From d50af1e1361a5905ed9139c21b2889081355cb28 Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 09:07:55 -0400
Subject: [PATCH 1/7] fix(azure-devops): implement incremental review (-i)
 support

Closes #2379.

`pr-agent review -i` against an Azure DevOps PR crashed with
`object of type 'NoneType' has no len()` because AzureDevopsProvider
inherited the no-op `GitProvider.get_incremental_commits` stub, leaving
`incremental.commits_range` as None. The hasattr guard in
`_can_run_incremental_review` was satisfied by the inherited stub.

Bug:
- Add `commits_range is None` guard in `_can_run_incremental_review`
  so any provider without real incremental support degrades gracefully.
- Defensive `previous_review.html_url` read in the no-new-files branch.

Feature (AzureDevopsProvider):
- Implement `get_incremental_commits`, `_get_incremental_commits`,
  `_get_commit_range`, `get_previous_review` mirroring GitHubProvider.
- `_AzureCommitAdapter` exposes the GitHub-shape (.sha, .commit.author.date,
  .commit.message, .parents) so shared code in pr_reviewer/IncrementalPR
  needs no changes.
- Reverse Azure's newest-first commit order to oldest-first to match
  GitHub iteration.
- Normalize tz-aware UTC datetimes (Azure SDK) to naive UTC, matching
  PyGithub semantics and `pr_reviewer`'s naive `datetime.now()` compare.
- Bridge Azure Comment to GitHub-shape attributes (`html_url` via
  existing `get_comment_url`, `created_at` from `published_date`).
- Filter `get_diff_files` to `unreviewed_files_set` and rebuild patches
  against `last_seen_commit_sha` when incremental, so token savings
  actually materialize.
- `get_files` override returns the unreviewed set when incremental.
- Skip merge commits (multiple parents) when collecting changes.
- Early-return in `get_diff_files` when `pr.last_merge_commit is None`
  instead of crashing on `head_sha.commit_id`.

Tests: tests/unittest/test_azure_devops_incremental.py (9 cases) covers
tz normalization, adapter shape, no-previous-review fallback, full
incremental path, merge-commit skip, and the commits_range None guard.
---
 .../git_providers/azuredevops_provider.py     | 164 ++++++++++++++++-
 pr_agent/tools/pr_reviewer.py                 |  10 +-
 .../unittest/test_azure_devops_incremental.py | 169 ++++++++++++++++++
 3 files changed, 339 insertions(+), 4 deletions(-)
 create mode 100644 tests/unittest/test_azure_devops_incremental.py

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index b9d2f3990c..4f12d3e016 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import datetime as _dt
 import os
 from typing import Optional, Tuple
 from urllib.parse import urlparse
@@ -8,12 +9,12 @@
 
 from ..algo.file_filter import filter_ignored
 from ..algo.language_handler import is_valid_file
-from ..algo.utils import (PRDescriptionHeader, clip_tokens,
+from ..algo.utils import (PRDescriptionHeader, PRReviewHeader, clip_tokens,
                           find_line_number_of_relevant_line_in_file,
                           load_large_diff)
 from ..config_loader import get_settings
 from ..log import get_logger
-from .git_provider import GitProvider
+from .git_provider import GitProvider, IncrementalPR
 
 AZURE_DEVOPS_AVAILABLE = True
 ADO_APP_CLIENT_DEFAULT_ID = "499b84ac-1321-427f-aa17-267ca6975798/.default"
@@ -32,6 +33,33 @@
     AZURE_DEVOPS_AVAILABLE = False
 
 
+def _to_naive_utc(dt):
+    if dt is None:
+        return None
+    if getattr(dt, "tzinfo", None) is not None:
+        return dt.astimezone(_dt.timezone.utc).replace(tzinfo=None)
+    return dt
+
+
+class _AzureCommitInner:
+    def __init__(self, raw):
+        self.message = getattr(raw, "comment", "") or ""
+        author = getattr(raw, "author", None)
+        author_date = _to_naive_utc(getattr(author, "date", None)) if author else None
+        self.author = type("_AzureAuthor", (), {"date": author_date})()
+
+
+class _AzureCommitAdapter:
+    """Mimics PyGithub `Commit` shape (.sha, .commit.author.date, .commit.message, .parents)."""
+
+    def __init__(self, raw):
+        self._raw = raw
+        self.sha = raw.commit_id
+        self.commit_id = raw.commit_id
+        self.commit = _AzureCommitInner(raw)
+        self.parents = list(getattr(raw, "parents", None) or [])
+
+
 class AzureDevopsProvider(GitProvider):
 
     def __init__(
@@ -51,6 +79,9 @@ def __init__(
         self.pr = None
         self.temp_comments = []
         self.incremental = incremental
+        self.unreviewed_files_set = {}
+        self.pr_commits = None
+        self.previous_review = None
         if pr_url:
             self.set_pr(pr_url)
 
@@ -158,6 +189,89 @@ def set_pr(self, pr_url: str):
         self.workspace_slug, self.repo_slug, self.pr_num = self._parse_pr_url(pr_url)
         self.pr = self._get_pr()
 
+    def get_incremental_commits(self, incremental=None):
+        if incremental is None:
+            incremental = IncrementalPR(False)
+        self.incremental = incremental
+        if self.incremental.is_incremental:
+            self.unreviewed_files_set = {}
+            self._get_incremental_commits()
+
+    def _get_incremental_commits(self):
+        if not self.pr_commits:
+            raw = list(self.azure_devops_client.get_pull_request_commits(
+                project=self.workspace_slug,
+                repository_id=self.repo_slug,
+                pull_request_id=self.pr_num,
+            ))
+            # Azure returns newest-first; oldest-first matches GitHub iteration order.
+            raw.reverse()
+            self.pr_commits = [_AzureCommitAdapter(c) for c in raw]
+
+        self.previous_review = self.get_previous_review(full=True, incremental=True)
+        if not self.previous_review:
+            get_logger().info("No previous review found, will review the entire PR")
+            self.incremental.is_incremental = False
+            return
+
+        self.incremental.commits_range = self._get_commit_range()
+        for commit in self.incremental.commits_range:
+            if len(commit.parents) > 1:
+                get_logger().info(f"Skipping merge commit {commit.sha}")
+                continue
+            try:
+                changes_obj = self.azure_devops_client.get_changes(
+                    project=self.workspace_slug,
+                    repository_id=self.repo_slug,
+                    commit_id=commit.commit_id,
+                )
+            except Exception as e:
+                get_logger().warning(f"Failed to fetch changes for {commit.commit_id}: {e}")
+                continue
+            for change in (getattr(changes_obj, "changes", None) or []):
+                try:
+                    item = change["item"]
+                except (KeyError, TypeError):
+                    item = getattr(change, "additional_properties", {}).get("item", {}) or {}
+                if not isinstance(item, dict) or item.get("gitObjectType") == "tree":
+                    continue
+                path = item.get("path")
+                if path:
+                    self.unreviewed_files_set[path] = path
+
+    def _get_commit_range(self):
+        last_review_time = _to_naive_utc(getattr(self.previous_review, "created_at", None))
+        if last_review_time is None or not self.pr_commits:
+            return []
+        first_new_commit_index = None
+        for index in range(len(self.pr_commits) - 1, -1, -1):
+            cdate = self.pr_commits[index].commit.author.date
+            if cdate is None:
+                continue
+            if cdate > last_review_time:
+                self.incremental.first_new_commit = self.pr_commits[index]
+                first_new_commit_index = index
+            else:
+                self.incremental.last_seen_commit = self.pr_commits[index]
+                break
+        return self.pr_commits[first_new_commit_index:] if first_new_commit_index is not None else []
+
+    def get_previous_review(self, *, full: bool, incremental: bool):
+        if not (full or incremental):
+            raise ValueError("At least one of full or incremental must be True")
+        prefixes = []
+        if full:
+            prefixes.append(PRReviewHeader.REGULAR.value)
+        if incremental:
+            prefixes.append(PRReviewHeader.INCREMENTAL.value)
+        for comment in self.get_issue_comments():
+            body = getattr(comment, "body", None)
+            if body and any(body.startswith(p) for p in prefixes):
+                comment.html_url = self.get_comment_url(comment)
+                comment.created_at = _to_naive_utc(getattr(comment, "published_date", None))
+                return comment
+        return None
+
     def get_repo_settings(self):
         try:
             contents = self.azure_devops_client.get_item_content(
@@ -175,6 +289,13 @@ def get_repo_settings(self):
             return ""
 
