//! Settings system - Persistent user preferences
//!
//! Settings are stored at ~/.config/deepseek/settings.toml
//!
//! TUI-specific preferences (theme, keybinds, font_size) that survive project
//! switches are stored separately at ~/.deepseek/tui.toml. See [`TuiPrefs`].

use std::path::PathBuf;

use anyhow::{Context, Result};
use serde::{Deserialize, Serialize};

use crate::config::{expand_path, normalize_model_name};
use crate::localization::normalize_configured_locale;
use crate::palette::{normalize_hex_rgb_color, normalize_theme_name};

// ============================================================================
// TuiPrefs — ~/.deepseek/tui.toml
// ============================================================================

/// TUI-specific preferences that are decoupled from agent/project config so
/// they survive project switches (issue #437).
///
/// Stored at `~/.deepseek/tui.toml`. When the file is absent the values fall
/// back to the `[tui]` section of the normal `config.toml` (via
/// [`TuiPrefs::load`]), and then to the struct's own defaults.
///
/// # Example `~/.deepseek/tui.toml`
///
/// ```toml
/// theme    = "dark"        # "system" | "dark" | "light" | "grayscale" | "catppuccin-mocha" | ...
/// font_size = 14
///
/// [keybinds]
/// submit   = "ctrl+enter"
/// new_line = "enter"
/// ```
//
// NOTE: the loader is defined but not yet called from startup — wiring is
// deferred to a later settings pass (#657). The `#[allow(dead_code)]` suppresses the CI
// `-D warnings` failure until the call site lands.
#[allow(dead_code)]
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(default)]
pub struct TuiPrefs {
    /// UI colour theme.
    /// Default `"dark"`.
    pub theme: String,
    /// Terminal font size hint forwarded to supporting front-ends (e.g. the
    /// Tauri shell). `0` means "use terminal default". Default `0`.
    pub font_size: u16,
    /// Key-binding overrides. Each field accepts an xterm-style chord string
    /// such as `"ctrl+enter"`, `"alt+n"`, or `"f1"`.
    pub keybinds: KeybindPrefs,
}

impl Default for TuiPrefs {
    fn default() -> Self {
        Self {
            theme: "dark".to_string(),
            font_size: 0,
            keybinds: KeybindPrefs::default(),
        }
    }
}

/// Per-action keybinding overrides stored inside [`TuiPrefs`].
#[allow(dead_code)] // see TuiPrefs note above; deferred to a later settings pass (#657).
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
#[serde(default)]
pub struct KeybindPrefs {
    /// Key to submit the current composer input to the model.
    /// Default: `"ctrl+enter"`.
    pub submit: Option<String>,
    /// Key to insert a literal newline inside the composer.
    /// Default: `"enter"`.
    pub new_line: Option<String>,
    /// Key to open the command palette.
    /// Default: `"ctrl+k"`.
    pub command_palette: Option<String>,
    /// Key to cancel / interrupt a running turn.
    /// Default: `"ctrl+c"`.
    pub cancel: Option<String>,
    /// Key to toggle the sidebar.
    /// Default: `"ctrl+b"`.
    pub toggle_sidebar: Option<String>,
}

#[allow(dead_code)] // see TuiPrefs note above; deferred to a later settings pass (#657).
impl TuiPrefs {
    /// Return the canonical path of the TUI preferences file:
    /// `~/.deepseek/tui.toml`.
    ///
    /// Tests may override the home directory through the
    /// `DEEPSEEK_CONFIG_PATH` environment variable (the parent directory of
    /// the pointed-to config is used instead of `~/.deepseek`).
    pub fn path() -> Result<PathBuf> {
        // Honour the same env-var escape hatch used by Settings::path so that
        // integration tests can redirect all config I/O to a temp directory.
        if let Ok(config_path) = std::env::var("DEEPSEEK_CONFIG_PATH") {
            let config_path = config_path.trim();
            if !config_path.is_empty() {
                let p = expand_path(config_path);
                if let Some(parent) = p.parent() {
                    return Ok(parent.join("tui.toml"));
                }
            }
        }

        let home = dirs::home_dir()
            .context("Failed to resolve home directory: cannot determine tui.toml path.")?;
        Ok(home.join(".deepseek").join("tui.toml"))
    }

    /// Load TUI preferences from `~/.deepseek/tui.toml`.
    ///
    /// If the file does not exist the struct defaults are returned — no error
    /// is produced. Parse errors surface as `Err` so the caller can warn the
    /// user without crashing the session.
    pub fn load() -> Result<Self> {
        let path = Self::path()?;
        if !path.exists() {
            return Ok(Self::default());
        }
        let content = std::fs::read_to_string(&path)
            .with_context(|| format!("Failed to read tui.toml from {}", path.display()))?;
        let prefs: TuiPrefs = toml::from_str(&content)
            .with_context(|| format!("Failed to parse tui.toml from {}", path.display()))?;
        Ok(prefs)
    }

    /// Save TUI preferences to `~/.deepseek/tui.toml`, creating the
    /// `~/.deepseek` directory if needed.
    pub fn save(&self) -> Result<()> {
        let path = Self::path()?;
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent).with_context(|| {
                format!("Failed to create config directory {}", parent.display())
            })?;
        }
        let content = toml::to_string_pretty(self).context("Failed to serialize TuiPrefs")?;
        std::fs::write(&path, content)
            .with_context(|| format!("Failed to write tui.toml to {}", path.display()))?;
        Ok(())
    }

    /// Validate field values and normalise them in place.
    ///
    /// Returns `Err` if an unrecognised `theme` value is found so callers can
    /// surface a helpful message rather than silently ignoring a typo.
    pub fn validate(&mut self) -> Result<()> {
        let theme = self.theme.trim().to_ascii_lowercase();
        let Some(theme) = normalize_theme_name(&theme) else {
            anyhow::bail!(
                "Invalid tui.toml theme '{}': expected system, dark, light, grayscale, catppuccin-mocha, tokyo-night, dracula, or gruvbox-dark.",
                self.theme
            );
        };
        self.theme = theme.to_string();
        Ok(())
    }
}

/// User settings with defaults
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(default)]
pub struct Settings {
    /// Auto-compact conversations when they approach the model limit.
    pub auto_compact: bool,
    /// Reduce status noise and collapse details more aggressively
    pub calm_mode: bool,
    /// Streaming pacing mode. `true` pins the chunker to one-character-per-
    /// commit-tick (typewriter); `false` drains the upstream cadence (each
    /// commit flushes everything queued, which matches V4-pro's burst pattern
    /// when the prefix cache is warm). Has no effect on the footer water-spout
    /// animation — that is gated independently by [`Self::fancy_animations`].
    pub low_motion: bool,
    /// Enable the footer water-spout animation strip during live turns. The
    /// strip's wave cadence is synchronized with the character-commit rate, so
    /// the visual flow matches whatever streaming pacing [`Self::low_motion`]
    /// selects: typewriter mode drips, upstream mode surges, tool calls /
    /// planning pauses freeze the surface. Set `false` to keep the gap as
    /// plain whitespace.
    pub fancy_animations: bool,
    /// Enable terminal bracketed-paste mode. Default true. Disable if your
    /// terminal mishandles the `\e[?2004h` escape (rare; some legacy
    /// terminals over SSH+screen multiplex without the cap).
    pub bracketed_paste: bool,
    /// Enable rapid-key paste-burst detection for terminals that do not emit
    /// bracketed-paste events. Independent from `bracketed_paste`.
    pub paste_burst_detection: bool,
    /// Show thinking blocks from the model
    pub show_thinking: bool,
    /// Show detailed tool output
    pub show_tool_details: bool,
    /// UI locale: auto, en, ja, zh-Hans, pt-BR, es-419
    pub locale: String,
    /// Named UI theme. Accepts `"system"` (follow terminal background),
    /// `"dark"`, `"light"`, `"grayscale"`, or one of the community
    /// presets: `"catppuccin-mocha"`, `"tokyo-night"`, `"dracula"`,
    /// `"gruvbox-dark"`. The `background_color` setting still overrides the
    /// surface color on top of the resolved theme.
    pub theme: String,
    /// Optional main TUI background color as a 6-digit hex RGB value.
    pub background_color: Option<String>,
    /// Composer layout density: compact, comfortable, spacious
    pub composer_density: String,
    /// Show a border around the composer input area
    pub composer_border: bool,
    /// Composer editing mode: "normal" (default) or "vim" for modal editing.
    /// When set to "vim" the composer starts in Normal mode; press i/a/o to
    /// enter Insert mode and Esc to return to Normal.
    pub composer_vim_mode: String,
    /// Transcript spacing rhythm: compact, comfortable, spacious
    pub transcript_spacing: String,
    /// Default mode: "agent", "plan", "yolo"
    pub default_mode: String,
    /// Sidebar width as percentage of terminal width
    pub sidebar_width_percent: u16,
    /// Sidebar focus mode: auto, work, tasks, agents, context, hidden
    pub sidebar_focus: String,
    /// Enable the session-context panel (#504). Shows working set, tokens,
    /// cost, MCP/LSP status, cycle count, and memory info.
    pub context_panel: bool,
    /// Cost display currency: usd or cny.
    pub cost_currency: String,
    /// Maximum number of input history entries to save
    pub max_input_history: usize,
    /// Default provider override (e.g. "deepseek", "openai").
    pub default_provider: Option<String>,
    /// Default model to use
    pub default_model: Option<String>,
    /// Default reasoning effort selected from the TUI model picker.
    /// `None` falls back to `config.toml` and then the runtime default.
    pub reasoning_effort: Option<String>,
    /// Per-provider model overrides. Key is provider name (e.g. "openai"),
    /// value is the model id. Takes precedence over `default_model`.
    pub provider_models: Option<std::collections::HashMap<String, String>>,
    /// Header status indicator next to the effort chip. Cycles through a
    /// per-turn animation keyed off `App::turn_started_at`:
    /// - `"whale"` (default): historical `🐳 → 🐋` 12-frame sequence
    ///   originally shipped in v0.3.5, removed in v0.8.x's "smoother TUI
    ///   streaming" pass, restored in v0.8.30. Idle frame is a steady `🐳`.
    /// - `"dots"`: the 6-frame geometric sequence (`◍ ◉ ◌ ◌ ◉ ◍`) that
    ///   replaced the whale during the dots era.
    /// - `"off"`: hide the indicator entirely.
    pub status_indicator: String,
    /// Whether to wrap each draw in DEC mode 2026 synchronized output
    /// (`\x1b[?2026h` … `\x1b[?2026l`). Synchronized output asks the
    /// terminal to defer rendering until the whole frame is staged so
    /// GPU-accelerated terminals (Ghostty, VS Code, Kitty, WezTerm)
    /// don't flash a blank intermediate frame.
    ///
    /// - `"auto"` (default): emit DEC 2026 unless an environment signal
    ///   says the active terminal mishandles it (currently Ptyxis 50.x
    ///   on VTE 0.84.x — see [`Settings::apply_env_overrides`]).
    /// - `"on"`: always emit DEC 2026 (override the auto opt-out).
    /// - `"off"`: never emit DEC 2026. Use this if your terminal flashes
    ///   the whole screen on every redraw — most often Ptyxis on
    ///   Ubuntu 26.04 today; historically also some legacy ssh+screen
    ///   stacks. The cost of `off` is brief tearing on terminals that
    ///   *do* support DEC 2026; it is purely a rendering-quality knob,
    ///   not a correctness one.
    pub synchronized_output: String,
    /// Prefer the external `pdftotext` binary (Poppler) over the bundled
    /// pure-Rust `pdf-extract` extractor for PDF reads in `read_file`.
    /// Pure-Rust extraction is the v0.8.32 default because it removes the
    /// install-poppler-first hurdle most users hit, but `pdftotext -layout`
    /// still wins for column-heavy or complex-table PDFs (academic papers
    /// laid out in two columns, financial filings, etc.). Set to `true` to
    /// route every PDF read through `pdftotext` instead — when the binary
    /// is missing in that mode the tool returns the structured
    /// `binary_unavailable` response with an install hint, matching the
    /// pre-v0.8.32 behavior.
    pub prefer_external_pdftotext: bool,
}

