diff --git a/clang/docs/ScalableStaticAnalysis/user-docs/SourceEditGeneration.md b/clang/docs/ScalableStaticAnalysis/user-docs/SourceEditGeneration.md
index af7fc7f..a0b52b3 100644
--- a/clang/docs/ScalableStaticAnalysis/user-docs/SourceEditGeneration.md
+++ b/clang/docs/ScalableStaticAnalysis/user-docs/SourceEditGeneration.md
@@ -65,3 +65,19 @@
 
 The transformation report can be consumed by any SARIF viewer.
 
+
+## Merging transformation reports
+
+A transformation report covers one translation unit.
+`clang-ssaf-merge-transformation-report` merges the reports of the
+translation units of a link unit into one:
+
+```console
+$ clang-ssaf-merge-transformation-report foo.sarif bar.sarif -o prg.sarif
+```
+
+The inputs must come from the same transformation. A finding that several
+inputs share, such as one in a header that both translation units include,
+is reported once, and the result does not depend on the order of the
+inputs. A merged report can be merged again.
+
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-artifact-index.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-artifact-index.sarif
new file mode 100644
index 0000000..893cd17
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-artifact-index.sarif
@@ -0,0 +1,71 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 120,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/a.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 5,
+                  "uri": "file:///src/a.cpp"
+                },
+                "region": {
+                  "endColumn": 5,
+                  "endLine": 1,
+                  "startColumn": 1,
+                  "startLine": 1
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "declarator spelled through a macro is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-rule-index.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-rule-index.sarif
new file mode 100644
index 0000000..093a89d
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/bad-rule-index.sarif
@@ -0,0 +1,71 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 120,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/a.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0,
+                  "uri": "file:///src/a.cpp"
+                },
+                "region": {
+                  "endColumn": 5,
+                  "endLine": 1,
+                  "startColumn": 1,
+                  "startLine": 1
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "declarator spelled through a macro is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 3
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/empty.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/empty.sarif
new file mode 100644
index 0000000..944201f
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/empty.sarif
@@ -0,0 +1,21 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [],
+      "columnKind": "unicodeCodePoints",
+      "results": [],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/other-transformation.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/other-transformation.sarif
new file mode 100644
index 0000000..2a950fd6
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/other-transformation.sarif
@@ -0,0 +1,21 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [],
+      "columnKind": "unicodeCodePoints",
+      "results": [],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (fix-noexcept)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-a.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-a.sarif
new file mode 100644
index 0000000..24a766b
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-a.sarif
@@ -0,0 +1,106 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 120,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/a.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        },
+        {
+          "length": 60,
+          "location": {
+            "index": 1,
+            "uri": "file:///src/shared.h"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 1,
+                  "uri": "file:///src/shared.h"
+                },
+                "region": {
+                  "endColumn": 12,
+                  "endLine": 3,
+                  "startColumn": 8,
+                  "startLine": 3
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "multi-level pointer indirection is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        },
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0,
+                  "uri": "file:///src/a.cpp"
+                },
+                "region": {
+                  "endColumn": 7,
+                  "endLine": 7,
+                  "startColumn": 3,
+                  "startLine": 7
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "declarator spelled through a macro is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-b.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-b.sarif
new file mode 100644
index 0000000..40d17d8
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-b.sarif
@@ -0,0 +1,118 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 60,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/shared.h"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        },
+        {
+          "length": 90,
+          "location": {
+            "index": 1,
+            "uri": "file:///src/b.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0,
+                  "uri": "file:///src/shared.h"
+                },
+                "region": {
+                  "endColumn": 12,
+                  "endLine": 3,
+                  "startColumn": 8,
+                  "startLine": 3
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "multi-level pointer indirection is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 1
+        },
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 1,
+                  "uri": "file:///src/b.cpp"
+                },
+                "region": {
+                  "endColumn": 5,
+                  "endLine": 5,
+                  "startColumn": 1,
+                  "startLine": 5
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "other finding"
+          },
+          "ruleId": "cpp-bounded-buffers-other",
+          "ruleIndex": 0
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-other",
+              "name": ""
+            },
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-c.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-c.sarif
new file mode 100644
index 0000000..51086f4
