diff --git a/TODO.md b/TODO.md
index 677a25fc..f49cb45e 100644
--- a/TODO.md
+++ b/TODO.md
@@ -13,7 +13,6 @@
 - Exchange / Turn / Call セマンティクス整理 → [tickets/exchange-turn-call-semantics.md](tickets/exchange-turn-call-semantics.md)
 - llm-worker のエラー耐性
   - ストリーム途中失敗時の継続 → [tickets/llm-worker-stream-continuation.md](tickets/llm-worker-stream-continuation.md)
-- llm-worker: Anthropic projection で assistant ターン内ブロックを 1 message に束ねる → [tickets/anthropic-assistant-burst-bundling.md](tickets/anthropic-assistant-burst-bundling.md)
 - ネイティブ GUI クライアント MVP → [tickets/native-gui-mvp.md](tickets/native-gui-mvp.md)
 - E2E テストハーネス（`tests/e2e/`、opt-in） → [tickets/e2e-harness.md](tickets/e2e-harness.md)
 - TUI 拡充
diff --git a/crates/llm-worker/src/llm_client/scheme/anthropic/request.rs b/crates/llm-worker/src/llm_client/scheme/anthropic/request.rs
index 835840f7..62fac8d1 100644
--- a/crates/llm-worker/src/llm_client/scheme/anthropic/request.rs
+++ b/crates/llm-worker/src/llm_client/scheme/anthropic/request.rs
@@ -242,10 +242,13 @@ impl AnthropicScheme {
     /// - Tool calls are content parts within assistant messages
     /// - Tool results are content parts within user messages
     ///
-    /// Each non-`Message` item produces exactly one content part, so
-    /// "last part for the item" is always well-defined. For breakpoint
-    /// `Message` items the output is forced into the array form so a
-    /// marker has a part to attach to.
+    /// Assistant-side items are accumulated until a user/system message or
+    /// tool result boundary so one logical assistant burst becomes one
+    /// Anthropic assistant message content array. Pending parts carry their
+    /// origin item index; when flushed, the final part for each item records
+    /// the `(msg_idx, part_idx)` used by breakpoint attachment. User/system
+    /// `Message` items keep the single-text shorthand unless a breakpoint
+    /// needs a concrete part to live on.
     fn convert_items_to_messages(
         &self,
         items: &[Item],
@@ -261,19 +264,6 @@ impl AnthropicScheme {
         for (i, item) in items.iter().enumerate() {
             match item {
                 Item::Message { role, content, .. } => {
-                    flush_pending(
-                        &mut messages,
-                        &mut pending_assistant,
-                        "assistant",
-                        &mut locations,
-                    );
-                    flush_pending(&mut messages, &mut pending_user, "user", &mut locations);
-
-                    let anthropic_role = match role {
-                        Role::User | Role::System => "user",
-                        Role::Assistant => "assistant",
-                    };
-
                     let parts: Vec<AnthropicContentPart> = content
                         .iter()
                         .map(|p| match p {
@@ -284,27 +274,43 @@ impl AnthropicScheme {
                         })
                         .collect();
 
-                    let force_parts = breakpoints.contains(&i);
-                    let msg_idx = messages.len();
+                    match role {
+                        Role::Assistant => {
+                            flush_pending(&mut messages, &mut pending_user, "user", &mut locations);
+                            pending_assistant.extend(parts.into_iter().map(|part| (i, part)));
+                        }
+                        Role::User | Role::System => {
+                            flush_pending(
+                                &mut messages,
+                                &mut pending_assistant,
+                                "assistant",
+                                &mut locations,
+                            );
+                            flush_pending(&mut messages, &mut pending_user, "user", &mut locations);
 
-                    // Preserve the single-text shorthand unless a
-                    // breakpoint needs a concrete part to live on.
-                    if parts.len() == 1 && !force_parts {
-                        if let AnthropicContentPart::Text { text, .. } = &parts[0] {
+                            let force_parts = breakpoints.contains(&i);
+                            let msg_idx = messages.len();
+
+                            // Preserve the single-text shorthand unless a
+                            // breakpoint needs a concrete part to live on.
