diff --git a/.github/workflows/emit-bitexact-gate.yml b/.github/workflows/emit-bitexact-gate.yml
index 8f620b29a..98d8250e6 100644
--- a/.github/workflows/emit-bitexact-gate.yml
+++ b/.github/workflows/emit-bitexact-gate.yml
@@ -20,6 +20,7 @@ on:
       # rewrites the C emitter merges with the cross-target proof never running.
       - "bootstrap/**"
       - "cli/**"
+      - "tools/check_specs_parse.py"
       - "tools/gft_backprop_microcode.py"
       - "tools/verify_emit_bitexact.py"
       - "tools/verify_multitarget.py"
@@ -54,6 +55,15 @@ jobs:
       - name: Build t27c
         run: cargo build --release -p t27c
 
+      # Precondition for everything below. A spec that does not parse produces no
+      # backend output at all, and the downstream scripts report that as "the C
+      # backend failed to build" -- which sent four days of readers to the wrong
+      # subsystem. Ask the parser first, and print its own message.
+      - name: Required specs parse (negative control)
+        run: python3 tools/check_specs_parse.py --self-check
+      - name: Required specs parse
+        run: python3 tools/check_specs_parse.py
+
       - name: Prove generated RTL == GF-T model (bit-exact) + synthesizes
         run: python3 tools/verify_emit_bitexact.py
 
diff --git a/docs/NOW.md b/docs/NOW.md
index 552d43126..db529269a 100644
--- a/docs/NOW.md
+++ b/docs/NOW.md
@@ -1,3 +1,17 @@
+# NOW -- one missing brace, and three layers that named the wrong subsystem (2026-08-18)
+
+Last updated: 2026-08-18
+
+## specs: close 27 unterminated test blocks; the cross-target proof was never running (Closes #2185)
+
+- **`emit-bitexact` was red since 2026-08-14 because of one character.** A bulk edit appended `test <name>_w339_batch_depth_invariant_2 {` to 27 spec files and omitted the closing `}` in every one, so the parser hits the next `test` keyword while still inside the block
+- **Three layers each reported something else, and only the innermost was true.** The CI gate said `IGLA RACE CROSS-TARGET MISMATCH`; `verify_igla_race.py` said `FAIL: C backend failed to build/run`; `t27c` said `parse error in fn 'ternary_mac_w339_batch_depth_invariant_2' near line 1815: unexpected token after expression statement: KwTest` -- file, function, line and token, exactly right. The script runs its builds with `capture_output=True` and inspects only `returncode`, so that message was collected and thrown away
+- **A diagnostic that names the wrong subsystem costs more than none.** "The C and Rust backends diverge" is a far more alarming claim than "a spec has a typo", and it is where four days of reading went
+- **There was no cross-target divergence.** With the braces closed, `verify_igla_race.py` exits 0: C and Rust each match the reference bit-exact over 800 vectors, for both `ternary_mul/mac` and `systolic_ternary_pe` with its i16 accumulator. #2184 is corrected accordingly -- the `i16 + i8` no-cast gap in `gen_rust` is real, is documented in the script, and is worked around there; it was never what made the gate red
+- **Gate:** `tools/check_specs_parse.py` asks the question the three layers did not -- does `t27c` accept the file -- and prints the compiler's own message. Negative control plants an unclosed block and proves the gate rejects it. Wired in ahead of every other step, because it is their precondition
+- **Reported, not fixed:** closing the braces reveals 15 of 27 igla specs still failing on unrelated parser features (`unknown cast target type f32`, `Unexpected top-level token: KwModule`), overlapping #2174. Different class, left alone
+- The `paths:` edit silently failed on an indentation mismatch for the second time today. Caught by a negative control over the filter, not by reading it
+
 # NOW -- the bit-exactness gate could not see the compiler (2026-08-18)
 
 Last updated: 2026-08-18
diff --git a/specs/igla/coder/arch.t27 b/specs/igla/coder/arch.t27
index 1b5ad9ca0..367a43f75 100644
--- a/specs/igla/coder/arch.t27
+++ b/specs/igla/coder/arch.t27
@@ -2329,7 +2329,7 @@ test arch_w339_batch_depth_invariant_1 {
 test arch_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (72→73)
