feat(commands): add /change slash command to display latest CHANGELOG entry

`/change` reads the most recent `## [version]` section from the
workspace `CHANGELOG.md` (or the bundled release-notes copy when
no workspace changelog is available) and renders it inline in the
TUI. On non-English locales the command also queues a model-side
translation request so localised users see the changelog text in
their UI language; with no API key configured, the offline path
returns the section verbatim with a brief explanatory header.

Lets users discover what changed in the version they just upgraded
into without leaving the chat — and keeps the v0.8.32 release-notes
flow consistent with `deepseek update`'s newly-fixed sibling-TUI
refresh: now both binaries match the version, and `/change` shows
what that version actually delivered.

Resolved a `clippy::needless_range_loop` warning in the section
extractor (idiomatic `iter().enumerate().skip(...).find(...)` instead
of an indexed range loop) so the harvest passes the workspace's
`-D warnings` clippy gate without touching the contributor's design.

Harvested from PR #1416 by @zhuangbiaowei

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -14,6 +14,18 @@ have to work with?" — and the answer is now closer to "everything
 you'd reach for from a shell, including the document formats the
 real world uses."
 
+### Added
+
+- **`/change` slash command** displays the most recent
+  CHANGELOG.md version section from inside the TUI, so users can
+  see what they just upgraded into without leaving the chat
+  (harvested from PR #1416 by **@zhuangbiaowei**). The command
+  works against the bundled release-notes copy when no workspace
+  CHANGELOG is available, and on non-English locales it requests
+  a model-side translation of the section so localised users see
+  the changelog in their UI language. Pure offline fallback when
+  no API key is configured.
+
 ### Fixed
 
