diff --git a/CLAUDE.md b/CLAUDE.md
index 5b2f401..ad9df87 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -113,10 +113,10 @@ src/deltaglider/
 
 ### Core Concepts
 
-1. **Leaf**: A prefix in S3 where related files are stored. Contains a `reference.bin` file that serves as the base for delta compression.
+1. **DeltaSpace**: A prefix in S3 where related files are stored for delta compression. Contains a `reference.bin` file that serves as the base for delta compression.
 
 2. **Delta Compression Flow**:
-   - First file uploaded to a Leaf becomes the reference (stored as `reference.bin`)
+   - First file uploaded to a DeltaSpace becomes the reference (stored as `reference.bin`)
    - Subsequent files are compared against the reference using xdelta3
    - Only the differences (delta) are stored with `.delta` suffix
    - Metadata in S3 tags preserves original file info and delta relationships
@@ -199,7 +199,7 @@ Core delta logic is in `src/deltaglider/core/service.py`:
 
 4. **Atomic Operations**: All S3 operations are atomic - no partial states are left if operations fail.
 
-5. **Reference File Updates**: Currently, the first file uploaded to a Leaf becomes the permanent reference. Future versions may implement reference rotation.
+5. **Reference File Updates**: Currently, the first file uploaded to a DeltaSpace becomes the permanent reference. Future versions may implement reference rotation.
 
 ## Performance Considerations
 
diff --git a/README.md b/README.md
index 8fdb714..39ff7e4 100644
--- a/README.md
+++ b/README.md
@@ -196,7 +196,7 @@ deltaglider rm -r s3://backups/2023/
 
 ```python
 from pathlib import Path
-from deltaglider.core import DeltaService, Leaf, ObjectKey
+from deltaglider.core import DeltaService, DeltaSpace, ObjectKey
 from deltaglider.adapters import (
     S3StorageAdapter,
     XdeltaAdapter,
@@ -261,8 +261,8 @@ def create_service(
 service = create_service()
 
 # Upload a file with automatic delta compression
-leaf = Leaf(bucket="my-releases", prefix="v2.0.0")
-summary = service.put(Path("my-app-v2.0.0.zip"), leaf)
+delta_space = DeltaSpace(bucket="my-releases", prefix="v2.0.0")
+summary = service.put(Path("my-app-v2.0.0.zip"), delta_space)
 
 print(f"Operation: {summary.operation}")  # 'create_reference' or 'create_delta'
 print(f"Stored at: s3://{summary.bucket}/{summary.key}")
diff --git a/docs/deltaglider_architecture_guidelines.txt b/docs/deltaglider_architecture_guidelines.txt
index 9c5bdeb..c51f557 100644
--- a/docs/deltaglider_architecture_guidelines.txt
+++ b/docs/deltaglider_architecture_guidelines.txt
@@ -42,21 +42,21 @@ interface DiffPort {
 interface HashPort { sha256(pathOrStream) -> Sha256 }
 
 interface CachePort {
-  refPath(bucket, leaf) -> Path
-  hasRef(bucket, leaf, sha) -> Bool
-  writeRef(bucket, leaf, src) -> Path
-  evict(bucket, leaf)
+  refPath(bucket, prefix) -> Path
+  hasRef(bucket, prefix, sha) -> Bool
+  writeRef(bucket, prefix, src) -> Path
+  evict(bucket, prefix)
 }
 
 interface DeltaService {
-  put(localFile, leaf, maxRatio) -> PutSummary
+  put(localFile, deltaSpace, maxRatio) -> PutSummary
   get(deltaKey, out) -> void
   verify(deltaKey) -> VerifyResult
 }
 
 4. Domain Use-Cases
 -------------------
-put(localFile, leaf):
+put(localFile, deltaSpace):
 - If no reference.bin: upload as reference, cache, create zero-diff delta.
 - Else: ensure cached reference valid, generate delta, upload with metadata.