 test arch_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test arch_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/bench_proxy.t27 b/specs/igla/coder/bench_proxy.t27
index ef8bbb15f..71d5d96dc 100644
--- a/specs/igla/coder/bench_proxy.t27
+++ b/specs/igla/coder/bench_proxy.t27
@@ -1231,7 +1231,7 @@ test bench_proxy_w339_batch_depth_invariant_1 {
 test bench_proxy_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (72→73)
 test bench_proxy_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test bench_proxy_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/benchmark.t27 b/specs/igla/coder/benchmark.t27
index 5ec007f87..5bb026046 100644
--- a/specs/igla/coder/benchmark.t27
+++ b/specs/igla/coder/benchmark.t27
@@ -4617,7 +4617,7 @@ test benchmark_w339_batch_depth_invariant_1 {
 test benchmark_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test benchmark_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test benchmark_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/dataset.t27 b/specs/igla/coder/dataset.t27
index efd1672dc..64d1bcc73 100644
--- a/specs/igla/coder/dataset.t27
+++ b/specs/igla/coder/dataset.t27
@@ -2450,7 +2450,7 @@ test dataset_w339_batch_depth_invariant_1 {
 test dataset_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (72→73)
 test dataset_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test dataset_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/eval.t27 b/specs/igla/coder/eval.t27
index 8e6bc20ac..fe6dfb98c 100644
--- a/specs/igla/coder/eval.t27
+++ b/specs/igla/coder/eval.t27
@@ -3631,7 +3631,7 @@ test eval_w339_batch_depth_invariant_1 {
 test eval_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (74→75)
 test eval_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test eval_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/pipeline.t27 b/specs/igla/coder/pipeline.t27
index 42a3bac3d..7c3a995b9 100644
--- a/specs/igla/coder/pipeline.t27
+++ b/specs/igla/coder/pipeline.t27
@@ -2253,7 +2253,7 @@ test pipeline_w339_batch_depth_invariant_1 {
 test pipeline_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test pipeline_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test pipeline_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/prm.t27 b/specs/igla/coder/prm.t27
index 4b9c4f09c..8cbbc3f9c 100644
--- a/specs/igla/coder/prm.t27
+++ b/specs/igla/coder/prm.t27
@@ -1559,7 +1559,7 @@ test prm_w339_batch_depth_invariant_1 {
 test prm_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test prm_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test prm_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/tokenizer.t27 b/specs/igla/coder/tokenizer.t27
index 03eeabea6..9c7935f2a 100644
--- a/specs/igla/coder/tokenizer.t27
+++ b/specs/igla/coder/tokenizer.t27
@@ -1381,7 +1381,7 @@ test tokenizer_w339_batch_depth_invariant_1 {
 test tokenizer_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test tokenizer_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test tokenizer_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/training.t27 b/specs/igla/coder/training.t27
index b72e4fea6..af04667c5 100644
--- a/specs/igla/coder/training.t27
+++ b/specs/igla/coder/training.t27
@@ -1587,7 +1587,7 @@ test training_w339_batch_depth_invariant_1 {
 test training_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test training_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test training_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/coder/weights.t27 b/specs/igla/coder/weights.t27
index 81c4c48dd..ddc60118e 100644
--- a/specs/igla/coder/weights.t27
+++ b/specs/igla/coder/weights.t27
@@ -1460,7 +1460,7 @@ test weights_w339_batch_depth_invariant_1 {
 test weights_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — CODER depth +1 (73→74)
 test weights_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test weights_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/adder_tree.t27 b/specs/igla/race/adder_tree.t27
index 0ccd84a7d..c29c04697 100644
--- a/specs/igla/race/adder_tree.t27
+++ b/specs/igla/race/adder_tree.t27
@@ -1594,7 +1594,7 @@ test adder_tree_w339_batch_depth_invariant_1 {
 test adder_tree_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (82→83)
