fix: reanchor live context usage updates

api/streaming.py

@@ -1939,6 +1939,7 @@ def _run_agent_streaming(
 
     agent = None
     _live_prompt_estimate_tokens = [0]
+    _live_prompt_exact_tokens = [0]
     _live_prompt_estimate_seen_ids = set()
 
     def _seed_live_prompt_estimate() -> int:
@@ -1961,6 +1962,7 @@ def _run_agent_streaming(
             except Exception:
                 _base = 0
         _live_prompt_estimate_tokens[0] = int(_base or 0)
+        _live_prompt_exact_tokens[0] = _live_prompt_estimate_tokens[0]
         return _live_prompt_estimate_tokens[0]
 
     def _bump_live_prompt_estimate(messages) -> int:
@@ -2023,7 +2025,11 @@ def _run_agent_streaming(
                     except Exception:
                         pass
 
-        if _live_prompt_estimate_tokens[0] > (_usage.get('last_prompt_tokens') or 0):
+        _real_prompt_tokens = int(_usage.get('last_prompt_tokens') or 0)
+        if _real_prompt_tokens and _real_prompt_tokens != _live_prompt_exact_tokens[0]:
+            _live_prompt_exact_tokens[0] = _real_prompt_tokens
+            _live_prompt_estimate_tokens[0] = _real_prompt_tokens
+        elif _live_prompt_estimate_tokens[0] > _real_prompt_tokens:
             _usage['last_prompt_tokens'] = _live_prompt_estimate_tokens[0]
 
         return _usage

static/messages.js

@@ -1161,14 +1161,6 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
         if((d.session_id||activeSid)!==activeSid) return;
         if(d.usage&&typeof _syncCtxIndicator==='function'){
           S.lastUsage={...(S.lastUsage||{}),...d.usage};
-          if(S.session&&S.session.session_id===activeSid){
-            S.session.input_tokens=d.usage.input_tokens??S.session.input_tokens;
-            S.session.output_tokens=d.usage.output_tokens??S.session.output_tokens;
-            S.session.estimated_cost=d.usage.estimated_cost??S.session.estimated_cost;
-            S.session.context_length=d.usage.context_length??S.session.context_length;
-            S.session.threshold_tokens=d.usage.threshold_tokens??S.session.threshold_tokens;
-            S.session.last_prompt_tokens=d.usage.last_prompt_tokens??S.session.last_prompt_tokens;
-          }
           _syncCtxIndicator(S.lastUsage);
         }
         if(d.estimated===true||d.tps_available!==true||typeof d.tps!=='number'||d.tps<=0){

tests/test_issue1617_tps_message_header.py

@@ -46,6 +46,32 @@ def test_live_metering_updates_only_real_tps_and_never_placeholders():
     )
 
 
+def test_live_metering_usage_is_provisional_until_done():
+    listener_start = MESSAGES_JS.find("source.addEventListener('metering'")
+    assert listener_start != -1, "messages.js should listen for metering SSE events"
+    listener_end = MESSAGES_JS.find("source.addEventListener('apperror'", listener_start)
+    assert listener_end != -1, "apperror listener should follow metering listener"
+    listener = MESSAGES_JS[listener_start:listener_end]
+
+    assert "S.lastUsage={...(S.lastUsage||{}),...d.usage}" in listener, (
+        "live usage should update the transient usage cache for the indicator"
+    )
+    assert "_syncCtxIndicator(S.lastUsage)" in listener, (
+        "live usage should refresh the context indicator"
+    )
+    assert "S.session.input_tokens=d.usage.input_tokens" not in listener
+    assert "S.session.last_prompt_tokens=d.usage.last_prompt_tokens" not in listener
+
+
+def test_live_prompt_estimate_reanchors_to_fresh_exact_prompt_tokens():
+    assert "_live_prompt_exact_tokens = [0]" in STREAMING_PY, (
+        "live prompt estimates need a separate exact-token anchor"
+    )
+    assert "_real_prompt_tokens = int(_usage.get('last_prompt_tokens') or 0)" in STREAMING_PY
+    assert "_real_prompt_tokens != _live_prompt_exact_tokens[0]" in STREAMING_PY
+    assert "_live_prompt_estimate_tokens[0] = _real_prompt_tokens" in STREAMING_PY
+
+
 def test_done_payload_persists_final_tps_when_exact_usage_available():
     assert "usage['tps']" in STREAMING_PY, "done usage payload should include final exact TPS when available"
     assert "output_tokens" in STREAMING_PY and "duration_seconds" in STREAMING_PY, (