build: bump libghostty-vt to ghostty main tip + zig 0.16

[charliek]

Bumps the vendored libghostty-vt pin from ghostty c74f6d56 (2026-04-25) to main tip f2d5758f6 (2026-08-26) with the zig 0.15.2 → 0.16.0 toolchain migration. First PR of plan 032 (three-PR stack: this bump, then tracked-ref selection #334, then formatter/render adoption #335 — those branch from this one and are noted as stacked in their bodies).

Closes #333

What changed

C1 — toolchain + pin + port (b6c46f7)

• .mise.toml zig → 0.16.0; build.sh SHA bump, zig check → 0.16.x, and the macOS-26 arm64 SDK shim deleted (zig 0.16 resolves the SDK correctly — spike-verified on the machine class the shim guarded; revert = restore from git history).
• Three upstream API breaks ported (Rust + Swift twins): mode_get → ghostty_terminal_get(DATA_MODE); colors_get → ghostty_render_state_get(DATA_COLORS); terminal_new(cols, rows) + scrollback via terminal_set.
• Behavior fix: scrollback now genuinely honors the configured line limit. At the old pin the configured value was internally a byte cap, silently limiting history to a few hundred rows; the port sets SCROLLBACK_MAX_LINES and clears the constructor's default 10 KB byte cap. New scrollback_limit_test.rs pins both keys.
• GhosttyResult −5/−6/−7 mapped into Error with a table test cross-checked against bindgen constants; bindgen enum-signedness sweep (upstream now emits : int).
• Tripwire triage (deliberate, none weakened): eviction test setup now writes 5000 rows (tip prunes page-granular) and pins the drift property (portable across the 16K/4K page-size targets); the theme-reset divergence tripwire inverted into a positive pin after upstream fixed DynamicRGB.reset().

C5 — docs/changelog sweep (2f190cf): every doc naming zig 0.15 or the old pin, the stale SDK-shim instruction rewritten, CHANGELOG entry.

Verification

• build.sh --force clean on macOS 26 arm64 (no shim), vendored tree at target SHA.
• cargo test -p roost-vt --features ffi: 106 tests green (incl. new scrollback + error-table tests).
• make check exit 0 (one earlier run had 2 roost-cli doctor-test failures under heavy parallel load; verified load flakes — pass standalone and on the quiet re-run).
• Mac: swift build + swift test (722 tests, 29 suites) green. No live local Mac run (single-instance constraint); e2e-mac on CI is the live gate.
• Shed (Linux VM) e2e-iced + screenshot smoke run in progress; results recorded in the plan's § Verified.

Review

Plan panel-reviewed pre-implementation (Codex + GLM + CodeRabbit). Diff review chain: codex quota-failed, cursor CLI unauthenticated → CodeRabbit agent + orchestrator self-review. CodeRabbit findings: default-byte-limit bug fixed; non-portable drift literal fixed; read_u32 on the u16 cursor-viewport keys noted pre-existing, deferred.

Impact

• Toolchain: zig 0.16.0 required (mise-provisioned; CI/release/shed all read .mise.toml). CI vendored-ghostty caches rotate automatically (key = hash of build.sh). First CI runs rebuild the archive per OS — slower once.
• No new dependencies; no secrets/privacy impact.
• Unlocks (follow-up PRs + filed issues): tracked grid refs (Fix selection drift on evicted scrollback with tracked grid refs (blocked on #333) #334), selection formatter + begin/end update (Adopt ghostty_terminal_selection_format_alloc and begin_update/end_update (blocked on #333) #335), snapshot API, native notification/paste/OSC-52 effects.

Plan 032 (full text)

# Plan 032 — Bump libghostty-vt to ghostty main tip + zig 0.16, adopt tracked refs & new selection/render APIs

**Status:** panel-reviewed (Codex + GLM 5.3 + CodeRabbit, 2026-08-26)
**Panel corrections incorporated:** scrollback maps to `_MAX_LINES` not
`_MAX_BYTES`; eviction acceptance split into follows-vs-`None` cases
(tracked refs go `NO_VALUE` when the selected content itself is pruned);
active-screen formatter precondition added to D5; `mode_get` keeps its
one-arg signature; third new result code `GHOSTTY_REJECTED = -7`; no
Swift error-enum mirror exists (task dropped); stacked-PR CI gap fixed
(all PRs target `main`); C4 re-motivated as mechanical adoption (no
caller-held lock exists in roost); file map extended (RenderState.swift,
5 Swift test files, third_party README, terminal-queries.md, ipc.md,
test_selection.py, CHANGELOG.md); C1 front-loads a bindgen+swift smoke;
`make docs` added where docs change; error-table, constructor-limit, and
tracked-ref test batteries added.
**Scope brief:** Bump the libghostty-vt pin to ghostty main tip with the
zig 0.15.2→0.16.0 toolchain migration, then adopt the newly available
APIs: #334 (selection drift → tracked grid refs) and #335
(`ghostty_terminal_selection_format_alloc` + render-state
`begin_update`/`end_update`). Keep roost-vt bindgen (libghostty-rs
deferred), Swift edits stay mechanical twins, new API adoption
Rust-first. Also file/map GitHub issues for post-bump features (W4).
**Repos:** roost only.
**Artifacts:** `~/.claude/plans/roost/032-ghostty-tip-zig016/` (spike
build log, sizeof probe + output, link-smoke + output already there).

## 1. Problem / motivation

The libghostty-vt pin (`c74f6d56`, 2026-04-25) is ~1,500 commits behind
ghostty main (~109 touching the lib-vt surface). Upstream's zig-0.16
boundary (2026-07-21) put nearly everything Roost wants on the far side:
the snapshot API (host-sessions attach primitive per
`discovery/host-sessions.md:207-248`), desktop-notification/progress OSC
effects, the paste API, OSC 52 read/write callbacks, XTGETTCAP
answering, semantic-prompt state, tracked grid refs, the full selection
API, and substantial render-state update optimizations. Issue #333
scoped a half-bump to the last 0.15-buildable SHA; the aligned direction
is straight to tip with the zig bump (zig tracks ghostty's own
`minimum_zig_version`, `0.16.0` at tip). #334 and #335 are the first two
adoptions the bump unblocks.

libghostty-rs (evaluated 2026-08-26) is **deferred**: its published
0.2.1 bakes the host CPU into vendored builds (their #66, fixed on
master only), its next release forces both zig 0.16 and *their* ghostty
pin cadence, and Roost's surface is 100% covered either way so the
option does not decay. `roost-vt` remains the seam — consumers see only
roost-vt types, so a later backend swap is invisible to `roost-iced`.

## 2. Current state (verified 2026-08-26)

- Pin: `GHOSTTY_SHA="c74f6d56d1feef473033057bc0ff7e3f00cf6421"`
  (`third_party/ghostty/build.sh:22`); zig check enforces 0.15.x
  (`build.sh:47-54`); macOS-26 arm64 SDK shim at `build.sh:56-126` was
  written against zig 0.15.2 behavior. `.mise.toml` pins zig 0.15.2.
- The pin is **ahead of every ghostty release tag** (v1.3.1 =
  2026-03-13 is its ancestor); any bump is a main-SHA bump. Target:
  `f2d5758f6305867dc36b36293c6165d8152b853e` (2026-08-26 main tip,
  fetched + spike-built).
- FFI exposure: 59 of 141 `ghostty_*` functions; ~88 Rust + ~108 Swift
  raw call lines. Rust wrapper `crates/roost-vt/` (3,843 src lines,
  1,999 tripwire-test lines, bindgen via `build.rs` with wholesale
  `ghostty_.*` allowlists). Swift shares the exact same header via the
  `mac/Sources/CGhosttyVT/include/ghostty` symlink — new headers flow
  into the Swift namespace automatically.
- **Exactly three breaking changes hit our call sites** (header diff
  pin→tip, cross-checked against every symbol we call):
  1. `ghostty_terminal_mode_get/set` removed (upstream `cfc19e805`,
     "ABI BREAKING"). Reads now go through `ghostty_terminal_get(t,
     GHOSTTY_TERMINAL_DATA_MODE, &cfg)`; writes through
     `ghostty_terminal_set(t, GHOSTTY_TERMINAL_OPT_MODE = 34, &cfg)`
     (`OPT_MODE_DEFAULT = 33` exists for RIS defaults; unused here).
     `GhosttyTerminalModeConfig` is a **plain 4-byte struct**
     `{GhosttyMode mode; bool value}` — NOT the sized-struct pattern
     (verified by compiled sizeof + header read). Callers:
     `crates/roost-vt/src/terminal.rs:479-495` (`mode_get`), Swift
     `TerminalView.swift` `isDecModeEnabled`.
  2. `ghostty_render_state_colors_get` removed (upstream `b4079f00c`) →
     `ghostty_render_state_get(state, GHOSTTY_RENDER_STATE_DATA_COLORS
     = 19, &colors)` with `GHOSTTY_INIT_SIZED(GhosttyRenderStateColors)`
     (tip `render.h:209-214,346-352`). Callers:
     `crates/roost-vt/src/render_state.rs:284`, Swift
     `mac/Sources/Roost/RenderState.swift:385`.
  3. `ghostty_terminal_new` now `(allocator, terminal, uint16 cols,
     uint16 rows)` — `GhosttyTerminalOptions` gone; scrollback limits
     move to `ghostty_terminal_set` (`OPT_SCROLLBACK_MAX_BYTES = 27`,
     `OPT_SCROLLBACK_MAX_LINES = 28`, tip `terminal.h:1359-1402`).
     Callers: `crates/roost-vt/src/terminal.rs:253-261`, Swift
     `TerminalView.swift:445` **plus ten test call sites across five
     Swift test files** (all break when `GhosttyTerminalOptions`
     disappears — inventory them at C1 start with a repo-wide grep).
