W2.6 — Cross-target python.dag leaf-model verification (PR #3938 §11.4 Wave 2). Mirror the rust.dag R1 pattern landed in #3972 (mergeCommit e2a33511ee) for python target. Deliverables: (1) python.dag R1 fixture (Phase-1 minimal Python source: 'def r1_test() -> int: return 0' or equivalent typed form

.github/workflows/ci.yml

@@ -238,6 +238,9 @@ jobs:
     - name: Phase 1 leaf-model R1 rustc boundary (gunbc#846 bypass)
       if: needs.affected.outputs.v4 == 'true' || needs.affected.outputs.workflow_policy == 'true'
       run: cargo test -p v3-compiler --test integration v4_leaf_model_rust_r1_rustc_test -- --quiet
+    - name: Phase 1 leaf-model python R1 boundary (gunbc#846 bypass)
+      if: needs.affected.outputs.v4 == 'true' || needs.affected.outputs.workflow_policy == 'true'
+      run: cargo test -p v3-compiler --test integration v4_leaf_model_python_r1_test -- --quiet
     - name: Phase 1 leaf-model R2a/R2b/R3-external rustc boundary (gunbc#846 bypass)
       if: needs.affected.outputs.v4 == 'true' || needs.affected.outputs.workflow_policy == 'true'
       run: cargo test -p v3-compiler --test integration v4_leaf_model_rust_r2_r3_external_rustc_test -- --quiet

_internal/INVARIANTS_OPS.md

@@ -48,6 +48,7 @@ Per **Dispatch-Discipline Mechanisms (b)** above, each **new** path added to `EX
 | `src/v3/compiler/tests/integration/v4_lens_identical_variant_payload_dag_smoke_test.rs` | **L1.4 IdenticalVariantPayload sub-signature:** `src/v4/lens/identical_variant_payload.dag` — Carrier-clone family scaffold (`CarrierCloneTrigger`, `IdenticalVariantPayloadVerdict` / `IdenticalVariantPayloadFact`); shared `coverage_defect_carrier_clone` per `docs/design-dissolution-lens.md` §5.1; does not block #3962 collapse. **ROADMAP:** `_internal/ROADMAP_OPS.md` § **Nine lanes** row **T-PB-B** / `pb_rust_tests_outside_residual_zero`. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs` land in the same PR as the smoke harness. **Dissolution:** remove when the lens consumes `v4.lens.structural_similarity` and enforcement runs without this host parse ratchet. **Interim ratchet:** `v4_lens_identical_variant_payload_dag_tokenizes_and_parses`; `v4_lens_identical_variant_payload_module_authority_and_entrypoints`. |
 | `src/v3/compiler/tests/integration/coverage_defect_acceptance_dag_test.rs` | **Coverage-defect acceptance keys:** `src/v4/lens/coverage.dag` carries the canonical coverage-key set for `docs/design-dissolution-lens.md` §5.1; the old emit-template key is retired into `TemplateHole`, and the old string-escape key is split into `TemplateHole` plus `CanonicalCarrier`. **ROADMAP:** `_internal/ROADMAP_OPS.md` § **Nine lanes** row **T-PB-B** / `pb_rust_tests_outside_residual_zero`. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs` land in the same PR as the parse-level ratchet. **Dissolution:** remove when the v4 coverage lens runs as `.dag` / generated coverage and can assert the same acceptance rows without this host parser check. **Interim ratchet:** `coverage_defect_acceptance_keys_match_declared_rows` tokenizes/parses `src/v4/lens/coverage.dag` and asserts the exact parsed `(coverage_defect_* data row, CoverageDefectKey variant)` set matches the expected acceptance-key table while rejecting retired emit-template / string-escape names. |
 | `src/v3/compiler/tests/boundary/v4_leaf_model_rust_r1_rustc_test.rs` | **Phase 1 leaf-model verification** (`docs/planning/v4-leaf-model-verification-2026-05-30.md` §7 R1): boundary `rustc` exercise for `src/v4/lens/leaf_model_verification.dag` happy + falsification fixtures; interim host runner `scripts/v4-leaf-model-rust-r1-verify.sh`. **ROADMAP:** `_internal/ROADMAP_OPS.md` § **Nine lanes** row **T-PB-B** / `pb_rust_tests_outside_residual_zero`; **TASKS.md** T-22/T-38 (Runtime/TestClaim verdict surface). **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs` land in the same PR as the harness. **Dissolution:** delete when modeled `run_target_verification` exercises `src/v4/test/claim/language_model/rust_r1.dag` without this hand-Rust bridge. **Interim ratchet:** `v4_leaf_model_rust_r1_fixture_strings_match_dag_authority`, `v4_leaf_model_rust_r1_happy_fixture_rustc_accepts`, `v4_leaf_model_rust_r1_falsification_fixture_rustc_e0308`. |
+| `src/v3/compiler/tests/boundary/v4_leaf_model_python_r1_test.rs` | **Phase 1 leaf-model verification — python.dag R1** (W2.6 / PR #3938 §11.4): boundary CPython exercise for `src/v4/lens/leaf_model_verification.dag` python happy + falsification fixtures; interim host runner `scripts/v4-leaf-model-python-r1-verify.sh`. **ROADMAP:** T-PB-B / T-22/T-38. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs`. **Dissolution:** delete when modeled `run_target_verification` exercises `src/v4/test/claim/language_model/python_r1.dag` without this hand-Rust bridge. **Interim ratchet:** `v4_leaf_model_python_r1_fixture_strings_match_dag_authority`, `v4_leaf_model_python_r1_happy_fixture_python_accepts`, `v4_leaf_model_python_r1_falsification_fixture_python_name_error`. |
 | `src/v3/compiler/tests/boundary/v4_leaf_model_rust_r2_r3_external_rustc_test.rs` | **Phase 1 leaf-model W1.7** (`docs/planning/v4-leaf-model-verification-2026-05-30.md` §7 R2a/R2b/R3-external): boundary `rustc` + runtime exercise for R2a algebra ops (E0599 falsification), R2b debug panic / release wrap on `i32::MAX + 1` runtime path, R3-external Symbol nominal carrier vs alias+ctor mismatch (E0423); interim host runners `scripts/v4-leaf-model-rust-r2a-verify.sh`, `scripts/v4-leaf-model-rust-r2b-verify.sh`, `scripts/v4-leaf-model-rust-r3-external-verify.sh`. **ROADMAP:** T-PB-B / T-22/T-38. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs`. **Dissolution:** delete when modeled `run_target_verification` exercises `rust_r2a.dag` / `rust_r2b.dag` / `rust_r3_external.dag` without this bridge. **Interim ratchet:** nine tests in module (fixture authority + happy/falsification or runtime outcomes per claim). R2b sub-claims 3–4 remain `not_checked` until explicit `-C overflow-checks` runner lands (quick-tern-735). |
 | `src/v3/compiler/tests/integration/v4_bin_main_dag_smoke_test.rs` | **T-15** (`src/v4/bin/main.dag` — trampoline **`String`** authority + B1 digest **placeholder** `Node`s; closed-tree invariant #2 / pure-bootstrap zero-floor per `docs/design-pure-bootstrap-zero.md`). **Grounded-indicator authoring on `main.dag` is HOLD** pending hub-relayed canonical spec (operator-direct format under-spec; pending canonical spec). **ROADMAP:** `_internal/ROADMAP_OPS.md` § **Nine lanes** row **T-PB-B** / `pb_rust_tests_outside_residual_zero`. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs` land in the same PR as the smoke harness. **Dissolution:** remove when `main.dag` is exercised only by `.dag` `TestClaim` rows / a generated harness without this per-file Rust probe. **Interim ratchet:** `v4_bin_main_dag_tokenizes_and_parses_with_trampoline_source_anchor` runs `tokenize_for_test` + `parse_for_test` on the pinned `include_str!` source and asserts the trampoline / stub `data` identifiers plus the escaped `include!` spelling remain present in source text (full `compile_to_dag` on `main.dag` alone is deferred: `import v4.std.node` is not linked in the single-file harness). |
 | `src/v3/compiler/tests/integration/v4_t15_self_host_fixed_point_harness_test.rs` | **T-15** (`src/v4/TASKS.md` §T-15 — `bin/main.dag` trampoline authority + bootstrap `FixptStage1Stage2` stage1==stage2 wiring, **not** stage0==stage1; `claim_t15_self_host_fixed_point.dag` EqualsClaim over digest operand placeholders; optional v2 `gunbc compile` with `main.dag` entry root when `target/release/gunbc` exists). **ROADMAP:** `_internal/ROADMAP_OPS.md` § **Nine lanes** row **T-PB-B** / `pb_rust_tests_outside_residual_zero`. **PR receipt (P5 Mechanism (b)):** this INVARIANTS row + matching `EXPECTED_HAND_AUTHORED_TEST` line in `sg0_census_test.rs` land in the same PR as the harness + `claim_t15_self_host_fixed_point.dag`. **Dissolution:** remove when B1 merkle `content_hash` pins + T-22 eval execute the Equals probe and bootstrap fixpt without host structural receipts. **Interim ratchet:** `t_15_self_host_fixed_point` (TASKS.md CI gate name) tokenize/parse `main.dag`, `bootstrap.dag`, `self_host.dag`, and the T-15 claim; assert trampoline + fixpt stage1/stage2 digest convergence strings in `bootstrap_plan_well_formed`; assert `self_host_fixed_point_validate` stays fail-closed; optional v2 entry-root compile receipt. |

scripts/ci-merge/sg0-pr-body-append.4022.txt

@@ -0,0 +1,3 @@
+SG-0 hand-path delta: +1
+
+SG-0 pairing: (c) Net +1 on `EXPECTED_HAND_AUTHORED_TEST` for `v4_leaf_model_python_r1_test.rs` (INVARIANTS §P5(b) Phase 1 leaf-model python R1 boundary CPython ratchet per PR #3938 §11.4 W2.6; pairs with `scripts/v4-leaf-model-python-r1-verify.sh`). Follow-up dispatch: retire when T-22 modeled `run_target_verification` exercises `src/v4/test/claim/language_model/python_r1.dag` without this hand-Rust bridge — gunb-ai/gunbc#4022 / T-PB-B `pb_rust_tests_outside_residual_zero` in `_internal/ROADMAP_OPS.md`.

scripts/v4-leaf-model-python-r1-verify.sh

@@ -0,0 +1,174 @@
+#!/usr/bin/env bash
+# scripts/v4-leaf-model-python-r1-verify.sh
+#
+# Phase 1 leaf-model verification host runner — python.dag R1 (int surface spelling).
+# Authority: src/v4/lens/leaf_model_verification.dag (fixture sources) +
+#   src/v4/test/claim/language_model/python_r1.dag (claim + receipt shape).
+#
+# Exercises CPython on happy + falsification fixtures; emits JSON receipt.
+# Falsification probe expects NameError (undefined `i32` annotation) per W2.6 mirror of
+# rust.dag R1 (wrong surface spelling for the claimed primitive).
+#
+# Dissolve-on-arrival: delete when T-22 modeled `run_target_verification` owns python3
+# invocation and structured TestClaimRun verdicts replace this host bridge (same
+# trigger as src/v3/compiler/tests/boundary/v4_leaf_model_python_r1_test.rs).
