diff --git a/README.md b/README.md
index 4112a2c..cb5b2cd 100644
--- a/README.md
+++ b/README.md
@@ -96,8 +96,10 @@ Canonical output supports local unstaged (`index` → working tree), staged
 (`HEAD` → index), explicit two-dot (`BASE..HEAD`), and explicit three-dot
 (`BASE...HEAD`) comparisons. Two-dot resolves both refs to immutable commits;
 three-dot resolves their merge base and compares it with the immutable head,
-matching Git diff semantics. The artifact records those exact comparison OIDs
-and every file's pre/post blob identities. Invalid refs and unavailable merge
+matching Git diff semantics. For commit ranges, `diff_ref` records both the
+user-requested base/head refs (`requested_base_ref`, `requested_head_ref`) and
+the resolved immutable comparison endpoints (`base_ref`, `head_ref`), plus
+`comparison_mode`; every file records its pre/post blob identities. Invalid refs and unavailable merge
 bases produce structured warnings instead of false changes.
 
 Put pathspecs after `--`. Pathspecs are interpreted relative to the directory
diff --git a/diffgraph/schema/diffgraph-v2.schema.json b/diffgraph/schema/diffgraph-v2.schema.json
index 1802327..4d89a0d 100644
--- a/diffgraph/schema/diffgraph-v2.schema.json
+++ b/diffgraph/schema/diffgraph-v2.schema.json
@@ -41,11 +41,24 @@
         },
         "base_ref": {
           "type": ["string", "null"],
-          "description": "Commit SHA or ref for the base side. null for working-tree diffs."
+          "description": "Resolved comparison-base commit object ID; for three_dot ranges this is the resolved merge base. null for working-tree diffs."
         },
         "head_ref": {
           "type": ["string", "null"],
-          "description": "Commit SHA or ref for the head side. null for working-tree diffs."
+          "description": "Immutable commit object ID for the head side. null for working-tree diffs."
+        },
+        "requested_base_ref": {
+          "type": ["string", "null"],
+          "description": "User-supplied base ref before immutable resolution. null for working-tree diffs."
+        },
+        "requested_head_ref": {
+          "type": ["string", "null"],
+          "description": "User-supplied head ref before immutable resolution. null for working-tree diffs."
+        },
+        "comparison_mode": {
+          "type": ["string", "null"],
+          "enum": ["two_dot", "three_dot", null],
+          "description": "Commit-range semantics. three_dot uses the resolved merge-base in base_ref. null for working-tree diffs."
         },
         "pathspecs": {
           "type": "array",
diff --git a/diffgraph/structural.py b/diffgraph/structural.py
index 2fef866..6b5c32f 100644
--- a/diffgraph/structural.py
+++ b/diffgraph/structural.py
@@ -922,6 +922,11 @@ def analyze_local_diff(
                 resolution.comparison_base_oid if is_commit_range else "HEAD" if staged else None
             ),
             "head_ref": resolution.head_oid if is_commit_range else None,
+            "requested_base_ref": resolution.base_ref if is_commit_range else None,
+            "requested_head_ref": resolution.head_ref if is_commit_range else None,
+            "comparison_mode": (
+                ("three_dot" if three_dot else "two_dot") if is_commit_range else None
+            ),
             "pathspecs": list(pathspecs or []), "repo_root": root,
         },
         "files": files, "symbols": symbols, "relationships": relationships,
diff --git a/tests/test_structural.py b/tests/test_structural.py
index 676f245..9fcf591 100644
--- a/tests/test_structural.py
+++ b/tests/test_structural.py
@@ -123,6 +123,22 @@ def test_unstaged_uses_index_to_worktree_exact_identity_and_is_stable(tmp_path):
     assert first["symbols"][0]["change_kind"] == "modified"
 
 
+@pytest.mark.parametrize("staged", [False, True])
+def test_worktree_diffs_do_not_record_commit_range_mode(tmp_path, staged):
+    root = repo(tmp_path)
+    write(root, "app.py", "def value():\n    return 1\n")
+    commit(root)
+    write(root, "app.py", "def value():\n    return 2\n")
+    if staged:
+        git(root, "add", "app.py")
+
+    artifact = analyze_local_diff(str(root), staged=staged, three_dot=True)
+
+    assert_valid(artifact)
+    assert artifact["diff_ref"]["kind"] == ("staged" if staged else "unstaged")
+    assert artifact["diff_ref"]["comparison_mode"] is None
+
+
 def test_untracked_python_is_an_exact_added_snapshot(tmp_path):
     root = repo(tmp_path)
     write(root, "tracked.txt", "baseline\n")
@@ -696,6 +712,9 @@ def test_cli_structural_json_resolves_immutable_two_dot_range(tmp_path, monkeypa
     assert artifact["diff_ref"]["kind"] == "commit_range"
     assert artifact["diff_ref"]["base_ref"] == base_oid
     assert artifact["diff_ref"]["head_ref"] == head_oid
+    assert artifact["diff_ref"]["requested_base_ref"] == "HEAD~1"
+    assert artifact["diff_ref"]["requested_head_ref"] == "HEAD"
+    assert artifact["diff_ref"]["comparison_mode"] == "two_dot"
     provenance = json.loads(artifact["files"][0]["evidence"][0]["detail"])
     assert provenance["old_oid"] == old_blob
     assert provenance["new_oid"] == new_blob
@@ -734,6 +753,9 @@ def test_cli_structural_json_three_dot_uses_merge_base_and_pathspec(tmp_path, mo
         "kind": "commit_range",
         "base_ref": merge_base_oid,
         "head_ref": head_oid,
+        "requested_base_ref": "left",
+        "requested_head_ref": "right",
+        "comparison_mode": "three_dot",
         "pathspecs": ["included.py"],
         "repo_root": str(root),
     }