- `GhosttyResult` gained **three** codes (tip `types.h:90-109`, read
  from the spike headers): `GHOSTTY_IO_ERROR = -5`,
  `GHOSTTY_LIMIT_EXCEEDED = -6`, `GHOSTTY_REJECTED = -7`. Rust
  hand-mirrors codes as literals in `crates/roost-vt/src/lib.rs:61-97`
  (`Error::from_result`, -1..-4) — add all three variants there. Swift
  has **no error-enum mirror** (call sites test `rc == GHOSTTY_SUCCESS`
  / `rawValue != 0` directly) — no symmetric Swift work exists.
- **Stable pin→tip** (verified by diff): `GHOSTTY_MODS_*` and
  `GHOSTTY_KEY_*` enums byte-identical; `-Demit-lib-vt` flag and header
  layout unchanged; `ghostty_mode_new` packing macro unchanged in shape
  (Swift reimplementation at `TerminalView.swift:2186-2194` — re-verify
  during C1, low risk). Every other symbol Roost calls survives with an
  identical signature.
- #334 API present at tip (verified in spike headers):
  `ghostty_terminal_grid_ref_track` +
  `ghostty_tracked_grid_ref_{free,has_value,point,set,snapshot}`.
  Tracked refs return `GHOSTTY_NO_VALUE` when the tracked location was
  **pruned or discarded** (`grid_ref_tracked.h:67,121-127`) — they
  follow content only while it remains representable.
- #335 APIs present at tip (verified):
  `ghostty_terminal_selection_format_alloc`,
  `ghostty_render_state_begin_update`/`_end_update`.
- CI: `jdx/mise-action@v4` installs from `.mise.toml` (zig bump flows
  through CI, release.yml, and the shed provisioning); vendored-ghostty
  cache keys = `hashFiles('third_party/ghostty/build.sh')` in ci.yml
  (6 keys) and release.yml (3, arch-keyed) — the SHA bump rotates them
  all automatically. `ci.yml:8-12` triggers `pull_request` only for
  base branches `main` and `poc/iced` — **a PR based on a feature
  branch gets no CI** (this shaped D7).
- Known tripwires designed to fire on a bump:
  `crates/roost-vt/tests/render_dirty_test.rs` (456 lines; upstream did
  render-state perf + dedicated dirty-row APIs since the pin — most
  likely site of real triage), `selection_test.rs` pinned struct sizes,
  `theme_vs_osc_override_test.rs`, `write_pty_test.rs`.
- Pinned struct sizes verified to **hold at tip** by compiled sizeof
  against spike headers: `GhosttyGridRef` 24, `GhosttySelection` 64,
  `GhosttyFormatterTerminalOptions` 56, `GhosttyFormatterTerminalExtra`
  32, `GhosttyFormatterScreenExtra` 16 (also `GhosttyRenderStateColors`
  792, `GhosttyMouseEncoderSize` 40, `GhosttyStyle` 72,
  `GhosttyTerminalModeConfig` 4).
- The selection-formatter UB precondition (`Selection.order()` unchecked
  `pointFromPin(...).?` under ReleaseFast) is **still not fixed at
  tip** — the new `selection.h` codifies it as a precondition. The
  pin/format/free-in-one-synchronous-call structure in
  `crates/roost-vt/src/formatter.rs` and
  `mac/Sources/Roost/SelectionFormatter.swift` stays mandatory through
  every workstream here. The formatter additionally requires both
  endpoints to belong to the terminal's **currently active screen**
  (see D5).
- Scrollback semantics: the pin's `GhosttyTerminalOptions.max_scrollback`
  is documented "Maximum number of **lines** to keep in scrollback
  history"; roost passes line counts (2000 in both UIs —
  `terminal.rs:36-38`, `crates/roost-iced/src/app/terminal_tab.rs:295`,
  `TerminalView.swift:442`; tests use 0/10/100).
- Spike (all green, artifacts in the plan's artifact dir): ghostty tip
  built with zig 0.16.0 on macOS 26 arm64 **without the SDK shim**
  (plain `zig build -Demit-lib-vt=true -Doptimize=ReleaseFast
  -Dcpu=baseline`, exit 0, 10.8 MB `libghostty-vt.a`); link-smoke
  calling `ghostty_terminal_new(NULL,&t,80,24)` + `vt_write` +
  `ghostty_terminal_get(GHOSTTY_TERMINAL_DATA_MODE,…)` runs clean.
  NOT yet exercised against tip: bindgen generation and a swift build
  through the `CGhosttyVT` umbrella — C1 front-loads both as a smoke
  before porting call sites.

## 3. Design decisions (PINNED)

### D1 — Target SHA and toolchain
Pin `f2d5758f6305867dc36b36293c6165d8152b853e` (main tip, 2026-08-26)
exactly. zig `0.16.0` in `.mise.toml` and `build.sh`'s version check
(accept `0.16.x`). C1 **removes the macOS-26 SDK shim**
(`build.sh:56-126`) — spike-proven unnecessary under zig 0.16 on the
exact machine class it guarded; commit message records the revert path.
Fallback rule: if the pinned SHA fails a gate, slide back to the newest
SHA that (a) builds lib-vt clean, (b) contains the #334/#335 symbol set
and the three ported API shapes — then rerun the header diff + sizeof
spike, update this plan's SHA and AC1, and note the substitution in the
C1 commit message. Alternative rejected: #333's `74d0c72f` half-bump
(misses everything strategic; two rounds of tripwire triage).

### D2 — Keep bindgen; tracked-ref wrapper requirements (inline)
No libghostty-rs adoption in this plan. The new tracked-ref wrapper
(C2) must satisfy, in roost-vt's own idiom:
- RAII: `Drop` calls `ghostty_tracked_grid_ref_free`.
- **Terminal identity:** the wrapper stores the owning terminal's raw
  handle and every operation that takes `&Terminal` checks it against
  the stored handle (mismatch → `Error::InvalidValue`), since upstream
  does not check.
- **No type-level lifetime claim over snapshots:** the current `GridRef`
  has no lifetime parameter (`terminal.rs:177`), and adding one is out
  of scope. Instead, raw snapshots stay **private to the synchronous
  formatter path** — `snapshot` is `pub(crate)` (or private), called
  only inside the single pin/format/free call that already holds
  `&Terminal` for its whole extent. Public API exposes only
  `has_value`/`point`/`set`.
(The libghostty-rs `TrackedGridRef` was the design reference; its
essential content — identity validation + snapshot confinement — is
fully stated above and the plan does not depend on that checkout.)

### D3 — Mode API port shape
`Terminal::mode_get(&self, mode: u16) -> bool` **keeps its current
one-argument public signature** (`terminal.rs:479`; callers
`crates/roost-iced/src/app/terminal_tab.rs:975`,
`interactions.rs:1807` unchanged). Internally it builds
`GhosttyTerminalModeConfig { mode, value }` with the packed DEC-private
mode (same `mode as _` packing as today; DEC-private = ANSI bit clear)
and calls `ghostty_terminal_get(t, GHOSTTY_TERMINAL_DATA_MODE, &cfg)` —
proven in the spike link-smoke. Swift `isDecModeEnabled` twin same
shape. No new modes adopted; `OPT_MODE`/`OPT_MODE_DEFAULT` writes not
used.

### D4 — Scrollback limits port shape
`TerminalOptions { cols, rows, max_scrollback }` stays the roost-vt
constructor type, unit = **lines** (verified §2). Port: construct the
RAII `Terminal` from `ghostty_terminal_new(NULL, &t, cols, rows)`
**first**, then apply `ghostty_terminal_set(t,
GHOSTTY_TERMINAL_OPT_SCROLLBACK_MAX_LINES, &n)` — always, including
`n = 0` (tests rely on 0 = disabled scrollback) — so a failed `set`
returns `Err` and the already-constructed owner frees the terminal (no
leak). NOT `_MAX_BYTES` (that would turn "2000 rows" into ~2 KB).
Swift twin same order. **Pinning test (C1):** after construction with
0 and 2000, query `GHOSTTY_TERMINAL_DATA_SCROLLBACK_MAX_LINES` (or the
tip's read equivalent) and assert the configured value round-trips.
**Known triage hazard:** tip documents line pruning as page-granular
("actual available scrollback lines will almost always be higher than
configured"); tests forcing eviction with tiny limits
(`selection_test.rs` eviction cases,
`crates/roost-iced/src/app/interactions.rs:2176,3612,3667`) may see
different eviction timing — adjust test setups (write enough rows to
cross page boundaries), never weaken assertions.

### D5 — #334 tracked refs (C2) — normative here; issue text is background
- New `crates/roost-vt/src/tracked_ref.rs` per D2, plus
  `Terminal::track` returning `Result<TrackedRef>` (OOM propagates —
  repo convention is errors returned, not swallowed).
  `TerminalSelection::begin/update/set` change from `bool` to
  `Result<bool>` (or equivalent) — audit + update iced callers.
- `CellSelection` holds two tracked refs instead of two screen-Y
  scalars (`selection.rs:86-92`) — endpoints resolve **both X and Y**
  from the tracked refs (upstream tracks through resize/reflow in both
  axes; keeping scalar columns would silently lose X tracking).
  Consequence: `CellSelection` (and types embedding it) lose
  `Copy`/`Clone`/`Eq` — audit consumers (`selection.rs:143` area,
  iced call sites) as part of C2.
- Visibility queries via `_point(ref, VIEWPORT, …)`;
  `GHOSTTY_NO_VALUE` → `None`.
- **Active-screen boundary:** tracked refs stay attached to the screen
  (primary/alt) where they were created and can still snapshot while
  that screen is inactive — but the formatter requires endpoints on the
  **active** screen. Store the `ActiveScreen` at selection start;
  while the terminal's active screen differs, `selected_text()` returns
  `None` and the selection is not drawn; it may reappear when the
  owning screen is active again. Assert (debug) screen identity before
  every snapshot/format.
- `formatter.rs:84`: snapshot each endpoint immediately before building
  `GhosttySelection`, inside the same synchronous call (D2).
- Swift twin: `TerminalView.swift` screenY/viewportRow round-trips
  (~:1417/:1443/:1662/:1857) + `SelectionFormatter.swift` — mechanical
  mirror of the Rust design.
- **Eviction tests (replaces the single renamed test):** two scenarios,
  Rust + Swift twins:
  1. Rows *older than* the selection are pruned while the selected row
     survives → selected text still `MARKER` (selection follows
     content).
  2. The selected row *itself* is pruned → `selected_text()` returns
     `None` — never drift onto another row. (Tracked refs cannot follow
     discarded content; `evicted_history_follows_content` alone would
     promise the impossible.)
  Plus a tracked-ref unit battery: invalid coordinates, wrong-terminal
  pairing, terminal reset, inactive-screen handling, resize/reflow,
  reversed (anchor-after-cursor) selection, drop/free discipline.
- Docs that assert the old drift behavior change **in C2, not C5**:
  `terminal.rs:93-99` (PointTag::Screen doc) + `terminal.rs:98-99`
  ("the C API does not export them"), `docs/reference/config.md`
  eviction caveat, `docs/reference/ipc.md:996` (document what
  `selection.dump`/selected text report when tracked content is
  discarded).
- Cross-UI regression: add a permanent case to
  `tools/roosttest/test_selection.py` driving scrollback past the limit
  with an anchored selection, asserting follows-then-None via the IPC
  op set (runs in `e2e-iced` + `e2e-mac`; note the enumerated-CI-list
  gotcha does not apply — the module already runs; only new modules
  need Makefile/ci.yml list edits).

