fix(tui): chrome cost from Nous portal headers only (F3)

The status-bar cost segment must show cost ONLY when running against the Nous
portal — per-model cache/input/output pricing is unreliable across the model
long tail, so a guessed figure is worse than none.

- New nous_header_cost_usd(agent): the chrome cost source, derived ONLY from the
  x-nous-credits-* header delta (deliberately ignores the OpenRouter usage.cost
  accumulator). _get_usage now uses it for cost_usd, so a non-Nous session
  reports no cost and the TUI hides the segment.
- The /usage accounting page is unchanged in spirit: it now reads
  real_session_cost_usd(agent) directly (both provider-reported sources) instead
  of the chrome-narrowed _get_usage cost_usd, so OpenRouter cost still shows there.

Tests: new TestNousHeaderCost (header-only, OR-accumulator ignored, clamp,
no-method); updated gateway _get_usage tests for the chrome narrowing; /usage
page test still asserts the full provider-reported figure. 316 gateway + 25 cost
tests green.

agent/usage_pricing.py

@@ -919,6 +919,33 @@ def real_session_cost_usd(agent: Any) -> Optional[float]:
     return total
 
 
+def nous_header_cost_usd(agent: Any) -> Optional[float]:
+    """Session-cumulative cost in USD derived ONLY from the Nous portal
+    ``x-nous-credits-*`` header delta, or None.
+
+    This is the STATUS-BAR cost source (glitch 2026-06-13, F3): the TUI chrome
+    must show cost ONLY when the session runs against the Nous portal, because
+    the header delta is the one figure we can trust without re-deriving per-model
+    cache/input/output pricing (which is unreliable across the model long tail).
+    Unlike :func:`real_session_cost_usd`, this DELIBERATELY ignores the
+    OpenRouter ``usage.cost`` accumulator — a non-Nous route reports no header,
+    so the chrome hides its cost segment entirely.
+
+    The ``/usage`` accounting page keeps using ``real_session_cost_usd`` (both
+    provider-reported sources); only the chrome bar narrows to header-only.
+    """
+    try:
+        spent_micros = agent.get_credits_spent_micros()
+    except Exception:
+        return None
+    if spent_micros is None:
+        return None
+    try:
+        return max(0, int(spent_micros)) / 1_000_000
+    except (TypeError, ValueError):
+        return None
+
+
 def has_known_pricing(
     model_name: str,
     provider: Optional[str] = None,

tests/agent/test_provider_cost_capture.py

@@ -10,7 +10,7 @@ from types import SimpleNamespace
 
 import pytest
 
-from agent.usage_pricing import extract_provider_cost_usd, real_session_cost_usd
+from agent.usage_pricing import extract_provider_cost_usd, nous_header_cost_usd, real_session_cost_usd
 
 
 # ── extract_provider_cost_usd — the per-response REAL cost reader ────────────
@@ -86,6 +86,32 @@ class TestRealSessionCost:
         assert real_session_cost_usd(agent) is None
 
 
+# ── nous_header_cost_usd — the CHROME status-bar cost (F3: header-only) ──────
+
+
+class TestNousHeaderCost:
+    def test_header_delta_only(self):
+        # 123_400 micros = $0.1234 — the Nous header source feeds the chrome.
+        assert nous_header_cost_usd(_FakeAgent(credits_micros=123_400)) == pytest.approx(0.1234)
+
+    def test_openrouter_accumulator_ignored(self):
+        # The OpenRouter usage.cost accumulator must NOT feed the chrome bar:
+        # a non-Nous session (no header → None) reports no cost even when the
+        # OpenRouter accumulator has a value.
+        assert nous_header_cost_usd(_FakeAgent(actual=0.42)) is None
+
+    def test_no_header_is_none(self):
+        assert nous_header_cost_usd(_FakeAgent()) is None
+
+    def test_negative_delta_clamped(self):
+        # A mid-session top-up makes the delta negative — never show negative.
+        assert nous_header_cost_usd(_FakeAgent(credits_micros=-50_000)) == 0.0
+
+    def test_agent_without_credits_method_is_none(self):
+        agent = SimpleNamespace(session_actual_cost_usd=0.42)
+        assert nous_header_cost_usd(agent) is None
+
+
 # ── Nous header fixture → real accumulator (full _capture_credits path) ─────
 