     def get_files(self):
+        if (isinstance(getattr(self, "incremental", None), IncrementalPR)
+                and self.incremental.is_incremental
+                and self.unreviewed_files_set):
+            return list(self.unreviewed_files_set.keys())
+        return self._get_files_full()
+
+    def _get_files_full(self):
         files = []
         for i in self.azure_devops_client.get_pull_request_commits(
                 project=self.workspace_slug,
@@ -197,6 +318,14 @@ def get_diff_files(self) -> list[FilePatchInfo]:
             if self.diff_files:
                 return self.diff_files
 
+            if self.pr.last_merge_commit is None or self.pr.last_merge_target_commit is None:
+                get_logger().info(
+                    f"PR {self.pr_num} has no last_merge_commit/last_merge_target_commit; "
+                    f"cannot compute diff files."
+                )
+                self.diff_files = []
+                return []
+
             base_sha = self.pr.last_merge_target_commit
             head_sha = self.pr.last_merge_commit
 
@@ -263,6 +392,15 @@ def get_diff_files(self) -> list[FilePatchInfo]:
                 except Exception:
                     pass
 
+            incremental_active = (
+                isinstance(getattr(self, "incremental", None), IncrementalPR)
+                and self.incremental.is_incremental
+                and bool(self.unreviewed_files_set)
+                and self.incremental.last_seen_commit_sha
+            )
+            if incremental_active:
+                diffs = [f for f in diffs if f in self.unreviewed_files_set]
+
             invalid_files_names = []
             for file in diffs:
                 if not is_valid_file(file):
@@ -321,9 +459,31 @@ def get_diff_files(self) -> list[FilePatchInfo]:
                         get_logger().error(f"Failed to retrieve original file content of {file} at version {version}", error=error)
                         original_file_content_str = ""
 
+                if incremental_active:
+                    inc_version = GitVersionDescriptor(
+                        version=self.incremental.last_seen_commit_sha, version_type="commit"
+                    )
+                    try:
+                        inc_original = self.azure_devops_client.get_item(
+                            repository_id=self.repo_slug,
+                            path=file,
+                            project=self.workspace_slug,
+                            version_descriptor=inc_version,
+                            download=False,
+                            include_content=True,
+                        )
+                        original_file_content_str = inc_original.content or ""
+                    except Exception as error:
+                        get_logger().warning(
+                            f"Failed to retrieve original of {file} at {self.incremental.last_seen_commit_sha}: {error}"
+                        )
+                        original_file_content_str = ""
+
                 patch = load_large_diff(
                     file, new_file_content_str, original_file_content_str, show_warning=False
                 ).rstrip()
+                if incremental_active:
+                    self.unreviewed_files_set[file] = patch
 
