docs: map existing codebase

.planning/codebase/ARCHITECTURE.md

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+# Architecture
+
+**Analysis Date:** 2026-03-21
+
+## Pattern Overview
+
+**Overall:** Actor-based event-driven TUI application with layered state management
+
+**Key Characteristics:**
+- Async event loop (Tokio) consuming terminal input events and dispatching to named `Actor` implementations
+- Strict separation between state (`yazi-core`), actions (`yazi-actor`), and rendering (`yazi-fm` UI widgets)
+- Lua scripting layer (`yazi-plugin`) hooks into the same state via `Lives` scoped userdata
+- Cross-process pub/sub via a Unix socket server (`yazi-dds`) allowing multiple yazi instances and the `ya` CLI to communicate
+
+## Layers
+
+**Entry Point / Binary:**
+- Purpose: Initialize all subsystems, start the Tokio event loop, drive `App::serve()`
+- Location: `yazi-fm/src/main.rs`
+- Contains: `main()`, subsystem `init()` calls in order, global allocator (jemalloc)
+- Depends on: Every other crate
+- Used by: OS process runner
+
+**App Loop (`App`):**
+- Purpose: Receive `Event` variants from a Tokio MPSC channel; throttle renders (max 10ms interval); coordinate `Dispatcher`
+- Location: `yazi-fm/src/app/app.rs`
+- Contains: `Core`, `Term`, `Signals`; the `serve()` async loop
+- Depends on: `yazi-core`, `yazi-term`, `yazi-actor`, `yazi-shared`
+- Used by: `main()`
+
+**Dispatcher:**
+- Purpose: Match each `Event` variant to the right handler — key events go to `Router`, action calls go to `Executor`, render/resize/mouse/paste handled directly
+- Location: `yazi-fm/src/dispatcher.rs`
+- Contains: `dispatch()` method with exhaustive `Event` match
+- Depends on: `Router`, `Executor`, `yazi-actor::Ctx`
+- Used by: `App::serve()`
+
+**Router:**
+- Purpose: Translate a `Key` press into an `ActionCow` sequence by looking up `KEYMAP` for the current `Layer`
+- Location: `yazi-fm/src/router.rs`
+- Contains: `route()`, `matches()`; multi-key chords activate the `which` overlay
+- Depends on: `yazi-config::KEYMAP`, `yazi-actor::Ctx`
+- Used by: `Dispatcher::dispatch_key()`
+
+**Executor:**
+- Purpose: Dispatch a named `ActionCow` to the correct `Actor::act()` call, organized by `Layer`
+- Location: `yazi-fm/src/executor.rs`
+- Contains: `execute()` with per-layer handler methods (`app`, `mgr`, `tasks`, `spot`, `pick`, `input`, `confirm`, `help`, `cmp`, `which`, `notify`)
+- Depends on: `yazi-actor`, `yazi-macro::act!`
+- Used by: `Dispatcher::dispatch_call()`
+
+**Core State (`Core`):**
+- Purpose: Owns all live application state as a single flat struct
+- Location: `yazi-core/src/core.rs`
+- Contains: `Mgr`, `Tasks`, `Pick`, `Input`, `Confirm`, `Help`, `Cmp`, `Which`, `Notify`
+- Depends on: `yazi-core` sub-modules
+- Used by: `App`, `Ctx`, `Root` renderer
+
+**Mgr / Tab:**
+- Purpose: File manager state — multiple tabs, yanked clipboard, filesystem watcher, MIME cache
+- Location: `yazi-core/src/mgr/mgr.rs`, `yazi-core/src/tab/tab.rs`
+- Contains: `Mgr { tabs, yanked, watcher, mimetype }`, `Tab { current, parent, history, selected, spot, preview, finder, search, ... }`
+- Depends on: `yazi-fs`, `yazi-watcher`, `yazi-vfs`
+- Used by: `Core`, `Ctx`
+
+**Actor Trait & Implementations:**
+- Purpose: Each user-visible command is a zero-size struct implementing `Actor { type Options; fn act(cx, opt) -> Result<Data> }`
+- Location: `yazi-actor/src/actor.rs` (trait), `yazi-actor/src/mgr/`, `yazi-actor/src/app/`, etc.
+- Contains: ~60 mgr actors (cd, arrow, open, yank, paste, search, tab_create, upload...), app actors (bootstrap, resize, plugin, quit...), plus per-overlay actors
+- Depends on: `yazi-actor::Ctx`, `yazi-proxy`, `yazi-parser`, `yazi-macro::act!`
+- Used by: `Executor` via the `act!` macro
+
+**Ctx (Action Context):**
+- Purpose: Borrows `Core` mutably for the duration of an action; provides convenience accessors for the active tab, current folder, hovered file
+- Location: `yazi-actor/src/context.rs`
+- Contains: `Ctx { core, term, tab, level, source }`; `Deref`/`DerefMut` into `Core`
+- Depends on: `yazi-core::Core`, `yazi-term::Term`
+- Used by: every `Actor::act()` implementation
+
+**Proxy Layer:**
+- Purpose: Allow background async tasks (scheduler workers, plugin coroutines) to emit actions without holding `Core` references — they emit `Event::Call` via the shared channel
+- Location: `yazi-proxy/src/`
+- Contains: `MgrProxy`, `InputProxy`, `CmpProxy`, `TasksProxy`, etc. — thin wrappers that call `emit!(Call(relay!(...)))`
+- Depends on: `yazi-shared::event::Event`, `yazi-macro`
+- Used by: `yazi-actor` async tasks, `yazi-scheduler`, `yazi-plugin`
+
+**Parser Layer:**
+- Purpose: Typed `Options` structs for every action; decouples serialization/deserialization from actor logic
+- Location: `yazi-parser/src/`
+- Contains: Per-overlay modules (`mgr`, `app`, `input`, ...) with structs like `CdOpt`, `OpenOpt`, `SortOpt`
+- Depends on: `yazi-shared`
+- Used by: `yazi-actor` implementations
+
+**Renderer (`Root`):**
+- Purpose: Compose the ratatui `Widget` tree; delegate to Lua for the base UI layout; render overlays in z-order
+- Location: `yazi-fm/src/root.rs`
+- Contains: `Root::render()` calls Lua `Root:new(area):redraw()`, then renders `Preview`, `Modal`, and all visible overlays
+- Depends on: `yazi-binding`, `yazi-plugin::LUA`, `yazi-core::Core`
+- Used by: `App::render()`
+
+**Lua Plugin System:**
+- Purpose: Provide a Lua 5.5 scripting environment; expose Rust state as read-only `UserData` via `Lives` scoped bindings
+- Location: `yazi-plugin/src/`, `yazi-binding/src/`, `yazi-actor/src/lives/`
+- Contains: `Lives::scope()` pins `Core` as a Lua global `cx`; `yazi-binding` exposes element types (Rect, Style, etc.) and state accessors
+- Depends on: `mlua`, `yazi-core`, `yazi-config`
+- Used by: `Root::render()`, `App::render()`, `AcceptPayload` actor
+
+**Scheduler:**
+- Purpose: Execute file operations, preload/fetch tasks, plugin workers, and external processes with configurable concurrency and priority queues
+- Location: `yazi-scheduler/src/`
+- Contains: `fetch/`, `file/`, `plugin/`, `preload/`, `process/`, `size/` task types; a `Scheduler` runner
+- Depends on: `yazi-proxy`, `yazi-fs`, `yazi-plugin`
+- Used by: `yazi-core::Tasks`
+
+**DDS (Data Distribution Service):**
+- Purpose: IPC broker — Unix domain socket server that routes typed `Payload` messages between yazi instances and the `ya` CLI
+- Location: `yazi-dds/src/`
+- Contains: `Server` (accepts connections, routes by receiver ID and `ability`), `Client` (connects, sends/receives), `Pubsub` (local/remote event subscriptions), `Payload`/`Ember` types
+- Depends on: `tokio`, `yazi-shared`, `yazi-boot`
+- Used by: `main()` (calls `yazi_dds::serve()`), `yazi-cli` for `emit`/`pub`/`sub` commands
+
+**VFS / SFTP:**
+- Purpose: Abstract filesystem access; local filesystem ops go through `yazi-fs`; remote (SFTP) access goes through `yazi-sftp` + `yazi-vfs::provider`
+- Location: `yazi-vfs/src/`, `yazi-sftp/src/`
+- Contains: `VfsFile`, `provider::` with local and SFTP providers; `yazi-sftp` implements the SSH/SFTP protocol via `russh`
+- Depends on: `russh`, `yazi-fs`, `tokio`
+- Used by: `yazi-actor` cd/download/upload actors, `yazi-core`
+
+**Image Adapter:**
+- Purpose: Detect terminal emulator capabilities and render inline images using the best available protocol
+- Location: `yazi-adapter/src/`
+- Contains: `Adapter` enum (Kgp, KgpOld, Iip, Sixel, Chafa, Ueberzug); `drivers/` with one file per protocol; `yazi-emulator` handles brand/capability detection
+- Depends on: `yazi-emulator`, `ratatui`
+- Used by: preview rendering in `yazi-fm`
+
+## Data Flow
+
+**Key press to screen update:**
+
+1. `crossterm` event arrives on `Signals` task → `Event::Key` emitted to shared MPSC channel
+2. `App::serve()` drains up to 50 events per batch
+3. `Dispatcher::dispatch_key()` → `Router::route()` looks up keymap for current `Layer` → emits `Event::Seq` or `Event::Call`
+4. `Dispatcher::dispatch_call()` → `Executor::execute()` matches layer + action name → calls `act!(layer:name, cx, action)`
+5. `Actor::act()` mutates `Core` fields, optionally spawns async tasks via `tokio::spawn` with result posted back through `Proxy::*` → `emit!(Call(...))`
+6. After each event, `NEED_RENDER` atomic is checked; if set and ≥10ms since last frame, `App::render()` is called
+7. `Root::render()` calls Lua `cx` (populated via `Lives::scope`), then renders Rust overlay widgets into ratatui `Buffer`
+8. `Term::draw()` diffs buffer and writes escape sequences via `crossterm` + `TTY`
+
+**DDS message from `ya emit`:**
+
+1. `ya` CLI connects to Unix socket, sends `hi` then payload then `bye`
+2. `yazi-dds::Server` routes to connected yazi instance(s) by receiver ID and ability set
+3. Receiving yazi instance's `Client` loop receives line, parses `Payload`, calls `payload.emit()` → `Event::Call(accept_payload)`
+4. `AcceptPayload::act()` looks up registered Lua handlers in `LOCAL`/`REMOTE` pubsub tables, calls each via `LUA`
+
+**State management:**
+
+- `Core` is owned by `App` and mutated synchronously on the Tokio local set thread
+- Background tasks (async Tokio tasks) never hold `&mut Core`; they post results back via `Proxy` functions that emit `Event::Call`
+- Lua scripts access a read-only snapshot of state through `Lives`-scoped `UserData` bound to the current `Core` reference
+
+## Key Abstractions
+
+**`Actor` trait:**
