fix(pool): keep label key and value identities distinct

sandboxes/pool.py

@@ -88,7 +88,7 @@ def __init__(self, pool_config: PoolConfig | None = None):
         self._busy_sandboxes: set[str] = set()
 
         # Label index for fast lookup
-        self._label_index: dict[str, set[str]] = {}
+        self._label_index: dict[tuple[str, str], set[str]] = {}
 
         # Locks for thread-safe operations
         self._lock = asyncio.Lock()
@@ -288,7 +288,7 @@ async def _create_sandbox(self, provider: Any, config: SandboxConfig) -> Sandbox
 
         # Update label index
         for key, value in entry.labels.items():
-            label_key = f"{key}:{value}"
+            label_key = (key, value)
             if label_key not in self._label_index:
                 self._label_index[label_key] = set()
             self._label_index[label_key].add(sandbox.id)
@@ -304,7 +304,7 @@ async def _create_sandbox(self, provider: Any, config: SandboxConfig) -> Sandbox
     async def _find_reusable_sandbox(self, labels: dict[str, str]) -> Sandbox | None:
         """Find an idle sandbox with matching labels."""
         # Build label keys
-        label_keys = [f"{k}:{v}" for k, v in labels.items()]
+        label_keys = list(labels.items())
 
         # Find sandboxes with all matching labels
         matching_ids = None
@@ -333,7 +333,7 @@ async def find_by_labels(self, labels: dict[str, str]) -> list[Sandbox]:
             return []
 
         async with self._lock:
-            label_keys = [f"{k}:{v}" for k, v in labels.items()]
+            label_keys = list(labels.items())
             matching_ids: set[str] | None = None
 
             for label_key in label_keys:
@@ -435,7 +435,7 @@ def _remove_from_pool_locked(self, sandbox_id: str) -> SandboxPoolEntry | None:
         entry = self._pool.pop(sandbox_id)
 
         for key, value in entry.labels.items():
-            label_key = f"{key}:{value}"
+            label_key = (key, value)
             if label_key in self._label_index:
                 self._label_index[label_key].discard(sandbox_id)
                 if not self._label_index[label_key]:

tests/test_pool_label_keys.py

@@ -0,0 +1,25 @@
+import pytest
+
+from sandboxes.base import SandboxConfig
+from sandboxes.pool import PoolConfig, SandboxPool
+from tests.test_pool import MockProvider
+
+
+@pytest.mark.asyncio
+async def test_colons_do_not_collapse_distinct_label_pairs():
+    provider = MockProvider()
+    pool = SandboxPool(PoolConfig(auto_cleanup=False))
+    try:
+        first = await pool.acquire(provider, SandboxConfig(labels={"scope:project": "a"}))
+        await pool.release(first.id)
+        assert await pool.find_by_labels({"scope": "project:a"}) == []
+        second = await pool.acquire(provider, SandboxConfig(labels={"scope": "project:a"}))
+        assert second.id != first.id
+        assert [sandbox.id for sandbox in await pool.find_by_labels({"scope:project": "a"})] == [
+            first.id
+        ]
+        assert [sandbox.id for sandbox in await pool.find_by_labels({"scope": "project:a"})] == [
+            second.id
+        ]
+    finally:
+        await pool.stop()