                 # count number of lines added and removed
                 patch_lines = patch.splitlines(keepends=True)
diff --git a/pr_agent/tools/pr_reviewer.py b/pr_agent/tools/pr_reviewer.py
index c4917f3597..425b5f5323 100644
--- a/pr_agent/tools/pr_reviewer.py
+++ b/pr_agent/tools/pr_reviewer.py
@@ -142,8 +142,8 @@ async def run(self) -> None:
             if self.incremental.is_incremental and hasattr(self.git_provider, "unreviewed_files_set") and not self.git_provider.unreviewed_files_set:
                 get_logger().info(f"Incremental review is enabled for {self.pr_url} but there are no new files")
                 previous_review_url = ""
-                if hasattr(self.git_provider, "previous_review"):
-                    previous_review_url = self.git_provider.previous_review.html_url
+                if hasattr(self.git_provider, "previous_review") and self.git_provider.previous_review is not None:
+                    previous_review_url = getattr(self.git_provider.previous_review, "html_url", "") or ""
                 if get_settings().config.publish_output:
                     self.git_provider.publish_comment(f"Incremental Review Skipped\n"
                                     f"No files were changed since the [previous PR Review]({previous_review_url})")
@@ -337,6 +337,12 @@ def _can_run_incremental_review(self) -> bool:
         if not hasattr(self.git_provider, "get_incremental_commits"):
             get_logger().info(f"Incremental review is not supported for {get_settings().config.git_provider}")
             return False
+        if self.incremental.commits_range is None:
+            get_logger().info(
+                f"Incremental review not initialized for {get_settings().config.git_provider}; "
+                f"falling back to full review."
+            )
+            return False
         # checking if there are enough commits to start the review
         num_new_commits = len(self.incremental.commits_range)
         num_commits_threshold = get_settings().pr_reviewer.minimal_commits_for_incremental_review
diff --git a/tests/unittest/test_azure_devops_incremental.py b/tests/unittest/test_azure_devops_incremental.py
new file mode 100644
index 0000000000..e693fcb57a
--- /dev/null
+++ b/tests/unittest/test_azure_devops_incremental.py
@@ -0,0 +1,169 @@
+import datetime as _dt
+import unittest
+from unittest.mock import MagicMock, patch
+
+from pr_agent.git_providers import AzureDevopsProvider
+from pr_agent.git_providers.azuredevops_provider import (
+    _AzureCommitAdapter,
+    _to_naive_utc,
+)
+from pr_agent.git_providers.git_provider import IncrementalPR
+
+
+def _raw_commit(commit_id, comment, author_date, parents=None):
+    raw = MagicMock()
+    raw.commit_id = commit_id
+    raw.comment = comment
+    raw.author = MagicMock()
+    raw.author.date = author_date
+    raw.parents = parents or []
+    return raw
+
+
+def _comment(body, published_date):
+    c = MagicMock()
+    c.body = body
+    c.content = body
+    c.published_date = published_date
+    c.thread_id = 7
+    return c
+
+
+class TestNaiveUtc(unittest.TestCase):
+    def test_strips_tz_from_aware(self):
+        aware = _dt.datetime(2024, 1, 1, 12, 0, tzinfo=_dt.timezone.utc)
+        naive = _to_naive_utc(aware)
+        self.assertIsNone(naive.tzinfo)
+        self.assertEqual(naive, _dt.datetime(2024, 1, 1, 12, 0))
+
+    def test_passes_naive_through(self):
+        naive = _dt.datetime(2024, 1, 1, 12, 0)
+        self.assertEqual(_to_naive_utc(naive), naive)
+
+    def test_none_returns_none(self):
+        self.assertIsNone(_to_naive_utc(None))
+
+
+class TestAzureCommitAdapter(unittest.TestCase):
+    def test_exposes_github_shape(self):
+        date = _dt.datetime(2024, 1, 1, 12, 0, tzinfo=_dt.timezone.utc)
+        raw = _raw_commit("abc123", "fix bug", date, parents=["p1"])
+        adapter = _AzureCommitAdapter(raw)
+        self.assertEqual(adapter.sha, "abc123")
+        self.assertEqual(adapter.commit_id, "abc123")
+        self.assertEqual(adapter.commit.message, "fix bug")
+        self.assertIsNone(adapter.commit.author.date.tzinfo)
+        self.assertEqual(adapter.parents, ["p1"])
+
+    def test_handles_missing_author(self):
+        raw = MagicMock()
+        raw.commit_id = "x"
+        raw.comment = ""
+        raw.author = None
+        raw.parents = None
+        adapter = _AzureCommitAdapter(raw)
+        self.assertIsNone(adapter.commit.author.date)
+        self.assertEqual(adapter.parents, [])
+
+
+class TestGetIncrementalCommits(unittest.TestCase):
+    def _make_provider(self):
+        with patch.object(
+            AzureDevopsProvider, "_get_azure_devops_client",
+            return_value=(MagicMock(), MagicMock()),
+        ):
+            provider = AzureDevopsProvider()
+        provider.workspace_slug = "ws"
+        provider.repo_slug = "repo"
+        provider.pr_num = 1
+        provider.pr_url = "https://dev.azure.com/o/ws/_git/repo/pullrequest/1"
+        return provider
+
+    def test_no_previous_review_disables_incremental(self):
+        provider = self._make_provider()
+        provider.azure_devops_client.get_pull_request_commits = MagicMock(return_value=[])
+        provider.get_issue_comments = MagicMock(return_value=[])
+
+        inc = IncrementalPR(True)
+        provider.get_incremental_commits(inc)
+
+        self.assertFalse(provider.incremental.is_incremental)
+        self.assertIsNone(provider.previous_review)
+
+    def test_populates_commits_range_and_files(self):
+        provider = self._make_provider()
+
+        review_time = _dt.datetime(2024, 6, 1, 10, 0, tzinfo=_dt.timezone.utc)
+        old = _raw_commit(
+            "old1", "first", _dt.datetime(2024, 5, 1, tzinfo=_dt.timezone.utc), parents=["p0"],
+        )
+        new1 = _raw_commit(
+            "new1", "second", _dt.datetime(2024, 6, 2, tzinfo=_dt.timezone.utc), parents=["old1"],
+        )
+        new2 = _raw_commit(
+            "new2", "third", _dt.datetime(2024, 6, 3, tzinfo=_dt.timezone.utc), parents=["new1"],
+        )
+        # Azure returns newest-first.
+        provider.azure_devops_client.get_pull_request_commits = MagicMock(
+            return_value=[new2, new1, old]
+        )
+
+        prev = _comment("## PR Reviewer Guide\nbody", review_time)
+        provider.get_issue_comments = MagicMock(return_value=[prev])
+
+        changes_obj = MagicMock()
+        changes_obj.changes = [
+            {"item": {"path": "/foo.py", "gitObjectType": "blob"}},
+            {"item": {"path": "/bar.py", "gitObjectType": "blob"}},
+            {"item": {"path": "/somedir", "gitObjectType": "tree"}},
+        ]
+        provider.azure_devops_client.get_changes = MagicMock(return_value=changes_obj)
+
+        inc = IncrementalPR(True)
+        provider.get_incremental_commits(inc)
+
+        self.assertTrue(provider.incremental.is_incremental)
+        self.assertEqual(len(provider.incremental.commits_range), 2)
+        self.assertEqual(provider.incremental.first_new_commit.sha, "new1")
+        self.assertEqual(provider.incremental.last_seen_commit.sha, "old1")
+        self.assertEqual(provider.incremental.last_seen_commit_sha, "old1")
+        self.assertIn("/foo.py", provider.unreviewed_files_set)
+        self.assertIn("/bar.py", provider.unreviewed_files_set)
+        self.assertNotIn("/somedir", provider.unreviewed_files_set)
+        self.assertEqual(prev.html_url, provider.get_comment_url(prev))
+
+    def test_skips_merge_commits(self):
+        provider = self._make_provider()
+        review_time = _dt.datetime(2024, 6, 1, tzinfo=_dt.timezone.utc)
+        merge = _raw_commit(
+            "m1", "merge", _dt.datetime(2024, 6, 2, tzinfo=_dt.timezone.utc),
+            parents=["a", "b"],
+        )
+        old = _raw_commit("o", "old", _dt.datetime(2024, 5, 1, tzinfo=_dt.timezone.utc))
+        provider.azure_devops_client.get_pull_request_commits = MagicMock(
+            return_value=[merge, old]
+        )
+        provider.get_issue_comments = MagicMock(
+            return_value=[_comment("## PR Reviewer Guide", review_time)]
+        )
+        provider.azure_devops_client.get_changes = MagicMock()
+
+        provider.get_incremental_commits(IncrementalPR(True))
+        provider.azure_devops_client.get_changes.assert_not_called()
+
+
+class TestPrReviewerGuard(unittest.TestCase):
+    def test_can_run_returns_false_when_commits_range_none(self):
+        from pr_agent.tools.pr_reviewer import PRReviewer
+        reviewer = PRReviewer.__new__(PRReviewer)
+        reviewer.is_auto = False
+        reviewer.pr_url = "u"
+        reviewer.incremental = IncrementalPR(True)
+        # incremental.commits_range stays None — provider has the method but didn't populate it.
+        reviewer.git_provider = MagicMock(spec=["get_incremental_commits"])
+        # Should not raise NoneType len() error.
+        self.assertFalse(reviewer._can_run_incremental_review())
+
+
+if __name__ == "__main__":
+    unittest.main()

