diff --git a/code_puppy/plugins/personality_tone/__init__.py b/code_puppy/plugins/personality_tone/__init__.py
new file mode 100644
index 000000000..8b97467b4
--- /dev/null
+++ b/code_puppy/plugins/personality_tone/__init__.py
@@ -0,0 +1 @@
+"""Personality tone control plugin."""
diff --git a/code_puppy/plugins/personality_tone/register_callbacks.py b/code_puppy/plugins/personality_tone/register_callbacks.py
new file mode 100644
index 000000000..d3757ae76
--- /dev/null
+++ b/code_puppy/plugins/personality_tone/register_callbacks.py
@@ -0,0 +1,191 @@
+"""Plugin for controlling Code Puppy's response tone.
+
+The core Code Puppy prompt intentionally has a playful personality. This plugin
+keeps that prompt unchanged and appends a configurable tone override through the
+existing load_prompt hook.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Callable
+
+from code_puppy.callbacks import register_callback
+from code_puppy.config import get_value, set_config_value
+from code_puppy.messaging import emit_error, emit_info, emit_success, emit_warning
+
+CONFIG_KEY = "personality_tone"
+DEFAULT_TONE = "default"
+
+
+@dataclass(frozen=True)
+class ToneProfile:
+    description: str
+    prompt: str
+
+
+TONE_PROFILES: dict[str, ToneProfile] = {
+    "professional": ToneProfile(
+        description="Dry, direct, business-professional responses",
+        prompt="""
+## Tone Override
+
+This section supersedes earlier playful or sassy personality guidance.
+- Use a business-professional tone: direct, concise, objective, and practical.
+- Avoid sass, sarcasm, cutesy phrasing, pet/dog jokes, playful metaphors, and emojis unless the user explicitly asks.
+- Keep the focus on the engineering objective, tradeoffs, risks, verification, and next steps.
+- Do not mention this tone policy unless the user asks about it.
+""",
+    ),
+    "neutral": ToneProfile(
+        description="Friendly and restrained, with minimal personality",
+        prompt="""
+## Tone Override
+
+This section supersedes earlier playful or sassy personality guidance.
+- Use a friendly but restrained tone.
+- Keep humor and personality light, rare, and secondary to technical clarity.
+- Avoid sarcasm, cutesy phrasing, pet/dog jokes, and emojis unless the user explicitly asks.
+- Do not mention this tone policy unless the user asks about it.
+""",
+    ),
+    "default": ToneProfile(
+        description="Native Code Puppy personality with no extra override",
+        prompt="",
+    ),
+    "playful": ToneProfile(
+        description="Explicitly playful, while staying useful and concise",
+        prompt="""
+## Tone Override
+
+Use Code Puppy's playful personality, but keep it useful.
+- Light humor is fine when it does not distract from the task.
+- Keep technical answers accurate, actionable, and concise.
+- Do not let jokes, sass, or roleplay obscure risks, bugs, commands, or next steps.
+""",
+    ),
+}
+
+ALIASES: dict[str, str] = {
+    "0": "professional",
+    "business": "professional",
+    "business-professional": "professional",
+    "dry": "professional",
+    "direct": "professional",
+    "serious": "professional",
+    "1": "neutral",
+    "balanced": "neutral",
+    "friendly": "neutral",
+    "minimal": "neutral",
+    "2": "default",
+    "native": "default",
+    "normal": "default",
+    "off": "default",
+    "reset": "default",
+    "3": "playful",
+    "fun": "playful",
+    "sassy": "playful",
+    "spunky": "playful",
+}
+
+
+def normalize_tone(value: str | None) -> str:
+    """Return a supported tone name, falling back to the default tone."""
+    if value is None:
+        return DEFAULT_TONE
+
+    normalized = value.strip().lower()
+    if not normalized:
+        return DEFAULT_TONE
+    if normalized in TONE_PROFILES:
+        return normalized
+    return ALIASES.get(normalized, DEFAULT_TONE)
+
+
+def get_current_tone() -> str:
+    """Read the configured tone from persistent config."""
+    return normalize_tone(get_value(CONFIG_KEY))
+
+
+def get_tone_prompt_addition() -> str:
+    """Return the prompt addition for the current tone.
+
+    load_prompt callbacks must return a string. Returning an empty string keeps
+    the default prompt behavior unchanged while still satisfying the hook.
+    """
+    return TONE_PROFILES[get_current_tone()].prompt
+
+
+def _custom_help() -> list[tuple[str, str]]:
+    return [
+        (
+            "tone",
+            "Set response tone: professional, neutral, default, playful",
+        )
+    ]
+
+
+def _available_tones_text() -> str:
+    lines = ["Available tones:"]
+    for tone_name in ("professional", "neutral", "default", "playful"):
+        profile = TONE_PROFILES[tone_name]
+        lines.append(f"  - {tone_name}: {profile.description}")
+    lines.append("")
+    lines.append("Usage: /tone <professional|neutral|default|playful>")
+    lines.append("Aliases: /tone 0, /tone 1, /tone 2, /tone 3")
+    return "\n".join(lines)
+
+
+def _show_tone() -> None:
+    tone = get_current_tone()
+    emit_info(f"Personality tone: {tone}")
+    emit_info(_available_tones_text())
+
+
+def _reload_current_agent() -> None:
+    try:
+        from code_puppy.agents import get_current_agent
+
+        get_current_agent().reload_code_generation_agent()
+        emit_info("Agent reloaded with updated tone prompt.")