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-c.sarif
@@ -0,0 +1,71 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 40,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/c.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0,
+                  "uri": "file:///src/c.cpp"
+                },
+                "region": {
+                  "endColumn": 9,
+                  "endLine": 2,
+                  "startColumn": 5,
+                  "startLine": 2
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "multi-level pointer indirection is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-clang-order.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-clang-order.sarif
new file mode 100644
index 0000000..8124ebb
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/tu-clang-order.sarif
@@ -0,0 +1,124 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [
+        {
+          "length": 120,
+          "location": {
+            "index": 1,
+            "uri": "file:///src/a.cpp"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        },
+        {
+          "length": 60,
+          "location": {
+            "index": 0,
+            "uri": "file:///src/shared.h"
+          },
+          "mimeType": "text/plain",
+          "roles": [
+            "resultFile"
+          ]
+        }
+      ],
+      "columnKind": "unicodeCodePoints",
+      "results": [
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0
+                },
+                "region": {
+                  "endColumn": 12,
+                  "endLine": 3,
+                  "startColumn": 8,
+                  "startLine": 3
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "multi-level pointer indirection is not yet rewritten"
+          },
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        },
+        {
+          "level": "note",
+          "locations": [
+            {
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 1,
+                  "uri": "file:///src/a.cpp"
+                },
+                "region": {
+                  "endColumn": 7,
+                  "endLine": 7,
+                  "startColumn": 3,
+                  "startLine": 7
+                }
+              }
+            }
+          ],
+          "message": {
+            "text": "declarator spelled through a macro is not yet rewritten"
+          },
+          "relatedLocations": [
+            {
+              "id": 1,
+              "message": {
+                "text": "the macro"
+              },
+              "physicalLocation": {
+                "artifactLocation": {
+                  "index": 0
+                },
+                "region": {
+                  "endColumn": 5,
+                  "endLine": 2,
+                  "startColumn": 1,
+                  "startLine": 2
+                }
+              }
+            }
+          ],
+          "ruleId": "cpp-bounded-buffers-skipped",
+          "ruleIndex": 0
+        }
+      ],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [
+            {
+              "defaultConfiguration": {
+                "enabled": true,
+                "level": "warning",
+                "rank": -1
+              },
+              "fullDescription": {
+                "text": ""
+              },
+              "id": "cpp-bounded-buffers-skipped",
+              "name": ""
+            }
+          ],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/two-runs.sarif b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/two-runs.sarif
new file mode 100644
index 0000000..6fc4646b
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/Inputs/two-runs.sarif
@@ -0,0 +1,36 @@
+{
+  "$schema": "https://docs.oasis-open.org/sarif/sarif/v2.1.0/cos02/schemas/sarif-schema-2.1.0.json",
+  "runs": [
+    {
+      "artifacts": [],
+      "columnKind": "unicodeCodePoints",
+      "results": [],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [],
+          "version": "24.0.0git"
+        }
+      }
+    },
+    {
+      "artifacts": [],
+      "columnKind": "unicodeCodePoints",
+      "results": [],
+      "tool": {
+        "driver": {
+          "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+          "informationUri": "https://clang.llvm.org/docs/UsersManual.html",
+          "language": "en-US",
+          "name": "clang-ssaf",
+          "rules": [],
+          "version": "24.0.0git"
+        }
+      }
+    }
+  ],
+  "version": "2.1.0"
+}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/clang-artifact-order.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/clang-artifact-order.test
new file mode 100644
index 0000000..67de8eb
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/clang-artifact-order.test
@@ -0,0 +1,23 @@
+// clang lists a run's artifacts in URI order but numbers them in the order
+// they were first referred to, and its results refer to them by that number.
+// A location that names its artifact only by number, in a result or in a
+// related location, is placed by the artifact's own index.
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-clang-order.sarif \
+// RUN:   %S/Inputs/tu-b.sarif -o %t/merged.sarif
+// RUN: FileCheck %s --input-file=%t/merged.sarif
+// RUN: grep 'multi-level pointer indirection' %t/merged.sarif | count 1
+
+// CHECK:      "results": [
+// CHECK:        "index": 0,
+// CHECK-NEXT:   "uri": "file:///src/a.cpp"
+// CHECK:        "text": "declarator spelled through a macro is not yet rewritten"
+// CHECK:      "relatedLocations": [
+// CHECK:        "index": 2,
+// CHECK-NEXT:   "uri": "file:///src/shared.h"
+// CHECK:        "index": 1,
+// CHECK-NEXT:   "uri": "file:///src/b.cpp"
+// CHECK:        "index": 2,
+// CHECK-NEXT:   "uri": "file:///src/shared.h"
+// CHECK:        "text": "multi-level pointer indirection is not yet rewritten"
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/cli-errors.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/cli-errors.test
new file mode 100644
index 0000000..93a2618
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/cli-errors.test
@@ -0,0 +1,87 @@
+// Tests for clang-ssaf-merge-transformation-report errors.
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// ============================================================================
+// CLI error: no arguments
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=NO-ARGS
+// NO-ARGS: clang-ssaf-merge-transformation-report{{(\.exe)?}}: Not enough positional command line arguments specified!