 

tests/test_tui_gateway_server.py

@@ -7444,11 +7444,15 @@ def test_get_usage_cost_absent_when_provider_reports_nothing(monkeypatch):
     assert usage["input"] == 35_000
 
 
-def test_get_usage_cost_present_when_provider_reported(monkeypatch):
+def test_get_usage_cost_absent_for_openrouter_accumulator_chrome(monkeypatch):
+    """F3: the chrome status bar shows cost ONLY from the Nous header delta.
+    An OpenRouter usage.cost accumulator alone (no x-nous-credits header) must
+    NOT surface cost_usd in _get_usage — the chrome hides cost off-Nous. (The
+    /usage accounting page still counts the accumulator; that's a separate path.)
+    """
     agent = _usage_agent(session_actual_cost_usd=0.4321)
     usage = server._get_usage(agent)
-    assert usage["cost_usd"] == pytest.approx(0.4321)
-    assert usage["cost_status"] == "actual"
+    assert "cost_usd" not in usage
 
 
 def test_get_usage_cost_from_nous_credits_delta(monkeypatch):
@@ -7456,6 +7460,7 @@ def test_get_usage_cost_from_nous_credits_delta(monkeypatch):
     agent.get_credits_spent_micros = lambda: 250_000  # $0.25 real header delta
     usage = server._get_usage(agent)
     assert usage["cost_usd"] == pytest.approx(0.25)
+    assert usage["cost_status"] == "actual"
 
 
 def test_compact_usage_per_model_rows_and_real_cost(monkeypatch):

tui_gateway/server.py

@@ -2154,14 +2154,17 @@ def _get_usage(agent) -> dict:
             usage["context_max"] = ctx_max
             usage["context_percent"] = max(0, min(100, round(ctx_used / ctx_max * 100)))
         usage["compressions"] = getattr(comp, "compression_count", 0) or 0
-    # Cost: provider-REPORTED only (OpenRouter usage.cost accumulator and/or
-    # the Nous x-nous-credits-* header delta). Never estimated. When nothing
-    # was reported `cost_usd` is ABSENT (not $0.00) and the TUI hides its
-    # cost segment — that's the intended UX.
+    # Cost (chrome status bar): Nous portal header delta ONLY (F3, glitch
+    # 2026-06-13). The OpenRouter usage.cost accumulator is deliberately NOT
+    # used here — per-model cache/input/output pricing is unreliable across the
+    # model long tail, so the bar shows cost ONLY on a Nous-portal session and
+    # hides it everywhere else. `cost_usd` is ABSENT (not $0.00) when no header
+    # was seen, and the TUI hides its cost segment. (The /usage accounting page
+    # still uses real_session_cost_usd — both provider-reported sources.)
     try:
-        from agent.usage_pricing import real_session_cost_usd
+        from agent.usage_pricing import nous_header_cost_usd
 
-        real_cost = real_session_cost_usd(agent)
+        real_cost = nous_header_cost_usd(agent)
         if real_cost is not None:
             usage["cost_usd"] = real_cost
             usage["cost_status"] = "actual"
@@ -2234,7 +2237,17 @@ def _compact_usage_text(session: dict) -> str:
             tail.append(f"compressions {u['compressions']}")
         lines.append("  " + " · ".join(tail))
 
-        cost_usd = u.get("cost_usd")
+        # The /usage page reports the FULL provider-reported cost (OpenRouter
+        # usage.cost accumulator AND/OR the Nous header delta) — NOT the chrome's
+        # Nous-header-only figure (F3 narrowed `_get_usage["cost_usd"]` to the
+        # status bar). Read it straight from real_session_cost_usd here so the
+        # accounting page keeps both sources.
+        try:
+            from agent.usage_pricing import real_session_cost_usd
+
+            cost_usd = real_session_cost_usd(agent)
+        except Exception:
+            cost_usd = None
         if cost_usd is not None:
             lines.append(f"  session cost: ${cost_usd:.4f} (provider-reported)")
         else: