diff --git a/lang/el-compiler/runtime/el_runtime.c b/lang/el-compiler/runtime/el_runtime.c
index 2b75c6f..af0d945 100644
--- a/lang/el-compiler/runtime/el_runtime.c
+++ b/lang/el-compiler/runtime/el_runtime.c
@@ -82,8 +82,14 @@ static _Thread_local ElArena _tl_arena = {NULL, 0, 0};
 static _Thread_local int     _tl_arena_active = 0;
 
 /* Binary-safe fs_read length — set by fs_read, consumed by http_send_response.
- * Allows serving PNGs and other binary files without strlen truncation. */
-static _Thread_local size_t  _tl_fs_read_len  = 0;
+ * Allows serving PNGs and other binary files without strlen truncation.
+ * PAIRED with the buffer pointer it describes: the length may only be applied
+ * to the exact buffer fs_read returned. Without the pairing, any handler that
+ * fs_read a file and then WRAPPED it into a larger response had that response
+ * truncated to the file's length (Content-Length lied AND the send stopped
+ * short) — the safety-contact onboarding trap, 2026-07-17. */
+static _Thread_local size_t      _tl_fs_read_len  = 0;
+static _Thread_local const char* _tl_fs_read_buf  = NULL;
 
 static void el_arena_track(char* p) {
     if (!_tl_arena_active || !p) return;
@@ -101,6 +107,8 @@ static void el_arena_track(char* p) {
 void el_request_start(void) {
     _tl_arena.count  = 0;
     _tl_arena_active = 1;
+    _tl_fs_read_len  = 0;     /* never let a previous request's file length */
+    _tl_fs_read_buf  = NULL;  /* leak into this response's byte accounting  */
 }
 
 /* Called by http_worker after the El handler returns and the response is sent.
@@ -1484,11 +1492,14 @@ static void http_send_response(int fd, const char* body) {
     }
 
     const char* eff_body = is_envelope ? env_body : body;
-    /* Use the real byte count from fs_read if available (handles binary files
-     * with embedded null bytes — PNG, WOFF2, etc.). Fall back to strlen for
-     * normal text/JSON responses where _tl_fs_read_len is 0. */
-    size_t blen = (_tl_fs_read_len > 0) ? _tl_fs_read_len : strlen(eff_body);
+    /* Use the real byte count from fs_read ONLY when this body IS the exact
+     * buffer fs_read returned (binary files with embedded null bytes — PNG,
+     * WOFF2, etc.). Any other body — wrapped, enveloped, or derived — must be
+     * measured with strlen, or it is truncated/over-read to the file's size. */
+    size_t blen = (_tl_fs_read_len > 0 && eff_body == _tl_fs_read_buf)
+                      ? _tl_fs_read_len : strlen(eff_body);
     _tl_fs_read_len = 0;  /* consume — one-shot per response */
+    _tl_fs_read_buf = NULL;
     int head_only = _tl_http_head_only;
 