 
@@ -69,7 +69,7 @@ verify(deltaKey):
 
 5. Object Model
 ---------------
-- Leaf { bucket, prefix }
+- DeltaSpace { bucket, prefix }
 - ObjectKey { bucket, key }
 - Sha256 { hex }
 - DeltaMeta { tool, original_name, file_sha256, file_size, created_at, ref_key, ref_sha256, delta_size, note? }
diff --git a/docs/deltaglider_metadata_schema.txt b/docs/deltaglider_metadata_schema.txt
index 8ef41a4..52738bd 100644
--- a/docs/deltaglider_metadata_schema.txt
+++ b/docs/deltaglider_metadata_schema.txt
@@ -12,7 +12,7 @@ General Rules
 
 Reference Object (`reference.bin`)
 ---------------------------------
-Stored once per leaf prefix.
+Stored once per DeltaSpace prefix.
 
 Required keys:
 - tool: deltaglider/0.1.0
@@ -31,7 +31,7 @@ Required keys:
 - file_sha256: SHA256 of hydrated file
 - file_size: size in bytes of hydrated file
 - created_at: ISO8601 UTC timestamp
-- ref_key: key of reference file (e.g. path/to/leaf/reference.bin)
+- ref_key: key of reference file (e.g. path/to/delta_space/reference.bin)
 - ref_sha256: SHA256 of reference file
 - delta_size: size in bytes of delta file
 - delta_cmd: "xdelta3 -e -9 -s reference.bin <file> <file>.delta"
diff --git a/docs/deltaglider_specs.txt b/docs/deltaglider_specs.txt
index 6316f76..15b6472 100644
--- a/docs/deltaglider_specs.txt
+++ b/docs/deltaglider_specs.txt
@@ -12,14 +12,14 @@ The cost of storing large binary artifacts (e.g., ZIP plugins, deliverables) on
 by only a few kilobytes. Current practice redundantly uploads full versions, wasting space and increasing transfer times.
 
 deltaglider is a CLI tool that transparently reduces storage overhead by representing a directory of similar large files as:
-- A single reference file (reference.bin) in each leaf S3 prefix.
+- A single reference file (reference.bin) in each DeltaSpace S3 prefix.
 - A set of delta files (<original>.delta) encoding differences against the reference.
 
 This approach compresses storage usage to near-optimal while retaining simple semantics.
 
 Goals
 -----
-1. Save S3 space by storing only one full copy of similar files per leaf and small binary deltas for subsequent versions.
+1. Save S3 space by storing only one full copy of similar files per DeltaSpace and small binary deltas for subsequent versions.
 2. Transparent developer workflow – deltaglider put/get mirrors aws s3 cp.
 3. Minimal state management – no manifests, no external databases.
 4. Integrity assurance – strong hashing (SHA256) stored in metadata, verified on upload/restore.
@@ -28,19 +28,19 @@ Goals
 Non-Goals
 ---------
 - Deduplication across multiple directories/prefixes.
-- Streaming delta generation across multiple references (always one reference per leaf).
+- Streaming delta generation across multiple references (always one reference per DeltaSpace).
 - Automatic background compaction or garbage collection.
 
 Terminology
 -----------
-- Leaf prefix: An S3 "directory" containing only files, no further sub-prefixes.
-- Reference file: The first uploaded file in a leaf, stored as reference.bin.
+- DeltaSpace: An S3 prefix containing related files for delta compression.
+- Reference file: The first uploaded file in a DeltaSpace, stored as reference.bin.
 - Delta file: Result of running xdelta3 against the reference, named <original>.delta.
 
 Architecture
 ------------
 Reference Selection
-- First uploaded file in a leaf becomes the reference.
+- First uploaded file in a DeltaSpace becomes the reference.
 - Stored as reference.bin.
 - Original filename preserved in metadata of both reference.bin and zero-diff delta.
 
@@ -68,7 +68,7 @@ Local Cache
 
 CLI Specification
 -----------------
-deltaglider put <file> <s3://bucket/path/to/leaf/>
+deltaglider put <file> <s3://bucket/path/to/delta_space/>
 - If no reference.bin: upload <file> as reference.bin, upload zero-diff <file>.delta.
 - If reference.bin exists: create delta, upload <file>.delta with metadata.
