# claude-cloak TUI that displays Claude Code's API streams token-by-token (thinking, text, tool calls) by acting as a pass-through proxy: Claude Code points `ANTHROPIC_BASE_URL` at `127.0.0.1:8484`, we forward everything verbatim to `api.anthropic.com` and tee SSE responses into the UI. **Never issue API requests of our own** — zero extra usage is the core constraint of this project. ## Architecture ``` src/main.rs entry; tokio runtime for proxy task, TUI on main thread; --headless mode src/proxy.rs axum fallback handler: buffers request body (for session metadata, tool results, and user prompts — `app::record_user_prompt` lifts the trailing user message into a Kind::User feed entry verbatim (incl. slash-command machinery — the goal is to show everything the model received, never filter it). On a turn-starting request (tools present) it also emits the system-prompt *size* as a Kind::System line (the prompt itself is too long to show) and the available tool set as Kind::ToolDefs — each once, re-emitted only on change (system/tools/history are re-sent every request but are not new data). A *side* request (no tools — topic/title haiku calls) is still shown, tagged with a `── side request ──` Meta divider. `app::extract_user_text` splits a user text block into its injected `` spans (kept as dimmed Kind::Reminder entries, never discarded — the prompt survives even when it shares its block with a reminder, the first-message-after-resume case) and the real prompt; `strip_injected` is the label-only projection (drops reminders *and* slash-command machinery) used for turn-tree labels. Dedup drops only true resends (the just-recorded prompt is still the tail entry), so verbatim repeats in later turns survive. Also reads the `x-claude-cloak-pane` header (passed to `Tap::new` to bind the embedded pane — see the embed-identity invariant) and strips it before forwarding. Forwards via reqwest, streams the response back unbuffered, tees SSE src/sse.rs incremental SSE parser; tolerant of chunk splits mid-event/mid-UTF-8 src/app.rs Arc> shared state; Tap = one in-flight tapped request, translates SSE events → session Entries (Drop closes it out) src/ui.rs ratatui rendering @ ~30fps; session list + scrollable feed (FeedCache: per-entry rendered lines + wrapped heights, only changed entries re-render; the viewport window of lines is handed to ratatui so scroll state is usize end-to-end). Focus accent is orange (`ACCENT` = indexed 208): borders, the scroll thumb and the user-prompt blocks all use it when focused, dim grey when not. User prompts render as full-width filled rectangles padded to exactly the inner width (`wrap_words` + exact pad, never the Paragraph's own wrap, so the box ends flush with the borders); the fingerprint folds feed-focus in for `Kind::User` only, so a focus toggle re-renders just those blocks. `color_on(bg)` picks black/white text by background luminance (used by the prompt blocks and the edit/diff blocks) so filled blocks stay legible under any terminal theme. Injected ``s and the system-prompt-size `Kind::System` line show dim under the "system" filter; the `Kind::ToolDefs` tool-list line shares the "tools" filter with tool calls. The feed's right border doubles as a prompt minimap: `*` markers show where each user message sits in the whole conversation, with the scroll thumb drawn on top where they coincide. Sessions panel is a uniform 50% of the main area: each session is a multi-line item — full white title (live = first user prompt via `live_title`, stub = disk label, word-wrapped by `wrap_words`) over a dimmed id·model meta row; expanded turn rows are indented past the title and `truncate_str`'d to one line each. src/markdown.rs wraps tui-markdown: renders GFM tables itself (box-drawing, width-fitted wrapped columns) and strips heading `#` markers — the pinned tui-markdown 0.3.5 does neither src/sessions.rs on-disk session history: background scanner thread keeps App::disk_sessions fresh (~1/s poll, `read_meta` re-read only on mtime change — one pass yields the label *and* the session's last main-chain model, which `App::resume_model` turns into the `--model` a resume spawns with); load_view/load_history rebuild a feed Session from a JSONL transcript (lazily, on first view); build_tree parses uuid/parentUuid chains into a TurnTree (one node per real user prompt; rewinds leave fork points); materialize writes a new session file from a chosen set of turns src/term.rs embedded claude pane: spawns `claude --session-id ` in a portable-pty routed through the proxy; wezterm-term models the screen (and