fix(tui): preserve cost when state is truncated (#1086)

Co-authored-by: oyasumi <oyasumi@kantilabs.xyz>

strix/interface/tui/backend/projection.py

@@ -146,7 +146,9 @@ def bounded_state_projection(state: dict[str, Any]) -> dict[str, Any]:
         }
         for message in state["messages"][-5:]
     ]
-    state["usage"] = {}
+    state["usage"] = {
+        key: state["usage"][key] for key in ("total_tokens", "cost") if key in state["usage"]
+    }
     state["error"] = terminal_projection(state["error"], max_string=512)
     state["model_warning"] = terminal_projection(state["model_warning"], max_string=256)
     state["caido_url"] = terminal_projection(state["caido_url"], max_string=256)
@@ -173,7 +175,7 @@ def bounded_state_projection(state: dict[str, Any]) -> dict[str, Any]:
         "model_warning": "",
         "caido_url": None,
         "messages": [],
-        "usage": {},
+        "usage": state["usage"],
         "subscription": state["subscription"],
         "viewer_status": state["viewer_status"],
         "viewer_url": None,

tests/test_tui_backend_server.py

@@ -13,7 +13,7 @@ from agents.tool import ToolOutputImage
 
 from strix.config.settings import DEFAULT_MAX_TURNS
 from strix.interface.tui.backend.controller import TuiController
-from strix.interface.tui.backend.projection import terminal_projection
+from strix.interface.tui.backend.projection import bounded_state_projection, terminal_projection
 from strix.interface.tui.backend.protocol import (
     MAX_COMMAND_BYTES,
     PROTOCOL_CAPABILITIES,
@@ -215,7 +215,11 @@ def test_unicode_heavy_setup_state_stays_within_control_frame_limit() -> None:
         "Any",
         SimpleNamespace(
             caido_url="https://例え.example/" + "道" * 10_000,
-            get_total_llm_usage=lambda: {f"model-{index}": "費" * 10_000 for index in range(20)},
+            get_total_llm_usage=lambda: {
+                "total_tokens": 720_400,
+                "cost": 20.0,
+                **{f"model-{index}": "🔒" * 10_000 for index in range(20)},
+            },
         ),
     )
     server = TuiBackendServer(controller)
@@ -226,6 +230,26 @@ def test_unicode_heavy_setup_state_stays_within_control_frame_limit() -> None:
     assert len(encoded) <= MAX_COMMAND_BYTES
     assert "🔒".encode() in encoded
     assert snapshot["projection_truncated"] is True
+    assert snapshot["usage"] == {"total_tokens": 720_400, "cost": 20.0}
+
+
+def test_defensive_state_projection_preserves_usage_summary() -> None:
+    controller = TuiController(args())
+    controller.report_state = cast(
+        "Any",
+        SimpleNamespace(
+            caido_url=None,
+            get_total_llm_usage=lambda: {"total_tokens": 720_400, "cost": 20.0},
+        ),
+    )
+    state = controller.snapshot()
+    state["provider"] = None
+    state["future_oversized_field"] = "x" * 100_000
+
+    snapshot = bounded_state_projection(state)
+
+    assert snapshot["projection_truncated"] is True
+    assert snapshot["usage"] == {"total_tokens": 720_400, "cost": 20.0}
 
 
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