Status: the macOS/iOS SwiftUI chat UI talks directly to the Gateway WebSocket. No embedded browser, no local static server.

What it is

• A native chat UI for the gateway.
• Uses the same sessions and routing rules as other channels.
• Deterministic routing: replies always go back to WebChat.
• History is always fetched from the gateway (no local file watching). If the gateway is unreachable, WebChat is read-only.

Quick start

1. Start the gateway.
2. Open the WebChat UI (macOS/iOS app) or the Control UI chat tab.
3. Ensure a valid gateway auth path is configured (shared-secret by default, even on loopback). See Auth basics (local vs remote).

How it works

• The UI connects to the Gateway WebSocket and uses the chat.history, chat.send, chat.inject, and chat.message.get RPC methods.
• Control UI opens a chat with a small recent-history page through chat.startup. Short chat links resolve their session in that same request. Short-reference startup also subscribes the connection to authorized session events before reading history, so updates arriving before the chat pane mounts are not missed. Scroll upward to load older messages. A restored Home pane waits for the selected chat to finish loading, while explicitly opening Home loads it immediately.
• chat.history is bounded for stability: Gateway may truncate long text fields, omit heavy metadata, and replace oversized entries with [chat.history omitted: message too large]. History pages skip hidden and tool-only transcript entries while filling the requested visible-message window from the existing indexed transcript. A byte-full window can finish before the requested message count, with older content available through pagination. API clients can send a per-request maxChars to override the default limit for one call.
• Paginated chat.history and chat.startup requests accept a maxBytes page target, defaulting to 512 KiB with a 6 MiB hard ceiling for messages and their activity. The Control UI keeps the initial tail small, then requests up to 1,000 older messages and follows nextOffset to continue. One readable message or a group projected from one transcript row can exceed the target so pagination does not hide its content; groups that exceed the hard ceiling remain bounded. Anchored messageId reads keep their existing default budget because they have no continuation. Bound Claude CLI transcripts use the same page budget and back-scroll pagination, including messages that exist only in the native transcript.
• If history changes during a page read, the Gateway returns a coherent page from the current history. A windowReset: true response contains a replacement tail; clients replace their loaded history and continue with its deltaCursor and pagination fields. A stale delta cursor returns { kind: "reset" }, prompting a fresh tail request. Reads racing a projection rebuild wait briefly before returning a retryable rebuilding error.
• When a visible assistant message was truncated in chat.history, the Control UI automatically fetches the full display-normalized entry through chat.message.get. That fetch does not increase the default history payload. The preview remains visible while it loads. Recovered content replaces it inline. chat.message.get uses the same transcript branch and display rules as chat.history. Unlike chat.history, it targets one entry by messageId. It returns an honest unavailable reason when the full content can no longer be returned.
• chat.history follows the active transcript branch for append-only session files, so abandoned rewrite branches and superseded prompt copies are not rendered in WebChat.
• Compaction entries render as a history divider showing the context reduction when token measurements are available. Ordinary conversation history and Fork remain available; compaction does not create a separate checkpoint browsing or restoration surface.
• Control UI remembers the backing Gateway sessionId returned by chat.history. It includes that id on follow-up chat.send calls. Reconnects and page refreshes therefore continue the same stored conversation, unless the user starts or resets a session.
• Foreground sends also include the displayed branch's leaf from the rendered history as expectedLeafEntryId. If another client switched branches first, Control UI parks the message for review and refreshes the transcript instead of posting it to the new branch. Reconnect and restored-outbox replays intentionally omit this precondition after reconciling current history.
• When you change a chat setting and immediately send, Control UI shows Applying chat settings until that change and its session refresh finish. Later background session refreshes do not extend this wait. Opening a pane without changing a setting does not create a settings wait.
• chat.send takes an idempotency key (Control UI uses the run id). The Gateway dedupes repeated requests that reuse the same key. Retried or duplicate in-flight submits do not create a second run when the session, message, attachments, and mention selections match. Reusing that key with different mention selections is rejected.
