patterm/CHANGELOG.md

# Changelog

All notable changes to patterm are tracked in this file. Format follows
[Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and the project
loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [Unreleased]

### Fixed
- Long claude session resume (and codex steady-state rendering) is
  noticeably faster. Two costs that scaled per-PTY-chunk are now
  deferred or short-circuited: (1) `drawSidebar()` used to run
  synchronously for every chunk that scrolled — on a session
  resume where every chunk scrolls, this rebuilt the full sidebar
  string hundreds of times for a frame that was almost always
  cache-equal. The sidebar now signals dirty and the chrome ticker
  (60 Hz) handles the repaint. (2) `pumpChild` polled the
  emulator's OSC title after every PTY chunk via CGO, even for
  chunks (the common case under codex/ratatui) that carry no OSC
  bytes at all. The poll is now gated on a containsOSC scan over
  the chunk.
- Click-and-drag text selection from alt-screen TUIs (codex in
  particular) now works. Patterm used to keep host SGR mouse
  reporting armed continuously, which forced the host terminal to
  forward every click as an escape sequence and prevented native
  selection. The host's mouse mode now follows the focused child's
  screen side: primary-screen children keep mouse armed (so wheel
  scrollback works), alt-screen children get host mouse disabled by
  default. Alt-screen TUIs that need mouse events (vim, less, etc.)
  re-enable mouse-mode themselves; the viewport renderer forwards
  those toggles to the host while the child is on alt. Leaving alt
  re-arms host mouse reporting so wheel scrollback resumes.