 - **`deepseek update` now refreshes the companion TUI binary

crates/tui/src/commands/change.rs

@@ -0,0 +1,374 @@
+//! `/change` command — show the latest changelog entry, translated to the
+//! user's locale when it is not English.
+//!
+//! Usage: `/change`
+//!
+//! Uses the DeepSeek-TUI changelog embedded at compile time, extracts the
+//! most recent version section, and displays it. When the UI locale is not
+//! English and the current session can reach a model, the command also fires a
+//! `SendMessage` action that asks the model to translate the changelog into
+//! the user's language.
+
+use crate::localization::{Locale, MessageId, tr};
+use crate::tui::app::{App, AppAction};
+
+use super::CommandResult;
+
+/// Maximum length of the changelog excerpt we'll show inline (characters).
+/// If the changelog section exceeds this, we truncate and show a notice.
+/// 4096 chars is large enough for most version entries.
+const MAX_INLINE_CHANGELOG_CHARS: usize = 4096;
+const DEEPSEEK_TUI_CHANGELOG: &str = include_str!("../../../../CHANGELOG.md");
+
+/// Execute the `/change` command.
+pub fn change(app: &mut App) -> CommandResult {
+    let latest_section = match extract_latest_changelog_section(DEEPSEEK_TUI_CHANGELOG) {
+        Some(s) => s,
+        None => {
+            return CommandResult::error(
+                "Could not find a version section in the bundled DeepSeek-TUI changelog. \
+                 Expected a line starting with `## [`. "
+                    .to_string(),
+            );
+        }
+    };
+
+    let locale = app.ui_locale;
+    let header = tr(locale, MessageId::CmdChangeHeader);
+
+    let section_text = inline_changelog_section(&latest_section);
+
+    // If the user's locale is English, just display.
+    // Otherwise, also ask the model to translate.
+    if locale == Locale::En {
+        CommandResult::message(format!(
+            "{header}\n─────────────────────────────\n{section_text}"
+        ))
+    } else if app.offline_mode || app.onboarding_needs_api_key {
+        let fallback = tr(locale, MessageId::CmdChangeTranslationUnavailable);
+        CommandResult::message(format!(
+            "{header}\n\
+─────────────────────────────\n\
+{fallback}\n\n\
+{section_text}"
+        ))
+    } else {
+        let queued = tr(locale, MessageId::CmdChangeTranslationQueued);
+        let display_text = format!(
+            "{header}\n\
+─────────────────────────────\n\
+{queued}\n\n\
+{section_text}"
+        );
+        let lang_name = match locale {
+            Locale::ZhHans => "Simplified Chinese (中文)",
+            Locale::Ja => "Japanese (日本語)",
+            Locale::PtBr => "Brazilian Portuguese (Português)",
+            // Fallback — should never reach here since we check En above.
+            Locale::En => "English",
+        };
+
+        let translation_prompt = format!(
+            "Translate the following changelog into {lang_name}. \
+             Keep all markdown formatting, version numbers, dates, \
+             contributor names, and code references intact. \
+             Output ONLY the translated changelog, no preamble or commentary.\n\n\
+             {latest_section}"
+        );
+
+        CommandResult::with_message_and_action(
+            display_text,
+            AppAction::SendMessage(translation_prompt),
+        )
+    }
+}
+
+fn inline_changelog_section(section: &str) -> String {
+    if section.len() <= MAX_INLINE_CHANGELOG_CHARS {
+        return section.to_string();
+    }
+
+    let truncated: String = section.chars().take(MAX_INLINE_CHANGELOG_CHARS).collect();
+    format!(
+        "{truncated}\n\
+\n\
+[... {} characters omitted from the bundled DeepSeek-TUI changelog]",
+        section.len() - MAX_INLINE_CHANGELOG_CHARS
+    )
+}
+
+/// Extract the latest version section from CHANGELOG.md content.
+///
+/// Looks for the first `## [version] - date` heading and returns all lines
+/// from that heading up to the next `## [` heading (or end of file).
+/// Leading and trailing whitespace is trimmed.
+fn extract_latest_changelog_section(content: &str) -> Option<String> {
+    let lines: Vec<&str> = content.lines().collect();
+    let mut start_idx: Option<usize> = None;
+
+    for (i, line) in lines.iter().enumerate() {
+        let trimmed = line.trim();
+        if trimmed.starts_with("## [") {
+            start_idx = Some(i);
+            break;
+        }
+    }
+
