fix(work): preserve blank context throughout attempt diffs

server/unified_diff.py

@@ -137,8 +137,14 @@ def append_file(old_path: str = "", new_path: str = "") -> dict[str, Any] | None
             current_file["hunks"].append(current_hunk)
             continue
 
-        if current_hunk is None or not raw_line:
+        if current_hunk is None:
             continue
+        if not raw_line:
+            if not in_hunk_body:
+                continue
+            # diff.suppressBlankEmpty (and GNU diff) write a blank context
+            # line without its leading space. Git apply reads it as context.
+            raw_line = " "
         prefix = raw_line[0]
         if prefix not in {" ", "+", "-", "\\"}:
             continue

server/work_artifact_registry.py

@@ -472,7 +472,7 @@ async def collect_git_delta(
         "conflicts": conflicts,
         "truncated_paths": truncated_paths,
         "patch": "\n".join(
-            part.rstrip("\n")
+            part.removesuffix("\n")
             for part in (committed_patch, working_patch, untracked_patch)
             if part
         ),

tests/test_unified_diff_canvas.py

@@ -241,6 +241,45 @@ def test_parse_unified_diff_splits_hunk_lines_only_at_newlines() -> None:
     ]
 
 
+def test_parse_unified_diff_reads_empty_lines_inside_hunks_as_blank_context() -> None:
+    # Output of `git -c diff.suppressBlankEmpty=true diff`: blank context
+    # lines lose their leading space.
+    parsed = parse_unified_diff(
+        "diff --git a/notes.txt b/notes.txt\n"
+        "--- a/notes.txt\n"
+        "+++ b/notes.txt\n"
+        "@@ -1,4 +1,4 @@\n"
+        " a\n"
+        "\n"
+        "-b\n"
+        "+B\n"
+        "\n"
+        "diff --git a/next.txt b/next.txt\n"
+        "--- a/next.txt\n"
+        "+++ b/next.txt\n"
+        "@@ -1 +1 @@\n"
+        "-old\n"
+        "+new\n"
+        "\n"
+    )
+
+    first, second = parsed["files"]
+    assert first["additions"] == 1
+    assert first["deletions"] == 1
+    assert first["hunks"][0]["lines"] == [
+        {"kind": "context", "oldLine": 1, "newLine": 1, "text": "a"},
+        {"kind": "context", "oldLine": 2, "newLine": 2, "text": ""},
+        {"kind": "remove", "oldLine": 3, "text": "b"},
+        {"kind": "add", "newLine": 3, "text": "B"},
+        {"kind": "context", "oldLine": 4, "newLine": 4, "text": ""},
+    ]
+    assert second["hunks"][0]["lines"] == [
+        {"kind": "remove", "oldLine": 1, "text": "old"},
+        {"kind": "add", "newLine": 1, "text": "new"},
+    ]
+    assert parsed["lineCount"] == 7
+
+
 def test_parse_unified_diff_reads_copy_headers() -> None:
     # Output of `git -c diff.renames=copies diff HEAD` after copying a
     # modified file: an exact copy has no marker lines or hunks.
@@ -292,5 +331,6 @@ def test_parse_unified_diff_reads_copy_headers() -> None:
     test_diff_canvas_payload_keeps_report_for_local_mode_switch()
     test_parse_unified_diff_caps_files_without_merging_hunks()
     test_parse_unified_diff_splits_hunk_lines_only_at_newlines()
+    test_parse_unified_diff_reads_empty_lines_inside_hunks_as_blank_context()
     test_parse_unified_diff_reads_copy_headers()
     print("unified diff canvas tests passed")

tests/test_work_artifact_registry.py

@@ -427,6 +427,46 @@ async def run() -> None:
     asyncio.run(run())
 