 test adder_tree_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test adder_tree_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/backend.t27 b/specs/igla/race/backend.t27
index 0c3dd5711..a9be9fbe1 100644
--- a/specs/igla/race/backend.t27
+++ b/specs/igla/race/backend.t27
@@ -1934,7 +1934,7 @@ test backend_w339_batch_depth_invariant_1 {
 test backend_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (85→86)
 test backend_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test backend_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/bram_weights.t27 b/specs/igla/race/bram_weights.t27
index ba7db7044..327acff1d 100644
--- a/specs/igla/race/bram_weights.t27
+++ b/specs/igla/race/bram_weights.t27
@@ -1588,7 +1588,7 @@ test bram_weights_w339_batch_depth_invariant_1 {
 test bram_weights_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test bram_weights_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test bram_weights_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/cordic.t27 b/specs/igla/race/cordic.t27
index 4572c01f6..761e940fc 100644
--- a/specs/igla/race/cordic.t27
+++ b/specs/igla/race/cordic.t27
@@ -1601,7 +1601,7 @@ test cordic_w339_batch_depth_invariant_1 {
 test cordic_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test cordic_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test cordic_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/cordic_fixed.t27 b/specs/igla/race/cordic_fixed.t27
index d234ccd10..dc00568f2 100644
--- a/specs/igla/race/cordic_fixed.t27
+++ b/specs/igla/race/cordic_fixed.t27
@@ -1615,7 +1615,7 @@ test cordic_fixed_w339_batch_depth_invariant_1 {
 test cordic_fixed_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (84→85)
 test cordic_fixed_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test cordic_fixed_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/cordic_top.t27 b/specs/igla/race/cordic_top.t27
index 65b4fad40..4cf284ed8 100644
--- a/specs/igla/race/cordic_top.t27
+++ b/specs/igla/race/cordic_top.t27
@@ -1640,7 +1640,7 @@ test cordic_top_w339_batch_depth_invariant_1 {
 test cordic_top_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (84→85)
 test cordic_top_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test cordic_top_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/eda.t27 b/specs/igla/race/eda.t27
index 6dc4ea1e2..8e4fd5df8 100644
--- a/specs/igla/race/eda.t27
+++ b/specs/igla/race/eda.t27
@@ -1829,7 +1829,7 @@ test eda_w339_batch_depth_invariant_1 {
 test eda_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test eda_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test eda_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/formal.t27 b/specs/igla/race/formal.t27
index 67ddaa93d..c6cfb629c 100644
--- a/specs/igla/race/formal.t27
+++ b/specs/igla/race/formal.t27
@@ -1750,7 +1750,7 @@ test formal_w339_batch_depth_invariant_1 {
 test formal_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test formal_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test formal_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/gemm.t27 b/specs/igla/race/gemm.t27
index 186870366..f8d35cffb 100644
--- a/specs/igla/race/gemm.t27
+++ b/specs/igla/race/gemm.t27
@@ -1642,7 +1642,7 @@ test gemm_w339_batch_depth_invariant_1 {
 test gemm_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test gemm_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test gemm_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/opcodes.t27 b/specs/igla/race/opcodes.t27
index 81c44b1c9..f486688ee 100644
--- a/specs/igla/race/opcodes.t27
+++ b/specs/igla/race/opcodes.t27
@@ -1456,7 +1456,7 @@ test opcodes_w339_batch_depth_invariant_1 {
 test opcodes_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test opcodes_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test opcodes_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/rtl.t27 b/specs/igla/race/rtl.t27
index be1f732e9..173c959f1 100644
--- a/specs/igla/race/rtl.t27
+++ b/specs/igla/race/rtl.t27
@@ -1776,7 +1776,7 @@ test rtl_w339_batch_depth_invariant_1 {
 test rtl_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (83→84)
 test rtl_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test rtl_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/systolic_array.t27 b/specs/igla/race/systolic_array.t27
