diff --git a/codex-rs/app-server-protocol/schema/json/ClientRequest.json b/codex-rs/app-server-protocol/schema/json/ClientRequest.json
index 85e5940bc..6f5ebcdf0 100644
--- a/codex-rs/app-server-protocol/schema/json/ClientRequest.json
+++ b/codex-rs/app-server-protocol/schema/json/ClientRequest.json
@@ -1038,6 +1038,13 @@
       ],
       "type": "string"
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -1317,6 +1324,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/EventMsg.json b/codex-rs/app-server-protocol/schema/json/EventMsg.json
index 9e3cbb415..3e73bdc8b 100644
--- a/codex-rs/app-server-protocol/schema/json/EventMsg.json
+++ b/codex-rs/app-server-protocol/schema/json/EventMsg.json
@@ -3111,6 +3111,13 @@
         }
       ]
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -3596,6 +3603,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/ServerNotification.json b/codex-rs/app-server-protocol/schema/json/ServerNotification.json
index 6df9a010b..5d9e719d8 100644
--- a/codex-rs/app-server-protocol/schema/json/ServerNotification.json
+++ b/codex-rs/app-server-protocol/schema/json/ServerNotification.json
@@ -3890,6 +3890,13 @@
       ],
       "type": "string"
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -4636,6 +4643,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
index e92d46e7b..571079c7c 100644
--- a/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
+++ b/codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json
@@ -5839,6 +5839,13 @@
         }
       ]
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -6536,6 +6543,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
@@ -11731,6 +11748,13 @@
         ],
         "type": "string"
       },
+      "MessagePhase": {
+        "enum": [
+          "commentary",
+          "final_answer"
+        ],
+        "type": "string"
+      },
       "ModeKind": {
         "description": "Initial collaboration mode to use when the TUI starts.",
         "enum": [
@@ -12449,6 +12473,16 @@
                 ],
                 "writeOnly": true
               },
+              "phase": {
+                "anyOf": [
+                  {
+                    "$ref": "#/definitions/v2/MessagePhase"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
               "role": {
                 "type": "string"
               },
diff --git a/codex-rs/app-server-protocol/schema/json/v1/ForkConversationResponse.json b/codex-rs/app-server-protocol/schema/json/v1/ForkConversationResponse.json
index ae6e70522..ad251a461 100644
--- a/codex-rs/app-server-protocol/schema/json/v1/ForkConversationResponse.json
+++ b/codex-rs/app-server-protocol/schema/json/v1/ForkConversationResponse.json
@@ -3111,6 +3111,13 @@
         }
       ]
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -3596,6 +3603,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationParams.json b/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationParams.json
index e1cc626cc..41284b009 100644
--- a/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationParams.json
+++ b/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationParams.json
@@ -266,6 +266,13 @@
       ],
       "type": "string"
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "NewConversationParams": {
       "properties": {
         "approvalPolicy": {
@@ -437,6 +444,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationResponse.json b/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationResponse.json
index cdad2018c..abd5beb21 100644
--- a/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationResponse.json
+++ b/codex-rs/app-server-protocol/schema/json/v1/ResumeConversationResponse.json
@@ -3111,6 +3111,13 @@
         }
       ]
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -3596,6 +3603,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/v1/SessionConfiguredNotification.json b/codex-rs/app-server-protocol/schema/json/v1/SessionConfiguredNotification.json
index e6ed4d042..69c2c4b8b 100644
--- a/codex-rs/app-server-protocol/schema/json/v1/SessionConfiguredNotification.json
+++ b/codex-rs/app-server-protocol/schema/json/v1/SessionConfiguredNotification.json
@@ -3111,6 +3111,13 @@
         }
       ]
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ModeKind": {
       "description": "Initial collaboration mode to use when the TUI starts.",
       "enum": [
@@ -3596,6 +3603,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json b/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
index 47039df05..aecb8c2b5 100644
--- a/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
+++ b/codex-rs/app-server-protocol/schema/json/v2/RawResponseItemCompletedNotification.json
@@ -233,6 +233,13 @@
       ],
       "type": "string"
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "ReasoningItemContent": {
       "oneOf": [
         {
@@ -324,6 +331,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json b/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
index 3da1e3c74..52567cec8 100644
--- a/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
+++ b/codex-rs/app-server-protocol/schema/json/v2/ThreadResumeParams.json
@@ -242,6 +242,13 @@
       ],
       "type": "string"
     },
+    "MessagePhase": {
+      "enum": [
+        "commentary",
+        "final_answer"
+      ],
+      "type": "string"
+    },
     "Personality": {
       "enum": [
         "friendly",
@@ -340,6 +347,16 @@
               ],
               "writeOnly": true
             },
+            "phase": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/MessagePhase"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "role": {
               "type": "string"
             },
diff --git a/codex-rs/app-server-protocol/schema/typescript/MessagePhase.ts b/codex-rs/app-server-protocol/schema/typescript/MessagePhase.ts
new file mode 100644
index 000000000..d339c0fa8
--- /dev/null
+++ b/codex-rs/app-server-protocol/schema/typescript/MessagePhase.ts
@@ -0,0 +1,5 @@
+// GENERATED CODE! DO NOT MODIFY BY HAND!
+
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type MessagePhase = "commentary" | "final_answer";
diff --git a/codex-rs/app-server-protocol/schema/typescript/ResponseItem.ts b/codex-rs/app-server-protocol/schema/typescript/ResponseItem.ts
index d72002161..611c7fb22 100644
--- a/codex-rs/app-server-protocol/schema/typescript/ResponseItem.ts
+++ b/codex-rs/app-server-protocol/schema/typescript/ResponseItem.ts
@@ -6,11 +6,12 @@ import type { FunctionCallOutputPayload } from "./FunctionCallOutputPayload";
 import type { GhostCommit } from "./GhostCommit";
 import type { LocalShellAction } from "./LocalShellAction";
 import type { LocalShellStatus } from "./LocalShellStatus";
+import type { MessagePhase } from "./MessagePhase";
 import type { ReasoningItemContent } from "./ReasoningItemContent";
 import type { ReasoningItemReasoningSummary } from "./ReasoningItemReasoningSummary";
 import type { WebSearchAction } from "./WebSearchAction";
 
