harvest(v0.8.51): diff-render whitespace fix + schema dead_code + model persistence + prompt updates

- fix(diff-render): preserve leading whitespace in patch content lines
  Credit: @zlh124 (PR #2591), with extra-space bug fixed.
- fix(tui): allow unused schema migration registry
  Credit: @reidliu41 (PR #2601).
- feat(tui): persist per-provider model selection from /model command
- docs(prompts): prefer gh --json CLI for GitHub triage in agent instructions

HANDOFF_v0.8.51.md

@@ -0,0 +1,140 @@
+# v0.8.51 Release Handoff — 2026-06-02
+
+## Workspace
+
+```
+/Volumes/VIXinSSD/codewhale
+Branch: codex/v0.8.51-arcee-provider (12 commits ahead of origin/main)
+```
+
+## What's Already Landed (committed, 12 commits on branch)
+
+| Commit | What |
+|--------|------|
+| `e54a0a500` | feat(provider): add direct Arcee support |
+| `99da87ca1` | fix(cli): wire arcee provider auth |
+| `8eca75763` | test(tui): cover arcee provider picker entry |
+| `06612495f` | chore(release): prep v0.8.51 — version bump, CHANGELOG |
+| `fd69f4c80` | fix(tui): strip DEC private mode CSI fragments (#2592) |
+| `5249723e1` | fix(engine): recover from turn panics (#2583, #1269) |
+| `478bae451` | fix(tui): find deeply nested files via @/Ctrl+P (#2488) |
+| `e95f759cd` | fix(tui): command-palette scroll visibility (#2590) |
+| `cccc5ed55` | fix(shell): .NET/NuGet + Windows env (#1857) |
+| `7aa73fad5` | fix(config): warn on misplaced shell/sandbox keys (#2589) |
+| `a7d482067` | fix(clippy): clear -D warnings (#2599) |
+| `79d78878b` | test(mcp): deterministic SSE reconnect (#2597) |
+| `f886f28ac` | test(tui): update walk-depth test for new default depth |
+
+**Claude branch `origin/claude/busy-mayer-b66rA` is identical to our HEAD** — same commit `f886f28ac`. Nothing to merge; already up to date.
+
+## What's Applied in Working Tree (NOT committed)
+
+4 files modified (88 insertions, 25 deletions):
+
+| File | Change | Credits |
+|------|--------|---------|
+| `crates/tui/src/tui/diff_render.rs` | `wrap_text` preserves leading whitespace; fixes extra-space bug in PR #2591; adds 2 regression tests | @zlh124 (PR #2591, fix version from working tree) |
+| `crates/tui/src/schema_migration.rs` | `#[allow(dead_code)]` on `pub mod registry` | @reidliu41 (PR #2601) |
+| `crates/tui/src/prompts/base.md` | Tool desc: prefer `gh --json` CLI for GitHub triage | — |
+| `crates/tui/src/prompts/base.txt` | Same prompt update for text variant | — |
+
+## Ready to Apply (patch saved, NOT yet applied)
+
+The model persistence patch is at `/tmp/model_persist.patch` (240 lines, 2 files):
+
+- `crates/tui/src/commands/core.rs`: `/model` command remembers per-provider model selection + persist warning
+- `crates/tui/src/settings.rs`: new `set_provider_model_selection()` and `persist_provider_model_selection()` methods
+
+**Apply it:**
+```bash
+cd /Volumes/VIXinSSD/codewhale
+git apply /tmp/model_persist.patch
+```
+
+This is small, self-contained, and directly improves UX for the new Arcee provider (model choice remembered across restarts). No dependency on the deferred image-attachment work.
+
+## Deferred (in stash, do NOT apply for v0.8.51)
+
+The stash (`stash@{0}`) contains:
+
+- **Image attachment** (#2584/#2587): `ContentBlock::ImageUrl`, multimodal chat requests, base64 encoding, + exhaustive match arms across 15 files. Deferred by Hmbown — changes the request shape, needs multimodal endpoint testing.
+- **GitHub structured route** (`fetch_url.rs`): new feature — routes GitHub issue/PR URLs through `gh` CLI. Too broad for v0.8.51.
