The front end is rebuilt on the design tokens the desktop app ships (surfaces, color-mix borders, alpha hovers, accent): a 30-icon inline SVG sprite, dark and light themes, layout switches as deep links (?side=0, ?panel=0, ?theme=light) resolved before the first paint. The empty page is one line and leaves with the first turn; the right rail keeps three cards - todo, file changes (+N -M) and context (tokens, prompt cache hit rate). Both rails animate in and out, and a collapsed rail widens its grid track to 0 instead of being removed, so the transcript never slides into a zero-width column. - src/webui.c: POST /api/workspace - re-root the agent at another directory (permission rules, metrics, AGENTS.md follow) and start a session there, as sessions live per directory; state also reports cached/cache_miss tokens - src/agent_loop.c: cst_agent_set_workspace(), rebuilt prompt and re-measured budget; the auto-compact threshold is 75% of the window (was 60%) - src/tui.c: /web forks a WebUI next to the TUI - separate process and a new session, because cst_webui_run() blocks and two writers corrupt one session - src/os_compat.c, src/os_win.c: run_shell runs without a time limit unless CST_SHELL_TIMEOUT asks for one, so builds and long clones finish - src/main.c, include/cst_webui.h: one CST_WEBUI_DEFAULT_PORT for --help, the docs and /web; Termux opens the browser through termux-open-url - README.md, docs/webui.md, docs/env_openai.md: /web, /api/workspace, the new state fields, the 75% threshold and the layout deep links tests/e2e_webui.sh green (permission round-trip, token paths, --web-dev); make check green.