### Added
- MCP `initialize.instructions`, the `spawn_agent` tool description
  (visible to LLMs via `tools/list`), and the `help('spawning')`
  topic now spell out — in the three places vendor TUIs actually
  consult — that the connected `patterm` MCP server is the only
  correct way to drive the host. Anti-patterns called out by name:
  (a) trying to launch `patterm` / `patterm mcp-stdio` themselves,
  (b) piping JSON-RPC into the per-PID Unix socket via `perl` /
  `nc` / `socat` / `curl`, and (c) shelling out to `claude` /
  `codex` / `opencode` to start a peer. Each of those bypasses
  caller identity, so a sub-agent spawned that way reads back as
  a stray top-level tab instead of a child under the spawning
  agent. Codex was hitting (b) and (c) in practice — this is the
  fix.
- `--debug[=DIR]` flag captures detailed run artefacts for offline
  analysis: a verbose `patterm.log` (the existing `PATTERM_DEBUG_LOG`
  stream), an `events.jsonl` lifecycle log (spawn / exit / idle-state
  changes with timestamps), and per-child `<id>.raw` files containing
  the raw PTY byte stream. With no argument, the dated subdir
  `$XDG_STATE_HOME/patterm/debug/YYYYMMDD-HHMMSS` is used; pass an
  explicit path to override. All output goes to files — stdout/stderr
  are untouched.
- `--profile[=DIR]` flag captures pprof data plus concrete
  performance counters for performance work: `cpu.pprof` (running
  for the lifetime of the session), plus `heap.pprof` and
  `goroutine.pprof` snapshots written on shutdown; alongside them,
  a per-hot-path metrics tracker writes `metrics.jsonl` (one row
  per second with chunk/byte rates, per-stage mean and max
  latencies, and cache hit rates) plus a final `metrics.json`
  aggregate and a human-readable `summary.txt` on exit.
  Instrumented hot paths: `OnPTYOut`, viewport `renderer.Render`,
  host stdout writes, libghostty-vt `emulator.Write` / `Title`,
  sidebar / tab bar / status line draws (with cache-hit
  accounting), snapshot replays, and the chrome ticker (so you can
  see how often it fires with nothing to do). Defaults to
  `$XDG_STATE_HOME/patterm/profile/YYYYMMDD-HHMMSS`. All
  diagnostics (startup, errors) are written to `profile.log`
  inside the dir, never to stdout/stderr.
- Renderer benchmark suite (`internal/app/bench_test.go`). Three
  workload fixtures — plain ASCII, SGR-styled lines, and a
  ratatui-style cursor-shuffling burst — plus an OSC-gate
  micro-benchmark. Run via `go test -bench=. -benchmem
  ./internal/app/`. Gives a stable reference for the per-chunk
  cost of the viewport renderer so future changes can be compared
  apples-to-apples.
- "New Terminal" entry in the command palette spawns a bare interactive
  `$SHELL` pane (kind `terminal`). Unlike "Run process: …" presets,
  which are session-persistent and reachable via `restart_process`,
  terminals are ephemeral — once they exit they vanish from the
  Processes sidebar instead of lingering as a dead row. The default
  `shell` process preset that previously seeded on first run has been
  removed; this entry replaces it.
- Per-child idle-state classifier with five states (`idle`, `working`,
  `thinking`, `permission`, `error`) and three pluggable strategies:
  `output_activity` (claude / opencode defaults), `osc_title_stability`
  (codex), and `osc_title_status` (gemini-style status-in-title agents).
  Optional `permission_patterns` / `thinking_patterns` / `error_patterns`
  regexes promote a base state when matched against the tail of recent
  output. State and last-match reason are exposed via MCP on
  `ProcessInfo` and `get_process_status` (`idle_state`, `idle_reason`).
- New `idle_detection` block on `preset.Preset` for setting the strategy
  threshold, title-to-state map, and promoter regex lists. Bundled
  defaults are shipped for the first-party claude / codex / opencode
  presets.
- Sidebar now renders a state glyph per process row (`○` idle, `●`
  working, `◐` thinking, `?` permission, `✕` error) and, when a process
  has a pending or paused timer, appends a nearest-timer indicator
  (`⏱ 12s` or `⏸ paused`).
- MCP timer surface expanded to match Solo's tool set: `timer_set`,
  `timer_fire_when_idle_any`, `timer_fire_when_idle_all`, `timer_cancel`,
  `timer_pause`, `timer_resume`, `timer_list`. Idle-aware timers
  registered against already-idle children fire synchronously