From d2b3b96648c4f48098f9240642eb42357aa92e53 Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 11:19:48 -0400
Subject: [PATCH 2/7] fix(azure-devops): address Qodo review on incremental
 review

- Guard against None additional_properties when parsing commit changes.
- Apply filter_ignored/is_valid_file when building unreviewed_files_set
  so it matches get_diff_files() filtering.
- When commits_range is None, disable incremental and proceed with a
  full review instead of returning early.
---
 pr_agent/git_providers/azuredevops_provider.py | 10 +++++++++-
 pr_agent/tools/pr_reviewer.py                  |  3 ++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index 4f12d3e016..17e9620e5d 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -215,6 +215,7 @@ def _get_incremental_commits(self):
             return
 
         self.incremental.commits_range = self._get_commit_range()
+        candidate_paths = []
         for commit in self.incremental.commits_range:
             if len(commit.parents) > 1:
                 get_logger().info(f"Skipping merge commit {commit.sha}")
@@ -232,11 +233,18 @@ def _get_incremental_commits(self):
                 try:
                     item = change["item"]
                 except (KeyError, TypeError):
-                    item = getattr(change, "additional_properties", {}).get("item", {}) or {}
+                    additional = getattr(change, "additional_properties", None) or {}
+                    item = additional.get("item") or {}
                 if not isinstance(item, dict) or item.get("gitObjectType") == "tree":
                     continue
                 path = item.get("path")
                 if path:
+                    candidate_paths.append(path)
+
+        if candidate_paths:
+            filtered = filter_ignored(list(set(candidate_paths)), 'azure')
+            for path in filtered:
+                if is_valid_file(path):
                     self.unreviewed_files_set[path] = path
 
     def _get_commit_range(self):
diff --git a/pr_agent/tools/pr_reviewer.py b/pr_agent/tools/pr_reviewer.py
index 425b5f5323..a7bf90c234 100644
--- a/pr_agent/tools/pr_reviewer.py
+++ b/pr_agent/tools/pr_reviewer.py
@@ -342,7 +342,8 @@ def _can_run_incremental_review(self) -> bool:
                 f"Incremental review not initialized for {get_settings().config.git_provider}; "
                 f"falling back to full review."
             )
-            return False
+            self.incremental.is_incremental = False
+            return True
         # checking if there are enough commits to start the review
         num_new_commits = len(self.incremental.commits_range)
         num_commits_threshold = get_settings().pr_reviewer.minimal_commits_for_incremental_review

From 63b58a6bcddff8fbaa1aa7d4adffc72f935b4843 Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 14:11:22 -0400
Subject: [PATCH 3/7] fix(azure-devops): pick newest previous review, preserve
 dedup order

- get_previous_review() now selects the most recent matching PR-Agent
  review by published_date instead of returning the first match. The
  prior behavior could feed a stale timestamp into the commit-range
  computation when multiple reviews existed.
- Replace set(candidate_paths) with dict.fromkeys(...) so incremental
  file-list dedup is order-preserving and deterministic across runs.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 pr_agent/git_providers/azuredevops_provider.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index 17e9620e5d..db7b527392 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -242,7 +242,8 @@ def _get_incremental_commits(self):
                     candidate_paths.append(path)
 
         if candidate_paths:
-            filtered = filter_ignored(list(set(candidate_paths)), 'azure')
+            deduped = list(dict.fromkeys(candidate_paths))
+            filtered = filter_ignored(deduped, 'azure')
             for path in filtered:
                 if is_valid_file(path):
                     self.unreviewed_files_set[path] = path
@@ -272,13 +273,17 @@ def get_previous_review(self, *, full: bool, incremental: bool):
             prefixes.append(PRReviewHeader.REGULAR.value)
         if incremental:
             prefixes.append(PRReviewHeader.INCREMENTAL.value)
+        matches = []
         for comment in self.get_issue_comments():
             body = getattr(comment, "body", None)
             if body and any(body.startswith(p) for p in prefixes):
-                comment.html_url = self.get_comment_url(comment)
-                comment.created_at = _to_naive_utc(getattr(comment, "published_date", None))
-                return comment
-        return None
+                matches.append(comment)
+        if not matches:
+            return None
+        latest = max(matches, key=lambda c: _to_naive_utc(getattr(c, "published_date", None)) or _dt.datetime.min)
+        latest.html_url = self.get_comment_url(latest)
+        latest.created_at = _to_naive_utc(getattr(latest, "published_date", None))
+        return latest
 
     def get_repo_settings(self):
         try:

From 4041c38914c3630d3bd4c5ed39f7645a946d7e6d Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 14:47:55 -0400
Subject: [PATCH 4/7] fix(azure-devops): gate fallback returns False; treat
 fetch errors as fallback

- _can_run_incremental_review() now returns False (not True) when
  incremental.commits_range is None, satisfying compliance ID 6 and
  the test_can_run_returns_false_when_commits_range_none unit test.
- PRReviewer.run() distinguishes "gate disabled incremental" (fall
  through to full review) from "gate said skip" (return early), so
  the previous fallback log line now produces an actual full review.
- _get_incremental_commits() tracks had_errors so that transient Azure
  get_changes failures disable incremental and fall back to a full
  review instead of being silently skipped as "no new files".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 pr_agent/git_providers/azuredevops_provider.py | 7 +++++++
 pr_agent/tools/pr_reviewer.py                  | 9 ++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index db7b527392..db9fff78d7 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -216,6 +216,7 @@ def _get_incremental_commits(self):
 
         self.incremental.commits_range = self._get_commit_range()
         candidate_paths = []
+        had_errors = False
         for commit in self.incremental.commits_range:
             if len(commit.parents) > 1:
                 get_logger().info(f"Skipping merge commit {commit.sha}")
@@ -227,6 +228,7 @@ def _get_incremental_commits(self):
                     commit_id=commit.commit_id,
                 )
             except Exception as e:
+                had_errors = True
                 get_logger().warning(f"Failed to fetch changes for {commit.commit_id}: {e}")
                 continue
             for change in (getattr(changes_obj, "changes", None) or []):
@@ -247,6 +249,11 @@ def _get_incremental_commits(self):
             for path in filtered:
                 if is_valid_file(path):
                     self.unreviewed_files_set[path] = path
+        elif had_errors and self.incremental.commits_range:
+            get_logger().warning(
+                "Failed to fetch changes for incremental commits; falling back to full review."
+            )
+            self.incremental.is_incremental = False
 
     def _get_commit_range(self):
         last_review_time = _to_naive_utc(getattr(self.previous_review, "created_at", None))
diff --git a/pr_agent/tools/pr_reviewer.py b/pr_agent/tools/pr_reviewer.py
index a7bf90c234..a3d7eeee1e 100644
--- a/pr_agent/tools/pr_reviewer.py
+++ b/pr_agent/tools/pr_reviewer.py
@@ -123,8 +123,11 @@ async def run(self) -> None:
                 get_logger().info(f"PR has no files: {self.pr_url}, skipping review")
                 return None
 
