Mcc Dev Workflow

MCC Development Workflow

Use this skill when the task needs a real local server loop, not just code reading.

Defaults

• Solution: MinecraftClient.sln
• Runtime target: .NET 10 / net10.0
• Environment: Linux, macOS, or WSL with Java, tmux, python3, and dotnet available
• Default server root after source tools/mcc-env.sh: ${MCC_SERVERS:-<repo>/MinecraftOfficial/downloads}
• Default validation target when the user does not specify a version: 1.21.11

Console modes

MCC supports two console modes selectable via ConsoleMode in [Console.General]:

Both modes support the same commands and input/output through ConsoleIO.Backend. The mode is determined at startup from config; BasicIO CLI arg overrides to simple stdio.

Core rules

• Prefer a real local server over static reasoning for protocol, login, movement, inventory, entity, or command-path work.
• Treat tmux mc-* sessions as shared state. Do not run multi-version server workflows in parallel unless the harness explicitly isolates them.
• For scripted or repeatable runs, use a generated temporary config. Do not edit the repo-root MinecraftClient.ini as part of the test loop.
• A server log line containing Done ( means startup finished. It does not guarantee that RCON is ready on the first attempt. Retry early mc-rcon commands.
• When instructions, docs, and code disagree, trust current code and current tool behavior first.

Shared server, isolated MCC sessions

• mc-* commands operate on the shared local Minecraft server.
• mcc-* commands operate on one MCC client session.
• The default session is the current worktree name.
• The default username is derived from session, unless you pass --username.
• Session files live under ${TMPDIR:-/tmp}/mcc-debug/<session>/.
• MCC_SERVERS stays the shared server-root override.

Keep shared servers running by default. Do not stop or reset them unless the user explicitly asks for that, or you need to switch server versions.

Two worktrees can debug against one shared server like this:

# worktree A
cd ~/Minecraft/Minecraft-Console-Client
source tools/mcc-env.sh
mc-start 1.21.11
mcc-debug -v 1.21.11 --file-input

# worktree B
cd ~/Minecraft/Minecraft-Console-Client-foo
source tools/mcc-env.sh
mcc-debug -v 1.21.11 --file-input

# from each worktree, mcc-* targets that worktree's default session
mcc-state

If you want two MCC sessions from the same worktree, pass --session NAME explicitly.

tmpfs build mode

Use this on machines with enough RAM when you want worktree-isolated builds outside the repo tree:

source tools/mcc-env.sh
export MCC_BUILD_MODE=tmpfs
mcc-build
mcc-build-clean

MCC_BUILD_MODE=tmpfs redirects build output to /dev/shm/mcc-build/<worktree>/ on Linux, or ${TMPDIR:-/tmp}/mcc-build/<worktree>/ if /dev/shm is unavailable.

Preflight and reset

Before scripted runs, especially on macOS or in a reused tmux environment:

source tools/mcc-env.sh
mcc-preflight 1.21.11
mc-reset-test-env 1.21.11

mcc-preflight checks Java, tmux, dotnet, python3, and server directories. It also resolves common Homebrew Java paths on macOS. mc-reset-test-env clears stale tmux sessions and stale stdin.pipe files before they turn into misleading startup failures.

Build

source tools/mcc-env.sh
mcc-build

Use mcc-build for normal local development so any MCC_BUILD_MODE=tmpfs routing stays active. Only use raw dotnet build when you are intentionally debugging the build system itself.

Server management

Interactive shell:

source tools/mcc-env.sh
SESSION="$(_mcc_resolve_session)"
USERNAME="$(_mcc_resolve_username "$SESSION")"
mc-start 1.21.11
mc-log 1.21.11 100
mc-rcon "op $USERNAME"
mc-stop 1.21.11

Non-interactive shell:

tools/start-server.sh 1.21.11
tools/mc-rcon.sh "op mcc_smoke_a"

If the servers live outside the repo, set MCC_SERVERS before sourcing or invoking the tools:

export MCC_SERVERS=/home/anon/Minecraft/Servers
source tools/mcc-env.sh

One-step debug session (recommended)

The tools/mcc-debug.sh script handles build, server startup, config preparation, and MCC launch in one step:

source tools/mcc-env.sh

# Classic mode with FileInput (script-driven debugging):
mcc-debug -v 1.21.11 --file-input

# Classic mode interactive (attach via tmux):
mcc-debug -v 1.21.11

# TUI mode:
mcc-debug -v 1.21.11 -m tui

# With debug messages enabled from start:
mcc-debug -v 1.21.11 --file-input --debug-on

# Skip build (already built):
mcc-debug -v 1.21.11 --file-input --no-build

What mcc-debug.sh does

1. Builds MCC (unless --no-build)
2. Creates a clean temp config at ${TMPDIR:-/tmp}/mcc-debug/<session>/MinecraftClient.debug.ini
3. Ensures server is running (starts if not, waits for Done ()
4. Launches MCC in a session-scoped tmux session and session-scoped log/input/pid files

After launch

• FileInput mode: drive MCC via mcc-cmd --session smoke-a "debug state", or just mcc-cmd "debug state" from the same worktree
• Interactive/TUI mode: attach with tmux attach -t mcc-<session>
• Logs: mcc-log-mcc --session smoke-a or tail -f "${TMPDIR:-/tmp}/mcc-debug/<session>/mcc-debug.log"
• Server RCON: grant op or gamemode to the username derived from that session

Debug commands (in-game)

/debug [on|off]

Toggles debug logging. Now correctly syncs both Settings.Config.Logging.DebugMessages and McClient.Log.DebugEnabled.