+- Purpose: Uniform interface for every command in the system
+- Examples: `yazi-actor/src/mgr/cd.rs`, `yazi-actor/src/mgr/open.rs`, `yazi-actor/src/app/bootstrap.rs`
+- Pattern: Zero-size structs; `type Options` parsed from `ActionCow`; `fn act(cx, opt) -> Result<Data>`; optional `fn hook()` for post-action DDS sparks
+
+**`Event` enum:**
+- Purpose: Central message bus shared between terminal input, action dispatch, and render scheduling
+- Location: `yazi-shared/src/event/event.rs`
+- Variants: `Call(ActionCow)`, `Seq(Vec<ActionCow>)`, `Render(bool)`, `Key`, `Mouse`, `Resize`, `Focus`, `Paste`
+
+**`Layer` enum:**
+- Purpose: Tracks which UI overlay is topmost, determining keymap lookup and executor routing
+- Location: `yazi-shared/src/layer.rs`
+- Values: `Mgr`, `Tasks`, `Spot`, `Pick`, `Input`, `Confirm`, `Help`, `Cmp`, `Which`, `App`, `Notify`
+
+**`Ctx` struct:**
+- Purpose: Short-lived mutable borrow of `Core` enriched with active tab index and action source; passed to every `Actor::act()`
+- Location: `yazi-actor/src/context.rs`
+- Pattern: Created by `Ctx::new(&action, core, term)` at start of `Executor` method; `Deref` into `Core` for ergonomic access
+
+**`RoCell` / `SyncCell`:**
+- Purpose: Thread-safe write-once containers used as module-level globals (replacing `lazy_static` / `OnceLock`)
+- Location: `yazi-shared/src/ro_cell.rs`, `yazi-shared/src/sync_cell.rs`
+- Pattern: `pub static FOO: RoCell<T> = RoCell::new(); ... FOO.init(value);`
+
+## Entry Points
+
+**`yazi-fm` binary:**
+- Location: `yazi-fm/src/main.rs`
+- Triggers: User runs `yazi` in terminal
+- Responsibilities: Calls `init()` on every crate in dependency order; starts DDS `serve()`; runs `App::serve()` on Tokio local set
+
+**`yazi-cli` binary (`ya`):**
+- Location: `yazi-cli/src/main.rs`
+- Triggers: User runs `ya emit|pub|sub|pkg`
+- Responsibilities: Minimal init (shared + fs only); connects to running yazi DDS server for IPC commands; manages plugin packages
+
+## Error Handling
+
+**Strategy:** `anyhow::Result<Data>` propagated through the actor chain; dispatcher logs errors at `warn` level and continues the loop — failures do not crash the app
+
+**Patterns:**
+- `act!` macro returns `Result<Data>`; callers can use `?` to propagate or `.ok()` to silently ignore
+- `succ!()` macro returns `Ok(Data::default())` — used to terminate actors that have nothing to return
+- `err!(expr)` macro logs expression result as a tracing `error` but does not propagate
+- `render!()` macro emits a `Render` event from within `succ!()` when state changed
+
+## Cross-Cutting Concerns
+
+**Logging:** `tracing` crate; level controlled via `YAZI_LOG` env var; initialized in `yazi-fm/src/logs.rs`
+
+**Validation:** Config validation happens at `yazi-config::init()` — parse errors show a blocking prompt then fall back to preset defaults
+
+**Authentication:** N/A for local mode; SFTP uses `russh` with key-based or password auth negotiated in `yazi-sftp/src/session.rs`
+
+**Concurrency model:** Single Tokio `LocalSet` thread owns `Core` and runs the event loop; all background I/O is spawned as regular `tokio::spawn` tasks and communicate back via `Event` channel
+
+---
+
+*Architecture analysis: 2026-03-21*

.planning/codebase/CONCERNS.md

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+# Codebase Concerns
+
+**Analysis Date:** 2026-03-21
+
+---
+
+## Tech Debt
+
+**SFTP URL rebase not implemented:**
+- Issue: `UrlBuf::rebase()` panics at runtime for SFTP URLs via `todo!()` macro — hardest-blocking panic
+- Files: `yazi-shared/src/url/buf.rs:166`
+- Impact: Any code path that calls `rebase()` on an SFTP URL will unconditionally panic at runtime
+- Fix approach: Implement the commented-out `Self::Sftp { loc: loc.rebase(base), domain: domain.clone() }` arm
+
+**`RwFile::metadata()` uses placeholder string for path:**
+- Issue: Both Tokio and SFTP arms pass the literal `"// FIXME"` string as the file path
+- Files: `yazi-vfs/src/provider/rw_file.rs:23-24`
+- Impact: Any metadata query on an open file returns incorrect path information; affects file attributes display
+- Fix approach: Capture and store the path when the file is opened; pass it through to `Cha::new()`
+
+**Splatter legacy `%*` shorthand pending removal:**
+- Issue: Three `// TODO: remove` comments mark the `%*` variant (maps to `visit_selected`) as deprecated; dead code kept for backward compat
+- Files: `yazi-fs/src/splatter.rs:85,158,247,346`
+- Impact: Bloated match arms, confusing maintenance; breaking change deferred
+- Fix approach: Remove `%*` handling after a deprecation grace period; update user-facing docs
+
+**`open_shell_compat` compatibility shim:**
+- Issue: Entire `OpenShellCompat` actor, `TasksProxy::open_shell_compat()`, and `match_and_open()` helper all carry `// TODO: remove` comments
+- Files: `yazi-actor/src/tasks/open_shell_compat.rs`, `yazi-proxy/src/tasks.rs:10`, `yazi-actor/src/mgr/open_do.rs:61`
+- Impact: Multiple call sites continue routing through legacy path instead of new `process_open`
+- Fix approach: Migrate all callers to use `TasksProxy::process_exec()` directly; delete the shim actor
+
+**`ProcessOpenOpt.spread` field marked for removal:**
+- Issue: `spread: bool` field carries `// TODO: remove` annotation in the parser type
+- Files: `yazi-parser/src/tasks/process_open.rs:17`
+- Impact: Dead struct field increasing complexity of every `ProcessOpenOpt` construction
+- Fix approach: Remove field; propagate removal to all construction sites in `mgr/shell.rs`, `mgr/open_do.rs`, `tasks/process_open.rs`
+
+**`ChaMode::is_exec()` deprecated but still in active use:**
+- Issue: Method carries `// TODO: deprecate` comment yet is called from `yazi-binding`, `yazi-config` theme code
+- Files: `yazi-fs/src/cha/mode.rs:153`, `yazi-binding/src/cha.rs:64`, `yazi-config/src/theme/is.rs:33`, `yazi-config/src/theme/icon.rs:66`
+- Impact: Deprecated API surface remains public and actively maintained
+- Fix approach: Determine replacement API, update callers, then remove method
+
+**`vfs::unique_name()` deprecated but infrastructure retained:**
+- Issue: `yazi_vfs::unique_name()` is deprecated in favour of `fs.unique()`; Lua wrapper still exposes `fs.unique_name()` with a deprecation warning at runtime
+- Files: `yazi-vfs/src/fns.rs:16`, `yazi-plugin/src/fs/fs.rs:234-241`
+- Impact: Duplicate code path; external plugins still using the old API receive runtime warnings
+- Fix approach: Track down plugin usages via community; remove API after sufficient migration time
+
+**`Data::into_any2()` has no satisfactory name:**
+- Issue: Method acknowledged as needing a better name in comment `// FIXME: find a better name`
+- Files: `yazi-shared/src/data/data.rs:233`
+- Impact: Poor discoverability in the `Data` API surface
+- Fix approach: Audit all callsites and rename; update callers
+
+**Multiple FIXME-annotated compat `impl AsRef` / `impl Default` on URL types:**
+- Issue: `LocBuf`, `UrlCow`, `UrlBuf`, `LocBuf` all carry `// FIXME: remove` impls that exist only for transitional compat
+- Files: `yazi-shared/src/loc/buf.rs:23`, `yazi-shared/src/url/cow.rs:21`, `yazi-shared/src/url/buf.rs:16`, `yazi-shared/src/loc/loc.rs:39`
+- Impact: These impls can mask type errors; they block further API hardening
+- Fix approach: Identify callers relying on these impls; replace with explicit conversions; remove impls
+
+**Lua `ya.select()` stub not implemented:**
+- Issue: `ya.select()` is registered but returns `Ok(())` unconditionally; body is a TODO placeholder
+- Files: `yazi-plugin/src/utils/sync.rs:126-128`
+- Impact: Any plugin that attempts to call `ya.select()` silently succeeds with no result; misleading API
+- Fix approach: Implement select semantics or return an explicit "not implemented" Lua error until complete
+
+**`spot:copy "line"` unimplemented:**
+- Issue: The `"line"` copy type in the spot view has an empty TODO body; no text is copied
+- Files: `yazi-actor/src/spot/copy.rs:28`
+- Impact: Silent no-op when user copies a line from spot view
+- Fix approach: Implement line extraction from the table widget
+
+**`ya.layer()` cursor and list fields unset:**
+- Issue: `cursor: None` and `list: Default::default()` in `ya.input()` / `ya.confirm()` carry `// TODO` comments indicating incomplete options plumbing
+- Files: `yazi-plugin/src/utils/layer.rs:57,89`
+- Impact: Plugins cannot programmatically position the cursor or pre-populate confirm lists via Lua
+- Fix approach: Thread these fields through `InputCfg` / `ConfirmCfg` from the Lua table argument
+
+**`WATCHER` semaphore acquire unwrap in file watcher:**
+- Issue: `WATCHER.acquire().await.unwrap()` can panic if the semaphore is closed during shutdown
+- Files: `yazi-watcher/src/local/local.rs:96`
+- Impact: Panics possible during clean shutdown sequence
+- Fix approach: Use `?` propagation or check for `SemaphoreAcquireError` explicitly
+
+---
+
+## Known Bugs
+
+**DDS `pub_inner_hi()` error silently swallowed:**
+- Symptoms: Peer hello messages fail without any error propagated or logged
+- Files: `yazi-dds/src/pubsub.rs:124-125`
+- Trigger: IPC transport error during initial hi broadcast
+- Workaround: None; failure is invisible
+
+**Watcher notification batching workaround:**
+- Symptoms: File change events are coalesced over 250 ms windows with batch size 1000 as an acknowledged workaround
+- Files: `yazi-watcher/src/local/local.rs:89`