+                            if parts.len() == 1 && !force_parts {
+                                if let AnthropicContentPart::Text { text, .. } = &parts[0] {
+                                    messages.push(AnthropicMessage {
+                                        role: "user".to_string(),
+                                        content: AnthropicContent::Text(text.clone()),
+                                    });
+                                    continue;
+                                }
+                            }
+
+                            let last_part_idx = parts.len().saturating_sub(1);
                             messages.push(AnthropicMessage {
-                                role: anthropic_role.to_string(),
-                                content: AnthropicContent::Text(text.clone()),
+                                role: "user".to_string(),
+                                content: AnthropicContent::Parts(parts),
                             });
-                            continue;
+                            locations[i] = Some((msg_idx, last_part_idx));
                         }
                     }
-
-                    let last_part_idx = parts.len().saturating_sub(1);
-                    messages.push(AnthropicMessage {
-                        role: anthropic_role.to_string(),
-                        content: AnthropicContent::Parts(parts),
-                    });
-                    locations[i] = Some((msg_idx, last_part_idx));
                 }
 
                 Item::ToolCall {
@@ -626,6 +632,109 @@ mod tests {
         out
     }
 
+    #[test]
+    fn assistant_burst_bundles_reasoning_text_and_tool_call() {
+        let scheme = AnthropicScheme::new();
+        let request = Request::new()
+            .user("question?")
+            .item(Item::reasoning("thinking").with_signature("SIG-A"))
+            .item(Item::assistant_message("answer"))
+            .item(Item::tool_call("c1", "tool_a", r#"{"x":1}"#));
+
+        let req = scheme.build_request("claude-sonnet-4-20250514", &request, &cap_explicit());
+
+        assert_eq!(req.messages.len(), 2, "messages: {:?}", req.messages);
+        assert_eq!(req.messages[0].role, "user");
+        assert_eq!(req.messages[1].role, "assistant");
+        let AnthropicContent::Parts(parts) = &req.messages[1].content else {
+            panic!("assistant burst must be emitted as content parts");
+        };
+        assert_eq!(parts.len(), 3, "parts: {:?}", parts);
+        assert!(matches!(parts[0], AnthropicContentPart::Thinking { .. }));
+        assert!(matches!(parts[1], AnthropicContentPart::Text { .. }));
+        assert!(matches!(parts[2], AnthropicContentPart::ToolUse { .. }));
+    }
+
+    #[test]
+    fn tool_result_and_user_messages_bound_assistant_bursts() {
+        let scheme = AnthropicScheme::new();
+        let request = Request::new()
+            .user("question?")
+            .item(Item::reasoning("thinking").with_signature("SIG-A"))
+            .item(Item::assistant_message("answer"))
+            .item(Item::tool_call("c1", "tool_a", "{}"))
+            .item(Item::tool_result("c1", "result"))
+            .item(Item::assistant_message("final"))
+            .user("follow up");
+
+        let req = scheme.build_request("claude-sonnet-4-20250514", &request, &cap_explicit());
+
+        let roles: Vec<&str> = req.messages.iter().map(|msg| msg.role.as_str()).collect();
+        assert_eq!(
+            roles,
+            vec!["user", "assistant", "user", "assistant", "user"]
+        );
+
+        let AnthropicContent::Parts(first_assistant) = &req.messages[1].content else {
+            panic!("first assistant burst must be content parts");
+        };
+        assert_eq!(first_assistant.len(), 3);
+        assert!(matches!(
+            first_assistant[0],
+            AnthropicContentPart::Thinking { .. }
+        ));
+        assert!(matches!(
+            first_assistant[1],
+            AnthropicContentPart::Text { .. }
+        ));
+        assert!(matches!(
+            first_assistant[2],
+            AnthropicContentPart::ToolUse { .. }
+        ));
+
+        let AnthropicContent::Parts(tool_result) = &req.messages[2].content else {
