diff --git a/CLAUDE.md b/CLAUDE.md
index 60acb4b..373c0cf 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -140,6 +140,9 @@ AGENT_EVENT_BUS_ICON=/path/to/icon.png agent-event-bus
 
 # Disable Tailscale auth (for testing/local dev)
 AGENT_EVENT_BUS_AUTH_DISABLED=1 agent-event-bus
+
+# CLI session attribution (used by hooks)
+AGENT_EVENT_BUS_SESSION_ID=abc123 agent-event-bus-cli publish ...
 ```
 
 Notifications: Uses terminal-notifier if installed (`brew install terminal-notifier`), falls back to osascript.
diff --git a/src/agent_event_bus/cli.py b/src/agent_event_bus/cli.py
index 5e5d1b3..8950dc2 100644
--- a/src/agent_event_bus/cli.py
+++ b/src/agent_event_bus/cli.py
@@ -218,8 +218,10 @@ def cmd_publish(args):
     }
     if args.channel:
         arguments["channel"] = args.channel
-    if args.session_id:
-        arguments["session_id"] = args.session_id
+    # Use explicit --session-id, fall back to env var
+    session_id = args.session_id or os.environ.get("AGENT_EVENT_BUS_SESSION_ID")
+    if session_id:
+        arguments["session_id"] = session_id
 
     result = call_tool("publish_event", arguments, url=args.url, debug=args.debug)
     print(json.dumps(result, indent=2))
@@ -341,7 +343,9 @@ def main():
     p_publish.add_argument("--type", required=True, help="Event type")
     p_publish.add_argument("--payload", required=True, help="Event payload")
     p_publish.add_argument("--channel", default="all", help="Target channel")
-    p_publish.add_argument("--session-id", help="Your session ID")
+    p_publish.add_argument(
+        "--session-id", help="Your session ID (default: $AGENT_EVENT_BUS_SESSION_ID)"
+    )
     p_publish.set_defaults(func=cmd_publish)
 
     # events
diff --git a/tests/test_cli.py b/tests/test_cli.py
index ebcdbe3..70eac20 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -271,6 +271,39 @@ def test_publish_with_channel(self, mock_call):
         assert call_args["channel"] == "repo:my-repo"
         assert call_args["session_id"] == "abc123"
 
+    @patch("agent_event_bus.cli.call_tool")
+    @patch.dict("os.environ", {"AGENT_EVENT_BUS_SESSION_ID": "env-session-123"})
+    def test_publish_session_id_from_env(self, mock_call):
+        """Test publish uses session_id from env var when not provided."""
+        mock_call.return_value = {"event_id": 1}
+
+        args = Namespace(
+            type="test_event", payload="hello", channel=None, session_id=None, url=None, debug=False
+        )
+        cli.cmd_publish(args)
+
+        call_args = mock_call.call_args[0][1]
+        assert call_args["session_id"] == "env-session-123"
+
+    @patch("agent_event_bus.cli.call_tool")
+    @patch.dict("os.environ", {"AGENT_EVENT_BUS_SESSION_ID": "env-session-123"})
+    def test_publish_explicit_session_id_overrides_env(self, mock_call):
+        """Test explicit --session-id overrides env var."""
+        mock_call.return_value = {"event_id": 1}
+
+        args = Namespace(
+            type="test_event",
+            payload="hello",
+            channel=None,
+            session_id="explicit-123",
+            url=None,
+            debug=False,
+        )
+        cli.cmd_publish(args)
+
+        call_args = mock_call.call_args[0][1]
+        assert call_args["session_id"] == "explicit-123"
+
 
 class TestCmdEvents:
     """Tests for events command."""