feat(guards): memory/context budget checks + multi-round T>=2 orchestrator tests

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_guards.py

@@ -0,0 +1,65 @@
+import pytest
+from markovian_rsa_mlx.guards import (
+    estimate_kv_bytes, estimate_total_bytes, check_memory_budget,
+    check_context_budget,
+)
+from markovian_rsa_mlx.config import RSAConfig
+
+
+def test_estimate_kv_bytes_for_known_zaya():
+    bytes_per_token = estimate_kv_bytes(zaya_per_token_bytes=40_000, tokens=16384, parallel=4)
+    assert bytes_per_token == 40_000 * 16384 * 4
+
+
+def test_total_bytes_includes_weights():
+    total = estimate_total_bytes(weights_bytes=4_700_000_000, kv_bytes=2_600_000_000, workspace_bytes=500_000_000)
+    assert total == 4_700_000_000 + 2_600_000_000 + 500_000_000
+
+
+def test_memory_check_returns_ok_when_under_limit():
+    cfg = RSAConfig(parallel=4, chunk_tokens=16384, memory_fraction=0.80)
+    decision = check_memory_budget(
+        cfg=cfg,
+        weights_bytes=4_700_000_000,
+        per_token_kv_bytes=40_000,
+        workspace_bytes=500_000_000,
+        metal_limit_bytes=24_000_000_000,
+    )
+    assert decision.ok is True
+    assert decision.fallback_to_serial is False
+
+
+def test_memory_check_recommends_serial_when_over():
+    cfg = RSAConfig(parallel=8, chunk_tokens=16384, memory_fraction=0.80, auto_serial=True)
+    decision = check_memory_budget(
+        cfg=cfg,
+        weights_bytes=4_700_000_000,
+        per_token_kv_bytes=40_000,
+        workspace_bytes=4_000_000_000,
+        metal_limit_bytes=16_000_000_000,
+    )
+    assert decision.ok is False
+    assert decision.fallback_to_serial is True
+
+
+def test_memory_check_raises_when_auto_serial_disabled():
+    cfg = RSAConfig(parallel=8, chunk_tokens=16384, memory_fraction=0.80, auto_serial=False)
+    with pytest.raises(MemoryError):
+        check_memory_budget(
+            cfg=cfg,
+            weights_bytes=4_700_000_000,
+            per_token_kv_bytes=40_000,
+            workspace_bytes=4_000_000_000,
+            metal_limit_bytes=16_000_000_000,
+        )
+
+
+def test_context_check_passes_within_limit():
+    cfg = RSAConfig(chunk_tokens=8000, tail_tokens=2000, aggregation_subsample=4)
+    check_context_budget(cfg=cfg, prompt_tokens=1000, max_context_tokens=131072)
+
+
+def test_context_check_raises_when_over():
+    cfg = RSAConfig(chunk_tokens=80000, tail_tokens=20000, aggregation_subsample=4)
+    with pytest.raises(ValueError, match="exceed"):
+        check_context_budget(cfg=cfg, prompt_tokens=1000, max_context_tokens=131072)