feature:chat

Screen States

ChatScreenState enum: LANDING | LOADING | ACTIVE

Landing: no conversation selected, shows greeting + model icon + optional conversation starters
Loading: spinner while fetching messages for a conversation
Active: message list + streaming content + input area

CHAT_GRAPH_ROUTE with NEW_CHAT_ROUTE (landing) and CHAT_ROUTE ("chat/{conversationId}")
PROMPTS_LIBRARY_ROUTE is co-located here for prompts library screen
When a new conversation starts from the landing page, pendingNavigationConversationId triggers navigation to chat/{id} after the first stream completes (data persisted to Room), keeping new_chat in the back stack
navigateToChat() replaces the current chat entry when switching between chats so back returns to new_chat

Messages stored flat, linked by parentMessageId (root = NO_PARENT UUID)
MessageTree.kt builds tree via buildActiveMessagePath(messages, activeBranches)
activeBranches: Map<String, Int> tracks which sibling is displayed per parent
switchBranch(parentMessageId, siblingIndex) updates branch selection and rebuilds display list
Editing a user message creates a new sibling (new branch); regenerating an AI message also creates a sibling

ContentPartRenderer dispatches by ContentPart.type:
- text -> MarkdownContent (custom regex parser with LaTeX support)
- think -> collapsible thinking block
- tool_call -> StreamingToolCallCard (expandable, shows args/output)
- image_file / image_url -> inline AsyncImage, tap opens FullscreenImageViewer
- error -> red-styled error display
CodeBlock renders fenced code with syntax highlighting, language badge, and copy button (3s checkmark)
LaTeX: LatexBlock (block math) and LatexInline (inline math) via AndroidMath native rendering
- Supports $$...$$, \[...\] (block) and $...$ , $...$ (inline)
- $...$ requires heuristic check (looksLikeLatex()) to avoid false positives on dollar amounts
- Falls back to monospace text if AndroidMath can't parse the expression

ChatViewModel.sendMessage() calls ChatRepository.startChat() which returns Flow<StreamEvent>
Two-phase: POST /api/agents/chat -> streamId, then GET SSE stream
streamingBuffer: StringBuilder accumulates text deltas
Tool calls tracked in activeToolCalls list (start -> complete lifecycle)
stopGeneration() cancels stream job and calls chatRepository.abortChat()
onPause()/onResume() handle app backgrounding: checks stream status, resumes if still active

Component	Purpose
`ChatInput`	Auto-growing text field, send/stop button, file attach, voice
`MessageBubble`	Icon + content column + action bar + sibling nav
`MessageList`	LazyColumn of MessageBubbles with scroll-to-bottom FAB
`ModelSelectorSheet`	Bottom sheet: search + endpoint-grouped model list
`ModelSelectorButton`	Header chip showing current model
`SiblingNavigator`	"1/3" with chevrons for branch switching
`LandingContent`	Greeting, entity icon, conversation starters
`StreamingIndicator`	Blinking cursor during active generation
`PresetPicker`	Preset selection menu
`SavePresetDialog`	Dialog to name and save current config as preset

PromptsLibraryScreen and PromptDetailScreen live in chat/prompts/
PromptsViewModel loads prompt groups from PromptRepository
handlePromptMention() on ChatViewModel inserts prompt command text at @ position

ChatInputToolbar renders toggles for enabled tools (web search, code interpreter, file search)
Tool state tracked as Set<String> in ChatUiState.enabledTools
ToolsDropdownMenu provides overflow for additional tool options
Toolbar wired into ChatInput above the text field

ImageGenCard renders DALL-E / image generation results (spinner while generating, AsyncImage when done)
LogContentCard renders expandable log output blocks with monospace text
Both dispatched from ContentPartRenderer — tool calls with name containing dall route to ImageGenCard

ArtifactDetector parses remark-directive format :::artifact{identifier="id" type="..." title="..."} with backtick-fenced content; groupArtifactVersions() groups by identifier
Supported types: text/html, image/svg+xml, application/vnd.react, application/vnd.mermaid, text/markdown/text/md, text/plain, application/vnd.code-html
MermaidWebContent renders Mermaid diagrams via CDN mermaid.js with zoom controls and dark theme
MarkdownWebContent renders Markdown via CDN marked.js + highlight.js with GFM and syntax highlighting
HTML/React/SVG templates include Tailwind CDN, theme CSS vars, and error handling
React template preprocesses import/export statements for browser-compatible execution
ArtifactPanel supports fullscreen Dialog mode, version switching, loading indicator, and WebView error overlay
ArtifactButton shows type-specific icons and subtitle (e.g. "Mermaid Diagram", "React Component")
ContentPartRenderer wires groupArtifactVersions() to pass version lists to ArtifactButton/ArtifactPanel
ArtifactVersionNav provides prev/next arrows with "v2/3" indicator
ArtifactDownloadHelper shares artifacts via FileProvider temp file + system share sheet. Maps 25+ language extensions including .mmd for Mermaid. Sanitizes filenames to 100 chars
Gotcha: FileProvider authority must match app's declared authority in AndroidManifest

VideoContentPlayer uses ExoPlayer (media3) — 16:9 aspect ratio Card, lifecycle-aware release
AudioContentPlayer uses MediaPlayer — play/pause + seekbar, 250ms polling for progress
AudioContentPlayerFromBytes variant writes bytes to temp file for MediaPlayer
Gotcha: Both players must release resources on dispose — use DisposableEffect

Thumbs-down opens FeedbackCommentDialog before submitting; thumbs-up fires immediately
Comment is optional — empty string is a valid submission
Toggling off an existing thumbs-down (already selected) calls onFeedback(null) directly, skipping the dialog

MessageTimestamp shows relative/absolute time, toggled on tap
Parses multiple ISO 8601 format variants; falls back gracefully on invalid input
Integrated into MessageBubble action row