### D6 — #335 adoptions (C3, C4) — normative here; issue text is background
C3: `ghostty_terminal_selection_format_alloc` replaces the
formatter-new/format/free dance in `formatter.rs:43-67,120-146` and
`SelectionFormatter.swift:97-108` — one FFI call per copy, keeping the
pin/format/free-in-one-call structure, `UNWRAP_SOFT_WRAPPED_LINES`, and
`trim: false`. Scope note: this is the **formatter fallback path
only** — fully-visible selections keep the render-state fast path;
the existing fast-path/slow-path equivalence tests prove no behavior
change.
C4: replace the fused `ghostty_render_state_update`
(`render_state.rs:254-262`; Swift twin `RenderState.swift:74-79`) with
`begin_update` + `end_update` **inside the same wrapper method** —
public shapes unchanged, so `render_dirty_test.rs` exercises the split
directly. Motivation is **mechanical API modernization** (staying
current with upstream's direction; a prerequisite for any future
off-main-thread render design) — NOT a lock win: both UIs own the
terminal on the main thread and no caller-held lock exists. Error
sequencing: call `end_update` only after `begin_update` succeeded;
propagate failures identically in Rust and Swift. Swift gets the same
mechanical twin (both wrappers use the fused call today). Explicitly
NOT adopting `ghostty_terminal_select_word/_line/_output` — the
toolkit-neutral word-selection corpus (`tests/word-fixtures/`) stays
canonical.

### D7 — PR structure: three PRs, all targeting main
`build.sh:20-21` pins the repo convention that the SHA bump lands in
its own PR; `ci.yml:8-12` means a PR must target `main` to get CI. So
all three PRs target **main**, opened as a stack:
- **PR A** `feature/plan-032-ghostty-tip-bump`: C1 + C5.
- **PR B** `feature/plan-032-tracked-selection` (branched from A): C2.
  PR body: "stacked on PR A — review commits after <A-head>".
- **PR C** `feature/plan-032-selection-format-adoption` (branched from
  B): C3 + C4, same stacking note.
B and C initially show predecessor commits in their diff; after A
merges, rebase B onto main and update; same for C. Every PR gets a
real `ci-success` run this way. All PRs left open for Charlie's
review/merge (manual merges per CLAUDE.md). Issue linkage: PR A body
carries `Closes #333` (superseded-by disposition comment posted on the
issue), PR B `Closes #334`, PR C `Closes #335` — closure happens at
merge; the AC requires the keywords + status comments, not closed
issues.

### D8 — Post-bump issue filing (W4, ship phase — no commits)
File new issues: snapshot-API adoption (host-sessions attach +
scrollback persistence, links `discovery/host-sessions.md`); native
desktop-notification/progress effects (relates #258; notes the
OPT_USERDATA single-slot multiplexing prerequisite);
`ghostty_terminal_paste` adoption (note `GHOSTTY_REJECTED` unsafe-paste
flow); idle scrollback compression; libghostty-rs
revisit-at-next-release. Comment on existing issues where the bump
changes their status: #188 (OSC 52 `clipboard_read` effect now
upstream), #209 (XTGETTCAP/size-report/enquiry effects now
answerable), #169 (semantic-prompt C API now exists). Each issue names
the enabling upstream commit(s).

### D9 — Orchestration notes (executor metadata, not plan substance)
Fable orchestrates. C1 → opus (fable takes over render-dirty triage
only if semantics genuinely moved). C2 → opus. C3/C4 → opus. C5 →
sonnet. Implementers run gates synchronously in the foreground and do
NOT commit; commits go through the gated-commit flow.

## 4. Deviations / non-goals

- No libghostty-rs adoption (deferred; tracking issue instead).
- No new capability adoption (snapshot, paste, OSC 52, notification
  effects, XTGETTCAP) — issues only (D8).
- No word-selection API swap (D6).
- No facade (#286) revival; Swift changes stay mechanical twins.
- No `GridRef` lifetime-parameter refactor (D2).
- No zig-0.16 code modernization beyond what the build requires.

