fix: remove line collapsing (#1330)

Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>

agent/tools/add_finding.py

@@ -55,14 +55,21 @@ def add_finding(
             ``style``, ``flag``, etc.). Free-form; used for grouping in the UI.
         file: Repo-relative path of the file the finding refers to.
         description: Markdown body the user sees.
-        start_line: 1-based line in the new (post-PR) file to anchor the
-            comment to. Pick the single most relevant line — the call site,
-            the signature, or the line the issue is actually about. Omit
-            (with ``end_line``) for file-level findings.
-        end_line: Accepted for API compatibility, but findings are always
-            anchored to a single line (``start_line``). GitHub renders
-            multi-line ranges as walls of context that bury the comment, so
-            we collapse to one line for a cleaner comment.
+        start_line: 1-based line in the new (post-PR) file where the
+            relevant range begins. For a single-line finding, this is the
+            line the issue is about. For a multi-line finding, this is the
+            first line of the relevant range. Omit (with ``end_line``) for
+            file-level findings.
+        end_line: 1-based line where the relevant range ends. GitHub
+            anchors the inline comment at ``end_line`` and renders the
+            ``start_line..end_line`` span as the highlighted snippet, so
+            choose ``end_line`` as the *last* line that matters — typically
+            the line the comment is most directly about. For a single-line
+            finding, set ``end_line == start_line`` (or omit it). Prefer
+            the natural range of the issue over a single line: GitHub
+            shows context above ``end_line``, so a one-line anchor often
+            buries the issue under unrelated context. Defaults to
+            ``start_line`` when omitted.
         suggestion: Replacement text for ``start_line..end_line``. When set,
             the published GitHub comment includes a ```suggestion``` block so
             the user can click "Commit suggestion". **Only set this for small,
@@ -91,9 +98,6 @@ def add_finding(
     if start_line is not None and end_line is not None and end_line < start_line:
         return {"success": False, "error": "end_line must be >= start_line"}
 
-    if start_line is not None:
-        end_line = start_line
-
     config = get_config()
     configurable = config.get("configurable", {}) if isinstance(config, dict) else {}
     diff_line_set = configurable.get("diff_line_set") if isinstance(configurable, dict) else None

tests/test_reviewer_tools.py

@@ -98,7 +98,7 @@ def test_add_finding_persists_to_thread_metadata() -> None:
     assert persisted_thread == "tid-1"
     assert persisted["file"] == "foo.py"
     assert persisted["start_line"] == 11
-    assert persisted["end_line"] == 11
+    assert persisted["end_line"] == 12
     assert persisted["suggestion"] == "renamed = 1"
     assert persisted["status"] == "open"
     assert persisted["first_seen_sha"] == "sha-head"
@@ -197,8 +197,8 @@ def test_add_finding_keeps_short_suggestion() -> None:
     assert captured[0]["suggestion"] == short_suggestion
 
 
-def test_add_finding_always_collapses_to_single_line() -> None:
-    """Multi-line ranges are always collapsed to ``start_line``."""
+def test_add_finding_preserves_multi_line_range() -> None:
+    """Multi-line ranges are preserved end-to-end (no collapse to start_line)."""
     captured: list[Any] = []
 
     async def fake_append(thread_id: str, finding: Any) -> Any:
@@ -215,14 +215,14 @@ def test_add_finding_always_collapses_to_single_line() -> None:
             confidence="low",
             category="style",
             file="foo.py",
-            description="anchor on start_line",
+            description="span the relevant range",
             start_line=15,
             end_line=19,
         )
 
     assert result["success"] is True
     assert captured[0]["start_line"] == 15
-    assert captured[0]["end_line"] == 15
+    assert captured[0]["end_line"] == 19
 
 
 def test_update_finding_rejects_long_suggestion_without_clobbering() -> None: