diff --git a/JSON_RPC_API.md b/JSON_RPC_API.md
index 1d94b70..4b63871 100644
--- a/JSON_RPC_API.md
+++ b/JSON_RPC_API.md
@@ -959,6 +959,10 @@ are not serialized. Live external input after restore changes subsequent play.
 Bundles have a 1 GiB total uncompressed data limit and a 4 MiB JSON limit.
 Malformed bundles/hashes are rejected before live installation. Disk I/O failure
 can leave a partial new output directory; the live machine stays unchanged.
+Archive/reference host-file open, metadata or read failures return -32603.
+Invalid checksums, dependency lengths and request guards remain -32602.
+This documents import host reads; other backends' export/output I/O errors need
+their own explicit contract and are not covered by this compatibility scope.
 Host ACLs, permissions, timestamps and external applications are not captured.
 
 Archive publication uses an atomic hard link from a completed temporary file;
diff --git a/docs/HANDOFF.md b/docs/HANDOFF.md
index cf6766f..30d2893 100644
--- a/docs/HANDOFF.md
+++ b/docs/HANDOFF.md
@@ -1,3 +1,10 @@
+# Handoff - snapshot host-read contract, 2026-10-06
+
+FINISHED documentation: import archive/reference host I/O reads return -32603;
+checksum/length/request refusals remain -32602. Runtime is unchanged; 14 focused
+API/snapshot tests and 13 subtests pass. Require final-head public CI before
+integration. Cross-backend export/output I/O normalization remains OPEN.
+
 # Handoff - device operation epochs, 2026-10-06
 
 FINISHED local: successful serial.write batches and io.read bus operations advance
@@ -12,7 +19,8 @@ control accept the old revision; exact restored source passes. Invalid parameter
 full queue and loopback refusals preserve complete Machine/control state.
 Initial scoped review found no runtime defect; its running-loop proof and central
 revision-summary gaps are fixed with an actual JSON-lines/CPU-loop UART test.
-WIP: targeted final review and final-head public CI/integration.
+PR77 rebase-integrated at b7e69ff after final-head public CI and no-defect
+targeted review.
 Parent source pin remains fixed until the combined repair/compiler witness.
 
 Earlier handoff notes below describe their historical slices.