-            if self.incremental.is_incremental and not self._can_run_incremental_review():
-                return None
+            if self.incremental.is_incremental:
+                can_run = self._can_run_incremental_review()
+                # If the gate disabled incremental (e.g., commits_range is None), fall through to full review.
+                if not can_run and self.incremental.is_incremental:
+                    return None
 
             # if isinstance(self.args, list) and self.args and self.args[0] == 'auto_approve':
             #     get_logger().info(f'Auto approve flow PR: {self.pr_url} ...')
@@ -343,7 +346,7 @@ def _can_run_incremental_review(self) -> bool:
                 f"falling back to full review."
             )
             self.incremental.is_incremental = False
-            return True
+            return False
         # checking if there are enough commits to start the review
         num_new_commits = len(self.incremental.commits_range)
         num_commits_threshold = get_settings().pr_reviewer.minimal_commits_for_incremental_review

From 55cd982576f8a06f2d201b583065257a3c2b6aa1 Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 15:05:43 -0400
Subject: [PATCH 5/7] fix(azure-devops): rm redundant base fetch, cache empty
 diff, rename map, polish

- get_diff_files: incremental path now substitutes for the base-SHA
  original fetch instead of fetching base then overwriting, saving one
  Azure get_item call per modified file in incremental runs.
- get_diff_files: cache guard switched to `is not None` so the
  early-return on missing last_merge_commit/last_merge_target_commit is
  cached (`[]` is falsy and was being recomputed each call).
- Rename `unreviewed_files_set` -> `unreviewed_files_map` across Azure,
  GitHub, Gitea providers, the reviewer, and the unit test. The
  attribute has always been a dict (path -> path/patch); the old name
  was misleading.
- Wrap get_previous_review max() lambda for readability.
- Normalize filter_ignored(..., "azure") to double-quoted literal.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 .../git_providers/azuredevops_provider.py     | 63 ++++++++++---------
 pr_agent/git_providers/gitea_provider.py      |  6 +-
 pr_agent/git_providers/github_provider.py     | 12 ++--
 pr_agent/tools/pr_reviewer.py                 |  2 +-
 .../unittest/test_azure_devops_incremental.py |  6 +-
 5 files changed, 47 insertions(+), 42 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index db9fff78d7..447233b436 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -79,7 +79,7 @@ def __init__(
         self.pr = None
         self.temp_comments = []
         self.incremental = incremental
-        self.unreviewed_files_set = {}
+        self.unreviewed_files_map = {}
         self.pr_commits = None
         self.previous_review = None
         if pr_url:
@@ -194,7 +194,7 @@ def get_incremental_commits(self, incremental=None):
             incremental = IncrementalPR(False)
         self.incremental = incremental
         if self.incremental.is_incremental:
-            self.unreviewed_files_set = {}
+            self.unreviewed_files_map = {}
             self._get_incremental_commits()
 
     def _get_incremental_commits(self):
@@ -245,10 +245,10 @@ def _get_incremental_commits(self):
 
         if candidate_paths:
             deduped = list(dict.fromkeys(candidate_paths))
-            filtered = filter_ignored(deduped, 'azure')
+            filtered = filter_ignored(deduped, "azure")
             for path in filtered:
                 if is_valid_file(path):
-                    self.unreviewed_files_set[path] = path
+                    self.unreviewed_files_map[path] = path
         elif had_errors and self.incremental.commits_range:
             get_logger().warning(
                 "Failed to fetch changes for incremental commits; falling back to full review."
@@ -287,7 +287,10 @@ def get_previous_review(self, *, full: bool, incremental: bool):
                 matches.append(comment)
         if not matches:
             return None
-        latest = max(matches, key=lambda c: _to_naive_utc(getattr(c, "published_date", None)) or _dt.datetime.min)
+        latest = max(
+            matches,
+            key=lambda c: _to_naive_utc(getattr(c, "published_date", None)) or _dt.datetime.min,
+        )
         latest.html_url = self.get_comment_url(latest)
         latest.created_at = _to_naive_utc(getattr(latest, "published_date", None))
         return latest
@@ -311,8 +314,8 @@ def get_repo_settings(self):
     def get_files(self):
         if (isinstance(getattr(self, "incremental", None), IncrementalPR)
                 and self.incremental.is_incremental
-                and self.unreviewed_files_set):
-            return list(self.unreviewed_files_set.keys())
+                and self.unreviewed_files_map):
+            return list(self.unreviewed_files_map.keys())
         return self._get_files_full()
 
     def _get_files_full(self):
@@ -335,7 +338,7 @@ def _get_files_full(self):
     def get_diff_files(self) -> list[FilePatchInfo]:
         try:
 
-            if self.diff_files:
+            if self.diff_files is not None:
                 return self.diff_files
 
             if self.pr.last_merge_commit is None or self.pr.last_merge_target_commit is None:
@@ -403,7 +406,7 @@ def get_diff_files(self) -> list[FilePatchInfo]:
             # diffs = list(set(diffs))
 
             diffs_original = diffs
-            diffs = filter_ignored(diffs_original, 'azure')
+            diffs = filter_ignored(diffs_original, "azure")
             if diffs_original != diffs:
                 try:
                     get_logger().info(f"Filtered out [ignore] files for pull request:", extra=
@@ -415,11 +418,11 @@ def get_diff_files(self) -> list[FilePatchInfo]:
             incremental_active = (
                 isinstance(getattr(self, "incremental", None), IncrementalPR)
                 and self.incremental.is_incremental
-                and bool(self.unreviewed_files_set)
+                and bool(self.unreviewed_files_map)
                 and self.incremental.last_seen_commit_sha
             )
             if incremental_active:
-                diffs = [f for f in diffs if f in self.unreviewed_files_set]
+                diffs = [f for f in diffs if f in self.unreviewed_files_map]
 
             invalid_files_names = []
             for file in diffs:
@@ -459,43 +462,45 @@ def get_diff_files(self) -> list[FilePatchInfo]:
                 elif "rename" in diff_types[file]: # diff_type can be `rename` | `edit, rename`
                     edit_type = EDIT_TYPE.RENAMED
 