• Queued messages keep their original send identity even when execution starts under a different run id. Clients reconcile the local pending message with its saved transcript entry by that send identity, so completion and history reload show one copy.
• During reconnect, an attempted message whose delivery is uncertain stays in the transcript with a Waiting for reconnect status. Messages that have not been attempted stay in the composer queue. Messages the Gateway has queued for a later turn also appear above the composer until consumed or canceled, without a duplicate transcript bubble or another send. Their remove action cancels the exact queued message on the Gateway. Once removal is confirmed, that prompt and its attachments disappear from the queue and conversation, including after reconnect or reload. Stop, timeout, and unsuccessful-send cancellations keep their recovery messages visible. Reordering applies only to messages still owned by the browser. Discard on an uncertain local message removes only its browser copy; it does not cancel a message the Gateway already received.
• Replying to a specific message (right-click → Reply) sends the target's transcript id as replyToId on chat.send. For sources with visible text, the Gateway resolves that message from session history. It hydrates the same channel-agnostic reply context metadata Discord replies use. Agents see has_reply_context plus the untrusted "Reply target of current user message" block with sender label and body. Webchat prompts keep volatile conversation ids such as reply_to_id suppressed, per the existing byte-stable prompt policy for direct webchat sessions. Reply targets without a persisted transcript id (for example pending sends) fall back to an inline quote in the message body.
• History pages include bounded quoted-reply previews, so displaying references does not fetch each original separately. chat.message.get reads the selected indexed row, with preceding-row context only when needed to hide an old announce pair. Explicit full-message reads are cached across reconnects within the same session lifecycle; reset or replacement invalidates them.
• Attachment-only messages keep their Reply action. The preview uses filenames or image labels, and replyToId still points to the original entry. Replying does not attach the source files to the new message.
• Workspace startup files and pending BOOTSTRAP.md instructions are supplied through the agent system prompt's # Project Context section, not copied into the WebChat user message. If bootstrap content is truncated, the system prompt gets a short "Bootstrap Context Notice" instead. Detailed counts and config knobs stay on diagnostic surfaces.
• Display normalization on chat.history strips: runtime-only Apus context, inbound envelope wrappers, inline delivery directive tags such as [[reply_to_current]], [[reply_to:<id>]], and [[audio_as_voice]], plain-text tool-call XML payloads (<tool_call>, <function_call>, <tool_calls>, <function_calls>, including truncated blocks), and leaked ASCII/full-width model control tokens. Removing model control tokens preserves punctuation and Markdown formatting, keeps adjacent words separated, and leaves code examples intact. Assistant entries whose whole visible text is only the silent token NO_REPLY (case-insensitive) are omitted.
• When a reply attachment cannot be read or prepared, WebChat preserves any deliverable attachments. It shows one short failure warning without exposing local filesystem paths.
• In Control UI chat and new-session composers, oversized static PNG uploads are resized in a browser worker before sending, keeping image decoding and encoding off the composer’s main thread. This applies to drag-and-drop, the file picker, and image paste. Images already within the Gateway-advertised limit stay unchanged; resized images keep their aspect ratio and PNG transparency. Browser resizing is limited to 25 megapixels of source data. Animated PNGs are not flattened, and other file types retain their size limits. If an image cannot be decoded or resized, its attachment shows a read failure instead of sending oversized bytes.
• In the Control UI, assistant images and attachments appear in message order, between their surrounding paragraphs. Before/after labels stay beside the corresponding images.
• Attachment directives owned by the current WebChat reply stay hidden in live transcript events while files are prepared. User prompts, fenced examples, and references outside that reply's attachment pipeline remain unchanged.
• WebChat excludes reasoning-flagged reply payloads (isReasoning: true) from assistant content, transcript replay text, and audio content blocks. Thinking-only payloads therefore do not surface as visible assistant messages or playable audio.
• chat.inject appends an assistant note directly to the transcript and broadcasts it to the UI (no agent run). The Control UI reconciles each note by transcript identity, so identical notes remain separate and do not become run activity or duplicate after a history reload.
• Aborted runs can keep partial assistant output visible in the UI. Gateway persists that partial text into transcript history when buffered output exists, and marks the entry with abort metadata.