  (`status: already_satisfied`) for `idle_all`, and report
  `already_idle` / `waiting_on` arrays so callers can introspect the
  watch set. Timer bodies are delivered to the owner process via the
  same orchestrator-injection path as `send_message`.
- Timer tools accept an explicit `owner_process_id` so top-level
  (non-agent) callers — including the harness MCP client — can attribute
  timers to a specific process. Omitting it treats the caller as the
  orchestrator with universal cancel / pause / resume / list privileges.
- libghostty-vt `Title()` accessor on the emulator surface, polled from
  the session pump so OSC 0/1/2 title updates feed into the classifier
  without a callback round-trip.
- Harness `wait_until_mcp` step type that re-runs an MCP method until an
  assertion (Equals / Contains) holds or the timeout elapses. Used by
  the new idle / timer scenarios.
- User-created top-level command processes now survive a patterm
  restart. Each spawn (palette form, command preset, or MCP
  `spawn_process` with `kind=command`) writes a record to
  `$XDG_DATA_HOME/patterm/projects/<key>/processes.json`; on next
  startup patterm replays those entries before the UI accepts input,
  so things like `bun run dev` or `tail -F log` come back without
  re-typing. `close_process` (and the palette's close action) drops
  the entry, and rename / "relaunch on exit" toggles are mirrored as
  they happen. Agents and terminals stay ephemeral by design.
- The command palette (Ctrl-K) now surfaces context-aware actions at
  the top of the list, based on what's currently focused:
  - Scratchpad in focus: `Delete`, `Rename` (inline form), and `Edit`
    (fire-and-forget launch of `zed` against the pad file).
  - Agent in focus: `Rename agent` (inline form) and `Close agent`.
  - Process in focus: `Rename process`, `Delete process` (drops the
    entry; SIGKILLs if alive), `Stop process` (SIGTERM, keep entry),
    and `Restart process` (same argv).
- `patterm --version` prints the build version, git commit, and build
  date (e.g. `patterm v0.0.1 (commit abc1234, built 2026-05-14)`). The
  version string is injected by the build (`make patterm` derives it
  from `git describe`; the release workflow injects the pushed tag).
  Commit and date come from the Go toolchain's embedded VCS info, so
  nothing has to be bumped by hand.
- Ctrl+R restarts the focused command process from the Processes
  sidebar, including command entries that have already exited.
- Scratchpads are now first-class navigation targets. Ctrl+W / Ctrl+S
  step from the Processes section and agent tree onto scratchpad
  entries; a focused scratchpad renders its content in the main
  viewport (with the pad name as the header) instead of cramping the
  bottom of the sidebar. The sidebar's scratchpad section is a names-
  only list with the focused pad highlighted, and external MCP
  `scratchpad_write` / `scratchpad_append` updates repaint the pad
  view immediately.
- Focused scratchpads now render as markdown — headings, bold, inline
  code, fenced code blocks, bullet/numbered lists, blockquotes, and
  horizontal rules pick up styling instead of the previous flat
  word-wrap. Long pads scroll: the mouse wheel is the primary control
  (patterm enables SGR mouse reporting while a pad is focused), and
  Up/Down / PageUp/PageDown / Home / End work for keyboard users. The
  header reports the visible row range and total row count. Esc leaves
  the pad view and falls back to the first running process (or an
  empty viewport). The scroll offset is preserved across MCP
  `scratchpad_write` / `scratchpad_append` writes so a live update
  doesn't snap the view back to the top.
- Inline wheel scrollback for the focused child, backed by
  libghostty-vt's native 5000-row scrollback history. On the primary
  screen, mouse-wheel events scroll the emulator viewport in-place with
  full SGR styling preserved — no modal view to enter or exit. On the
  alternate screen wheel events still pass through to the child so
  vim / less / codex receive them as input. Ctrl+B snaps the viewport
  back to the live (bottom) area as the escape hatch from a scrolled-up
  state. Patterm now keeps SGR mouse reporting armed on the host
  terminal while the alt screen is active and filters mouse-mode
  toggles from the child stream so wheel events keep arriving even
  after a child program disables mouse tracking.