answers terminal queries); renderer paints cells into the ratatui buffer. Each spawn injects a fresh per-pane token via `ANTHROPIC_CUSTOM_HEADERS` (`PANE_TOKEN_HEADER` = `x-claude-cloak-pane`), the correlation handle the proxy uses to recognise the pane's own traffic (see the embed-identity invariant) ``` Data flow: proxy task parses SSE chunks → `Tap::handle()` mutates shared state → UI thread redraws on its own tick (no channel; just the mutex). ## Key invariants - **Latency-neutral pass-through**: response bytes are forwarded as-is, never buffered or rewritten. Auth headers pass through untouched. If the tap code panics or misparses, the proxy must still relay bytes (tee is best-effort): chunks are `try_send`-cloned into a bounded channel and parsed on a separate task (dropped on overflow, never blocking the relay), and the proxy/tap side locks the app mutex poison-tolerantly (`app::lock_app`) so a UI panic can't kill forwarding. - **`accept-encoding` is stripped** from forwarded requests so the upstream sends identity encoding we can parse in transit. Don't "fix" that. - Hop-by-hop headers (`content-length`, `transfer-encoding`, etc.) are stripped both directions; hyper re-frames. - Sessions are keyed by the session UUID in request `metadata.user_id` — Claude Code ≥2.1.x sends a JSON blob with `"session_id":""`, older builds `user_…_session_`; `proxy::session_key` handles both. Concurrent requests (subagents) share a session but each `Tap` tracks its own current entry index — entries/sessions are append-only, so indices stay stable. - **Embed identity is learned from traffic, never assumed from `--session-id`.** Claude Code's interactive `--session-id` is *not* guaranteed to equal the id it reports in request metadata (and a `--resume` can mint a fresh one), so the pane is correlated by a token we control: `term.rs` injects a per-spawn `x-claude-cloak-pane` header (`ANTHROPIC_CUSTOM_HEADERS`), the proxy reads it (and strips it before forwarding), and `Tap::new` *binds* `App::embed_session` to whatever id that tagged request actually carries (`App::bind_embed_session` rebinds + renames a provisional resume row if they differ). Selection policy follows: the embed jumps the selection only on first bind; a brand-new *external* session auto-jumps so a fresh `/clear` is visible **unless** `App::pane_focused` (mirrored from the UI each frame) — never steal the selection from a pane the user is driving. This is what made an `a`-spawned session stream into the wrong row before. - **One app instance = one proxy port = at most one embedded claude** (`EmbedUi::term` / `App::embed_token` → learned `App::embed_session`). `kill_current_embed` is the single teardown path and `bind_new_pane` the single registration path, so pane identity + grow/clear flags can't drift across the spawn/replace call sites. Every other live session is an external claude pointed at our port: observable, never attachable. The pane stays visible while it holds keyboard focus even if the selection isn't on its session yet (its id is still being learned); only an intentional ctrl-↑ / tab-away hides it. - The session list merges live sessions (first, indices stable) with this directory's past sessions from `~/.claude/projects//*.jsonl` as dimmed stubs (deduped by uuid — a live session's file is on disk too). **Tab is viewing only, never a process operation**: selecting a stub lazy-loads its transcript into `App::history`; tabbing off the embedded session hides the pane without killing the child (instant to come back). ctrl-↓ is the commit point that attaches the pane to the selection: reveal+focus if it's the embedded session, `claude --resume ` (kill + respawn) for disk stubs and dead embeds, fresh `--session-id` spawn when there's nothing. Live *external* sessions are guarded — their instance may still run elsewhere and a second `--resume` would fork the transcript — but a second ctrl-↓ within 3s forces it (liveness is unknowable: an idle claude sends no traffic; `EmbedUi::past_embeds` skips the guard for sessions whose instance we killed ourselves). `--session-id` cannot be combined with `--resume` (CLI rejects it without `--fork-session`); `--model` can, and every resume passes it. - **A resume continues on the session's own model**, not the CLI default: `App::resume_model` reads the model Claude Code recorded for the session's last main-chain assistant message (`DiskSession::model`, filled by the scanner's `read_meta` — subagent `isSidechain` records run their own model and `` error records carry no model, so both are skipped) and `app::model_arg_for_id` maps