+
+set -euo pipefail
+
+root="$(git rev-parse --show-toplevel 2>/dev/null || pwd)"
+cd "$root"
+
+fixture_dag="src/v4/lens/leaf_model_verification.dag"
+if [[ ! -f "$fixture_dag" ]]; then
+  echo "error: missing fixture authority at $fixture_dag" >&2
+  exit 1
+fi
+
+if ! command -v python3 >/dev/null 2>&1; then
+  echo "error: python3 not on PATH — required for leaf-model python R1 verification" >&2
+  exit 1
+fi
+
+eval "$(python3 - "$fixture_dag" <<'PY'
+from __future__ import annotations
+
+import re
+import shlex
+import sys
+from pathlib import Path
+
+path = Path(sys.argv[1])
+text = path.read_text()
+
+def extract(name: str) -> str:
+    pattern = rf'^data {name}: String = "(.*)"\s*$'
+    for line in text.splitlines():
+        m = re.match(pattern, line)
+        if m:
+            return bytes(m.group(1), "utf-8").decode("unicode_escape")
+    raise SystemExit(f"error: {path}: missing data {name}: String = ...")
+
+happy = extract("python_r1_happy_fixture_source")
+falsification = extract("python_r1_falsification_fixture_source")
+print(f"happy_source={shlex.quote(happy)}")
+print(f"falsification_source={shlex.quote(falsification)}")
+PY
+)"
+
+run_suffix="${GITHUB_RUN_ID:-local}-${GITHUB_RUN_ATTEMPT:-$$}"
+tmp_root="${RUNNER_TEMP:-/tmp}"
+scratch="${tmp_root}/v4-leaf-model-python-r1-${run_suffix}"
+rm -rf "$scratch"
+mkdir -p "$scratch"
+
+exercise_python_fixture() {
+  local label="$1"
+  local source="$2"
+  local src_path="${scratch}/${label}.py"
+  local stderr_path="${scratch}/${label}.stderr"
+  printf '%s' "$source" >"$src_path"
+  set +e
+  python3 -m py_compile "$src_path" 2>"$stderr_path"
+  local py_compile_status=$?
+  if [[ "$py_compile_status" -ne 0 ]]; then
+    echo "$py_compile_status" >"${scratch}/${label}.exit"
+    cat "$stderr_path"
+    return
+  fi
+  python3 "$src_path" 2>>"$stderr_path"
+  local exec_status=$?
+  set -e
+  echo "$exec_status" >"${scratch}/${label}.exit"
+  cat "$stderr_path"
+}
+
+echo "=== leaf-model R1: python3 happy fixture (python.dag int surface spelling) ==="
+happy_stderr="$(exercise_python_fixture happy "$happy_source")"
+happy_status="$(cat "${scratch}/happy.exit")"
+
+echo "=== leaf-model R1: python3 falsification fixture (NameError probe) ==="
+falsification_stderr="$(exercise_python_fixture falsification "$falsification_source")"
+falsification_status="$(cat "${scratch}/falsification.exit")"
+
+happy_pass=false
+falsification_pass=false
+if [[ "$happy_status" -eq 0 ]]; then
+  happy_pass=true
+fi
+if [[ "$falsification_status" -ne 0 ]] && grep -qE 'NameError: name .i32. is not defined' <<<"$falsification_stderr"; then
+  falsification_pass=true
+fi
+
+proven=false
+if [[ "$happy_pass" == true && "$falsification_pass" == true ]]; then
+  proven=true
+fi
+
+export V4_PYTHON_R1_HAPPY_STATUS="$happy_status"
+export V4_PYTHON_R1_FALSIFICATION_STATUS="$falsification_status"
+export V4_PYTHON_R1_HAPPY_PASS="$happy_pass"
+export V4_PYTHON_R1_FALSIFICATION_PASS="$falsification_pass"