impl Default for Settings {
    fn default() -> Self {
        Self {
            // v0.8.11: default flipped to `false` to stop the engine from
            // routinely rewriting the prompt prefix, which breaks DeepSeek
            // V4's prefix cache (~90% discount on cached prefix tokens) and
            // ends up costing more than the compaction itself saves. With
            // V4's 1M-token window the user has plenty of headroom to run
            // long sessions without auto-trimming, and the explicit
            // `/compact` slash command + `auto_compact = on` opt-in remain
            // available for users / agents that decide compaction is
            // worth the cache hit on their workload (#664).
            auto_compact: false,
            calm_mode: false,
            low_motion: false,
            fancy_animations: true,
            bracketed_paste: true,
            paste_burst_detection: true,
            show_thinking: true,
            show_tool_details: true,
            locale: "auto".to_string(),
            theme: "system".to_string(),
            background_color: None,
            composer_density: "comfortable".to_string(),
            composer_border: true,
            composer_vim_mode: "normal".to_string(),
            transcript_spacing: "comfortable".to_string(),
            default_mode: "agent".to_string(),
            sidebar_width_percent: 28,
            sidebar_focus: "auto".to_string(),
            context_panel: false,
            cost_currency: "usd".to_string(),
            max_input_history: 100,
            default_provider: None,
            default_model: None,
            reasoning_effort: None,
            provider_models: None,
            status_indicator: "whale".to_string(),
            synchronized_output: "auto".to_string(),
            prefer_external_pdftotext: false,
        }
    }
}

impl Settings {
    /// Get the settings file path
    pub fn path() -> Result<PathBuf> {
        // Allow tests to override the settings directory via the same env var
        // used for config (DEEPSEEK_CONFIG_PATH points at config.toml; the
        // settings file lives as a sibling in the same directory).
        if let Ok(config_path) = std::env::var("DEEPSEEK_CONFIG_PATH") {
            let config_path = config_path.trim();
            if !config_path.is_empty() {
                let p = expand_path(config_path);
                if let Some(parent) = p.parent() {
                    return Ok(parent.join("settings.toml"));
                }
            }
        }

        let config_dir = dirs::config_dir()
            .context("Failed to resolve config directory: not found.")?
            .join("deepseek");
        Ok(config_dir.join("settings.toml"))
    }

    /// Load settings from disk, or return defaults if not found
    pub fn load() -> Result<Self> {
        let path = Self::path()?;
        let mut settings = if !path.exists() {
            Self::default()
        } else {
            let content = std::fs::read_to_string(&path)
                .with_context(|| format!("Failed to read settings from {}", path.display()))?;
            let mut s: Settings = toml::from_str(&content)
                .with_context(|| format!("Failed to parse settings from {}", path.display()))?;
            s.default_mode = normalize_mode(&s.default_mode).to_string();
            s.composer_density = normalize_composer_density(&s.composer_density).to_string();
            s.transcript_spacing = normalize_transcript_spacing(&s.transcript_spacing).to_string();
            s.sidebar_focus = normalize_sidebar_focus(&s.sidebar_focus).to_string();
            s.status_indicator = normalize_status_indicator(&s.status_indicator).to_string();
            s.synchronized_output =
                normalize_synchronized_output(&s.synchronized_output).to_string();
            s.locale = normalize_configured_locale(&s.locale)
                .unwrap_or("en")
                .to_string();
            s.background_color = normalize_optional_background_color(s.background_color.as_deref());
            s.theme = normalize_settings_theme(&s.theme).to_string();
            s.default_model = s.default_model.as_deref().and_then(normalize_default_model);
            s.reasoning_effort = s
                .reasoning_effort
                .as_deref()
                .and_then(|value| normalize_reasoning_effort_setting(value).ok().flatten());
            s
        };
        settings.apply_env_overrides();
        Ok(settings)
    }

    /// Apply environment-driven overlays after disk load. Used for
    /// platform a11y signals that should ignore the user's saved
    /// preference (#450). The env values are consulted at startup;
    /// changing them mid-session has no effect because settings are
    /// only re-read on `Settings::load()`.
    pub fn apply_env_overrides(&mut self) {
        if env_truthy("NO_ANIMATIONS") {
            self.low_motion = true;
            self.fancy_animations = false;
        }
        // VS Code (TERM_PROGRAM=vscode, #1356), Ghostty (TERM_PROGRAM=ghostty,
        // #1445), and a few VTE terminals (#1470) produce visible flicker at
        // 120 FPS. Drop to the 30 FPS low-motion cap for them automatically.
        // Like NO_ANIMATIONS above, this unconditionally overrides any
        // disk-loaded value — consistent precedence: env signals always win.
        let vte_env_forces_low_motion = std::env::var_os("TILIX_ID").is_some_and(|v| !v.is_empty())
            || std::env::var_os("TERMINATOR_UUID").is_some_and(|v| !v.is_empty());
        if matches!(
            std::env::var("TERM_PROGRAM").as_deref(),
            Ok("vscode") | Ok("ghostty")
        ) || vte_env_forces_low_motion
        {
            self.low_motion = true;
            self.fancy_animations = false;
        }

        // Termius (TERM_PROGRAM=Termius) and SSH sessions exhibit the
        // same 120-FPS flicker class as VS Code — the SSH round-trip
        // races ahead of what the remote renderer can flush, so rapid
        // cursor-positioning sequences cycle through input boxes.
        // Drop both to the 30 FPS low-motion cap. Harvested from
        // PR #1479 by @CrepuscularIRIS / autoghclaw (closes #1433).
        //
        // SSH_CLIENT is exported by sshd for every TCP SSH session;
        // SSH_TTY is exported only for interactive PTY logins, so we
        // check both so non-PTY-allocating tools (rsync wrappers, etc.)
        // still pick this up if they end up running the TUI.
        let term_is_termius = std::env::var("TERM_PROGRAM").as_deref() == Ok("Termius");
        let in_ssh_session = std::env::var_os("SSH_CLIENT").is_some_and(|v| !v.is_empty())
            || std::env::var_os("SSH_TTY").is_some_and(|v| !v.is_empty());
        if term_is_termius || in_ssh_session {
            self.low_motion = true;
            self.fancy_animations = false;
        }