that id to a `--model` argument: a known alias (`sonnet`, `opus`, … from `App::model_choices`) wins over the dated snapshot id, so a retired snapshot can't pin the pane; an id with no alias inside is passed through verbatim (`--model` takes full names too). The transcript is authoritative, so a mid-session `/model` switch is honoured. `[1m]` (1M-context) picks are the one thing it cannot see — the transcript records the same base id either way — so `Session::spawn_model` remembers the exact argument the pane was spawned with in-process and wins **only** while it still names the model the transcript reports. - **Turn tree / branching** (lazygit/yazi-style, all in the sessions panel): `space` (or `→`/`l`) expands the selected session's turn tree — one row per real user prompt, abandoned rewind branches indented `⑂` under their fork point, trunk continuing below. j/k/↑/↓ walk sessions *and* turns (they never scroll the feed; the wheel and PgUp/PgDn/g/G do that). Highlighting a turn switches the feed to the on-disk transcript along the path through that turn and pins the turn's prompt to the viewport top (HistoryView caches per uuid, rebuilt when the leaf changes; FeedCache keys on leaf+live so views of the same uuid don't share slots). `v` anchors a contiguous visual range, `b` materializes a **new fully decoupled session file** — chain root→turn, or exactly the visual range stitched together (sessionId rewritten, each turn's head re-parented onto the previous turn's tail, our own ai-title record gives it the `⑂ …` label) — injected as the selected top stub. Branching never touches a process: ctrl-↓ stays the only spawn/kill commit point. - The tap drives pane behavior: grows it for AskUserQuestion / ExitPlanMode (sized from the question's option count) before Claude Code renders the prompt, shrinks when the tool_result echoes back, and schedules a ctrl-l transcript wipe 400ms after each turn (the pane is prompt-only; the feed shows the context). - Tool input streams as raw JSON fragments; pretty-printed only on `content_block_stop`. Streaming text re-renders markdown on every change (FeedCache fingerprints by content length + done + result), so partial markdown self-heals; completed entries render from cache. ## Gotchas - `tui-markdown` is pinned `=0.3.5`: 0.3.7+ moved to `ratatui-core` (0.30 alpha types), incompatible with ratatui 0.29 — 0.3.6 is the last 0.29-compatible release, but *no* version (through 0.3.8) enables pulldown-cmark's table extension, so upgrading still wouldn't render tables. Its gaps (no tables, literal heading markers) are compensated in `src/markdown.rs`, not by upgrading. - `wezterm-term`/`wezterm-surface` are not on crates.io: pinned to a git rev of the wezterm monorepo (keep both revs identical). - The compact pane *dynamically frames* Claude Code's input box rather than cropping by fixed offsets (`term.rs`: `compact_frame` + `PaneView`). It locates the box by its two horizontal-rule borders (`text_is_rule`) — the last two `────` rules on screen, since the prompt always sits at the bottom — and shows one context row above the top rule (the spinner / "✻ Worked…" row) down to the statusLine just under the bottom rule, cropping the persistent hint/token/effort chrome below it. When an `@`/`/` menu is open it has replaced that chrome with a list (`text_is_menu_item`, CC-2.1.x glyphs — retune there if an update changes them), so the frame extends to the last non-blank row instead. The menu is detected by scanning the *whole* region below the bottom rule for a menu row, not just the row directly under it: the list can start after a blank/header row and only the highlighted item carries a glyph (unselected file rows are plain names), so checking one row collapsed the pane whenever that row wasn't the selected item. Above the top rule the frame also swallows an **active task panel** (`text_is_task_row` / `task_block_top`): Claude Code parks the `N tasks (…)` header + `✔ ◼ ◻` rows (and its `… +N pending` overflow line) directly above the input box, so walking up over that block — tolerating one blank line and single wrapped / activity rows, capped at `MAX_TASK_BLOCK` — makes task status visible with no extra app state. Priority when the pane can't hold everything: the panel is dropped first (`CompactFrame::ess_top`, the one-context-row frame) so the line you're typing and an open menu never fall off screen. The framed region drives the pane height too: `compact_rows` (called from `ui::draw`) measures box-height + tail so the pane auto-expands as the prompt gains lines or a menu opens