+export V4_PYTHON_R1_PROVEN="$proven"
+export V4_PYTHON_R1_FALSIFICATION_STDERR="$falsification_stderr"
+
+python3 - <<'PY'
+import json
+import os
+import re
+
+stderr = os.environ.get("V4_PYTHON_R1_FALSIFICATION_STDERR", "")
+print(
+    json.dumps(
+        {
+            "schema": "scripts/v4-leaf-model-python-r1-verify.sh::host_receipt_v1",
+            "claim_id": "PythonR1IntSurfaceSpelling",
+            "happy": {
+                "python_exit": int(os.environ["V4_PYTHON_R1_HAPPY_STATUS"]),
+                "verdict": "Pass"
+                if os.environ["V4_PYTHON_R1_HAPPY_PASS"] == "true"
+                else "Fail",
+            },
+            "falsification": {
+                "python_exit": int(os.environ["V4_PYTHON_R1_FALSIFICATION_STATUS"]),
+                "expected_diagnostic": "NameError:i32",
+                "name_error_i32_observed": bool(
+                    re.search(r"NameError: name 'i32' is not defined", stderr)
+                ),
+                "verdict": "Pass"
+                if os.environ["V4_PYTHON_R1_FALSIFICATION_PASS"] == "true"
+                else "Fail",
+            },
+            "proven": os.environ["V4_PYTHON_R1_PROVEN"] == "true",
+        },
+        indent=2,
+    )
+)
+PY
+
+if [[ "$proven" != true ]]; then
+  echo "error: leaf-model python R1 verification failed (happy_pass=${happy_pass} falsification_pass=${falsification_pass})" >&2
+  if [[ "$happy_pass" != true ]]; then
+    echo "--- happy python stderr ---" >&2
+    printf '%s\n' "$happy_stderr" >&2
+  fi
+  if [[ "$falsification_pass" != true ]]; then
+    echo "--- falsification python stderr ---" >&2
+    printf '%s\n' "$falsification_stderr" >&2
+  fi
+  exit 1
+fi
+
+if [[ -n "${GITHUB_STEP_SUMMARY:-}" ]]; then
+  {
+    echo "### Leaf-model verification — python.dag R1 (int surface spelling)"
+    echo ""
+    echo "| path | verdict |"
+    echo "| --- | --- |"
+    echo "| happy \`def r1_test() -> int: return 0\` | Pass (python3 clean) |"
+    echo "| falsification \`def r1_test() -> i32: ...\` | Pass (NameError on i32) |"
+    echo ""
+    echo "_Authority: \`${fixture_dag}\` + \`src/v4/test/claim/language_model/python_r1.dag\`_"
+  } >> "$GITHUB_STEP_SUMMARY"
+fi
+
+echo "leaf-model python R1 verification PROVEN: happy runs clean; falsification rejected with NameError on i32"

src/v3/compiler/tests/boundary/v4_leaf_model_python_r1_test.rs

@@ -0,0 +1,121 @@
+//! **Layer:** boundary (TESTING.md § test layers — CPython exercise for v4 leaf-model python R1).
+//!
+//! Phase 1: python.dag claim R1 (int surface spelling) — fixture authority in
+//! `src/v4/lens/leaf_model_verification.dag`; host runner
+//! `scripts/v4-leaf-model-python-r1-verify.sh`.
+//!
+//! **P5 receipt:** matching `_internal/INVARIANTS_OPS.md` row +
+//! `EXPECTED_HAND_AUTHORED_TEST` literal in `sg0_census_test.rs` (same PR).
+//! **Dissolution:** retire when T-22 eval + modeled `run_target_verification` owns
+//! python3 invocation without this hand-Rust bridge.