### Changed
- The palette's per-child "Kill <name>" action is now labelled
  "Close <name>". The underlying signal (SIGTERM) and behaviour are
  unchanged; the new label matches the existing "Close agent: …"
  context entry and reads less violent for what is really just a
  graceful termination.
- `timer_wait` is now a thin wrapper over the shared timer manager
  (`timer_set` semantics). Existing callers see no behavioural change;
  the timer is visible in `timer_list` while it's pending.
- CLI flag parsing switched from Go's stdlib `flag` to `spf13/pflag`.
  `--project` (and the internal `--socket` / `--identity` /
  `--scenario` / `--patterm-bin` flags) are now the only accepted form
  — single-hyphen long flags like `-project` are rejected. Help output
  renders the canonical `--flag` form.

### Fixed
- Exited terminal panes (kind `terminal`, including those launched via
  the new "New Terminal" palette entry or MCP `spawn_process` with
  `kind=terminal`) are now removed from the session and the Processes
  sidebar as soon as they exit. Previously they stuck around as a
  greyed-out row indistinguishable from an exited command process,
  even though terminals have no restart path.
- `whoami` and `help("timers")` now advertise the full Solo-parity timer
  surface (`timer_set`, `timer_fire_when_idle_any`,
  `timer_fire_when_idle_all`, `timer_cancel`, `timer_pause`,
  `timer_resume`, `timer_list`) so agents using either tool for
  orientation discover them — previously only `timer_wait` was listed.
- Resuming a paused idle-aware timer now re-checks the satisfaction
  condition. Previously, if every watched process became idle (or, for
  `idle_any`, any non-baseline watcher went idle) while the timer was
  paused, the timer stayed pending forever because no further state
  transitions were observed.
- Fired and canceled timers are now removed from the timer registry,
  so long-running patterm sessions no longer accumulate completed
  timer records and message bodies. `timer_list` and the sidebar
  indicator already filtered them out; only the in-memory leak is
  fixed.
- Per-preset idle-detection config is now installed through `SpawnSpec`
  before the child is published to the session, closing a race in
  which the classifier goroutine could observe a freshly spawned
  process before its preset's classifier strategy was attached.
- Opening the command palette while a scratchpad was focused left the
  palette wedged — typing did nothing and Esc left the palette's top
  border drawn over the pad until you closed the pad with Ctrl-W and
  re-opened the palette. The stdin loop's scratchpad-input branch ran
  before the palette branch and silently dropped every byte except a
  handful of app-level chords, so palette filter input and Esc never
  reached `palette.handleInput`. The palette branch now takes
  precedence whenever the palette is open, and `closePalette` repaints
  the pad (instead of the empty focused-child slot) on cancel / no-op
  action. Switching from a pad to a child via the palette now clears
  the pad focus and wipes the viewport, matching `focusProcess`.
- Tab bar and bottom status row no longer get overwritten by long
  claude / codex sessions. Three holes were letting child output land
  on the chrome: (1) absolute cursor moves — CUP / HVP / VPA — added
  the row offset but didn't clamp to the viewport, so a child whose
  internal row state drifted past its assigned height could walk the
  host cursor onto the status row (or above the tab bar); (2) relative
  cursor moves — CUU / CUD / CNL / CPL — were forwarded verbatim, so
  a `CSI 50 A` from viewport row 1 walked the host cursor into the
  tab bar before the next printable wiped it; (3) the host's DECSTBM
  scroll region was only set during snapshot-replay preludes, so the
  windows between (startup before first focus, post-SIGWINCH,
  post-clearScreen) left the region defaulted to the full screen and
  any LF / IND / NEL / RI / SU / SD at the viewport bottom scrolled
  the chrome rows along with the pane. The cursor shifter now clamps
  CUP/HVP/VPA rows to mainTop..mainBottom, the viewport renderer
  rewrites CUU/CUD/CNL/CPL with a clamped step (and homes the column
  for CNL/CPL), and patterm installs the host scroll region after
  `enterScreen` and after every `clearScreen` (and resets it cleanly
  on `leaveScreen` so the calling shell isn't left with a constrained
  region).
- Plain line-feed scrolling at the bottom of a child pane now invalidates
  and repaints the sidebar, so long agent output can no longer drag the
  sidebar border and labels out of view while the chrome cache stays warm.
- Child DEC origin-mode and left/right-margin controls are now handled
  inside the viewport renderer instead of being forwarded to the host
  terminal, so later tab bar, sidebar, and status-line repaints keep
  using physical screen coordinates and do not appear inside the
  focused pane.
- Exited command processes in the top Processes section are now reachable
  with Ctrl+W/S navigation, so a dead shell entry can be focused and
  restarted instead of becoming a visible but unreachable row.
- Resizing the host terminal no longer makes codex (and other
  diff-based TUIs) scroll-jump for several seconds. SIGWINCH is now
  coalesced into a single resize after an ~80ms idle, the resize path
  skips the full snapshot replay (the child's own SIGWINCH-driven
  redraw fills the viewport), and `Child.NudgeRedraw` no longer
  toggles the PTY through rows-1 + rows back-to-back during a
  drag-resize.
- Steady-state CPU during a long codex session dropped sharply.
  Tab-bar and status-line repaints moved off the per-PTY-chunk path
  to a 16ms chrome ticker; the scratchpad listing is cached and only
  rebuilt when the pads change; the post-spawn / post-repaint
  styled-snapshot replay budget dropped from 8 chunks to 2; URL/port
  scanning short-circuits chunks that don't contain "http"; the
  three writes around the autowrap toggle in `OnPTYOut` collapsed
  into one syscall; the per-PTY-read `make+copy` was removed (the
  64 KiB read buffer is reused, with a documented "do not retain"
  listener contract); session listeners now dispatch through an
  `atomic.Pointer` snapshot instead of a mutex copy on every chunk;
  the per-child output ring is a true wrap-around buffer instead of
  a slide-and-trim slice; `wait_for_pattern` wakes on PTY chunk
  events with a 500ms fallback instead of unconditional 50ms
  polling; ANSI stripping in MCP `get_process_output stream`,
  `search_output`, and `wait_for_pattern scrollback` is now an
  in-place byte walk; and the viewport renderer copies long ASCII
  runs en bloc instead of feeding the state machine one byte at a
  time.

