diff --git a/s16code/events/engine.py b/s16code/events/engine.py
index ab32753..cf79db6 100644
--- a/s16code/events/engine.py
+++ b/s16code/events/engine.py
@@ -25,6 +25,32 @@ def _json_object(text: str) -> dict[str, Any]:
     return value
 
 
+def _run_spend_of(result: dict[str, Any]) -> float:
+    """What the run cost, read from where the runtime actually reports it.
+
+    `Runtime.run` returns spend inside `budget` — `run_budget.snapshot()`, which
+    carries `total` and `spent`. There is no `spend_usd` key; reading one recorded
+    every run at $0.00, so `daily_budget` could never bind, a run's ceiling was
+    never squeezed by what the window had left, and the morning report showed a
+    night that cost nothing.
+
+    `spend_usd` is still honoured, so any caller or fake supplying it keeps working.
+    """
+    direct = result.get("spend_usd")
+    if direct is not None:
+        try:
+            return float(direct)
+        except (TypeError, ValueError):
+            return 0.0
+    budget = result.get("budget")
+    if isinstance(budget, dict):
+        try:
+            return float(budget.get("spent") or 0.0)
+        except (TypeError, ValueError):
+            return 0.0
+    return 0.0
+
+
 def _spend_of(reply: dict[str, Any]) -> float:
     """What the gate itself cost. Deciding not to act is not free."""
     total = 0.0
@@ -145,7 +171,7 @@ async def decide(subscription: Subscription) -> dict[str, Any]:
                         initial_evidence={"event": event.model_dump(mode="json")},
                     )
                     self.governor.record(subscription.id, kind="run",
-                                         usd=float(result.get("spend_usd") or 0.0), now=now)
+                                         usd=_run_spend_of(result), now=now)
                     decision.update(run_id=result["run_id"], run_status=result["status"], acted=True)
                 self.store.add_decision(event.source, event.id, decision)
                 return decision
diff --git a/tests/test_run_spend_is_recorded.py b/tests/test_run_spend_is_recorded.py
new file mode 100644
index 0000000..bd09920
--- /dev/null
+++ b/tests/test_run_spend_is_recorded.py
@@ -0,0 +1,175 @@
+"""`daily_budget` must be fed what a run actually cost.
+
+`AutonomousEventEngine` records a completed run's spend like this:
+
+    self.governor.record(subscription.id, kind="run",
+                         usd=float(result.get("spend_usd") or 0.0), now=now)
+
+`Runtime.run()` never returns a `spend_usd` key. Its result dict is:
+
+    {"run_id", "status", "answer", "provider", "model", "graph", "trace",
+     "events", "principal", "budget", "economics", "allocations"}
+
+The real figure is `result["budget"]["spent"]`. So `.get("spend_usd")` is always
+None, every run is recorded at $0.00, and `window_spend(..., kind="run")` stays
+zero for the life of the installation.
+
+## Three consequences, one root cause
+
+1. `daily_budget` can never bind. `admit_run` compares the window's run spend
+   against it, and that spend is always 0. Section 10 makes this the ceiling that
+   survives "escape the budget by starting more runs".
+
+2. The per-run ceiling is never squeezed by the window. `admit_run` computes
+   `remaining = daily_budget - spent` and hands the run
+   `min(per_run, remaining)`; with `spent` pinned at 0, `remaining` is always the
+   full daily budget. Section 10 asks for "each run's ceiling shrunk by whatever
+   the window has left". It never shrinks.
+
+3. The morning report's "cost of doing" is always $0.00. Observed live on
+   2026-08-10 after four real runs against Gemini:
+
+       - acted: 4
+       - cost of watching: $0.00066000
+       - cost of doing:    $0.00000000
+
+   An operator reading Section 9's report sees a night that cost nothing.
+
+`max_runs_per_day` still bounds the count, so this is not unbounded spend - but
+the money ceiling specifically is inert, and the report understates the bill.
+
+## Why the suite did not catch it
+
+`tests/test_autonomy_governor.py` defines
+
+    class _Runtime:
+        async def run(self, *, prompt, **_):
+            return {"run_id": ..., "status": "completed", "spend_usd": self.spend}
+
+The stub invents the key production never sends, so
+`test_a_daily_budget_caps_the_window_and_shrinks_the_last_run` passes while the
+control it covers cannot fire. Section 12: "a green check on a control that never
+ran is worse than a red one." This is the second instance of that shape in the
+same file - the other was `metered_calls` for triage.
+
+The stub here deliberately mirrors the *real* `Runtime.run` contract instead.