 
+def test_attempt_diff_keeps_blank_context_lines_with_suppress_blank_empty() -> None:
+    async def run() -> None:
+        with tempfile.TemporaryDirectory(prefix="work_artifact_blank_context_") as temp:
+            root = Path(temp) / "project"
+            root.mkdir()
+            _git(root, "init")
+            _git(root, "config", "user.email", "amadeus-test@example.invalid")
+            _git(root, "config", "user.name", "Amadeus Test")
+            (root / "notes.txt").write_text("a\n\nb\nc\n", encoding="utf-8")
+            _git(root, "add", ".")
+            _git(root, "commit", "-m", "baseline")
+            _git(root, "config", "diff.suppressBlankEmpty", "true")
+
+            store = WorkLedgerStore(Path(temp) / "ledger.sqlite3")
+            project = store.create_or_get_project(root)
+            item = store.create_work_item(project.project_id, title="Edit notes")
+            attempt = store.create_attempt(item.work_item_id, provider="codex", task="Edit notes")
+            registry = WorkArtifactRegistry(store)
+            await registry.capture_baseline(attempt, item)
+            (root / "notes.txt").write_text("a\n\nB\nc\n", encoding="utf-8")
+
+            current_attempt = store.get_attempt(attempt.attempt_id)
+            assert current_attempt is not None
+            delta = await registry.finalize_attempt(current_attempt, item)
+            store.close()
+
+        assert "\n a\n\n-b\n" in delta["patch"]
+        parsed = parse_unified_diff(delta["patch"], changed_files=delta["changed_files"])
+        assert [entry["path"] for entry in parsed["files"]] == ["notes.txt"]
+        assert parsed["files"][0]["hunks"][0]["lines"] == [
+            {"kind": "context", "oldLine": 1, "newLine": 1, "text": "a"},
+            {"kind": "context", "oldLine": 2, "newLine": 2, "text": ""},
+            {"kind": "remove", "oldLine": 3, "text": "b"},
+            {"kind": "add", "newLine": 3, "text": "B"},
+            {"kind": "context", "oldLine": 4, "newLine": 4, "text": "c"},
+        ]
+
+    asyncio.run(run())
+
+
 def test_non_git_workspace_registers_new_files_without_claiming_preexisting_changes() -> None:
     async def run() -> None:
         with tempfile.TemporaryDirectory(prefix="work_artifact_filesystem_") as temp:
@@ -651,13 +691,71 @@ async def run() -> None:
     asyncio.run(run())
 
 
+@pytest.mark.parametrize("patch_sources", ["working", "committed", "both"])
+@pytest.mark.parametrize("blank_lines", [1, 2])
+def test_attempt_diff_preserves_trailing_blank_context(
+    tmp_path: Path, patch_sources: str, blank_lines: int,
+) -> None:
+    async def run() -> None:
+        root = tmp_path / "workspace"
+        root.mkdir()
+        _git(root, "init")
+        _git(root, "config", "user.email", "amadeus-test@example.invalid")
+        _git(root, "config", "user.name", "Amadeus Test")
+        _git(root, "config", "core.autocrlf", "false")
+        _git(root, "config", "diff.suppressBlankEmpty", "true")
+        before = ("x\ny\n" + "\n" * blank_lines).encode("utf-8")
+        after = ("X\ny\n" + "\n" * blank_lines).encode("utf-8")
+        paths = (
+            ["committed.txt", "working.txt"] if patch_sources == "both"
+            else [f"{patch_sources}.txt"]
+        )
+        for path in paths:
+            (root / path).write_bytes(before)
+        _git(root, "add", ".")
+        _git(root, "commit", "-m", "baseline")
+        with WorkLedgerStore(tmp_path / "ledger.sqlite3") as store:
+            project = store.create_or_get_project(root)
+            item = store.create_work_item(project.project_id, title="Edit files")
+            attempt = store.create_attempt(item.work_item_id, provider="codex", task="Edit files")
+            registry = WorkArtifactRegistry(store)
+            await registry.capture_baseline(attempt, item)
+            if "committed.txt" in paths:
+                (root / "committed.txt").write_bytes(after)
+                _git(root, "commit", "-am", "provider commit")
+            if "working.txt" in paths:
+                (root / "working.txt").write_bytes(after)
+            current_attempt = store.get_attempt(attempt.attempt_id)
+            assert current_attempt is not None
+            delta = await registry.finalize_attempt(current_attempt, item)
+
+        parsed = parse_unified_diff(delta["patch"], changed_files=delta["changed_files"])
+        assert sorted(file["path"] for file in parsed["files"]) == sorted(paths)
+        assert parsed["additions"] == parsed["deletions"] == len(paths)
+        for file in parsed["files"]:
+            hunk, = file["hunks"]
+            assert hunk["oldCount"] == hunk["newCount"] == 2 + blank_lines
+            assert hunk["lines"] == [
+                {"kind": "remove", "oldLine": 1, "text": "x"},
+                {"kind": "add", "newLine": 1, "text": "X"},
+                {"kind": "context", "oldLine": 2, "newLine": 2, "text": "y"},
+                *[
+                    {"kind": "context", "oldLine": number, "newLine": number, "text": ""}
+                    for number in range(3, 3 + blank_lines)
+                ],
+            ]
+
+    asyncio.run(run())
+
+
 def _main() -> None:
     test_committed_delta_survives_and_baseline_dirty_is_not_stolen()
     test_changed_preexisting_dirty_path_is_ambiguous_not_claimed_exact()
     test_non_ascii_entry_revision_is_registered_as_the_real_path()
     test_non_git_workspace_registers_new_files_without_claiming_preexisting_changes()
     test_explicit_amend_may_change_predecessor_owned_dirty_artifact()
     test_attempt_diff_lists_committed_copies_once_with_copy_detection()
+    test_attempt_diff_keeps_blank_context_lines_with_suppress_blank_empty()
     print("ok: work artifact registry preserves attempt Git boundaries")