+- Trigger: Comment says `// TODO: revert this once a new notification is implemented`; current impl is not the intended design
+- Workaround: Current behaviour is functional but has fixed latency overhead
+
+**LINKED returns Path type instead of Url:**
+- Symptoms: Symlink-based watch targets use an incorrect type, requiring an extra `Url::regular()` wrapping
+- Files: `yazi-watcher/src/reporter.rs:33-35`
+- Trigger: Any access to watched symlinked directories
+- Workaround: Current adapter in place but acknowledged as wrong
+
+**`UrlCov::parent()` not used in selection remove path:**
+- Symptoms: Parent traversal in `selected.rs` uses a manual workaround instead of the correct `UrlCov::parent()` API
+- Files: `yazi-core/src/tab/selected.rs:111`
+- Trigger: Removing selected files that have deep parent chains
+- Workaround: Manual `while let Some(u) = parent` loop
+
+---
+
+## Security Considerations
+
+**`unsafe std::env::set_var()` in async context:**
+- Risk: `set_var` is unsound in multi-threaded programs; marked `unsafe` in Rust 1.83+. Called from a `spawn_blocking` closure that runs concurrently with other threads reading the environment
+- Files: `yazi-fs/src/cwd.rs:101,108`, `yazi-dds/src/lib.rs:25-33`
+- Current mitigation: `unsafe` block is present acknowledging the risk; init happens early in `dds::init()`
+- Recommendations: Migrate environment variables to explicit `Arc<OsString>` passing or use `std::env::set_var` only before any threads are spawned
+
+**`str::from_utf8_unchecked()` without SAFETY comments:**
+- Risk: If upstream data is not validated as valid UTF-8 before calling the unchecked variant, memory safety of `str` references is violated
+- Files: `yazi-adapter/src/drivers/kgp.rs:360,366`, `yazi-adapter/src/drivers/kgp_old.rs:49,55`, `yazi-plugin/src/external/highlighter.rs:188`, `yazi-shared/src/strand/buf.rs:68,85,90`
+- Current mitigation: No `// SAFETY` comment explaining the invariant; workspace lint `missing_safety_doc = "allow"` suppresses the Clippy warning globally (`Cargo.toml:87`)
+- Recommendations: Add `// SAFETY:` comments to each site explaining why the bytes are valid UTF-8; re-enable `missing_safety_doc` lint
+
+**`missing_safety_doc` lint globally suppressed:**
+- Risk: All `unsafe fn` blocks in the workspace are exempt from documentation requirements
+- Files: `Cargo.toml:87`
+- Current mitigation: None
+- Recommendations: Remove `missing_safety_doc = "allow"` from workspace lints; fix each site
+
+---
+
+## Performance Bottlenecks
+
+**`Refresh::trigger_dirs()` acknowledged slow path:**
+- Problem: Spawns async tasks to stat and reload every visible folder on every refresh event; acknowledged in comment `// TODO: performance improvement`
+- Files: `yazi-actor/src/mgr/refresh.rs:44`
+- Cause: No caching layer; unconditional `Files::assert_stale()` and `Files::from_dir_bulk()` calls per folder
+- Improvement path: Track change timestamps and skip re-reads when stat hasn't changed; debounce refresh triggers
+
+**`icon()` method computes icon match on every call without caching:**
+- Problem: `yazi-actor/src/lives/file.rs:91` and `yazi-binding/src/file.rs:93` both call `THEME.icon.matches()` per file on every render with `// TODO: use a cache`
+- Files: `yazi-actor/src/lives/file.rs:91`, `yazi-binding/src/file.rs:93`
+- Cause: No memoization on `File` for the computed icon
+- Improvement path: Cache the icon result on the `File` struct after first computation; invalidate on theme reload
+
+**`Pos::to_rect()` caching absent:**
+- Problem: Rect computation from `Pos` has `// TODO: cache` comment indicating repeated recomputation
+- Files: `yazi-binding/src/elements/pos.rs:84`
+- Cause: No cached field
+- Improvement path: Store computed `Rect` alongside `Pos`; invalidate when terminal size changes
+
+**245 `.clone()` calls across the codebase:**
+- Problem: URL types (`UrlBuf`, `UrlCow`) are cloned pervasively; 126 `unwrap()`/`expect()` calls in non-test production code
+- Files: spread across all crates
+- Cause: URL types carry owned strings with no interning beyond the `Pool` for symbols; clone-heavy IPC message passing
+- Improvement path: Audit hot paths using `clone()` on URLs; leverage existing `UrlCow` borrow types where ownership is not needed
+
+---
+
+## Fragile Areas
+
+**`yazi-fs/src/splatter.rs` — shell argument expansion:**
+- Files: `yazi-fs/src/splatter.rs`
+- Why fragile: Multiple `unreachable!()` arms in `visit_hovered()`, `visit_dirname()` etc. that panic if the character dispatch logic in `visit()` is ever inconsistent; legacy `%*` arms awaiting removal add more match paths
+- Safe modification: Run full `cargo test -p yazi-fs` after any change; ensure all `visit_*` dispatch matches the `visit()` character table exactly
+- Test coverage: Inline `#[test]` block exists for basic cases; no exhaustive round-trip tests for all interpolation forms
+
+**`yazi-shared/src/url/` — URL type hierarchy:**
+- Files: `yazi-shared/src/url/url.rs`, `yazi-shared/src/url/buf.rs`, `yazi-shared/src/url/cow.rs`
+- Why fragile: Parallel enum hierarchies (`Url`, `UrlBuf`, `UrlCow`) must stay in sync; SFTP arm incomplete in `rebase()`; several compat `impl` blocks marked for removal; any variant addition requires changes in all three types plus `Loc`/`LocBuf`
+- Safe modification: Add variants to all three enums simultaneously; verify no `_ =>` arms silently absorb new variants; check all `From`/`Into` impls
+- Test coverage: Unit tests exist in `yazi-shared/src/url/buf.rs` and `cow.rs` but do not cover SFTP variant paths
+
+**`yazi-dds` — inter-process pub/sub:**
+- Files: `yazi-dds/src/pubsub.rs`, `yazi-dds/src/lib.rs`
+- Why fragile: Uses `unsafe { std::env::set_var }` during init; `pub_inner_hi()` silently ignores errors; global statics (`ID`, `PEERS`, `LOCAL`, `REMOTE`) initialized via `RoCell::init()` which panics on double-init
+- Safe modification: Only call `dds::init()` once before spawning any async tasks; never call from tests without isolation
+- Test coverage: No tests found in `yazi-dds/`
+
+**`yazi-adapter` — image protocol drivers:**
+- Files: `yazi-adapter/src/drivers/kgp.rs`, `yazi-adapter/src/drivers/kgp_old.rs`
+- Why fragile: Two parallel KGP driver implementations exist (current and `_old`); both use `str::from_utf8_unchecked()` without SAFETY docs; base64-encoded image data passed through format strings
+- Safe modification: Treat `kgp_old.rs` as read-only reference; do not add features there; changes to base64 chunking must preserve chunk boundary alignment
+- Test coverage: No unit tests found; runtime-only validation
+
+**`yazi-plugin/src/isolate/` — Lua plugin isolation:**
+- Files: `yazi-plugin/src/isolate/peek.rs`, `yazi-plugin/src/isolate/preload.rs`, `yazi-plugin/src/isolate/fetch.rs`, `yazi-plugin/src/isolate/spot.rs`
+- Why fragile: Uses `Handle::current().block_on()` which blocks the calling OS thread; if called from within an async context on the Tokio thread pool this starves the executor
+- Safe modification: Only invoke isolate entry points from dedicated `spawn_blocking` threads, never from `async` tasks directly
+- Test coverage: No unit tests; integration-tested only via running yazi
+
+---
+
+## Scaling Limits
+
+**Lua `ya.select()` stub:**
+- Current capacity: Not functional; always returns empty result
+- Limit: Any plugin relying on multi-item selection UI is broken
+- Scaling path: Implement in `yazi-plugin/src/utils/sync.rs`
+
+**File watcher batch size hardcoded at 1000:**
+- Current capacity: 1000 change events per 250 ms window
+- Limit: Repositories or directories with high churn (e.g., build output) may overwhelm the batch and drop events
+- Scaling path: Make `chunks_timeout` size/duration configurable; implement proper OS-level coalescing
+
+---
+
+## Dependencies at Risk
+
+**`ratatui` unstable features:**
+- Risk: Uses `unstable-rendered-line-info` and `unstable-widget-ref` feature flags; these APIs can break without a semver guarantee between minor ratatui versions
+- Impact: Build breaks or behavioural regressions on ratatui upgrades
+- Migration plan: Track ratatui changelog; stabilisation of these features is planned upstream but no ETA
+
+**`mlua` with Lua 5.5:**
+- Risk: `lua55` feature targets Lua 5.5 which is not yet a stable release; API changes between Lua 5.5 preview builds could require code updates
+- Impact: `yazi-plugin` and `yazi-binding` crates rely on Lua 5.5 semantics
+- Migration plan: Pin to a tested mlua version; test against new Lua 5.5 release candidates in CI
+
+---
+
+## Test Coverage Gaps
+
+**`yazi-dds` — zero tests:**
+- What's not tested: IPC message serialization, pub/sub routing, peer discovery, all `pubsub.rs` paths
+- Files: `yazi-dds/src/pubsub.rs`, `yazi-dds/src/client.rs`, `yazi-dds/src/server.rs`
+- Risk: Silent regressions in cross-instance communication; `pub_inner_hi()` error swallowing undetected
+- Priority: High
+
+**`yazi-adapter` — zero tests:**
+- What's not tested: All image protocol drivers (KGP, KGP-old, Sixel, IIP, Ueberzug), ICC colour transform, image encoding
+- Files: `yazi-adapter/src/drivers/`, `yazi-adapter/src/icc.rs`
+- Risk: Image rendering regressions not caught until runtime
+- Priority: High
+
+**`yazi-vfs` SFTP provider paths — sparse tests:**
+- What's not tested: `RwFile` metadata with SFTP, `try_absolute()` for archive URLs, SFTP-specific `Cha` conversion
+- Files: `yazi-vfs/src/provider/rw_file.rs`, `yazi-vfs/src/provider/provider.rs`