+            panic!("tool result must be content parts");
+        };
+        assert_eq!(tool_result.len(), 1);
+        assert!(matches!(
+            tool_result[0],
+            AnthropicContentPart::ToolResult { .. }
+        ));
+
+        let AnthropicContent::Parts(second_assistant) = &req.messages[3].content else {
+            panic!("second assistant burst must be content parts");
+        };
+        assert_eq!(second_assistant.len(), 1);
+        assert!(matches!(
+            second_assistant[0],
+            AnthropicContentPart::Text { .. }
+        ));
+    }
+
+    #[test]
+    fn assistant_message_breakpoint_maps_to_text_part_inside_burst() {
+        let scheme = AnthropicScheme::new();
+        let mut request = Request::new().items(vec![
+            Item::user_message("question?"),
+            Item::reasoning("thinking").with_signature("SIG-A"),
+            Item::assistant_message("answer"),
+            Item::tool_call("c1", "tool_a", "{}"),
+            Item::user_message("next"),
+        ]);
+        request.cache_anchor = Some(2);
+
+        let req = scheme.build_request("claude-sonnet-4-20250514", &request, &cap_explicit());
+        let AnthropicContent::Parts(parts) = &req.messages[1].content else {
+            panic!("assistant burst must be content parts");
+        };
+
+        assert!(matches!(parts[0], AnthropicContentPart::Thinking { .. }));
+        assert!(matches!(parts[1], AnthropicContentPart::Text { .. }));
+        assert!(matches!(parts[2], AnthropicContentPart::ToolUse { .. }));
+        assert_eq!(part_cache_control(&parts[1]), Some(CacheControl::Ephemeral));
+        assert_eq!(part_cache_control(&parts[2]), Some(CacheControl::Ephemeral));
+    }
+
     /// Convenience: a turn that ends with one assistant text, one tool
     /// call/result pair, and a final assistant text. Produced at
     /// `history[head..]` indices shown alongside, so tests can reason
diff --git a/tickets/anthropic-assistant-burst-bundling.md b/tickets/anthropic-assistant-burst-bundling.md
deleted file mode 100644
index 4cf2c81a..00000000
--- a/tickets/anthropic-assistant-burst-bundling.md
+++ /dev/null
@@ -1,31 +0,0 @@
-# Anthropic projection: assistant ターン内ブロックを 1 message に束ねる
-
-## 背景
-
-`crates/llm-worker/src/llm_client/scheme/anthropic/request.rs` の `convert_items_to_messages` は、Worker が 1 ターンで生成する `[Reasoning, assistant_message, ToolCall]` の連列を、Anthropic wire 上で **複数の隣接した assistant message** に分割している。
-
-具体的には:
-- `Item::Reasoning` を `pending_assistant` に push
-- 次の `Item::Message { Role::Assistant }` が到来すると `pending_assistant` を flush し、自分自身は別 message として messages に直 push
-- 続く `Item::ToolCall` は再び `pending_assistant` に積まれ、turn 末で flush され 3 つ目の assistant message に
-
-結果として 1 turn が `assistant[Thinking] / assistant[text] / assistant[tool_use]` の 3 message に展開される。
-
-Anthropic Messages API は user/assistant の交互を要求し、同一論理 turn 内の thinking/text/tool_use は **1 つの assistant message の `content` 配列** に並べる仕様。新世代 Claude (Opus 4.5+/Sonnet 4.6+) で thinking signature を round-trip する際、隣接 assistant message に分かれていると signature の文脈が崩れて 400 になる懸念がある（reasoning-history-persist のレビュー指摘）。
-
-なお、本バグは reasoning-history-persist で導入されたものではなく、`assistant_message` + `tool_call` の組合せで以前から存在していた pre-existing な分割。Reasoning が同じ flush 経路を継承した形。
-
-## 要件
-
-- 同一論理ターンに属する `Item::Reasoning` / `Item::Message(Assistant)` / `Item::ToolCall` を、Anthropic wire 上の **1 つの assistant message の `content` 配列** に束ねる
-- 順序は arrival 順 (= history 順)。Anthropic 仕様の典型は thinking → text → tool_use
-- user / system role の `Item::Message` や `Item::ToolResult` を境界として assistant burst を区切る
-- 既存の breakpoint (cache_control) 計算が壊れないこと: 各 item のオリジン index → (msg_idx, part_idx) マッピングは flush_pending 経由で記録されているので、Item::Message(Assistant) も pending を経由するように揃えれば自然に追従する
-- Single-text 専用の `AnthropicContent::Text` shorthand は assistant burst 内 1 part のみのときに限定して維持するか、簡潔さのために常に `Parts` 形式に統一するかは実装時に判断
-- 既存テスト群（`completed_turn`, `single_text_message_uses_text_shorthand_without_breakpoint`, `breakpoint_on_tool_result_head` 等）の意図を逸脱しないよう更新
-
-## スコープ外
-
-- モデル世代別の thinking keep/strip デフォルト分岐（reasoning-history-persist のフォローアップ候補と同じ扱い）
-- `clear_thinking_20251015` context-edit
-- prune.rs の reasoning aware 化