diff --git a/FUSE-Mount.md b/FUSE-Mount.md
index 7ec0553..7cfb49f 100644
--- a/FUSE-Mount.md
+++ b/FUSE-Mount.md
@@ -16,6 +16,102 @@ With "weed mount", the files can be operated as a local file. The following oper
 * advisory file locking (`flock(2)` and POSIX `fcntl(2)` byte-range locks)
 * extended attributes (xattr)
 
+### Distributed Lock (cross-mount write coordination)
+
+`weed mount` can coordinate writers across different mount instances using
+the filer's distributed lock manager (DLM). When enabled, opening a file
+for writing acquires a cluster-wide lock on the file's filer path, so only
+one mount can write a given file at a time. Other mounts that open the same
+file for writing block until the holder releases it.
+
+#### Enabling
+
+Pass `-dlm` when starting `weed mount`:
+
+```bash
+weed mount -filer=localhost:8888 -dir=/mnt/seaweedfs -dlm
+```
+
+DLM is off by default. It is automatically disabled if `-writebackCache` is
+also set, since writeback implies single-writer semantics and the extra
+coordination would only add latency. When DLM is disabled, writers across
+mounts are unordered — last writer wins on flush.
+
+#### Flow
+
+```mermaid
+sequenceDiagram
+    participant A as App on Mount A
+    participant MA as weed mount A<br/>(owner mount-1)
+    participant F as Filer DLM
+    participant MB as weed mount B<br/>(owner mount-2)
+    participant B as App on Mount B
+
+    A->>MA: open("/data/file", O_WRONLY)
+    MA->>F: Lock("/data/file", owner=mount-1, ttl=7s)
+    F-->>MA: granted
+    Note over MA,F: Heartbeat renews lock every ~7s
+    MA-->>A: fd
+
+    B->>MB: open("/data/file", O_WRONLY)
+    MB->>F: Lock("/data/file", owner=mount-2, ttl=7s)
+    F-->>MB: blocked (held by mount-1)
+
+    A->>MA: write / close
+    MA->>F: flush to filer, then Unlock
+    F-->>MB: granted (mount-1 released)
+    MB-->>B: fd
+    B->>MB: write / close
+    MB->>F: flush to filer, then Unlock
+```
+
+If mount A crashes without closing, the filer drops the lock after the
+7-second TTL and mount B's pending acquire unblocks automatically.
+
+#### Semantics
+
+* **Scope.** The lock key is the file's filer path (not the local inode,
+  which is per-mount). Two mounts opening the same path for writing contend
+  on the same key.
+* **Acquisition.** The lock is taken when a handle is opened with any write
+  flag (`O_WRONLY`, `O_RDWR`, `O_APPEND`, `O_CREAT`, `O_TRUNC`). Read-only
+  opens are not locked. Acquisition is blocking: a second mount's
+  `open(2)`-for-write blocks until the first mount closes the file or the
+  lock TTL expires.
+* **Release.** The lock is held for the full lifetime of the file handle
+  and released on close. For handles running the writeback async flush
+  path, the lock is released after the background flush completes — so a
+  reader on another mount after a successful close always sees the flushed
+  data.
+* **Auto-renewal.** The lock is renewed on a 7-second TTL heartbeat while
+  the handle is open. If a mount crashes, the lock frees on TTL expiry.
+* **Rename and unlink.** `rename(2)` acquires DLM locks on both the source
+  and destination paths (sorted to avoid A→B / B→A deadlocks) so no other
+  mount can open either path for writing during the rename. `unlink(2)` of
+  a file that is currently open on this mount coordinates with the held
+  handle's lock.
+* **Owner identifier.** Each mount is tagged with `mount-<signature>`,
+  which appears in filer lock logs and in `weed shell`'s lock commands for
+  debugging.
+
+#### Requirements and constraints
+
+* At least one filer address (`-filer=`) must be configured; DLM is a
+  filer-hosted service.
+* DLM is disabled when `-writebackCache` is set (single-writer mode).
+* DLM coordinates writes only. Concurrent readers on different mounts are
+  never blocked, and they still see flushed data via the filer's metadata.
+* DLM does not replace POSIX `fcntl`/`flock` advisory locks; those remain
+  available and are orthogonal (see the next section).
+
+#### When to use it
+
+Enable `-dlm` when multiple `weed mount` instances may write to the same
+files — e.g. a shared build cache mounted on several CI workers, or an
+application that runs on multiple nodes and writes to the same path. Leave
+it off for single-mount deployments or when each mount writes into its own
+subtree, since the extra round-trips add latency on every open-for-write.
+
 ### Advisory File Locking
 