+"""
+
+from __future__ import annotations
+
+import json
+from datetime import UTC, datetime
+
+import pytest
+
+from s16code.events import (
+    AutonomousEventEngine,
+    EventEnvelope,
+    EventStore,
+    Subscription,
+)
+
+
+def _event(**changes) -> EventEnvelope:
+    body = {"id": "e1", "source": "deployments", "type": "deployment.completed",
+            "subject": "checkout/production", "occurred_at": datetime.now(UTC),
+            "data": {"previous_error_rate": 0.7, "current_error_rate": 6.4}}
+    body.update(changes)
+    return EventEnvelope(**body)
+
+
+def _subscription(**changes) -> Subscription:
+    body = {"id": "watch", "instruction": "Assess material error-rate increases.",
+            "event_types": ["deployment.completed"], "sources": ["deployments"],
+            "tenant_id": "course", "allowed_side_effects": [], "budget": 0.01}
+    body.update(changes)
+    return Subscription(**body)
+
+
+class _RealShapedRuntime:
+    """Returns what `s16code.runtime.Runtime.run` actually returns.
+
+    Note what is absent: `spend_usd`. Spend is reported inside `budget`, which is
+    `run_budget.snapshot()` - `{"total": ..., "spent": ...}`.
+    """
+
+    def __init__(self, spend: float = 0.004) -> None:
+        self.runs: list[str] = []
+        self.spend = spend
+
+    async def run(self, *, prompt: str, **_: object) -> dict[str, object]:
+        self.runs.append(prompt)
+        return {
+            "run_id": f"run-{len(self.runs)}",
+            "status": "completed",
+            "answer": "assessed",
+            "provider": "gemini",
+            "model": "gemini-3.1-flash-lite",
+            "graph": {"finished": True, "nodes": {}, "edges": []},
+            "trace": {"planner": {}, "agents": []},
+            "events": [],
+            "principal": "course",
+            "budget": {"total": 0.01, "spent": self.spend},
+            "economics": None,
+            "allocations": [],
+        }
+
+
+def _relevance_llm(cost: float = 0.00002):
+    async def llm(prompt: str, system: str):  # noqa: ARG001
+        return {"text": json.dumps({"relevant": True, "reason": "error rate rose",
+                                    "goal": "Assess the increase."}),
+                "metered_calls": [{"cost_usd": cost}]}
+    return llm
+
+
+def _day(moment: datetime | None = None) -> str:
+    return (moment or datetime.now(UTC)).strftime("%Y-%m-%d")
+
+
+async def test_a_completed_run_records_what_it_spent(tmp_path) -> None:
+    store = EventStore(tmp_path)
+    runtime = _RealShapedRuntime(spend=0.004)
+    engine = AutonomousEventEngine(store, runtime)
+    store.put_subscription(_subscription())
+
+    await engine.process(_event(id="spend-1"), llm=_relevance_llm())
+
+    recorded = store.window_spend("watch", _day(), kind="run")
+    assert recorded == pytest.approx(0.004), (
+        f"the run spent $0.004 and the ledger recorded ${recorded:.8f}; the engine "
+        "reads result['spend_usd'], a key Runtime.run does not return"
+    )
+
+
+async def test_daily_budget_actually_refuses_once_the_window_is_spent(tmp_path) -> None:
+    """The control Section 10 relies on, exercised against the real result shape."""
+    store = EventStore(tmp_path)
+    runtime = _RealShapedRuntime(spend=0.004)
+    engine = AutonomousEventEngine(store, runtime)
+    store.put_subscription(_subscription(budget=0.004, daily_budget=0.01))
+
+    for index in range(4):
+        await engine.process(_event(id=f"spend-{index}"), llm=_relevance_llm())
+
+    assert len(runtime.runs) < 4, (
+        f"all {len(runtime.runs)} runs were admitted against a $0.01 daily budget "
+        "at $0.004 each; the window ceiling never fired"
+    )
+    assert any(item["control"] == "daily_budget" for item in store.refusals()), (
+        "no daily_budget refusal was recorded, so nothing tells an operator the "
+        "window stopped the work"
+    )
+
+
+async def test_the_remaining_window_shrinks_a_later_run(tmp_path) -> None:
+    """Section 10: a run's ceiling is cut down by whatever the window has left."""
+    store = EventStore(tmp_path)
+    runtime = _RealShapedRuntime(spend=0.004)
+    engine = AutonomousEventEngine(store, runtime)
+    store.put_subscription(_subscription(budget=0.01, daily_budget=0.01))
+
+    await engine.process(_event(id="first"), llm=_relevance_llm())
+    spent = store.window_spend("watch", _day(), kind="run")
+    assert spent > 0, "nothing was recorded, so no later run can be squeezed"
+    assert spent < 0.01