diff --git a/docs/README.md b/docs/README.md
index 1aebe8d49..39cddb114 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -18,7 +18,7 @@ Use:
 7. `python3 scripts/release_control/contract_audit.py --check` if you need a machine-derived subsystem contract audit, including explicit cross-subsystem dependency checks and exact registry-derived shared-boundary wording
    Local pre-commit runs the v6 machine audits against staged control-file content so partial staging cannot hide governance drift.
    Local pre-commit also blocks partial staging for hook-sensitive governance files under `docs/release-control/v6/`, `scripts/release_control/`, `internal/repoctl/`, `.husky/pre-commit`, and `.github/workflows/canonical-governance.yml`, because those checks still execute or structurally read the working-tree versions locally.
-8. `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...]` if you need subsystem ownership, proof routing, lane context, relevant decision records, and dependent contract-update obligations for a change
+8. `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean` if you need subsystem ownership, proof routing, exact contract-focus lines, and compact lane context for a change
 
 For governed runtime changes, a staged subsystem contract only counts if its
 diff updates a substantive contract section such as `Purpose`, `Canonical Files`,
diff --git a/docs/release-control/v6/README.md b/docs/release-control/v6/README.md
index efd10abd2..4736fabee 100644
--- a/docs/release-control/v6/README.md
+++ b/docs/release-control/v6/README.md
@@ -81,7 +81,8 @@ Useful helper tools:
 - `python3 scripts/release_control/readiness_assertion_guard.py --active-target --proof-type hybrid`
   Runs any executable hybrid proof commands required by the active target phase, without replacing the linked manual release gates.
 - `python3 scripts/release_control/registry_audit.py --check`
-- `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...]` for subsystem ownership, proof routing, lane context, relevant decision records, and dependent contract-update obligations
+- `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean` for subsystem ownership, proof routing, exact contract-focus lines, and compact lane context without pulling the full governance payload into every lookup
+  Omit `--lean` when you explicitly need the full decision, release-gate, and status-summary payload.
 - `python3 scripts/release_control/work_claim.py --kind <KIND> --id <ID> --summary <SUMMARY> --agent-id <AGENT_ID> --pretty`
   Reserve or renew exactly one governed slice in a shared checkout before mutation without hand-editing `status.json`.
 - `python3 scripts/release_control/worktree_base.py --base-branch <BASE_BRANCH> --pretty`
diff --git a/docs/release-control/v6/internal/CANONICAL_DEVELOPMENT_PROTOCOL.md b/docs/release-control/v6/internal/CANONICAL_DEVELOPMENT_PROTOCOL.md
index 2a97d9ac4..edb5956a7 100644
--- a/docs/release-control/v6/internal/CANONICAL_DEVELOPMENT_PROTOCOL.md
+++ b/docs/release-control/v6/internal/CANONICAL_DEVELOPMENT_PROTOCOL.md
@@ -482,10 +482,11 @@ Before adding new behavior, the author must answer:
 If those answers are not obvious in under a minute, the subsystem still needs
 architectural hardening.
 
-Use `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...]`
-to ask the repo which subsystem, contract, proof route, live lane context,
-relevant decision records, and dependent contract-update obligations apply to a
-file set before editing.
+Use `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean`
+to ask the repo which subsystem, contract, proof route, exact contract-focus
+lines, and compact lane context apply to a file set before editing.
+Omit `--lean` only when the full decision, release-gate, or status-summary
+payload is materially needed.
 
 ## Boundary Rule
 
diff --git a/frontend-modern/public/docs/README.md b/frontend-modern/public/docs/README.md
index 1aebe8d49..39cddb114 100644
--- a/frontend-modern/public/docs/README.md
+++ b/frontend-modern/public/docs/README.md
@@ -18,7 +18,7 @@ Use:
 7. `python3 scripts/release_control/contract_audit.py --check` if you need a machine-derived subsystem contract audit, including explicit cross-subsystem dependency checks and exact registry-derived shared-boundary wording
    Local pre-commit runs the v6 machine audits against staged control-file content so partial staging cannot hide governance drift.
    Local pre-commit also blocks partial staging for hook-sensitive governance files under `docs/release-control/v6/`, `scripts/release_control/`, `internal/repoctl/`, `.husky/pre-commit`, and `.github/workflows/canonical-governance.yml`, because those checks still execute or structurally read the working-tree versions locally.
-8. `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...]` if you need subsystem ownership, proof routing, lane context, relevant decision records, and dependent contract-update obligations for a change
+8. `python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean` if you need subsystem ownership, proof routing, exact contract-focus lines, and compact lane context for a change
 