## [0.0.1] - 2026-05-14

### Fixed
- Tab bar redraw used `\x1b[2K` to clear rows 1 and 2 before painting
  labels, which wiped the sidebar columns on those rows too. When the
  sidebar cache was still warm the rail never repainted, leaving a
  gap where the sidebar's top border and "Processes" header should be.
  The clear is now bounded to the viewport width.
- Long-running TUIs (claude / codex) whose internal column state
  drifted past the patterm viewport could spray text into the sidebar
  columns — overwriting the session-tree and scratchpad rail until the
  user opened/closed the palette to force a full repaint. The viewport
  renderer now clamps absolute cursor positioning (CUP / HVP / CHA /
  HPA) to the viewport's right edge and drops printable bytes (ASCII
  and full UTF-8 glyphs) that would otherwise land past it. Covered by
  a unit suite and a new `sidebar_survives_wide_writes` harness
  scenario.
- Sub-agent panes spawned while another diff-based TUI (claude/codex/
  opencode) held focus could come up corrupted because the new child's
  first incremental updates targeted cells the host viewport hadn't
  populated yet. `OnChildSpawned` now primes the snapshot-replay budget
  for the new child, so its first PTY chunks render from the full
  styled emulator grid — the same path that fixed the symptom when the
  user manually cycled focus with Ctrl+W / Ctrl+S.

### Changed
- Command palette `Kill …` entries now mark the focused tab with the
  same "• … (current)" marker the `Switch to …` entries use, so the
  user can tell at a glance which tab a kill action targets.
- Status line now advertises the navigation chords (`Ctrl-A/D · tabs`,
  `Ctrl-W/S · tree`) alongside `Ctrl-K · palette`. Hints decay
  shortest-first when the terminal is too narrow to fit all three.