and shrinks back when idle (floor `MIN_COMPACT_INNER`, cap = screen − 6); `PTY_PAD` keeps the PTY taller than the visible window so the child can still draw the rows we crop. **A cropped PTY is sized to the *whole screen height*, not the visible pane** (`ui::draw` passes `f.area().height` to `resize` for every view except Full): their height is derived by measuring what Ink has already drawn, and Ink only ever draws as many rows as the PTY reports, so tying the PTY to the (small) visible height is a feedback loop — an `@`/`/` menu or a big paste that suddenly needs many more rows than the current PTY+pad never gets the room to draw them, so `compact_rows` can't measure the growth and the pane stays stuck small. A screen-tall PTY lets Ink lay out the full box+menu in one shot; `compact_view_range` still shows only the cropped window. When that window is shorter than an open menu it **top-anchors on the input box** (crop the menu's tail, never the line you're typing) — the idle no-menu case still bottom-anchors on the statusLine. That per-frame measurement is smoothed by hysteresis (`EmbedUi::compact_height` / `smooth_compact`, seeded at `DEFAULT_COMPACT_INNER`): the pane grows instantly but shrinks only after the smaller height has held for `SHRINK_DELAY` (400ms), and `compact_rows` returns `None` on a transient mid-repaint (box border caught missing) so the last height is kept. Without this the height oscillates every frame during a subagent turn or `@`/`/` menu filtering, and each change resizes the PTY → Ink repaints → flicker. `PaneView::Interactive` (the tap-grown AskUserQuestion / ExitPlanMode pane, whose selection box renders *above* the input) is **measured the same way, never estimated**: `interactive_frame` anchors on the rule above the header-chip row (`← ☐ Header ✔ Submit →`), else the second-to-last rule, and runs to the last non-blank row; `EmbeddedTerm::interactive_rows` feeds that height through the same hysteresis. `App::ask_question_rows` (the row guess from the tool JSON) is only the fallback for the frames before Ink has drawn the box — it can't know how far the question text wraps, which is what used to crop the first paragraph. Because the Interactive PTY is now screen-tall, Claude Code lays the prompt out in full instead of switching to its own truncated form. `interactive_view_range` top-anchors on that frame and slides down only far enough to keep the `❯` option on screen when the prompt overflows the pane. `PaneView::Full` (fullscreen) renders the child's screen verbatim from row 0 with the PTY sized exactly to the pane. Permission-prompt boxes (rounded borders, not rules, and not in the API stream) aren't expanded in the compact pane — consistent with the known "permission prompts aren't detected" limit. - Keybindings avoid Alt entirely: on layouts like dk_mac_fixed, Alt composes characters (alt-c = ©) and never reaches the app as a modifier. Pane keys: F2 toggle, ctrl-↓ attach pane to selected session (resume/spawn/focus), ctrl-↑ focus feed, ctrl-f fullscreen toggle (only while the pane is focused), ctrl-q quit (global; needed while the pane is focused, where plain `q` is forwarded to the child), c attach most-recent past session. List keys: j/k/↑/↓ move the session/turn highlight, space/→/← expand/ enter/leave the turn tree, a opens the model picker popup and spawns a brand-new `claude --session-id … [--model …]` (kills any current pane — `show_embed_new`; saves resume-then-/clear to get a fresh chat). The picker list comes from `App::model_choices`: seeded with `default_model_choices`, then replaced by `term::spawn_model_discovery` — a background scan that reads the live model-alias array (`["sonnet","opus","haiku","fable",…]`) straight out of the installed `claude` ELF (single self-contained binary with the JS bundle embedded). No API call, never runs claude — just resolves `claude` on PATH and greps its bytes for the longest lowercase-token array anchored by `opus`+`sonnet`. The list then gets the **1M-context variants** appended (`sonnet[1m]` etc., Claude Code's `--model` spelling for the long context window): `term::long_context_tokens` collects every quoted `"[1m]"` literal in the same byte scan, and only aliases that really have one are offered (today `opus`/`sonnet`/`fable` — *not* `haiku` or `mythos`), so the suffix is never assumed. `[1m]` needs no shell quoting: the pane spawns via `CommandBuilder` argv, not a shell. Tab/BackTab cycle sessions (`p` no longer mirrors BackTab). v visual range, b branch, Esc unwinds (visual → tree → quit). n/N jump the feed scroll to the