diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0db7ec0..a1df992 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,7 +13,15 @@ All notable changes to this project will be documented in this file. This change
 - `:custom-tool` permission kind — `::permission-kind` spec now includes `:custom-tool`, matching the upstream `PermissionRequest.kind` union type. Permission handlers will receive `{:permission-kind :custom-tool ...}` for SDK-registered custom tool invocations (upstream PR #555).
 
 ### Added (upstream PR #544 sync)
-- `:copilot/session.task_complete` event type added to `::event-type` spec (from upstream generated session event types).
+- `:copilot/session.task_complete` event type added to `::event-type` spec and `event-types` var. Previously it was in the spec but missing from the public `event-types` set (upstream PR #544).
+- `:copilot/assistant.streaming_delta` new event type: emitted when the total response size changes during streaming. Data: `{:total-response-size-bytes N}`. Added to `::event-type` spec, `event-types` var, and `assistant-events` var (upstream PR #544).
+- `:copilot/session.mode_changed` event type: emitted when the session agent mode changes. Data: `{:previous-mode "...", :new-mode "..."}`. Added to `::event-type` spec, `event-types` var, and `session-events` var.
+- `:copilot/session.plan_changed` event type: emitted when the session plan changes. Data: `{:operation "create"|"update"|"delete"}`. Added to `::event-type` spec, `event-types` var, and `session-events` var.
+- `:copilot/session.workspace_file_changed` event type: emitted when a workspace file is created or updated. Data: `{:path "...", :operation "create"|"update"}`. Added to `::event-type` spec, `event-types` var, and `session-events` var.
+- Data specs for new events: `::session.mode_changed-data`, `::session.plan_changed-data`, `::session.workspace_file_changed-data`, `::session.task_complete-data`, `::assistant.streaming_delta-data`.
+
+### Changed (upstream PR #544 sync)
+- `::assistant.message_delta-data` spec: removed `::total-response-size-bytes` from optional keys. The response size is now delivered via the separate `assistant.streaming_delta` event (upstream PR #544).
 
 ### Added (documentation)
 - Microsoft Foundry Local BYOK provider guide in `doc/auth/byok.md`: quick start example, installation instructions, and connection troubleshooting (upstream PR #461).
diff --git a/doc/reference/API.md b/doc/reference/API.md
index 52079c1..92dc366 100644
--- a/doc/reference/API.md
+++ b/doc/reference/API.md
@@ -861,6 +861,10 @@ copilot/tool-events
 | `:copilot/session.snapshot_rewind` | Session state rolled back |
 | `:copilot/session.compaction_start` | Context compaction started (infinite sessions) |
 | `:copilot/session.compaction_complete` | Context compaction completed (infinite sessions) |
+| `:copilot/session.mode_changed` | Session agent mode changed; data: `{:previous-mode "...", :new-mode "..."}` |
+| `:copilot/session.plan_changed` | Session plan created/updated/deleted; data: `{:operation "create"/"update"/"delete"}` |
+| `:copilot/session.workspace_file_changed` | Workspace file created or updated; data: `{:path "...", :operation "create"/"update"}` |
+| `:copilot/session.task_complete` | Task completed by the session agent; data: `{:summary "..."}` (optional) |
 | `:copilot/skill.invoked` | Skill invocation triggered |
 | `:copilot/user.message` | User message added |
 | `:copilot/pending_messages.modified` | Pending message queue updated |
@@ -870,6 +874,7 @@ copilot/tool-events
 | `:copilot/assistant.reasoning_delta` | Streaming reasoning chunk |
 | `:copilot/assistant.message` | Complete assistant response |
 | `:copilot/assistant.message_delta` | Streaming response chunk |
+| `:copilot/assistant.streaming_delta` | Response size update during streaming; data: `{:total-response-size-bytes N}` |
 | `:copilot/assistant.turn_end` | Assistant turn completed |
 | `:copilot/assistant.usage` | Token usage for this turn |
 | `:copilot/abort` | Current message aborted |
@@ -885,7 +890,6 @@ copilot/tool-events
 | `:copilot/hook.start` | Hook invocation started |
 | `:copilot/hook.end` | Hook invocation finished |
 | `:copilot/system.message` | System message emitted |
-| `:copilot/session.task_complete` | Task completed by the session agent |
 
