045: Pure's answers checked for real (cost.c and where.c compared only the C's with the test before; now Pure's boundaries are read from its view, and a wrong variant is refused with 0 lines right); the executor and the stitched build, rebuilt at adccf58, both answer all 18,672 lines, and the stitched build's numbers stand (40,189 to 28,089 machine instructions a point, 1.43x; cycles 1.32x); 029 says so

3 files changed, 33 insertions, 23 deletions

diff --git a/research/experiments/045-proof-compiler/2026-10-19-break.jsonl b/research/experiments/045-proof-compiler/2026-10-19-break.jsonl
index f70a825..7710f47 100644
--- a/research/experiments/045-proof-compiler/2026-10-19-break.jsonl
+++ b/research/experiments/045-proof-compiler/2026-10-19-break.jsonl
@@ -11,3 +11,4 @@
 {"what": "variant v0r: the empty handler and range(p.code) a point (events.c, PURE_JIT=0)", "empty_handler": 1562.6, "range_only": 16051.7, "lists_built": 24211.2, "range_per_point": 14489.1, "range_iterations_per_point": 11.4}
 {"what": "mechanisms, the app (where.c and where.py: 246,581 samples every 100,003 user instructions, 10 rounds, answers checked)", "machine_instructions_per_point": 40236, "dispatch": 12298, "list_build": 6953, "compute": 5416, "list_read": 5238, "moves": 3601, "call": 2847, "memory": 1609, "unplaced": 1213, "event": 947, "loop": 113}
 {"what": "mechanisms, variant v0r (range only)", "machine_instructions_per_point": 16089, "dispatch": 6038, "compute": 3697, "list_read": 2729, "moves": 1521, "unplaced": 713, "list_build": 451, "call": 360, "memory": 247, "event": 190, "loop": 144, "floor_divide_and_fmod": 2121}
+{"what": "(b) checked again: cost.c now reads Pure's boundaries from its view (it compared only the C's before); the stitched build rebuilt from stitch.c and native-hook.patch at adccf58; both answer all 18,672 lines", "interpreted": {"instructions_per_point": 40189.2, "cycles_per_point": [15398.8, 15433.1]}, "stitched": {"instructions_per_point": 28088.7, "cycles_per_point": [11692.5, 11715.0]}, "instruction_factor": 1.43, "cycle_factor": 1.32, "pure_right": 18672, "lines": 18672}
diff --git a/research/experiments/045-proof-compiler/cost.c b/research/experiments/045-proof-compiler/cost.c
index 2b300a4..15940d6 100644
--- a/research/experiments/045-proof-compiler/cost.c
+++ b/research/experiments/045-proof-compiler/cost.c
@@ -13,23 +13,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
 #include <linux/perf_event.h>
 #include <sys/ioctl.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 
-static double now_ns(void) {
-    struct timespec t;
-    clock_gettime(CLOCK_MONOTONIC, &t);
-    return (double)t.tv_sec * 1e9 + (double)t.tv_nsec;
-}
-
-static int by_value(const void *a, const void *b) {
-    double x = *(const double *)a, y = *(const double *)b;
-    return (x > y) - (x < y);
-}
-
 static unsigned char *whole(const char *path, size_t *size) {
     FILE *f = fopen(path, "rb");
     if (!f) return NULL;
@@ -44,7 +32,7 @@ static unsigned char *whole(const char *path, size_t *size) {
 
 typedef struct { uint32_t count; const uint32_t *codes; const unsigned char *want; unsigned char *payload; } Line;
 
