diff --git a/README.md b/README.md
index 6497021..b51da03 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,9 @@ For a repository-level reviewer overview, use the
 SBOM tool from the supporting diagnostics projects and points reviewers to
 the right evidence path.
 
+For the shortest boundary check before adding or reviewing new material, use
+the [repository scope map](docs/repo-scope-map.md).
+
 ## Supporting Diagnostics Projects
 
 These projects are internal supporting material for reviewer depth. They are
@@ -160,6 +163,8 @@ they do not prove the same thing.
   [`docs/pypi-production-publishing-decision.md`](tools/sbom-diff-and-risk/docs/pypi-production-publishing-decision.md)
 - Reviewer route contract:
   [`scripts/validate-reviewer-routes.py`](scripts/validate-reviewer-routes.py)
+- Repository scope map:
+  [`docs/repo-scope-map.md`](docs/repo-scope-map.md)
 
 The TestPyPI Trusted Publishing dry-run has been validated. Production PyPI
 publishing is intentionally deferred.
diff --git a/docs/repo-scope-map.md b/docs/repo-scope-map.md
new file mode 100644
index 0000000..65fe390
--- /dev/null
+++ b/docs/repo-scope-map.md
@@ -0,0 +1,21 @@
+# Repository scope map
+
+Use this map as the shortest boundary check before adding new reviewer-facing
+material to this repository.
+
+## Flagship
+
+- `sbom-diff-and-risk`
+
+## Supporting diagnostics
+
+- `precipitation-anomaly-diagnostics`
+- `precipitation-anomaly-diagnostics-lab`
+- `python-weather-diagnostics-toolkit`
+
+## What this repo does not claim
+
+- not a climate portfolio
+- not a vulnerability scanner
+- not a CVE resolver
+- not a production PyPI release claim
diff --git a/docs/reviewer-brief.md b/docs/reviewer-brief.md
index f6c0931..78dcdda 100644
--- a/docs/reviewer-brief.md
+++ b/docs/reviewer-brief.md
@@ -24,7 +24,7 @@ workflows, but they are not part of the `sbom-diff-and-risk` release surface.
 
 | Review question | Start here | Stop when |
 | --- | --- | --- |
-| What is the repository shape? | This brief and the root [README](../README.md). | You can distinguish the flagship SBOM tool from the supporting diagnostics projects. |
+| What is the repository shape? | This brief, the root [README](../README.md), and the [repository scope map](repo-scope-map.md). | You can distinguish the flagship SBOM tool from the supporting diagnostics projects. |
 | What should I review for the SBOM tool? | The SBOM [reviewer path](../tools/sbom-diff-and-risk/docs/reviewer-path.md). | You have chosen the right 30-second, 5-minute, 15-minute, release, or deep-review route. |
 | Can the SBOM examples be reproduced? | The SBOM [example artifact regeneration guide](../tools/sbom-diff-and-risk/docs/example-artifact-regeneration.md). | `python scripts/regenerate-example-artifacts.py --check` passes. |
 | Can the released SBOM artifacts be verified? | The SBOM [verification guide](../tools/sbom-diff-and-risk/docs/verification.md). | You know whether to use checksums, release verification, or workflow artifact attestations. |
@@ -50,6 +50,8 @@ workflows, but they are not part of the `sbom-diff-and-risk` release surface.
 - Release evidence: `sbom-diff-and-risk` release notes, GitHub release
   verification docs, TestPyPI Trusted Publishing dry-run notes, and
   intentionally deferred production PyPI decision docs.
+- Scope map: `docs/repo-scope-map.md` keeps the flagship/supporting split and
+  repository non-claims explicit.
 - Non-goals: vulnerability scanning, CVE resolution, exploitability scoring,
   package safety verdicts, hidden enrichment, or production PyPI claims.
 
diff --git a/scripts/validate-reviewer-routes.py b/scripts/validate-reviewer-routes.py
index 34ed49f..d6c0610 100644
--- a/scripts/validate-reviewer-routes.py
+++ b/scripts/validate-reviewer-routes.py
@@ -13,6 +13,7 @@
 DOCS_TO_VALIDATE = (
     Path("README.md"),
     Path("docs/reviewer-brief.md"),
+    Path("docs/repo-scope-map.md"),
     Path("tools/sbom-diff-and-risk/docs/reviewer-path.md"),
     Path("projects/precipitation-anomaly-diagnostics/docs/reviewer-path.md"),
     Path("projects/precipitation-anomaly-diagnostics-lab/docs/reviewer-path.md"),
@@ -42,6 +43,7 @@
 REQUIRED_LINK_TARGETS = {
     Path("README.md"): {
         "docs/reviewer-brief.md",
+        "docs/repo-scope-map.md",
         "tools/sbom-diff-and-risk/docs/reviewer-path.md",
         "tools/sbom-diff-and-risk/docs/reviewer-evidence-pack.md",
         "projects/precipitation-anomaly-diagnostics/docs/reviewer-path.md",
@@ -50,12 +52,14 @@
     },
     Path("docs/reviewer-brief.md"): {
         "README.md",
+        "docs/repo-scope-map.md",
         "tools/sbom-diff-and-risk/docs/reviewer-path.md",
         "tools/sbom-diff-and-risk/docs/example-artifact-regeneration.md",
         "projects/precipitation-anomaly-diagnostics/docs/reviewer-path.md",
         "projects/precipitation-anomaly-diagnostics-lab/docs/reviewer-path.md",
         "projects/python-weather-diagnostics-toolkit/docs/reviewer-path.md",
     },
+    Path("docs/repo-scope-map.md"): set(),
     Path("tools/sbom-diff-and-risk/docs/reviewer-path.md"): {
         ".github/workflows/reviewer-route-contract-ci.yml",
         "scripts/validate-reviewer-routes.py",
@@ -128,6 +132,19 @@
         "supporting diagnostics projects",
         "production PyPI publishing remains intentionally deferred",
     ),
+    Path("docs/repo-scope-map.md"): (
+        "Flagship",
+        "sbom-diff-and-risk",
+        "Supporting diagnostics",
+        "precipitation-anomaly-diagnostics",
+        "precipitation-anomaly-diagnostics-lab",
+        "python-weather-diagnostics-toolkit",
+        "What this repo does not claim",
+        "not a climate portfolio",
+        "not a vulnerability scanner",
+        "not a CVE resolver",
+        "not a production PyPI release claim",
+    ),
     Path("tools/sbom-diff-and-risk/docs/reviewer-path.md"): (
         "Artifact evidence map",
         "Reviewer route contract",