docs: update all docs for :last, :search, :mute-joins and MOTD

- README: add new commands to COMMAND mode table, MOTD section,
  update Known Limitations (100-msg limit now softened by :last/:search)
- tnt.1: add :last/:search/:mute-joins to man page command table,
  add motd.txt to FILES section
- CHANGELOG: add 2026-04-23 entry
- QUICKREF: rewrite command section, add new commands, add motd.txt to files
- ROADMAP: mark Stage 4 :last/:search/:mute-joins items as completed
- DEPLOYMENT: add MOTD setup section

README.md

@@ -82,6 +82,9 @@ Ctrl+C     - Exit chat
 :nick <name>         - Change nickname
 :msg <user> <text>   - Whisper to user
 :w <user> <text>     - Short alias for :msg
+:last [N]            - Show last N messages from history (max 50, default 10)
+:search <keyword>    - Search full message history (case-insensitive)
+:mute-joins          - Toggle join/leave system notifications
 :help                - Show available commands
 :clear               - Clear command output
 :q, :quit, :exit     - Disconnect
@@ -276,9 +279,24 @@ See [docs/DEPLOYMENT.md](docs/DEPLOYMENT.md) for details.
 ```
 messages.log    - Chat history (RFC3339 format)
 host_key        - SSH host key (auto-generated, 4096-bit RSA)
+motd.txt        - Message of the Day (optional, shown to users on connect)
 tnt.service     - systemd service unit
 ```
 
+### MOTD (Message of the Day)
+
+Place a `motd.txt` file in the state directory to show a welcome message to every user on connect. Users see the MOTD before entering the chat and press any key to continue.
+
+```sh
+# Example (assuming default state dir)
+cat > motd.txt <<'EOF'
+Welcome to the chat server!
+Be respectful. No spam.
+EOF
+```
+
+Delete `motd.txt` to disable the MOTD.
+
 ## Documentation
 
 - [Development Guide](https://github.com/m1ngsama/TNT/wiki/Development-Guide) - Complete development manual
@@ -300,7 +318,7 @@ tnt.service     - systemd service unit
 ## Known Limitations
 
 - Single chat room (no multi-room support yet)
-- Keeps only last 100 messages in memory
+- TUI displays at most 100 messages at once; use `:last N` or `:search` to access older history from disk
 - Ctrl+W only recognizes ASCII space as word boundary
 
 ## Contributing

docs/CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## 2026-04-23 - Chat UX Commands and MOTD
+
+### Added
+- **`:last [N]`** — show last N messages retrieved directly from the log file (1–50, default 10), bypassing the 100-message in-memory ring buffer limit
+- **`:search <keyword>`** — case-insensitive full-text search across the entire message history on disk; returns the most recent 15 matches
+- **`:mute-joins`** — per-client toggle to silence join/leave system notifications; title bar shows `[静音]` when active
+- **MOTD support** — place `motd.txt` in the state directory; users see it on connect and press any key to enter chat
+- **`message_search()`** — new function in `message.c` / `message.h` for log file keyword search with rolling result collection
+- Updated in-TUI help screens (English and Chinese) with new commands
+
 ## 2026-03-10 - SSH Runtime & Unix Interface Update
 
 ### Fixed

docs/DEPLOYMENT.md

@@ -89,6 +89,24 @@ Recommended interpretation:
 - `TNT_MAX_CONN_RATE_PER_IP`: new connection attempts allowed per IP per 60 seconds
 - `TNT_RATE_LIMIT=0`: disables rate-based blocking and auth-failure IP blocking, but not the explicit capacity limits
 
+## MOTD (Message of the Day)
+
+Place a `motd.txt` file in the state directory. TNT displays it to each user on connect; they press any key to enter the chat.
+
+```bash
+# Systemd deployment (state dir is /var/lib/tnt)
+sudo tee /var/lib/tnt/motd.txt <<'EOF'
+Welcome! Be respectful. No spam.
+Type :help for available commands.
+EOF
+sudo chown tnt:tnt /var/lib/tnt/motd.txt
+
+# Remove to disable
+sudo rm /var/lib/tnt/motd.txt
+```
+
+No restart required — TNT reads the file on each new connection.
+
 ## Firewall
 
 ```bash

docs/QUICKREF.md

@@ -17,21 +17,37 @@ DEBUG
   valgrind --leak-check=full ./tnt
   make check
 
+COMMANDS (COMMAND mode, prefix with :)
+  list, users, who       show online users
+  nick <name>            change nickname
+  msg <user> <text>      whisper to user
+  w <user> <text>        alias for msg
+  last [N]               last N messages from log (default 10, max 50)
+  search <keyword>       search full history (case-insensitive, 15 results)
+  mute-joins             toggle join/leave notifications
+  help                   show all commands
+  clear                  clear output
+  q / quit / exit        disconnect
+
+INSERT MODE
+  /me <action>           action message
+  @username              mention (bell + highlight)
+
 STRUCTURE
   src/main.c          entry, signals
-  src/ssh_server.c    SSH, threads
+  src/ssh_server.c    SSH, threads, commands
   src/chat_room.c     broadcast
-  src/message.c       persistence
-  src/tui.c           rendering
+  src/message.c       persistence, search
+  src/tui.c           rendering, help
   src/utf8.c          unicode
 
 LIMITS
-  64 clients max
-  100 messages in RAM
+  64 clients max (configurable)
+  100 messages in RAM; unlimited on disk
   1024 bytes/message
 
 FILES
-  HACKING           dev guide
-  CHANGELOG.md      changes
-  messages.log      chat log
-  host_key          SSH key
+  messages.log      chat log (RFC3339)
+  host_key          SSH key (auto-generated)
+  motd.txt          message of the day (optional)
+  CHANGELOG.md      version history

docs/ROADMAP.md

@@ -59,11 +59,11 @@ Goal: keep the interface efficient for terminal users without sacrificing simpli
 - keep the current modal editing model, but make its behavior precise and documented
 - support resize, cursor movement, command history, and predictable paste behavior
 - add useful chat commands with clear semantics:
-  - `/nick`
-  - `/me`
-  - `/last N`
-  - `/search`
-  - `/mute-joins`
+  - ✅ `:nick` / `:name` — nickname change with broadcast
+  - ✅ `/me` — action messages
+  - ✅ `:last N` — show last N messages from disk history
+  - ✅ `:search <keyword>` — case-insensitive full-text search
+  - ✅ `:mute-joins` — per-client join/leave notification toggle
 - improve discoverability of NORMAL and COMMAND mode actions
 - make status lines and help output concise enough for small terminals
 

tnt.1

@@ -107,6 +107,9 @@ l l.
 :name \fIname\fR	Alias for :nick
 :msg \fIuser text\fR	Send private whisper
 :w \fIuser text\fR	Short alias for :msg
+:last [\fIN\fR]	Show last N messages from history (1\-50, default 10)
+:search \fIkeyword\fR	Case\-insensitive search across full message history
+:mute\-joins	Toggle join/leave system notifications on/off
 :help	Show available commands
 :clear	Clear command output
 :q, :quit, :exit	Disconnect
@@ -167,6 +170,12 @@ Stored in the state directory.
 .I host_key
 RSA 4096\-bit host key, auto\-generated on first run.
 Stored in the state directory with mode 0600.
+.TP
+.I motd.txt
+Optional Message of the Day.
+When present in the state directory, its contents are shown to each user
+immediately on connect before the chat screen appears.
+Delete the file to disable the MOTD.
 .SH SYSTEMD
 A unit file
 .I tnt.service