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+# RESUME POINT — HashBackend (HashMap<u32, Vec<u8>>) work, 2026-08-20
+
+## WHAT WAS DONE THIS SESSION
+1. Scrapbed `cube-store-raw/` and `cube-fuse-proxy/` — wrong-architecture duplicates that broke the build (103 errors). They referenced a non-existent backend plan.
+2. Cleaned `Cargo.toml` — removed the two stale members.
+3. Added 7 `HashBackend` (HashMap) trait-level tests to `cubestore/src/lib.rs`:
+   - put/get/delete roundtrip
+   - overwrite replaces value
+   - keys() returns sorted order
+   - scan_prefix filters C/Z/Y correctly
+   - empty backend edge case
+   - null coord (0,0,0,0) is a valid distinct key
+   - multiple backends are independent
+4. Cleaned up `_assert_backend_assoc` workaround + dead `HashMap` import in `record_codec` — no longer needed now that HashBackend has real tests.
+5. Workspace green: 15/15 cubestore tests pass, cargo check clean.
+
+## CURRENT STATE
+- Branch: feat/os-kernel-in-cube (HEAD b97efa2)
+- cubestore has 15 tests: 8 original + 7 new HashMap/HashBackend tests
+- No duplicate crates in workspace
+
+## NEXT STEPS (pick one)
+1. **Wire HashBackend into cubefs-mount** as the default in-memory backend (already wired via `--seed`; verify it mounts and serves reads/writes without a daemon)
+2. **Benchmark HashBackend** vs FileBackedStore — put/get latency to establish the in-memory baseline
+3. **Continue reading the spec** from CUBELinux.txt (offset ~360+) — the store trait and in-memory backend section, then implement the next piece
+4. **Add a small CLI smoke test** that exercises HashBackend directly (put/get/delete) without going through CubeStore