-/* A line's boundaries from Pure: the bytes state "breaks", compared as breaks or not with want. */
+/* A line's boundaries from Pure: the bytes view "boundaries", compared as breaks or not with want. */
 typedef struct { const unsigned char *want; size_t at; bool same; } Compare;
 static bool compare(void *context, PureSpan span) {
     Compare *c = context;
@@ -95,14 +83,19 @@ int main(int argc, char **argv) {
     int load = pure_module_input(&module, "load"), line = pure_module_input(&module, "line");
     if (pure_app_message(&app, (uint32_t)load, (PureSpan){ranges, ranges_size}) != PURE_OK) return 1;
     static uint8_t got[4096];
-    size_t right = 0;
-    for (size_t k = 0; k < count; ++k) { /* checked first: both give the test's boundaries */
-        bool same = pure_app_message(&app, (uint32_t)line, (PureSpan){lines[k].payload, 8 * (size_t)lines[k].count}) == PURE_OK &&
-                    lines[k].count < sizeof(got) && vega_line_breaks(lines[k].codes, lines[k].count, got);
+    size_t right = 0, pure_right = 0;
+    int boundaries = pure_module_view(&module, "boundaries");
+    for (size_t k = 0; k < count; ++k) { /* checked first: both give the test's boundaries, Pure's read from its view */
+        bool same = lines[k].count < sizeof(got) && vega_line_breaks(lines[k].codes, lines[k].count, got);
         for (uint32_t i = 0; same && i <= lines[k].count; ++i) same = (got[i] != VEGA_BREAK_NONE) == lines[k].want[i];
         right += same;
+        Compare c = {lines[k].want, 0, true};
+        c.same = boundaries >= 0 &&
+                 pure_app_message(&app, (uint32_t)line, (PureSpan){lines[k].payload, 8 * (size_t)lines[k].count}) == PURE_OK &&
+                 pure_app_view_text(&app, (uint32_t)boundaries, compare, &c) == PURE_OK;
+        pure_right += c.same && c.at == lines[k].count + 1;
     }
-    if (right != count) { fprintf(stderr, "right %zu of %zu\n", right, count); return 1; }
+    if (right != count || pure_right != count) { fprintf(stderr, "right: C %zu, Pure %zu, of %zu\n", right, pure_right, count); return 1; }
     int ins = counter(PERF_COUNT_HW_INSTRUCTIONS), cyc = counter(PERF_COUNT_HW_CPU_CYCLES);
     if (ins < 0 || cyc < 0) { perror("perf_event_open"); return 1; }
     volatile unsigned sink = 0;
diff --git a/research/experiments/045-proof-compiler/where.c b/research/experiments/045-proof-compiler/where.c
index 0764443..6d3799b 100644
--- a/research/experiments/045-proof-compiler/where.c
+++ b/research/experiments/045-proof-compiler/where.c
@@ -34,6 +34,14 @@ static unsigned char *whole(const char *path, size_t *size) {
 
 typedef struct { uint32_t count; const uint32_t *codes; const unsigned char *want; unsigned char *payload; } Line;
 
+/* A line's boundaries from Pure: the bytes view "boundaries", compared as breaks or not with want. */
+typedef struct { const unsigned char *want; size_t at; bool same; } Compare;
+static bool compare(void *context, PureSpan span) {
+    Compare *c = context;
+    for (size_t i = 0; i < span.size; ++i, ++c->at) c->same = c->same && (span.data[i] != 0) == c->want[c->at];
+    return true;
+}
+
 /* Addresses sampled, counted in an open table. */
 enum { SLOTS = 1 << 20, PAGES = 64 };
 static uint64_t address[SLOTS], hits[SLOTS];
@@ -92,14 +100,22 @@ int main(int argc, char **argv) {
     int load = pure_module_input(&module, "load"), line = pure_module_input(&module, "line");
     if (pure_app_message(&app, (uint32_t)load, (PureSpan){ranges, ranges_size}) != PURE_OK) return 1;
     static uint8_t got[4096];
-    size_t right = 0;
-    for (size_t k = 0; k < count; ++k) { /* checked first: Pure gives the test's boundaries */
-        bool same = pure_app_message(&app, (uint32_t)line, (PureSpan){lines[k].payload, 8 * (size_t)lines[k].count}) == PURE_OK &&
-                    lines[k].count < sizeof(got) && vega_line_breaks(lines[k].codes, lines[k].count, got);
+    size_t right = 0, pure_right = 0;
+    int boundaries = pure_module_view(&module, "boundaries");
+    for (size_t k = 0; k < count; ++k) { /* checked first: both give the test's boundaries, Pure's read from its view */
+        bool same = lines[k].count < sizeof(got) && vega_line_breaks(lines[k].codes, lines[k].count, got);
         for (uint32_t i = 0; same && i <= lines[k].count; ++i) same = (got[i] != VEGA_BREAK_NONE) == lines[k].want[i];
         right += same;
+        Compare c = {lines[k].want, 0, true};
+        c.same = boundaries >= 0 &&
+                 pure_app_message(&app, (uint32_t)line, (PureSpan){lines[k].payload, 8 * (size_t)lines[k].count}) == PURE_OK &&
+                 pure_app_view_text(&app, (uint32_t)boundaries, compare, &c) == PURE_OK;
+        pure_right += c.same && c.at == lines[k].count + 1;
+    }
+    if ((right != count || pure_right != count) && !getenv("WHERE_VARIANT")) {
+        fprintf(stderr, "right: C %zu, Pure %zu, of %zu\n", right, pure_right, count);
+        return 1;
     }
-    if (right != count && !getenv("WHERE_VARIANT")) { fprintf(stderr, "right %zu of %zu\n", right, count); return 1; }
     struct perf_event_attr a;
     memset(&a, 0, sizeof(a));
     a.size = sizeof(a), a.type = PERF_TYPE_HARDWARE, a.config = PERF_COUNT_HW_INSTRUCTIONS, a.disabled = 1,