+- **Config custom model changes** (`commands/config.rs`): `normalize_custom_model_id` etc. Need review.
+
+To view: `git stash show -p stash@{0}`
+
+## What Remains
+
+```bash
+cd /Volumes/VIXinSSD/codewhale
+
+# 1. Apply the model persistence patch
+git apply /tmp/model_persist.patch
+
+# 2. Commit all working-tree changes as one harvest commit
+git add -A
+git commit -m "harvest(v0.8.51): diff-render whitespace fix + schema dead_code + model persistence + prompt updates
+
+- fix(diff-render): preserve leading whitespace in patch content lines
+  Credit: @zlh124 (PR #2591), with extra-space bug fixed.
+- fix(tui): allow unused schema migration registry
+  Credit: @reidliu41 (PR #2601).
+- feat(tui): persist per-provider model selection from /model command
+- docs(prompts): prefer gh --json CLI for GitHub triage in agent instructions"
+
+# 3. Run release gates
+cargo fmt --all -- --check
+cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
+cargo test -p codewhale-tui -- --test-threads=4
+
+# 4. If gates pass, rebuild
+cargo install --path crates/tui --locked --force
+codewhale --version
+codewhale-tui --version
+
+# 5. Final checks
+git diff origin/main --stat
+gh issue view 2600 --repo Hmbown/CodeWhale  # re-read release checklist
+```
+
+## Release Checklist Status (issue #2600)
+
+- [x] Arcee provider landed + tested
+- [x] Cycle/checkpoint-restart system removed
+- [x] Auto-compaction percentage/model-aware
+- [x] Provider/gateway HTTP error sanitization
+- [x] TUI fixes (blue dot, sidebar scroll, tooltip)
+- [x] CHANGELOG + version bump
+- [x] Clippy clean (#2599)
+- [x] MCP SSE test deterministic (#2597)
+- [ ] Full `cargo test --workspace` green — codewhale-tui validated; 1 environment-only Landlock test may fail on macOS
+- [ ] `npm test` in `npm/codewhale`
+- [ ] Harvest commits applied + re-gated
+- [ ] Merge branch to `main`
+- [ ] Tag `v0.8.51`, push tag
+- [ ] Publish GitHub release + `npm publish`
+
+## Contributors to Credit
+
+| Contributor | Contribution | PR/Issue |
+|-------------|-------------|----------|
+| @zlh124 (jayzhu) | diff-render whitespace preservation | #2591 |
+| @reidliu41 (Reid) | schema migration dead_code allow | #2601 |
+| @xyuai | Image attachment root cause + initial PR | #2587, #2584 |
+| @IcedOranges | Image attachment bug report | #2584 |
+| @idling11 (Hanmiao Li) | Sidebar resize feature request | #2602 |
+| @gordonlu (Gordon) | Engine death recovery | #2585 |
+| @cyq1017 | File picker depth fix draft | #2593 |
+
+## Risks / Notes
+
+1. **Working tree was stashed** — the image attachment feature and GitHub structured route are deferred for v0.8.52+. The model persistence patch is the only remaining piece worth landing.
+2. **DeepSeek naming**: The branch and committed code use "CodeWhale" naming throughout. Do not imply DeepSeek is deprecated.
+3. **The `origin/claude/busy-mayer-b66rA` branch is identical to HEAD** — the Claude Code session in #2600 claimed "+8 commits" but those are the same commits already on this branch. Verify with `git rev-parse HEAD origin/claude/busy-mayer-b66rA`.
+4. **Landlock test**: `sandbox::tests::test_parity_linux_landlock_available` will fail on macOS (no Landlock LSM). This is environment-only, not a regression. On CI Linux runners it passes.
+5. **Cross-platform artifacts**: The release workflow builds macOS + Windows + NSIS installer on tag push. Not buildable locally on macOS alone.
+
+---
+
+Generated by deepseek-v4-pro in CodeWhale v0.8.51 pre-release triage.
+Next session: read this file, apply `/tmp/model_persist.patch`, run gates, commit, and prepare the merge.