## 5. Work breakdown (gated commits)

- **C1 (PR A, opus)** — Toolchain + pin bump + port.
  Order: (1) `.mise.toml` zig → 0.16.0; `build.sh` SHA → `f2d5758f…`,
  zig check → 0.16.x, delete the SDK shim, rewrite the `:22` comment;
  `./third_party/ghostty/build.sh --force`. (2) **Smoke before
  porting:** `cargo build -p roost-vt --features ffi` (bindgen over the
  31 tip headers) and `cd mac && swift build` (CGhosttyVT umbrella) —
  discover generation/namespace breakage in minutes, not mid-port.
  (3) Port the three breaking call sites in Rust (`terminal.rs`,
  `render_state.rs`) and Swift (`TerminalView.swift`,
  `RenderState.swift:385`, + the ten `ghostty_terminal_new` test call
  sites across five Swift test files — grep-inventory first). D3/D4
  shapes. (4) Add `Error::{IoError, LimitExceeded, Rejected}` + a
  table-driven `from_result` test over `0, -1..-7` + unknown-code
  fallthrough. (5) D4 scrollback round-trip pinning test. (6) Triage
  tripwire tests — every re-pinned expectation individually justified
  in the commit message; re-verify Swift `ghostty_mode_new` packing +
  `ActiveScreen` numeric assumption (`terminal.rs:537-543`).
  Note: CI's restored cargo `target/` self-heals after the vendored
  cache rotates (`build.rs` rerun-if-changed on header + archive) — a
  confusing first-run failure should not be mis-triaged as this.
  **Gate:** `./third_party/ghostty/build.sh --force` + `cargo test -p
  roost-vt --features ffi` + `make check` + `cd mac && swift build &&
  swift test`.
- **C5 (PR A, sonnet)** — Docs/comment/changelog sweep:
  `third_party/ghostty/README.md` (old SHA), CLAUDE.md zig/pin
  references, `docs/reference/terminal-queries.md:184` (names the
  removed mode getter), `docs/development/*` stale pin statements,
  stale SHA refs in `formatter.rs`/`SelectionFormatter.swift` module
  docs, `CHANGELOG.md` entry (toolchain bump, new error variants,
  selection-eviction semantics).
  **Gate:** `make check` + `make docs`.
- **C2 (PR B, opus)** — #334 per D5 (includes its doc edits + the
  roosttest case).
  **Gate:** `cargo test -p roost-vt --features ffi` + `make check` +
  `cd mac && swift build && swift test` + `make docs` (config.md/ipc.md
  touched) + `ROOST_TEST_MODE=1 make e2e-iced`.
- **C3 (PR C, opus)** — #335 formatter adoption per D6.
  **Gate:** `cargo test -p roost-vt --features ffi` + `make check` +
  `cd mac && swift build && swift test`.
- **C4 (PR C, opus)** — #335 begin/end_update per D6.
  **Gate:** same as C3, plus `ROOST_TEST_MODE=1 make e2e-iced`.

## 6. File map (indicative)

- `.mise.toml`; `third_party/ghostty/build.sh`;
  `third_party/ghostty/README.md`; `CHANGELOG.md`
- `crates/roost-vt/src/{lib,terminal,render_state,selection,formatter}.rs`,
  new `crates/roost-vt/src/tracked_ref.rs`
- `crates/roost-vt/tests/{render_dirty,selection,mode,write_pty,theme_vs_osc_override}_test.rs`
  (+ new tests per D4/D5)
- `crates/roost-iced/src/app/{terminal_tab,interactions}.rs` (selection
  Result plumbing + test scrollback setups)
- `mac/Sources/Roost/{TerminalView,RenderState,SelectionFormatter,Theme}.swift`;
  `mac/Tests/RoostTests/*` (five files with raw `ghostty_terminal_new`
  calls + new twins)
- `tools/roosttest/test_selection.py`
- `docs/reference/{config,ipc,terminal-queries}.md`,
  `docs/development/*`, `CLAUDE.md`

## 7. Acceptance criteria

1. Pin = `f2d5758f6305867dc36b36293c6165d8152b853e` (or a D1-fallback
   SHA recorded in this plan), zig 0.16.0 in `.mise.toml` + build.sh;
   `./third_party/ghostty/build.sh --force` succeeds on macOS 26 arm64
   **with the SDK shim deleted**; `ci-success` green (incl. `e2e-iced`
   + `e2e-mac`) on all three PRs.
2. All roost-vt ffi tripwire suites pass, every re-pinned expectation
   individually justified in commit messages; `from_result` table test
   covers `0, -1..-7`; scrollback-lines round-trip test passes at 0 and
   2000.
3. #334: the two eviction scenarios (older-content-pruned → follows;
   selected-content-pruned → `None`) pass in Rust and Swift, the
   tracked-ref unit battery passes, and the `test_selection.py` case
   passes on both UI targets.
4. #335: selection copy through `selection_format_alloc` is
   byte-identical (equivalence tests unchanged); render wrapper uses
   `begin_update`/`end_update` with unchanged public shape and no
   `render_dirty_test.rs` or e2e regression.
5. PR bodies carry `Closes #333/#334/#335` respectively + disposition
   comments posted on the issues; W4 issue set filed per D8.
6. Verified per §8's per-platform scope: iced live in the shed; Mac via
   local `swift test` + CI `e2e-mac` (no live local Mac run — single
   instance would kill the session's own Roost).

## 8. Verification plan (beyond automated tests)

- **Linux (shed, linux-test skill):** `e2e-iced` lanes + screenshot
  smoke (`tools/screenshot/smoke.sh iced`) at C1 and after C4;
  opencode 256-color canary in shed `test1` (historical
  palette-regression probe — C1's colors port touches exactly that
  path). Artifacts → `032-ghostty-tip-zig016/`.
- **Mac:** local `swift test` only; live behavior via CI `e2e-mac`.
  Do NOT run `make e2e-mac` or a dev Roost.app locally (single
  instance; check `$ROOST_TAB_ID`).
- **Selection behavior (C2):** the permanent `test_selection.py` case
  is the record; a shed IPC drive replays it live for the artifact
  folder.
- **Perf sanity (C4):** `make perf-refresh` / `tools/perf/render-stats.sh`
  before/after in the shed, 3 runs each, flag >10% regression
  (expected neutral). `tools/perf/echo-latency.py` optional
  (measures view cost, not update cost).