/debug state

Prints a one-shot summary of MCC's internal state:

=== MCC Debug State ===
Server:    localhost:25565
Username:  mcc_smoke_a
Protocol:  774
GameMode:  1
Health:    20.0
Food:      20
Location:  0.50, 80.00, 0.50
TPS:       20.0
Console:   ClassicConsoleBackend    (or TuiConsoleBackend)
Features:  Terrain Inventory Entity
Debug:     ON
Bots (3):  AutoFishing, FileInputBot, ScriptScheduler
Players:   2 online

This works in both classic and TUI modes.

Classic mode debugging

Agent workflow (FileInput mode)

For agents calling MCC commands programmatically:

source tools/mcc-env.sh
SESSION="smoke-a"
mcc-debug -v 1.21.11 --file-input --session "$SESSION" --no-build

# Send commands:
mcc-cmd --session "$SESSION" "debug state"
mcc-cmd --session "$SESSION" "inventory player list"
mcc-cmd --session "$SESSION" "entity"

# Check results:
mcc-log-mcc --session "$SESSION"

# Stop:
mcc-cmd --session "$SESSION" "quit"
mcc-kill --session "$SESSION"
mc-stop 1.21.11

Interactive workflow

source tools/mcc-env.sh
SESSION="live-a"
mcc-debug -v 1.21.11 --session "$SESSION"

# In another terminal:
tmux attach -t "mcc-$SESSION"
# Type commands directly in MCC console

TUI mode debugging

TUI mode runs Consolonia full-screen in a tmux session. Key differences:

1. No pipe/redirect: TUI needs a real tty. Cannot | tee or redirect stdout.
2. Log output is in-screen: all output appears in the scrollable log area.
3. Keyboard shortcuts: PageUp/PageDown scroll, ESC exits.
4. /debug state: the primary way to inspect internal state since external log tailing is not available.
5. Dialog windows: /inventui opens as an overlay dialog instead of a separate screen.

Agent workflow for TUI mode

source tools/mcc-env.sh
SESSION="tui-a"
mcc-debug -v 1.21.11 -m tui --session "$SESSION" --no-build

# Cannot use mcc-cmd (no FileInput); must use tmux send-keys:
tmux send-keys -t "mcc-$SESSION" "/debug state" Enter

# Read TUI screen:
tmux capture-pane -t "mcc-$SESSION" -p -S -30

# Stop:
tmux send-keys -t "mcc-$SESSION" Escape

Caveat with tmux send-keys and Consolonia: When sending text containing /, the Enter key may need to be sent separately:

tmux send-keys -t "mcc-$SESSION" "/inventory player list"
tmux send-keys -t "mcc-$SESSION" Enter

mcc-env.sh quick reference

After source tools/mcc-env.sh:

Temporary config recipe

source tools/mcc-env.sh
SESSION="smoke-a"
USERNAME="$(_mcc_resolve_username "$SESSION")"
CFG="$(_mcc_session_root "$SESSION")/MinecraftClient.debug.ini"
mkdir -p "$(_mcc_session_root "$SESSION")"
bash "$MCC_REPO/.skills/mcc-integration-testing/scripts/prepare_offline_mcc_config.sh" \
  "$CFG" \
  "1.21.11" \
  "$USERNAME"

For TUI mode, also add:

sed -i 's/ConsoleMode = "classic"/ConsoleMode = "tui"/' "$CFG"

Verify connection and a basic command

MCC output should include:

• [MCC] Server was successfully joined.

Server output should include the session-derived username, for example:

• mcc_smoke_a joined the game

Basic command check:

mcc-cmd --session smoke-a "inventory player list"

If a scripted run fails before MCC joins, check for a harness problem before assuming a product regression. Missing mcc.log, a pre-join Connection refused, or a server that never reached Done ( usually means shared-state cleanup or startup failed.

Typical debug loop

1. source tools/mcc-env.sh
2. mcc-debug -v 1.21.11 --file-input (or -m tui)
3. Confirm Server was successfully joined in log
4. mcc-cmd "debug state" to verify MCC state
5. Run test commands
6. Inspect log output
7. mcc-cmd "quit" and mc-stop 1.21.11
8. Edit code, rebuild, repeat

Debugging tips

• /debug state is your primary diagnostic tool in both modes. Use it first to verify connection, mode, and feature flags.
• /debug on now correctly enables debug logging at runtime. Previous versions had a bug where Log.DebugEnabled was not synced.
• Protocol mismatches usually show up as a version line such as Server version : 1.21.11 (protocol vNNN) before the failure.
• If an early mc-rcon command fails, retry it before assuming the server setup is broken.
• If a supposedly isolated run behaves strangely, check tmux list-sessions and kill stale mc-* sessions first.
• Legacy 1.8 and 1.8.9 servers may need use-native-transport=false in server.properties on some Linux environments.
• For timing-sensitive work, do not trust wall-clock intuition. Use a real server run and capture evidence from logs or test scripts.
• TUI mode tip: if the terminal becomes unresponsive after a crash, run stty sane && reset to restore it.
• tmux capture trick: tmux capture-pane -t mcc-<session> -p -S -50 captures the last 50 lines of a tmux session without attaching.

Tool files