+    let start = start_idx?;
+
+    // Find the next `## [` heading (or end)
+    let end = lines
+        .iter()
+        .enumerate()
+        .skip(start + 1)
+        .find(|(_, line)| line.trim().starts_with("## ["))
+        .map_or(lines.len(), |(i, _)| i);
+
+    let section = lines[start..end].join("\n");
+    let section = section.trim().to_string();
+
+    if section.is_empty() {
+        return None;
+    }
+
+    Some(section)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::Config;
+    use crate::localization::Locale;
+    use crate::tui::app::{App, TuiOptions};
+    fn make_app(tmpdir: &tempfile::TempDir, locale: Locale, has_api_key: bool) -> App {
+        let mut config = Config::default();
+        if has_api_key {
+            config.api_key = Some("test-key".to_string());
+        }
+        let mut app = App::new(
+            TuiOptions {
+                model: "deepseek-v4-pro".to_string(),
+                workspace: tmpdir.path().to_path_buf(),
+                config_path: None,
+                config_profile: None,
+                allow_shell: false,
+                use_alt_screen: true,
+                use_mouse_capture: false,
+                use_bracketed_paste: true,
+                max_subagents: 1,
+                skills_dir: tmpdir.path().join("skills"),
+                memory_path: tmpdir.path().join("memory.md"),
+                notes_path: tmpdir.path().join("notes.txt"),
+                mcp_config_path: tmpdir.path().join("mcp.json"),
+                use_memory: false,
+                start_in_agent_mode: false,
+                skip_onboarding: true,
+                yolo: false,
+                resume_session_id: None,
+                initial_input: None,
+            },
+            &config,
+        );
+        app.ui_locale = locale;
+        app
+    }
+
+    #[test]
+    fn extract_latest_section_finds_first_version() {
+        let content = "\n\
+## [0.8.26] - 2026-05-09\n\
+\n\
+A security + polish release.\n\
+\n\
+### Fixed\n\
+\n\
+- Fixed something\n\
+\n\
+## [0.8.25] - 2026-05-09\n\
+\n\
+A stabilization release.\n";
+        let section = extract_latest_changelog_section(content).expect("should find a section");
+        assert!(section.contains("0.8.26"));
+        assert!(section.contains("Fixed something"));
+        assert!(!section.contains("0.8.25"));
+    }
+
+    #[test]
+    fn extract_latest_section_handles_0_8_29_style_fixture() {
+        let content = "\n\
+# Changelog\n\
+\n\
+## [0.8.29] - 2026-05-11\n\
+\n\
+Release candidate polish.\n\
+\n\
+### Added\n\
+- New note-management command.\n\
+\n\
+## [0.8.28] - 2026-05-10\n\
+\n\
+Previous release.\n";
+        let section = extract_latest_changelog_section(content).expect("should find a section");
+        assert!(section.contains("0.8.29"));
+        assert!(section.contains("2026-05-11"));
+        assert!(section.contains("New note-management command"));
+        assert!(!section.contains("0.8.28"));
+    }
+
+    #[test]
+    fn extract_latest_section_returns_none_for_empty_content() {
+        assert!(extract_latest_changelog_section("").is_none());
+    }
+
+    #[test]
+    fn extract_latest_section_returns_none_for_no_version_headers() {
+        let content = "# Just a heading\n\nSome text\n";
+        assert!(extract_latest_changelog_section(content).is_none());
+    }
+
+    #[test]
+    fn extract_latest_section_handles_single_version() {
+        let content = "\n## [0.8.26] - 2026-05-09\n\nOnly one version.\n";
+        let section = extract_latest_changelog_section(content).expect("should find a section");
+        assert!(section.contains("0.8.26"));
+        assert!(section.contains("Only one version"));
+    }
+
+    #[test]
+    fn extract_latest_section_handles_subheadings() {
+        let content = "\n\
+## [0.8.26] - 2026-05-09\n\
+\n\
+### Added\n\
+- New feature A\n\
+\n\
+### Fixed\n\
+- Fixed bug B\n\
+\n\
+## [0.8.25] - 2026-05-09\n\
+";
+        let section = extract_latest_changelog_section(content).expect("should find a section");
+        assert!(section.contains("New feature A"));
+        assert!(section.contains("Fixed bug B"));
+        assert!(!section.contains("0.8.25"));
+    }
+
+    #[test]
+    fn change_uses_bundled_release_notes_without_workspace_changelog() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let mut app = make_app(&tmp, Locale::En, false);
+        let result = change(&mut app);