 For governed runtime changes, a staged subsystem contract only counts if its
 diff updates a substantive contract section such as `Purpose`, `Canonical Files`,
diff --git a/scripts/release_control/canonical_completion_guard.py b/scripts/release_control/canonical_completion_guard.py
index 7d45fbb2e..eccbc55f0 100644
--- a/scripts/release_control/canonical_completion_guard.py
+++ b/scripts/release_control/canonical_completion_guard.py
@@ -303,10 +303,31 @@ def required_contract_updates(
                 descriptor = f"{reference['heading']}: {reference['path']}"
                 if descriptor not in entry["matched_references"]:
                     entry["matched_references"].append(descriptor)
+                detail = {
+                    "heading": str(reference.get("heading", "")),
+                    "path": str(reference.get("path", "")),
+                }
+                if isinstance(reference.get("line"), int):
+                    detail["line"] = int(reference["line"])
+                if isinstance(reference.get("heading_line"), int):
+                    detail["heading_line"] = int(reference["heading_line"])
+                detail_list = entry.setdefault("matched_reference_details", [])
+                if detail not in detail_list:
+                    detail_list.append(detail)
 
     for data in required.values():
         data["touched_runtime_files"] = sorted(set(data["touched_runtime_files"]))
         data["matched_references"] = sorted(set(data["matched_references"]), key=str.casefold)
+        details = data.get("matched_reference_details")
+        if isinstance(details, list) and details:
+            data["matched_reference_details"] = sorted(
+                details,
+                key=lambda item: (
+                    int(item.get("line", 0) or 0),
+                    str(item.get("heading", "")).casefold(),
+                    str(item.get("path", "")).casefold(),
+                ),
+            )
 
     return dict(sorted(required.items()))
 
diff --git a/scripts/release_control/canonical_completion_guard_test.py b/scripts/release_control/canonical_completion_guard_test.py
index c84b2a810..0916a741e 100644
--- a/scripts/release_control/canonical_completion_guard_test.py
+++ b/scripts/release_control/canonical_completion_guard_test.py
@@ -2708,6 +2708,23 @@ class CanonicalCompletionGuardTest(unittest.TestCase):
                 "## Extension Points: internal/unifiedresources/views.go",
             ],
         )
+        self.assertEqual(
+            required["docs/release-control/v6/internal/subsystems/monitoring.md"]["matched_reference_details"],
+            [
+                {
+                    "heading": "## Canonical Files",
+                    "path": "internal/unifiedresources/views.go",
+                    "line": 32,
+                    "heading_line": 23,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/unifiedresources/views.go",
+                    "line": 46,
+                    "heading_line": 42,
+                },
+            ],
+        )
 