next/previous user prompt (`App::prompt_jump`, applied in `draw` where entry heights are cached). The feed scrolls only via wheel / PgUp / PgDn / g / G / n / N. `CT_DEBUG_KEYS=1` shows raw key events in the status bar. - Mouse is captured: wheel always scrolls the feed (regardless of focus), and left-drag selects screen text, copied on release via OSC 52 (like Claude Code). Native terminal selection therefore needs shift held. - Bracketed paste is enabled on the outer terminal (`EnableBracketedPaste`): a multiline paste arrives as one `Event::Paste` and, when the claude pane has focus, is handed to the child via `EmbeddedTerm::paste` (wezterm-term's `send_paste` re-wraps it in bracketed markers iff the child enabled them) — so Claude Code inserts it as one block instead of submitting on the first embedded newline. Paste is ignored when the pane is unfocused (nothing else takes text input). - Pane cursor shape mirrors the child: each frame `draw` records the child's DECSCUSR shape (`EmbeddedTerm::cursor_shape`) into `EmbedUi::cursor_shape` and the event loop emits `SetCursorStyle` only on change (so a blinking cursor isn't reset every frame), resetting to `DefaultUserShape` when no pane cursor is shown / on teardown. Without this the outer terminal kept a stale block cursor regardless of Claude Code's insert-vs-vim-normal state. `term::cursor_style` maps the child's DECSCUSR `Default` to a blinking *bar*, not `DefaultUserShape`: Claude Code's normal input leaves the cursor at the terminal default expecting a bar caret, so forwarding the outer terminal's own default (often a block) would wrongly show a block in insert mode; vim normal mode still sends an explicit `SteadyBlock`. - ratatui needs feature `unstable-rendered-line-info` for `Paragraph::line_count` (used to compute cached per-entry wrapped heights for follow/auto-scroll). - reqwest is `default-features = false` + `rustls-tls,stream` — don't enable compression features (would re-add accept-encoding). - The listener is bound in `main` before the TUI starts: prefers 8484, falls back to an OS-assigned free port so multiple instances coexist (each pane gets the actual port via `ANTHROPIC_BASE_URL`). `CT_PORT` pins the port and turns bind failure into a hard startup error. - Testing: SSE parser has unit tests (`cargo test`). For a live pass-through check: `--headless` (prints the bound port), then POST to `127.0.0.1:/v1/messages` without auth — a relayed 401 from Anthropic proves the round-trip. The TUI can't run in a non-tty. `CT_UPSTREAM` points the proxy at an alternative upstream (e.g. a local fake SSE server) for fully offline end-to-end tests with zero API usage. That fake server is `dev/fake_upstream.py`: it answers every request with canned SSE, so a **real `claude` child** can be made to render its client-side tool UIs on demand (`dev/.fake_scenario` = `ask | plan | todo | taskupdate | text`, switchable mid-run) — this is how the pane's frame detector is developed against what Ink actually draws. Drive it through tmux (`.claude/skills/tui-verify`) and obey that skill's safety rule: **never `pkill`/`killall`**, tear down only your own named tmux session. The child writes real task files under `~/.claude/tasks//`; delete that directory afterwards. ## Not yet handled (known MVP limits) - Non-streaming requests pass through untapped (e.g. `count_tokens`). - Sessions are never pruned (entry memory grows for the process lifetime); the same goes for viewed disk transcripts (`App::history`). - Request bodies are fully buffered (up to 512 MB) before forwarding — needed to read session metadata; adds first-byte latency on huge bodies. - Tool results only appear once the *next* request fires; if the session ends right after a tool call, that result is never seen. Output is what Claude Code sends the model (i.e. post-truncation). - Embedded pane: no mouse forwarding yet; no scrollback view (live screen only); shift+enter needs kitty keyboard protocol pushed on the outer terminal (not done); permission prompts aren't detected for pane growth (not visible in the API stream — would need a Notification hook hitting a local control endpoint). - Materialized branch files satisfy our own parser (round-trip tested) but Claude Code's loader tolerance is only verified empirically by resuming one — if a CC update changes the JSONL schema, retest `b` + ctrl-↓. The tree itself isn't refreshed while expanded (collapse/re-expand re-reads the file), and a highlighted turn of a *live* session views its on-disk transcript, which lags the in-memory feed by however much CC buffers.