crates/tui/src/commands/core.rs

@@ -134,10 +134,18 @@ pub fn model(app: &mut App, model_name: Option<&str>) -> CommandResult {
                 app.session.last_prompt_tokens = None;
                 app.session.last_completion_tokens = None;
             }
+            app.provider_models
+                .insert(app.api_provider.as_str().to_string(), "auto".to_string());
+            let persist_warning =
+                provider_model_selection_persist_warning(app.api_provider, "auto");
+            let mut message = tr(app.ui_locale, MessageId::ModelChanged)
+                .replace("{old}", &old_model)
+                .replace("{new}", "auto");
+            if let Some(warning) = persist_warning {
+                message.push_str(&warning);
+            }
             return CommandResult::with_message_and_action(
-                tr(app.ui_locale, MessageId::ModelChanged)
-                    .replace("{old}", &old_model)
-                    .replace("{new}", "auto"),
+                message,
                 AppAction::UpdateCompaction(app.compaction_config()),
             );
         }
@@ -181,10 +189,17 @@ pub fn model(app: &mut App, model_name: Option<&str>) -> CommandResult {
             app.session.last_prompt_tokens = None;
             app.session.last_completion_tokens = None;
         }
+        app.provider_models
+            .insert(app.api_provider.as_str().to_string(), model_id.clone());
+        let persist_warning = provider_model_selection_persist_warning(app.api_provider, &model_id);
+        let mut message = tr(app.ui_locale, MessageId::ModelChanged)
+            .replace("{old}", &old_model)
+            .replace("{new}", &model_id);
+        if let Some(warning) = persist_warning {
+            message.push_str(&warning);
+        }
         CommandResult::with_message_and_action(
-            tr(app.ui_locale, MessageId::ModelChanged)
-                .replace("{old}", &old_model)
-                .replace("{new}", &model_id),
+            message,
             AppAction::UpdateCompaction(app.compaction_config()),
         )
     } else {
@@ -192,6 +207,12 @@ pub fn model(app: &mut App, model_name: Option<&str>) -> CommandResult {
     }
 }
 
+fn provider_model_selection_persist_warning(provider: ApiProvider, model: &str) -> Option<String> {
+    crate::settings::Settings::persist_provider_model_selection(provider, model)
+        .err()
+        .map(|err| format!(" (not persisted: {err})"))
+}
+
 fn saved_provider_model_match(app: &App, name: &str) -> Option<(ApiProvider, String)> {
     let requested = normalize_custom_model_id(name)?;
     let mut saved = app
@@ -454,9 +475,49 @@ mod tests {
     use crate::models::Message;
     use crate::tui::app::{App, AppMode, TuiOptions, TurnCacheRecord};
     use crate::tui::history::HistoryCell;
+    use std::ffi::OsString;
     use std::path::PathBuf;
     use std::time::Instant;
-    use tempfile::tempdir;
+    use tempfile::{TempDir, tempdir};
+
+    struct SettingsPathGuard {
+        _tmp: TempDir,
+        previous: Option<OsString>,
+        _lock: std::sync::MutexGuard<'static, ()>,
+    }
+
+    impl SettingsPathGuard {
+        fn new() -> Self {
+            let lock = crate::test_support::lock_test_env();
+            let tmp = TempDir::new().expect("settings tempdir");
+            let config_path = tmp.path().join(".deepseek").join("config.toml");
+            std::fs::create_dir_all(config_path.parent().expect("config parent"))
+                .expect("config dir");
+            let previous = std::env::var_os("DEEPSEEK_CONFIG_PATH");
+            // Safety: test-only environment mutation guarded by a global mutex.
+            unsafe {
+                std::env::set_var("DEEPSEEK_CONFIG_PATH", &config_path);
+            }
+            Self {
+                _tmp: tmp,
+                previous,
+                _lock: lock,
+            }
+        }
+    }
+
+    impl Drop for SettingsPathGuard {
+        fn drop(&mut self) {
+            // Safety: test-only environment mutation guarded by a global mutex.
+            unsafe {
+                if let Some(previous) = self.previous.take() {
+                    std::env::set_var("DEEPSEEK_CONFIG_PATH", previous);
+                } else {
+                    std::env::remove_var("DEEPSEEK_CONFIG_PATH");
+                }
+            }
+        }
+    }
 
     fn create_test_app() -> App {
         let options = TuiOptions {
@@ -718,6 +779,7 @@ mod tests {
 
     #[test]
     fn test_model_change_updates_state() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         let old_model = app.model.clone();
         let result = model(&mut app, Some("deepseek-v4-flash"));
@@ -734,8 +796,34 @@ mod tests {
         assert_eq!(app.session.last_completion_tokens, None);
     }
 