## 9. Risks / open items

- **render_dirty semantics moved upstream** (dirty-row API rework
  2026-08-15): triage may reveal real behavior differences; budgeted in
  C1; if `Dirty` semantics changed materially, fable takes over triage
  and the plan gains a panel-reviewed addendum.
- **Scrollback pruning granularity** (D4 hazard): eviction-dependent
  tests may need setup changes; assertions must not weaken.
- **Tip freshness** (same-day SHA): mitigated by tripwires + e2e + the
  D1 fallback rule (which requires re-running the header diff + spike).
- **bindgen/Swift-namespace breakage from 5 new headers**: front-loaded
  smoke in C1 step 2.
- **First CI runs slower** after cache-key rotation (vendored-ghostty
  rebuild per OS, in ci.yml AND release.yml) — expected.
- **Stacked PRs targeting main** show predecessor commits until
  rebased post-merge; PR bodies state the review range. Keep A
  append-only once B exists.
- **`GHOSTTY_REJECTED` unused today** (paste-API safety code) — mapped
  in the error enum now so the future paste adoption can't hit the
  unknown-code fallthrough.

## § Verified (running record — final summary appended at ship)

- 2026-08-26 spike: zig 0.16.0 + tip build clean without SDK shim on
  macOS 26 arm64; sizeof probe (5 pinned sizes hold); link-smoke of the
  new terminal_new + DATA_MODE query. Artifacts:
  `spike-build-zig016-tip.log`, `sizecheck.c/.out`, `linksmoke.c/.out`,
  `spike-notes.txt`.

🤖 Generated with Claude Code

https://claude.ai/code/session_01VVNzooL9ww3TgdMo1UABzb

Summary by CodeRabbit

• New Features

  • Added clearer terminal error reporting for I/O failures, limit violations, and rejected operations.
  • Scrollback limits now apply consistently by line count, including unlimited byte limits.
  • Terminal color and palette queries now receive consistent responses.

• Bug Fixes

  • Prevented duplicate color-query replies and improved theme reset behavior.
  • Improved terminal, color, cursor, keyboard, and mode compatibility.

• Documentation

  • Updated build and installation guidance for Zig 0.16.0 and refreshed the bundled Ghostty version.
  • Removed the obsolete macOS SDK compatibility workaround.

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📒 Files selected for processing (39)

• .mise.toml
• CHANGELOG.md
• CLAUDE.md
• README.md
• crates/roost-engine/src/osc.rs
• crates/roost-engine/src/session.rs
• crates/roost-engine/tests/osc_drain_reply_test.rs
• crates/roost-iced/src/app/servicing.rs
• crates/roost-iced/src/input.rs
• crates/roost-osc/src/lib.rs
• crates/roost-vt/src/key_encoder.rs
• crates/roost-vt/src/lib.rs
• crates/roost-vt/src/mouse_encoder.rs
• crates/roost-vt/src/render_state.rs
• crates/roost-vt/src/terminal.rs
• crates/roost-vt/tests/key_encoder_test.rs
• crates/roost-vt/tests/scrollback_limit_test.rs
• crates/roost-vt/tests/selection_test.rs
• crates/roost-vt/tests/theme_vs_osc_override_test.rs
• crates/roost-vt/tests/write_pty_test.rs
• docs/development/setup.md
• docs/getting-started/installation.md
• docs/reference/architecture.md
• docs/reference/terminal-queries.md
• linux/scripts/build-deb.sh
• mac/README.md
• mac/Sources/Roost/RenderState.swift
• mac/Sources/Roost/TerminalView.swift
• mac/Tests/RoostTests/CGhosttyVTSmokeTests.swift
• mac/Tests/RoostTests/GhosttyTestSupport.swift
• mac/Tests/RoostTests/KeyEncoderTests.swift
• mac/Tests/RoostTests/OscReplyTests.swift
• mac/Tests/RoostTests/RenderResolverTests.swift
• mac/Tests/RoostTests/TerminalViewOscDrainTests.swift
• mac/Tests/RoostTests/ThemeBoldColorTests.swift
• third_party/ghostty/README.md
• third_party/ghostty/build.sh
• tools/roosttest/README.md
• tools/roosttest/test_osc_pipeline.py

💤 Files with no reviewable changes (2)

• crates/roost-iced/src/app/servicing.rs
• mac/Tests/RoostTests/OscReplyTests.swift

🚧 Files skipped from review as they are similar to previous changes (34)