-                version = GitVersionDescriptor(
-                    version=base_sha.commit_id, version_type="commit"
-                )
                 if edit_type == EDIT_TYPE.ADDED or edit_type == EDIT_TYPE.RENAMED:
                     original_file_content_str = ""
-                else:
+                elif incremental_active:
+                    inc_version = GitVersionDescriptor(
+                        version=self.incremental.last_seen_commit_sha, version_type="commit"
+                    )
                     try:
-                        original_file_content_str = self.azure_devops_client.get_item(
+                        inc_original = self.azure_devops_client.get_item(
                             repository_id=self.repo_slug,
                             path=file,
                             project=self.workspace_slug,
-                            version_descriptor=version,
+                            version_descriptor=inc_version,
                             download=False,
                             include_content=True,
                         )
-                        original_file_content_str = original_file_content_str.content
+                        original_file_content_str = inc_original.content or ""
                     except Exception as error:
-                        get_logger().error(f"Failed to retrieve original file content of {file} at version {version}", error=error)
+                        get_logger().warning(
+                            f"Failed to retrieve original of {file} at {self.incremental.last_seen_commit_sha}: {error}"
+                        )
                         original_file_content_str = ""
-
-                if incremental_active:
-                    inc_version = GitVersionDescriptor(
-                        version=self.incremental.last_seen_commit_sha, version_type="commit"
+                else:
+                    base_version = GitVersionDescriptor(
+                        version=base_sha.commit_id, version_type="commit"
                     )
                     try:
-                        inc_original = self.azure_devops_client.get_item(
+                        base_original = self.azure_devops_client.get_item(
                             repository_id=self.repo_slug,
                             path=file,
                             project=self.workspace_slug,
-                            version_descriptor=inc_version,
+                            version_descriptor=base_version,
                             download=False,
                             include_content=True,
                         )
-                        original_file_content_str = inc_original.content or ""
+                        original_file_content_str = base_original.content
                     except Exception as error:
-                        get_logger().warning(
-                            f"Failed to retrieve original of {file} at {self.incremental.last_seen_commit_sha}: {error}"
+                        get_logger().error(
+                            f"Failed to retrieve original file content of {file} at version {base_version}",
+                            error=error,
                         )
                         original_file_content_str = ""
 
@@ -503,7 +508,7 @@ def get_diff_files(self) -> list[FilePatchInfo]:
                     file, new_file_content_str, original_file_content_str, show_warning=False
                 ).rstrip()
                 if incremental_active:
-                    self.unreviewed_files_set[file] = patch
+                    self.unreviewed_files_map[file] = patch
 
                 # count number of lines added and removed
                 patch_lines = patch.splitlines(keepends=True)
diff --git a/pr_agent/git_providers/gitea_provider.py b/pr_agent/git_providers/gitea_provider.py
index 89a6248e9b..d3d7f20624 100644
--- a/pr_agent/git_providers/gitea_provider.py
+++ b/pr_agent/git_providers/gitea_provider.py
@@ -64,7 +64,7 @@ def __init__(self, url: Optional[str] = None):
         self.diff_files = []
         self.incremental = IncrementalPR(False)
         self.comments_list = []
-        self.unreviewed_files_set = dict()
+        self.unreviewed_files_map = dict()
 
         if "pulls" in url:
             self.pr_url = url
@@ -475,9 +475,9 @@ def get_diff_files(self) -> List[FilePatchInfo]:
                 # Get file content from this pr
                 head_file = self.file_contents.get(filename,"")
 
-            if self.incremental.is_incremental and self.unreviewed_files_set:
+            if self.incremental.is_incremental and self.unreviewed_files_map:
                 base_file = self._get_file_content_from_latest_commit(filename)
-                self.unreviewed_files_set[filename] = patch
+                self.unreviewed_files_map[filename] = patch
             else:
                 if avoid_load:
                     base_file = ""
diff --git a/pr_agent/git_providers/github_provider.py b/pr_agent/git_providers/github_provider.py
index fa52b7dc05..901f66b5d1 100644
--- a/pr_agent/git_providers/github_provider.py
+++ b/pr_agent/git_providers/github_provider.py
@@ -79,7 +79,7 @@ def _get_issue_handle(self, issue_url) -> Optional[Issue]:
     def get_incremental_commits(self, incremental=IncrementalPR(False)):
         self.incremental = incremental
         if self.incremental.is_incremental:
-            self.unreviewed_files_set = dict()
+            self.unreviewed_files_map = dict()
             self._get_incremental_commits()
 
     def is_supported(self, capability: str) -> bool:
@@ -162,7 +162,7 @@ def _get_incremental_commits(self):
                 if commit.commit.message.startswith(f"Merge branch '{self._get_repo().default_branch}'"):
                     get_logger().info(f"Skipping merge commit {commit.commit.message}")
                     continue
-                self.unreviewed_files_set.update({file.filename: file for file in commit.files})
+                self.unreviewed_files_map.update({file.filename: file for file in commit.files})
         else:
             get_logger().info("No previous review found, will review the entire PR")
             self.incremental.is_incremental = False
@@ -194,8 +194,8 @@ def get_previous_review(self, *, full: bool, incremental: bool):
                 return self.comments[index]
 
     def get_files(self):
-        if self.incremental.is_incremental and self.unreviewed_files_set:
-            return self.unreviewed_files_set.values()
+        if self.incremental.is_incremental and self.unreviewed_files_map:
+            return self.unreviewed_files_map.values()
         try:
             git_files = context.get("git_files", None)
             if git_files:
@@ -296,10 +296,10 @@ def get_diff_files(self) -> list[FilePatchInfo]:
                     else:
                         new_file_content_str = self._get_pr_file_content(file, self.pr.head.sha)  # communication with GitHub
 
-                    if self.incremental.is_incremental and self.unreviewed_files_set:
+                    if self.incremental.is_incremental and self.unreviewed_files_map:
                         original_file_content_str = self._get_pr_file_content(file, self.incremental.last_seen_commit_sha)
                         patch = load_large_diff(file.filename, new_file_content_str, original_file_content_str)
-                        self.unreviewed_files_set[file.filename] = patch
+                        self.unreviewed_files_map[file.filename] = patch
                     else:
                         if avoid_load:
                             original_file_content_str = ""
diff --git a/pr_agent/tools/pr_reviewer.py b/pr_agent/tools/pr_reviewer.py
index a3d7eeee1e..67882a27d5 100644
--- a/pr_agent/tools/pr_reviewer.py
+++ b/pr_agent/tools/pr_reviewer.py
@@ -142,7 +142,7 @@ async def run(self) -> None:
             # ticket extraction if exists
             await extract_and_cache_pr_tickets(self.git_provider, self.vars)
 