index f28984256..56b2c2d78 100644
--- a/specs/igla/race/systolic_array.t27
+++ b/specs/igla/race/systolic_array.t27
@@ -1755,7 +1755,7 @@ test systolic_array_w339_batch_depth_invariant_1 {
 test systolic_array_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (86→87)
 test systolic_array_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test systolic_array_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/systolic_ternary.t27 b/specs/igla/race/systolic_ternary.t27
index 71ac7522f..cf25acfc4 100644
--- a/specs/igla/race/systolic_ternary.t27
+++ b/specs/igla/race/systolic_ternary.t27
@@ -2004,7 +2004,7 @@ test systolic_ternary_w339_batch_depth_invariant_1 {
 test systolic_ternary_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool B depth +1 (99→100)
 test systolic_ternary_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test systolic_ternary_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/ternary_gemm.t27 b/specs/igla/race/ternary_gemm.t27
index 50c7d123b..b152b76be 100644
--- a/specs/igla/race/ternary_gemm.t27
+++ b/specs/igla/race/ternary_gemm.t27
@@ -1755,7 +1755,7 @@ test ternary_gemm_w339_batch_depth_invariant_1 {
 test ternary_gemm_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (82→83)
 test ternary_gemm_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test ternary_gemm_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/ternary_inference.t27 b/specs/igla/race/ternary_inference.t27
index 5ae878522..32269dbb1 100644
--- a/specs/igla/race/ternary_inference.t27
+++ b/specs/igla/race/ternary_inference.t27
@@ -1130,7 +1130,7 @@ test ternary_inference_w339_batch_depth_invariant_1 {
 test ternary_inference_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Integration depth +1 (82→83)
 test ternary_inference_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test ternary_inference_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/ternary_mac.t27 b/specs/igla/race/ternary_mac.t27
index ac3d6c9e3..0ddb5a5a3 100644
--- a/specs/igla/race/ternary_mac.t27
+++ b/specs/igla/race/ternary_mac.t27
@@ -1810,7 +1810,7 @@ test ternary_mac_w339_batch_depth_invariant_1 {
 test ternary_mac_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (82→83)
 test ternary_mac_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test ternary_mac_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/specs/igla/race/yosys.t27 b/specs/igla/race/yosys.t27
index 9930a4aec..24dada8fa 100644
--- a/specs/igla/race/yosys.t27
+++ b/specs/igla/race/yosys.t27
@@ -1785,7 +1785,7 @@ test yosys_w339_batch_depth_invariant_1 {
 test yosys_w339_batch_depth_invariant_2 {
   // Verify baseline properties for 15-variable accumulation
   assert(true)
-
+}
 // Wave Loop 340 — Pool A depth +1 (84→85)
 test yosys_w340_batch_depth_invariant_1 { /* verify baseline */ }
 test yosys_w340_batch_depth_invariant_2 { /* verify baseline */ }
diff --git a/tools/check_specs_parse.py b/tools/check_specs_parse.py
new file mode 100755
index 000000000..11a21036a
--- /dev/null
+++ b/tools/check_specs_parse.py
@@ -0,0 +1,129 @@
+#!/usr/bin/env python3
+"""Does every spec the cross-target gate depends on still parse?
+
+Written after a bulk edit dropped one closing brace in 27 files and nobody
+noticed for four days.
+
+`test X_w339_batch_depth_invariant_2 {` was appended to 27 specs with its `}`
+omitted, so the parser hit the next `test` keyword while still inside the block:
+
+    parse error in fn 'ternary_mac_w339_batch_depth_invariant_2' near line 1815:
+    unexpected token after expression statement: KwTest
+
+The message was exact. Nothing surfaced it, because three layers reported
+something else:
+
+  the CI gate said   IGLA RACE CROSS-TARGET MISMATCH
+  the script said    FAIL: C backend failed to build/run
+  the truth was      the spec does not parse, so no backend ever ran
+
+The script's own build helpers pass capture_output=True and inspect only
+returncode, so the compiler's message -- which named the file, the function and
+the line -- was collected and thrown away. A diagnostic that names the wrong
+subsystem costs more than no diagnostic: it sends the reader to the backend.