 - Output JSON summary.
diff --git a/src/deltaglider/adapters/cache_fs.py b/src/deltaglider/adapters/cache_fs.py
index d6fdb2e..a0c2a05 100644
--- a/src/deltaglider/adapters/cache_fs.py
+++ b/src/deltaglider/adapters/cache_fs.py
@@ -15,30 +15,30 @@ class FsCacheAdapter(CachePort):
         self.base_dir = base_dir
         self.hasher = hasher
 
-    def ref_path(self, bucket: str, leaf: str) -> Path:
+    def ref_path(self, bucket: str, prefix: str) -> Path:
         """Get path where reference should be cached."""
-        cache_dir = self.base_dir / bucket / leaf
+        cache_dir = self.base_dir / bucket / prefix
         return cache_dir / "reference.bin"
 
-    def has_ref(self, bucket: str, leaf: str, sha: str) -> bool:
+    def has_ref(self, bucket: str, prefix: str, sha: str) -> bool:
         """Check if reference exists and matches SHA."""
-        path = self.ref_path(bucket, leaf)
+        path = self.ref_path(bucket, prefix)
         if not path.exists():
             return False
 
         actual_sha = self.hasher.sha256(path)
         return actual_sha == sha
 
-    def write_ref(self, bucket: str, leaf: str, src: Path) -> Path:
+    def write_ref(self, bucket: str, prefix: str, src: Path) -> Path:
         """Cache reference file."""
-        path = self.ref_path(bucket, leaf)
+        path = self.ref_path(bucket, prefix)
         path.parent.mkdir(parents=True, exist_ok=True)
         shutil.copy2(src, path)
         return path
 
-    def evict(self, bucket: str, leaf: str) -> None:
+    def evict(self, bucket: str, prefix: str) -> None:
         """Remove cached reference."""
-        path = self.ref_path(bucket, leaf)
+        path = self.ref_path(bucket, prefix)
         if path.exists():
             path.unlink()
         # Clean up empty directories
diff --git a/src/deltaglider/app/cli/aws_compat.py b/src/deltaglider/app/cli/aws_compat.py
index 8273ebc..04b2dea 100644
--- a/src/deltaglider/app/cli/aws_compat.py
+++ b/src/deltaglider/app/cli/aws_compat.py
@@ -5,7 +5,7 @@ from pathlib import Path
 
 import click
 
-from ...core import DeltaService, Leaf, ObjectKey
+from ...core import DeltaService, DeltaSpace, ObjectKey
 
 
 def is_s3_path(path: str) -> bool:
@@ -55,7 +55,7 @@ def upload_file(
     if not key or key.endswith("/"):
         key = (key + local_path.name).lstrip("/")
 
-    leaf = Leaf(bucket=bucket, prefix="/".join(key.split("/")[:-1]))
+    delta_space = DeltaSpace(bucket=bucket, prefix="/".join(key.split("/")[:-1]))
 
     try:
         # Check if delta should be disabled
@@ -69,7 +69,7 @@ def upload_file(
                 click.echo(f"upload: '{local_path}' to 's3://{bucket}/{key}' ({file_size} bytes)")
         else:
             # Use delta compression
-            summary = service.put(local_path, leaf, max_ratio)
+            summary = service.put(local_path, delta_space, max_ratio)
 
             if not quiet:
                 if summary.delta_size:
diff --git a/src/deltaglider/app/cli/main.py b/src/deltaglider/app/cli/main.py
index 512f8a8..04df848 100644
--- a/src/deltaglider/app/cli/main.py
+++ b/src/deltaglider/app/cli/main.py
@@ -16,7 +16,7 @@ from ...adapters import (
     UtcClockAdapter,
     XdeltaAdapter,
 )
-from ...core import DeltaService, Leaf, ObjectKey
+from ...core import DeltaService, DeltaSpace, ObjectKey
 from .aws_compat import (
     copy_s3_to_s3,
     determine_operation,
@@ -537,10 +537,10 @@ def put(service: DeltaService, file: Path, s3_url: str, max_ratio: float | None)
     bucket = parts[0]
     prefix = parts[1] if len(parts) > 1 else ""
 
-    leaf = Leaf(bucket=bucket, prefix=prefix)
+    delta_space = DeltaSpace(bucket=bucket, prefix=prefix)
 
     try:
-        summary = service.put(file, leaf, max_ratio)
+        summary = service.put(file, delta_space, max_ratio)
 
         # Output JSON summary
