Add app-server APIs for stored thread attachments (#44564)

## What changed

- Add `thread/attachment/add`, `thread/attachment/list`, and `thread/attachment/remove` to manage durable resource references without loading the owning thread or changing conversation history.
- Identify attachments by thread, `attachmentType`, and `identityKey`. Repeated adds return the existing attachment; repeated removals succeed without emitting another update. Listing supports cursor pagination.
- Broadcast `thread/attachment/updated` after creation or deletion, after responding to the requester. Serialize attachment mutations with thread lifecycle operations and reject stores that do not support attachments.
- Update protocol schemas, TypeScript and Python bindings, documentation, and TUI notification handling so attachment updates do not add untracked threads to the agent picker.

## Testing

Add coverage for unloaded threads, pagination, idempotent addition and removal, reattachment, invalid inputs, unsupported stores, response-before-notification ordering across clients, and TUI notification routing.

GitOrigin-RevId: 0d29cf903afd4e931a70a9cf96300475213b34aa

sdk/python/src/openai_codex/generated/notification_registry.py

@@ -54,6 +54,7 @@ from .v2_all import SkillsChangedNotification
 from .v2_all import StrictReviewRequiredNotification
 from .v2_all import TerminalInteractionNotification
 from .v2_all import ThreadArchivedNotification
+from .v2_all import ThreadAttachmentUpdatedNotification
 from .v2_all import ThreadClosedNotification
 from .v2_all import ThreadDeletedNotification
 from .v2_all import ThreadGoalClearedNotification
@@ -135,6 +136,7 @@ KnownNotificationPayload: TypeAlias = (
     | StrictReviewRequiredNotification
     | TerminalInteractionNotification
     | ThreadArchivedNotification
+    | ThreadAttachmentUpdatedNotification
     | ThreadClosedNotification
     | ThreadDeletedNotification
     | ThreadGoalClearedNotification
@@ -216,6 +218,7 @@ NOTIFICATION_MODELS: dict[str, type[KnownNotificationPayload]] = {
     "serverRequest/resolved": ServerRequestResolvedNotification,
     "skills/changed": SkillsChangedNotification,
     "thread/archived": ThreadArchivedNotification,
+    "thread/attachment/updated": ThreadAttachmentUpdatedNotification,
     "thread/closed": ThreadClosedNotification,
     "thread/compacted": ContextCompactedNotification,
     "thread/deleted": ThreadDeletedNotification,

sdk/python/src/openai_codex/generated/v2_all.py

@@ -5034,6 +5034,89 @@ class ThreadArchivedNotification(BaseModel):
     thread_id: Annotated[str, Field(alias="threadId")]
 
 
+class ThreadAttachment(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    attachment_type: Annotated[str, Field(alias="attachmentType")]
+    created_at: Annotated[int, Field(alias="createdAt")]
+    id: str
+    identity_key: Annotated[str, Field(alias="identityKey")]
+    payload: Any
+
+
+class ThreadAttachmentAddOutcome(Enum):
+    created = "created"
+    existing = "existing"
+
+
+class ThreadAttachmentAddParams(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    attachment_type: Annotated[str, Field(alias="attachmentType")]
+    identity_key: Annotated[str, Field(alias="identityKey")]
+    payload: Any
+    thread_id: Annotated[str, Field(alias="threadId")]
+
+
+class ThreadAttachmentAddResponse(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    attachment: ThreadAttachment
+    outcome: ThreadAttachmentAddOutcome
+
+
+class ThreadAttachmentListParams(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    cursor: str | None = None
+    limit: Annotated[int | None, Field(ge=0)] = None
+    thread_id: Annotated[str, Field(alias="threadId")]
+
+
+class ThreadAttachmentListResponse(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    data: list[ThreadAttachment]
+    next_cursor: Annotated[str | None, Field(alias="nextCursor")] = None
+
+
+class ThreadAttachmentOperation(Enum):
+    created = "created"
+    deleted = "deleted"
+
+
+class ThreadAttachmentRemoveParams(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    attachment_type: Annotated[str, Field(alias="attachmentType")]
+    identity_key: Annotated[str, Field(alias="identityKey")]
+    thread_id: Annotated[str, Field(alias="threadId")]
+
+
+class ThreadAttachmentRemoveResponse(BaseModel):
+    pass
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+
+
+class ThreadAttachmentUpdatedNotification(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    attachment_id: Annotated[str, Field(alias="attachmentId")]
+    attachment_type: Annotated[str, Field(alias="attachmentType")]
+    identity_key: Annotated[str, Field(alias="identityKey")]
+    operation: ThreadAttachmentOperation
+    thread_id: Annotated[str, Field(alias="threadId")]
+
+
 class ThreadClosedNotification(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,
@@ -6638,6 +6721,39 @@ class ThreadMetadataUpdateRequest(BaseModel):
     params: ThreadMetadataUpdateParams
 