     JsonBuf hdrs; jb_init(&hdrs);
@@ -1568,11 +1579,22 @@ static void* http_worker(void* arg) {
             const char* rs = EL_CSTR(r);
             /* Copy response out BEFORE arena teardown.
              * For binary files, _tl_fs_read_len holds the real byte count —
-             * use memcpy instead of strdup so null bytes are preserved. */
-            size_t rlen = _tl_fs_read_len > 0 ? _tl_fs_read_len : (rs ? strlen(rs) : 0);
+             * use memcpy instead of strdup so null bytes are preserved.
+             * The stored length applies ONLY when the response IS the exact
+             * fs_read buffer; a wrapped/derived response must use strlen or
+             * it gets truncated (or over-read) to the file's length. */
+            size_t rlen;
+            if (_tl_fs_read_len > 0 && rs && rs == _tl_fs_read_buf) {
+                rlen = _tl_fs_read_len;   /* raw file bytes — binary-safe */
+            } else {
+                rlen = rs ? strlen(rs) : 0;
+                _tl_fs_read_len = 0;      /* hint doesn't describe this body */
+                _tl_fs_read_buf = NULL;
+            }
             response = malloc(rlen + 1);
             if (response && rs) { memcpy(response, rs, rlen); response[rlen] = '\0'; }
             else if (response) { response[0] = '\0'; }
+            if (_tl_fs_read_len > 0) _tl_fs_read_buf = response; /* hint follows the copy */
         } else {
             response = el_strdup_persist("el-runtime: no http handler registered");
         }
@@ -1822,10 +1844,20 @@ static void* http_worker_v2(void* arg) {
             el_val_t hmap = http_build_headers_map(hdr_block ? hdr_block : "");
             el_val_t r = h(EL_STR(dispatch_method), EL_STR(path), hmap, EL_STR(body));
             const char* rs = EL_CSTR(r);
-            size_t rlen = _tl_fs_read_len > 0 ? _tl_fs_read_len : (rs ? strlen(rs) : 0);
+            /* Same pairing rule as the v1 worker: the fs_read length is only
+             * trustworthy for the exact buffer fs_read returned. */
+            size_t rlen;
+            if (_tl_fs_read_len > 0 && rs && rs == _tl_fs_read_buf) {
+                rlen = _tl_fs_read_len;   /* raw file bytes — binary-safe */
+            } else {
+                rlen = rs ? strlen(rs) : 0;
+                _tl_fs_read_len = 0;      /* hint doesn't describe this body */
+                _tl_fs_read_buf = NULL;
+            }
             response = malloc(rlen + 1);
             if (response && rs) { memcpy(response, rs, rlen); response[rlen] = '\0'; }
             else if (response) { response[0] = '\0'; }
+            if (_tl_fs_read_len > 0) _tl_fs_read_buf = response; /* hint follows the copy */
             el_release(hmap);
         } else {
             response = el_strdup_persist(
@@ -2024,6 +2056,7 @@ el_val_t http_response(el_val_t status, el_val_t headers_json, el_val_t body) {
 el_val_t fs_read(el_val_t pathv) {
     const char* path = EL_CSTR(pathv);
     _tl_fs_read_len = 0;
+    _tl_fs_read_buf = NULL;
     if (!path) return el_wrap_str(el_strdup(""));
     FILE* f = fopen(path, "rb");
     if (!f) return el_wrap_str(el_strdup(""));
@@ -2035,6 +2068,7 @@ el_val_t fs_read(el_val_t pathv) {
     size_t got = fread(buf, 1, (size_t)sz, f);
     buf[got] = '\0';
     _tl_fs_read_len = got;   /* store real byte count for binary-safe send */
+    _tl_fs_read_buf = buf;   /* ...valid ONLY for this exact buffer */
     fclose(f);
     return el_wrap_str(buf);
 }
@@ -3577,8 +3611,10 @@ el_val_t json_get_raw(el_val_t json_str, el_val_t key) {
     const char* k    = EL_CSTR(key);
     const char* p = json_find_key(json, k);
     /* Clear fs_read binary-length hint — result is a fresh null-terminated
-     * string, not the raw file bytes, so Content-Length must use strlen. */
+     * string, not the raw file bytes, so Content-Length must use strlen.
+     * (Kept although the pointer pairing now makes this redundant.) */
     _tl_fs_read_len = 0;
+    _tl_fs_read_buf = NULL;
     if (!p) return el_wrap_str(el_strdup(""));
     const char* end = json_skip_value(p);
     size_t n = (size_t)(end - p);
diff --git a/lang/releases/v1.0.0-20260501/el_runtime.c b/lang/releases/v1.0.0-20260501/el_runtime.c
index e9d633c..d05edfe 100644
--- a/lang/releases/v1.0.0-20260501/el_runtime.c
+++ b/lang/releases/v1.0.0-20260501/el_runtime.c
@@ -71,8 +71,14 @@ static _Thread_local ElArena _tl_arena = {NULL, 0, 0};
 static _Thread_local int     _tl_arena_active = 0;
 
 /* Binary-safe fs_read length — set by fs_read, consumed by http_send_response.
- * Allows serving PNGs and other binary files without strlen truncation. */
-static _Thread_local size_t  _tl_fs_read_len  = 0;
+ * Allows serving PNGs and other binary files without strlen truncation.
+ * PAIRED with the buffer pointer it describes: the length may only be applied
+ * to the exact buffer fs_read returned. Without the pairing, any handler that
+ * fs_read a file and then WRAPPED it into a larger response had that response
+ * truncated to the file's length (Content-Length lied AND the send stopped
+ * short) — the safety-contact onboarding trap, 2026-07-17. */
+static _Thread_local size_t      _tl_fs_read_len  = 0;
+static _Thread_local const char* _tl_fs_read_buf  = NULL;
 
 static void el_arena_track(char* p) {
     if (!_tl_arena_active || !p) return;
@@ -90,6 +96,8 @@ static void el_arena_track(char* p) {
 void el_request_start(void) {
     _tl_arena.count  = 0;
     _tl_arena_active = 1;
+    _tl_fs_read_len  = 0;     /* never let a previous request's file length */
+    _tl_fs_read_buf  = NULL;  /* leak into this response's byte accounting  */
 }
 
 /* Called by http_worker after the El handler returns and the response is sent.
@@ -1403,11 +1411,14 @@ static void http_send_response(int fd, const char* body) {
     }
 
     const char* eff_body = is_envelope ? env_body : body;
-    /* Use the real byte count from fs_read if available (handles binary files
-     * with embedded null bytes — PNG, WOFF2, etc.). Fall back to strlen for
-     * normal text/JSON responses where _tl_fs_read_len is 0. */
-    size_t blen = (_tl_fs_read_len > 0) ? _tl_fs_read_len : strlen(eff_body);
+    /* Use the real byte count from fs_read ONLY when this body IS the exact
+     * buffer fs_read returned (binary files with embedded null bytes — PNG,
+     * WOFF2, etc.). Any other body — wrapped, enveloped, or derived — must be
+     * measured with strlen, or it is truncated/over-read to the file's size. */
+    size_t blen = (_tl_fs_read_len > 0 && eff_body == _tl_fs_read_buf)
+                      ? _tl_fs_read_len : strlen(eff_body);
     _tl_fs_read_len = 0;  /* consume — one-shot per response */
+    _tl_fs_read_buf = NULL;
     int head_only = _tl_http_head_only;
 