         output = {
diff --git a/src/deltaglider/core/__init__.py b/src/deltaglider/core/__init__.py
index 9b5c10b..3c5166b 100644
--- a/src/deltaglider/core/__init__.py
+++ b/src/deltaglider/core/__init__.py
@@ -12,7 +12,7 @@ from .errors import (
 )
 from .models import (
     DeltaMeta,
-    Leaf,
+    DeltaSpace,
     ObjectKey,
     PutSummary,
     ReferenceMeta,
@@ -30,7 +30,7 @@ __all__ = [
     "DiffDecodeError",
     "StorageIOError",
     "PolicyViolationWarning",
-    "Leaf",
+    "DeltaSpace",
     "ObjectKey",
     "Sha256",
     "DeltaMeta",
diff --git a/src/deltaglider/core/models.py b/src/deltaglider/core/models.py
index 6c82d68..7f978ac 100644
--- a/src/deltaglider/core/models.py
+++ b/src/deltaglider/core/models.py
@@ -5,8 +5,8 @@ from datetime import datetime
 
 
 @dataclass(frozen=True)
-class Leaf:
-    """S3 leaf prefix."""
+class DeltaSpace:
+    """S3 delta compression space - a prefix containing related files for delta compression."""
 
     bucket: str
     prefix: str
diff --git a/src/deltaglider/core/service.py b/src/deltaglider/core/service.py
index 5ec179e..76f7f6d 100644
--- a/src/deltaglider/core/service.py
+++ b/src/deltaglider/core/service.py
@@ -25,7 +25,7 @@ from .errors import (
 )
 from .models import (
     DeltaMeta,
-    Leaf,
+    DeltaSpace,
     ObjectKey,
     PutSummary,
     ReferenceMeta,
@@ -93,7 +93,9 @@ class DeltaService:
         # Check simple extensions
         return any(name_lower.endswith(ext) for ext in self.delta_extensions)
 
-    def put(self, local_file: Path, leaf: Leaf, max_ratio: float | None = None) -> PutSummary:
+    def put(
+        self, local_file: Path, delta_space: DeltaSpace, max_ratio: float | None = None
+    ) -> PutSummary:
         """Upload file as reference or delta (for archive files) or directly (for other files)."""
         if max_ratio is None:
             max_ratio = self.max_ratio
@@ -106,7 +108,7 @@ class DeltaService:
         self.logger.info(
             "Starting put operation",
             file=str(local_file),
-            leaf=f"{leaf.bucket}/{leaf.prefix}",
+            leaf=f"{delta_space.bucket}/{delta_space.prefix}",
             size=file_size,
         )
 
@@ -119,23 +121,25 @@ class DeltaService:
                 "Uploading file directly (no delta for this type)",
                 file_type=Path(original_name).suffix,
             )
-            summary = self._upload_direct(local_file, leaf, file_sha256, original_name, file_size)
+            summary = self._upload_direct(
+                local_file, delta_space, file_sha256, original_name, file_size
+            )
         else:
             # For archive files, use the delta compression system
             # Check for existing reference
-            ref_key = leaf.reference_key()
-            ref_head = self.storage.head(f"{leaf.bucket}/{ref_key}")
+            ref_key = delta_space.reference_key()
+            ref_head = self.storage.head(f"{delta_space.bucket}/{ref_key}")
 
             if ref_head is None:
                 # Create reference
                 summary = self._create_reference(
-                    local_file, leaf, file_sha256, original_name, file_size
+                    local_file, delta_space, file_sha256, original_name, file_size
                 )
             else:
                 # Create delta
                 summary = self._create_delta(
                     local_file,
-                    leaf,
+                    delta_space,
                     ref_head,
                     file_sha256,
                     original_name,
@@ -147,7 +151,7 @@ class DeltaService:
         self.logger.log_operation(
             op="put",
             key=summary.key,
-            leaf=f"{leaf.bucket}/{leaf.prefix}",
+            leaf=f"{delta_space.bucket}/{delta_space.prefix}",