• docs/getting-started/installation.md
• mac/README.md
• linux/scripts/build-deb.sh
• docs/development/setup.md
• mac/Sources/Roost/RenderState.swift
• mac/Tests/RoostTests/GhosttyTestSupport.swift
• mac/Tests/RoostTests/RenderResolverTests.swift
• crates/roost-vt/tests/selection_test.rs
• crates/roost-vt/tests/theme_vs_osc_override_test.rs
• README.md
• mac/Tests/RoostTests/KeyEncoderTests.swift
• crates/roost-vt/src/key_encoder.rs
• mac/Tests/RoostTests/CGhosttyVTSmokeTests.swift
• third_party/ghostty/README.md
• .mise.toml
• crates/roost-vt/tests/write_pty_test.rs
• mac/Tests/RoostTests/ThemeBoldColorTests.swift
• CLAUDE.md
• crates/roost-vt/tests/key_encoder_test.rs
• crates/roost-vt/src/mouse_encoder.rs
• crates/roost-iced/src/input.rs
• CHANGELOG.md
• crates/roost-vt/src/terminal.rs
• third_party/ghostty/build.sh
• crates/roost-vt/tests/scrollback_limit_test.rs
• crates/roost-vt/src/render_state.rs
• docs/reference/architecture.md
• crates/roost-vt/src/lib.rs
• tools/roosttest/README.md
• crates/roost-engine/tests/osc_drain_reply_test.rs
• crates/roost-engine/src/session.rs
• crates/roost-osc/src/lib.rs
• mac/Sources/Roost/TerminalView.swift
• crates/roost-engine/src/osc.rs

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---

📝 Walkthrough

Walkthrough

The project upgrades Zig and libghostty-vt, adapts terminal and render-state bindings to new APIs, moves OSC query replies to libghostty, configures scrollback after terminal creation, and updates regression coverage.

Changes

Ghostty and Zig integration

Layer / File(s)	Summary
Toolchain and ABI updates .mise.toml, third_party/ghostty/..., docs/..., README.md, CLAUDE.md, CHANGELOG.md, crates/roost-vt/..., crates/roost-iced/src/input.rs	Build metadata now uses Zig 0.16.x and libghostty-vt commit f2d5758f6. Typed Ghostty aliases replace raw integer declarations. New result codes map to public Error variants.
Terminal lifecycle and rendering APIs crates/roost-vt/src/terminal.rs, crates/roost-vt/src/render_state.rs, mac/Sources/Roost/..., crates/roost-vt/tests/..., mac/Tests/RoostTests/...	Terminal creation passes dimensions directly. Scrollback is configured after creation, with byte limits cleared. Mode, screen, color, and enum reads use updated Ghostty APIs.
Behavior regressions and documentation crates/roost-vt/tests/selection_test.rs, crates/roost-vt/tests/theme_vs_osc_override_test.rs, docs/reference/...	Tests cover page-granular selection eviction and OSC override reset behavior. Architecture and terminal-query documentation describe the updated APIs and reply flow.

OSC query reply ownership

Layer / File(s)	Summary
Libghostty OSC reply ownership crates/roost-engine/src/osc.rs, crates/roost-engine/src/session.rs, crates/roost-osc/src/lib.rs, crates/roost-iced/src/app/servicing.rs, mac/Sources/Roost/TerminalView.swift	OSC color and palette queries pass through the scanner. libghostty emits replies through write_pty. Roost-side response formatters and PTY-input actions are removed.
OSC state and reply validation crates/roost-vt/tests/write_pty_test.rs, crates/roost-engine/tests/osc_drain_reply_test.rs, mac/Tests/RoostTests/TerminalViewOscDrainTests.swift, tools/roosttest/...	Tests validate state tracking, exact replies, wire ordering, terminators, palette probes, and exactly one reply per query across Rust, Swift, and Python paths.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to 3ae2e

One terminal-query documentation example could mislead readers by showing the same reply selector for three different requests, while runtime behavior remains correct. This is a localized documentation fix and does not block merge.

Sequence Diagram(s)

sequenceDiagram
  participant TerminalView
  participant OscRouter
  participant libghostty_vt
  participant write_pty
  TerminalView->>OscRouter: scan OSC query bytes
  OscRouter-->>TerminalView: pass through query without PTY action
  TerminalView->>libghostty_vt: write query bytes
  libghostty_vt->>write_pty: emit one color or palette reply
  write_pty-->>TerminalView: deliver reply bytes

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.41% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 122 functions across 27 files. (11 skippe…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the two primary changes: the libghostty-vt pin update and the Zig 0.16 upgrade.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 75.41% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 122 functions across 27 files. (11 skipped: 11 unsupported.)

✨ Finishing Touches 💡 1

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• Create stacked PR
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• Create PR with unit tests
• Commit unit tests in branch feature/plan-032-ghostty-tip-bump

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Actionable comments posted: 1

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Inline comments:
In `@docs/reference/terminal-queries.md`:
- Around line 103-105: Update the OSC color query entry to document
selector-specific replies: show separate response examples for OSC 10, OSC 11,
and OSC 12, with each reply preserving its corresponding request selector while
retaining the pinned engine-default formatting and terminator behavior.

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• crates/roost-engine/src/osc.rs
• crates/roost-engine/src/session.rs
• crates/roost-engine/tests/osc_drain_reply_test.rs
• crates/roost-iced/src/app/servicing.rs
• crates/roost-osc/src/lib.rs
• crates/roost-vt/tests/write_pty_test.rs
• docs/reference/architecture.md
• docs/reference/terminal-queries.md
• mac/Sources/Roost/TerminalView.swift
• mac/Tests/RoostTests/OscReplyTests.swift
• mac/Tests/RoostTests/TerminalViewOscDrainTests.swift
• tools/roosttest/README.md
• tools/roosttest/test_osc_pipeline.py

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• crates/roost-iced/src/app/servicing.rs
• mac/Tests/RoostTests/OscReplyTests.swift

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