+- Risk: Archive and SFTP URL handling silently broken; placeholder `"// FIXME"` path in production unnoticed
+- Priority: High
+
+**`yazi-actor` core actions — partial tests:**
+- What's not tested: `bulk_rename` cycle detection edge cases, `open_do::match_and_open()` legacy path, `spot::copy "line"` variant
+- Files: `yazi-actor/src/mgr/bulk_rename.rs`, `yazi-actor/src/mgr/open_do.rs`, `yazi-actor/src/spot/copy.rs`
+- Risk: Silent regressions in file operations; no-op copy undetected
+- Priority: Medium
+
+**Only 23 of 912 Rust source files contain tests (~2.5%):**
+- What's not tested: The vast majority of crate logic including scheduler, config parsing, most of the actor layer, watcher, and binding
+- Files: All crates except `yazi-shared`, `yazi-fs`, `yazi-core` (partial), `yazi-config` (partial)
+- Risk: Wide surface area for undetected regressions; TDD mandate in CLAUDE.md is not yet reflected in coverage
+- Priority: High
+
+---
+
+*Concerns audit: 2026-03-21*

.planning/codebase/CONVENTIONS.md

@@ -0,0 +1,175 @@
+# Coding Conventions
+
+**Analysis Date:** 2026-03-21
+
+## Naming Patterns
+
+**Files:**
+- `snake_case.rs` for all Rust source files
+- Module directories named after the concept they contain (e.g., `yazi-shared/src/url/`, `yazi-fs/src/path/`)
+- Error types live in dedicated `error.rs` or `error/` files per crate
+- Config presets in `preset/` subdirectories
+
+**Structs and Enums:**
+- `PascalCase` for all types: `UrlBuf`, `LocBuf`, `Backstack`, `Selected`, `SchemeCow`
+- `Buf`-suffixed types are owned buffers; reference types use the bare name (e.g., `Url` vs `UrlBuf`, `Loc` vs `LocBuf`)
+- `Cow`-suffixed types are clone-on-write wrappers (e.g., `UrlCow`, `SchemeCow`, `PathCow`)
+- Error enums use `Error` suffix with domain prefix: `PathDynError`, `StripPrefixError`, `SetNameError`
+
+**Functions:**
+- `snake_case` for all functions and methods
+- Boolean getters often use `is_` prefix: `is_empty()`, `is_dir()`, `is_local()`, `is_regular()`
+- Public accessor stubs that return a borrowed view often match the field name: `uri()`, `urn()`, `base()`, `trail()`
+- Fallible constructors use `try_` prefix: `try_join()`, `try_set_name()`, `try_strip_prefix()`
+- Conversion constructors named by intent: `zeroed()`, `floated()`, `saturated()`, `from_components()`
+- Async variants of sync functions stay named the same (not `_async` suffixed)
+
+**Variables:**
+- `snake_case`, single-letter names only for iterators (`i`, `c`, `b`) and closures
+- Avoid abbreviations; prefer `url`, `path`, `domain` over `u`, `p`, `d` in function signatures
+- Tuple/temporary intermediate values named `a`, `b` when context is obvious
+
+**Traits:**
+- `PascalCase`; `Able` suffix for marker/capability traits: `LocAble`, `LocBufAble`, `Splatable`
+- `Like` suffix for view-oriented traits: `UrlLike`, `PathLike`, `SchemeLike`, `StrandLike`
+- `As` prefix for conversion traits: `AsUrl`, `AsPath`, `AsScheme`, `AsStrand`
+
+**Constants and Statics:**
+- `UPPER_SNAKE_CASE` for statics: `ADAPTOR`, `WSL`, `WATCHED`, `WATCHER`
+- Associated constants inside `impl` use `UPPER_SNAKE_CASE`: `const NAME: &str = "bulk_rename"`
+
+## Code Style
+
+**Formatting:**
+- Tool: `rustfmt` (nightly toolchain required)
+- Config: `rustfmt.toml` at repo root
+- Hard tabs for indentation (not spaces)
+- Tab width: 2 spaces equivalent
+- Edition 2024 style
+- Imports grouped: std → external crates → workspace crates (via `group_imports = "StdExternalCrate"`)
+- Imports within a group horizontally collapsed: `use std::{borrow::Cow, ffi::OsStr, ...}`
+- One-liner functions on a single line when possible (`fn_single_line = true`)
+- Struct field alignment enabled up to 99 chars: fields visually aligned with spaces
+
+**Linting:**
+- Tool: Clippy (stable)
+- Config: `[workspace.lints.clippy]` in `Cargo.toml`
+- `format_push_string = "warn"` – avoid `push_str(&format!(...))`, use `write!` instead
+- `implicit_clone = "warn"` – `.to_owned()` or `.clone()` must be explicit
+- `use_self = "warn"` – use `Self` instead of the concrete type name inside `impl` blocks
+- `if_same_then_else = "allow"` – duplicate branches permitted
+- `module_inception = "allow"` – `mod foo { struct Foo }` pattern is allowed
+
+**Lua:**
+- Tool: StyLua
+- Config: `stylua.toml` at repo root
+- Lua 5.4 syntax
+- Indent width: 2 spaces
+- `call_parentheses = "NoSingleTable"` – omit parentheses when the only argument is a table
+- `sort_requires = true` – `require()` calls are sorted alphabetically
+
+## Import Organization
+
+**Rust order (enforced by rustfmt):**
+1. `std` / `core` / `alloc`
+2. External crates (e.g., `anyhow`, `mlua`, `tokio`)
+3. Workspace crates (e.g., `yazi_shared`, `yazi_fs`)
+4. Local / crate-internal: `crate::`, `super::`, `self::`
+
+**Path Aliases:**
+- No `use` aliases used in production code; type aliases via `type` declaration where needed
+- In tests, `use super::*` is the universal import pattern
+
+**Module Export Pattern:**
+- `yazi_macro::mod_pub!(a b c)` – re-exports submodules as `pub mod` (subdirectories visible)
+- `yazi_macro::mod_flat!(a b c)` – makes private `mod` items `pub use`d flat into current namespace
+- Avoids manual `mod x; pub use x::*;` repetition throughout all crates
+
+## Error Handling
+
+**Boundary strategy:**
+- Functions that can fail return `anyhow::Result<T>` at application layer (actors, async tasks)
+- Domain-specific errors use `thiserror::Error`-derived enums with precise variants (see `yazi-shared/src/path/error.rs`, `yazi-shared/src/strand/error.rs`)
+- Error propagation uses `?` operator; `.context()` added where clarification helps
+- `bail!()` from `anyhow` used for early failure with message
+- `ensure!()` from `anyhow` used for condition checks
+
+**Error macro (`err!`):**
+- `yazi_macro::err!(expr)` – logs error via `tracing::error!` and discards result; used for fire-and-forget side effects
+- `yazi_macro::err!(expr, "fmt {}", args)` – same but with custom message
+- Do NOT use `unwrap()` in production code; `expect("message")` is acceptable only when invariant is guaranteed
+- `debug_assert!(...)` used inside `impl` blocks to verify post-conditions cheaply
+
+**Panics:**
+- `unreachable!()` used only inside exhaustive match arms that should logically never be hit
+- `expect("...")` used in constructors/init code where failure means programmer error
+
+## Logging
+
+**Framework:** `tracing` crate
+
+**Import pattern:**
+```rust
+use tracing::{debug, error, warn};
+// or targeted:
+use tracing::error;
+```
+
+**Patterns:**
+- `tracing::error!(...)` – non-recoverable errors in async tasks
+- `tracing::warn!(...)` – degraded state that can continue
+- `tracing::debug!(...)` – diagnostic information (only in debug builds via `max_level_debug`)
+- `yazi_macro::err!(expr)` – shorthand to log and discard a `Result::Err`
+- `yazi_macro::time!(expr)` – wraps an expression in a debug-level timing log
+- Log level controlled at runtime via `YAZI_LOG` environment variable
+
+## Comments
+
+**When to Comment:**
+- Inline comments explain WHY, not WHAT: `// Only keep 30 URLs before the cursor, the cleanup threshold is 60`
+- Code sections within large files use `// ---` separator lines: `// --- Tuple`, `// --- Tests`
+- Platform-conditional code annotated: `// "/" is both a directory separator and the root directory per se`
+- Pending work uses `// TODO:` or `// FIXME:` markers (not `//TODO:`)
+
+**Doc comments (`///`):**
+- Used only on public API items with non-obvious contracts
+- CLI arguments all have `///` docs (powers `--help` output via `clap`)
+- Internal implementation functions rarely have doc comments
+
+**Commented-out code:**
+- Not present; dead code is removed immediately
+
+## Function Design
+
+**Size:** Typically 5–25 lines; business logic delegated to private helpers
+
+**Parameters:** Max 3 in most cases; larger argument sets use an Options struct (e.g., `BulkRenameOpt`, `ShowOpt`)
+
+**Return Values:**
+- `Option<T>` for absence; `Result<T>` for failure
+- `bool` return for mutation success/failure: `add()`, `remove()` on `Selected`
+- Avoid `(bool, T)` tuples; use named return types or structs
+
+**Boolean Parameters:**
+- Avoided in public APIs; use enums or named Options structs instead
+- Acceptable in private helpers when the call site is immediately adjacent
+
+## Module Design
+
+**Exports:**
+- All crates have a `pub fn init()` entry point for global state initialization
+- Each crate exposes a flat public API via `mod_flat!` – callers do not need to know internal module layout
+- Sub-namespaces exposed via `mod_pub!` when logical grouping is useful (e.g., `elements/`, `path/`)
+
+**Barrel Files:**
+- `lib.rs` serves as the crate root; uses macros instead of manual barrel re-exports
+- No separate `mod.rs` barrel files – directory modules are declared in `lib.rs`
+
+**Struct Internals:**
+- Private fields by default; getters expose them where needed
+- `pub(super)` used for intra-module access (e.g., `pub(super) inner`, `pub(super) area`)
+- Newtype pattern common for domain types: `struct Backstack { cursor: usize, stack: Vec<UrlBuf> }`
+
+---
+
+*Convention analysis: 2026-03-21*

.planning/codebase/INTEGRATIONS.md

@@ -0,0 +1,208 @@
+# External Integrations
+
+**Analysis Date:** 2026-03-21
+
+## APIs & External Services
+
+**None (network-based APIs):**
+- Yazi is a local terminal file manager. It does not call any external web APIs or cloud services at runtime.
