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Record mmap bulk copy discoveries

ober

a00ba7377703ede19f3df6957fd5d1bdc629f568

diff --git a/data/anti-patterns.sexp b/data/anti-patterns.sexp
index 176e28b..9bcf826 100644
--- a/data/anti-patterns.sexp
+++ b/data/anti-patterns.sexp
@@ -4380,4 +4380,23 @@
    ("title"
      .
      "Do Not Trust Capacity Results While Stale Workers Run")
-   ("tools" "ps" "pgrep" "time" "benchmark")))
+   ("tools" "ps" "pgrep" "time" "benchmark"))
+ (("advice"
+    .
+    "Validate the range once, copy bounded chunks with a native bulk primitive, hash them with (std crypto native), and regression-check the persisted format against the pure digest implementation.")
+   ("avoid"
+     .
+     "Do not copy or hash an entire large mapping with one mmap-u8-ref call per byte; FFI and bounds-check overhead can dominate startup by orders of magnitude.")
+   ("id" . "scalar-mmap-access-for-whole-file-digest")
+   ("kinds" "module")
+   ("pattern" . "mmap-u8-ref.*(sha|digest|checksum)")
+   ("severity" . "medium")
+   ("tags" "mmap" "checksum" "sha256" "performance" "native")
+   ("title"
+     .
+     "Do Not Hash Large Mappings Through Scalar Accessors")
+   ("tools"
+     "jerboa_howto"
+     "jerboa_verify"
+     "benchmark"
+     "jerboa_security_scan")))
diff --git a/data/features.sexp b/data/features.sexp
index 35545be..302830c 100644
--- a/data/features.sexp
+++ b/data/features.sexp
@@ -3640,4 +3640,21 @@
    ("use_case"
      .
      "Long capacity and soak benchmarks that may survive an interrupted agent session and contaminate later measurements.")
+   ("votes" . 0))
+ (("description"
+    .
+    "Provide mmap-copy-out! and a bounded mmap-range->bytevector implemented with one native memcpy after range validation. The current mmap->bytevector and custom input-port callbacks copy through per-byte foreign-ref loops.")
+   ("estimated_token_reduction"
+     .
+     "~300 tokens and one local FFI helper per mmap consumer")
+   ("example_scenario"
+     .
+     "A 258 MB QIX checksum took tens of seconds through scalar mmap-u8-ref calls; bounded native copies into Jerboa's existing native SHA reduced full validation to 140 ms.")
+   ("id" . "std-mmap-bulk-copy-out") ("impact" . "high")
+   ("status" . "proposed")
+   ("tags" "mmap" "memcpy" "bytevector" "performance")
+   ("title" . "Add native bulk copy-out to std mmap")
+   ("use_case"
+     .
+     "Checksums, parsers, and codecs that consume bounded chunks from large mappings through existing bytevector APIs.")
    ("votes" . 0)))