+
+// ============================================================================
+// CLI error: missing -o
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=NO-OUTPUT
+// NO-OUTPUT: clang-ssaf-merge-transformation-report{{(\.exe)?}}: for the -o option: must be specified at least once!
+
+// ============================================================================
+// Error: nonexistent input
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report %t/missing.sarif \
+// RUN:   -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=MISSING -DPATH=%t/missing.sarif
+// MISSING: clang-ssaf-merge-transformation-report: error: failed to read '[[PATH]]': {{.*}}
+
+// ============================================================================
+// Error: input is not JSON
+// ============================================================================
+
+// RUN: echo 'not json' > %t/not-json.sarif
+// RUN: not clang-ssaf-merge-transformation-report %t/not-json.sarif \
+// RUN:   -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=NOT-JSON -DPATH=%t/not-json.sarif
+// NOT-JSON: clang-ssaf-merge-transformation-report: error: failed to parse '[[PATH]]': {{.*}}
+
+// ============================================================================
+// Error: input does not have exactly one run
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report %S/Inputs/two-runs.sarif \
+// RUN:   -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=TWO-RUNS
+// TWO-RUNS: clang-ssaf-merge-transformation-report: error: '{{.*}}two-runs.sarif' is not a SARIF log with exactly one run
+
+// ============================================================================
+// Error: inputs from different transformations
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/other-transformation.sarif -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=OTHER
+// OTHER: clang-ssaf-merge-transformation-report: error: '{{.*}}other-transformation.sarif' reports on 'clang ScalableStaticAnalysisFramework source transformation (fix-noexcept)', not on 'clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)'
+
+// ============================================================================
+// Error: a result refers to a rule its run does not define
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report \
+// RUN:   %S/Inputs/bad-rule-index.sarif -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=BAD-RULE
+// BAD-RULE: clang-ssaf-merge-transformation-report: error: '{{.*}}bad-rule-index.sarif': a result refers to rule 3, which its run does not define
+
+// ============================================================================
+// Error: a location refers to an artifact its run does not define
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report \
+// RUN:   %S/Inputs/bad-artifact-index.sarif -o %t/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=BAD-ARTIFACT
+// BAD-ARTIFACT: clang-ssaf-merge-transformation-report: error: '{{.*}}bad-artifact-index.sarif': a location refers to artifact 5, which its run does not define
+
+// ============================================================================
+// Error: the output cannot be written
+// ============================================================================
+
+// RUN: not clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   -o %t/no-such-dir/out.sarif 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CANNOT-WRITE -DPATH=%t/no-such-dir/out.sarif
+// CANNOT-WRITE: clang-ssaf-merge-transformation-report: error: failed to write '[[PATH]]': {{.*}}
+
+// No error leaves an output behind.
+// RUN: not ls %t/out.sarif
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/empty.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/empty.test
new file mode 100644
index 0000000..f2a2fc0
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/empty.test
@@ -0,0 +1,16 @@
+// Reports without results merge into a report without results, and add
+// nothing to a report that has some.
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/empty.sarif \
+// RUN:   %S/Inputs/empty.sarif -o %t/empty.sarif
+// RUN: FileCheck %s --input-file=%t/empty.sarif
+// CHECK: "artifacts": [],
+// CHECK: "results": [],
+// CHECK: "rules": [],
+
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   -o %t/a.sarif
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/empty.sarif \
+// RUN:   %S/Inputs/tu-a.sarif -o %t/empty-a.sarif
+// RUN: diff %t/a.sarif %t/empty-a.sarif
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/help.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/help.test
new file mode 100644
index 0000000..8014d652b
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/help.test
@@ -0,0 +1,19 @@
+// Test clang-ssaf-merge-transformation-report help option
+
+// RUN: clang-ssaf-merge-transformation-report --help-list-hidden \
+// RUN:           | FileCheck %s --match-full-lines
+
+// CHECK:      OVERVIEW: SSAF Transformation Report Merger
+// CHECK-EMPTY:
+// CHECK-NEXT: USAGE: clang-ssaf-merge-transformation-report{{(\.exe)?}} [options] <input.sarif>...
+// CHECK-EMPTY:
+// CHECK-NEXT: OPTIONS:
+// CHECK-NEXT:   -h                  - Alias for --help
+// CHECK-NEXT:   --help              - Display available options (--help-hidden for more)
+// CHECK-NEXT:   --help-hidden       - Display all available options
+// CHECK-NEXT:   --help-list         - Display list of available options (--help-list-hidden for more)
+// CHECK-NEXT:   --help-list-hidden  - Display list of all available options
+// CHECK-NEXT:   -o <path>           - Output file path
+// CHECK-NEXT:   --print-all-options - Print all option values after command line parsing
+// CHECK-NEXT:   --print-options     - Print non-default options after command line parsing
+// CHECK-NEXT:   --version           - Display the version of this program
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/merge.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/merge.test
new file mode 100644
index 0000000..12b6832
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/merge.test
@@ -0,0 +1,51 @@
+// Two reports that both carry a finding in a shared header, under different
+// rule and artifact indices, merge into one run.