+
+This gate asks the one question those three layers did not: does `t27c` accept
+the file at all. It reports the compiler's own error verbatim.
+
+Usage:
+  tools/check_specs_parse.py                  gate over the required set
+  tools/check_specs_parse.py --all            every spec under specs/, reporting
+  tools/check_specs_parse.py --self-check     negative control
+
+Exits non-zero if a required spec does not parse.
+"""
+import glob
+import os
+import pathlib
+import subprocess
+import sys
+
+ROOT = pathlib.Path(__file__).resolve().parent.parent
+
+# Specs the cross-target bit-exactness proof consumes. These must parse; a PR
+# that breaks one is breaking the proof, not merely a file.
+REQUIRED = [
+    "specs/igla/race/ternary_mac.t27",
+    "specs/igla/race/systolic_ternary.t27",
+    "specs/ternary/gft_smul.t27",
+    "specs/ternary/gft_sadd.t27",
+]
+
+
+def find_t27c():
+    for p in ("target/release/t27c", "target/debug/t27c"):
+        c = ROOT / p
+        if c.exists():
+            return str(c)
+    return None
+
+
+def parses(t27c, spec):
+    """(ok, first line of the compiler's own error)."""
+    r = subprocess.run([t27c, "gen-c", spec], capture_output=True, text=True, cwd=ROOT)
+    if r.returncode == 0:
+        return True, ""
+    err = (r.stderr or r.stdout or "").strip().split("\n")
+    return False, err[0] if err else f"exit {r.returncode}, no message"
+
+
+def self_check(t27c):
+    """Plant an unclosed test block and prove the gate reports it."""
+    import tempfile, shutil
+    src = ROOT / REQUIRED[0]
+    with tempfile.TemporaryDirectory() as td:
+        bad = os.path.join(td, "bad.t27")
+        text = src.read_text(encoding="utf-8")
+        # remove the first closing brace of a test block -> the exact fault we hit
+        i = text.find("\n}\n", text.find("test "))
+        shutil.copy(src, bad)
+        pathlib.Path(bad).write_text(text[:i] + "\n" + text[i + 3:], encoding="utf-8")
+        ok_bad, msg = parses(t27c, bad)
+        ok_good, _ = parses(t27c, str(src))
+    print(f"  self-check: planted spec rejected = {not ok_bad}, real spec accepted = {ok_good}")
+    if not ok_bad:
+        print(f"              reported: {msg[:100]}")
+    return 0 if (not ok_bad and ok_good) else 1
+
+
+def main():
+    t27c = find_t27c()
+    if not t27c:
+        print("FAIL: t27c not built. Run: cargo build --release -p t27c")
+        return 1
+    if "--self-check" in sys.argv:
+        return self_check(t27c)
+
+    targets = (sorted(glob.glob(str(ROOT / "specs/**/*.t27"), recursive=True))
+               if "--all" in sys.argv else [str(ROOT / p) for p in REQUIRED])
+    bad = []
+    for spec in targets:
+        rel = os.path.relpath(spec, ROOT)
+        ok, msg = parses(t27c, spec)
+        if not ok:
+            bad.append((rel, msg))
+        elif "--all" not in sys.argv:
+            print(f"  ok   {rel}")
+
+    if "--all" in sys.argv:
+        print(f"\n  {len(targets) - len(bad)} of {len(targets)} specs parse")
+        for rel, msg in bad:
+            print(f"    {rel}\n      {msg[:120]}")
+        print("\n  --all is a report, not a gate: many specs fail on parser features")
+        print("  that are tracked separately. Only the REQUIRED set gates CI.")
+        return 0
+
+    if not bad:
+        print(f"\nOK: all {len(targets)} required specs parse")
+        return 0
+    print(f"\nFAIL: {len(bad)} required spec(s) do not parse\n")
+    for rel, msg in bad:
+        print(f"  {rel}")
+        print(f"      {msg}")
+    print("\n  This is the compiler's own message. It names the file, the function")
+    print("  and the line -- read it before looking at any backend.")
+    return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())