     def test_monitoring_owned_runtime_does_not_require_unified_resources_contract(self):
         required = required_contract_updates(["internal/monitoring/monitor.go"])
diff --git a/scripts/release_control/control_plane.py b/scripts/release_control/control_plane.py
index 1d7325446..7be1fc6a8 100644
--- a/scripts/release_control/control_plane.py
+++ b/scripts/release_control/control_plane.py
@@ -334,7 +334,7 @@ def agent_entrypoint(*, staged: bool = False) -> dict[str, Any]:
             "python3 scripts/release_control/status_lookup.py --followup <FOLLOWUP_ID> --pretty",
             "python3 scripts/release_control/status_lookup.py --work-claim <CLAIM_ID> --pretty",
             "python3 scripts/release_control/work_claim.py --kind <KIND> --id <ID> --summary <SUMMARY> --agent-id <AGENT_ID> --pretty",
-            "python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty",
+            "python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean",
             "python3 scripts/release_control/worktree_base.py --base-branch <BASE_BRANCH> --pretty",
             "python3 scripts/release_control/worktree_claim.py --kind <KIND> --id <ID> --summary <SUMMARY> --agent-id <AGENT_ID> --pretty",
             "python3 scripts/release_control/worktree_finish.py --base-branch <BASE_BRANCH> --pretty",
diff --git a/scripts/release_control/control_plane_audit_test.py b/scripts/release_control/control_plane_audit_test.py
index a21522fc8..45d28b73c 100644
--- a/scripts/release_control/control_plane_audit_test.py
+++ b/scripts/release_control/control_plane_audit_test.py
@@ -123,6 +123,10 @@ class ControlPlaneAuditTest(unittest.TestCase):
             "python3 scripts/release_control/work_claim.py --kind <KIND> --id <ID> --summary <SUMMARY> --agent-id <AGENT_ID> --pretty",
             entrypoint["targeted_lookup_commands"],
         )
+        self.assertIn(
+            "python3 scripts/release_control/subsystem_lookup.py <path> [<path> ...] --pretty --lean",
+            entrypoint["targeted_lookup_commands"],
+        )
         self.assertIn("reserve exactly one", entrypoint["claim_rule"])
         self.assertIn("record any remaining same-lane residual", entrypoint["claim_rule"])
         self.assertIn(
diff --git a/scripts/release_control/subsystem_contracts.py b/scripts/release_control/subsystem_contracts.py
index 9b775b83f..8f82b9db1 100644
--- a/scripts/release_control/subsystem_contracts.py
+++ b/scripts/release_control/subsystem_contracts.py
@@ -182,12 +182,22 @@ def parse_contract_text(rel: str, content: str) -> tuple[dict[str, Any], list[st
     for heading in ("## Canonical Files", "## Shared Boundaries", "## Extension Points"):
         if heading not in heading_positions:
             continue
+        heading_line = heading_positions[heading] + 1
+        body_start = heading_positions[heading] + 1
         body = section_body(lines, heading)
         items = section_list_items(body)
-        for _, item in items:
+        for item_index, item in items:
+            line_number = body_start + item_index + 1
             for token in re.findall(r"`([^`]+)`", item):
                 if looks_like_repo_path(token):
-                    path_references.append({"heading": heading, "path": token})
+                    path_references.append(
+                        {
+                            "heading": heading,
+                            "path": token,
+                            "line": line_number,
+                            "heading_line": heading_line,
+                        }
+                    )
 
     return {
         "title": lines[0].strip() if lines else "",
diff --git a/scripts/release_control/subsystem_contracts_test.py b/scripts/release_control/subsystem_contracts_test.py
index 5c17e3199..cab1c182e 100644
--- a/scripts/release_control/subsystem_contracts_test.py
+++ b/scripts/release_control/subsystem_contracts_test.py
@@ -76,9 +76,24 @@ Stable.
         self.assertEqual(
             parsed["path_references"],
             [
-                {"heading": "## Canonical Files", "path": "internal/example/runtime.go"},
-                {"heading": "## Shared Boundaries", "path": "internal/shared/runtime.go"},
-                {"heading": "## Extension Points", "path": "internal/example/"},
+                {
+                    "heading": "## Canonical Files",
+                    "path": "internal/example/runtime.go",
+                    "line": 17,
+                    "heading_line": 15,
+                },
+                {
+                    "heading": "## Shared Boundaries",
+                    "path": "internal/shared/runtime.go",
+                    "line": 21,
+                    "heading_line": 19,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/example/",
+                    "line": 25,
+                    "heading_line": 23,
+                },
             ],
         )
 
@@ -138,8 +153,18 @@ Stable.
         self.assertEqual(
             matches[0]["matched_references"],
             [
-                {"heading": "## Canonical Files", "path": "internal/example/runtime.go"},
-                {"heading": "## Extension Points", "path": "internal/example/"},
+                {
+                    "heading": "## Canonical Files",
+                    "path": "internal/example/runtime.go",
+                    "line": 17,
+                    "heading_line": 15,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/example/",
+                    "line": 25,
+                    "heading_line": 23,
+                },
             ],
         )
 