### Added
- "Spawn process…" entry in the command palette opens a two-field form
  for typing an arbitrary command line and ticking "Relaunch on exit".
  The command runs through `sh -lc` so multi-word lines like
  `bun run dev` resolve binaries the way an interactive shell would.
  When the relaunch flag is set, patterm Starts the process again after
  it exits (1s backoff). Killing the process from the palette clears
  the flag so it does not come back.
- Dedicated "Processes" section in the sidebar above the agent tree,
  listing every top-level command/terminal process. It is global to
  the patterm session — switching between agent tabs no longer changes
  which processes are visible. The relaunch-on-exit indicator (`⟳`)
  shows next to processes the user opted into auto-restart for.
- Ctrl+W / Ctrl+S now traverse the combined Processes section and the
  active agent tree as one flat list, so the user can step out of the
  agent tree into the Processes pane and back without leaving the
  keyboard.
- New `lifecycle` help topic spelling out that the caller owns the
  processes it spawns and should call `close_process` when a sub-agent
  or spawned process is no longer needed. The `spawn_agent` and
  `spawn_process` tool descriptions advertised via `tools/list` now
  call out the same cleanup duty (with a pointer to `help('lifecycle')`),
  and the `spawning` help topic and `topics` index cross-reference it.
- `spawn_agent` now prepends a single-line `[system: …]` orientation
  block to the sub-agent's first prompt so vendor TUIs (claude, codex,
  opencode) know they're a sub-agent, are reminded to `send_message`
  their parent with a summary when done, and to clean up processes /
  scratchpads they created. Skipped for top-level launches and empty
  instructions.
- Ctrl+A / Ctrl+D step focus between top-level tabs; Ctrl+W / Ctrl+S
  step through processes (root + sub-agents) inside the current tab.
  Recognised in legacy, kitty CSI u, and xterm modifyOtherKeys
  encodings. The chord shadows the corresponding raw byte for the
  focused pane — pressing Ctrl+D no longer sends EOF to the
  underlying shell, for instance.
- MCP protocol layer (`internal/mcp/protocol.go`) implementing
  `initialize`, `tools/list`, `tools/call`, `ping`, and MCP
  notifications. Tool catalog with input schemas is advertised via
  `tools/list`. Real MCP clients (claude, etc.) can now complete the
  handshake against patterm's per-PID socket. Legacy direct-tool
  dispatch is preserved so the harness keeps working unchanged.
- `mcp_injection.kind = "cli_override"` for agents that accept inline
  `key=value` config overrides on the command line. The default codex
  preset uses it to emit `-c mcp_servers.patterm.command=…` and
  `-c mcp_servers.patterm.args=[…]` — zero files written, no
  `CODEX_HOME` override.
- `mcp_injection.kind = "config_env"` for agents that read their
  config from an env var. The default opencode preset uses it to pass
  a merged `opencode.json` inline through `OPENCODE_CONFIG_CONTENT`,
  so auth/agents/tui.json/skills resolve from the user's real `$HOME`
  with no XDG override.
- Palette macros: typing `sw `, `k `, or `sp ` filters the list to
  switch / kill / spawn entries respectively. Footer shows the
  available macros.

### Changed
- The sidebar's session-tree section is now labeled "Agent Tree" and
  shows only agent sessions (and any sub-agents they spawn). Top-level
  command and terminal processes live in the new "Processes" section
  above it.
- Tab bar tabs now correspond to agent sessions only. Command/terminal
  processes that previously claimed a top-level tab now appear in the
  Processes sidebar section, so the tab strip is reserved for agent
  context.
- Focus, lifecycle, and repaint paths now capture terminal layout before
  taking UI state locks, reducing resize-time deadlock risk without
  changing visible behavior.
- Focused PTY output no longer rebuilds the scratchpad sidebar on every
  chunk. The sidebar still repaints on focus/lifecycle/resize changes
  and when child output scrolls over the chrome, but normal output avoids
  repeated scratchpad disk reads.
- Harness scenario tests now reuse one built patterm binary per test run
  and write failure artifacts under a repo-rooted, collision-proof
  directory.
- Palette ordering: open agents/processes (`Switch to …`) now appear
  above the option to spawn new ones, with kill entries pushed down
  toward the end of the list.
- Tab bar trimmed from three rows (label / subtitle / underline) to
  two (label / underline). Tabs flex to fill the available host width
  evenly with leftover columns distributed to the leftmost tabs; the
  `+ new` hint sits in a reserved slot on the right. Layout's
  `mainTop` consequently drops from 4 to 3, giving each pane one
  extra row of viewport.