+    except Exception as exc:
+        emit_warning(f"Tone saved, but agent reload failed: {exc}")
+
+
+def _set_tone(
+    raw_tone: str, reload_agent: Callable[[], None] = _reload_current_agent
+) -> None:
+    tone = normalize_tone(raw_tone)
+    if tone == DEFAULT_TONE and raw_tone.strip().lower() not in {
+        DEFAULT_TONE,
+        *ALIASES,
+    }:
+        valid = ", ".join(TONE_PROFILES)
+        emit_error(f"Unknown tone '{raw_tone}'. Valid tones: {valid}")
+        return
+
+    set_config_value(CONFIG_KEY, tone)
+    emit_success(f"Personality tone set to {tone}.")
+    reload_agent()
+
+
+def _handle_custom_command(command: str, name: str) -> bool | None:
+    if name != "tone":
+        return None
+
+    parts = command.split()
+    if len(parts) == 1 or parts[1].lower() in {"show", "list", "help"}:
+        _show_tone()
+        return True
+
+    if len(parts) > 2:
+        emit_error("Usage: /tone <professional|neutral|default|playful>")
+        return True
+
+    _set_tone(parts[1])
+    return True
+
+
+register_callback("load_prompt", get_tone_prompt_addition)
+register_callback("custom_command_help", _custom_help)
+register_callback("custom_command", _handle_custom_command)
diff --git a/tests/plugins/test_personality_tone.py b/tests/plugins/test_personality_tone.py
new file mode 100644
index 000000000..cf34d9811
--- /dev/null
+++ b/tests/plugins/test_personality_tone.py
@@ -0,0 +1,101 @@
+"""Tests for the personality tone plugin."""
+
+from __future__ import annotations
+
+from unittest.mock import Mock, patch
+
+from code_puppy.plugins.personality_tone import register_callbacks as plugin
+
+
+def test_normalize_tone_accepts_names_and_aliases():
+    assert plugin.normalize_tone("professional") == "professional"
+    assert plugin.normalize_tone("dry") == "professional"
+    assert plugin.normalize_tone("1") == "neutral"
+    assert plugin.normalize_tone("off") == "default"
+    assert plugin.normalize_tone("spunky") == "playful"
+
+
+def test_normalize_tone_defaults_unknown_values():
+    assert plugin.normalize_tone(None) == "default"
+    assert plugin.normalize_tone("") == "default"
+    assert plugin.normalize_tone("unknown") == "default"
+
+
+def test_default_tone_preserves_existing_prompt_behavior():
+    with patch(
+        "code_puppy.plugins.personality_tone.register_callbacks.get_value",
+        return_value="default",
+    ):
+        assert plugin.get_tone_prompt_addition() == ""
+
+
+def test_professional_tone_adds_override():
+    with patch(
+        "code_puppy.plugins.personality_tone.register_callbacks.get_value",
+        return_value="professional",
+    ):
+        prompt = plugin.get_tone_prompt_addition()
+
+    assert "Tone Override" in prompt
+    assert "business-professional" in prompt
+    assert "supersedes earlier playful or sassy" in prompt
+    assert "Avoid sass" in prompt
+
+
+def test_handle_tone_show_emits_current_tone_and_options():
+    with (
+        patch(
+            "code_puppy.plugins.personality_tone.register_callbacks.get_value",
+            return_value="neutral",
+        ),
+        patch(
+            "code_puppy.plugins.personality_tone.register_callbacks.emit_info"
+        ) as emit_info,
+    ):
+        result = plugin._handle_custom_command("/tone", "tone")
+
+    assert result is True
+    assert "Personality tone: neutral" in str(emit_info.call_args_list[0])
+    assert "Available tones" in str(emit_info.call_args_list[1])
+
+
+def test_handle_tone_sets_config_and_reloads():
+    reload_agent = Mock()
+
+    with (
+        patch(
+            "code_puppy.plugins.personality_tone.register_callbacks.set_config_value"
+        ) as set_config,
+        patch("code_puppy.plugins.personality_tone.register_callbacks.emit_success"),
+    ):
+        plugin._set_tone("dry", reload_agent=reload_agent)
+
+    set_config.assert_called_once_with(plugin.CONFIG_KEY, "professional")
+    reload_agent.assert_called_once_with()
+
+
+def test_handle_tone_rejects_unknown_tone():
+    reload_agent = Mock()
+
+    with (
+        patch(
+            "code_puppy.plugins.personality_tone.register_callbacks.set_config_value"
+        ) as set_config,
+        patch(
+            "code_puppy.plugins.personality_tone.register_callbacks.emit_error"
+        ) as emit_error,
+    ):
+        plugin._set_tone("weird", reload_agent=reload_agent)
+
+    set_config.assert_not_called()
+    reload_agent.assert_not_called()
+    assert "Unknown tone" in str(emit_error.call_args)
+
+
+def test_custom_help_includes_tone_command():
+    entries = dict(plugin._custom_help())
+    assert "tone" in entries
+
+
+def test_handle_custom_command_ignores_other_commands():
+    assert plugin._handle_custom_command("/other", "other") is None