 ### Example: Handling Events
 
diff --git a/src/github/copilot_sdk.clj b/src/github/copilot_sdk.clj
index 37a3bb9..969bf68 100644
--- a/src/github/copilot_sdk.clj
+++ b/src/github/copilot_sdk.clj
@@ -47,6 +47,10 @@
     :copilot/session.context_changed
     :copilot/session.title_changed
     :copilot/session.warning
+    :copilot/session.mode_changed
+    :copilot/session.plan_changed
+    :copilot/session.workspace_file_changed
+    :copilot/session.task_complete
     :copilot/user.message
     :copilot/pending_messages.modified
     :copilot/assistant.turn_start
@@ -55,6 +59,7 @@
     :copilot/assistant.reasoning_delta
     :copilot/assistant.message
     :copilot/assistant.message_delta
+    :copilot/assistant.streaming_delta
     :copilot/assistant.turn_end
     :copilot/assistant.usage
     :copilot/abort
@@ -89,7 +94,11 @@
     :copilot/session.shutdown
     :copilot/session.context_changed
     :copilot/session.title_changed
-    :copilot/session.warning})
+    :copilot/session.warning
+    :copilot/session.mode_changed
+    :copilot/session.plan_changed
+    :copilot/session.workspace_file_changed
+    :copilot/session.task_complete})
 
 (def assistant-events
   "Assistant response events."
@@ -99,6 +108,7 @@
     :copilot/assistant.reasoning_delta
     :copilot/assistant.message
     :copilot/assistant.message_delta
+    :copilot/assistant.streaming_delta
     :copilot/assistant.turn_end
     :copilot/assistant.usage})
 
diff --git a/src/github/copilot_sdk/specs.clj b/src/github/copilot_sdk/specs.clj
index c0f3ee7..6a95fd8 100644
--- a/src/github/copilot_sdk/specs.clj
+++ b/src/github/copilot_sdk/specs.clj
@@ -356,10 +356,11 @@
     :copilot/session.compaction_start :copilot/session.compaction_complete
     :copilot/session.shutdown :copilot/session.task_complete
     :copilot/session.title_changed :copilot/session.warning :copilot/session.context_changed
+    :copilot/session.mode_changed :copilot/session.plan_changed :copilot/session.workspace_file_changed
     :copilot/user.message :copilot/pending_messages.modified
     :copilot/assistant.turn_start :copilot/assistant.intent :copilot/assistant.reasoning
     :copilot/assistant.reasoning_delta :copilot/assistant.message :copilot/assistant.message_delta
-    :copilot/assistant.turn_end :copilot/assistant.usage
+    :copilot/assistant.streaming_delta :copilot/assistant.turn_end :copilot/assistant.usage
     :copilot/abort
     :copilot/tool.user_requested :copilot/tool.execution_start :copilot/tool.execution_partial_result
     :copilot/tool.execution_progress :copilot/tool.execution_complete
@@ -389,9 +390,14 @@
   (s/keys :req-un [::message-id ::content]
           :opt-un [::tool-requests ::parent-tool-call-id]))
 
+(s/def ::total-response-size-bytes nat-int?)
+
 (s/def ::assistant.message_delta-data
   (s/keys :req-un [::message-id ::delta-content]
-          :opt-un [::total-response-size-bytes ::parent-tool-call-id]))
+          :opt-un [::parent-tool-call-id]))
+
+(s/def ::assistant.streaming_delta-data
+  (s/keys :req-un [::total-response-size-bytes]))
 
 (s/def ::tool.execution_start-data
   (s/keys :req-un [::tool-call-id ::tool-name]
@@ -436,6 +442,27 @@
   (s/keys :req-un [::cwd]
           :opt-un [::git-root ::repository ::branch]))
 
+;; Session mode changed event
+(s/def ::previous-mode string?)
+(s/def ::new-mode string?)
+(s/def ::session.mode_changed-data
+  (s/keys :req-un [::previous-mode ::new-mode]))
+
+;; Session plan changed event
+(s/def ::operation #{"create" "update" "delete"})
+(s/def ::session.plan_changed-data
+  (s/keys :req-un [::operation]))
+
+;; Session workspace file changed event
+;; ::path already defined above; ::operation reused but constrained to create/update
+(s/def ::session.workspace_file_changed-data
+  (s/and (s/keys :req-un [::path ::operation])
+         #(contains? #{"create" "update"} (:operation %))))
+
+;; Session task complete event
+(s/def ::session.task_complete-data
+  (s/keys :opt-un [::summary]))
+
 ;; Skill invoked event
 (s/def ::allowed-tools (s/coll-of string?))