### Fixed
- Agent MCP injection no longer writes unused config files for inline
  injection modes (`cli_override` / `config_env`). File-backed injection
  modes track their generated paths and clean them up when the child is
  closed, exits, or patterm shuts down.
- MCP `tools/list` descriptions now match the runtime argument values
  for process output and pattern waiting, and typed invalid-argument
  errors map to JSON-RPC invalid params instead of generic internal
  errors.
- Scratchpad writes and appends are serialized inside a patterm process
  so `expected_revision` checks cannot race another local scratchpad
  mutation.
- The sidebar scratchpad list now refreshes after MCP
  `scratchpad_write` and `scratchpad_append` calls.
- UI chrome now reads renamed child display names through the
  `DisplayName` accessor, avoiding races with `rename_process`.
- Child processes spawned by an orchestrator are now killed when the
  orchestrator dies, recursively through the tree. Applies whether the
  parent was closed via MCP, Ctrl-C'd by the user, or exited on its
  own — `reapChild` cascades a SIGTERM (escalating to SIGKILL after 2s)
  to every direct child, and each descendant's own reap fires the same
  cascade so the kill flows through arbitrary depth.
- Killed agents no longer linger in the command palette. Agent
  entries that aren't running are filtered out of the switch list;
  session-persistent commands (which can be restarted) stay visible.
- `tools/list` now emits a concrete `properties` object (`{}`) for
  parameterless tools instead of `null`. Claude rejected the
  `null`-properties form with "tools fetch failed" even though the
  initialize handshake had succeeded.
- Sidebar no longer flickers on every PTY chunk. The tab bar,
  sidebar, and status line now cache their last rendered byte string
  and skip the write when the new frame matches; full repaint paths
  (resize / focus change / palette close / screen clear) invalidate
  the cache so the next draw fires unconditionally.
- Spawning a child agent now clears the viewport area before it
  paints, so the previous focused child's PTY output no longer bleeds
  through underneath the new pane.
- Orchestrator-injected input (initial agent prompts, MCP
  `send_input` with `submit: true`, `send_message`, `timer_wait`
  callbacks) now ends with CR (`\r`) instead of LF (`\n`). Claude
  treated `\n` as "newline in textarea"; with CR the prompt actually
  submits, matching what the host terminal sends when a user presses
  Enter directly.
- Enter is now written to a child PTY as its own `write()` call,
  separated from the preceding text by a short delay. Both
  `InjectAsUser` (user typing forwarded through patterm) and
  `InjectAsOrchestrator` (MCP / send_message / initial-prompt paths)
  share the split. Without it, claude — and other paste-detecting
  TUIs — coalesced `"hello\r"` into one read and inserted the CR as
  literal text instead of treating it as the Enter keystroke.
- Sidebar (and tab bar) no longer get wiped when the focused child
  issues `CSI 0 J` / `CSI 1 J` (clear-to-cursor). The viewport renderer
  already clamped `CSI 2 J` and `CSI K` to viewport columns, but the
  partial-screen variants were forwarded verbatim, so any tool-call
  expansion in claude (Ctrl+O) would erase every cell to the right of
  the cursor — including the right rail. Both forms are now translated
  into per-row ECH sequences that stop at the viewport's right edge.
- Sidebar left border no longer vanishes when the viewport repaints.
  The border column was the same column as the viewport's rightmost
  cell, so any child write to that column (or `clearViewport`'s ECH)
  would erase it. The viewport is now one column narrower so the
  border has a dedicated column.
- Sidebar session-tree entries no longer get pushed downward when an
  agent emits a scroll burst on startup. Codex (Ratatui) issues 8× RI
  (`\x1bM`) right after setting its scroll region, which scrolls the
  region down across every column — dragging the right-rail entries
  with it. The chrome cache then hid the clobber because the computed
  frame still matched. The viewport renderer now flags any chunk that
  contains a scroll-triggering escape (RI / IND / NEL / SU / SD / IL /
  DL) and `OnPTYOut` drops the sidebar cache when the flag is set, so
  the next `drawSidebar` repaints over the drift.

## Conventions

- This file is the single record of user-visible changes; the TODO is
  scratch space, not history.
- One bullet per change, written in the past tense from the user's
  point of view. Reference the package or preset name when it helps a
  reader find the code.