+    #[test]
+    fn model_command_persists_active_provider_model() {
+        let _settings = SettingsPathGuard::new();
+        let mut app = create_test_app();
+
+        let result = model(&mut app, Some("deepseek-v4-flash"));
+
+        assert!(result.message.is_some());
+        assert_eq!(
+            app.provider_models.get("deepseek").map(String::as_str),
+            Some("deepseek-v4-flash")
+        );
+        let settings = crate::settings::Settings::load().expect("load settings");
+        assert_eq!(settings.default_provider.as_deref(), Some("deepseek"));
+        assert_eq!(settings.default_model.as_deref(), Some("deepseek-v4-flash"));
+        assert_eq!(
+            settings
+                .provider_models
+                .as_ref()
+                .and_then(|models| models.get("deepseek"))
+                .map(String::as_str),
+            Some("deepseek-v4-flash")
+        );
+    }
+
     #[test]
     fn model_switch_clears_turn_cache_history() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         // Keep the assertion independent of the developer's saved default model.
         app.auto_model = false;
@@ -757,6 +845,7 @@ mod tests {
 
     #[test]
     fn model_reset_same_model_keeps_turn_cache_history() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         app.auto_model = false;
         app.model = "deepseek-v4-pro".to_string();
@@ -777,6 +866,7 @@ mod tests {
 
     #[test]
     fn test_model_auto_enables_auto_thinking() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         app.reasoning_effort = ReasoningEffort::Off;
 
@@ -792,6 +882,7 @@ mod tests {
 
     #[test]
     fn test_model_change_accepts_future_deepseek_model() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         let result = model(&mut app, Some("deepseek-v4"));
         assert!(result.message.is_some());
@@ -806,6 +897,7 @@ mod tests {
 
     #[test]
     fn test_model_change_accepts_custom_id_for_openai_compatible_provider() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         app.api_provider = crate::config::ApiProvider::Openai;
         app.model_ids_passthrough = true;
@@ -823,6 +915,7 @@ mod tests {
 
     #[test]
     fn test_model_change_accepts_custom_id_for_custom_base_url() {
+        let _settings = SettingsPathGuard::new();
         let mut app = create_test_app();
         app.model_ids_passthrough = true;
 

crates/tui/src/prompts/base.md

@@ -245,7 +245,7 @@ When context is deep (past a soft seam): cache reasoning conclusions in concise
 - **Planning / tracking**: `checklist_write` (primary Work progress under the active task/thread), `checklist_add` / `checklist_update` / `checklist_list`, `update_plan` (optional high-level strategy metadata for complex initiatives), `task_create` / `task_list` / `task_read` / `task_cancel` (durable work objects), `todo_*` aliases (legacy compatibility), `note` (persistent memory).
 - **File I/O**: `read_file` (PDFs auto-extracted), `list_dir`, `write_file`, `edit_file`, `apply_patch`, `retrieve_tool_result` for prior spilled large tool outputs.
 - **Shell**: `task_shell_start` + `task_shell_wait` for long-running commands, diagnostics, tests, searches, and servers; `exec_shell` for bounded cancellable foreground commands; `exec_shell_wait`, `exec_shell_interact`. If foreground `exec_shell` times out, the process was killed; rerun long work with `task_shell_start` or `exec_shell` using `background: true`, then poll/wait.
-- **Task evidence**: `task_gate_run` for verification gates; `pr_attempt_record` / `pr_attempt_list` / `pr_attempt_read` / `pr_attempt_preflight`; `github_issue_context` / `github_pr_context` (read-only); `github_comment` / `github_close_issue` (approval + evidence required); `automation_*` scheduling tools.
+- **Task evidence**: `task_gate_run` for verification gates; `pr_attempt_record` / `pr_attempt_list` / `pr_attempt_read` / `pr_attempt_preflight`; for GitHub issue/PR/release triage, prefer the native `gh ... --json` CLI through shell because it is authenticated, structured, and reproducible; `github_issue_context` / `github_pr_context` are read-only fallbacks when the CLI route is unavailable; `github_comment` / `github_close_issue` require approval + evidence; `automation_*` scheduling tools.
 - **Structured search**: `grep_files`, `file_search`, `web_search`, `fetch_url`, `web.run` (browse).
 - **Git / diag / tests**: `git_status`, `git_diff`, `git_show`, `git_log`, `git_blame`, `diagnostics`, `run_tests`, `run_verifiers`, `review`.
 - **Sub-agents**: `agent_open`, `agent_eval`, `agent_close`. Open fresh sessions by default; pass `fork_context: true` only when the child needs the current parent context and prefix-cache continuity.

