From ff78d3e8adf001959614b90e6412a9a57a46985b Mon Sep 17 00:00:00 2001
From: Brian Searls <briansrls@gunb.ai>
Date: Tue, 30 Jun 2026 22:31:39 +0000
Subject: [PATCH] lens: add Witness<Bool> API + perturb-RED witness for
 medium_structure_containment
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Gate PR-A step 1 only: execution-proven Holds→Violates flip on canonical
scan roots via medium_structure_containment_witness fed by live
medium_structure_leak_facts read-back. medium_structure_project.rs
retirement (HAND[] delete) deferred per loyal-bee MIXED split — separate
from this diff.

Co-authored-by: Cursor <cursoragent@cursor.com>
---
 src/v2/lens/medium_structure_containment.dag  | 50 +++++++++++++++++++
 .../scanner/perturb_red_test.dag              | 42 ++++++++++++++++
 .../perturb_red/plant.dag                     | 12 +++++
 3 files changed, 104 insertions(+)
 create mode 100644 src/v2/test/claim/medium_structure_containment/scanner/perturb_red_test.dag
 create mode 100644 src/v2/test/fixture/medium_structure_scan/perturb_red/plant.dag

diff --git a/src/v2/lens/medium_structure_containment.dag b/src/v2/lens/medium_structure_containment.dag
index ca4f6e0a95a..3aca6f167b8 100644
--- a/src/v2/lens/medium_structure_containment.dag
+++ b/src/v2/lens/medium_structure_containment.dag
@@ -11,8 +11,16 @@ import v2.std.algebra {
   list_snoc_item
 }
 import v2.std.collection { List }
+import v2.std.diagnostic {
+  AmbiguousIntent,
+  Diagnostic,
+  Textual,
+  Unavailable,
+  WholeFile
+}
 import v2.std.logic { Bool }
 import v2.std.text { Char, String }
+import v2.std.witness { Holds, Violates, Witness }
 
 type MediumLeakFace
   = InlineSyntaxLiteral
@@ -273,6 +281,48 @@ fn medium_structure_containment_clean_live(
   )
 }
 
+fn medium_structure_containment_witness_diagnostic() -> Diagnostic {
+  Diagnostic {
+    reason: ^medium_structure_containment_leak_detected,
+    at: Textual { file: ^medium_structure_containment_lens_file, extent: WholeFile },
+    correction: Unavailable { reason: AmbiguousIntent }
+  }
+}
+
+fn medium_structure_containment_witness(
+  emit_roots: List<String>,
+  check_roots: List<String>
+) -> Witness<Bool> {
+  if medium_structure_containment_clean_live(
+    emit_roots: emit_roots,
+    check_roots: check_roots
+  ) {
+    Holds { value: true }
+  } else {
+    Violates { diagnostic: medium_structure_containment_witness_diagnostic() }
+  }
+}
+
+fn medium_structure_containment_canonical_witness() -> Witness<Bool> {
+  medium_structure_containment_witness(
+    emit_roots: medium_emit_side_scan_roots,
+    check_roots: medium_check_side_scan_roots
+  )
+}
+
+fn medium_structure_check_roots_with_perturb(perturb_roots: List<String>) -> List<String> {
+  list_append(left: medium_check_side_scan_roots, right: perturb_roots)
+}
+
+fn medium_structure_containment_canonical_with_check_perturb_witness(
+  perturb_roots: List<String>
+) -> Witness<Bool> {
+  medium_structure_containment_witness(
+    emit_roots: medium_emit_side_scan_roots,
+    check_roots: medium_structure_check_roots_with_perturb(perturb_roots: perturb_roots)
+  )
+}
+
 data construction_justification: ConstructionJustification = ConstructionJustification {
   class: WallAfterGrounding { dissolves_to: RealizationDispatch }
 }
diff --git a/src/v2/test/claim/medium_structure_containment/scanner/perturb_red_test.dag b/src/v2/test/claim/medium_structure_containment/scanner/perturb_red_test.dag
new file mode 100644
index 00000000000..d7b34ad2179
--- /dev/null
+++ b/src/v2/test/claim/medium_structure_containment/scanner/perturb_red_test.dag
@@ -0,0 +1,42 @@
+module v2.test.medium_structure_containment.scanner.perturb_red
+
+import v2.lens.medium_structure_containment {
+  medium_structure_containment_canonical_witness,
+  medium_structure_containment_canonical_with_check_perturb_witness,
+  medium_structure_leak_count_live,
+  medium_emit_side_scan_roots,
+  medium_structure_check_roots_with_perturb
+}
+import v2.std.collection { List }
+import v2.std.logic { Bool }
+import v2.std.text { String }
+import v2.std.witness { Holds, Violates }
+
+data perturb_red_scan_roots: List<String> = [
+  "src/v2/test/fixture/medium_structure_scan/perturb_red"
+]
+
+test fn medium_structure_canonical_read_back_holds() -> Bool {
+  match medium_structure_containment_canonical_witness() {
+    Holds { value: _ } => true
+    Violates { diagnostic: _ } => false
+  }
+}
+
+test fn medium_structure_canonical_perturb_flips_violates() -> Bool {
+  match medium_structure_containment_canonical_with_check_perturb_witness(
+    perturb_roots: perturb_red_scan_roots
+  ) {
+    Holds { value: _ } => false
+    Violates { diagnostic: _ } => true
+  }
+}
+
+test fn medium_structure_perturb_red_leak_count_positive() -> Bool {
+  medium_structure_leak_count_live(
+    emit_roots: medium_emit_side_scan_roots,
+    check_roots: medium_structure_check_roots_with_perturb(
+      perturb_roots: perturb_red_scan_roots
+    )
+  ) > 0
+}
diff --git a/src/v2/test/fixture/medium_structure_scan/perturb_red/plant.dag b/src/v2/test/fixture/medium_structure_scan/perturb_red/plant.dag
new file mode 100644
index 00000000000..c96af8a60b2
--- /dev/null
+++ b/src/v2/test/fixture/medium_structure_scan/perturb_red/plant.dag
@@ -0,0 +1,12 @@
+module v2.test.fixture.medium_structure_scan.perturb_red_plant
+import v2.std.logic { Bool }
+import v2.std.text { String }
+
+fn expected_ci_yml() -> String {
+  "runs-on: linux\n"
+}
+
+fn perturb_red_check_side_leak() -> Bool {
+  let yaml = expected_ci_yml()
+  string_contains(s: yaml, pattern: "runs-on")
+}