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/tu-b.sarif -o %t/merged.sarif
+// RUN: FileCheck %s --input-file=%t/merged.sarif
+
+// '-' writes the report to stdout.
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/tu-b.sarif -o - > %t/stdout.sarif
+// RUN: diff %t/merged.sarif %t/stdout.sarif
+
+// The artifacts of both runs, once each and numbered in URI order.
+// CHECK:      "artifacts": [
+// CHECK:        "index": 0,
+// CHECK-NEXT:   "uri": "file:///src/a.cpp"
+// CHECK:        "index": 1,
+// CHECK-NEXT:   "uri": "file:///src/b.cpp"
+// CHECK:        "index": 2,
+// CHECK-NEXT:   "uri": "file:///src/shared.h"
+
+// The results in location order, each pointing into the merged rules and
+// artifacts. The header's finding is kept once.
+// CHECK:      "results": [
+// CHECK:        "index": 0,
+// CHECK-NEXT:   "uri": "file:///src/a.cpp"
+// CHECK:        "ruleId": "cpp-bounded-buffers-skipped",
+// CHECK-NEXT:   "ruleIndex": 1
+// CHECK:        "index": 1,
+// CHECK-NEXT:   "uri": "file:///src/b.cpp"
+// CHECK:        "ruleId": "cpp-bounded-buffers-other",
+// CHECK-NEXT:   "ruleIndex": 0
+// CHECK:        "index": 2,
+// CHECK-NEXT:   "uri": "file:///src/shared.h"
+// CHECK:        "text": "multi-level pointer indirection is not yet rewritten"
+// CHECK:        "ruleId": "cpp-bounded-buffers-skipped",
+// CHECK-NEXT:   "ruleIndex": 1
+// CHECK-NOT:    "text": "multi-level pointer indirection is not yet rewritten"
+
+// The rules of both runs, once each and in id order, under the driver of the
+// first input.
+// CHECK:      "tool": {
+// CHECK:        "fullName": "clang ScalableStaticAnalysisFramework source transformation (cpp-bounded-buffers)",
+// CHECK:        "name": "clang-ssaf",
+// CHECK:        "rules": [
+// CHECK:          "id": "cpp-bounded-buffers-other",
+// CHECK:          "id": "cpp-bounded-buffers-skipped",
+// CHECK-NOT:      "id":
+// CHECK:        "version": "24.0.0git"
+// CHECK:      "version": "2.1.0"
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/nested.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/nested.test
new file mode 100644
index 0000000..47db227
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/nested.test
@@ -0,0 +1,16 @@
+// A merged report merges again like the reports it was made from, so that an
+// archive's report can feed the report of the program it is linked into.
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/tu-b.sarif -o %t/ab.sarif
+// RUN: clang-ssaf-merge-transformation-report %t/ab.sarif \
+// RUN:   %S/Inputs/tu-c.sarif -o %t/ab-c.sarif
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/tu-b.sarif %S/Inputs/tu-c.sarif -o %t/abc.sarif
+// RUN: diff %t/ab-c.sarif %t/abc.sarif
+
+// Merging a report with itself adds nothing.
+// RUN: clang-ssaf-merge-transformation-report %t/ab.sarif %t/ab.sarif \
+// RUN:   -o %t/ab-ab.sarif
+// RUN: diff %t/ab.sarif %t/ab-ab.sarif
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/order-invariance.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/order-invariance.test
new file mode 100644
index 0000000..07986cd
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/order-invariance.test
@@ -0,0 +1,8 @@
+// The merged report does not depend on the order of the inputs.
+
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-a.sarif \
+// RUN:   %S/Inputs/tu-b.sarif %S/Inputs/tu-c.sarif -o %t/abc.sarif
+// RUN: clang-ssaf-merge-transformation-report %S/Inputs/tu-c.sarif \
+// RUN:   %S/Inputs/tu-b.sarif %S/Inputs/tu-a.sarif -o %t/cba.sarif
+// RUN: diff %t/abc.sarif %t/cba.sarif
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/plugin-reports.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/plugin-reports.test
new file mode 100644
index 0000000..fd62ce4
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/plugin-reports.test
@@ -0,0 +1,47 @@
+// Reports written by clang for two translation units merge into one, and a
+// report given twice contributes its findings once.