-export type ResponseItem = { "type": "message", role: string, content: Array<ContentItem>, end_turn?: boolean, } | { "type": "reasoning", summary: Array<ReasoningItemReasoningSummary>, content?: Array<ReasoningItemContent>, encrypted_content: string | null, } | { "type": "local_shell_call", 
+export type ResponseItem = { "type": "message", role: string, content: Array<ContentItem>, end_turn?: boolean, phase?: MessagePhase, } | { "type": "reasoning", summary: Array<ReasoningItemReasoningSummary>, content?: Array<ReasoningItemContent>, encrypted_content: string | null, } | { "type": "local_shell_call", 
 /**
  * Set when using the Responses API.
  */
diff --git a/codex-rs/app-server-protocol/schema/typescript/index.ts b/codex-rs/app-server-protocol/schema/typescript/index.ts
index 191f99386..b24e42a83 100644
--- a/codex-rs/app-server-protocol/schema/typescript/index.ts
+++ b/codex-rs/app-server-protocol/schema/typescript/index.ts
@@ -115,6 +115,7 @@ export type { McpStartupStatus } from "./McpStartupStatus";
 export type { McpStartupUpdateEvent } from "./McpStartupUpdateEvent";
 export type { McpToolCallBeginEvent } from "./McpToolCallBeginEvent";
 export type { McpToolCallEndEvent } from "./McpToolCallEndEvent";
+export type { MessagePhase } from "./MessagePhase";
 export type { ModeKind } from "./ModeKind";
 export type { NetworkAccess } from "./NetworkAccess";
 export type { NewConversationParams } from "./NewConversationParams";
diff --git a/codex-rs/app-server/tests/suite/list_resume.rs b/codex-rs/app-server/tests/suite/list_resume.rs
index f2b82c611..efa90ea35 100644
--- a/codex-rs/app-server/tests/suite/list_resume.rs
+++ b/codex-rs/app-server/tests/suite/list_resume.rs
@@ -308,6 +308,7 @@ async fn test_list_and_resume_conversations() -> Result<()> {
             text: fork_history_text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }];
     let resume_with_history_req_id = mcp
         .send_resume_conversation_request(ResumeConversationParams {
diff --git a/codex-rs/app-server/tests/suite/v2/compaction.rs b/codex-rs/app-server/tests/suite/v2/compaction.rs
index 66cf43bc0..eeedcb286 100644
--- a/codex-rs/app-server/tests/suite/v2/compaction.rs
+++ b/codex-rs/app-server/tests/suite/v2/compaction.rs
@@ -126,6 +126,7 @@ async fn auto_compaction_remote_emits_started_and_completed_items() -> Result<()
                 text: "REMOTE_COMPACT_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
diff --git a/codex-rs/app-server/tests/suite/v2/thread_resume.rs b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
index efa51573c..358fec351 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_resume.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
@@ -338,6 +338,7 @@ async fn thread_resume_supports_history_and_overrides() -> Result<()> {
             text: history_text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     // Resume with explicit history and override the model.
diff --git a/codex-rs/codex-api/src/endpoint/chat.rs b/codex-rs/codex-api/src/endpoint/chat.rs
index 2148a5ad9..b183597d6 100644
--- a/codex-rs/codex-api/src/endpoint/chat.rs
+++ b/codex-rs/codex-api/src/endpoint/chat.rs
@@ -194,6 +194,7 @@ impl Stream for AggregatedStream {
                                 text: std::mem::take(&mut this.cumulative),
                             }],
                             end_turn: None,
+                            phase: None,
                         };
                         this.pending
                             .push_back(ResponseEvent::OutputItemDone(aggregated_message));
diff --git a/codex-rs/codex-api/src/requests/chat.rs b/codex-rs/codex-api/src/requests/chat.rs
index 5c16a5fb5..60a591e5c 100644
--- a/codex-rs/codex-api/src/requests/chat.rs
+++ b/codex-rs/codex-api/src/requests/chat.rs
@@ -387,6 +387,7 @@ mod tests {
                 text: "hi".to_string(),
             }],
             end_turn: None,
+            phase: None,
         }];
         let req = ChatRequestBuilder::new("gpt-test", "inst", &prompt_input, &[])
             .conversation_id(Some("conv-1".into()))
@@ -414,6 +415,7 @@ mod tests {
                     text: "read these".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::FunctionCall {
                 id: None,
diff --git a/codex-rs/codex-api/src/requests/responses.rs b/codex-rs/codex-api/src/requests/responses.rs
index 73a413dd9..a0e90db06 100644
--- a/codex-rs/codex-api/src/requests/responses.rs
+++ b/codex-rs/codex-api/src/requests/responses.rs
@@ -224,12 +224,14 @@ mod tests {
                 role: "assistant".into(),
                 content: Vec::new(),
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: None,
                 role: "assistant".into(),
                 content: Vec::new(),
                 end_turn: None,
+                phase: None,
             },
         ];
 
