Add golden fixtures and contract tests for structured route logs

tests/samples/router_logs_contract.ndjson

@@ -0,0 +1,7 @@
+INFO:     127.0.0.1:1 - "GET /health HTTP/1.1" 200 OK
+{"event":"route_complete","route_id":"chat.strong","target_model":"pro-router","policy_id":"hard_rule","reason":"hard_rule:vip","request_id":"req_001","stream":true,"duration_ms":312.5,"upstream_status":200}
+{"event":"route_error","route_id":"chat.strong","target_model":"pro-router","policy_id":"embedding_error","reason":"embedding_error","request_id":"req_002","stream":true,"duration_ms":489,"error_type":"UpstreamStatusError","upstream_status":503,"upstream_error":"gateway_timeout"}
+{"event":"route_complete","route_id":null,"target_model":"base-router","policy_id":"passthrough","reason":"passthrough","request_id":"req_003","stream":false,"duration_ms":142,"upstream_status":200}
+{"event":"route_error","target_model":"legacy-router","policy_id":"hard_rule","reason":"hard_rule:legacy","request_id":"req_004","stream":false,"duration_ms":220,"error_type":"RemoteProtocolError","upstream_status":502,"upstream_error":"legacy_bad_gateway"}
+{"event":"startup"}
+{"event":"route_error",

tests/test_check_route_error_budget.py

@@ -3,6 +3,7 @@
 import json
 import subprocess
 import sys
+from pathlib import Path
 
 from scripts.check_route_error_budget import BudgetConfig, check_budget, format_budget_result, main
 from scripts.router_log_summary import ParseDiagnostics, parse_route_records
@@ -635,3 +636,25 @@ def test_script_file_execution_returns_nonzero_for_failing_budget():
     assert completed.returncode != 0
     assert completed.stdout.startswith("FAIL route_error_budget\n")
     assert "error_rate 1.0000 exceeds max_error_rate 0.0000" in completed.stdout
+
+def test_contract_fixture_budget_includes_route_and_target_buckets():
+    fixture = Path("tests/samples/router_logs_contract.ndjson")
+    diagnostics = ParseDiagnostics()
+    records = list(parse_route_records(fixture.read_text().splitlines(), diagnostics=diagnostics))
+
+    result = check_budget(
+        records,
+        BudgetConfig(min_total=1, max_error_rate=1.0, max_target_error_rate=1.0),
+        parse_diagnostics=diagnostics,
+    )
+
+    assert result.passed is True
+    assert result.target_error_rates == {
+        "base-router": 0.0,
+        "legacy-router": 1.0,
+        "pro-router": 0.5,
+    }
+    assert result.route_error_rates == {"chat.strong": 0.5, "unknown": 0.5}
+    assert result.error_types == {"RemoteProtocolError": 1, "UpstreamStatusError": 1}
+    assert result.parse_diagnostics.malformed_json_lines == 1
+    assert result.parse_diagnostics.unknown_event_records == 1

tests/test_router_log_summary.py

@@ -3,6 +3,7 @@
 import json
 import subprocess
 import sys
+from pathlib import Path
 
 from scripts.router_log_summary import (
     ParseDiagnostics,
@@ -311,3 +312,35 @@ def test_main_short_json_flag_outputs_machine_readable_json():
         },
         "upstream_statuses": {"200": 1, "503": 1},
     }
+
+def test_contract_fixture_summary_separates_routes_and_targets():
+    fixture = Path("tests/samples/router_logs_contract.ndjson")
+    diagnostics = ParseDiagnostics()
+    records = list(parse_route_records(fixture.read_text().splitlines(), diagnostics=diagnostics))
+
+    summary = summarize_records(records, parse_diagnostics=diagnostics)
+
+    assert summary.total == 4
+    assert summary.completed == 2
+    assert summary.errors == 2
+    assert summary.routes == {"chat.strong": 2}
+    assert summary.targets == {"base-router": 1, "legacy-router": 1, "pro-router": 2}
+    assert summary.error_types == {"RemoteProtocolError": 1, "UpstreamStatusError": 1}
+    assert summary.parse_diagnostics.malformed_json_lines == 1
+    assert summary.parse_diagnostics.unknown_event_records == 1
+
+
+def test_contract_fixture_has_no_sensitive_payload_fields():
+    fixture_text = Path("tests/samples/router_logs_contract.ndjson").read_text()
+
+    forbidden_patterns = [
+        "prompt",
+        "authorization",
+        "bearer ",
+        "request_body",
+        "raw_body",
+    ]
+    lower_fixture = fixture_text.lower()
+
+    for pattern in forbidden_patterns:
+        assert pattern not in lower_fixture