@@ -149,7 +174,12 @@ Stable.
         self.assertEqual(
             shared_matches[0]["matched_references"],
             [
-                {"heading": "## Shared Boundaries", "path": "internal/shared/runtime.go"},
+                {
+                    "heading": "## Shared Boundaries",
+                    "path": "internal/shared/runtime.go",
+                    "line": 21,
+                    "heading_line": 19,
+                },
             ],
         )
 
diff --git a/scripts/release_control/subsystem_lookup.py b/scripts/release_control/subsystem_lookup.py
index 5ea783126..f388a841a 100644
--- a/scripts/release_control/subsystem_lookup.py
+++ b/scripts/release_control/subsystem_lookup.py
@@ -20,6 +20,7 @@ from canonical_completion_guard import (
     required_contract_updates,
     subsystem_matches_path,
 )
+from subsystem_contracts import load_contract_index, referenced_contracts_for_path
 from status_audit import audit_status_payload, load_status_payload
 from registry_audit import load_registry_payload
 
@@ -82,6 +83,40 @@ def verification_requirements_for_test_path(rule: dict[str, Any], path: str) ->
     return requirements
 
 
+def ownership_basis_for_path(rule: dict[str, Any], path: str) -> dict[str, str] | None:
+    for exact_file in rule.get("owned_files", []):
+        if path == exact_file:
+            return {"type": "owned-file", "value": str(exact_file)}
+    for prefix in rule.get("owned_prefixes", []):
+        normalized = str(prefix).rstrip("/")
+        if path == normalized or path.startswith(str(prefix)):
+            return {"type": "owned-prefix", "value": str(prefix)}
+    return None
+
+
+def normalized_reference_details(references: list[dict[str, Any]]) -> list[dict[str, Any]]:
+    normalized: list[dict[str, Any]] = []
+    for reference in references:
+        detail = {
+            "heading": str(reference.get("heading", "")),
+            "path": str(reference.get("path", "")),
+        }
+        if isinstance(reference.get("line"), int):
+            detail["line"] = int(reference["line"])
+        if isinstance(reference.get("heading_line"), int):
+            detail["heading_line"] = int(reference["heading_line"])
+        if detail not in normalized:
+            normalized.append(detail)
+    return sorted(
+        normalized,
+        key=lambda item: (
+            int(item.get("line", 0) or 0),
+            str(item.get("heading", "")).casefold(),
+            str(item.get("path", "")).casefold(),
+        ),
+    )
+
+
 def lane_context_for_rule(rule: dict[str, Any], status_report: dict[str, Any]) -> dict[str, Any] | None:
     lane_id = str(rule.get("lane", "")).strip()
     subsystem_id = str(rule.get("id", "")).strip()
@@ -115,10 +150,98 @@ def lane_context_for_rule(rule: dict[str, Any], status_report: dict[str, Any]) -
     }
 