        // tmux/screen activity monitors treat purely animated redraws as
        // activity. Keep multiplexer sessions calm by pinning animations.
        let in_terminal_multiplexer = std::env::var_os("TMUX").is_some_and(|v| !v.is_empty())
            || std::env::var_os("STY").is_some_and(|v| !v.is_empty());
        if in_terminal_multiplexer {
            self.low_motion = true;
            self.fancy_animations = false;
        }

        // Plain Windows PowerShell / cmd.exe under legacy ConHost exposes none
        // of the modern terminal markers below. Keep rendering calmer there:
        // lower the motion rate, disable animated chrome, and avoid DEC 2026
        // synchronized-output wrapping unless the user explicitly forced it on.
        if detected_legacy_windows_console_host() {
            self.low_motion = true;
            self.fancy_animations = false;
            if self.synchronized_output.eq_ignore_ascii_case("auto") {
                self.synchronized_output = "off".to_string();
            }
        }

        // Ptyxis 50.x (the new default terminal on Ubuntu 26.04) ships with
        // VTE 0.84.x which mishandles DEC mode 2026 synchronized output: the
        // begin/end pair is parsed but each wrapped frame still triggers a
        // full-viewport flash on the GPU compositor side, so any TUI that
        // uses DEC 2026 to avoid tearing instead gets visible flicker on
        // every redraw. gnome-terminal 3.58 on the same VTE renders cleanly,
        // so we can't broaden the opt-out to all VTE-based terminals —
        // only the Ptyxis-specific signals trigger it. Confirmed
        // user-visible regression starting with Ubuntu 26.04's default
        // terminal swap; cargo-installed binaries are not exempt because
        // the bug is in the terminal, not the binary.
        //
        // Only flip `auto` to `off`; respect an explicit `"on"` so users
        // who upgrade Ptyxis or want to confirm the fix landed upstream
        // can override the heuristic from `~/.config/deepseek/settings.toml`
        // or `/set synchronized_output on`.
        if self.synchronized_output.eq_ignore_ascii_case("auto") && detected_ptyxis_terminal() {
            self.synchronized_output = "off".to_string();
        }
    }

    /// Save settings to disk
    pub fn save(&self) -> Result<()> {
        let path = Self::path()?;

        // Create config directory if it doesn't exist
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent).with_context(|| {
                format!("Failed to create config directory {}", parent.display())
            })?;
        }

        let content = toml::to_string_pretty(self).context("Failed to serialize settings")?;
        std::fs::write(&path, content)
            .with_context(|| format!("Failed to write settings to {}", path.display()))?;
        Ok(())
    }

    /// Set a single setting by key
    pub fn set(&mut self, key: &str, value: &str) -> Result<()> {
        match key {
            "auto_compact" | "compact" => {
                self.auto_compact = parse_bool(value)?;
            }
            "calm_mode" | "calm" => {
                self.calm_mode = parse_bool(value)?;
            }
            "low_motion" | "motion" => {
                self.low_motion = parse_bool(value)?;
            }
            "fancy_animations" | "fancy" | "animations" => {
                self.fancy_animations = parse_bool(value)?;
            }
            "bracketed_paste" | "paste" => {
                self.bracketed_paste = parse_bool(value)?;
            }
            "paste_burst_detection" | "paste_burst" => {
                self.paste_burst_detection = parse_bool(value)?;
            }
            "show_thinking" | "thinking" => {
                self.show_thinking = parse_bool(value)?;
            }
            "show_tool_details" | "tool_details" => {
                self.show_tool_details = parse_bool(value)?;
            }
            "locale" | "language" => {
                let Some(locale) = normalize_configured_locale(value) else {
                    anyhow::bail!(
                        "Failed to update setting: invalid locale '{value}'. Expected: auto, en, ja, zh-Hans, pt-BR, es-419."
                    );
                };
                self.locale = locale.to_string();
            }
            "theme" => {
                let Some(id) = crate::palette::ThemeId::from_name(value) else {
                    anyhow::bail!(
                        "Failed to update setting: invalid theme '{value}'. Expected: system, dark, light, grayscale, catppuccin-mocha, tokyo-night, dracula, gruvbox-dark."
                    );
                };
                self.theme = id.name().to_string();
            }
            "ui_theme" => {
                let Some(id) = crate::palette::ThemeId::from_name(value) else {
                    anyhow::bail!(
                        "Failed to update setting: invalid theme '{value}'. Expected: system, dark, light, grayscale, catppuccin-mocha, tokyo-night, dracula, gruvbox-dark."
                    );
                };
                self.theme = id.name().to_string();
            }
            "background_color" | "background" | "bg" => {
                self.background_color = normalize_background_color_setting(value)?;
            }
            "composer_density" | "composer" => {
                let normalized = normalize_composer_density(value);
                if !["compact", "comfortable", "spacious"].contains(&normalized) {
                    anyhow::bail!(
                        "Failed to update setting: invalid composer density '{value}'. Expected: compact, comfortable, spacious."
                    );
                }
                self.composer_density = normalized.to_string();
            }
            "composer_border" | "border" => {
                self.composer_border = parse_bool(value)?;
            }
            "composer_vim_mode" | "vim_mode" | "vim" => {
                let normalized = value.trim().to_ascii_lowercase();
                if !["vim", "normal"].contains(&normalized.as_str()) {
                    anyhow::bail!(
                        "Failed to update setting: invalid composer vim mode '{value}'. Expected: normal, vim."
                    );
                }
                self.composer_vim_mode = normalized;
            }
            "transcript_spacing" | "spacing" => {
                let normalized = normalize_transcript_spacing(value);
                if !["compact", "comfortable", "spacious"].contains(&normalized) {
                    anyhow::bail!(
                        "Failed to update setting: invalid transcript spacing '{value}'. Expected: compact, comfortable, spacious."
                    );
                }
                self.transcript_spacing = normalized.to_string();
            }
            "status_indicator" | "indicator" => {
                let normalized = normalize_status_indicator(value);
                if !["whale", "dots", "off"].contains(&normalized) {
                    anyhow::bail!(
                        "Failed to update setting: invalid status indicator '{value}'. Expected: whale, dots, off."
                    );
                }
                self.status_indicator = normalized.to_string();
            }
            "synchronized_output" | "sync_output" | "sync" => {
                let normalized = normalize_synchronized_output(value);
                if !["auto", "on", "off"].contains(&normalized) {
                    anyhow::bail!(
                        "Failed to update setting: invalid synchronized_output '{value}'. Expected: auto, on, off."
                    );
                }
                self.synchronized_output = normalized.to_string();
            }
            "prefer_external_pdftotext" | "external_pdftotext" | "pdftotext" => {
                self.prefer_external_pdftotext = parse_bool(value)?;
            }
            "default_mode" | "mode" => {
                let normalized = normalize_mode(value);
                if !["agent", "plan", "yolo"].contains(&normalized) {
                    anyhow::bail!(
                        "Failed to update setting: invalid mode '{value}'. Expected: agent, plan, yolo."
                    );
                }
                self.default_mode = normalized.to_string();
            }
            "sidebar_width" | "sidebar" => {
                let width: u16 = value
                    .parse()
                    .map_err(|_| {
                        anyhow::anyhow!(
                            "Failed to update setting: invalid width '{value}'. Expected a number between 10-50."
                        )
                    })?;
                if !(10..=50).contains(&width) {
                    anyhow::bail!(
                        "Failed to update setting: width must be between 10 and 50 percent."
                    );
                }
                self.sidebar_width_percent = width;
            }
            "sidebar_focus" | "focus" => {
                let normalized = match value.trim().to_ascii_lowercase().as_str() {
                    "auto" => "auto",
                    "work" | "plan" | "todos" => "work",
                    "tasks" => "tasks",
                    "agents" | "subagents" | "sub-agents" => "agents",
                    "context" | "session" => "context",
                    "hidden" | "hide" | "closed" | "off" | "none" => "hidden",
                    _ => {
                        anyhow::bail!(
                            "Failed to update setting: invalid sidebar focus '{value}'. Expected: auto, work, tasks, agents, context, hidden."
                        )
                    }
                };
                self.sidebar_focus = normalized.to_string();
            }
            "context_panel" | "context" | "session_panel" => {
                self.context_panel = parse_bool(value)?;
            }
            "cost_currency" | "currency" => {
                let Some(currency) = crate::pricing::CostCurrency::from_setting(value) else {
                    anyhow::bail!(
                        "Failed to update setting: invalid cost currency '{value}'. Expected: usd, cny, rmb, yuan."
                    );
                };
                self.cost_currency = match currency {
                    crate::pricing::CostCurrency::Usd => "usd",
                    crate::pricing::CostCurrency::Cny => "cny",
                }
                .to_string();
            }
            "max_history" | "history" => {
                let max: usize = value.parse().map_err(|_| {
                    anyhow::anyhow!(
                        "Failed to update setting: invalid max history '{value}'. Expected a positive number."
                    )
                })?;
                self.max_input_history = max;
            }
            "default_model" | "model" => {
                let trimmed = value.trim();
                if trimmed.is_empty()
                    || matches!(
                        trimmed.to_ascii_lowercase().as_str(),
                        "none" | "default" | "(default)"
                    )
                {
                    self.default_model = None;
                    return Ok(());
                }

                let Some(model) = normalize_default_model(trimmed) else {
                    anyhow::bail!(
                        "Failed to update setting: invalid model '{value}'. Expected: auto, a DeepSeek model ID (for example deepseek-v4-pro, deepseek-v4-flash), or none/default."
                    );
                };
                self.default_model = Some(model);
            }
            "reasoning_effort" | "effort" => {
                self.reasoning_effort = normalize_reasoning_effort_setting(value)?;
            }
            _ => {
                anyhow::bail!("Failed to update setting: unknown setting '{key}'.");
            }
        }
        Ok(())
    }