diff --git a/codex-rs/codex-api/src/sse/chat.rs b/codex-rs/codex-api/src/sse/chat.rs
index a3effce2e..4b7884528 100644
--- a/codex-rs/codex-api/src/sse/chat.rs
+++ b/codex-rs/codex-api/src/sse/chat.rs
@@ -331,6 +331,7 @@ async fn append_assistant_text(
             role: "assistant".to_string(),
             content: vec![],
             end_turn: None,
+            phase: None,
         };
         *assistant_item = Some(item.clone());
         let _ = tx_event
diff --git a/codex-rs/codex-api/src/sse/responses.rs b/codex-rs/codex-api/src/sse/responses.rs
index b363671a1..2c9110472 100644
--- a/codex-rs/codex-api/src/sse/responses.rs
+++ b/codex-rs/codex-api/src/sse/responses.rs
@@ -429,6 +429,7 @@ mod tests {
     use super::*;
     use assert_matches::assert_matches;
     use bytes::Bytes;
+    use codex_protocol::models::MessagePhase;
     use codex_protocol::models::ResponseItem;
     use futures::stream;
     use pretty_assertions::assert_eq;
@@ -492,7 +493,8 @@ mod tests {
             "item": {
                 "type": "message",
                 "role": "assistant",
-                "content": [{"type": "output_text", "text": "Hello"}]
+                "content": [{"type": "output_text", "text": "Hello"}],
+                "phase": "commentary"
             }
         })
         .to_string();
@@ -523,8 +525,11 @@ mod tests {
 
         assert_matches!(
             &events[0],
-            Ok(ResponseEvent::OutputItemDone(ResponseItem::Message { role, .. }))
-                if role == "assistant"
+            Ok(ResponseEvent::OutputItemDone(ResponseItem::Message {
+                role,
+                phase: Some(MessagePhase::Commentary),
+                ..
+            })) if role == "assistant"
         );
 
         assert_matches!(
diff --git a/codex-rs/codex-api/tests/clients.rs b/codex-rs/codex-api/tests/clients.rs
index b71edf324..3040fb872 100644
--- a/codex-rs/codex-api/tests/clients.rs
+++ b/codex-rs/codex-api/tests/clients.rs
@@ -309,6 +309,7 @@ async fn streaming_client_retries_on_transport_error() -> Result<()> {
                 text: "hi".to_string(),
             }],
             end_turn: None,
+            phase: None,
         }],
         tools: Vec::<Value>::new(),
         parallel_tool_calls: false,
diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index 6cc389b53..7c9909355 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -1834,6 +1834,7 @@ impl Session {
                 text: format!("Warning: {}", message.into()),
             }],
             end_turn: None,
+            phase: None,
         };
 
