Use Lemon in a Browser

Last reviewed: 2026-10-15

The full Lemon runtime includes Lemon Web: a browser workspace for coding sessions plus every operator surface (automation, skills, memory, MCP, nodes, models, usage, diagnostics and settings). It talks to the same control-plane methods and events as the TUI, so both clients always show the same sessions, approvals and plan state.

lemon web            # start the runtime if needed, open the browser signed in
lemon web --no-open  # only print the address

The default address is http://127.0.0.1:4080/. Set LEMON_WEB_PORT before launch to choose another port (a source checkout also accepts --web-port N on ./bin/lemon start|daemon). A source checkout uses ./bin/lemon web. lemon web requires the lemon_runtime_full release profile; reinstall with LEMON_PROFILE=full if the launcher reports the minimal profile.

Sign in

Lemon Web uses the control plane's operator token, the same credential the TUI uses (LEMON_CONTROL_PLANE_OPERATOR_TOKEN, normally the launcher-managed token). lemon web opens /login#token=…: the token travels in the URL fragment, which browsers never send to a server, and the page removes it from history before signing in. Otherwise paste the token on the login page.

• The server checks the token and keeps only a derived marker in a signed, encrypted, httpOnly cookie. Rotating the operator token signs every browser out.
• Every page requires sign-in. Without a configured token the UI returns 503, unless LEMON_CONTROL_PLANE_ALLOW_UNAUTHENTICATED_LOOPBACK=true is set and the browser connects directly from loopback.
• Repeated wrong tokens from one address are throttled for a minute.
• Sign out from the bottom of the navigation rail or Settings → Operator.

LEMON_WEB_ACCESS_TOKEN, ?token= URLs and the /manage pages were removed; use the operator token and the pages below.

Layout, themes and keyboard

The navigation rail groups Workspace (Chat, omp, Sessions), Automate, Knowledge, Runtime and System. On phones it becomes a drawer behind the menu button. Choose light, dark or system theme at the bottom of the rail or in Settings (⌘⇧L / Ctrl+Shift+L cycles it).

Keys	Action
⌘K / Ctrl+K	Command palette: pages, actions, sessions; Tab or a leading / searches everywhere (session content, memory, cron jobs)
?	Every shortcut, grouped
g then a letter	Go to a page (g c chat, g s sessions, g a automation, g m models, …)
⌘/	Focus the composer
⌘.	Stop the active run
⌘⇧O	New session
⌘⇧P	Toggle plan mode
⌘⇧M	Model picker; Shift+Tab in the composer cycles thinking level
⌘B / ⌘I	Toggle the sessions sidebar / inspector
⌘\	Split view
Alt+↑ / Alt+↓	Previous / next session
Alt+O / Alt+R	Expand all tool output / the latest tool or thought
/	Focus the filter on list pages; j/k, Enter on the session manager

Ctrl replaces ⌘ off macOS. The palette's chat actions (fork, compact, plan, stop, inspector, split, pickers) appear only on a chat page.

Notifications: the bell lists recent run completions and approval requests from sessions other than the one in front of you. Enable desktop alerts there or in Settings; they appear only while the tab is in the background.

Chat

Chat (/) starts a session: describe the task, choose the workspace folder (recent folders are one click) and optionally a profile. The page lists active and recent sessions. If setup is incomplete it explains what is missing and keeps sending disabled; run lemon setup, then Check again.

A session opens at /chat/<session-key>:

• Sidebar: search, new, rename, pin, archive, fork, open in split, and a dot on sessions with a running agent.
• Header: inline rename, run status, plan indicator, context gauge, split, fork and a menu with exports and the session manager. The toolbar holds the model, thinking-level and tool-policy pickers ("Ask before commands & edits" requires approvals).
• Transcript: answers stream as Markdown with highlighted, copyable code. Thinking is collapsible. Tool cards show shell commands with live output, exit status and duration; file reads with line ranges; edits as diffs; searches with match counts; todo checklists; subagents with status and links. Each run ends with model, duration, tokens and cost.
• Composer: Enter sends, Shift+Enter adds a line, attachments (up to five files of 20 MB; paste or drop images). Images can total at most 10 MB per message. While Lemon works, choose Follow-up (queued for after the run), Steer (guidance for the current run; ⌘Enter) or Redirect (new direction, finished tool work kept), or Stop.
• Approvals appear in the conversation: Approve once, for the session, always, or Deny. Answers given in the TUI or another tab clear the card.
• Plan mode (⌘⇧P) keeps the agent read-only. Its proposal appears as a plan card: Approve & execute runs it, Refine sends it back and focuses the composer for your feedback. Leaving plan mode never approves a plan.
• Inspector (⌘I): Context (window usage by category, largest items, auto-compaction threshold, Compact), Plan, Changes (git status of the session folder with unified or split diffs), Subagents and Details.
• Split view: ⌘\ or "Open in split" shows two sessions side by side (/chat/<key>?split=<other-key>); each pane runs independently.

After reconnecting, the page uses the same bounded sessions.snapshot authority as the TUI. It replaces the selected branch's transcript, tool states, current approvals, todo/plan projection, and owned child/process status rather than replaying missed mutations. An approval answered elsewhere does not remain actionable. Unknown process/tool outcomes stay unknown; recovery never reruns them.