    /// Get all settings as a displayable string
    pub fn display(&self, locale: crate::localization::Locale) -> String {
        use crate::localization::{MessageId, tr};
        let mut lines = Vec::new();
        lines.push(tr(locale, MessageId::SettingsTitle).to_string());
        lines.push("─────────────────────────────".to_string());
        lines.push(format!("  auto_compact:       {}", self.auto_compact));
        lines.push(format!("  calm_mode:          {}", self.calm_mode));
        lines.push(format!("  low_motion:         {}", self.low_motion));
        lines.push(format!("  fancy_animations:   {}", self.fancy_animations));
        lines.push(format!("  bracketed_paste:    {}", self.bracketed_paste));
        lines.push(format!(
            "  paste_burst_detect: {}",
            self.paste_burst_detection
        ));
        lines.push(format!("  show_thinking:      {}", self.show_thinking));
        lines.push(format!("  show_tool_details:  {}", self.show_tool_details));
        lines.push(format!("  locale:            {}", self.locale));
        lines.push(format!("  theme:              {}", self.theme));
        lines.push(format!(
            "  background_color:   {}",
            self.background_color.as_deref().unwrap_or("(default)")
        ));
        lines.push(format!("  composer_density:   {}", self.composer_density));
        lines.push(format!("  composer_border:    {}", self.composer_border));
        lines.push(format!("  composer_vim_mode:  {}", self.composer_vim_mode));
        lines.push(format!("  transcript_spacing: {}", self.transcript_spacing));
        lines.push(format!("  status_indicator:   {}", self.status_indicator));
        lines.push(format!(
            "  synchronized_output: {}",
            self.synchronized_output
        ));
        lines.push(format!(
            "  prefer_external_pdftotext: {}",
            self.prefer_external_pdftotext
        ));
        lines.push(format!("  default_mode:       {}", self.default_mode));
        lines.push(format!(
            "  sidebar_width:      {}%",
            self.sidebar_width_percent
        ));
        lines.push(format!("  sidebar_focus:      {}", self.sidebar_focus));
        lines.push(format!("  context_panel:      {}", self.context_panel));
        lines.push(format!("  cost_currency:      {}", self.cost_currency));
        lines.push(format!("  max_history:        {}", self.max_input_history));
        lines.push(format!(
            "  default_model:      {}",
            self.default_model.as_deref().unwrap_or("(default)")
        ));
        lines.push(format!(
            "  reasoning_effort:   {}",
            self.reasoning_effort
                .as_deref()
                .unwrap_or("(config/default)")
        ));
        lines.push(String::new());
        lines.push(format!(
            "{} {}",
            tr(locale, MessageId::SettingsConfigFile),
            Self::path().map_or_else(|_| "(unknown)".to_string(), |p| p.display().to_string())
        ));
        lines.join("\n")
    }

    /// Get available setting keys and their descriptions
    #[allow(dead_code)]
    pub fn available_settings() -> Vec<(&'static str, &'static str)> {
        vec![
            (
                "auto_compact",
                "Auto-compact near the hard context limit: on/off (default off)",
            ),
            ("calm_mode", "Calmer UI defaults: on/off"),
            (
                "low_motion",
                "Streaming pacing: on = typewriter (one char/tick), off = upstream cadence",
            ),
            (
                "fancy_animations",
                "Footer water-spout strip (wave synced to typing speed): on/off",
            ),
            (
                "bracketed_paste",
                "Terminal bracketed-paste mode: on/off (rare to disable)",
            ),
            (
                "paste_burst_detection",
                "Fallback rapid-key paste detection: on/off",
            ),
            ("show_thinking", "Show model thinking: on/off"),
            ("show_tool_details", "Show detailed tool output: on/off"),
            (
                "locale",
                "UI locale and default model language: auto, en, ja, zh-Hans, pt-BR, es-419",
            ),
            (
                "theme",
                "UI theme: system, dark, light, grayscale, catppuccin-mocha, tokyo-night, dracula, gruvbox-dark",
            ),
            (
                "background_color",
                "Main TUI background color: #RRGGBB or default",
            ),
            (
                "composer_density",
                "Composer density: compact, comfortable, spacious",
            ),
            (
                "composer_border",
                "Show a border around the composer input area: on/off",
            ),
            ("composer_vim_mode", "Composer editing mode: normal, vim"),
            (
                "transcript_spacing",
                "Transcript spacing: compact, comfortable, spacious",
            ),
            (
                "status_indicator",
                "Header status indicator next to effort chip: whale, dots, off",
            ),
            (
                "synchronized_output",
                "DEC 2026 synchronized output: auto, on, off (set off if your terminal flickers)",
            ),
            (
                "prefer_external_pdftotext",
                "Route PDF reads through Poppler's pdftotext instead of the bundled pure-Rust extractor: on/off (default off)",
            ),
            ("default_mode", "Default mode: agent, plan, yolo"),
            ("sidebar_width", "Sidebar width percentage: 10-50"),
            (
                "sidebar_focus",
                "Sidebar focus: auto, work, tasks, agents, context, hidden",
            ),
            (
                "context_panel",
                "Show the session context sidebar panel: on/off",
            ),
            ("cost_currency", "Cost display currency: usd, cny"),
            ("max_history", "Max input history entries"),
            (
                "default_model",
                "Default model: auto or any DeepSeek model ID (e.g. deepseek-v4-pro)",
            ),
            (
                "reasoning_effort",
                "Default thinking effort: auto, off, low, medium, high, max, or default",
            ),
        ]
    }

    /// Persist the model for a specific provider.
    pub fn set_model_for_provider(&mut self, provider: &str, model: &str) {
        self.provider_models
            .get_or_insert_with(std::collections::HashMap::new)
            .insert(provider.to_string(), model.to_string());
    }

    /// Resolved boolean for whether the renderer should wrap each frame in
    /// DEC mode 2026 synchronized output. `auto` and `on` enable; `off`
    /// disables. The `auto` → `off` flip for known-bad terminals happens
    /// earlier in [`Self::apply_env_overrides`]; this method only inspects
    /// the final state.
    #[must_use]
    pub fn synchronized_output_enabled(&self) -> bool {
        !self.synchronized_output.eq_ignore_ascii_case("off")
    }
}

fn normalize_default_model(value: &str) -> Option<String> {
    let trimmed = value.trim();
    if trimmed.eq_ignore_ascii_case("auto") {
        Some("auto".to_string())
    } else {
        normalize_model_name(trimmed)
    }
}

fn normalize_reasoning_effort_setting(value: &str) -> Result<Option<String>> {
    let trimmed = value.trim();
    if trimmed.is_empty()
        || matches!(
            trimmed.to_ascii_lowercase().as_str(),
            "default" | "(default)" | "config" | "configured" | "unset"
        )
    {
        return Ok(None);
    }

    let normalized = match trimmed.to_ascii_lowercase().as_str() {
        "off" | "disabled" | "none" | "false" => "off",
        "low" | "minimal" => "low",
        "medium" | "mid" => "medium",
        "high" => "high",
        "auto" | "automatic" => "auto",
        "max" | "maximum" | "xhigh" => "max",
        _ => {
            anyhow::bail!(
                "Failed to update setting: invalid reasoning_effort '{value}'. Expected: auto, off, low, medium, high, max, or default."
            );
        }
    };
    Ok(Some(normalized.to_string()))
}

/// Parse a boolean value from various formats
fn parse_bool(value: &str) -> Result<bool> {
    match value.to_lowercase().as_str() {
        "on" | "true" | "yes" | "1" | "enabled" => Ok(true),
        "off" | "false" | "no" | "0" | "disabled" => Ok(false),
        _ => {
            anyhow::bail!("Failed to parse boolean '{value}': expected on/off, true/false, yes/no.")
        }
    }
}

fn normalize_mode(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "edit" => "agent",
        "normal" => "agent",
        "agent" => "agent",
        "plan" => "plan",
        "yolo" => "yolo",
        _ => value,
    }
}

fn normalize_composer_density(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "compact" | "tight" => "compact",
        "comfortable" | "default" | "normal" => "comfortable",
        "spacious" | "loose" => "spacious",
        _ => value,
    }
}

fn normalize_transcript_spacing(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "compact" | "tight" => "compact",
        "comfortable" | "default" | "normal" => "comfortable",
        "spacious" | "loose" => "spacious",
        _ => value,
    }
}

/// Normalize the `status_indicator` header chip setting. Accepts the
/// canonical names plus common aliases ("none"/"hidden" → "off",
/// "dot" → "dots"). Unknown values fall through unchanged so the parser
/// in `update_setting` can surface a clear error.
fn normalize_status_indicator(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "whale" | "🐳" | "🐋" => "whale",
        "dots" | "dot" => "dots",
        "off" | "none" | "hidden" | "false" => "off",
        _ => value,
    }
}