         self.record_conversation_items(ctx, &[item]).await;
@@ -4542,6 +4543,7 @@ mod tests {
                 text: text.to_string(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 
@@ -4823,6 +4825,7 @@ mod tests {
                     text: "turn 1 user".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -4831,6 +4834,7 @@ mod tests {
                     text: "turn 1 assistant".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
         ];
         sess.record_into_history(&turn_1, tc.as_ref()).await;
@@ -4843,6 +4847,7 @@ mod tests {
                     text: "turn 2 user".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -4851,6 +4856,7 @@ mod tests {
                     text: "turn 2 assistant".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
         ];
         sess.record_into_history(&turn_2, tc.as_ref()).await;
@@ -4883,6 +4889,7 @@ mod tests {
                 text: "turn 1 user".to_string(),
             }],
             end_turn: None,
+            phase: None,
         }];
         sess.record_into_history(&turn_1, tc.as_ref()).await;
 
@@ -5832,6 +5839,7 @@ mod tests {
                 text: "first user".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&user1), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(user1.clone()));
@@ -5843,6 +5851,7 @@ mod tests {
                 text: "assistant reply one".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&assistant1), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(assistant1.clone()));
@@ -5868,6 +5877,7 @@ mod tests {
                 text: "second user".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&user2), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(user2.clone()));
@@ -5879,6 +5889,7 @@ mod tests {
                 text: "assistant reply two".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&assistant2), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(assistant2.clone()));
@@ -5904,6 +5915,7 @@ mod tests {
                 text: "third user".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&user3), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(user3));
@@ -5915,6 +5927,7 @@ mod tests {
                 text: "assistant reply three".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         live_history.record_items(std::iter::once(&assistant3), turn_context.truncation_policy);
         rollout_items.push(RolloutItem::ResponseItem(assistant3));
diff --git a/codex-rs/core/src/compact.rs b/codex-rs/core/src/compact.rs
index b44d43f42..ee94e4994 100644
--- a/codex-rs/core/src/compact.rs
+++ b/codex-rs/core/src/compact.rs
@@ -311,6 +311,7 @@ fn build_compacted_history_with_limit(
                 text: message.clone(),
             }],
             end_turn: None,
+            phase: None,
         });
     }
 
@@ -325,6 +326,7 @@ fn build_compacted_history_with_limit(
         role: "user".to_string(),
         content: vec![ContentItem::InputText { text: summary_text }],
         end_turn: None,
+        phase: None,
     });
 
     history
@@ -416,6 +418,7 @@ mod tests {
                     text: "ignored".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: Some("user".to_string()),
@@ -424,6 +427,7 @@ mod tests {
                     text: "first".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Other,
         ];
@@ -444,6 +448,7 @@ mod tests {
                         .to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -452,6 +457,7 @@ mod tests {
                     text: "<ENVIRONMENT_CONTEXT>cwd=/tmp</ENVIRONMENT_CONTEXT>".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -460,6 +466,7 @@ mod tests {
                     text: "real user message".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
         ];
 
@@ -545,6 +552,7 @@ mod tests {
                     text: marker.clone(),
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -553,6 +561,7 @@ mod tests {
                     text: "real user message".to_string(),
                 }],
                 end_turn: None,
+                phase: None,
             },
         ];
 
diff --git a/codex-rs/core/src/context_manager/history_tests.rs b/codex-rs/core/src/context_manager/history_tests.rs
index 50ee98e5b..d31f731a9 100644
--- a/codex-rs/core/src/context_manager/history_tests.rs
+++ b/codex-rs/core/src/context_manager/history_tests.rs
@@ -24,6 +24,7 @@ fn assistant_msg(text: &str) -> ResponseItem {
             text: text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
@@ -43,6 +44,7 @@ fn user_msg(text: &str) -> ResponseItem {
             text: text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
@@ -54,6 +56,7 @@ fn user_input_text_msg(text: &str) -> ResponseItem {
             text: text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
@@ -97,6 +100,7 @@ fn filters_non_api_messages() {
             text: "ignored".to_string(),
         }],
         end_turn: None,
+        phase: None,
     };
     let reasoning = reasoning_msg("thinking...");
     h.record_items([&system, &reasoning, &ResponseItem::Other], policy);
@@ -127,6 +131,7 @@ fn filters_non_api_messages() {
                     text: "hi".to_string()
                 }],
                 end_turn: None,
+                phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -135,6 +140,7 @@ fn filters_non_api_messages() {
                     text: "hello".to_string()
                 }],
                 end_turn: None,
+                phase: None,
             }
         ]
     );
@@ -262,6 +268,7 @@ fn replace_last_turn_images_does_not_touch_user_images() {
             image_url: "data:image/png;base64,AAA".to_string(),
         }],
         end_turn: None,
+        phase: None,
     }];
     let mut history = create_history_with_items(items.clone());
 