-            if self.incremental.is_incremental and hasattr(self.git_provider, "unreviewed_files_set") and not self.git_provider.unreviewed_files_set:
+            if self.incremental.is_incremental and hasattr(self.git_provider, "unreviewed_files_map") and not self.git_provider.unreviewed_files_map:
                 get_logger().info(f"Incremental review is enabled for {self.pr_url} but there are no new files")
                 previous_review_url = ""
                 if hasattr(self.git_provider, "previous_review") and self.git_provider.previous_review is not None:
diff --git a/tests/unittest/test_azure_devops_incremental.py b/tests/unittest/test_azure_devops_incremental.py
index e693fcb57a..79c220a2b8 100644
--- a/tests/unittest/test_azure_devops_incremental.py
+++ b/tests/unittest/test_azure_devops_incremental.py
@@ -127,9 +127,9 @@ def test_populates_commits_range_and_files(self):
         self.assertEqual(provider.incremental.first_new_commit.sha, "new1")
         self.assertEqual(provider.incremental.last_seen_commit.sha, "old1")
         self.assertEqual(provider.incremental.last_seen_commit_sha, "old1")
-        self.assertIn("/foo.py", provider.unreviewed_files_set)
-        self.assertIn("/bar.py", provider.unreviewed_files_set)
-        self.assertNotIn("/somedir", provider.unreviewed_files_set)
+        self.assertIn("/foo.py", provider.unreviewed_files_map)
+        self.assertIn("/bar.py", provider.unreviewed_files_map)
+        self.assertNotIn("/somedir", provider.unreviewed_files_map)
         self.assertEqual(prev.html_url, provider.get_comment_url(prev))
 
     def test_skips_merge_commits(self):

From 2690d2774d02550529f49a0e13e32ee64fe7f88b Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 15:20:36 -0400
Subject: [PATCH 6/7] fix(azure-devops): fall back to full review when commit
 dates are unreliable

- _get_commit_range now returns None (not []) when the previous review
  has no timestamp, no PR commits exist, or every commit author date is
  None, and disables incremental so PRReviewer's existing
  `commits_range is None` fallback path runs a full review instead of
  silently exiting via the threshold check.
- _get_incremental_commits short-circuits when _get_commit_range
  returns None, avoiding TypeError on the iteration that follows.
- Wraps the over-120-char incremental-skip conditional in
  PRReviewer.run for ruff compliance.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
---
 pr_agent/git_providers/azuredevops_provider.py | 18 +++++++++++++++++-
 pr_agent/tools/pr_reviewer.py                  |  6 +++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index 447233b436..228727137c 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -215,6 +215,8 @@ def _get_incremental_commits(self):
             return
 
         self.incremental.commits_range = self._get_commit_range()
+        if self.incremental.commits_range is None:
+            return
         candidate_paths = []
         had_errors = False
         for commit in self.incremental.commits_range:
@@ -258,18 +260,32 @@ def _get_incremental_commits(self):
     def _get_commit_range(self):
         last_review_time = _to_naive_utc(getattr(self.previous_review, "created_at", None))
         if last_review_time is None or not self.pr_commits:
-            return []
+            get_logger().info(
+                "Cannot compute incremental commit range "
+                "(missing previous review timestamp or PR commits); falling back to full review."
+            )
+            self.incremental.is_incremental = False
+            return None
         first_new_commit_index = None
+        saw_reliable_date = False
         for index in range(len(self.pr_commits) - 1, -1, -1):
             cdate = self.pr_commits[index].commit.author.date
             if cdate is None:
                 continue
+            saw_reliable_date = True
             if cdate > last_review_time:
                 self.incremental.first_new_commit = self.pr_commits[index]
                 first_new_commit_index = index
             else:
                 self.incremental.last_seen_commit = self.pr_commits[index]
                 break
+        if not saw_reliable_date:
+            get_logger().info(
+                "All PR commit author dates are missing; cannot compute incremental range. "
+                "Falling back to full review."
+            )
+            self.incremental.is_incremental = False
+            return None
         return self.pr_commits[first_new_commit_index:] if first_new_commit_index is not None else []
 
     def get_previous_review(self, *, full: bool, incremental: bool):
diff --git a/pr_agent/tools/pr_reviewer.py b/pr_agent/tools/pr_reviewer.py
index 67882a27d5..2b1f358011 100644
--- a/pr_agent/tools/pr_reviewer.py
+++ b/pr_agent/tools/pr_reviewer.py
@@ -142,7 +142,11 @@ async def run(self) -> None:
             # ticket extraction if exists
             await extract_and_cache_pr_tickets(self.git_provider, self.vars)
 
-            if self.incremental.is_incremental and hasattr(self.git_provider, "unreviewed_files_map") and not self.git_provider.unreviewed_files_map:
+            if (
+                self.incremental.is_incremental
+                and hasattr(self.git_provider, "unreviewed_files_map")
+                and not self.git_provider.unreviewed_files_map
+            ):
                 get_logger().info(f"Incremental review is enabled for {self.pr_url} but there are no new files")
                 previous_review_url = ""
                 if hasattr(self.git_provider, "previous_review") and self.git_provider.previous_review is not None:

From 5cddd81c0004bb14bc5f80f6b77b0113f93e6701 Mon Sep 17 00:00:00 2001
From: Andy Gonzales <agonzales@ipcoop.com>
Date: Fri, 8 May 2026 15:50:26 -0400
Subject: [PATCH 7/7] pr comments

---
 .../git_providers/azuredevops_provider.py     |  8 +-
 .../unittest/test_azure_devops_incremental.py | 83 ++++++++++++-------
 2 files changed, 58 insertions(+), 33 deletions(-)

diff --git a/pr_agent/git_providers/azuredevops_provider.py b/pr_agent/git_providers/azuredevops_provider.py
index 228727137c..1d05ac5a3e 100644
--- a/pr_agent/git_providers/azuredevops_provider.py
+++ b/pr_agent/git_providers/azuredevops_provider.py
@@ -53,7 +53,6 @@ class _AzureCommitAdapter:
     """Mimics PyGithub `Commit` shape (.sha, .commit.author.date, .commit.message, .parents)."""
 
     def __init__(self, raw):
-        self._raw = raw
         self.sha = raw.commit_id
         self.commit_id = raw.commit_id
         self.commit = _AzureCommitInner(raw)
@@ -219,10 +218,12 @@ def _get_incremental_commits(self):
             return
         candidate_paths = []
         had_errors = False
+        non_merge_seen = False
         for commit in self.incremental.commits_range:
             if len(commit.parents) > 1:
                 get_logger().info(f"Skipping merge commit {commit.sha}")
                 continue
+            non_merge_seen = True
             try:
                 changes_obj = self.azure_devops_client.get_changes(
                     project=self.workspace_slug,
@@ -256,6 +257,11 @@ def _get_incremental_commits(self):
                 "Failed to fetch changes for incremental commits; falling back to full review."
             )
             self.incremental.is_incremental = False
+        elif self.incremental.commits_range and not non_merge_seen:
+            get_logger().info(
+                "Incremental range only contains merge commits; falling back to full review."
+            )
+            self.incremental.is_incremental = False
 
     def _get_commit_range(self):
         last_review_time = _to_naive_utc(getattr(self.previous_review, "created_at", None))
diff --git a/tests/unittest/test_azure_devops_incremental.py b/tests/unittest/test_azure_devops_incremental.py
index 79c220a2b8..a58f2603a2 100644
--- a/tests/unittest/test_azure_devops_incremental.py
+++ b/tests/unittest/test_azure_devops_incremental.py
@@ -1,5 +1,4 @@
 import datetime as _dt
-import unittest
 from unittest.mock import MagicMock, patch
 
 from pr_agent.git_providers import AzureDevopsProvider
@@ -29,31 +28,31 @@ def _comment(body, published_date):
     return c
 