Transcript and delivery model

Admission and transcript persistence are separate. A chat.send, sessions.send, or initial sessions.create acknowledgment can arrive while approved input waits in durable pending-input custody, including during workspace preparation. Skill-library selection and authoring preparation run after that acknowledgment, under the admitted run's cancellation and error handling, alongside workspace and reply startup. Preparation failures appear as run errors. The Gateway reserves the existing reply-admission ticket before acknowledging, so a later send cannot overtake a message whose preparation is still pending. An optional messageSeq comes only from a committed transcript receipt. Clients must not predict it from history length or treat status: "started" as persistence. The Control UI replaces its provisional source with accepted custody, then with the canonical row. Accepted inputs stay below saved conversation history until they are committed to the transcript. Its renderer keeps a loaded local preview in the same image element during this handoff while canonical media metadata and image bytes load. Authoritative text, media replacements, and removals still win. Unavailable or access-denied media shows a visible reason. Once custody, a consumption record, or a committed user-message receipt retires a local source, replayed terminal events cannot bring it back, even when its row is absent from a later history page. Submission identity stays separate from the execution run, so two intentionally identical sends remain two inputs.

WebChat has two separate data paths:

• The SQLite transcript rows are the durable model/runtime transcript. For normal agent runs, the embedded Apus runtime persists model-visible user, assistant, and toolResult messages through the session accessor. WebChat does not write arbitrary delivery, status, or helper text into that transcript.
• Gateway ReplyPayload events are the live delivery projection: normalized for WebChat/channel display, block streaming, directive tags, media embedding, TTS/audio flags, and UI fallback behavior. They are not themselves the canonical session log.
• Harnesses that require visible replies through tools.message still use WebChat as a current-run internal source reply sink. A targetless message.send from that active WebChat run is projected into the same chat and mirrored to the session transcript. WebChat does not become a reusable outbound channel and never inherits lastChannel.
• WebChat injects assistant transcript entries only when the Gateway owns a displayed message outside a normal embedded agent turn. Those cases are chat.inject, non-agent command replies, aborted partial output, and WebChat-managed media transcript supplements.
• If live assistant text appears during a run but disappears after history reload, check three things in order. First, whether the SQLite transcript contains the assistant text. Second, whether the chat.history display projection stripped it. Third, whether the Control UI optimistic-tail merge replaced local delivery state with the persisted snapshot.

Normal agent-run final answers should be durable because the embedded runtime writes the assistant message_end. Any fallback that mirrors a delivered final payload into the transcript must first avoid duplicating an assistant turn that the embedded runtime already wrote.

Human mention delivery

The Control UI binds each selected person to the submitted message text. chat.send, the initial message on sessions.create, and sessions.send accept an optional mentions array of { profileId, start, end } annotations. There are at most ten annotations. start is inclusive and end is exclusive, measured in UTF-16 code units. The Gateway validates their text ranges and recipients before accepting the input. Plain @name text and agent output do not create human mentions. Copying or quoting text does not copy its recipient selections.

The mention becomes eligible for an Inbox entry and optional browser push only after the original human message is newly committed to the transcript. An early status: "started" acknowledgment, a staged initial message, or durable pending-input custody is not that commit. A queued or remotely placed first message therefore does not notify while it is still waiting to be recorded. A later agent failure does not undo a mention whose human message was already committed.

Transport retries preserve the exact submitted text, mention annotations, and original send identity, even when execution gets a different run id. Replaying that committed input does not create another mention or restore a dismissed entry. An intentional new send has a new identity and may notify again, even when its text is identical. Transcript loading, hidden continuations, and attachment enrichment are not new human sends.

The supporting RPCs require operator.read and use the authenticated profile, never a caller-selected Inbox owner:

Delivery is best-effort. The Inbox and replay bookkeeping survive Gateway restarts within their retention limits. Capacity limits can still skip alerts. Restarting or reconnecting does not resend old browser notifications or restore dismissed entries. Notification failures do not retry or undo the posted chat message. Browser push does not provide exactly-once delivery. See Inbox retention and notification preferences.

Control UI agents tools panel

• The Control UI /agents Tools panel has a "Tool preview" backed by tools.effective(sessionKey=...). It previews core, plugin, channel-owned, and already-discovered MCP server tools using the session's saved settings. It does not report the exact tools of an active run.
• A separate config-editing view (backed by tools.catalog) covers profiles, per-agent overrides, and catalog semantics.
• The preview is session-scoped. Switching sessions on the same agent can change it, and resetting a session refreshes it. Unsaved config edits are not reflected in the preview, and saved or runtime changes may take time to appear. Run-specific tools can become available when a run starts; a tool missing from the preview is not necessarily disabled. The run still applies its current policy, credentials, and execution checks.
• The panel shows a notice when configured MCP servers have not been connected or changed since the last discovery. It does not silently start MCP transports from the read path. Loading and failed previews do not mean the session has zero tools.
• The config editor does not imply runtime availability. Effective access still follows policy precedence (allow/deny, per-agent and provider/channel overrides).

Remote use

• Remote mode tunnels the gateway WebSocket over SSH/Tailscale.
• You do not need to run a separate WebChat server.

Configuration reference (WebChat)

Full configuration: Configuration

WebChat has no persisted config section. Gateway uses the built-in chat.history display limit. API clients can send per-request maxChars to override it for a single call. Clients that can expand tool output with chat.message.get may also send toolResultMaxChars to request shorter tool-result text previews without reducing user or assistant text. Complete JSON objects and arrays that fit the existing display limit retain that limit because clients use them for source cards and embedded views. This optional limit applies to chat.history and chat.startup, including history pages and delta catch-up; omit it to retain the default behavior. Repeat it on each page request. Legacy channels.webchat and gateway.webchat config is retired. Run apus doctor --fix to remove it.

Related global options:

• gateway.port, gateway.bind: WebSocket host/port.
• gateway.auth.mode, gateway.auth.token, gateway.auth.password: shared-secret WebSocket auth.
• gateway.auth.allowTailscale: browser Control UI chat tab can use Tailscale Serve identity headers when enabled.
• gateway.auth.mode: "trusted-proxy": reverse-proxy auth for browser clients behind an identity-aware non-loopback proxy source (see Trusted Proxy Auth).
• gateway.remote.url, gateway.remote.token, gateway.remote.password: remote gateway target.
• session.*: session routing and storage.

Related

• Control UI
• Dashboard