diff --git a/codex-rs/core/src/environment_context.rs b/codex-rs/core/src/environment_context.rs
index 87692a2f0..9f5455a69 100644
--- a/codex-rs/core/src/environment_context.rs
+++ b/codex-rs/core/src/environment_context.rs
@@ -81,6 +81,7 @@ impl From<EnvironmentContext> for ResponseItem {
                 text: ec.serialize_to_xml(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 }
diff --git a/codex-rs/core/src/event_mapping.rs b/codex-rs/core/src/event_mapping.rs
index 35804fd47..2ad19d3df 100644
--- a/codex-rs/core/src/event_mapping.rs
+++ b/codex-rs/core/src/event_mapping.rs
@@ -177,6 +177,7 @@ mod tests {
                 },
             ],
             end_turn: None,
+            phase: None,
         };
 
         let turn_item = parse_turn_item(&item).expect("expected user message turn item");
@@ -219,6 +220,7 @@ mod tests {
                 },
             ],
             end_turn: None,
+            phase: None,
         };
 
         let turn_item = parse_turn_item(&item).expect("expected user message turn item");
@@ -260,6 +262,7 @@ mod tests {
                 },
             ],
             end_turn: None,
+            phase: None,
         };
 
         let turn_item = parse_turn_item(&item).expect("expected user message turn item");
@@ -289,6 +292,7 @@ mod tests {
                     text: "<user_instructions>test_text</user_instructions>".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -297,6 +301,7 @@ mod tests {
                     text: "<environment_context>test_text</environment_context>".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -305,6 +310,7 @@ mod tests {
                     text: "# AGENTS.md instructions for test_directory\n\n<INSTRUCTIONS>\ntest_text\n</INSTRUCTIONS>".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -314,6 +320,7 @@ mod tests {
                         .to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
             ResponseItem::Message {
                 id: None,
@@ -322,6 +329,7 @@ mod tests {
                     text: "<user_shell_command>echo 42</user_shell_command>".to_string(),
                 }],
                 end_turn: None,
+            phase: None,
             },
         ];
 
@@ -340,6 +348,7 @@ mod tests {
                 text: "Hello from Codex".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
 