 
-def lookup_paths(paths: list[str]) -> dict[str, Any]:
+def compact_control_plane(control_plane: dict[str, Any]) -> dict[str, Any]:
+    active_target = dict(control_plane.get("active_target", {}))
+    return {
+        "active_profile_id": control_plane.get("active_profile_id"),
+        "active_target": {
+            key: active_target[key]
+            for key in ("id", "kind", "status", "completion_rule", "completion_met")
+            if key in active_target
+        },
+    }
+
+
+def compact_lane_context(lane_context: dict[str, Any] | None) -> dict[str, Any] | None:
+    if lane_context is None:
+        return None
+    lane = lane_context.get("lane")
+    compact_lane = None
+    if isinstance(lane, dict):
+        compact_lane = {
+            key: lane.get(key)
+            for key in ("id", "name", "status", "derived_status", "completion_state", "gap", "repo_ids")
+            if key in lane
+        }
+    return {
+        "lane_id": lane_context.get("lane_id"),
+        "lane": compact_lane,
+        "open_decision_ids": [
+            str(decision.get("id"))
+            for decision in lane_context.get("open_decisions", [])
+            if isinstance(decision, dict) and decision.get("id")
+        ],
+        "resolved_decision_ids": [
+            str(decision.get("id"))
+            for decision in lane_context.get("resolved_decisions", [])
+            if isinstance(decision, dict) and decision.get("id")
+        ],
+        "release_gate_ids": [
+            str(gate.get("id"))
+            for gate in lane_context.get("release_gates", [])
+            if isinstance(gate, dict) and gate.get("id")
+        ],
+    }
+
+
+def compact_match(match: dict[str, Any]) -> dict[str, Any]:
+    compacted = dict(match)
+    compacted["lane_context"] = compact_lane_context(match.get("lane_context"))
+    return compacted
+
+
+def compact_contract_update(contract_update: dict[str, Any]) -> dict[str, Any]:
+    compacted = dict(contract_update)
+    if compacted.get("matched_reference_details"):
+        compacted.pop("matched_references", None)
+    return compacted
+
+
+def compact_lookup_result(result: dict[str, Any]) -> dict[str, Any]:
+    return {
+        "control_plane": compact_control_plane(result.get("control_plane", {})),
+        "status_audit_errors": list(result.get("status_audit_errors", [])),
+        "files": [
+            {
+                **entry,
+                "matches": [compact_match(match) for match in entry.get("matches", [])],
+                "dependent_contract_updates": [
+                    compact_contract_update(contract)
+                    for contract in entry.get("dependent_contract_updates", [])
+                ],
+            }
+            for entry in result.get("files", [])
+        ],
+        "impacted_subsystems": [
+            {
+                **entry,
+                "lane_context": compact_lane_context(entry.get("lane_context")),
+            }
+            for entry in result.get("impacted_subsystems", [])
+        ],
+        "required_contract_updates": [
+            compact_contract_update(contract)
+            for contract in result.get("required_contract_updates", [])
+        ],
+        "unowned_runtime_files": list(result.get("unowned_runtime_files", [])),
+    }
+
+
+def lookup_paths(paths: list[str], *, lean: bool = False) -> dict[str, Any]:
     normalized = [normalize_input_path(path) for path in paths if path.strip()]
     rules = load_subsystem_rules()
     rules_by_id = {str(rule["id"]): rule for rule in rules}
+    contract_index = load_contract_index()
     registry_payload = load_registry_payload()
     shared_ownership_by_path = {
         str(entry["path"]): entry
@@ -137,6 +260,12 @@ def lookup_paths(paths: list[str]) -> dict[str, Any]:
             classification = "ignored"
         elif is_test_or_fixture(path):
             classification = "test-or-fixture"
+        reference_matches_by_subsystem = {
+            str(contract["subsystem_id"]): normalized_reference_details(
+                list(contract.get("matched_references", []))
+            )
+            for contract in referenced_contracts_for_path(path, contract_index)
+        }
 
         matches = []
         if classification == "runtime":
@@ -151,6 +280,11 @@ def lookup_paths(paths: list[str]) -> dict[str, Any]:
                         "lane_context": lane_context_for_rule(rule, status_report),
                         "contract_update_required": True,
                         "proof_update_required": True,
+                        "ownership_basis": ownership_basis_for_path(rule, path),
+                        "matched_contract_references": reference_matches_by_subsystem.get(
+                            str(rule["id"]),
+                            [],
+                        ),
                         "verification_requirement": requirement,
                     }
                 )
@@ -164,6 +298,7 @@ def lookup_paths(paths: list[str]) -> dict[str, Any]:
                             "lane_context": lane_context_for_rule(rule, status_report),
                             "contract_update_required": False,
                             "proof_update_required": False,
+                            "ownership_basis": ownership_basis_for_path(rule, path),
                             "verification_requirement": requirement,
                         }
                     )
@@ -200,7 +335,7 @@ def lookup_paths(paths: list[str]) -> dict[str, Any]:
             }
         )
 
-    return {
+    result = {
         "control_plane": status_report.get("control_plane", {}),
         "scope": status_report.get("scope", {}),
         "status_summary": status_report.get("summary", {}),
@@ -210,6 +345,7 @@ def lookup_paths(paths: list[str]) -> dict[str, Any]:
         "required_contract_updates": list(contract_updates.values()),
         "unowned_runtime_files": unowned,
     }
+    return compact_lookup_result(result) if lean else result
 
 
 def parse_args(argv: list[str]) -> argparse.Namespace:
@@ -225,9 +361,24 @@ def parse_args(argv: list[str]) -> argparse.Namespace:
         action="store_true",
         help="Print a concise human-readable summary instead of JSON.",
     )
+    parser.add_argument(
+        "--lean",
+        action="store_true",
+        help="Return compact agent-facing context with exact contract reference lines.",
+    )
     return parser.parse_args(argv)
 