crates/tui/src/prompts/base.txt

@@ -40,7 +40,7 @@ Model notes: DeepSeek V4 models emit *thinking tokens* (`ContentBlock::Thinking`
 - **Planning / tracking**: `checklist_write` (primary Work progress under the active task/thread), `checklist_add` / `checklist_update` / `checklist_list`, `update_plan` (optional high-level strategy metadata for complex initiatives), `task_create` / `task_list` / `task_read` / `task_cancel` (durable work objects), `todo_*` aliases (legacy compatibility), `note` (persistent memory).
 - **File I/O**: `read_file` (PDFs auto-extracted), `list_dir`, `write_file`, `edit_file`, `apply_patch`, `retrieve_tool_result` for prior spilled large tool outputs.
 - **Shell**: `task_shell_start` + `task_shell_wait` for long-running commands, diagnostics, tests, searches, and servers; `exec_shell` for bounded cancellable foreground commands; `exec_shell_wait`, `exec_shell_interact`.
-- **Task evidence**: `task_gate_run` for verification gates; `pr_attempt_record` / `pr_attempt_list` / `pr_attempt_read` / `pr_attempt_preflight`; `github_issue_context` / `github_pr_context` (read-only); `github_comment` / `github_close_issue` (approval + evidence required); `automation_*` scheduling tools.
+- **Task evidence**: `task_gate_run` for verification gates; `pr_attempt_record` / `pr_attempt_list` / `pr_attempt_read` / `pr_attempt_preflight`; for GitHub issue/PR/release triage, prefer the native `gh ... --json` CLI through shell because it is authenticated, structured, and reproducible; `github_issue_context` / `github_pr_context` are read-only fallbacks when the CLI route is unavailable; `github_comment` / `github_close_issue` require approval + evidence; `automation_*` scheduling tools.
 - **Structured search**: `grep_files`, `file_search`, `web_search`, `fetch_url`, `web.run` (browse).
 - **Git / diag / tests**: `git_status`, `git_diff`, `git_show`, `git_log`, `git_blame`, `diagnostics`, `run_tests`, `run_verifiers`, `review`.
 - **Sub-agents**: `agent_open`, `agent_eval`, `agent_close`. Fresh sessions are the default; use `fork_context: true` when multiple perspectives need the current parent context and byte-identical prefill/prompt prefix for DeepSeek prefix-cache reuse. Use `tool_agent` for experimental Fin fast-lane execution: simple tool-bound OCR/search/fetch/probe work on Flash V4 with thinking off.

crates/tui/src/schema_migration.rs

@@ -205,6 +205,7 @@ pub fn backup_before_migrate(path: &Path, domain: &str) -> PathBuf {
 /// 3. Bump `CURRENT_VERSION` to match.
 /// 4. Wire `<Domain>Migration::migrate(...)` into the load function in
 ///    the owning module.
+#[allow(dead_code)]
 pub mod registry {
     use super::{MigrationFn, SchemaMigration};
 

crates/tui/src/settings.rs

@@ -10,7 +10,7 @@ use std::path::PathBuf;
 use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
 
-use crate::config::{expand_path, normalize_model_name};
+use crate::config::{ApiProvider, expand_path, normalize_model_name};
 use crate::localization::normalize_configured_locale;
 use crate::palette::{normalize_hex_rgb_color, normalize_theme_name};
 
@@ -943,6 +943,32 @@ impl Settings {
             .insert(provider.to_string(), model.to_string());
     }
 
+    /// Persist the active provider/model tuple that runtime selection UI and
+    /// slash commands should restore on the next startup.
+    pub fn set_provider_model_selection(
+        &mut self,
+        provider: ApiProvider,
+        model: &str,
+    ) -> Result<()> {
+        let model = model.trim();
+        if model.is_empty() {
+            anyhow::bail!("model cannot be empty");
+        }
+        self.default_provider = Some(provider.as_str().to_string());
+        self.set_model_for_provider(provider.as_str(), model);
+        if matches!(provider, ApiProvider::Deepseek | ApiProvider::DeepseekCN) {
+            self.set("default_model", model)?;
+        }
+        Ok(())
+    }
+
+    /// Load, update, and save the runtime provider/model selection.
+    pub fn persist_provider_model_selection(provider: ApiProvider, model: &str) -> Result<()> {
+        let mut settings = Self::load()?;
+        settings.set_provider_model_selection(provider, model)?;
+        settings.save()
+    }
+
     /// 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