/// Normalize the `synchronized_output` setting. Accepts the canonical
/// `"auto"` / `"on"` / `"off"` plus the usual truthy/falsey spellings.
/// Unknown values fall through unchanged so the parser in `set` can
/// surface a clear error.
fn normalize_synchronized_output(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "auto" | "default" => "auto",
        "on" | "true" | "yes" | "1" | "enabled" => "on",
        "off" | "false" | "no" | "0" | "disabled" => "off",
        _ => value,
    }
}

fn normalize_settings_theme(value: &str) -> &'static str {
    normalize_theme_name(value).unwrap_or("system")
}

/// Returns `true` when the active terminal is Ptyxis (the new default
/// terminal on Ubuntu 26.04). Used by [`Settings::apply_env_overrides`]
/// to flip `synchronized_output` from `auto` to `off` so DEC mode 2026
/// flicker on Ptyxis 50.x + VTE 0.84.x stops at the source.
///
/// We deliberately keep this narrow:
///
/// - `TERM_PROGRAM` matches `ptyxis` case-insensitively (the value
///   Ptyxis sets when it forwards a process-launch context).
/// - `PTYXIS_VERSION` is set to any non-empty value (the binary's
///   own version probe, present whether or not `TERM_PROGRAM` made it
///   into the child environment).
///
/// Either signal is sufficient. We do *not* trigger on `VTE_VERSION`
/// alone because gnome-terminal 3.58 ships with the same VTE 0.84.x
/// and renders cleanly — broadening the heuristic would regress every
/// gnome-terminal user.
pub fn detected_ptyxis_terminal() -> bool {
    if let Ok(program) = std::env::var("TERM_PROGRAM")
        && program.trim().to_ascii_lowercase().contains("ptyxis")
    {
        return true;
    }
    matches!(std::env::var("PTYXIS_VERSION"), Ok(v) if !v.trim().is_empty())
}

/// Returns `true` for the unmarked Windows console-host path used by plain
/// PowerShell / cmd.exe. Modern Windows terminals set at least one marker that
/// lets us keep the richer rendering path.
pub fn detected_legacy_windows_console_host() -> bool {
    cfg!(windows)
        && legacy_windows_console_host_env([
            std::env::var_os("WT_SESSION").as_deref(),
            std::env::var_os("ConEmuPID").as_deref(),
            std::env::var_os("TERM_PROGRAM").as_deref(),
            std::env::var_os("WEZTERM_EXECUTABLE").as_deref(),
            std::env::var_os("WEZTERM_PANE").as_deref(),
            std::env::var_os("ALACRITTY_WINDOW_ID").as_deref(),
            std::env::var_os("ANSICON").as_deref(),
            std::env::var_os("TERM").as_deref(),
        ])
}

fn legacy_windows_console_host_env(markers: [Option<&std::ffi::OsStr>; 8]) -> bool {
    fn has_value(value: Option<&std::ffi::OsStr>) -> bool {
        value.is_some_and(|v| !v.is_empty())
    }

    markers.into_iter().all(|value| !has_value(value))
}

fn normalize_optional_background_color(value: Option<&str>) -> Option<String> {
    value.and_then(|raw| normalize_background_color_setting(raw).ok().flatten())
}

fn normalize_background_color_setting(value: &str) -> Result<Option<String>> {
    let trimmed = value.trim();
    if trimmed.is_empty()
        || matches!(
            trimmed.to_ascii_lowercase().as_str(),
            "default" | "none" | "reset" | "off"
        )
    {
        return Ok(None);
    }

    normalize_hex_rgb_color(trimmed).map(Some).ok_or_else(|| {
        anyhow::anyhow!(
            "Failed to update setting: invalid background_color '{value}'. Expected #RRGGBB, RRGGBB, or default."
        )
    })
}

fn normalize_sidebar_focus(value: &str) -> &str {
    match value.trim().to_ascii_lowercase().as_str() {
        "work" | "plan" | "todos" => "work",
        "tasks" => "tasks",
        "agents" | "subagents" | "sub-agents" => "agents",
        "context" | "session" => "context",
        "hidden" | "hide" | "closed" | "off" | "none" => "hidden",
        _ => "auto",
    }
}

/// Resolve an environment variable as a boolean. Recognises the
/// common truthy spellings (`1`, `true`, `yes`, `on`) case-
/// insensitively. Used by [`Settings::apply_env_overrides`] for
/// platform a11y signals like `NO_ANIMATIONS`.
fn env_truthy(name: &str) -> bool {
    match std::env::var(name) {
        Ok(v) => matches!(
            v.trim().to_ascii_lowercase().as_str(),
            "1" | "true" | "yes" | "on"
        ),
        Err(_) => false,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn default_settings_disable_auto_compact_to_protect_v4_prefix_cache() {
        let settings = Settings::default();
        // v0.8.11: default is `false` to stop the engine from routinely
        // rewriting the prompt prefix, which breaks V4's prefix-cache
        // discount. The explicit `/compact` command and the
        // `auto_compact = on` opt-in stay available; the default is
        // flipped so the cache-friendly path is the one users get
        // without configuring anything (#664).
        assert!(!settings.auto_compact);
    }

    #[test]
    fn auto_compact_remains_explicitly_configurable() {
        let mut settings = Settings::default();
        settings.set("auto_compact", "on").expect("enable");
        assert!(settings.auto_compact);
        settings.set("auto_compact", "off").expect("disable");
        assert!(!settings.auto_compact);
    }

    #[test]
    fn default_settings_show_footer_water_strip() {
        let settings = Settings::default();
        assert!(settings.fancy_animations);
    }

    #[test]
    fn reasoning_effort_setting_normalizes_and_clears() {
        let mut settings = Settings::default();
        settings
            .set("reasoning_effort", "xhigh")
            .expect("normalize xhigh");
        assert_eq!(settings.reasoning_effort.as_deref(), Some("max"));
        settings
            .set("reasoning_effort", "default")
            .expect("clear effort");
        assert!(settings.reasoning_effort.is_none());
    }

    #[test]
    fn paste_burst_detection_is_configurable_independent_of_bracketed_paste() {
        let mut settings = Settings::default();
        assert!(settings.bracketed_paste);
        assert!(settings.paste_burst_detection);

        settings
            .set("paste_burst_detection", "off")
            .expect("disable paste burst fallback");
        assert!(settings.bracketed_paste);
        assert!(!settings.paste_burst_detection);

        settings
            .set("bracketed_paste", "off")
            .expect("disable bracketed paste");
        assert!(!settings.bracketed_paste);
        assert!(!settings.paste_burst_detection);
    }

    #[test]
    fn locale_normalizes_supported_values_and_rejects_unknowns() {
        let mut settings = Settings::default();
        settings.set("locale", "ja_JP.UTF-8").expect("set ja");
        assert_eq!(settings.locale, "ja");

        settings.set("language", "pt-PT").expect("set pt fallback");
        assert_eq!(settings.locale, "pt-BR");

        let err = settings
            .set("locale", "ar")
            .expect_err("Arabic is planned, not shipped");
        assert!(err.to_string().contains("invalid locale"));
    }

    #[test]
    fn theme_normalizes_supported_values_and_rejects_unknowns() {
        let mut settings = Settings::default();
        assert_eq!(settings.theme, "system");

        settings.set("theme", "grayscale").expect("set grayscale");
        assert_eq!(settings.theme, "grayscale");

        settings.set("ui_theme", "black-white").expect("set alias");
        assert_eq!(settings.theme, "grayscale");

        settings.set("theme", "whale").expect("set dark alias");
        assert_eq!(settings.theme, "dark");

        settings
            .set("theme", "tokyonight")
            .expect("set community theme alias");
        assert_eq!(settings.theme, "tokyo-night");

        let err = settings
            .set("theme", "solarized")
            .expect_err("unknown theme should fail");
        assert!(err.to_string().contains("invalid theme"));
    }

    #[test]
    fn background_color_normalizes_hex_and_accepts_default() {
        let mut settings = Settings::default();
        settings
            .set("background_color", "#1A1b26")
            .expect("set custom background");
        assert_eq!(settings.background_color.as_deref(), Some("#1a1b26"));

        settings
            .set("background", "default")
            .expect("reset custom background");
        assert_eq!(settings.background_color, None);
    }

    #[test]
    fn background_color_rejects_invalid_hex() {
        let mut settings = Settings::default();
        let err = settings
            .set("background_color", "#123")
            .expect_err("short hex should fail");
        assert!(err.to_string().contains("invalid background_color"));
    }

    #[test]
    fn cost_currency_normalizes_yuan_aliases_and_rejects_unknowns() {
        let mut settings = Settings::default();
        assert_eq!(settings.cost_currency, "usd");

        settings.set("cost_currency", "yuan").expect("set yuan");
        assert_eq!(settings.cost_currency, "cny");

        settings.set("currency", "rmb").expect("set rmb");
        assert_eq!(settings.cost_currency, "cny");

        let err = settings
            .set("cost_currency", "eur")
            .expect_err("unsupported currency");
        assert!(err.to_string().contains("invalid cost currency"));
    }