+- All "integrations" are protocol-level or subprocess-based.
+
+## SSH / SFTP
+
+**SSH/SFTP Protocol:**
+- Implementation: `yazi-sftp/` crate
+- SDK/Client: `russh` 0.57.1 (pure-Rust SSH2 implementation, ring + rsa features)
+- Purpose: Browse and operate on remote filesystems over SFTP
+- Session management: `yazi-sftp/src/session.rs` — async session with per-request oneshot callbacks
+- Protocol: Custom SFTP packet serialization/deserialization in `yazi-sftp/src/ser.rs`, `de.rs`
+- Auth: SSH key-based (RSA supported via `russh`); no env var required, handled by SSH session negotiation
+- VFS integration: Remote paths handled by `typed-path` for cross-platform path normalization
+
+## Image Display Protocols
+
+**Terminal Image Rendering (`yazi-adapter/`):**
+
+Yazi probes the terminal emulator and selects the best supported image protocol:
+
+| Protocol | Driver file | Terminals |
+|---|---|---|
+| Kitty Graphics Protocol (KGP) | `yazi-adapter/src/drivers/kgp.rs` | Kitty, Ghostty |
+| KGP Old (chunked) | `yazi-adapter/src/drivers/kgp_old.rs` | Konsole, Warp |
+| iTerm2 Inline Protocol (IIP) | `yazi-adapter/src/drivers/iip.rs` | iTerm2, WezTerm, VSCode, Tabby, Hyper, Mintty, Rio, Bobcat |
+| Sixel | `yazi-adapter/src/drivers/sixel.rs` | Foot, Microsoft Terminal, BlackBox, VSCode, Rio, Bobcat |
+| Ueberzug++ | `yazi-adapter/src/drivers/ueberzug.rs` | Fallback via external process |
+| Chafa | `yazi-adapter/src/drivers/chafa.rs` | Default fallback (text-mode rendering) |
+
+Detection logic: `yazi-adapter/src/adapters.rs` — maps `yazi_emulator::Brand` enum to adapter list.
+
+**ICC Color Management:**
+- `moxcms` 0.8.1 — reads embedded ICC profiles from images
+- `palette` 0.7.6 — color space conversion
+- `quantette` 0.5.1 — color quantization for Sixel/Chafa output
+
+## Terminal Emulator Detection
+
+**Emulator Database (`yazi-emulator/`):**
+- Detects running terminal via escape sequence queries and environment variables
+- Recognized brands: Kitty, Konsole, iTerm2, WezTerm, Foot, Ghostty, Microsoft Terminal, Warp, Rio, BlackBox, VSCode, Tabby, Hyper, Mintty, Tmux, VTerm, Apple Terminal, Urxvt, Bobcat
+- Light/dark theme detection feeds into `yazi-config` flavor selection
+- Tmux multiplexer passthrough handled via `yazi-adapter/src/lib.rs`
+- WSL detection via `yazi_shared::in_wsl()`
+
+## Data Storage
+
+**Databases:**
+- None (no embedded database)
+
+**File Storage:**
+- Local filesystem only, via Rust standard library and `yazi-fs/` crate
+- Trash/recycle bin: `trash` 5.2.5 crate (all non-Android platforms) in `yazi-fs/`
+- Preview image cache: configurable directory via `preview.cache_dir` in `yazi-config/preset/yazi-default.toml`
+
+**Caching:**
+- In-process LRU cache: `lru` 0.16.3 in `yazi-scheduler/`
+- No external cache service
+
+## Plugin System
+
+**Lua Plugin System (`yazi-plugin/`):**
+- Runtime: Lua 5.5 embedded via `mlua` 0.11.6 (vendored by default)
+- Prebuilt assets: `yazi-prebuilt` 0.1.0 crate bundles compiled Lua plugins
+- Built-in plugins: `yazi-plugin/preset/plugins/` — archive, code, dds, image, video, pdf, svg, json, font, fzf, zoxide, mime, session, vfs, etc.
+- Plugin API exposed as `ya` global in Lua; see `yazi-plugin/preset/ya.lua`
+- Async plugin execution via `ya.co()` coroutine API
+
+## Data Distribution Service (DDS)
+
+**Inter-process Communication (`yazi-dds/`):**
+- Purpose: Communication between multiple yazi instances (e.g., nesting, shell integration)
+- Transport: Unix domain socket (or named pipe on Windows), using Tokio async I/O
+- Protocol: JSON-serialized messages (`serde_json`)
+- Environment variables set/read: `YAZI_ID`, `YAZI_PID`, `YAZI_LEVEL`
+- Build embeds git metadata via `vergen-gitcl`
+
+## Shell Integration
+
+**CLI Tool (`yazi-cli/` → binary `ya`):**
+- Shell completion generated at build time for: bash, zsh, fish, elvish, nushell, fig
+- Libraries: `clap_complete` 4.6.0, `clap_complete_nushell` 4.6.0, `clap_complete_fig` 4.5.2
+- `ya pub` / `ya emit` commands for DDS messaging from shell scripts
+
+## Filesystem Watching
+
+**File Watcher (`yazi-watcher/`):**
+- Library: `notify` 8.2.0 with `macos_fsevent` feature
+- macOS: FSEvents API via feature flag
+- Linux: inotify (via notify default backend)
+- Windows: ReadDirectoryChanges (via notify default backend)
+
+## External Programs (Subprocess Integrations)
+
+Yazi shells out to external programs configured in `yazi-config/preset/yazi-default.toml`. These are not hard dependencies but expected to be present in `$PATH`:
+
+**File Operations:**
+- `$EDITOR` / `vi` — text editing
+- `code` — VS Code editor (Windows)
+- `xdg-open` — open files (Linux)
+- `open` — open files (macOS)
+- `termux-open` — open files (Android)
+
+**Media:**
+- `mediainfo` — media file metadata display
+- `exiftool` — EXIF data display
+
+**Archives:**
+- Handled internally via `ya pub extract` (DDS command)
+
+**Fuzzy Finder:**
+- `fzf` — optional, via `yazi-plugin/preset/plugins/fzf.lua`
+
+**Directory Jumping:**
+- `zoxide` — optional, via `yazi-plugin/preset/plugins/zoxide.lua`
+
+**Image Fallback:**
+- `ueberzug++` — external process fallback for image display
+- `chafa` — text-mode image rendering fallback
+
+**Video Preview:**
+- External video thumbnailing via `yazi-plugin/preset/plugins/video.lua`
+
+**PDF Preview:**
+- External PDF rendering via `yazi-plugin/preset/plugins/pdf.lua`
+
+**SVG Preview:**
+- External SVG rendering via `yazi-plugin/preset/plugins/svg.lua`
+
+**Font Preview:**
+- `yazi-plugin/preset/plugins/font.lua`
+
+## Authentication & Identity
+
+**Auth Provider:**
+- None (no user accounts or auth service)
+- SSH auth for SFTP handled by `russh` (key-based)
+
+## Monitoring & Observability
+
+**Error Tracking:**
+- None (no external error tracking service)
+
+**Logging:**
+- `tracing` 0.1.44 framework with `tracing-subscriber` 0.3.23
+- Log appender: `tracing-appender` 0.2.4 writes to file
+- Max log level: `debug` in both dev and release builds (via `max_level_debug` and `release_max_level_debug` features)
+- Configurable via `RUST_LOG` environment variable (env-filter feature)
+
+**Panic Handling:**
+- `better-panic` 0.3.0 in `yazi-fm/` for improved panic display
+
+## CI/CD & Deployment
+
+**Hosting:**
+- GitHub Releases (binary archives per platform/arch)
+- Snap Store (Linux, via `snap/`)
+- Winget (Windows Package Manager)
+- Nix (via `flake.nix` and nixpkgs)
+
+**CI Pipeline:**
+- GitHub Actions (`.github/workflows/`)
+  - `test.yml` — build + `cargo test --workspace` on Ubuntu, Windows, macOS
+  - `check.yml` — clippy (stable), rustfmt (nightly), stylua
+  - `publish.yml` — on release: publish to Winget and Snap Store
+  - `cachix.yml` — Nix binary cache
+  - `draft.yml` — release draft automation
+  - `lock.yml` — dependency lock file updates
+- Build cache: `sccache` via `mozilla-actions/sccache-action`
+
+**Release Distribution:**
+- Binary installs via `cargo-binstall` (metadata in `[package.metadata.binstall]`)
+- Archive naming: `yazi-{target}.{archive-suffix}` from GitHub Releases
+
+## Webhooks & Callbacks
+
+**Incoming:**
+- None
+
+**Outgoing:**
+- None
+
+## Environment Configuration
+
+**Required for build:**
+- Rust stable toolchain (MSRV 1.92.0)
+- `MACOSX_DEPLOYMENT_TARGET=10.12` (set automatically via `.cargo/config.toml`)
+
+**Required for CI secrets:**
+- `WINGET_TOKEN` — publishing to Windows Package Manager
+- `SNAPCRAFT_TOKEN` — publishing to Snap Store
+- `GITHUB_TOKEN` — stylua action authentication
+
+**Optional runtime:**
+- `EDITOR` — preferred text editor (falls back to `vi`)
+- `YAZI_CONFIG_HOME` — override config directory
+- `RUST_LOG` — log level filter
+
+---
+
+*Integration audit: 2026-03-21*

.planning/codebase/STACK.md

@@ -0,0 +1,146 @@
+# Technology Stack
+
+**Analysis Date:** 2026-03-21
+
+## Languages
+
+**Primary:**
+- Rust 2024 edition - All core crates (`yazi-fm/`, `yazi-cli/`, `yazi-core/`, all `yazi-*` crates)
+
+**Secondary:**
+- Lua 5.5 (embedded via mlua) - Plugin system (`yazi-plugin/preset/plugins/*.lua`, `yazi-plugin/preset/ya.lua`)
+- Nix - Development environment and packaging (`flake.nix`, `nix/`)
+- TOML - Configuration format (`yazi-config/preset/*.toml`)
+
+## Runtime
+
+**Environment:**
+- Native binary, no runtime required
+- Platform targets: Linux, macOS, Windows, Android (via Termux)
+- WSL (Windows Subsystem for Linux) supported with special detection logic
+
+**Package Manager:**
+- Cargo (Rust)
+- Lockfile: `Cargo.lock` (present, committed)
+
+## Frameworks