+
+use std::io::Write;
+use std::process::Command;
+
+const FIXTURE_DAG: &str = include_str!("../../../../v4/lens/leaf_model_verification.dag");
+const CLAIM_DAG: &str = include_str!("../../../../v4/test/claim/language_model/python_r1.dag");
+
+const HAPPY_FIXTURE: &str = "def r1_test() -> int:\n    return 0\n";
+const FALSIFICATION_FIXTURE: &str = "def r1_test() -> i32:\n    return 0\n";
+
+fn unescape_dag_string_literal(body: &str) -> String {
+    let mut out = String::new();
+    let mut chars = body.chars();
+    while let Some(c) = chars.next() {
+        if c == '\\' {
+            match chars.next() {
+                Some('n') => out.push('\n'),
+                Some('"') => out.push('"'),
+                Some('\\') => out.push('\\'),
+                Some(other) => {
+                    out.push('\\');
+                    out.push(other);
+                }
+                None => out.push('\\'),
+            }
+        } else {
+            out.push(c);
+        }
+    }
+    out
+}
+
+fn extract_fixture_source(dag_text: &str, data_name: &str) -> Option<String> {
+    let needle = format!("data {data_name}: String = \"");
+    let line = dag_text.lines().find(|l| l.starts_with(&needle))?;
+    let rest = line.strip_prefix(&needle)?.strip_suffix('"')?;
+    Some(unescape_dag_string_literal(rest))
+}
+
+fn scratch_dir(label: &str) -> std::path::PathBuf {
+    let suffix = std::process::id();
+    std::env::temp_dir().join(format!("v4_leaf_model_python_r1_{label}_{suffix}"))
+}
+
+fn exercise_fixture(label: &str, source: &str) -> (i32, String) {
+    let tmp_dir = scratch_dir(label);
+    let _ = std::fs::remove_dir_all(&tmp_dir);
+    std::fs::create_dir_all(&tmp_dir).expect("create scratch dir");
+    let src_path = tmp_dir.join(format!("{label}.py"));
+    std::fs::File::create(&src_path)
+        .and_then(|mut f| f.write_all(source.as_bytes()))
+        .expect("write fixture source");
+
+    let py_compile = Command::new("python3")
+        .args(["-m", "py_compile"])
+        .arg(&src_path)
+        .output()
+        .expect("invoke python3 -m py_compile");
+    if !py_compile.status.success() {
+        let stderr = String::from_utf8_lossy(&py_compile.stderr).into_owned();
+        let _ = std::fs::remove_dir_all(&tmp_dir);
+        return (py_compile.status.code().unwrap_or(1), stderr);
+    }
+
+    let exec = Command::new("python3")
+        .arg(&src_path)
+        .output()
+        .expect("invoke python3 on fixture");
+    let stderr = String::from_utf8_lossy(&exec.stderr).into_owned();
+    let status = exec.status.code().unwrap_or(1);
+    let _ = std::fs::remove_dir_all(&tmp_dir);
+    (status, stderr)
+}
+
+#[test]
+fn v4_leaf_model_python_r1_fixture_strings_match_dag_authority() {
+    let happy = extract_fixture_source(FIXTURE_DAG, "python_r1_happy_fixture_source")
+        .expect("python_r1_happy_fixture_source in lens/leaf_model_verification.dag");
+    let falsification =
+        extract_fixture_source(FIXTURE_DAG, "python_r1_falsification_fixture_source")
+            .expect("python_r1_falsification_fixture_source in lens/leaf_model_verification.dag");
+    assert_eq!(happy, HAPPY_FIXTURE);
+    assert_eq!(falsification, FALSIFICATION_FIXTURE);
+    assert!(
+        CLAIM_DAG.contains("python_r1_happy_fixture_source")
+            && CLAIM_DAG.contains("python_surface_spelling_int"),
+        "claim module must reference fixture + fact anchors"
+    );
+}
+
+#[test]
+fn v4_leaf_model_python_r1_happy_fixture_python_accepts() {
+    let (status, stderr) = exercise_fixture("happy", HAPPY_FIXTURE);
+    assert_eq!(
+        status, 0,
+        "python3 should accept R1 happy fixture; stderr:\n{stderr}"
+    );
+}
+
+#[test]
+fn v4_leaf_model_python_r1_falsification_fixture_python_name_error() {
+    let (status, stderr) = exercise_fixture("falsification", FALSIFICATION_FIXTURE);
+    assert_ne!(
+        status, 0,
+        "falsification fixture must not run clean (wrong int surface spelling i32)"
+    );
+    assert!(
+        stderr.contains("NameError: name 'i32' is not defined"),
+        "expected NameError on undefined i32 annotation; stderr:\n{stderr}"
+    );
+}