             sizes={"file": file_size, "delta": summary.delta_size or file_size},
             durations={"total": duration},
             cache_hit=summary.cache_hit,
@@ -197,17 +201,19 @@ class DeltaService:
             leaf_prefix = "/".join(ref_parts[:-1])
         else:
             leaf_prefix = ""
-        leaf = Leaf(bucket=object_key.bucket, prefix=leaf_prefix)
+        delta_space = DeltaSpace(bucket=object_key.bucket, prefix=leaf_prefix)
 
-        cache_hit = self.cache.has_ref(leaf.bucket, leaf.prefix, delta_meta.ref_sha256)
+        cache_hit = self.cache.has_ref(
+            delta_space.bucket, delta_space.prefix, delta_meta.ref_sha256
+        )
         if not cache_hit:
-            self._cache_reference(leaf, delta_meta.ref_sha256)
+            self._cache_reference(delta_space, delta_meta.ref_sha256)
 
         # Download delta and decode
         with tempfile.TemporaryDirectory() as tmpdir:
             tmp_path = Path(tmpdir)
             delta_path = tmp_path / "delta"
-            ref_path = self.cache.ref_path(leaf.bucket, leaf.prefix)
+            ref_path = self.cache.ref_path(delta_space.bucket, delta_space.prefix)
             out_path = tmp_path / "output"
 
             # Download delta
@@ -241,7 +247,7 @@ class DeltaService:
         self.logger.log_operation(
             op="get",
             key=object_key.key,
-            leaf=f"{leaf.bucket}/{leaf.prefix}",
+            leaf=f"{delta_space.bucket}/{delta_space.prefix}",
             sizes={"delta": delta_meta.delta_size, "file": delta_meta.file_size},
             durations={"total": duration},
             cache_hit=cache_hit,
@@ -285,14 +291,14 @@ class DeltaService:
     def _create_reference(
         self,
         local_file: Path,
-        leaf: Leaf,
+        delta_space: DeltaSpace,
         file_sha256: str,
         original_name: str,
         file_size: int,
     ) -> PutSummary:
         """Create reference file."""
-        ref_key = leaf.reference_key()
-        full_ref_key = f"{leaf.bucket}/{ref_key}"
+        ref_key = delta_space.reference_key()
+        full_ref_key = f"{delta_space.bucket}/{ref_key}"
 
         # Create reference metadata
         ref_meta = ReferenceMeta(
@@ -320,14 +326,16 @@ class DeltaService:
             ref_sha256 = file_sha256
 
         # Cache reference
-        cached_path = self.cache.write_ref(leaf.bucket, leaf.prefix, local_file)
+        cached_path = self.cache.write_ref(delta_space.bucket, delta_space.prefix, local_file)
         self.logger.debug("Cached reference", path=str(cached_path))
 
         # Also create zero-diff delta
         delta_key = (
-            f"{leaf.prefix}/{original_name}.delta" if leaf.prefix else f"{original_name}.delta"
+            f"{delta_space.prefix}/{original_name}.delta"
+            if delta_space.prefix
+            else f"{original_name}.delta"
         )
-        full_delta_key = f"{leaf.bucket}/{delta_key}"
+        full_delta_key = f"{delta_space.bucket}/{delta_key}"
 
         with tempfile.NamedTemporaryFile() as zero_delta:
             # Create empty delta using xdelta3
@@ -357,7 +365,7 @@ class DeltaService:
         self.metrics.increment("deltaglider.reference.created")
         return PutSummary(
             operation="create_reference",
-            bucket=leaf.bucket,
+            bucket=delta_space.bucket,
             key=ref_key,
             original_name=original_name,
             file_size=file_size,
@@ -367,7 +375,7 @@ class DeltaService:
     def _create_delta(
         self,
         local_file: Path,
-        leaf: Leaf,
+        delta_space: DeltaSpace,
         ref_head: ObjectHead,
         file_sha256: str,
         original_name: str,
@@ -375,15 +383,15 @@ class DeltaService:
         max_ratio: float,
     ) -> PutSummary:
         """Create delta file."""