    #[test]
    fn sidebar_focus_accepts_work_values_and_legacy_aliases() {
        let mut settings = Settings::default();

        settings.set("sidebar_focus", "work").expect("set work");
        assert_eq!(settings.sidebar_focus, "work");

        settings.set("focus", "plan").expect("legacy plan alias");
        assert_eq!(settings.sidebar_focus, "work");

        settings.set("focus", "todos").expect("legacy todos alias");
        assert_eq!(settings.sidebar_focus, "work");

        settings.set("focus", "context").expect("context focus");
        assert_eq!(settings.sidebar_focus, "context");

        settings.set("focus", "hidden").expect("hidden focus");
        assert_eq!(settings.sidebar_focus, "hidden");

        settings.set("focus", "off").expect("off alias");
        assert_eq!(settings.sidebar_focus, "hidden");

        let err = settings
            .set("sidebar_focus", "classic")
            .expect_err("classic is not a supported public focus");
        assert!(err.to_string().contains("invalid sidebar focus"));
    }

    #[test]
    fn context_panel_is_configurable() {
        let mut settings = Settings::default();
        assert!(!settings.context_panel);

        settings
            .set("context_panel", "on")
            .expect("enable context panel");
        assert!(settings.context_panel);

        settings
            .set("session_panel", "off")
            .expect("disable context panel via alias");
        assert!(!settings.context_panel);
    }

    #[test]
    fn display_localizes_header_and_config_file_label() {
        let settings = Settings::default();
        let en = settings.display(crate::localization::Locale::En);
        assert!(en.contains("Settings:"), "english header missing:\n{en}");
        assert!(
            en.contains("Config file:"),
            "english config label missing:\n{en}"
        );

        let zh = settings.display(crate::localization::Locale::ZhHans);
        assert!(zh.contains("设置"), "chinese header missing:\n{zh}");
        assert!(
            zh.contains("配置文件"),
            "chinese config label missing:\n{zh}"
        );
    }

    /// Tests that mutate process-global `NO_ANIMATIONS` serialise
    /// through this guard so the cargo parallel runner doesn't
    /// observe interleaved overrides. Uses the process-wide test env
    /// lock so this serializes with the TERM_PROGRAM tests too —
    /// otherwise a `NO_ANIMATIONS=1` leak from this test family can
    /// flip a concurrent `TERM_PROGRAM=iTerm` test's `low_motion`
    /// assertion through the shared `apply_env_overrides` path.
    fn no_animations_test_guard() -> std::sync::MutexGuard<'static, ()> {
        crate::test_support::lock_test_env()
    }

    #[test]
    fn no_animations_env_forces_low_motion_on() {
        let _g = no_animations_test_guard();
        // SAFETY: tests in this group serialise through the guard.
        unsafe {
            std::env::set_var("NO_ANIMATIONS", "1");
        }
        let mut settings = Settings::default();
        assert!(!settings.low_motion, "default is animated");
        assert!(settings.fancy_animations, "default shows the water strip");
        settings.apply_env_overrides();
        assert!(settings.low_motion, "NO_ANIMATIONS=1 forces low_motion");
        assert!(
            !settings.fancy_animations,
            "NO_ANIMATIONS=1 keeps fancy off"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("NO_ANIMATIONS");
        }
    }

    #[test]
    fn no_animations_env_overrides_user_opt_in() {
        let _g = no_animations_test_guard();
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("NO_ANIMATIONS", "true");
        }
        // User had explicitly opted into fancy animations on disk.
        let mut settings = Settings {
            fancy_animations: true,
            ..Settings::default()
        };
        settings.apply_env_overrides();
        assert!(
            !settings.fancy_animations,
            "platform NO_ANIMATIONS overrides user-opt-in fancy_animations"
        );
        assert!(settings.low_motion);
        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("NO_ANIMATIONS");
        }
    }

    #[test]
    fn no_animations_env_recognises_truthy_spellings_only() {
        let _g = no_animations_test_guard();
        let prev_wt_session = std::env::var_os("WT_SESSION");
        let prev_tmux = std::env::var_os("TMUX");
        let prev_sty = std::env::var_os("STY");
        // The test is about NO_ANIMATIONS only. On Windows CI, an unmarked
        // console host now independently enables low_motion, so mark the host
        // as non-legacy while checking falsy spellings.
        // Clear multiplexer markers for the same reason: they also force
        // low_motion independently of NO_ANIMATIONS.
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::remove_var("TMUX");
            std::env::remove_var("STY");
        }
        #[cfg(windows)]
        unsafe {
            std::env::set_var("WT_SESSION", "test");
        }
        for truthy in ["1", "true", "True", "YES", "on"] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::set_var("NO_ANIMATIONS", truthy);
            }
            let mut s = Settings::default();
            s.apply_env_overrides();
            assert!(s.low_motion, "{truthy:?} should be truthy");
        }
        for falsy in ["0", "false", "no", "off", ""] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::set_var("NO_ANIMATIONS", falsy);
            }
            let mut s = Settings::default();
            s.apply_env_overrides();
            assert!(!s.low_motion, "{falsy:?} should be falsy");
        }
        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("NO_ANIMATIONS");
            match prev_wt_session {
                Some(v) => std::env::set_var("WT_SESSION", v),
                None => std::env::remove_var("WT_SESSION"),
            }
            match prev_tmux {
                Some(v) => std::env::set_var("TMUX", v),
                None => std::env::remove_var("TMUX"),
            }
            match prev_sty {
                Some(v) => std::env::set_var("STY", v),
                None => std::env::remove_var("STY"),
            }
        }
    }

    /// Serialise tests that mutate `TERM_PROGRAM` through this guard.
    /// Uses the process-wide test env lock so this serializes not just
    /// with itself but with every other env-mutating test in the suite
    /// — otherwise a concurrent test that calls `Settings::default()`
    /// can read whatever value our two `set_var`s have raced into the
    /// env at that instant.
    fn term_program_test_guard() -> std::sync::MutexGuard<'static, ()> {
        crate::test_support::lock_test_env()
    }

    #[test]
    fn vscode_term_program_forces_low_motion_on() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "vscode");
        }
        let mut settings = Settings::default();
        assert!(!settings.low_motion, "default is animated");
        settings.apply_env_overrides();
        assert!(
            settings.low_motion,
            "TERM_PROGRAM=vscode must enable low_motion to prevent flickering (#1356)"
        );
        assert!(
            !settings.fancy_animations,
            "TERM_PROGRAM=vscode must disable fancy_animations"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn ghostty_term_program_forces_low_motion_on() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "ghostty");
        }
        let mut settings = Settings::default();
        assert!(!settings.low_motion, "default is animated");
        settings.apply_env_overrides();
        assert!(
            settings.low_motion,
            "TERM_PROGRAM=ghostty must enable low_motion to prevent flickering (#1445)"
        );
        assert!(
            !settings.fancy_animations,
            "TERM_PROGRAM=ghostty must disable fancy_animations"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn non_vscode_term_program_does_not_force_low_motion() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        let prev_ssh_client = std::env::var_os("SSH_CLIENT");
        let prev_ssh_tty = std::env::var_os("SSH_TTY");
        let prev_tilix_id = std::env::var_os("TILIX_ID");
        let prev_terminator_uuid = std::env::var_os("TERMINATOR_UUID");
        let prev_tmux = std::env::var_os("TMUX");
        let prev_sty = std::env::var_os("STY");
        // SAFETY: serialised by the guard. Clear SSH_* so a real
        // SSH session running the test suite doesn't make this
        // assertion trivially fail — the SSH path is exercised
        // separately by `ssh_session_forces_low_motion_on`.
        unsafe {
            std::env::remove_var("SSH_CLIENT");
            std::env::remove_var("SSH_TTY");
            std::env::remove_var("TILIX_ID");
            std::env::remove_var("TERMINATOR_UUID");
            std::env::remove_var("TMUX");
            std::env::remove_var("STY");
        }
        for program in ["iTerm.app", "Apple_Terminal", "WezTerm", "xterm-256color"] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::set_var("TERM_PROGRAM", program);
            }
            let mut s = Settings::default();
            s.apply_env_overrides();
            assert!(
                !s.low_motion,
                "TERM_PROGRAM={program:?} should not force low_motion"
            );
        }
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
            if let Some(v) = prev_ssh_client {
                std::env::set_var("SSH_CLIENT", v);
            }
            if let Some(v) = prev_ssh_tty {
                std::env::set_var("SSH_TTY", v);
            }
            if let Some(v) = prev_tilix_id {
                std::env::set_var("TILIX_ID", v);
            }
            if let Some(v) = prev_terminator_uuid {
                std::env::set_var("TERMINATOR_UUID", v);
            }
            if let Some(v) = prev_tmux {
                std::env::set_var("TMUX", v);
            }
            if let Some(v) = prev_sty {
                std::env::set_var("STY", v);
            }
        }
    }