         let turn_item = parse_turn_item(&item).expect("expected agent message turn item");
diff --git a/codex-rs/core/src/instructions/user_instructions.rs b/codex-rs/core/src/instructions/user_instructions.rs
index 611bf4cbf..525834847 100644
--- a/codex-rs/core/src/instructions/user_instructions.rs
+++ b/codex-rs/core/src/instructions/user_instructions.rs
@@ -39,6 +39,7 @@ impl From<UserInstructions> for ResponseItem {
                 ),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 }
@@ -73,6 +74,7 @@ impl From<SkillInstructions> for ResponseItem {
                 ),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 }
diff --git a/codex-rs/core/src/rollout/tests.rs b/codex-rs/core/src/rollout/tests.rs
index cdf16291d..ee750b126 100644
--- a/codex-rs/core/src/rollout/tests.rs
+++ b/codex-rs/core/src/rollout/tests.rs
@@ -902,6 +902,7 @@ async fn test_updated_at_uses_file_mtime() -> Result<()> {
                     text: format!("reply-{idx}"),
                 }],
                 end_turn: None,
+                phase: None,
             }),
         };
         writeln!(file, "{}", serde_json::to_string(&response_line)?)?;
diff --git a/codex-rs/core/src/rollout/truncation.rs b/codex-rs/core/src/rollout/truncation.rs
index e6a84628f..c50eacc48 100644
--- a/codex-rs/core/src/rollout/truncation.rs
+++ b/codex-rs/core/src/rollout/truncation.rs
@@ -86,6 +86,7 @@ mod tests {
                 text: text.to_string(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 
@@ -97,6 +98,7 @@ mod tests {
                 text: text.to_string(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 
diff --git a/codex-rs/core/src/tasks/mod.rs b/codex-rs/core/src/tasks/mod.rs
index a487041eb..d5d6f6058 100644
--- a/codex-rs/core/src/tasks/mod.rs
+++ b/codex-rs/core/src/tasks/mod.rs
@@ -265,6 +265,7 @@ impl Session {
                     ),
                 }],
                 end_turn: None,
+                phase: None,
             };
             self.record_into_history(std::slice::from_ref(&marker), task.turn_context.as_ref())
                 .await;
diff --git a/codex-rs/core/src/tasks/review.rs b/codex-rs/core/src/tasks/review.rs
index d156d3e0d..cfc554f85 100644
--- a/codex-rs/core/src/tasks/review.rs
+++ b/codex-rs/core/src/tasks/review.rs
@@ -222,6 +222,7 @@ pub(crate) async fn exit_review_mode(
                 role: "user".to_string(),
                 content: vec![ContentItem::InputText { text: user_message }],
                 end_turn: None,
+                phase: None,
             }],
         )
         .await;
@@ -241,6 +242,7 @@ pub(crate) async fn exit_review_mode(
                     text: assistant_message,
                 }],
                 end_turn: None,
+                phase: None,
             },
         )
         .await;
diff --git a/codex-rs/core/src/thread_manager.rs b/codex-rs/core/src/thread_manager.rs
index 9b633ded3..37bd0efab 100644
--- a/codex-rs/core/src/thread_manager.rs
+++ b/codex-rs/core/src/thread_manager.rs
@@ -462,6 +462,7 @@ mod tests {
                 text: text.to_string(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
     fn assistant_msg(text: &str) -> ResponseItem {
@@ -472,6 +473,7 @@ mod tests {
                 text: text.to_string(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 
diff --git a/codex-rs/core/src/user_shell_command.rs b/codex-rs/core/src/user_shell_command.rs
index 566f39958..80128df00 100644
--- a/codex-rs/core/src/user_shell_command.rs
+++ b/codex-rs/core/src/user_shell_command.rs
@@ -63,6 +63,7 @@ pub fn user_shell_command_record_item(
             text: format_user_shell_command_record(command, exec_output, turn_context),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
diff --git a/codex-rs/core/tests/chat_completions_payload.rs b/codex-rs/core/tests/chat_completions_payload.rs
index 5406b44ad..277209144 100644
--- a/codex-rs/core/tests/chat_completions_payload.rs
+++ b/codex-rs/core/tests/chat_completions_payload.rs
@@ -139,6 +139,7 @@ fn user_message(text: &str) -> ResponseItem {
             text: text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
@@ -150,6 +151,7 @@ fn assistant_message(text: &str) -> ResponseItem {
             text: text.to_string(),
         }],
         end_turn: None,
+        phase: None,
     }
 }
 
diff --git a/codex-rs/core/tests/chat_completions_sse.rs b/codex-rs/core/tests/chat_completions_sse.rs
index 836023775..98e2fd9f0 100644
--- a/codex-rs/core/tests/chat_completions_sse.rs
+++ b/codex-rs/core/tests/chat_completions_sse.rs
@@ -113,6 +113,7 @@ async fn run_stream_with_bytes(sse_body: &[u8]) -> Vec<ResponseEvent> {
             text: "hello".to_string(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     let mut stream = match client.stream(&prompt).await {
diff --git a/codex-rs/core/tests/responses_headers.rs b/codex-rs/core/tests/responses_headers.rs
index a40c92d02..86e511c47 100644
--- a/codex-rs/core/tests/responses_headers.rs
+++ b/codex-rs/core/tests/responses_headers.rs
@@ -110,6 +110,7 @@ async fn responses_stream_includes_subagent_header_on_review() {
             text: "hello".into(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     let mut stream = client_session.stream(&prompt).await.expect("stream failed");
@@ -209,6 +210,7 @@ async fn responses_stream_includes_subagent_header_on_other() {
             text: "hello".into(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     let mut stream = client_session.stream(&prompt).await.expect("stream failed");
@@ -366,6 +368,7 @@ async fn responses_respects_model_info_overrides_from_config() {
             text: "hello".into(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     let mut stream = client.stream(&prompt).await.expect("stream failed");
@@ -473,6 +476,7 @@ async fn responses_stream_includes_turn_metadata_header_for_git_workspace_e2e()
             text: "hello".into(),
         }],
         end_turn: None,
+        phase: None,
     }];
 
