diff --git a/Makefile b/Makefile
index b7b874c..6071ca5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: build test validate dist release-dry-run clean
+.PHONY: build test validate validate-maturity dist release-dry-run clean
 
 BIN := holmes
 DIST_DIR := dist
@@ -17,7 +17,10 @@ build:
 test:
 	go test ./...
 
-validate: build
+validate-maturity:
+	python3 tools/validate_maturity.py
+
+validate: build validate-maturity
 	python3 tools/validate_holmes.py
 	bin/$(BIN) --version
 	bin/$(BIN) doctor
diff --git a/repo.maturity.yaml b/repo.maturity.yaml
new file mode 100644
index 0000000..e31c8ca
--- /dev/null
+++ b/repo.maturity.yaml
@@ -0,0 +1,62 @@
+schemaVersion: repo-maturity.v1
+repository: SocioProphet/holmes
+plane: runtime
+status: active
+canonicality: canonical
+owners:
+  - SocioProphet
+maturity:
+  level: M2
+  targetLevel: M3
+  evidence:
+    - README.md defines Holmes purpose, product family, Slash Topics training role, proof-claim reasoning role, repo boundaries, and integration path.
+    - docs/ARCHITECTURE.md defines Holmes product components, service boundaries, TriTRPC method families, and promotion rules.
+    - docs/NLP_COMPONENT_ALIGNMENT.md defines governed NLP component coverage and Slash Topics topic-model training alignment.
+    - docs/PROOF_CLAIM_CONTRACT.md defines the Propose -> Explain -> Verify proof-claim contract and policy-admission boundary.
+    - examples/holmes-surface.json provides the machine-readable Holmes product surface fixture.
+    - examples/holmes-proof-claim-contract.json provides deterministic proof-claim reasoning fixture coverage.
+    - tools/validate_holmes.py validates Holmes surface and proof-claim contract fixtures.
+    - Makefile provides build, test, validate, dist, and release-dry-run targets.
+    - .github/workflows/validate.yml runs make validate and make release-dry-run on pull requests and main pushes.
+validation:
+  commands:
+    - make validate
+  ciRequired: true
+  lastKnownStatus: pending
+integrations:
+  - repository: SocioProphet/functional-model-surfaces
+    relationship: normative cross-surface standards and maturity model reference
+    required: true
+  - repository: SocioProphet/prophet-platform
+    relationship: runtime deployment and platform records after contracts stabilize
+    required: true
+  - repository: SocioProphet/sherlock-search
+    relationship: discovery, retrieval, evidence search, and investigation input surface
+    required: true
+  - repository: SocioProphet/slash-topics
+    relationship: governed topic-pack semantics and topic-model training consumer
+    required: true
+  - repository: SociOS-Linux/nlplab
+    relationship: Linux-native NLP lab execution and benchmark receipts
+    required: true
+  - repository: SourceOS-Linux/sourceos-model-carry
+    relationship: SourceOS client references and signed service carry refs
+    required: true
+  - repository: SocioProphet/ontogenesis
+    relationship: canonical semantic contracts for claims, traces, truth bounds, and contradiction artifacts
+    required: true
+  - repository: SocioProphet/policy-fabric
+    relationship: downstream policy admission for Holmes evidence and proof artifacts
+    required: true
+  - repository: SocioProphet/agentplane
+    relationship: governed execution after policy outcomes are decided
+    required: true
+  - repository: SocioProphet/sociosphere
+    relationship: workspace governance and maturity ingestion
+    required: false
+nextActions:
+  - Add negative fixtures and a negative-fixture runner so Holmes can honestly claim M3.
+  - Replace deterministic not-yet-wired CLI stubs with service-backed Sherlock, graph, and governance adapters.
+  - Add schema files for Holmes surface, proof-claim contract, and Slash Topics training references.
+  - Add release notes, checksums, and provenance attestations for M4 readiness.
+  - Register Holmes in workspace-inventory or Sociosphere scorecard ingestion.
diff --git a/tools/validate_maturity.py b/tools/validate_maturity.py
new file mode 100644
index 0000000..13b4dfa
--- /dev/null
+++ b/tools/validate_maturity.py
@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+from __future__ import annotations
+
+import re
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+MATURITY = ROOT / "repo.maturity.yaml"
+
+REQUIRED_HEADER_VALUES = {
+    "schemaVersion": "repo-maturity.v1",
+    "repository": "SocioProphet/holmes",
+    "plane": "runtime",
+    "status": "active",
+    "canonicality": "canonical",
+}
+REQUIRED_TEXT = [
+    "owners:",
+    "  - SocioProphet",
+    "maturity:",
+    "  level: M2",
+    "  targetLevel: M3",
+    "validation:",
+    "  commands:",
+    "    - make validate",
+    "  ciRequired: true",
+    "integrations:",
+    "nextActions:",
+]
+REQUIRED_INTEGRATIONS = {
+    "SocioProphet/functional-model-surfaces",
+    "SocioProphet/prophet-platform",
+    "SocioProphet/sherlock-search",
+    "SocioProphet/slash-topics",
+    "SociOS-Linux/nlplab",
+    "SourceOS-Linux/sourceos-model-carry",
+    "SocioProphet/ontogenesis",
+    "SocioProphet/policy-fabric",
+    "SocioProphet/agentplane",
+    "SocioProphet/sociosphere",
+}
+ALLOWED_VALIDATION_STATUS = {"pending", "passing", "failing", "unknown"}
+
+
+def fail(message: str) -> int:
+    print(f"ERROR: {message}", file=sys.stderr)
+    return 1
+
+
+def scalar(text: str, key: str) -> str | None:
+    match = re.search(rf"^{re.escape(key)}:\s*(.+?)\s*$", text, flags=re.MULTILINE)
+    if not match:
+        return None
+    return match.group(1).strip().strip('"')
+
+
+def count_list_items_in_section(text: str, section: str) -> int:
+    match = re.search(rf"^{re.escape(section)}:\n(?P<body>(?:\s+.*\n?)*)", text, flags=re.MULTILINE)
+    if not match:
+        return 0
+    body = match.group("body")
+    return len(re.findall(r"^\s+-\s+", body, flags=re.MULTILINE))
+
+
+def main() -> int:
+    if not MATURITY.exists():
+        return fail("missing repo.maturity.yaml")
+    text = MATURITY.read_text()
+
+    for key, expected in REQUIRED_HEADER_VALUES.items():
+        observed = scalar(text, key)
+        if observed != expected:
+            return fail(f"{key} must be {expected!r}; got {observed!r}")
+
+    for required in REQUIRED_TEXT:
+        if required not in text:
+            return fail(f"missing required maturity text: {required}")
+
+    status = scalar(text, "lastKnownStatus")
+    if status not in ALLOWED_VALIDATION_STATUS:
+        return fail(f"validation.lastKnownStatus must be one of {sorted(ALLOWED_VALIDATION_STATUS)}; got {status!r}")
+
+    missing_integrations = sorted(repo for repo in REQUIRED_INTEGRATIONS if repo not in text)
+    if missing_integrations:
+        return fail(f"missing integrations: {missing_integrations}")
+
+    evidence_count = count_list_items_in_section(text, "  evidence")
+    if evidence_count < 6:
+        return fail(f"maturity.evidence should contain at least 6 concrete evidence items; got {evidence_count}")
+
+    next_actions = count_list_items_in_section(text, "nextActions")
+    if next_actions < 3:
+        return fail(f"nextActions should contain at least 3 roadmap items; got {next_actions}")
+
+    print("OK: Holmes maturity manifest validated")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())