Sign in with a ChatGPT subscription for inference (#854)

Co-authored-by: Jonathan Singer <jonathansinger@Jonathans-MacBook-Pro.local>
Co-authored-by: Jonathan Singer <jonathansinger@Mac-3004.lan>
Co-authored-by: Ahmed Allam <ahmed39652003@gmail.com>

tests/test_usage_subscription.py

@@ -0,0 +1,46 @@
+"""Subscription runs track tokens but report zero cost."""
+
+from __future__ import annotations
+
+from agents.usage import Usage
+
+from strix.report.usage import LLMUsageLedger
+
+
+def _usage() -> Usage:
+    usage = Usage()
+    usage.requests = 1
+    usage.input_tokens = 1000
+    usage.output_tokens = 200
+    usage.total_tokens = 1200
+    return usage
+
+
+def test_zero_cost_ledger_keeps_tokens_but_reports_no_cost() -> None:
+    ledger = LLMUsageLedger()
+    ledger.zero_cost = True
+    ledger.record(agent_id="a", usage=_usage(), agent_name="strix", model="gpt-5.5")
+
+    record = ledger.to_record()
+    assert record["cost"] == 0.0
+    assert record["total_tokens"] == 1200
+    assert record["input_tokens"] == 1000
+    assert record["output_tokens"] == 200
+    assert ledger.total_cost == 0.0
+
+
+def test_zero_cost_ledger_ignores_observed_cost() -> None:
+    ledger = LLMUsageLedger()
+    ledger.zero_cost = True
+    ledger.record_observed_cost(4.20)
+    assert ledger.total_cost == 0.0
+
+
+def test_normal_ledger_still_estimates_cost() -> None:
+    # Sanity check the flag is opt-in: without it, an OpenAI-native model still
+    # accrues an estimated cost (proves zeroing is what suppresses it).
+    ledger = LLMUsageLedger()
+    ledger.record(agent_id="a", usage=_usage(), agent_name="strix", model="gpt-5.5")
+    assert ledger.to_record()["total_tokens"] == 1200
+    # Cost estimation depends on litellm's cost map; it should be >= 0 and not error.
+    assert ledger.total_cost >= 0.0