 
-class TestNaiveUtc(unittest.TestCase):
+class TestNaiveUtc:
     def test_strips_tz_from_aware(self):
         aware = _dt.datetime(2024, 1, 1, 12, 0, tzinfo=_dt.timezone.utc)
         naive = _to_naive_utc(aware)
-        self.assertIsNone(naive.tzinfo)
-        self.assertEqual(naive, _dt.datetime(2024, 1, 1, 12, 0))
+        assert naive.tzinfo is None
+        assert naive == _dt.datetime(2024, 1, 1, 12, 0)
 
     def test_passes_naive_through(self):
         naive = _dt.datetime(2024, 1, 1, 12, 0)
-        self.assertEqual(_to_naive_utc(naive), naive)
+        assert _to_naive_utc(naive) == naive
 
     def test_none_returns_none(self):
-        self.assertIsNone(_to_naive_utc(None))
+        assert _to_naive_utc(None) is None
 
 
-class TestAzureCommitAdapter(unittest.TestCase):
+class TestAzureCommitAdapter:
     def test_exposes_github_shape(self):
         date = _dt.datetime(2024, 1, 1, 12, 0, tzinfo=_dt.timezone.utc)
         raw = _raw_commit("abc123", "fix bug", date, parents=["p1"])
         adapter = _AzureCommitAdapter(raw)
-        self.assertEqual(adapter.sha, "abc123")
-        self.assertEqual(adapter.commit_id, "abc123")
-        self.assertEqual(adapter.commit.message, "fix bug")
-        self.assertIsNone(adapter.commit.author.date.tzinfo)
-        self.assertEqual(adapter.parents, ["p1"])
+        assert adapter.sha == "abc123"
+        assert adapter.commit_id == "abc123"
+        assert adapter.commit.message == "fix bug"
+        assert adapter.commit.author.date.tzinfo is None
+        assert adapter.parents == ["p1"]
 
     def test_handles_missing_author(self):
         raw = MagicMock()
@@ -62,11 +61,11 @@ def test_handles_missing_author(self):
         raw.author = None
         raw.parents = None
         adapter = _AzureCommitAdapter(raw)
-        self.assertIsNone(adapter.commit.author.date)
-        self.assertEqual(adapter.parents, [])
+        assert adapter.commit.author.date is None
+        assert adapter.parents == []
 
 
-class TestGetIncrementalCommits(unittest.TestCase):
+class TestGetIncrementalCommits:
     def _make_provider(self):
         with patch.object(
             AzureDevopsProvider, "_get_azure_devops_client",
@@ -87,8 +86,8 @@ def test_no_previous_review_disables_incremental(self):
         inc = IncrementalPR(True)
         provider.get_incremental_commits(inc)
 
-        self.assertFalse(provider.incremental.is_incremental)
-        self.assertIsNone(provider.previous_review)
+        assert provider.incremental.is_incremental is False
+        assert provider.previous_review is None
 
     def test_populates_commits_range_and_files(self):
         provider = self._make_provider()
@@ -122,15 +121,15 @@ def test_populates_commits_range_and_files(self):
         inc = IncrementalPR(True)
         provider.get_incremental_commits(inc)
 
-        self.assertTrue(provider.incremental.is_incremental)
-        self.assertEqual(len(provider.incremental.commits_range), 2)
-        self.assertEqual(provider.incremental.first_new_commit.sha, "new1")
-        self.assertEqual(provider.incremental.last_seen_commit.sha, "old1")
-        self.assertEqual(provider.incremental.last_seen_commit_sha, "old1")
-        self.assertIn("/foo.py", provider.unreviewed_files_map)
-        self.assertIn("/bar.py", provider.unreviewed_files_map)
-        self.assertNotIn("/somedir", provider.unreviewed_files_map)
-        self.assertEqual(prev.html_url, provider.get_comment_url(prev))
+        assert provider.incremental.is_incremental
+        assert len(provider.incremental.commits_range) == 2
+        assert provider.incremental.first_new_commit.sha == "new1"
+        assert provider.incremental.last_seen_commit.sha == "old1"
+        assert provider.incremental.last_seen_commit_sha == "old1"
+        assert "/foo.py" in provider.unreviewed_files_map
+        assert "/bar.py" in provider.unreviewed_files_map
+        assert "/somedir" not in provider.unreviewed_files_map
+        assert prev.html_url == provider.get_comment_url(prev)
 
     def test_skips_merge_commits(self):
         provider = self._make_provider()
@@ -151,8 +150,32 @@ def test_skips_merge_commits(self):
         provider.get_incremental_commits(IncrementalPR(True))
         provider.azure_devops_client.get_changes.assert_not_called()
 
+    def test_all_merge_commits_falls_back_to_full(self):
+        provider = self._make_provider()
+        review_time = _dt.datetime(2024, 6, 1, tzinfo=_dt.timezone.utc)
+        merge1 = _raw_commit(
+            "m1", "merge1", _dt.datetime(2024, 6, 2, tzinfo=_dt.timezone.utc),
+            parents=["a", "b"],
+        )
+        merge2 = _raw_commit(
+            "m2", "merge2", _dt.datetime(2024, 6, 3, tzinfo=_dt.timezone.utc),
+            parents=["c", "d"],
+        )
+        provider.azure_devops_client.get_pull_request_commits = MagicMock(
+            return_value=[merge2, merge1]
+        )
+        provider.get_issue_comments = MagicMock(
+            return_value=[_comment("## PR Reviewer Guide", review_time)]
+        )
+        provider.azure_devops_client.get_changes = MagicMock()
 
-class TestPrReviewerGuard(unittest.TestCase):
+        provider.get_incremental_commits(IncrementalPR(True))
+
+        assert provider.incremental.is_incremental is False
+        provider.azure_devops_client.get_changes.assert_not_called()
+
+
+class TestPrReviewerGuard:
     def test_can_run_returns_false_when_commits_range_none(self):
         from pr_agent.tools.pr_reviewer import PRReviewer
         reviewer = PRReviewer.__new__(PRReviewer)
@@ -162,8 +185,4 @@ def test_can_run_returns_false_when_commits_range_none(self):
         # incremental.commits_range stays None — provider has the method but didn't populate it.
         reviewer.git_provider = MagicMock(spec=["get_incremental_commits"])
         # Should not raise NoneType len() error.
-        self.assertFalse(reviewer._can_run_incremental_review())
-
-
-if __name__ == "__main__":
-    unittest.main()
+        assert reviewer._can_run_incremental_review() is False