+
+// REQUIRES: plugins
+
+// RUN: rm -rf %t && split-file %s %t
+// DEFINE: %{transform} = %clang_cc1 \
+// DEFINE:   -load %llvmshlibdir/SSAFTestTransformationPlugin%pluginext \
+// DEFINE:   --ssaf-source-transformation=test-transformation \
+// DEFINE:   --ssaf-global-scope-analysis-result=%S/../source-edit-generation/Inputs/two-function-suite.json \
+// DEFINE:   --ssaf-link-unit-id=lu -emit-obj
+// RUN: %{transform} --ssaf-compilation-unit-id=a --ssaf-src-edit-file=%t/a.yaml \
+// RUN:   --ssaf-transformation-report-file=%t/a.sarif -o %t/a.o %t/a.cpp
+// RUN: %{transform} --ssaf-compilation-unit-id=b --ssaf-src-edit-file=%t/b.yaml \
+// RUN:   --ssaf-transformation-report-file=%t/b.sarif -o %t/b.o %t/b.cpp
+
+// RUN: clang-ssaf-merge-transformation-report %t/a.sarif %t/b.sarif \
+// RUN:   %t/a.sarif -o %t/merged.sarif
+// RUN: FileCheck %s --input-file=%t/merged.sarif
+// RUN: grep '"text": "visited alpha"' %t/merged.sarif | count 1
+
+// CHECK:      "artifacts": [
+// CHECK:        "index": 0,
+// CHECK-NEXT:   "uri": "file://{{.*}}a.cpp"
+// CHECK:        "index": 1,
+// CHECK-NEXT:   "uri": "file://{{.*}}b.cpp"
+// CHECK:      "results": [
+// CHECK:        "index": 0,
+// CHECK-NEXT:   "uri": "file://{{.*}}a.cpp"
+// CHECK:        "text": "visited alpha"
+// CHECK:        "ruleId": "test-touches-function",
+// CHECK-NEXT:   "ruleIndex": 0
+// CHECK:        "index": 1,
+// CHECK-NEXT:   "uri": "file://{{.*}}b.cpp"
+// CHECK:        "text": "visited beta"
+// CHECK:        "ruleId": "test-touches-function",
+// CHECK-NEXT:   "ruleIndex": 0
+// CHECK:        "name": "clang-ssaf",
+// CHECK:        "rules": [
+// CHECK:          "id": "test-touches-function",
+// CHECK-NOT:      "id":
+
+//--- a.cpp
+void alpha() {}
+
+//--- b.cpp
+void beta() {}
diff --git a/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/version.test b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/version.test
new file mode 100644
index 0000000..94b7e45
--- /dev/null
+++ b/clang/test/Analysis/Scalable/ssaf-merge-transformation-report/version.test
@@ -0,0 +1,5 @@
+// Test clang-ssaf-merge-transformation-report version
+
+// RUN: clang-ssaf-merge-transformation-report --version | FileCheck %s
+
+// CHECK: clang-ssaf-merge-transformation-report 0.1
diff --git a/clang/test/CMakeLists.txt b/clang/test/CMakeLists.txt
index 72a4f27..793bed1 100644
--- a/clang/test/CMakeLists.txt
+++ b/clang/test/CMakeLists.txt
@@ -107,6 +107,7 @@
   clang-ssaf-analyzer
   clang-ssaf-format
   clang-ssaf-linker
+  clang-ssaf-merge-transformation-report
   clang-ssaf-src-edit-merge
   clang-sycl-linker
   diagtool
diff --git a/clang/tools/CMakeLists.txt b/clang/tools/CMakeLists.txt
index 1824896..c38efad 100644
--- a/clang/tools/CMakeLists.txt
+++ b/clang/tools/CMakeLists.txt
@@ -18,6 +18,7 @@
 add_clang_subdirectory(clang-ssaf-analyzer)
 add_clang_subdirectory(clang-ssaf-format)
 add_clang_subdirectory(clang-ssaf-linker)
+add_clang_subdirectory(clang-ssaf-merge-transformation-report)
 if(NOT WIN32)
   add_clang_subdirectory(clang-ssaf-orchestrator-make)
 endif()
diff --git a/clang/tools/clang-ssaf-merge-transformation-report/CMakeLists.txt b/clang/tools/clang-ssaf-merge-transformation-report/CMakeLists.txt
new file mode 100644
index 0000000..d243b07
--- /dev/null
+++ b/clang/tools/clang-ssaf-merge-transformation-report/CMakeLists.txt
@@ -0,0 +1,12 @@
+set(LLVM_LINK_COMPONENTS
+  Support
+  )
+
+add_clang_tool(clang-ssaf-merge-transformation-report
+  MergeTransformationReport.cpp
+  )
+
+clang_target_link_libraries(clang-ssaf-merge-transformation-report
+  PRIVATE
+  clangScalableStaticAnalysisTool
+  )
diff --git a/clang/tools/clang-ssaf-merge-transformation-report/MergeTransformationReport.cpp b/clang/tools/clang-ssaf-merge-transformation-report/MergeTransformationReport.cpp
new file mode 100644
index 0000000..3ca4b22
--- /dev/null
+++ b/clang/tools/clang-ssaf-merge-transformation-report/MergeTransformationReport.cpp
@@ -0,0 +1,386 @@
+//===- MergeTransformationReport.cpp - SSAF Report Merge Tool -------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the tool that merges SARIF transformation reports, as
+//  written by clang's --ssaf-transformation-report-file or by this tool, into