     let first_request = responses::mount_sse_once(&server, response_body.clone()).await;
diff --git a/codex-rs/core/tests/suite/client.rs b/codex-rs/core/tests/suite/client.rs
index d79ef22b5..d0f2ba1ae 100644
--- a/codex-rs/core/tests/suite/client.rs
+++ b/codex-rs/core/tests/suite/client.rs
@@ -29,6 +29,7 @@ use codex_protocol::config_types::ReasoningSummary;
 use codex_protocol::config_types::Settings;
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::models::FunctionCallOutputPayload;
+use codex_protocol::models::MessagePhase;
 use codex_protocol::models::ReasoningItemContent;
 use codex_protocol::models::ReasoningItemReasoningSummary;
 use codex_protocol::models::WebSearchAction;
@@ -197,6 +198,7 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
             text: "resumed user message".to_string(),
         }],
         end_turn: None,
+        phase: None,
     };
     let prior_user_json = serde_json::to_value(&prior_user).unwrap();
     writeln!(
@@ -218,6 +220,7 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
             text: "resumed system instruction".to_string(),
         }],
         end_turn: None,
+        phase: None,
     };
     let prior_system_json = serde_json::to_value(&prior_system).unwrap();
     writeln!(
@@ -239,6 +242,7 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
             text: "resumed assistant message".to_string(),
         }],
         end_turn: None,
+        phase: Some(MessagePhase::Commentary),
     };
     let prior_item_json = serde_json::to_value(&prior_item).unwrap();
     writeln!(
@@ -318,6 +322,25 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
         .iter()
         .position(|(role, text)| role == "assistant" && text == "resumed assistant message")
         .expect("prior assistant message");
+    let prior_assistant = input
+        .iter()
+        .find(|item| {
+            item.get("role").and_then(|role| role.as_str()) == Some("assistant")
+                && item
+                    .get("content")
+                    .and_then(|content| content.as_array())
+                    .and_then(|content| content.first())
+                    .and_then(|entry| entry.get("text"))
+                    .and_then(|text| text.as_str())
+                    == Some("resumed assistant message")
+        })
+        .expect("resumed assistant message request item");
+    assert_eq!(
+        prior_assistant
+            .get("phase")
+            .and_then(|phase| phase.as_str()),
+        Some("commentary")
+    );
     let pos_permissions = messages
         .iter()
         .position(|(role, text)| role == "developer" && text.contains("<permissions instructions>"))
@@ -1210,6 +1233,7 @@ async fn azure_responses_request_includes_store_and_reasoning_ids() {
             text: "message".into(),
         }],
         end_turn: None,
+        phase: None,
     });
     prompt.input.push(ResponseItem::WebSearchCall {
         id: Some("web-search-id".into()),
diff --git a/codex-rs/core/tests/suite/client_websockets.rs b/codex-rs/core/tests/suite/client_websockets.rs
index 1acc3756d..51c94edd7 100644
--- a/codex-rs/core/tests/suite/client_websockets.rs
+++ b/codex-rs/core/tests/suite/client_websockets.rs
@@ -211,6 +211,7 @@ fn message_item(text: &str) -> ResponseItem {
         role: "user".into(),
         content: vec![ContentItem::InputText { text: text.into() }],
         end_turn: None,
+        phase: None,
     }
 }
 
diff --git a/codex-rs/core/tests/suite/compact.rs b/codex-rs/core/tests/suite/compact.rs
index fa07bf7f9..ea9d2f92f 100644
--- a/codex-rs/core/tests/suite/compact.rs
+++ b/codex-rs/core/tests/suite/compact.rs
@@ -1452,6 +1452,7 @@ async fn auto_compact_runs_after_resume_when_token_usage_is_over_limit() {
                 text: remote_summary.to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         codex_protocol::models::ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -2275,6 +2276,7 @@ async fn auto_compact_counts_encrypted_reasoning_before_last_user() {
                 text: "REMOTE_COMPACT_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         codex_protocol::models::ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -2395,6 +2397,7 @@ async fn auto_compact_runs_when_reasoning_header_clears_between_turns() {
                 text: "REMOTE_COMPACT_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         codex_protocol::models::ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
diff --git a/codex-rs/core/tests/suite/compact_remote.rs b/codex-rs/core/tests/suite/compact_remote.rs
index 563aff782..e5446f4a3 100644
--- a/codex-rs/core/tests/suite/compact_remote.rs
+++ b/codex-rs/core/tests/suite/compact_remote.rs
@@ -62,6 +62,7 @@ async fn remote_compact_replaces_history_for_followups() -> Result<()> {
                 text: "REMOTE_COMPACTED_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -184,6 +185,7 @@ async fn remote_compact_runs_automatically() -> Result<()> {
                 text: "REMOTE_COMPACTED_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -251,6 +253,7 @@ async fn remote_manual_compact_emits_context_compaction_items() -> Result<()> {
                 text: "REMOTE_COMPACTED_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -352,6 +355,7 @@ async fn remote_compact_persists_replacement_history_in_rollout() -> Result<()>
                 text: "COMPACTED_USER_SUMMARY".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
         ResponseItem::Compaction {
             encrypted_content: "ENCRYPTED_COMPACTION_SUMMARY".to_string(),
@@ -363,6 +367,7 @@ async fn remote_compact_persists_replacement_history_in_rollout() -> Result<()>
                 text: "COMPACTED_ASSISTANT_NOTE".to_string(),
             }],
             end_turn: None,
+            phase: None,
         },
     ];
     let compact_mock = responses::mount_compact_json_once(
diff --git a/codex-rs/core/tests/suite/image_rollout.rs b/codex-rs/core/tests/suite/image_rollout.rs
index 6aebe6630..691531e04 100644
--- a/codex-rs/core/tests/suite/image_rollout.rs
+++ b/codex-rs/core/tests/suite/image_rollout.rs
@@ -158,6 +158,7 @@ async fn copy_paste_local_image_persists_rollout_request_shape() -> anyhow::Resu
             },
         ],
         end_turn: None,
+        phase: None,
     };
 