If the event queue overflows, live delivery is fenced until reconciliation succeeds. Events racing a snapshot cause a bounded retry; a failed owner read shows recovery as unavailable, not as proof that a run finished. Recovered active answers are refreshed as replacement snapshots (on the existing status cadence) rather than appended to uncertain old deltas. Terminal state comes from the same authority, so the final answer is shown once. Recovery responses are bounded and credential-redacted; an omitted tail is not proof of a complete transcript. Controls that change state remain disabled while disconnected; nothing is queued offline. See the delivery boundary for paths that remain best effort.

Sessions and profiles

Sessions (/sessions) searches titles, keys, prompts and answers, with Active/Archived/All tabs, a pinned filter and an agent/profile filter (all kept in the URL). Rows open in chat or inspection and offer rename, pin, archive, fork, JSON/Markdown export and delete; bulk select pins or archives. Working now shows live runs. Delete and Prune always preview the exact sessions first and refuse if anything changed since. Exports and inspection are redacted.

Profiles (/profiles): create, clone and rename preview first; delete requires typing the profile ID and moves its home to trash; Export downloads a credential-safe JSON file; Open chat goes to the profile's stable session.

omp

omp (/omp) lists live and recent omp sessions with status, activity, todos, tokens and cost, and lets you start, resume, steer, queue a follow-up, cancel a turn and close a session. When omp is not installed the page says so.

Automation and blueprints

Automation (/automation, keys 1/2/3 switch tabs):

• Kanban: boards in their configured column order with result, attempt and retry state; start a board or stop its dispatcher.
• Goals: progress, loop status and verdicts; start, pause, resume, stop; set a new goal for a session.
• Cron: schedules in plain words with next/last run; run now, pause/resume, stop the exact active run, recent runs, create and edit (cron syntax or "every 15m", "weekdays at 09:30", with the next three run times shown).

Every action previews against the current revision and is refused if the item changed. Prompts and objectives are write-only in the browser. An unknown outcome is never retried automatically.

Blueprints (/blueprints) shows the catalog with validate and preview; activation requires retyping the fresh digest.

Knowledge

• Skills (/skills): installed skills with source and trust level, and the Hermes catalog with install.
• Memory (/memory): search bounded, redacted summaries with provenance; delete requires the exact digest.
• Learning (/learning): newest-first learning events grouped by UTC day, filtered by local profile ID and kind. Uses the same bounded/redacted current-state timeline as lemon learning. Memory/Skills links lead to existing management; this page never mutates data.
• MCP (/mcp): configured servers with connection status and tools.
• Nodes (/nodes): paired execution nodes and pending pairing requests.

Runtime and settings

• Models (/models): model catalog with context window, output limit and price; set the default model (preview then apply). Providers shows whether each provider has a usable credential (add them with lemon setup provider); Routing edits fallbacks and credential pools with previews, and typed confirmation for destructive changes. Credential references are entered in password fields and never stored in the page.
• Usage (/usage): spend and tokens for today, 7 and 30 days (UTC), by model, provider and top sessions. Usage is recorded when a run finishes.
• Diagnostics (/diagnostics): health, versions, capacity, channels, setup readiness, the same read-only checks as lemon doctor, and the last 200 log lines with secrets and paths hidden. Use lemon doctor --bundle for a support bundle. Chat model-list and compaction failures suggest retrying or checking this page; service error details stay out of the chat message.
• Settings (/settings): theme, notifications, default model and thinking level for new sessions (written to [defaults] in config.toml), the shortcut reference and the operator section. Theme and notification choices are stored in this browser only.

Remote access

A source checkout (./bin/lemon start|daemon) binds Lemon Web to 127.0.0.1. A packaged release configures its endpoint on all interfaces (config/runtime.exs), so restrict the port with a firewall or bind it behind a reverse proxy unless you intend LAN access. Set LEMON_WEB_HOST, LEMON_WEB_URL_SCHEME and LEMON_WEB_URL_PORT for the public URL (defaults localhost, https, 443). Terminate TLS in front of Lemon (the session cookie is marked Secure on HTTPS requests) and keep the operator token private. Never enable tokenless loopback compatibility behind a reverse proxy.

Recovery

Symptom	What to do
Login says no operator token is configured	Start Lemon through lemon web/lemon daemon (managed token) or set LEMON_CONTROL_PLANE_OPERATOR_TOKEN, then restart.
Token not accepted	Use the token of this runtime; rerun lemon web to sign in automatically.
"Too many attempts"	Wait a minute before trying again.
Setup needed	Run lemon setup, then choose Check again.
Web UI does not become healthy	Run lemon status, inspect the launcher log, then lemon doctor.
Port 4080 is occupied	Set LEMON_WEB_PORT and rerun lemon web.
A preview became stale	Review the refreshed state and preview again; nothing was changed.
Active-run choices disappeared	The run finished; send the preserved draft as a new message.

The UI ships its CSS, JavaScript and syntax highlighter inside the release and needs no CDN. It includes a skip link, labeled controls, visible focus, keyboard access to every action, live regions for streaming status, and responsive layouts down to phone width.