+//  one report. Every input run numbers its rules and artifacts on its own, so
+//  results are renumbered against the merged run, and identical results, such
+//  as a finding in a header that several translation units include, are kept
+//  once. An artifact is numbered by its own location index where it has one,
+//  since clang lists artifacts in URI order but numbers them in the order they
+//  were first referred to.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/ScalableStaticAnalysis/Tool/Utils.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/JSON.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstdint>
+#include <map>
+#include <optional>
+#include <set>
+#include <string>
+#include <tuple>
+#include <vector>
+
+using namespace llvm;
+using namespace clang::ssaf;
+
+namespace {
+
+//===----------------------------------------------------------------------===//
+// Command-Line Options
+//===----------------------------------------------------------------------===//
+
+cl::OptionCategory MergeTransformationReportCategory(
+    "clang-ssaf-merge-transformation-report options");
+
+cl::list<std::string> InputPaths(cl::Positional, cl::desc("<input.sarif>..."),
+                                 cl::OneOrMore,
+                                 cl::cat(MergeTransformationReportCategory));
+
+cl::opt<std::string> OutputPath("o", cl::desc("Output file path"),
+                                cl::value_desc("path"), cl::Required,
+                                cl::cat(MergeTransformationReportCategory));
+
+//===----------------------------------------------------------------------===//
+// Error Messages
+//===----------------------------------------------------------------------===//
+
+namespace ErrorMessages {
+
+constexpr const char *CannotRead = "failed to read '{0}': {1}";
+
+constexpr const char *CannotParse = "failed to parse '{0}': {1}";
+
+constexpr const char *NotOneRun =
+    "'{0}' is not a SARIF log with exactly one run";
+
+constexpr const char *OtherTransformation =
+    "'{0}' reports on '{1}', not on '{2}'";
+
+constexpr const char *UnknownRule =
+    "'{0}': a result refers to rule {1}, which its run does not define";
+
+constexpr const char *UnknownArtifact =
+    "'{0}': a location refers to artifact {1}, which its run does not define";
+
+constexpr const char *CannotWrite = "failed to write '{0}': {1}";
+
+} // namespace ErrorMessages
+
+//===----------------------------------------------------------------------===//
+// Reading and Writing
+//===----------------------------------------------------------------------===//
+
+json::Value readLog(StringRef Path) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> Buffer = MemoryBuffer::getFile(Path);
+  if (!Buffer) {
+    fail(ErrorMessages::CannotRead, Path, Buffer.getError().message());
+  }
+  Expected<json::Value> Log = json::parse((*Buffer)->getBuffer());
+  if (!Log) {
+    fail(ErrorMessages::CannotParse, Path, toString(Log.takeError()));
+  }
+  return std::move(*Log);
+}
+
+json::Object &getRun(json::Value &Log, StringRef Path) {
+  json::Object *Root = Log.getAsObject();
+  json::Array *Runs = Root ? Root->getArray("runs") : nullptr;
+  if (!Runs || Runs->size() != 1 || !Runs->front().getAsObject()) {
+    fail(ErrorMessages::NotOneRun, Path);
+  }
+  return *Runs->front().getAsObject();
+}
+
+void writeLog(const json::Value &Log, StringRef Path) {
+  std::error_code EC;
+  ToolOutputFile Out(Path, EC, sys::fs::OF_Text);
+  if (EC) {
+    fail(ErrorMessages::CannotWrite, Path, EC.message());
+  }
+  Out.os() << formatv("{0:2}", Log) << "\n";
+  Out.os().flush();
+  if (Out.os().has_error()) {
+    fail(ErrorMessages::CannotWrite, Path, Out.os().error().message());
+  }
+  Out.keep();
+}
+
+StringRef getString(const json::Object *Object, StringRef Key) {
+  if (!Object) {
+    return "";
+  }
+  return Object->getString(Key).value_or("");
+}
+
+json::Object *getArtifactLocation(json::Value &Location) {
+  json::Object *Object = Location.getAsObject();
+  json::Object *Physical =
+      Object ? Object->getObject("physicalLocation") : nullptr;
+  return Physical ? Physical->getObject("artifactLocation") : nullptr;
+}
+
+/// Returns a copy of \p Object without the members named in \p Excluded.