    #[test]
    fn tilix_and_terminator_env_force_low_motion_on() {
        let _g = term_program_test_guard();
        let prev_term_program = std::env::var_os("TERM_PROGRAM");
        let prev_tilix_id = std::env::var_os("TILIX_ID");
        let prev_terminator_uuid = std::env::var_os("TERMINATOR_UUID");

        for (var, val) in [
            ("TILIX_ID", "d5b5b5d6-tilix-session"),
            ("TERMINATOR_UUID", "urn:uuid:terminator-session"),
        ] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::remove_var("TERM_PROGRAM");
                std::env::remove_var("TILIX_ID");
                std::env::remove_var("TERMINATOR_UUID");
                std::env::set_var(var, val);
            }
            let mut settings = Settings::default();
            assert!(!settings.low_motion, "default is animated");
            settings.apply_env_overrides();
            assert!(
                settings.low_motion,
                "{var} must enable low_motion to prevent VTE flicker (#1470)"
            );
            assert!(
                !settings.fancy_animations,
                "{var} must disable fancy_animations"
            );
        }

        // SAFETY: cleanup under the guard.
        unsafe {
            match prev_term_program {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
            match prev_tilix_id {
                Some(v) => std::env::set_var("TILIX_ID", v),
                None => std::env::remove_var("TILIX_ID"),
            }
            match prev_terminator_uuid {
                Some(v) => std::env::set_var("TERMINATOR_UUID", v),
                None => std::env::remove_var("TERMINATOR_UUID"),
            }
        }
    }

    #[test]
    fn termius_term_program_forces_low_motion_on() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "Termius");
        }
        let mut settings = Settings::default();
        assert!(!settings.low_motion, "default is animated");
        settings.apply_env_overrides();
        assert!(
            settings.low_motion,
            "TERM_PROGRAM=Termius must enable low_motion to prevent flickering (#1433)"
        );
        assert!(
            !settings.fancy_animations,
            "TERM_PROGRAM=Termius must disable fancy_animations"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn legacy_windows_console_host_detects_unmarked_shell() {
        assert!(legacy_windows_console_host_env([
            None, None, None, None, None, None, None, None
        ]));
    }

    #[test]
    fn legacy_windows_console_host_excludes_modern_terminal_markers() {
        use std::ffi::OsStr;

        let marker = Some(OsStr::new("1"));
        assert!(!legacy_windows_console_host_env([
            marker, None, None, None, None, None, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, marker, None, None, None, None, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, marker, None, None, None, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, None, marker, None, None, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, None, None, marker, None, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, None, None, None, marker, None, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, None, None, None, None, marker, None
        ]));
        assert!(!legacy_windows_console_host_env([
            None, None, None, None, None, None, None, marker
        ]));
    }

    #[cfg(windows)]
    #[test]
    fn unmarked_windows_console_forces_calm_rendering() {
        let _g = term_program_test_guard();
        let vars = [
            "WT_SESSION",
            "ConEmuPID",
            "TERM_PROGRAM",
            "WEZTERM_EXECUTABLE",
            "WEZTERM_PANE",
            "ALACRITTY_WINDOW_ID",
            "ANSICON",
            "TERM",
            "SSH_CLIENT",
            "SSH_TTY",
            "NO_ANIMATIONS",
            "PTYXIS_VERSION",
        ];
        let prev: Vec<_> = vars
            .iter()
            .map(|name| (*name, std::env::var_os(name)))
            .collect();

        // SAFETY: serialised by the guard.
        unsafe {
            for name in vars {
                std::env::remove_var(name);
            }
        }

        let mut settings = Settings::default();
        assert!(!settings.low_motion, "default is animated");
        assert!(settings.fancy_animations, "default shows the water strip");
        assert_eq!(settings.synchronized_output, "auto");
        settings.apply_env_overrides();
        assert!(settings.low_motion);
        assert!(!settings.fancy_animations);
        assert_eq!(settings.synchronized_output, "off");

        // SAFETY: cleanup under the guard.
        unsafe {
            for (name, value) in prev {
                match value {
                    Some(value) => std::env::set_var(name, value),
                    None => std::env::remove_var(name),
                }
            }
        }
    }

    #[test]
    fn ssh_session_forces_low_motion_on() {
        let _g = term_program_test_guard();
        let prev_client = std::env::var_os("SSH_CLIENT");
        let prev_tty = std::env::var_os("SSH_TTY");
        let prev_term_program = std::env::var_os("TERM_PROGRAM");
        for (var, val) in [
            ("SSH_CLIENT", "192.168.1.100 50000 22"),
            ("SSH_TTY", "/dev/pts/0"),
        ] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::remove_var("SSH_CLIENT");
                std::env::remove_var("SSH_TTY");
                // Clear TERM_PROGRAM so the test isolates the SSH signal
                // — otherwise a leaked `TERM_PROGRAM=vscode` from a
                // concurrent test would already have forced low_motion
                // and the SSH-only assertion below would be a tautology.
                std::env::remove_var("TERM_PROGRAM");
                std::env::set_var(var, val);
            }
            let mut s = Settings::default();
            s.apply_env_overrides();
            assert!(
                s.low_motion,
                "{var}={val:?} must enable low_motion to prevent flickering in SSH sessions (#1433)"
            );
            assert!(
                !s.fancy_animations,
                "{var}={val:?} must disable fancy_animations in SSH sessions (#1433)"
            );
        }
        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("SSH_CLIENT");
            std::env::remove_var("SSH_TTY");
            if let Some(v) = prev_client {
                std::env::set_var("SSH_CLIENT", v);
            }
            if let Some(v) = prev_tty {
                std::env::set_var("SSH_TTY", v);
            }
            match prev_term_program {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn terminal_multiplexer_env_forces_low_motion_on() {
        let _g = term_program_test_guard();
        let vars = [
            "TMUX",
            "STY",
            "TERM_PROGRAM",
            "SSH_CLIENT",
            "SSH_TTY",
            "TILIX_ID",
            "TERMINATOR_UUID",
            "NO_ANIMATIONS",
        ];
        let prev: Vec<_> = vars
            .iter()
            .map(|name| (*name, std::env::var_os(name)))
            .collect();

        for (var, val) in [
            ("TMUX", "/tmp/tmux-501/default,1234,0"),
            ("STY", "1234.pts-0.host"),
        ] {
            // SAFETY: serialised by the guard.
            unsafe {
                for name in vars {
                    std::env::remove_var(name);
                }
                std::env::set_var(var, val);
            }
            let mut settings = Settings::default();
            assert!(!settings.low_motion, "default is animated");
            assert!(settings.fancy_animations, "default shows the water strip");
            settings.apply_env_overrides();
            assert!(
                settings.low_motion,
                "{var}={val:?} must enable low_motion under terminal multiplexers (#1925)"
            );
            assert!(
                !settings.fancy_animations,
                "{var}={val:?} must disable fancy_animations under terminal multiplexers (#1925)"
            );
        }

        // SAFETY: cleanup under the guard.
        unsafe {
            for (name, value) in prev {
                match value {
                    Some(value) => std::env::set_var(name, value),
                    None => std::env::remove_var(name),
                }
            }
        }
    }

    // ────────────────────────────────────────────────────────────────────────
    // synchronized_output / Ptyxis flicker detection
    // ────────────────────────────────────────────────────────────────────────

    #[test]
    fn synchronized_output_defaults_to_auto_and_resolves_to_enabled() {
        let s = Settings::default();
        assert_eq!(s.synchronized_output, "auto");
        assert!(
            s.synchronized_output_enabled(),
            "auto must keep DEC 2026 on so terminals that support it stay tear-free"
        );
    }

    #[test]
    fn synchronized_output_off_disables_dec_2026() {
        let s = Settings {
            synchronized_output: "off".to_string(),
            ..Settings::default()
        };
        assert!(!s.synchronized_output_enabled());
    }

    #[test]
    fn synchronized_output_on_keeps_dec_2026_enabled() {
        let s = Settings {
            synchronized_output: "on".to_string(),
            ..Settings::default()
        };
        assert!(s.synchronized_output_enabled());
    }

    #[test]
    fn synchronized_output_set_command_accepts_aliases() {
        let mut s = Settings::default();
        for value in ["auto", "AUTO", "default"] {
            s.set("synchronized_output", value).expect("valid");
            assert_eq!(s.synchronized_output, "auto");
        }
        for value in ["on", "true", "yes", "1", "ENABLED"] {
            s.set("sync_output", value).expect("valid");
            assert_eq!(s.synchronized_output, "on");
        }
        for value in ["off", "false", "no", "0", "DISABLED"] {
            s.set("sync", value).expect("valid");
            assert_eq!(s.synchronized_output, "off");
        }
        let err = s
            .set("synchronized_output", "maybe")
            .expect_err("unknown value rejected");
        assert!(
            err.to_string().contains("synchronized_output"),
            "error names the offending key: {err}"
        );
    }

    #[test]
    fn ptyxis_term_program_flips_synchronized_output_off() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        let prev_ptyxis = std::env::var_os("PTYXIS_VERSION");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "Ptyxis");
            std::env::remove_var("PTYXIS_VERSION");
        }
        let mut s = Settings::default();
        assert_eq!(s.synchronized_output, "auto");
        s.apply_env_overrides();
        assert_eq!(
            s.synchronized_output, "off",
            "Ptyxis 50.x mishandles DEC 2026 — auto must flip to off so VTE 0.84 stops flickering"
        );
        assert!(
            !s.synchronized_output_enabled(),
            "resolved boolean must agree with stored string"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
            match prev_ptyxis {
                Some(v) => std::env::set_var("PTYXIS_VERSION", v),
                None => std::env::remove_var("PTYXIS_VERSION"),
            }
        }
    }