-        ref_key = leaf.reference_key()
+        ref_key = delta_space.reference_key()
         ref_sha256 = ref_head.metadata["file_sha256"]
 
         # Ensure reference is cached
-        cache_hit = self.cache.has_ref(leaf.bucket, leaf.prefix, ref_sha256)
+        cache_hit = self.cache.has_ref(delta_space.bucket, delta_space.prefix, ref_sha256)
         if not cache_hit:
-            self._cache_reference(leaf, ref_sha256)
+            self._cache_reference(delta_space, ref_sha256)
 
-        ref_path = self.cache.ref_path(leaf.bucket, leaf.prefix)
+        ref_path = self.cache.ref_path(delta_space.bucket, delta_space.prefix)
 
         # Create delta
         with tempfile.NamedTemporaryFile(suffix=".delta") as delta_file:
@@ -412,9 +420,11 @@ class DeltaService:
 
             # Create delta metadata
             delta_key = (
-                f"{leaf.prefix}/{original_name}.delta" if leaf.prefix else f"{original_name}.delta"
+                f"{delta_space.prefix}/{original_name}.delta"
+                if delta_space.prefix
+                else f"{original_name}.delta"
             )
-            full_delta_key = f"{leaf.bucket}/{delta_key}"
+            full_delta_key = f"{delta_space.bucket}/{delta_key}"
 
             delta_meta = DeltaMeta(
                 tool=self.tool_version,
@@ -445,7 +455,7 @@ class DeltaService:
 
         return PutSummary(
             operation="create_delta",
-            bucket=leaf.bucket,
+            bucket=delta_space.bucket,
             key=delta_key,
             original_name=original_name,
             file_size=file_size,
@@ -457,10 +467,10 @@ class DeltaService:
             cache_hit=cache_hit,
         )
 
-    def _cache_reference(self, leaf: Leaf, expected_sha: str) -> None:
+    def _cache_reference(self, delta_space: DeltaSpace, expected_sha: str) -> None:
         """Download and cache reference."""
-        ref_key = leaf.reference_key()
-        full_ref_key = f"{leaf.bucket}/{ref_key}"
+        ref_key = delta_space.reference_key()
+        full_ref_key = f"{delta_space.bucket}/{ref_key}"
 
         self.logger.info("Caching reference", key=ref_key)
 
@@ -482,7 +492,7 @@ class DeltaService:
             )
 
         # Cache it
-        self.cache.write_ref(leaf.bucket, leaf.prefix, tmp_path)
+        self.cache.write_ref(delta_space.bucket, delta_space.prefix, tmp_path)
         tmp_path.unlink()
 
     def _get_direct(
@@ -533,18 +543,18 @@ class DeltaService:
     def _upload_direct(
         self,
         local_file: Path,
-        leaf: Leaf,
+        delta_space: DeltaSpace,
         file_sha256: str,
         original_name: str,
         file_size: int,
     ) -> PutSummary:
         """Upload file directly to S3 without delta compression."""
         # Construct the key path
-        if leaf.prefix:
-            key = f"{leaf.prefix}/{original_name}"
+        if delta_space.prefix:
+            key = f"{delta_space.prefix}/{original_name}"
         else:
             key = original_name
-        full_key = f"{leaf.bucket}/{key}"
+        full_key = f"{delta_space.bucket}/{key}"
 
         # Create metadata for the file
         metadata = {
@@ -568,7 +578,7 @@ class DeltaService:
 
         return PutSummary(
             operation="upload_direct",
-            bucket=leaf.bucket,
+            bucket=delta_space.bucket,
             key=key,
             original_name=original_name,
             file_size=file_size,
diff --git a/src/deltaglider/ports/cache.py b/src/deltaglider/ports/cache.py
index 1f32080..bd76395 100644
--- a/src/deltaglider/ports/cache.py
+++ b/src/deltaglider/ports/cache.py
@@ -7,18 +7,18 @@ from typing import Protocol
 class CachePort(Protocol):
     """Port for cache operations."""
