,
+      'status', v_case.status,
+      'skill_name', v_case.skill_name,
+      'skill_version', v_case.skill_version,
+      'candidate_range', v_case.candidate_range,
+      'accepted_time', v_case.accepted_time,
+      'confirmed_time', v_case.confirmed_time,
+      'completed_at', v_case.completed_at,
+      'closed_reason', v_case.closed_reason,
+      'last_activity_at', v_case.last_activity_at,
+      'evidence_count', v_evidence_count,
+      'turn_count', v_turn_count
+    ),
+    'turns', v_turns,
+    'evidence', v_evidence,
+    'latest_result', case
+      when v_result.id is null then null
+      else jsonb_build_object(
+        'result_id', v_result.id,
+        'candidates', v_result.candidates,
+        'overall_confidence', v_result.overall_confidence,
+        'selection_allowed', v_result.selection_allowed,
+        'confirmation_allowed', v_result.confirmation_allowed,
+        'representative_time', v_result.representative_time,
+        'selected_time', v_result.selected_time,
+        'selection_kind', v_result.selection_kind,
+        'evidence_ledger_fingerprint', v_result.evidence_ledger_fingerprint,
+        'candidate_range_fingerprint', v_result.candidate_range_fingerprint,
+        'skill_version', v_result.skill_version,
+        'algorithm_version', v_result.algorithm_version,
+        'created_at', v_result.created_at,
+        'invalidated_at', v_result.invalidated_at
+      )
+    end
+  );
+end;
+$$;
+
+revoke all on function public.get_agentic_rectification_case_dossier(uuid, uuid)
+  from public, anon, authenticated;
+grant execute on function public.get_agentic_rectification_case_dossier(uuid, uuid)
+  to service_role;
+
+commit;

frontend/tests/rectification-v9-migration.test.ts

@@ -399,3 +399,53 @@ test("birth-context activity migration stays out of the identity migration tree"
     "business migration must not be copied into frontend/db/migrations (BUG-127/BUG-144)",
   );
 });
+
+// ---------------------------------------------------------------------------
+// 20260813030000_rectification_turn_message_projection.sql
+// ---------------------------------------------------------------------------
+
+const turnMessageProjectionMigration = readFileSync(
+  new URL(
+    "../supabase/migrations/20260813030000_rectification_turn_message_projection.sql",
+    import.meta.url,
+  ),
+  "utf8",
+);
+
+const turnMessageProjectionMigrationCopy = fileURLToPath(
+  new URL(
+    "../db/migrations/20260813030000_rectification_turn_message_projection.sql",
+    import.meta.url,
+  ),
+);
+
+test("rectification turn projection migration follows the V9 activity migration", () => {
+  assert.ok(
+    "20260813030000_rectification_turn_message_projection.sql" >
+      "20260813020000_rectification_birth_context_activity.sql",
+  );
+  assert.match(turnMessageProjectionMigration, /^-- Preserve both logical messages[\s\S]*\nbegin;[\s\S]*^commit;$/m);
+});
+
+test("rectification dossier expands each physical turn into user and assistant messages", () => {
+  assert.match(
+    turnMessageProjectionMigration,
+    /cross join lateral \(\s*values\s*\(1, 'user'::text, t\.user_message\),\s*\(2, 'assistant'::text, t\.assistant_message\)\s*\) as message\(ordinal, role, text\)/,
+  );
+  assert.match(turnMessageProjectionMigration, /'role', message\.role/);
+  assert.match(turnMessageProjectionMigration, /'text', message\.text/);
+  assert.match(turnMessageProjectionMigration, /order by t\.created_at, message\.ordinal/);
+  assert.match(turnMessageProjectionMigration, /and message\.text is not null/);
+  assert.doesNotMatch(
+    turnMessageProjectionMigration,
+    /coalesce\(t\.user_message, t\.assistant_message\)/,
+  );
+});
+
+test("rectification turn projection migration stays out of the identity migration tree", () => {
+  assert.equal(
+    existsSync(turnMessageProjectionMigrationCopy),
+    false,
+    "business migration must not be copied into frontend/db/migrations (BUG-127/BUG-144)",
+  );
+});