+
+**Core:**
+- `ratatui` 0.30.0 - TUI rendering framework (used in `yazi-fm/`, `yazi-widgets/`, `yazi-adapter/`)
+- `crossterm` 0.29.0 - Cross-platform terminal I/O, with `use-dev-tty` on macOS
+- `tokio` 1.50.0 (full features) - Async runtime powering the entire application
+
+**Lua Embedding:**
+- `mlua` 0.11.6 - Lua 5.5 embedding with `async`, `anyhow`, `serde`, `macros` features
+- `vendored-lua` feature flag bundles Lua at compile time (default)
+
+**Serialization:**
+- `serde` 1.0.228 with derive - universal serialization
+- `serde_json` 1.0.149 - JSON for DDS protocol
+- `toml` 1.0.6 - Configuration file parsing
+- `serde_with` 3.18.0 - Advanced serde helpers
+
+**Build/Dev:**
+- `rustfmt` nightly - Code formatting (`rustfmt.toml`)
+- `clippy` stable - Linting (rules in root `Cargo.toml` `[workspace.lints.clippy]`)
+- `stylua` latest - Lua code formatting (`stylua.toml`, Lua 5.4 syntax target)
+- `vergen-gitcl` 9.1.0 - Build-time git metadata embedding (in `yazi-dds`, `yazi-cli` build scripts)
+- `sccache` - Build caching in CI
+
+## Key Dependencies
+
+**Critical:**
+- `mlua` 0.11.6 - Lua plugin system; entire extensibility model depends on this
+- `ratatui` 0.30.0 - All UI rendering; uses unstable features `unstable-rendered-line-info`, `unstable-widget-ref`
+- `tokio` 1.50.0 - All async I/O; scheduler, watcher, DDS, SFTP all depend on it
+- `russh` 0.57.1 - SSH/SFTP client (ring + rsa features) used in `yazi-sftp/`
+
+**Image Rendering:**
+- `image` 0.25.10 - Image decoding (avif, bmp, dds, exr, gif, hdr, ico, jpeg, png, pnm, qoi, tga, tiff, webp) in `yazi-adapter/`
+- `moxcms` 0.8.1 - ICC color management in `yazi-adapter/`
+- `palette` 0.7.6 - Color manipulation in `yazi-adapter/`
+- `quantette` 0.5.1 - Color quantization in `yazi-adapter/`
+
+**Syntax Highlighting:**
+- `syntect` 5.3.0 - Syntax highlighting with `plist-load` and `regex-onig` features in `yazi-plugin/`
+
+**Filesystem:**
+- `notify` 8.2.0 - Filesystem watching with `macos_fsevent` feature in `yazi-watcher/`
+- `trash` 5.2.5 - Cross-platform trash/recycle bin (all non-Android targets) in `yazi-fs/`
+- `typed-path` 0.12.3 - Cross-platform path handling (for SFTP and VFS)
+
+**Performance:**
+- `tikv-jemallocator` 0.6.1 - jemalloc allocator on non-macOS/non-Windows (configured in `.cargo/config.toml`)
+- `parking_lot` 0.12.5 - Fast mutexes and RwLocks throughout
+- `foldhash` 0.2.0 - Fast hash function
+- `hashbrown` 0.16.1 - Fast hash maps
+- `lru` 0.16.3 - LRU cache in `yazi-scheduler/`
+- `twox-hash` 2.1.2 - xxHash3_128 for content hashing
+
+**Utility:**
+- `anyhow` 1.0.102 - Error handling throughout
+- `thiserror` 2.0.18 - Error type derivation
+- `clap` 4.6.0 - CLI argument parsing in `yazi-cli/`, `yazi-boot/`
+- `clap_complete`, `clap_complete_nushell`, `clap_complete_fig` - Shell completion generation
+- `chrono` 0.4.44 - Date/time
+- `regex` 1.12.3 - Regular expressions
+- `globset` 0.4.18 - Glob pattern matching for file rules
+- `percent-encoding` 2.3.2 - URL encoding for VFS paths
+- `base64` 0.22.1 - Encoding for image protocols
+- `rand` 0.9.2 - Random number generation
+- `tracing` 0.1.44 + `tracing-subscriber` 0.3.23 - Structured logging
+- `tracing-appender` 0.2.4 - Log file appending
+- `async-priority-channel` 0.2.0 - Priority task queue in `yazi-scheduler/`
+- `yazi-prebuilt` 0.1.0 - Prebuilt Lua plugin assets bundled into `yazi-plugin/`
+
+**Platform-specific:**
+- `libc` 0.2.183 - Unix FFI (Linux, macOS)
+- `uzers` 0.12.2 - Unix user/group info (Linux, macOS)
+- `windows-sys` 0.61.2 - Windows API bindings (Windows; JobObjects, Storage, UI Shell)
+- `core-foundation-sys` 0.8.7 - macOS CoreFoundation (macOS only)
+- `objc2` 0.6.4 - Objective-C bindings (macOS only, `yazi-fs/`)
+- `signal-hook-tokio` 0.4.0 - Unix signal handling in `yazi-fm/`
+
+## Configuration
+
+**Environment:**
+- No `.env` files; configured through TOML files placed in XDG config dirs
+- Runtime env vars used: `YAZI_ID`, `YAZI_LEVEL`, `YAZI_PID`, `EDITOR`, `YAZI_CONFIG_HOME`
+- Build-time env via `.cargo/config.toml`: `MACOSX_DEPLOYMENT_TARGET=10.12`, jemalloc settings
+
+**Build:**
+- Root `Cargo.toml` - Workspace manifest with centralized dependency versions
+- `.cargo/config.toml` - Allocator config, macOS deployment target, aarch64 CPU flags
+- `rustfmt.toml` - Formatter config (nightly, hard tabs, 2-space tab width, Unix newlines)
+- `stylua.toml` - Lua formatter config (Lua 5.4 syntax, 2-space indent)
+
+**Configuration files (user-facing):**
+- `yazi-config/preset/yazi-default.toml` - Manager, preview, opener, open rules
+- `yazi-config/preset/keymap-default.toml` - Keybindings
+- `yazi-config/preset/theme-dark.toml`, `theme-light.toml` - Color themes
+- `yazi-config/preset/vfs-default.toml` - Virtual filesystem settings
+
+## Build Profiles
+
+**dev:** Line-tables debug info only; dependencies built without debug info
+**release:** LTO=fat, codegen-units=1, panic=abort, strip=true
+**release-windows:** Inherits release but panic=unwind
+**dev-opt:** Release settings but 256 codegen-units, incremental=true, LTO off
+
+## Platform Requirements
+
+**Development:**
+- Rust stable toolchain (minimum MSRV 1.92.0)
+- Rust nightly for `rustfmt` formatting only
+- `stylua` for Lua formatting
+- Nix (optional, via `flake.nix` for reproducible dev shell)
+
+**Production:**
+- Self-contained binary; no runtime dependencies beyond system libc
+- Platforms: Linux x86_64/aarch64, macOS x86_64/aarch64 (min 10.12), Windows x86_64/aarch64
+- jemalloc linked statically on Linux; system allocator on macOS/Windows
+- Apple M1 optimized build via `-Ctarget-cpu=apple-m1` rustflag
+
+---
+
+*Stack analysis: 2026-03-21*

.planning/codebase/STRUCTURE.md

@@ -0,0 +1,256 @@
+# Codebase Structure
+
+**Analysis Date:** 2026-03-21
+
+## Directory Layout
+
+```
+yazi/                           # Workspace root
+├── Cargo.toml                  # Workspace manifest, centralized deps, clippy rules
+├── Cargo.lock                  # Lockfile (committed)
+├── rustfmt.toml                # Hard tabs, nightly formatting features
+├── stylua.toml                 # Lua formatter config (for plugin files)
+├── .cargo/config.toml          # jemalloc global allocator, linker flags
+├── assets/                     # Icons, screenshots, misc assets
+├── scripts/                    # Dev utilities (icon validation, form scripts)
+├── nix/                        # Nix flake derivations
+├── snap/                       # Snapcraft packaging
+├── .github/                    # CI workflows, issue templates
+├── .planning/                  # GSD planning documents (not shipped)
+│
+├── yazi-fm/                    # BINARY: main file manager (default workspace member)
+├── yazi-cli/                   # BINARY: `ya` CLI tool (default workspace member)
+│
+├── yazi-actor/                 # Actor trait + all command implementations
+├── yazi-adapter/               # Terminal image protocol adapters (kgp/sixel/iip/chafa/ueberzug)
+├── yazi-binding/               # Lua ↔ Rust type bindings (mlua UserData)
+├── yazi-boot/                  # CLI arg parsing (clap), boot configuration
+├── yazi-build/                 # Build-time code generation helper binary
+├── yazi-codegen/               # Proc-macro support crate
+├── yazi-config/                # Config parsing (yazi.toml, keymap.toml, theme.toml)
+├── yazi-core/                  # Core state structs (Core, Mgr, Tab, Tasks, overlays)
+├── yazi-dds/                   # IPC pub/sub server (Unix socket, multi-instance)
+├── yazi-emulator/              # Terminal emulator detection (brand, dimensions)
+├── yazi-ffi/                   # macOS FFI bindings (CoreFoundation, IOKit, DiskArbitration)
+├── yazi-fs/                    # Filesystem abstractions (File, Files, sorting, filtering)
+├── yazi-macro/                 # Proc-macros (act!, emit!, succ!, mod_pub!, mod_flat!, render!, ...)
+├── yazi-packing/               # Plugin packaging utilities
+├── yazi-parser/                # Options structs for every action (parsed from ActionCow)
+├── yazi-plugin/                # Lua runtime, plugin loader, isolate sandboxing
+├── yazi-proxy/                 # Fire-and-forget action emitters for async contexts
+├── yazi-scheduler/             # Task runner (file ops, preload, fetch, plugin, process workers)
+├── yazi-sftp/                  # SFTP client (russh-based remote filesystem)
+├── yazi-shared/                # Shared primitives (Event, Layer, Id, RoCell, URL types, ...)