 
+class ThreadAttachmentAddRequest(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    id: RequestId
+    method: Annotated[
+        Literal["thread/attachment/add"], Field(title="Thread/attachment/addRequestMethod")
+    ]
+    params: ThreadAttachmentAddParams
+
+
+class ThreadAttachmentListRequest(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    id: RequestId
+    method: Annotated[
+        Literal["thread/attachment/list"], Field(title="Thread/attachment/listRequestMethod")
+    ]
+    params: ThreadAttachmentListParams
+
+
+class ThreadAttachmentRemoveRequest(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    id: RequestId
+    method: Annotated[
+        Literal["thread/attachment/remove"], Field(title="Thread/attachment/removeRequestMethod")
+    ]
+    params: ThreadAttachmentRemoveParams
+
+
 class ThreadSectionMoveRequest(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,
@@ -8776,6 +8892,24 @@ class ThreadNameUpdatedServerNotification(BaseModel):
     params: ThreadNameUpdatedNotification
 
 
+class ThreadAttachmentUpdatedServerNotification(BaseModel):
+    model_config = ConfigDict(
+        populate_by_name=True,
+    )
+    emitted_at_ms: Annotated[
+        int | None,
+        Field(
+            alias="emittedAtMs",
+            description="Unix timestamp (in milliseconds) when app-server emitted this notification.",
+        ),
+    ] = None
+    method: Annotated[
+        Literal["thread/attachment/updated"],
+        Field(title="Thread/attachment/updatedNotificationMethod"),
+    ]
+    params: ThreadAttachmentUpdatedNotification
+
+
 class ThreadGoalClearedServerNotification(BaseModel):
     model_config = ConfigDict(
         populate_by_name=True,
@@ -11957,6 +12091,9 @@ class ClientRequest(
         | ThreadGoalGetRequest
         | ThreadGoalClearRequest
         | ThreadMetadataUpdateRequest
+        | ThreadAttachmentAddRequest
+        | ThreadAttachmentListRequest
+        | ThreadAttachmentRemoveRequest
         | ThreadSectionMoveRequest
         | ThreadUnarchiveRequest
         | ThreadCompactStartRequest
@@ -12062,6 +12199,9 @@ class ClientRequest(
         | ThreadGoalGetRequest
         | ThreadGoalClearRequest
         | ThreadMetadataUpdateRequest
+        | ThreadAttachmentAddRequest
+        | ThreadAttachmentListRequest
+        | ThreadAttachmentRemoveRequest
         | ThreadSectionMoveRequest
         | ThreadUnarchiveRequest
         | ThreadCompactStartRequest
@@ -12336,6 +12476,7 @@ class ServerNotification(
         | ThreadRevertedServerNotification
         | SkillsChangedServerNotification
         | ThreadNameUpdatedServerNotification
+        | ThreadAttachmentUpdatedServerNotification
         | ThreadGoalUpdatedServerNotification
         | ThreadGoalClearedServerNotification
         | ThreadQueueChangedServerNotification
@@ -12423,6 +12564,7 @@ class ServerNotification(
         | ThreadRevertedServerNotification
         | SkillsChangedServerNotification
         | ThreadNameUpdatedServerNotification
+        | ThreadAttachmentUpdatedServerNotification
         | ThreadGoalUpdatedServerNotification
         | ThreadGoalClearedServerNotification
         | ThreadQueueChangedServerNotification