diff --git a/0-Core-Formalism/lean/Semantics/Semantics/AVMIsa/Emit.lean b/0-Core-Formalism/lean/Semantics/Semantics/AVMIsa/Emit.lean
index 6f72c69b..3a167064 100644
--- a/0-Core-Formalism/lean/Semantics/Semantics/AVMIsa/Emit.lean
+++ b/0-Core-Formalism/lean/Semantics/Semantics/AVMIsa/Emit.lean
@@ -216,14 +216,18 @@ def emitRrcCorpus278 : String :=
   let total      := classified.totalRows
   let passed     := classified.candidateRows
   let held       := total - passed
-  -- 5. Emit JSON — AVM is the output boundary
+  -- 5. Emit JSON — AVM is the output boundary.
+  -- In Lean s! strings: \{ = literal {, } = literal }, {expr} = interpolation.
+  -- The summary sub-object is assembled as a plain String, then interpolated.
+  let summaryStr :=
+    s!"\{\"total\":{total},\"passed_alignment\":{passed},\"held\":{held}," ++
+    s!"\"not_promoted\":{total}}"
   s!"\{\"schema\":\"avm_rrc_corpus278_v1\"," ++
   s!"\"claim_boundary\":\"admissibility-and-routing-pass-only;not-promoted\"," ++
   s!"\"avm_canaries_passed\":{jsonBool avmOk}," ++
   s!"\"bundle_receipt_valid\":{jsonBool bundleReceipt.valid}," ++
-  s!"\"summary\":\{\"total\":{total},\"passed_alignment\":{passed},\"held\":{held}," ++
-  s!"\"not_promoted\":{total}}}," ++
-  s!"\"rows\":{classified.json}}"
+  s!"\"summary\":{summaryStr}," ++
+  s!"\"rows\":{classified.rowsJson}}"
 
 -- ─────────────────────────────────────────────────────────────────────────────
 -- §8  Proof-of-life eval witnesses
@@ -251,4 +255,9 @@ open Semantics.RRC.Corpus278 in
   let r := emitCorpus "rrc_corpus278_v1" corpus278
   (r.totalRows, r.candidateRows, r.totalRows - r.candidateRows)
 
+-- Full end-to-end JSON: AVM-stamped, 278 rows, claim_boundary, schema=avm_rrc_corpus278_v1.
+-- Captured by emit278_extract.py → emit278.json (validated by python3 -m json.tool).
+-- expect: JSON string starting with {"schema":"avm_rrc_corpus278_v1",...}
+#eval emitRrcCorpus278
+
 end Semantics.AVMIsa.Emit
diff --git a/0-Core-Formalism/lean/Semantics/Semantics/RRC/Emit.lean b/0-Core-Formalism/lean/Semantics/Semantics/RRC/Emit.lean
index 5d2b715a..fbe0ea3c 100644
--- a/0-Core-Formalism/lean/Semantics/Semantics/RRC/Emit.lean
+++ b/0-Core-Formalism/lean/Semantics/Semantics/RRC/Emit.lean
@@ -375,7 +375,8 @@ structure EmitResult where
   rows          : List RrcRow
   totalRows     : Nat
   candidateRows : Nat     -- rows where receipt.valid = true (alignment passed)
-  json          : String
+  rowsJson      : String  -- JSON array string of all rows (for embedding in outer envelopes)
+  json          : String  -- full JSON envelope including schema/summary/rows
   deriving Repr
 
 /-- Generic corpus emitter: compile any list of FixtureRows and emit a
@@ -384,6 +385,7 @@ structure EmitResult where
 def emitCorpus (schema : String) (corpus : List FixtureRow) : EmitResult :=
   let rows       := corpus.map compileRow
   let candidates := rows.filter (·.receipt.valid)
+  let rowsJson   := jRowList rows
   let summary    :=
     s!"\{\"total\":{rows.length}," ++
     s!"\"passed_alignment\":{candidates.length}," ++
@@ -394,10 +396,11 @@ def emitCorpus (schema : String) (corpus : List FixtureRow) : EmitResult :=
     s!"\{\"schema\":{jStr schema}," ++
     s!"\"claim_boundary\":\"admissibility-and-routing-pass-only\"," ++
     s!"\"summary\":{summary}," ++
-    s!"\"rows\":{jRowList rows}}"
+    s!"\"rows\":{rowsJson}}"
   { rows          := rows
     totalRows     := rows.length
     candidateRows := candidates.length
+    rowsJson      := rowsJson
     json          := json }
 
