diff --git a/code_review_graph/changes.py b/code_review_graph/changes.py
index 2165fba1..0aa6f595 100644
--- a/code_review_graph/changes.py
+++ b/code_review_graph/changes.py
@@ -420,6 +420,19 @@ def analyze_changes(
             for key, ranges in parse_diff_ranges(repo_root, base).items()
         }
 
+    # The affected-flows lookup and the no-ranges fallback match
+    # changed_files against nodes.file_path, which stores absolute
+    # normalized paths. CLI callers pass repo-relative diff paths, so an
+    # exact IN (...) match finds no nodes and detect-changes reports
+    # "0 affected flow(s)" even when the MCP tool reports hundreds on the
+    # same input (#848). Remap the same way as changed_ranges keys;
+    # already-absolute inputs (MCP) pass through pathlib joining unchanged.
+    if repo_root is not None:
+        _root = Path(repo_root)
+        changed_files = [
+            normalize_file_path(_root / fp) for fp in changed_files
+        ]
+
     # Map changes to nodes.
     if changed_ranges:
         changed_nodes = map_changes_to_nodes(store, changed_ranges)
diff --git a/tests/test_changes.py b/tests/test_changes.py
index c0d4f75f..b1547371 100644
--- a/tests/test_changes.py
+++ b/tests/test_changes.py
@@ -403,6 +403,35 @@ def test_analyze_changes_with_flows(self):
         )
         assert len(result["affected_flows"]) >= 1
 
+    def test_analyze_changes_flows_with_relative_cli_paths(self):
+        """Relative changed_files still hit flows stored under absolute paths.
+
+        Real builds store absolute node paths while the CLI passes
+        repo-relative diff paths, which made detect-changes report
+        "0 affected flow(s)" where the MCP tool reported them (#848).
+        """
+        repo_root = "/repo" if not Path("C:/").exists() else "C:/repo"
+        routes_abs = f"{repo_root}/routes.py"
+        services_abs = f"{repo_root}/services.py"
+        self._add_func("handler", path=routes_abs, line_start=1, line_end=10)
+        self._add_func("service", path=services_abs, line_start=1, line_end=10)
+        self._add_call(
+            f"{routes_abs}::handler",
+            f"{services_abs}::service",
+            routes_abs,
+        )
+
+        flows = trace_flows(self.store)
+        store_flows(self.store, flows)
+
+        result = analyze_changes(
+            self.store,
+            changed_files=["services.py"],
+            changed_ranges={services_abs: [(1, 10)]},
+            repo_root=repo_root,
+        )
+        assert len(result["affected_flows"]) >= 1
+
     def test_analyze_changes_review_priorities_ordered(self):
         """Review priorities are ordered by descending risk score."""
         # Create several functions with varying risk levels.