 
-    def ref_path(self, bucket: str, leaf: str) -> Path:
+    def ref_path(self, bucket: str, prefix: str) -> Path:
         """Get path where reference should be cached."""
         ...
 
-    def has_ref(self, bucket: str, leaf: str, sha: str) -> bool:
+    def has_ref(self, bucket: str, prefix: str, sha: str) -> bool:
         """Check if reference exists and matches SHA."""
         ...
 
-    def write_ref(self, bucket: str, leaf: str, src: Path) -> Path:
+    def write_ref(self, bucket: str, prefix: str, src: Path) -> Path:
         """Cache reference file."""
         ...
 
-    def evict(self, bucket: str, leaf: str) -> None:
+    def evict(self, bucket: str, prefix: str) -> None:
         """Remove cached reference."""
         ...
diff --git a/tests/integration/test_full_workflow.py b/tests/integration/test_full_workflow.py
index 20d9150..e23409c 100644
--- a/tests/integration/test_full_workflow.py
+++ b/tests/integration/test_full_workflow.py
@@ -3,7 +3,7 @@
 import io
 from pathlib import Path
 
-from deltaglider.core import Leaf, ObjectKey
+from deltaglider.core import DeltaSpace, ObjectKey
 
 
 def test_full_put_get_workflow(service, temp_dir, mock_storage, mock_diff):
@@ -25,7 +25,7 @@ def test_full_put_get_workflow(service, temp_dir, mock_storage, mock_diff):
 
     mock_diff.decode.side_effect = decode_side_effect
 
-    leaf = Leaf(bucket="test-bucket", prefix="test/data")
+    delta_space = DeltaSpace(bucket="test-bucket", prefix="test/data")
 
     # Storage state tracking
     storage_data = {}
@@ -76,28 +76,28 @@ def test_full_put_get_workflow(service, temp_dir, mock_storage, mock_diff):
     mock_storage.get.side_effect = mock_get
 
     # Step 1: Put the first file (creates reference)
-    summary1 = service.put(file1, leaf)
+    summary1 = service.put(file1, delta_space)
     assert summary1.operation == "create_reference"
     assert summary1.key == "test/data/reference.bin"
 
     # Verify reference was stored
-    ref_key = f"{leaf.bucket}/{leaf.reference_key()}"
+    ref_key = f"{delta_space.bucket}/{delta_space.reference_key()}"
     assert ref_key in storage_data
     assert storage_data[ref_key]["content"] == file1_content
 
     # Step 2: Put the second file (creates delta)
-    summary2 = service.put(file2, leaf)
+    summary2 = service.put(file2, delta_space)
     assert summary2.operation == "create_delta"
     assert summary2.key == "test/data/version2.zip.delta"
     assert summary2.delta_size is not None
     assert summary2.ref_key == "test/data/reference.bin"
 
     # Verify delta was stored
-    delta_key = f"{leaf.bucket}/{summary2.key}"
+    delta_key = f"{delta_space.bucket}/{summary2.key}"
     assert delta_key in storage_data
 
     # Step 3: Get the delta file back
-    obj_key = ObjectKey(bucket=leaf.bucket, key=summary2.key)
+    obj_key = ObjectKey(bucket=delta_space.bucket, key=summary2.key)
     service.get(obj_key, output_file)
 
     # Step 4: Verify the recovered file matches the original
@@ -118,7 +118,7 @@ def test_get_with_auto_delta_suffix(service, temp_dir, mock_storage, mock_diff):
 
     mock_diff.decode.side_effect = decode_side_effect
 
-    leaf = Leaf(bucket="test-bucket", prefix="archive")
+    delta_space = DeltaSpace(bucket="test-bucket", prefix="archive")
 
     # Storage state tracking
     storage_data = {}
@@ -169,7 +169,7 @@ def test_get_with_auto_delta_suffix(service, temp_dir, mock_storage, mock_diff):
     mock_storage.get.side_effect = mock_get
 
     # Put the file
-    summary = service.put(test_file, leaf)
+    summary = service.put(test_file, delta_space)
 
     # Get it back using original name (without .delta)
     # The service should internally look for "mydata.zip.delta"
@@ -178,9 +178,9 @@ def test_get_with_auto_delta_suffix(service, temp_dir, mock_storage, mock_diff):