+        assert!(!result.is_error);
+        let msg = result.message.expect("should have a message");
+        let expected = extract_latest_changelog_section(DEEPSEEK_TUI_CHANGELOG)
+            .expect("bundled changelog should have a release section");
+        assert!(msg.contains(expected.lines().next().unwrap()));
+    }
+
+    #[test]
+    fn change_ignores_workspace_changelog() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        std::fs::write(
+            tmp.path().join("CHANGELOG.md"),
+            "\n## [9.9.9] - 2099-01-01\n\nWorkspace changelog.\n",
+        )
+        .unwrap();
+        let mut app = make_app(&tmp, Locale::En, false);
+        let result = change(&mut app);
+        assert!(!result.is_error);
+        let msg = result.message.expect("should have a message");
+        assert!(!msg.contains("9.9.9"));
+        assert!(!msg.contains("Workspace changelog"));
+    }
+
+    #[test]
+    fn change_in_english_returns_message_without_action() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let mut app = make_app(&tmp, Locale::En, true);
+        let result = change(&mut app);
+        assert!(!result.is_error);
+        let msg = result.message.expect("should have a message");
+        let expected = extract_latest_changelog_section(DEEPSEEK_TUI_CHANGELOG)
+            .expect("bundled changelog should have a release section");
+        assert!(msg.contains(expected.lines().next().unwrap()));
+        assert!(
+            result.action.is_none(),
+            "English locale should not send translation"
+        );
+    }
+
+    #[test]
+    fn change_in_non_english_also_sends_translation_action() {
+        for (locale, _label) in [
+            (Locale::ZhHans, "zh-Hans"),
+            (Locale::Ja, "ja"),
+            (Locale::PtBr, "pt-BR"),
+        ] {
+            let tmp = tempfile::TempDir::new().unwrap();
+            let mut app = make_app(&tmp, locale, true);
+            let result = change(&mut app);
+            assert!(!result.is_error, "Failed for locale {locale:?}");
+            let msg = result.message.expect("should have a message");
+            assert!(msg.contains(tr(locale, MessageId::CmdChangeTranslationQueued)));
+            assert!(
+                matches!(result.action, Some(AppAction::SendMessage(_))),
+                "Non-English locale should send translation, got {:?}",
+                result.action
+            );
+            if let Some(AppAction::SendMessage(prompt)) = &result.action {
+                let expected = extract_latest_changelog_section(DEEPSEEK_TUI_CHANGELOG)
+                    .expect("bundled changelog should have a release section");
+                assert!(prompt.contains(expected.lines().next().unwrap()));
+            }
+        }
+    }
+
+    #[test]
+    fn change_in_non_english_without_api_key_uses_explicit_fallback() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let mut app = make_app(&tmp, Locale::ZhHans, false);
+        let result = change(&mut app);
+        assert!(!result.is_error);
+        let msg = result.message.expect("should have a message");
+        assert!(msg.contains(tr(
+            Locale::ZhHans,
+            MessageId::CmdChangeTranslationUnavailable
+        )));
+        assert!(
+            result.action.is_none(),
+            "missing API key should not send translation"
+        );
+    }
+
+    #[test]
+    fn change_in_non_english_offline_uses_explicit_fallback() {
+        let tmp = tempfile::TempDir::new().unwrap();
+        let mut app = make_app(&tmp, Locale::Ja, true);
+        app.offline_mode = true;
+        let result = change(&mut app);
+        assert!(!result.is_error);
+        let msg = result.message.expect("should have a message");
+        assert!(msg.contains(tr(Locale::Ja, MessageId::CmdChangeTranslationUnavailable)));
+        assert!(
+            result.action.is_none(),
+            "offline mode should not send translation"
+        );
+    }
+
+    #[test]
+    fn extract_latest_ignores_lines_before_first_version() {
+        let content = "\n\
+# Changelog\n\
+\n\
+Some intro text.\n\
+\n\
+## [0.8.26] - 2026-05-09\n\
+\n\
+Content\n\
+";
+        let section = extract_latest_changelog_section(content).expect("should find a section");
+        assert!(section.contains("0.8.26"));
+        assert!(!section.contains("Changelog"));
+        assert!(!section.contains("intro text"));
+    }
+}