 SeaweedFS supports advisory file locking over FUSE:
diff --git a/POSIX-Compliance.md b/POSIX-Compliance.md
new file mode 100644
index 0000000..c6d1b4a
--- /dev/null
+++ b/POSIX-Compliance.md
@@ -0,0 +1,76 @@
+# POSIX Compliance for `weed mount`
+
+SeaweedFS runs the [pjdfstest](https://github.com/pjd/pjdfstest) POSIX
+compliance suite against `weed mount` on every change to `weed/mount/**`,
+`weed/filer/**`, or the test harness itself. The job is defined in
+[`.github/workflows/pjdfstest.yml`](https://github.com/seaweedfs/seaweedfs/blob/master/.github/workflows/pjdfstest.yml)
+and the harness lives under [`test/pjdfstest/`](https://github.com/seaweedfs/seaweedfs/tree/master/test/pjdfstest).
+
+## How it runs
+
+1. A SeaweedFS e2e image (master + volume + filer + mount) is built and
+   started via `test/pjdfstest/docker-compose.yml`.
+2. `test/pjdfstest/run.sh` mounts the filesystem with `weed mount
+   -allowOthers=true` and clones pjdfstest pinned to an immutable upstream
+   commit for reproducibility.
+3. `prove -rv` runs every `tests/**/*.t` except the entries listed in
+   [`known_failures.txt`](https://github.com/seaweedfs/seaweedfs/blob/master/test/pjdfstest/known_failures.txt).
+   Any failure outside that allow-list fails CI.
+
+## Tests passing
+
+All pjdfstest syscall groups pass on `weed mount`, except for the three
+test files called out below. The groups exercised by the suite are:
+
+| Group | Coverage |
+|-------|----------|
+| `tests/chflags/` | BSD file flags (skipped on Linux by the suite itself) |
+| `tests/chmod/` | `chmod(2)` permission, errno, and setuid/setgid behavior |
+| `tests/chown/` | `chown(2)` ownership, errno, and clearing of set\*id bits |
+| `tests/link/` | `link(2)` creation, permission, and errno cases (except `00.t`) |
+| `tests/mkdir/` | `mkdir(2)` creation and errno paths |
+| `tests/mkfifo/` | `mkfifo(2)` FIFO creation |
+| `tests/mknod/` | `mknod(2)` regular/FIFO node creation |
+| `tests/open/` | `open(2)` flags, permissions, `O_CREAT`, `O_TRUNC`, errno |
+| `tests/rename/` | `rename(2)` same/cross-directory, errno cases (except `21.t`) |
+| `tests/rmdir/` | `rmdir(2)` empty-directory and errno cases |
+| `tests/symlink/` | `symlink(2)` creation, traversal, errno cases |
+| `tests/truncate/` | `truncate(2)` resize, permission, and errno cases |
+| `tests/unlink/` | `unlink(2)` removal and errno cases (except `00.t`) |
+| `tests/utimensat/` | `utimensat(2)` atime/mtime/ctime semantics, errno paths |
+| `tests/granular/` | Granular timestamp update checks |
+
+## Tests not passing
+
+The following tests are listed in
+[`test/pjdfstest/known_failures.txt`](https://github.com/seaweedfs/seaweedfs/blob/master/test/pjdfstest/known_failures.txt)
+and are skipped in CI. They are deterministic and tracked as known issues:
+
+| Test | Category | Reason |
+|------|----------|--------|
+| `tests/rename/21.t` | rename | Cross-directory rename of a subdirectory with restricted permissions triggers cascading failures in the rest of the test file. |
+| `tests/link/00.t` | link | `nlink` assertion mismatch (e.g. expected `nlink=2`, got `nlink=3`) after hard link creation. Filer-side hard-link counter issue. |
+| `tests/unlink/00.t` | unlink | Same filer-side hard-link counter issue surfaced on the removal path. |
+
+The two `nlink` failures are filer-side hard-link counter bugs rather than
+FUSE mount bugs, and are deterministic under the current meta-cache load
+ordering. The rename failure is a permission edge case on cross-directory
+rename. Contributions that fix any of these are welcome — once a test is
+green, remove it from `known_failures.txt` so CI enforces it going forward.
+
+## Running locally
+
+```sh
+# Full suite against a local weed binary (requires sudo, fusermount3,
+# autoconf, make, perl TAP::Harness::Archive).
+test/pjdfstest/run.sh
+
+# Subset, e.g. only chmod tests
+PJDFSTEST_TESTS=tests/chmod test/pjdfstest/run.sh
+
+# Containerized (matches CI exactly)
+docker compose -f test/pjdfstest/docker-compose.yml up --wait
+docker compose -f test/pjdfstest/docker-compose.yml exec mount /run.sh
+```
+
+See also: [FUSE Mount](FUSE-Mount).
diff --git a/_Sidebar.md b/_Sidebar.md
index c49bc63..c859c40 100644
--- a/_Sidebar.md
+++ b/_Sidebar.md
@@ -58,6 +58,7 @@
 ### [[FUSE Mount]]
 * [[FIO benchmark]]
 * [[fstab and systemd mount]]
+* [[POSIX Compliance]]
 
 ### [[WebDAV]]