+├── yazi-shim/                  # Patches/shims for crossterm and ratatui
+├── yazi-term/                  # Ratatui Terminal wrapper with partial-render support
+├── yazi-tty/                   # Raw TTY handle (separate from ratatui for direct writes)
+├── yazi-vfs/                   # Virtual filesystem (local + SFTP provider abstraction)
+└── yazi-watcher/               # Filesystem watcher (local inotify/FSEvents + remote polling)
+```
+
+## Directory Purposes
+
+**`yazi-fm/src/`:**
+- Purpose: Binary crate for the main `yazi` process
+- Contains: `main.rs`, `App` event loop, `Dispatcher`, `Router`, `Executor`, `Root` renderer, per-overlay UI widgets
+- Key files: `yazi-fm/src/main.rs`, `yazi-fm/src/app/app.rs`, `yazi-fm/src/dispatcher.rs`, `yazi-fm/src/executor.rs`, `yazi-fm/src/router.rs`, `yazi-fm/src/root.rs`
+
+**`yazi-cli/src/`:**
+- Purpose: Binary crate for the `ya` companion CLI
+- Contains: `main.rs`, `args.rs`, command handlers for `emit`, `emit-to`, `pub`, `pub-to`, `sub`, `pkg`
+- Key files: `yazi-cli/src/main.rs`, `yazi-cli/src/package/`
+
+**`yazi-actor/src/`:**
+- Purpose: All command/action implementations; the `Actor` trait definition; `Ctx` context struct; `Lives` Lua scope manager
+- Sub-directories: `app/` (15 actors), `mgr/` (~60 actors), `cmp/`, `confirm/`, `help/`, `input/`, `notify/`, `pick/`, `spot/`, `tasks/`, `which/`, `lives/`, `core/`
+- Key files: `yazi-actor/src/actor.rs`, `yazi-actor/src/context.rs`, `yazi-actor/src/lives/lives.rs`
+
+**`yazi-core/src/`:**
+- Purpose: Pure state structs; no I/O, no async; mutated only by actors via `Ctx`
+- Sub-directories: `mgr/` (Mgr, Tabs, Yanked, Mimetype), `tab/` (Tab, Folder, Preview, Finder, Selected, History, Backstack, Mode), `tasks/`, `cmp/`, `confirm/`, `help/`, `input/`, `notify/`, `pick/`, `spot/`, `which/`
+- Key files: `yazi-core/src/core.rs`, `yazi-core/src/mgr/mgr.rs`, `yazi-core/src/tab/tab.rs`
+
+**`yazi-config/src/`:**
+- Purpose: TOML config parsing; exposes global `static` values (`YAZI`, `KEYMAP`, `THEME`, `LAYOUT`)
+- Sub-directories: `keymap/`, `mgr/`, `open/`, `opener/`, `plugin/`, `popup/`, `preview/`, `tasks/`, `theme/`, `vfs/`, `which/`
+- Key files: `yazi-config/src/lib.rs`, `yazi-config/preset/yazi-default.toml`, `yazi-config/preset/keymap-default.toml`
+
+**`yazi-config/preset/`:**
+- Purpose: Embedded default configurations shipped with the binary
+- Contains: `yazi-default.toml`, `keymap-default.toml`, `theme-dark.toml`, `theme-light.toml`, `vfs-default.toml`
+
+**`yazi-shared/src/`:**
+- Purpose: Cross-crate primitives with no domain logic
+- Contains: `event/` (Event enum, ActionCow), `url/` (UrlBuf, UrlLike, Scheme), `data/`, `errors/`, `pool/`, `strand/`, and misc types (`Id`, `Layer`, `Source`, `RoCell`, `SyncCell`, `Debounce`)
+- Key files: `yazi-shared/src/event/event.rs`, `yazi-shared/src/layer.rs`
+
+**`yazi-dds/src/`:**
+- Purpose: IPC broker for multi-instance communication
+- Contains: `client.rs`, `server.rs`, `pubsub.rs`, `payload.rs`, `stream.rs`, `ember/` (message frame types: Hi, Hey, Bye, payload body)
+- Key files: `yazi-dds/src/client.rs`, `yazi-dds/src/server.rs`, `yazi-dds/src/lib.rs`
+
+**`yazi-plugin/src/`:**
+- Purpose: Lua 5.5 scripting engine initialization, plugin loader, coroutine/isolate sandboxing
+- Sub-directories: `runtime/` (Lua globals composer), `loader/` (plugin discovery), `isolate/` (sandboxed execution), `pubsub/`, `fs/`, `external/`, `process/`, `theme/`, `utils/`
+- Key files: `yazi-plugin/src/lua.rs`, `yazi-plugin/src/runtime/runtime.rs`
+
+**`yazi-binding/src/`:**
+- Purpose: Lua UserData implementations for Rust types (Url, Rect, Style, Color, File, Id, Image, etc.)
+- Contains: `elements/` (ratatui widget helpers), and flat modules for each bound type
+- Key files: `yazi-binding/src/elements/`, `yazi-binding/src/file.rs`, `yazi-binding/src/url.rs`
+
+**`yazi-scheduler/src/`:**
+- Purpose: Async task runner with priority queues
+- Sub-directories: `fetch/`, `file/`, `hook/`, `plugin/`, `preload/`, `process/`, `size/`
+- Key files: `yazi-scheduler/src/scheduler.rs`, `yazi-scheduler/src/runner.rs`
+
+**`yazi-fs/src/`:**
+- Purpose: Local filesystem abstractions: `File`, `Files` collection, URL/path helpers, sorting, filtering, XDG paths
+- Contains: `file.rs`, `files.rs`, `cha.rs` (file characteristics), `sorter.rs`, `filter.rs`, `mounts.rs`, `provider/`
+- Key files: `yazi-fs/src/file.rs`, `yazi-fs/src/files.rs`
+
+**`yazi-vfs/src/`:**
+- Purpose: Unified virtual filesystem provider interface; delegates to local or SFTP backend
+- Contains: `provider/` with `local/`, `sftp/`; `cha.rs`, `file.rs`, `files.rs`, `op.rs`
+- Key files: `yazi-vfs/src/provider/providers.rs`, `yazi-vfs/src/provider/provider.rs`
+
+**`yazi-adapter/src/`:**
+- Purpose: Image rendering to terminal; auto-selects protocol per emulator brand
+- Contains: `adapter.rs`, `adapters.rs`, `drivers/` (chafa, iip, kgp, kgp_old, sixel, ueberzug), `image.rs`, `info.rs`
+- Key files: `yazi-adapter/src/adapter.rs`, `yazi-adapter/src/adapters.rs`
+
+**`yazi-macro/src/`:**
+- Purpose: Proc-macros used throughout the workspace
+- Contains: `actor.rs` (`act!`), `event.rs` (`emit!`, `relay!`), `render.rs` (`render!`), `module.rs` (`mod_pub!`, `mod_flat!`), `context.rs`, `fs.rs`, `fmt.rs`, `log.rs`, `stdio.rs`, `platform.rs`
+
+**`yazi-proxy/src/`:**
+- Purpose: Thin wrappers allowing async tasks to emit actions without holding `Core`
+- Contains: one file per layer: `app.rs`, `mgr.rs`, `input.rs`, `cmp.rs`, `tasks.rs`, `notify.rs`, `pick.rs`, `which.rs`, `confirm.rs`
+
+**`yazi-parser/src/`:**
+- Purpose: Typed `Options` structs (`CdOpt`, `OpenOpt`, `SortOpt`, ...) deserialized from `ActionCow` parameters
+- Sub-directories: one per layer matching `yazi-actor` structure
+
+**`yazi-watcher/src/`:**
+- Purpose: Watch local directory changes (platform FS events) and poll remote paths
+- Sub-directories: `local/` (OS watcher backend), `remote/` (polling for VFS paths)
+
+## Key File Locations
+
+**Entry Points:**
+- `yazi-fm/src/main.rs`: `yazi` binary entry; subsystem initialization order
+- `yazi-cli/src/main.rs`: `ya` CLI entry
+
+**Event Bus:**
+- `yazi-shared/src/event/event.rs`: `Event` enum definition and global channel
+
+**Core State:**
+- `yazi-core/src/core.rs`: `Core` struct aggregating all UI component states
+- `yazi-core/src/mgr/mgr.rs`: File manager state (tabs, yanked, watcher)
+- `yazi-core/src/tab/tab.rs`: Per-tab state (current folder, history, selection, preview)
+
+**Action Dispatch:**
+- `yazi-fm/src/executor.rs`: Routes `ActionCow` by layer to `act!` macros
+- `yazi-fm/src/router.rs`: Translates key events to action sequences via `KEYMAP`
+- `yazi-actor/src/actor.rs`: `Actor` trait definition
+
+**Actor Context:**
+- `yazi-actor/src/context.rs`: `Ctx` struct — short-lived mutable `Core` borrow passed to actors
+
+**Rendering:**
+- `yazi-fm/src/root.rs`: `Root` widget — Lua-driven base + Rust overlay z-stack
+- `yazi-fm/src/app/render.rs`: `App::render()` and `App::render_partially()`
+
+**Configuration:**
+- `yazi-config/src/lib.rs`: Global statics `YAZI`, `KEYMAP`, `THEME`, `LAYOUT`
+- `yazi-config/preset/`: Embedded default TOML files
+
+**IPC:**
+- `yazi-dds/src/client.rs`: Client connect/reconnect loop and `shot()`/`draw()` for `ya`
+- `yazi-dds/src/server.rs`: Unix socket server routing messages by ability
+
+**Lua Integration:**
+- `yazi-actor/src/lives/lives.rs`: `Lives::scope()` — pins Rust state as Lua globals
+- `yazi-plugin/src/runtime/runtime.rs`: `cx` global composer (args, mgr, preview, tasks)
+
+**Testing:**
+- Tests are co-located within each crate under `src/` using `#[cfg(test)]` modules
+
+## Naming Conventions
+
+**Files:**
+- `snake_case.rs` for all Rust source files
+- `mod.rs` for module root files within subdirectories
+- `lib.rs` for crate root files
+
+**Directories:**
+- `snake_case` for all source subdirectories
+- Directory name matches the module name it exposes (e.g., `yazi-actor/src/mgr/` → `pub mod mgr`)
+
+**Crates:**
+- All crates prefixed with `yazi-` (hyphenated); Rust module names use `yazi_` (underscored)
+
+**Types:**
+- `PascalCase` for structs, enums, traits
+- `SCREAMING_SNAKE_CASE` for module-level statics (`YAZI`, `KEYMAP`, `TX`, `RX`)
+- `snake_case` for functions and variables
+
+**Macros:**
+- `snake_case!` for all proc-macros (`act!`, `emit!`, `succ!`, `render!`, `mod_pub!`)
+
+## Where to Add New Code
+
+**New actor (user command):**
+- Implementation: `yazi-actor/src/{layer}/{command_name}.rs` implementing `Actor` trait
+- Options struct: `yazi-parser/src/{layer}/{command_name}.rs` or add to existing file
+- Registration: Add to `yazi-fm/src/executor.rs` in the relevant layer method using `on!(command_name)`
+- Proxy helper (if needed from async): Add method to `yazi-proxy/src/{layer}.rs`