crates/tui/src/commands/mod.rs

@@ -5,6 +5,7 @@
 
 mod anchor;
 mod attachment;
+mod change;
 mod config;
 mod core;
 mod cycle;
@@ -386,6 +387,12 @@ pub const COMMANDS: &[CommandInfo] = &[
         usage: "/diff",
         description_id: MessageId::CmdDiffDescription,
     },
+    CommandInfo {
+        name: "change",
+        aliases: &[],
+        usage: "/change",
+        description_id: MessageId::CmdChangeDescription,
+    },
     CommandInfo {
         name: "undo",
         aliases: &[],
@@ -558,6 +565,9 @@ pub fn execute(cmd: &str, app: &mut App) -> CommandResult {
         "tokens" => debug::tokens(app),
         "cost" => debug::cost(app),
         "cache" => debug::cache(app, arg),
+
+        // ChangeLog command
+        "change" => change::change(app),
         "system" => debug::system_prompt(app),
         "context" | "ctx" => debug::context(app),
         "edit" => debug::edit(app),

crates/tui/src/localization.rs

@@ -217,6 +217,10 @@ pub enum MessageId {
     CmdAttachDescription,
     CmdAnchorDescription,
     CmdCacheDescription,
+    CmdChangeDescription,
+    CmdChangeHeader,
+    CmdChangeTranslationQueued,
+    CmdChangeTranslationUnavailable,
     CmdClearDescription,
     CmdCompactDescription,
     CmdConfigDescription,
@@ -498,6 +502,10 @@ pub const ALL_MESSAGE_IDS: &[MessageId] = &[
     MessageId::CmdCacheHeader,
     MessageId::CmdCacheNoData,
     MessageId::CmdCacheTotals,
+    MessageId::CmdChangeDescription,
+    MessageId::CmdChangeHeader,
+    MessageId::CmdChangeTranslationQueued,
+    MessageId::CmdChangeTranslationUnavailable,
     MessageId::CmdCostReport,
     MessageId::CmdTokensCacheBoth,
     MessageId::CmdTokensCacheHitOnly,
@@ -783,6 +791,14 @@ fn english(id: MessageId) -> &'static str {
         MessageId::CmdCacheDescription => {
             "Show DeepSeek prefix-cache hit/miss stats for the last N turns"
         }
+        MessageId::CmdChangeDescription => "Show the latest changelog entry",
+        MessageId::CmdChangeHeader => "Latest Changelog",
+        MessageId::CmdChangeTranslationQueued => {
+            "English release notes are shown below. A translated version will be requested next; if the provider is unavailable, this English text is the fallback."
+        }
+        MessageId::CmdChangeTranslationUnavailable => {
+            "English release notes are shown below. Translation is unavailable because the current session has no API key or is offline."
+        }
         MessageId::CmdClearDescription => "Clear conversation history",
         MessageId::CmdCompactDescription => {
             "Trigger context compaction to free up space (legacy; v0.6.6 prefers cycle restart)"
@@ -1118,6 +1134,14 @@ fn japanese(id: MessageId) -> Option<&'static str> {
         MessageId::CmdCacheDescription => {
             "直近 N ターンの DeepSeek プレフィックスキャッシュのヒット/ミス統計を表示"
         }
+        MessageId::CmdChangeDescription => "最新の更新履歴を表示",
+        MessageId::CmdChangeHeader => "最新の更新履歴",
+        MessageId::CmdChangeTranslationQueued => {
+            "英語のリリースノートを以下に表示します。次に翻訳を依頼します。プロバイダーを利用できない場合は、この英語版がフォールバックです。"
+        }
+        MessageId::CmdChangeTranslationUnavailable => {
+            "英語のリリースノートを以下に表示します。現在のセッションに API キーがないかオフラインのため、翻訳は利用できません。"
+        }
         MessageId::CmdClearDescription => "会話履歴をクリア",
         MessageId::CmdCompactDescription => {
             "コンテキスト圧縮で容量を確保（旧式：v0.6.6 以降はサイクル再起動を推奨）"
@@ -1443,6 +1467,14 @@ fn chinese_simplified(id: MessageId) -> Option<&'static str> {
         MessageId::CmdAnchorDescription => "钉选关键事实，在压缩后自动注入上下文",
         MessageId::CmdAttachDescription => "附加图片或视频媒体；文本文件或目录请使用 @path",
         MessageId::CmdCacheDescription => "显示最近 N 轮的 DeepSeek 前缀缓存命中/未命中统计",
+        MessageId::CmdChangeDescription => "显示最新的更新日志",
+        MessageId::CmdChangeHeader => "最新更新日志",
+        MessageId::CmdChangeTranslationQueued => {
+            "下面显示英文发布说明。接下来会请求模型翻译；如果当前提供商不可用，这段英文内容就是备用结果。"
+        }
+        MessageId::CmdChangeTranslationUnavailable => {
+            "下面显示英文发布说明。当前会话没有 API Key 或处于离线状态，无法翻译。"
+        }
         MessageId::CmdClearDescription => "清除对话历史",
         MessageId::CmdCompactDescription => {
             "触发上下文压缩以释放空间（旧版命令；v0.6.6 起建议改用循环重启）"
@@ -1736,6 +1768,14 @@ fn portuguese_brazil(id: MessageId) -> Option<&'static str> {
         MessageId::CmdCacheDescription => {
             "Exibir estatísticas de hit/miss do cache de prefixo DeepSeek nas últimas N rodadas"
         }
+        MessageId::CmdChangeDescription => "Mostrar a entrada mais recente do changelog",
+        MessageId::CmdChangeHeader => "Changelog Mais Recente",
+        MessageId::CmdChangeTranslationQueued => {
+            "As notas de versao em ingles aparecem abaixo. Uma versao traduzida sera solicitada em seguida; se o provedor estiver indisponivel, este texto em ingles sera o fallback."
+        }
+        MessageId::CmdChangeTranslationUnavailable => {
+            "As notas de versao em ingles aparecem abaixo. A traducao esta indisponivel porque a sessao atual nao tem chave de API ou esta offline."
+        }
         MessageId::CmdClearDescription => "Limpar o histórico da conversa",
         MessageId::CmdCompactDescription => {
             "Compactar o contexto para liberar espaço (legado; a v0.6.6 prefere o reinício de ciclo)"