crates/tui/src/tui/diff_render.rs

@@ -341,43 +341,61 @@ fn wrap_text(text: &str, width: usize) -> Vec<String> {
     if width == 0 {
         return vec![text.to_string()];
     }
-    let mut lines = Vec::new();
-    let mut current = String::new();
-    let mut current_width = 0;
-
-    for word in text.split_whitespace() {
-        let word_width = word.width();
-        if word_width > width {
-            if !current.is_empty() {
-                lines.push(std::mem::take(&mut current));
-                current_width = 0;
-            }
-            push_word_breaking_chars(word, width, &mut current, &mut current_width, &mut lines);
-            continue;
-        }
-        let additional = if current.is_empty() {
-            word_width
-        } else {
-            word_width + 1
-        };
-        if current_width + additional > width && !current.is_empty() {
-            lines.push(current);
-            current = word.to_string();
-            current_width = word_width;
-        } else {
-            if !current.is_empty() {
-                current.push(' ');
-                current_width += 1;
-            }
-            current.push_str(word);
-            current_width += word_width;
-        }
+    let lead = text
+        .chars()
+        .take_while(|ch| ch.is_whitespace())
+        .collect::<String>();
+    let trimmed = text.trim_start();
+    if trimmed.is_empty() {
+        return vec![text.to_string()];
     }
 
-    if current.is_empty() {
-        lines.push(String::new());
-    } else {
+    let mut lines = Vec::new();
+    let lead_width = lead.width();
+    let mut current = lead.clone();
+    let mut current_width = lead_width;
+    let mut has_word = false;
+
+    for word in trimmed.split_whitespace() {
+        let word_width = word.width();
+        if word_width > width {
+            if has_word {
+                lines.push(std::mem::take(&mut current));
+                current = lead.clone();
+                current_width = lead_width;
+            }
+            push_word_breaking_chars(word, width, &mut current, &mut current_width, &mut lines);
+            has_word = current_width > lead_width;
+            continue;
+        }
+        let additional = if has_word { word_width + 1 } else { word_width };
+        if current_width + additional > width && has_word {
+            lines.push(current);
+            current = lead.clone();
+            current_width = lead_width;
+            has_word = false;
+        }
+        if has_word {
+            current.push(' ');
+            current_width += 1;
+        }
+        if current_width + word_width > width && !has_word && lead_width > 0 {
+            lines.push(std::mem::take(&mut current));
+            current_width = 0;
+        }
+        if current_width == 0 && lead_width > 0 && word_width + lead_width <= width {
+            current = lead.clone();
+            current_width = lead_width;
+        }
+        current.push_str(word);
+        current_width += word_width;
+        has_word = true;
+    }
+
+    if has_word || !current.is_empty() {
         lines.push(current);
+    } else {
+        lines.push(String::new());
     }
 
     lines
@@ -412,6 +430,10 @@ mod tests {
             .collect()
     }
 
+    fn diff_content_text(line: &Line<'static>) -> Option<String> {
+        line.spans.get(1).map(|span| span.content.to_string())
+    }
+
     #[test]
     fn summarizes_multi_file_diff() {
         let diff = "\
@@ -467,6 +489,46 @@ diff --git a/src/a.rs b/src/a.rs
         );
     }
 
+    #[test]
+    fn wrap_text_preserves_leading_whitespace_without_extra_space() {
+        assert_eq!(wrap_text("    let y = 2;", 80), vec!["    let y = 2;"]);
+        assert_eq!(
+            wrap_text("        println!(\"hello\");", 80),
+            vec!["        println!(\"hello\");"]
+        );
+    }
+
+    #[test]
+    fn render_diff_preserves_leading_whitespace_exactly() {
+        let diff = "\
+diff --git a/src/lib.rs b/src/lib.rs
+--- a/src/lib.rs
++++ b/src/lib.rs
+@@ -1,2 +1,3 @@
+ fn main() {
++    let y = 2;
++        println!(\"{y}\");
+ }
+";
+
+        let rendered = render_diff(diff, 80);
+        let content = rendered
+            .iter()
+            .filter_map(diff_content_text)
+            .collect::<Vec<_>>();
+
+        assert!(
+            content.iter().any(|line| line == "    let y = 2;"),
+            "added line should keep exact 4-space indent: {content:?}"
+        );
+        assert!(
+            content
+                .iter()
+                .any(|line| line == "        println!(\"{y}\");"),
+            "added line should keep exact 8-space indent: {content:?}"
+        );
+    }
+
     #[test]
     fn wrap_text_breaks_overlong_cjk_runs() {
         let text = "这是一个非常长的中文字符串".repeat(10);