fix(runtime): reject stale batched source fingerprints

loopx/control_plane/effect_runtime.py

@@ -58,6 +58,12 @@
 _RuntimeSourceSnapshot = tuple[tuple[str, int, int, int], ...]
 
 
+class _RuntimeSourceChanged(RuntimeError):
+    def __init__(self, snapshot: _RuntimeSourceSnapshot) -> None:
+        super().__init__("runtime source changed while hashing")
+        self.snapshot = snapshot
+
+
 @dataclass(frozen=True)
 class _RuntimeRevision:
     fingerprint: str
@@ -290,28 +296,35 @@ def _runtime_fingerprint_for_snapshot(
             assert read.data is not None
             digest.update(relative.encode("utf-8"))
             digest.update(read.data)
+    current_snapshot = _runtime_source_snapshot(source_root)
+    if current_snapshot != snapshot:
+        raise _RuntimeSourceChanged(current_snapshot)
     return digest.hexdigest()
 
 
 def _runtime_fingerprint() -> str:
     root = _control_plane_root()
     resolved_root = os.fspath(root.resolve())
-    try:
-        return _runtime_fingerprint_for_snapshot(
-            resolved_root,
-            _runtime_source_snapshot(root),
-        )
-    except FileNotFoundError:
+    snapshot: _RuntimeSourceSnapshot | None = None
+    last_error: Exception | None = None
+    for _attempt in range(2):
         try:
+            if snapshot is None:
+                snapshot = _runtime_source_snapshot(root)
             return _runtime_fingerprint_for_snapshot(
                 resolved_root,
-                _runtime_source_snapshot(root),
+                snapshot,
             )
+        except _RuntimeSourceChanged as exc:
+            last_error = exc
+            snapshot = exc.snapshot
         except FileNotFoundError as exc:
-            raise EffectRuntimeStartupError(
-                "TypeScript Effect runtime source topology did not stabilize",
-                diagnostic_code="packaged_runtime_source_unstable",
-            ) from exc
+            last_error = exc
+            snapshot = None
+    raise EffectRuntimeStartupError(
+        "TypeScript Effect runtime source topology did not stabilize",
+        diagnostic_code="packaged_runtime_source_unstable",
+    ) from last_error
 
 
 @contextmanager

tests/control_plane/test_turn_journal_runtime_readiness.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from pathlib import Path
+from threading import Event
 from typing import Any
 
 import pytest
@@ -104,7 +105,11 @@ def scan_then_remove(root: Path) -> tuple[str, ...]:
     monkeypatch.setattr(effect_runtime, "_control_plane_root", lambda: tmp_path)
 
     assert len(effect_runtime._runtime_fingerprint()) == 64
-    assert scans == [("kept.ts", "removed.ts"), ("kept.ts",)]
+    assert scans == [
+        ("kept.ts", "removed.ts"),
+        ("kept.ts",),
+        ("kept.ts",),
+    ]
 
 
 def test_runtime_fingerprint_rescans_when_a_snapshotted_file_disappears_while_reading(
@@ -117,19 +122,25 @@ def test_runtime_fingerprint_rescans_when_a_snapshotted_file_disappears_while_re
     later.write_text("export const later = true;\n", encoding="utf-8")
     original_read_bytes = Path.read_bytes
     reads: list[str] = []
+    later_prefetched = Event()
 
-    def remove_later_after_first_read(path: Path) -> bytes:
-        reads.append(path.name)
+    def remove_later_after_prefetch(path: Path) -> bytes:
         content = original_read_bytes(path)
-        if path == first and later.exists():
-            later.unlink()
+        if path == later:
+            reads.append(path.name)
+            later_prefetched.set()
+        else:
+            if later.exists():
+                assert later_prefetched.wait(timeout=5)
+                later.unlink()
+            reads.append(path.name)
         return content
 
     monkeypatch.setattr(effect_runtime, "_control_plane_root", lambda: tmp_path)
-    monkeypatch.setattr(Path, "read_bytes", remove_later_after_first_read)
+    monkeypatch.setattr(Path, "read_bytes", remove_later_after_prefetch)
 
     assert len(effect_runtime._runtime_fingerprint()) == 64
-    assert reads == ["first.ts", "later.ts", "first.ts"]
+    assert reads == ["later.ts", "first.ts", "first.ts"]
 
 
 def _install_persistent_stat_read_churn(
@@ -139,25 +150,35 @@ def _install_persistent_stat_read_churn(
     first = tmp_path / "first.ts"
     later = tmp_path / "later.ts"
     first.write_text("export const first = true;\n", encoding="utf-8")
+    later.write_text("export const later = true;\n", encoding="utf-8")
     original_scan = effect_runtime._scan_runtime_source_files
     original_read_bytes = Path.read_bytes
     scans: list[tuple[str, ...]] = []
+    later_prefetched = Event()
+    first_reads = 0
 
-    def restore_then_scan(root: Path) -> tuple[str, ...]:
-        later.write_text("export const later = true;\n", encoding="utf-8")
+    def record_scan(root: Path) -> tuple[str, ...]:
         files = original_scan(root)
         scans.append(files)
         return files
 
-    def remove_later_after_first_read(path: Path) -> bytes:
+    def churn_after_each_first_read(path: Path) -> bytes:
+        nonlocal first_reads
         content = original_read_bytes(path)
-        if path == first:
+        if path == later:
+            later_prefetched.set()
+        else:
+            first_reads += 1
+        if first_reads == 1 and path == first:
+            assert later_prefetched.wait(timeout=5)
             later.unlink()
+        elif first_reads == 2 and path == first:
+            later.write_text("export const later = true;\n", encoding="utf-8")
         return content
 
     monkeypatch.setattr(effect_runtime, "_control_plane_root", lambda: tmp_path)
-    monkeypatch.setattr(effect_runtime, "_scan_runtime_source_files", restore_then_scan)
-    monkeypatch.setattr(Path, "read_bytes", remove_later_after_first_read)
+    monkeypatch.setattr(effect_runtime, "_scan_runtime_source_files", record_scan)
+    monkeypatch.setattr(Path, "read_bytes", churn_after_each_first_read)
     return scans
 
 
@@ -180,7 +201,11 @@ def test_runtime_source_churn_has_a_stable_readiness_diagnostic(
         result["runtime_lifecycle"]["diagnostic_code"]
         == "packaged_runtime_source_unstable"
     )
-    assert scans == [("first.ts", "later.ts"), ("first.ts", "later.ts")]
+    assert scans == [
+        ("first.ts", "later.ts"),
+        ("first.ts",),
+        ("first.ts", "later.ts"),
+    ]
 
 
 def test_runtime_request_source_churn_raises_a_stable_startup_diagnostic(
@@ -193,7 +218,11 @@ def test_runtime_request_source_churn_raises_a_stable_startup_diagnostic(
         effect_runtime.effect_runtime_request("runtime.ping", {})
 
     assert error.value.diagnostic_code == "packaged_runtime_source_unstable"
-    assert scans == [("first.ts", "later.ts"), ("first.ts", "later.ts")]
+    assert scans == [
+        ("first.ts", "later.ts"),
+        ("first.ts",),
+        ("first.ts", "later.ts"),
+    ]
 
 
 def test_missing_node_blocks_the_typescript_control_plane_and_is_actionable(