     # Use the key without .delta suffix
     if summary.operation == "create_reference":
         # If it's a reference, the zero-diff delta was created
-        obj_key = ObjectKey(bucket=leaf.bucket, key="archive/mydata.zip.delta")
+        obj_key = ObjectKey(bucket=delta_space.bucket, key="archive/mydata.zip.delta")
     else:
-        obj_key = ObjectKey(bucket=leaf.bucket, key=summary.key)
+        obj_key = ObjectKey(bucket=delta_space.bucket, key=summary.key)
 
     service.get(obj_key, output_file)
 
diff --git a/tests/unit/test_core_service.py b/tests/unit/test_core_service.py
index 2ec93ac..81d064a 100644
--- a/tests/unit/test_core_service.py
+++ b/tests/unit/test_core_service.py
@@ -5,7 +5,7 @@ import warnings
 import pytest
 
 from deltaglider.core import (
-    Leaf,
+    DeltaSpace,
     NotFoundError,
     ObjectKey,
     PolicyViolationWarning,
@@ -19,12 +19,12 @@ class TestDeltaServicePut:
     def test_create_reference_first_file(self, service, sample_file, mock_storage):
         """Test creating reference for first file."""
         # Setup
-        leaf = Leaf(bucket="test-bucket", prefix="test/prefix")
+        delta_space = DeltaSpace(bucket="test-bucket", prefix="test/prefix")
         mock_storage.head.return_value = None  # No reference exists
         mock_storage.put.return_value = PutResult(etag="abc123")
 
         # Execute
-        summary = service.put(sample_file, leaf)
+        summary = service.put(sample_file, delta_space)
 
         # Verify
         assert summary.operation == "create_reference"
@@ -41,7 +41,7 @@ class TestDeltaServicePut:
     def test_create_delta_subsequent_file(self, service, sample_file, mock_storage, mock_diff):
         """Test creating delta for subsequent file."""
         # Setup
-        leaf = Leaf(bucket="test-bucket", prefix="test/prefix")
+        delta_space = DeltaSpace(bucket="test-bucket", prefix="test/prefix")
 
         # Create reference content and compute its SHA
         import io
@@ -68,12 +68,12 @@ class TestDeltaServicePut:
         mock_storage.get.return_value = io.BytesIO(ref_content)
 
         # Create cached reference with matching content
-        ref_path = service.cache.ref_path(leaf.bucket, leaf.prefix)
+        ref_path = service.cache.ref_path(delta_space.bucket, delta_space.prefix)
         ref_path.parent.mkdir(parents=True, exist_ok=True)
         ref_path.write_bytes(ref_content)
 
         # Execute
-        summary = service.put(sample_file, leaf)
+        summary = service.put(sample_file, delta_space)
 
         # Verify
         assert summary.operation == "create_delta"
@@ -89,7 +89,7 @@ class TestDeltaServicePut:
     def test_delta_ratio_warning(self, service, sample_file, mock_storage, mock_diff):
         """Test warning when delta ratio exceeds threshold."""
         # Setup
-        leaf = Leaf(bucket="test-bucket", prefix="test/prefix")
+        delta_space = DeltaSpace(bucket="test-bucket", prefix="test/prefix")
 
         # Create reference content and compute its SHA
         import io
@@ -119,14 +119,14 @@ class TestDeltaServicePut:
         mock_diff.encode.side_effect = large_encode
 
         # Create cached reference with matching content
-        ref_path = service.cache.ref_path(leaf.bucket, leaf.prefix)
+        ref_path = service.cache.ref_path(delta_space.bucket, delta_space.prefix)
         ref_path.parent.mkdir(parents=True, exist_ok=True)
         ref_path.write_bytes(ref_content)
 
         # Execute and check warning
         with warnings.catch_warnings(record=True) as w:
             warnings.simplefilter("always")
-            service.put(sample_file, leaf, max_ratio=0.1)
+            service.put(sample_file, delta_space, max_ratio=0.1)
 
             assert len(w) == 1
             assert issubclass(w[0].category, PolicyViolationWarning)