+json::Object copyExcept(const json::Object &Object,
+                        ArrayRef<StringRef> Excluded) {
+  json::Object Copy;
+  for (const auto &[Key, Value] : Object) {
+    if (!is_contained(Excluded, StringRef(Key))) {
+      Copy[Key] = Value;
+    }
+  }
+  return Copy;
+}
+
+//===----------------------------------------------------------------------===//
+// Merging
+//===----------------------------------------------------------------------===//
+
+/// A result whose rule and artifacts are named by id and URI rather than by
+/// index, so that results from different runs compare equal.
+struct Finding {
+  std::string Uri;
+  int64_t Line;
+  int64_t Column;
+  std::string RuleId;
+  std::string Message;
+  std::string Serialized;
+  json::Object Result;
+
+  bool operator<(const Finding &Other) const {
+    return std::tie(Uri, Line, Column, RuleId, Message, Serialized) <
+           std::tie(Other.Uri, Other.Line, Other.Column, Other.RuleId,
+                    Other.Message, Other.Serialized);
+  }
+};
+
+class ReportMerger {
+public:
+  void add(json::Value Log, StringRef Path);
+  json::Value takeMerged();
+
+private:
+  void addFinding(json::Object Result);
+
+  bool HasInput = false;
+  json::Object Root;
+  json::Object Run;
+  json::Object Tool;
+  json::Object Driver;
+  std::map<std::string, json::Value> Rules;
+  std::map<std::string, json::Value> Artifacts;
+  std::set<std::string> Seen;
+  std::vector<Finding> Findings;
+};
+
+void ReportMerger::add(json::Value Log, StringRef Path) {
+  json::Object &InputRun = getRun(Log, Path);
+  const json::Object *InputTool = InputRun.getObject("tool");
+  const json::Object *InputDriver =
+      InputTool ? InputTool->getObject("driver") : nullptr;
+
+  if (!HasInput) {
+    HasInput = true;
+    Root = copyExcept(*Log.getAsObject(), {"runs"});
+    Run = copyExcept(InputRun, {"artifacts", "results", "tool"});
+    if (InputTool) {
+      Tool = copyExcept(*InputTool, {"driver"});
+    }
+    if (InputDriver) {
+      Driver = copyExcept(*InputDriver, {"rules"});
+    }
+  } else if (getString(InputDriver, "name") != getString(&Driver, "name") ||
+             getString(InputDriver, "fullName") !=
+                 getString(&Driver, "fullName")) {
+    fail(ErrorMessages::OtherTransformation, Path,
+         getString(InputDriver, "fullName"), getString(&Driver, "fullName"));
+  }
+
+  std::vector<std::string> RuleIds;
+  if (const json::Array *InputRules =
+          InputDriver ? InputDriver->getArray("rules") : nullptr) {
+    for (const json::Value &Rule : *InputRules) {
+      std::string Id = getString(Rule.getAsObject(), "id").str();
+      Rules.try_emplace(Id, Rule);
+      RuleIds.push_back(std::move(Id));
+    }
+  }
+
+  std::map<int64_t, std::string> Uris;
+  if (const json::Array *InputArtifacts = InputRun.getArray("artifacts")) {
+    for (auto [Position, Artifact] : enumerate(*InputArtifacts)) {
+      const json::Object *Object = Artifact.getAsObject();
+      const json::Object *Location =
+          Object ? Object->getObject("location") : nullptr;
+      std::string Uri = getString(Location, "uri").str();
+      int64_t Index = static_cast<int64_t>(Position);
+      if (Location) {
+        Index = Location->getInteger("index").value_or(Index);
+      }
+      Artifacts.try_emplace(Uri, Artifact);
+      Uris[Index] = std::move(Uri);
+    }
+  }
+
+  json::Array *Results = InputRun.getArray("results");
+  if (!Results) {
+    return;
+  }
+  for (json::Value &Value : *Results) {
+    json::Object *Result = Value.getAsObject();
+    if (!Result) {
+      continue;
+    }
+    if (std::optional<int64_t> Index = Result->getInteger("ruleIndex")) {
+      if (*Index < 0 || *Index >= static_cast<int64_t>(RuleIds.size())) {
+        fail(ErrorMessages::UnknownRule, Path, *Index);
+      }
+      Result->try_emplace("ruleId", RuleIds[*Index]);
+      Result->erase("ruleIndex");
+    }
+    for (StringRef Key : {"locations", "relatedLocations"}) {
+      json::Array *Locations = Result->getArray(Key);
+      if (!Locations) {