 
+def format_reference_detail(reference: dict[str, Any]) -> str:
+    heading = str(reference.get("heading", "")).strip() or "-"
+    path = str(reference.get("path", "")).strip()
+    line = reference.get("line")
+    line_suffix = f" @L{line}" if isinstance(line, int) else ""
+    if path:
+        return f"{heading}{line_suffix}: {path}"
+    return f"{heading}{line_suffix}"
+
+
 def render_pretty(result: dict[str, Any]) -> str:
     lines: list[str] = []
     control_plane = result.get("control_plane", {})
@@ -257,12 +408,27 @@ def render_pretty(result: dict[str, Any]) -> str:
             )
             if lane_context and lane_context.get("lane"):
                 lane = lane_context["lane"]
+                gap = lane.get("gap")
+                gap_text = f"{gap:.0f}" if isinstance(gap, (int, float)) else "-"
+                open_decisions = lane_context.get("open_decisions", lane_context.get("open_decision_ids", []))
+                release_gates = lane_context.get("release_gates", lane_context.get("release_gate_ids", []))
                 lines.append(
                     f"    lane {lane_context['lane_id']} "
-                    f"gap={lane['gap']:.0f} derived={lane['derived_status']} "
+                    f"gap={gap_text} derived={lane.get('derived_status') or '-'} "
                     f"repos={','.join(lane.get('repo_ids', [])) or '-'} "
-                    f"open_decisions={len(lane_context['open_decisions'])} "
-                    f"release_gates={len(lane_context['release_gates'])}"
+                    f"open_decisions={len(open_decisions)} "
+                    f"release_gates={len(release_gates)}"
+                )
+            if match.get("matched_contract_references"):
+                focus = ", ".join(
+                    format_reference_detail(reference)
+                    for reference in match["matched_contract_references"]
+                )
+                lines.append(f"    contract focus: {focus}")
+            elif match.get("ownership_basis"):
+                basis = match["ownership_basis"]
+                lines.append(
+                    f"    ownership basis: {basis.get('type') or '-'} {basis.get('value') or '-'}"
                 )
         if entry.get("shared_ownership"):
             shared = entry["shared_ownership"]
@@ -273,8 +439,12 @@ def render_pretty(result: dict[str, Any]) -> str:
             lines.append(
                 f"  - also update {contract['subsystem']} contract -> {contract['contract']}"
             )
-            for reference in contract.get("matched_references", []):
-                lines.append(f"    referenced by {reference}")
+            if contract.get("matched_reference_details"):
+                for reference in contract["matched_reference_details"]:
+                    lines.append(f"    referenced by {format_reference_detail(reference)}")
+            else:
+                for reference in contract.get("matched_references", []):
+                    lines.append(f"    referenced by {reference}")
         if entry["classification"] == "runtime" and not entry["matches"]:
             lines.append("  - no owning subsystem rule matched")
     for path in result["unowned_runtime_files"]:
@@ -295,7 +465,7 @@ def main(argv: list[str] | None = None) -> int:
         print("no file paths provided", file=sys.stderr)
         return 2
 
-    result = lookup_paths(paths)
+    result = lookup_paths(paths, lean=args.lean)
     output = render_pretty(result) if args.pretty else json.dumps(result, indent=2, sort_keys=True)
     print(output)
     return 0
diff --git a/scripts/release_control/subsystem_lookup_test.py b/scripts/release_control/subsystem_lookup_test.py
index c80cc285b..41b2a22e7 100644
--- a/scripts/release_control/subsystem_lookup_test.py
+++ b/scripts/release_control/subsystem_lookup_test.py
@@ -2,7 +2,7 @@ import unittest
 from pathlib import Path
 
 from canonical_completion_guard import REPO_ROOT
-from subsystem_lookup import lookup_paths
+from subsystem_lookup import lookup_paths, parse_args, render_pretty
 