     assert_eq!(actual, expected);
@@ -239,6 +240,7 @@ async fn drag_drop_image_persists_rollout_request_shape() -> anyhow::Result<()>
             },
         ],
         end_turn: None,
+        phase: None,
     };
 
     assert_eq!(actual, expected);
diff --git a/codex-rs/core/tests/suite/review.rs b/codex-rs/core/tests/suite/review.rs
index cfc4a8048..1c9c3adf7 100644
--- a/codex-rs/core/tests/suite/review.rs
+++ b/codex-rs/core/tests/suite/review.rs
@@ -530,6 +530,7 @@ async fn review_input_isolated_from_parent_history() {
                 text: "parent: earlier user message".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         let user_json = serde_json::to_value(&user).unwrap();
         let user_line = serde_json::json!({
@@ -549,6 +550,7 @@ async fn review_input_isolated_from_parent_history() {
                 text: "parent: assistant reply".to_string(),
             }],
             end_turn: None,
+            phase: None,
         };
         let assistant_json = serde_json::to_value(&assistant).unwrap();
         let assistant_line = serde_json::json!({
diff --git a/codex-rs/protocol/src/models.rs b/codex-rs/protocol/src/models.rs
index 07c8856fe..74cc9a53f 100644
--- a/codex-rs/protocol/src/models.rs
+++ b/codex-rs/protocol/src/models.rs
@@ -72,6 +72,13 @@ pub enum ContentItem {
     OutputText { text: String },
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "snake_case")]
+pub enum MessagePhase {
+    Commentary,
+    FinalAnswer,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, JsonSchema, TS)]
 #[serde(tag = "type", rename_all = "snake_case")]
 pub enum ResponseItem {
@@ -85,6 +92,11 @@ pub enum ResponseItem {
         #[serde(default, skip_serializing_if = "Option::is_none")]
         #[ts(optional)]
         end_turn: Option<bool>,
+        // Optional output-message phase (for example: "commentary", "final_answer").
+        // Do not use directly; availability can vary by provider and model.
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        #[ts(optional)]
+        phase: Option<MessagePhase>,
     },
     Reasoning {
         #[serde(default, skip_serializing)]
@@ -439,6 +451,7 @@ impl From<DeveloperInstructions> for ResponseItem {
                 text: di.into_text(),
             }],
             end_turn: None,
+            phase: None,
         }
     }
 }
@@ -596,6 +609,7 @@ impl From<ResponseInputItem> for ResponseItem {
                 content,
                 id: None,
                 end_turn: None,
+                phase: None,
             },
             ResponseInputItem::FunctionCallOutput { call_id, output } => {
                 Self::FunctionCallOutput { call_id, output }
diff --git a/codex-rs/protocol/src/protocol.rs b/codex-rs/protocol/src/protocol.rs
index 71a7973c6..bf193cca9 100644
--- a/codex-rs/protocol/src/protocol.rs
+++ b/codex-rs/protocol/src/protocol.rs
@@ -1691,6 +1691,7 @@ impl From<CompactedItem> for ResponseItem {
                 text: value.message,
             }],
             end_turn: None,
+            phase: None,
         }
     }
 }
diff --git a/codex-rs/state/src/extract.rs b/codex-rs/state/src/extract.rs
index 8d327a4d1..ad4011808 100644
--- a/codex-rs/state/src/extract.rs
+++ b/codex-rs/state/src/extract.rs
@@ -151,6 +151,7 @@ mod tests {
                 },
             ],
             end_turn: None,
+            phase: None,
         };
         let actual = extract_user_message_text(&item);
         assert_eq!(actual.as_deref(), Some("actual question"));