     JsonBuf hdrs; jb_init(&hdrs);
@@ -1479,11 +1490,22 @@ static void* http_worker(void* arg) {
             const char* rs = EL_CSTR(r);
             /* Copy response out BEFORE arena teardown.
              * For binary files, _tl_fs_read_len holds the real byte count —
-             * use memcpy instead of strdup so null bytes are preserved. */
-            size_t rlen = _tl_fs_read_len > 0 ? _tl_fs_read_len : (rs ? strlen(rs) : 0);
+             * use memcpy instead of strdup so null bytes are preserved.
+             * The stored length applies ONLY when the response IS the exact
+             * fs_read buffer; a wrapped/derived response must use strlen or
+             * it gets truncated (or over-read) to the file's length. */
+            size_t rlen;
+            if (_tl_fs_read_len > 0 && rs && rs == _tl_fs_read_buf) {
+                rlen = _tl_fs_read_len;   /* raw file bytes — binary-safe */
+            } else {
+                rlen = rs ? strlen(rs) : 0;
+                _tl_fs_read_len = 0;      /* hint doesn't describe this body */
+                _tl_fs_read_buf = NULL;
+            }
             response = malloc(rlen + 1);
             if (response && rs) { memcpy(response, rs, rlen); response[rlen] = '\0'; }
             else if (response) { response[0] = '\0'; }
+            if (_tl_fs_read_len > 0) _tl_fs_read_buf = response; /* hint follows the copy */
         } else {
             response = el_strdup_persist("el-runtime: no http handler registered");
         }
@@ -1805,10 +1827,20 @@ static void* http_worker_v2(void* arg) {
             el_val_t hmap = http_build_headers_map(hdr_block ? hdr_block : "");
             el_val_t r = h(EL_STR(dispatch_method), EL_STR(path), hmap, EL_STR(body));
             const char* rs = EL_CSTR(r);
-            size_t rlen = _tl_fs_read_len > 0 ? _tl_fs_read_len : (rs ? strlen(rs) : 0);
+            /* Same pairing rule as the v1 worker: the fs_read length is only
+             * trustworthy for the exact buffer fs_read returned. */
+            size_t rlen;
+            if (_tl_fs_read_len > 0 && rs && rs == _tl_fs_read_buf) {
+                rlen = _tl_fs_read_len;   /* raw file bytes — binary-safe */
+            } else {
+                rlen = rs ? strlen(rs) : 0;
+                _tl_fs_read_len = 0;      /* hint doesn't describe this body */
+                _tl_fs_read_buf = NULL;
+            }
             response = malloc(rlen + 1);
             if (response && rs) { memcpy(response, rs, rlen); response[rlen] = '\0'; }
             else if (response) { response[0] = '\0'; }
+            if (_tl_fs_read_len > 0) _tl_fs_read_buf = response; /* hint follows the copy */
             el_release(hmap);
         } else {
             response = el_strdup_persist(
@@ -1924,6 +1956,7 @@ el_val_t http_response(el_val_t status, el_val_t headers_json, el_val_t body) {
 el_val_t fs_read(el_val_t pathv) {
     const char* path = EL_CSTR(pathv);
     _tl_fs_read_len = 0;
+    _tl_fs_read_buf = NULL;
     if (!path) return el_wrap_str(el_strdup(""));
     FILE* f = fopen(path, "rb");
     if (!f) return el_wrap_str(el_strdup(""));
@@ -1935,6 +1968,7 @@ el_val_t fs_read(el_val_t pathv) {
     size_t got = fread(buf, 1, (size_t)sz, f);
     buf[got] = '\0';
     _tl_fs_read_len = got;   /* store real byte count for binary-safe send */
+    _tl_fs_read_buf = buf;   /* ...valid ONLY for this exact buffer */
     fclose(f);
     return el_wrap_str(buf);
 }
@@ -3305,8 +3339,10 @@ el_val_t json_get_raw(el_val_t json_str, el_val_t key) {
     const char* k    = EL_CSTR(key);
     const char* p = json_find_key(json, k);
     /* Clear fs_read binary-length hint — result is a fresh null-terminated
-     * string, not the raw file bytes, so Content-Length must use strlen. */
+     * string, not the raw file bytes, so Content-Length must use strlen.
+     * (Kept although the pointer pairing now makes this redundant.) */
     _tl_fs_read_len = 0;
+    _tl_fs_read_buf = NULL;
     if (!p) return el_wrap_str(el_strdup(""));
     const char* end = json_skip_value(p);
     size_t n = (size_t)(end - p);