    #[test]
    fn ptyxis_version_env_alone_flips_synchronized_output_off() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        let prev_ptyxis = std::env::var_os("PTYXIS_VERSION");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::remove_var("TERM_PROGRAM");
            std::env::set_var("PTYXIS_VERSION", "50.1");
        }
        let mut s = Settings::default();
        s.apply_env_overrides();
        assert_eq!(
            s.synchronized_output, "off",
            "PTYXIS_VERSION alone is sufficient — Ptyxis sets this even when TERM_PROGRAM isn't propagated"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
            match prev_ptyxis {
                Some(v) => std::env::set_var("PTYXIS_VERSION", v),
                None => std::env::remove_var("PTYXIS_VERSION"),
            }
        }
    }

    #[test]
    fn ptyxis_does_not_override_user_explicit_on() {
        // Users who set `synchronized_output = "on"` (e.g. to confirm a
        // Ptyxis upgrade fixed it) must keep DEC 2026 even on Ptyxis.
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "ptyxis");
        }
        let mut s = Settings {
            synchronized_output: "on".to_string(),
            ..Settings::default()
        };
        s.apply_env_overrides();
        assert_eq!(
            s.synchronized_output, "on",
            "explicit user override must beat the Ptyxis env heuristic"
        );
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn ptyxis_does_not_override_user_explicit_off() {
        // A user with `synchronized_output = "off"` on a non-Ptyxis
        // terminal stays off after env detection (no-op flip).
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        // SAFETY: serialised by the guard.
        unsafe {
            std::env::set_var("TERM_PROGRAM", "xterm-256color");
        }
        let mut s = Settings {
            synchronized_output: "off".to_string(),
            ..Settings::default()
        };
        s.apply_env_overrides();
        assert_eq!(s.synchronized_output, "off");
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
        }
    }

    #[test]
    fn non_ptyxis_term_programs_keep_synchronized_output_auto() {
        let _g = term_program_test_guard();
        let prev = std::env::var_os("TERM_PROGRAM");
        let prev_ptyxis = std::env::var_os("PTYXIS_VERSION");
        // SAFETY: clean slate so non-Ptyxis programs don't see a leaked
        // PTYXIS_VERSION from another test.
        unsafe {
            std::env::remove_var("PTYXIS_VERSION");
        }
        for program in [
            "iTerm.app",
            "Apple_Terminal",
            "WezTerm",
            "xterm-256color",
            "gnome-terminal-server",
            // The Ghostty / VS Code paths force low_motion but must NOT
            // disable DEC 2026 — they handle synchronized output cleanly.
            "ghostty",
            "vscode",
        ] {
            // SAFETY: serialised by the guard.
            unsafe {
                std::env::set_var("TERM_PROGRAM", program);
            }
            let mut s = Settings::default();
            s.apply_env_overrides();
            assert_eq!(
                s.synchronized_output, "auto",
                "TERM_PROGRAM={program:?} must not opt out of DEC 2026"
            );
            assert!(
                s.synchronized_output_enabled(),
                "resolved boolean for {program:?} must stay enabled"
            );
        }
        // SAFETY: cleanup under the guard.
        unsafe {
            match prev {
                Some(v) => std::env::set_var("TERM_PROGRAM", v),
                None => std::env::remove_var("TERM_PROGRAM"),
            }
            match prev_ptyxis {
                Some(v) => std::env::set_var("PTYXIS_VERSION", v),
                None => std::env::remove_var("PTYXIS_VERSION"),
            }
        }
    }

    // ────────────────────────────────────────────────────────────────────────
    // TuiPrefs tests
    // ────────────────────────────────────────────────────────────────────────

    /// Serialise tests that mutate `DEEPSEEK_CONFIG_PATH` through this guard
    /// so the parallel test runner doesn't observe interleaved env values.
    fn config_path_test_guard() -> std::sync::MutexGuard<'static, ()> {
        crate::test_support::lock_test_env()
    }

    #[test]
    fn tui_prefs_defaults_are_dark_theme_zero_font() {
        let prefs = TuiPrefs::default();
        assert_eq!(prefs.theme, "dark");
        assert_eq!(prefs.font_size, 0);
        assert!(prefs.keybinds.submit.is_none());
        assert!(prefs.keybinds.new_line.is_none());
    }

    #[test]
    fn tui_prefs_validate_accepts_known_themes() {
        for theme in [
            "dark",
            "light",
            "system",
            "grayscale",
            "catppuccin-mocha",
            "tokyo-night",
            "dracula",
            "gruvbox-dark",
        ] {
            let mut prefs = TuiPrefs {
                theme: theme.to_string(),
                ..TuiPrefs::default()
            };
            prefs
                .validate()
                .unwrap_or_else(|e| panic!("validate({theme}) failed: {e}"));
            assert_eq!(prefs.theme, theme);
        }
    }

    #[test]
    fn tui_prefs_validate_normalises_theme_case() {
        let mut prefs = TuiPrefs {
            theme: "MONO".to_string(),
            ..TuiPrefs::default()
        };
        prefs
            .validate()
            .expect("MONO should normalise to grayscale");
        assert_eq!(prefs.theme, "grayscale");
    }

    #[test]
    fn tui_prefs_validate_rejects_unknown_theme() {
        let mut prefs = TuiPrefs {
            theme: "solarized".to_string(),
            ..TuiPrefs::default()
        };
        let err = prefs
            .validate()
            .expect_err("solarized is not a valid theme");
        assert!(err.to_string().contains("Invalid tui.toml theme"));
        assert!(
            err.to_string()
                .contains("expected system, dark, light, grayscale")
        );
    }

    #[test]
    fn tui_prefs_round_trips_through_toml() {
        let prefs = TuiPrefs {
            theme: "light".to_string(),
            font_size: 16,
            keybinds: KeybindPrefs {
                submit: Some("ctrl+enter".to_string()),
                new_line: Some("enter".to_string()),
                command_palette: None,
                cancel: None,
                toggle_sidebar: None,
            },
        };
        let serialised = toml::to_string_pretty(&prefs).expect("serialise");
        let de: TuiPrefs = toml::from_str(&serialised).expect("deserialise");
        assert_eq!(de.theme, "light");
        assert_eq!(de.font_size, 16);
        assert_eq!(de.keybinds.submit.as_deref(), Some("ctrl+enter"));
        assert_eq!(de.keybinds.new_line.as_deref(), Some("enter"));
        assert!(de.keybinds.command_palette.is_none());
    }

    #[test]
    fn tui_prefs_load_returns_defaults_when_file_absent() {
        let _g = config_path_test_guard();
        // Point config path at a non-existent location so tui.toml is absent.
        let tmp = std::env::temp_dir().join("dst_tui_prefs_absent_test");
        std::fs::create_dir_all(&tmp).unwrap();
        // SAFETY: test-only env mutation guarded by config_path_test_guard.
        unsafe {
            std::env::set_var(
                "DEEPSEEK_CONFIG_PATH",
                tmp.join("config.toml").to_str().unwrap(),
            );
        }
        let prefs = TuiPrefs::load().expect("load should not fail when file absent");
        assert_eq!(prefs.theme, "dark", "should fall back to default theme");
        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("DEEPSEEK_CONFIG_PATH");
        }
        let _ = std::fs::remove_dir_all(&tmp);
    }

    #[test]
    fn tui_prefs_save_and_load_round_trip() {
        let _g = config_path_test_guard();
        let tmp = std::env::temp_dir().join("dst_tui_prefs_save_test");
        std::fs::create_dir_all(&tmp).unwrap();
        // SAFETY: test-only env mutation guarded by config_path_test_guard.
        unsafe {
            std::env::set_var(
                "DEEPSEEK_CONFIG_PATH",
                tmp.join("config.toml").to_str().unwrap(),
            );
        }

        let prefs = TuiPrefs {
            theme: "light".to_string(),
            font_size: 14,
            keybinds: KeybindPrefs {
                submit: Some("ctrl+enter".to_string()),
                ..KeybindPrefs::default()
            },
        };
        prefs.save().expect("save should succeed");

        let loaded = TuiPrefs::load().expect("load after save");
        assert_eq!(loaded.theme, "light");
        assert_eq!(loaded.font_size, 14);
        assert_eq!(loaded.keybinds.submit.as_deref(), Some("ctrl+enter"));

        // SAFETY: cleanup under the guard.
        unsafe {
            std::env::remove_var("DEEPSEEK_CONFIG_PATH");
        }
        let _ = std::fs::remove_dir_all(&tmp);
    }

    #[test]
    fn tui_prefs_path_uses_home_deepseek_subdir_by_default() {
        let _g = config_path_test_guard();
        // Without DEEPSEEK_CONFIG_PATH the path should end with
        // .deepseek/tui.toml relative to the home directory.
        // We skip this check if home_dir() is unavailable (CI without HOME).
        if let Some(home) = dirs::home_dir() {
            let expected = home.join(".deepseek").join("tui.toml");
            // Only compare when no env override is active.
            if std::env::var("DEEPSEEK_CONFIG_PATH").is_err() {
                let got = TuiPrefs::path().expect("path should resolve");
                assert_eq!(got, expected);
            }
        }
    }
}