+
+**New UI overlay:**
+- State struct: `yazi-core/src/{overlay_name}/` with `mod.rs`
+- Add field to `Core` in `yazi-core/src/core.rs`
+- Actor implementations: `yazi-actor/src/{overlay_name}/`
+- Renderer widget: `yazi-fm/src/{overlay_name}/` implementing `ratatui::Widget`
+- Add `Layer` variant to `yazi-shared/src/layer.rs`
+- Add executor routing in `yazi-fm/src/executor.rs`
+- Register in `Core::layer()` priority chain in `yazi-core/src/core.rs`
+
+**New configuration section:**
+- Config struct: `yazi-config/src/{section}/`
+- Add field to the relevant config aggregate struct
+- Add default values to `yazi-config/preset/yazi-default.toml`
+
+**New Lua binding (expose Rust type to plugins):**
+- UserData impl: `yazi-binding/src/{type_name}.rs`
+- Add to `yazi-actor/src/lives/` if it needs to be accessible via the `cx` global
+
+**Shared utilities:**
+- Cross-crate primitives: `yazi-shared/src/`
+- Filesystem helpers: `yazi-fs/src/`
+- New proc-macro: `yazi-macro/src/`
+
+## Special Directories
+
+**`yazi-config/preset/`:**
+- Purpose: Default TOML configurations embedded into the binary at build time
+- Generated: No (hand-authored)
+- Committed: Yes
+
+**`.planning/`:**
+- Purpose: GSD planning documents and codebase analysis (not shipped)
+- Generated: By GSD tooling
+- Committed: No (gitignored or team-local)
+
+**`target/`:**
+- Purpose: Cargo build artifacts
+- Generated: Yes
+- Committed: No
+
+**`assets/`:**
+- Purpose: Non-code resources (icon files, screenshots)
+- Generated: No
+- Committed: Yes
+
+---
+
+*Structure analysis: 2026-03-21*

.planning/codebase/TESTING.md

@@ -0,0 +1,251 @@
+# Testing Patterns
+
+**Analysis Date:** 2026-03-21
+
+## Test Framework
+
+**Runner:**
+- Rust's built-in `cargo test`
+- No external test runner; no `jest.config` or `vitest.config`
+
+**Assertion Library:**
+- `assert_eq!`, `assert_ne!`, `assert!` from Rust standard library
+- `anyhow::Result` used as test return type for `?` propagation
+
+**Run Commands:**
+```bash
+cargo test --workspace --verbose    # Run all tests across all crates
+cargo test -p yazi-core             # Test a specific crate
+cargo test test_backstack           # Run a single test by name
+cargo test --workspace              # Full suite (CI equivalent)
+```
+
+## Test File Organization
+
+**Location:**
+- Co-located: tests live in a `#[cfg(test)] mod tests { ... }` block at the bottom of the source file they test
+- No separate `tests/` integration test directories found
+- No external test fixtures directory
+
+**Naming:**
+- Test module: always named `mod tests`
+- Test functions: `test_` prefix followed by the function or concept being tested
+  - `fn test_backstack()`, `fn test_natsort()`, `fn test_clean_url()`, `fn test_split()`
+  - Behavior-specific names also used without `test_` prefix: `fn insert_many_success()`, `fn test_insert_conflicting_parent()`
+
+**Structure:**
+```
+src/
+├── some_module.rs          # Implementation + inline test module
+│   └── #[cfg(test)] mod tests { ... }
+├── path/
+│   ├── clean.rs            # Tests at bottom of file
+│   └── relative.rs         # Tests at bottom of file
+```
+
+## Test Structure
+
+**Suite Organization:**
+```rust
+#[cfg(test)]
+mod tests {
+    use super::*;                     // Always import everything from parent
+
+    #[test]
+    fn test_something() {
+        // arrange
+        let mut subject = Subject::default();
+        // act + assert
+        assert_eq!(subject.method(), expected);
+    }
+
+    #[test]
+    fn test_something_else() -> anyhow::Result<()> {
+        // Use Result return type for tests needing ? propagation
+        let u: UrlBuf = "/some/path".parse()?;
+        assert_eq!(format!("{u:?}"), "/some/path");
+        Ok(())
+    }
+}
+```
+
+**Section Separator:**
+```rust
+// --- Tests
+#[cfg(test)]
+mod tests {
+```
+The `// --- Tests` separator comment appears above the test module in some files.
+
+**Patterns:**
+- Setup: `Subject::default()` for zero-state; `yazi_shared::init_tests()` for global state
+- No `before_each` / `after_each`; each test is fully self-contained
+- Data tables (slices of tuples) used for parameterized assertions
+- Helper functions within the `mod tests` block used to reduce assertion boilerplate
+
+## Mocking
+
+**Framework:** None – no mocking crate used
+
+**Patterns:**
+- No mock objects; tests call real implementations directly
+- Platform-specific tests gated with `#[cfg(unix)]` / `#[cfg(windows)]` on individual test functions
+- Global state initialized with `yazi_shared::init_tests()` where needed (see below)
+- Tests that require filesystem state initialize `yazi_fs::init()` directly
+
+**What to Mock:**
+- Nothing – the codebase uses no mocking framework
+
+**What NOT to Mock:**
+- Filesystem, URLs, sorting – all tested with real values
+
+## Fixtures and Factories
+
+**Test Data:**
+The dominant pattern is inline slice literals of tuples serving as parameterized test cases:
+
+```rust
+let cases = [
+    // Comment describing the category
+    ("/a/b", "/a/b/c", "c"),
+    ("/a/b/c", "/a/b", ".."),
+    ("/a/b/d", "/a/b/c", "../c"),
+];
+for (from, to, expected) in cases {
+    let result = function_under_test(from, to);
+    assert_eq!(result, expected);
+}
+```
+
+**Helper closures and functions inside test modules:**
+```rust
+fn cmp(left: &[&str]) {
+    let mut right = left.to_vec();
+    right.sort_by(|a, b| natsort(a.as_bytes(), b.as_bytes(), true));
+    assert_eq!(left, right);
+}
+
+fn matches(glob: &str, url: &str) -> bool {
+    Pattern::from_str(glob).unwrap().match_url(UrlCow::try_from(url).unwrap(), false)
+}
+```
+
+**Global state initialization:**
+```rust
+#[test]
+fn test_something() {
+    yazi_shared::init_tests();    // Must call before any URL/path parsing
+    yazi_fs::init();              // Must call before CWD-dependent tests
+    // ...
+}
+```
+`init_tests()` is idempotent via `OnceLock` so ordering between tests doesn't matter.
+
+**Location:**
+- No separate fixtures directory; all test data is inlined in the test block
+
+## Coverage
+
+**Requirements:** Not enforced – no minimum coverage threshold configured
+
+**View Coverage:**
+```bash
+# No coverage tooling configured in the repository.
+# Use cargo-llvm-cov or cargo-tarpaulin manually if needed:
+cargo llvm-cov --workspace
+```
+
+## Test Types
+
+**Unit Tests:**
+- Dominant form: all tests are unit tests co-located with the code they test
+- Scope: individual functions and struct methods
+- Approach: pure input/output; no I/O or side effects except where `init_tests()` sets up global state
+
+**Integration Tests:**
+- Not present as a separate category; complex behavior tested via unit tests against real types
+
+**E2E Tests:**
+- Not present
+
+**Property-based Tests:**
+- Not present (no `proptest` or `quickcheck` dependencies)
+
+## Common Patterns
+
+**Table-driven tests (most common):**
+```rust
+let cases: &[(&str, &str)] = &[
+    ("input_a", "expected_a"),
+    ("input_b", "expected_b"),
+];
+for &(input, expected) in cases {
+    assert_eq!(function(input), expected, "input: {:?}", input);
+}
+```
+
+**Fallible tests with `anyhow::Result`:**
+```rust
+#[test]
+fn test_join() -> anyhow::Result<()> {
+    crate::init_tests();
+    let base: UrlBuf = "/a".parse()?;
+    assert_eq!(format!("{:?}", base.try_join("b/c")?), "/a/b/c");
+    Ok(())
+}
+```
+
+**Platform-conditional tests:**
+```rust
+#[cfg(unix)]
+#[test]
+fn test_split() {
+    yazi_shared::init_tests();
+    yazi_fs::init();
+    // unix-specific assertions
+}
+
+#[cfg(windows)]
+#[test]
+fn test_split() {
+    yazi_fs::init();
+    // windows-specific assertions
+}
+```
+
+**Struct state verification tests:**
+```rust
+#[test]
+fn test_remove() {
+    let mut s = Selected::default();
+    assert!(s.add(Path::new("/a/b")));
+    assert!(!s.remove(Path::new("/a/c")));    // non-existent
+    assert!(s.remove(Path::new("/a/b")));     // exists
+    assert!(s.inner.is_empty());
+    assert!(s.parents.is_empty());
+}
+```
+Note: test code accesses private fields (`s.inner`, `s.stack`, `s.cursor`) directly because tests are in the same file.
+
+**Error testing:**
+```rust
+// Testing absence (None/false) explicitly
+assert_eq!(bs.shift_backward(), None);
+assert!(!s.add(Path::new("/a/b")));   // returns false when conflict
+
+// Testing error propagation
+let result = risky_function();
+assert!(result.is_err());
+// OR via ? in Result-returning tests
+```
+
+## CI Integration
+
+**Matrix:** Ubuntu, Windows, macOS (all via `cargo test --workspace --verbose`)
+**Trigger:** push/PR to `main` branch
+**Lint checks run separately:** Clippy (`cargo clippy --all`), rustfmt (`rustfmt +nightly --check **/*.rs`), StyLua
+**Caching:** sccache via `mozilla-actions/sccache-action`
+
+---
+
+*Testing analysis: 2026-03-21*