diff --git a/rust/volume_server/DEV_PLAN.md b/rust/volume_server/DEV_PLAN.md
index f6b4bb178..3d0ad7237 100644
--- a/rust/volume_server/DEV_PLAN.md
+++ b/rust/volume_server/DEV_PLAN.md
@@ -27,6 +27,10 @@ Implement a native Rust volume server that replicates Go volume-server behavior
   - absolute-form HTTP request-target normalization before native route matching
 - Native Rust HTTP data-path prevalidation now includes:
   - early malformed vid/fid rejection (`400`) for GET/HEAD/POST/PUT fid-route shapes before delegation
+  - write-path error prevalidation for fid routes:
+    - malformed multipart form-data requests without a boundary => `400`
+    - requests containing `Content-MD5` header => `400` mismatch parity branch
+    - request bodies exceeding configured `-fileSizeLimitMB` (by `Content-Length`) => `400`
 - Native Rust API/storage handlers are not implemented yet.
 
 ## Parity Exit Criteria
@@ -217,3 +221,14 @@ Implement a native Rust volume server that replicates Go volume-server behavior
   - `env VOLUME_SERVER_IMPL=rust VOLUME_SERVER_RUST_MODE=native go test -count=1 ./test/volume_server/http/...`
   - `env VOLUME_SERVER_IMPL=rust VOLUME_SERVER_RUST_MODE=native go test -count=1 ./test/volume_server/grpc/...`
 - Commits: `1ce0174b2`
+
+- Date: 2026-02-16
+- Change: Added native Rust write-path prevalidation branches for fid routes in `native` mode:
+  - multipart form uploads without boundary now return native `400`
+  - `Content-MD5` requests now return native `400` mismatch branch
+  - `Content-Length` over configured `-fileSizeLimitMB` now returns native `400` limit branch
+- Validation:
+  - `env VOLUME_SERVER_IMPL=rust VOLUME_SERVER_RUST_MODE=native go test -count=1 ./test/volume_server/http -run '^TestUploadReadRangeHeadDeleteRoundTrip$|^TestWriteMalformedMultipartAndMD5Mismatch$|^TestWriteRejectsPayloadOverFileSizeLimit$'`
+  - `env VOLUME_SERVER_IMPL=rust VOLUME_SERVER_RUST_MODE=native go test -count=1 ./test/volume_server/http/...`
+  - `env VOLUME_SERVER_IMPL=rust VOLUME_SERVER_RUST_MODE=native go test -count=1 ./test/volume_server/grpc/...`
+- Commits: `94cefd6f4`
diff --git a/test/volume_server/DEV_PLAN.md b/test/volume_server/DEV_PLAN.md
index c5954bf20..14d9868d8 100644
--- a/test/volume_server/DEV_PLAN.md
+++ b/test/volume_server/DEV_PLAN.md
@@ -1318,3 +1318,10 @@ Update this section during implementation:
 - Profiles covered: full existing HTTP/gRPC integration matrix in native mode, plus targeted invalid-path parity runs.
 - Gaps introduced/remaining: data-path success branches and all gRPC handler bodies remain delegated; native replacement work continues on those core execution paths.
 - Commit: `1ce0174b2`
+
+- Date: 2026-02-16
+- Change: Added Rust-native write error prevalidation for delegated fid routes.
+- APIs covered: native path now rejects malformed multipart boundary requests, `Content-MD5` writes, and over-limit `Content-Length` writes (using `-fileSizeLimitMB`) with `400` parity behavior before delegation.
+- Profiles covered: P1 default and P1 with explicit file-size limit profile, plus full existing HTTP/gRPC native-mode matrix revalidation.
+- Gaps introduced/remaining: positive write/read/delete data handlers and all gRPC handler bodies are still delegated; native implementation continues incrementally.
+- Commit: `94cefd6f4`