+        continue;
+      }
+      for (json::Value &Location : *Locations) {
+        json::Object *Artifact = getArtifactLocation(Location);
+        if (!Artifact) {
+          continue;
+        }
+        if (std::optional<int64_t> Index = Artifact->getInteger("index")) {
+          auto Uri = Uris.find(*Index);
+          if (Uri == Uris.end()) {
+            fail(ErrorMessages::UnknownArtifact, Path, *Index);
+          }
+          Artifact->try_emplace("uri", Uri->second);
+          Artifact->erase("index");
+        }
+      }
+    }
+    addFinding(std::move(*Result));
+  }
+}
+
+void ReportMerger::addFinding(json::Object Result) {
+  json::Value Value(std::move(Result));
+  Finding F;
+  F.Serialized = formatv("{0}", Value);
+  if (!Seen.insert(F.Serialized).second) {
+    return;
+  }
+  json::Object &Object = *Value.getAsObject();
+  F.Line = 0;
+  F.Column = 0;
+  if (json::Array *Locations = Object.getArray("locations");
+      Locations && !Locations->empty()) {
+    F.Uri = getString(getArtifactLocation(Locations->front()), "uri").str();
+    const json::Object *Location = Locations->front().getAsObject();
+    const json::Object *Physical =
+        Location ? Location->getObject("physicalLocation") : nullptr;
+    if (const json::Object *Region =
+            Physical ? Physical->getObject("region") : nullptr) {
+      F.Line = Region->getInteger("startLine").value_or(0);
+      F.Column = Region->getInteger("startColumn").value_or(0);
+    }
+  }
+  F.RuleId = getString(&Object, "ruleId").str();
+  F.Message = getString(Object.getObject("message"), "text").str();
+  F.Result = std::move(Object);
+  Findings.push_back(std::move(F));
+}
+
+json::Value ReportMerger::takeMerged() {
+  std::map<std::string, int64_t> RuleIndex;
+  json::Array MergedRules;
+  for (auto &[Id, Rule] : Rules) {
+    RuleIndex[Id] = MergedRules.size();
+    MergedRules.push_back(std::move(Rule));
+  }
+
+  std::map<std::string, int64_t> ArtifactIndex;
+  json::Array MergedArtifacts;
+  for (auto &[Uri, Artifact] : Artifacts) {
+    int64_t Index = MergedArtifacts.size();
+    ArtifactIndex[Uri] = Index;
+    if (json::Object *Object = Artifact.getAsObject()) {
+      if (json::Object *Location = Object->getObject("location")) {
+        (*Location)["index"] = Index;
+      }
+    }
+    MergedArtifacts.push_back(std::move(Artifact));
+  }
+
+  llvm::sort(Findings);
+  json::Array MergedResults;
+  for (Finding &F : Findings) {
+    auto Rule = RuleIndex.find(F.RuleId);
+    if (Rule != RuleIndex.end()) {
+      F.Result["ruleIndex"] = Rule->second;
+    }
+    for (StringRef Key : {"locations", "relatedLocations"}) {
+      json::Array *Locations = F.Result.getArray(Key);
+      if (!Locations) {
+        continue;
+      }
+      for (json::Value &Location : *Locations) {
+        json::Object *Artifact = getArtifactLocation(Location);
+        if (!Artifact) {
+          continue;
+        }
+        auto Index = ArtifactIndex.find(getString(Artifact, "uri").str());
+        if (Index != ArtifactIndex.end()) {
+          (*Artifact)["index"] = Index->second;
+        }
+      }
+    }
+    MergedResults.push_back(std::move(F.Result));
+  }
+
+  Driver["rules"] = std::move(MergedRules);
+  Tool["driver"] = std::move(Driver);
+  Run["tool"] = std::move(Tool);
+  Run["artifacts"] = std::move(MergedArtifacts);
+  Run["results"] = std::move(MergedResults);
+  json::Array Runs;
+  Runs.push_back(std::move(Run));
+  Root["runs"] = std::move(Runs);
+  return std::move(Root);
+}
+
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// Driver
+//===----------------------------------------------------------------------===//
+
+int main(int argc, const char **argv) {
+  llvm::StringRef ToolHeading = "SSAF Transformation Report Merger";
+
+  InitLLVM X(argc, argv);
+  initTool(argc, argv, "0.1", MergeTransformationReportCategory, ToolHeading);
+
+  ReportMerger Merger;
+  for (const std::string &Path : InputPaths) {
+    Merger.add(readLog(Path), Path);
+  }
+  writeLog(Merger.takeMerged(), OutputPath);
+
+  return 0;
+}