 
 RECOVERY_PRODUCT_SURFACE_EXACT_FILES = [
@@ -39,6 +39,12 @@ PLATFORM_CONNECTIONS_WORKSPACE_EXACT_FILES = [
 
 
 class SubsystemLookupTest(unittest.TestCase):
+    def test_parse_args_accepts_lean_flag(self) -> None:
+        args = parse_args(["internal/api/ai_handler.go", "--pretty", "--lean"])
+        self.assertEqual(args.paths, ["internal/api/ai_handler.go"])
+        self.assertTrue(args.pretty)
+        self.assertTrue(args.lean)
+
     def test_lookup_paths_reports_multiple_subsystems_for_shared_runtime_file(self) -> None:
         result = lookup_paths(["internal/api/resources.go"])
         impacted = {entry["subsystem"] for entry in result["impacted_subsystems"]}
@@ -4441,11 +4447,106 @@ class SubsystemLookupTest(unittest.TestCase):
             {contract["subsystem"] for contract in file_entry["dependent_contract_updates"]},
             {"monitoring"},
         )
+        monitoring_contract = file_entry["dependent_contract_updates"][0]
+        self.assertEqual(
+            monitoring_contract["matched_reference_details"],
+            [
+                {
+                    "heading": "## Canonical Files",
+                    "path": "internal/unifiedresources/views.go",
+                    "line": 32,
+                    "heading_line": 23,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/unifiedresources/views.go",
+                    "line": 46,
+                    "heading_line": 42,
+                },
+            ],
+        )
         self.assertEqual(
             {contract["subsystem"] for contract in result["required_contract_updates"]},
             {"monitoring", "unified-resources"},
         )
 
+    def test_lookup_paths_reports_contract_focus_for_shared_api_runtime_file(self) -> None:
+        result = lookup_paths(["internal/api/ai_handler.go"])
+        file_entry = result["files"][0]
+        by_subsystem = {match["subsystem"]: match for match in file_entry["matches"]}
+
+        self.assertEqual(
+            by_subsystem["ai-runtime"]["matched_contract_references"],
+            [
+                {
+                    "heading": "## Canonical Files",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 24,
+                    "heading_line": 21,
+                },
+                {
+                    "heading": "## Shared Boundaries",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 45,
+                    "heading_line": 41,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 52,
+                    "heading_line": 49,
+                },
+            ],
+        )
+        self.assertEqual(
+            by_subsystem["api-contracts"]["matched_contract_references"],
+            [
+                {
+                    "heading": "## Shared Boundaries",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 108,
+                    "heading_line": 77,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 167,
+                    "heading_line": 125,
+                },
+                {
+                    "heading": "## Extension Points",
+                    "path": "internal/api/ai_handler.go",
+                    "line": 168,
+                    "heading_line": 125,
+                },
+            ],
+        )
+        self.assertEqual(
+            by_subsystem["api-contracts"]["ownership_basis"],
+            {"type": "owned-prefix", "value": "internal/api/"},
+        )
+
+    def test_lookup_paths_lean_mode_trims_status_payload_but_keeps_contract_focus(self) -> None:
+        result = lookup_paths(["internal/api/ai_handler.go"], lean=True)
+        self.assertNotIn("scope", result)
+        self.assertNotIn("status_summary", result)
+
+        file_entry = result["files"][0]
+        by_subsystem = {match["subsystem"]: match for match in file_entry["matches"]}
+        api_match = by_subsystem["api-contracts"]
+        self.assertEqual(api_match["lane_context"]["lane_id"], "L6")
+        self.assertEqual(api_match["lane_context"]["open_decision_ids"], [])
+        self.assertIn("paid-feature-entitlement-gating", api_match["lane_context"]["release_gate_ids"])
+        self.assertEqual(
+            [reference["line"] for reference in api_match["matched_contract_references"]],
+            [108, 167, 168],
+        )
+
+    def test_render_pretty_shows_contract_focus_for_lean_lookup(self) -> None:
+        rendered = render_pretty(lookup_paths(["internal/api/ai_handler.go"], lean=True))
+        self.assertIn("contract focus: ## Shared Boundaries @L108: internal/api/ai_handler.go", rendered)
+        self.assertIn("contract focus: ## Canonical Files @L24: internal/api/ai_handler.go", rendered)
+
     def test_lookup_paths_maps_unified_agent_runtime_to_agent_lifecycle(self) -> None:
         result = lookup_paths(["internal/hostagent/agent.go"])
         self.assertEqual(result["unowned_runtime_files"], [])