 def emitFixture : EmitResult :=
diff --git a/4-Infrastructure/shim/emit278_extract.py b/4-Infrastructure/shim/emit278_extract.py
new file mode 100644
index 00000000..e45874a2
--- /dev/null
+++ b/4-Infrastructure/shim/emit278_extract.py
@@ -0,0 +1,136 @@
+#!/usr/bin/env python3
+# /// script
+# requires-python = ">=3.10"
+# dependencies = []
+# ///
+"""
+emit278_extract.py — run `lake build Semantics.AVMIsa.Emit` and capture the
+`#eval emitRrcCorpus278` output, writing it as emit278.json.
+
+Python role: subprocess + I/O only.
+Lean role: all alignment-gate, receipt-stamping, and JSON-emission logic.
+
+Usage:
+    python3 4-Infrastructure/shim/emit278_extract.py
+    python3 4-Infrastructure/shim/emit278_extract.py --out /tmp/emit278.json
+    python3 4-Infrastructure/shim/emit278_extract.py --validate-only
+"""
+from __future__ import annotations
+import argparse, json, re, subprocess, sys
+from pathlib import Path
+
+ROOT = Path("/home/allaun/Research Stack")
+LEAN_DIR = ROOT / "0-Core-Formalism/lean/Semantics"
+DEFAULT_OUT = ROOT / "shared-data/data/stack_solidification/emit278.json"
+
+# The #eval for emitRrcCorpus278 is in AVMIsa/Emit.lean — its info: line
+# will contain the string starting with {"schema":"avm_rrc_corpus278_v1",...}
+# In the raw lake output the JSON string is Lean-repr-escaped, so quotes appear
+# as \" — we search for both forms.
+MARKER = 'avm_rrc_corpus278_v1'
+
+
+def build_and_capture() -> str:
+    """Run lake build and return the raw info: line containing MARKER."""
+    print("Running: lake build Semantics.AVMIsa.Emit ...", file=sys.stderr)
+    result = subprocess.run(
+        ["lake", "build", "Semantics.AVMIsa.Emit"],
+        cwd=str(LEAN_DIR),
+        capture_output=True,
+        text=True,
+    )
+    # lake prints #eval output to stderr as "info: <file>:<line>:<col>: <value>"
+    combined = result.stdout + result.stderr
+    for line in combined.splitlines():
+        if MARKER in line:
+            return line
+    raise RuntimeError(
+        f"MARKER '{MARKER}' not found in lake build output.\n"
+        f"Return code: {result.returncode}\n"
+        f"Last 20 lines:\n" + "\n".join(combined.splitlines()[-20:])
+    )
+
+
+def extract_json(info_line: str) -> str:
+    """
+    Strip the `info: <path>:<line>:<col>: ` prefix and outer Lean string quotes,
+    then unescape Lean string escapes to produce a raw JSON string.
+    """
+    # info: Semantics/AVMIsa/Emit.lean:260:0: "{...json...}"
+    # We want everything after the last `: ` that starts with `"`
+    m = re.search(r'info:.*?:\d+:\d+:\s*(".*)', info_line, re.DOTALL)
+    if not m:
+        raise RuntimeError(f"Cannot parse info line: {info_line[:200]}")
+    quoted = m.group(1).strip()
+    # The Lean repr wraps the string in outer quotes and escapes internal quotes.
+    # Remove outer quotes and unescape.
+    if quoted.startswith('"') and quoted.endswith('"'):
+        inner = quoted[1:-1]
+    else:
+        raise RuntimeError(f"Expected outer quotes in: {quoted[:200]}")
+    # Unescape Lean string escapes (only \\ and \" are used in our JSON emitter)
+    inner = inner.replace('\\"', '"').replace('\\\\', '\\')
+    return inner
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser(description="Extract emit278.json from lake build output")
+    ap.add_argument("--out", default=str(DEFAULT_OUT), help="Output JSON path")
+    ap.add_argument("--validate-only", action="store_true",
+                    help="Parse and validate JSON only; do not write file")
+    args = ap.parse_args()
+
+    info_line = build_and_capture()
+    json_str  = extract_json(info_line)
+
+    # Validate JSON
+    try:
+        parsed = json.loads(json_str)
+    except json.JSONDecodeError as e:
+        print(f"ERROR: JSON parse failed: {e}", file=sys.stderr)
+        print(f"First 500 chars: {json_str[:500]}", file=sys.stderr)
+        sys.exit(1)
+
+    # Sanity checks
+    schema = parsed.get("schema")
+    total  = parsed.get("summary", {}).get("total")
+    claim  = parsed.get("claim_boundary")
+    print(f"schema            : {schema}", file=sys.stderr)
+    print(f"total_rows        : {total}", file=sys.stderr)
+    print(f"claim_boundary    : {claim}", file=sys.stderr)
+    print(f"avm_canaries_pass : {parsed.get('avm_canaries_passed')}", file=sys.stderr)
+    print(f"bundle_receipt_ok : {parsed.get('bundle_receipt_valid')}", file=sys.stderr)
+    rows_val  = parsed.get("rows", [])
+    row_count = len(rows_val) if isinstance(rows_val, list) else \
+                len(rows_val.get("rows", [])) if isinstance(rows_val, dict) else -1
+    print(f"rows in JSON      : {row_count}", file=sys.stderr)
+
+    if schema != "avm_rrc_corpus278_v1":
+        print(f"ERROR: unexpected schema '{schema}'", file=sys.stderr)
+        sys.exit(1)
+    if total != 278 or row_count != 278:
+        print(f"ERROR: expected 278 rows, got total={total}, rows={row_count}", file=sys.stderr)
+        sys.exit(1)
+
+    if args.validate_only:
+        print("Validation OK (--validate-only; file not written)", file=sys.stderr)
+        return
+
+    out = Path(args.out)
+    out.parent.mkdir(parents=True, exist_ok=True)
+    out.write_text(json.dumps(parsed, indent=2))
+    print(f"Wrote {out}", file=sys.stderr)
+    print(f"Validation: python3 -m json.tool {out} > /dev/null", file=sys.stderr)
+    # Final python3 -m json.tool validation
+    check = subprocess.run(
+        ["python3", "-m", "json.tool", str(out)],
+        capture_output=True, text=True
+    )
+    if check.returncode != 0:
+        print(f"ERROR: json.tool validation failed:\n{check.stderr}", file=sys.stderr)
+        sys.exit(1)
+    print("json.tool validation PASSED", file=sys.stderr)
+
+
+if __name__ == "__main__":
+    main()