async function streamChatResponse(messages, chatContainer, agentType, tabId) {
    const currentSettings = getSettings();
    const backendEndpoint = '/api';

    // Resolve model configuration for this agent type
    let modelConfig = resolveModelConfig(agentType);
    if (!modelConfig) {
        modelConfig = getDefaultModelConfig();
    }

    if (!modelConfig) {
        // No models configured - show error
        const errorDiv = document.createElement('div');
        errorDiv.className = 'message assistant error';
        errorDiv.innerHTML = `<div class="message-content">No models configured. Please open Settings and add a provider and model.</div>`;
        chatContainer.appendChild(errorDiv);
        return;
    }

    // Resolve research sub-agent model if configured
    let researchSubAgentConfig = null;
    if (currentSettings.researchSubAgentModel) {
        const subAgentModel = currentSettings.models?.[currentSettings.researchSubAgentModel];
        if (subAgentModel) {
            const subAgentProvider = currentSettings.providers?.[subAgentModel.providerId];
            if (subAgentProvider) {
                researchSubAgentConfig = {
                    endpoint: subAgentProvider.endpoint,
                    token: subAgentProvider.token,
                    model: subAgentModel.modelId
                };
            }
        }
    }

    // Resolve image model selections to HF model ID strings
    const imageGenModelId = currentSettings.imageGenModel
        ? currentSettings.models?.[currentSettings.imageGenModel]?.modelId || null
        : null;
    const imageEditModelId = currentSettings.imageEditModel
        ? currentSettings.models?.[currentSettings.imageEditModel]?.modelId || null
        : null;

    // Set up AbortController for this request
    const abortController = new AbortController();
    if (tabId !== undefined) {
        activeAbortControllers[tabId] = abortController;
    }

    try {
        // Determine parent agent ID for abort propagation
        const parentAgentId = timelineData[tabId]?.parentTabId != null
            ? timelineData[tabId].parentTabId.toString()
            : null;

        const response = await apiFetch(`${backendEndpoint}/chat/stream`, {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            signal: abortController.signal,
            body: JSON.stringify({
                messages: messages,
                agent_type: agentType,
                stream: true,
                endpoint: modelConfig.endpoint,
                token: modelConfig.token || null,
                model: modelConfig.model,
                extra_params: modelConfig.extraParams || null,
                multimodal: modelConfig.multimodal || false,
                e2b_key: currentSettings.e2bKey || null,
                serper_key: currentSettings.serperKey || null,
                hf_token: currentSettings.hfToken || null,
                image_gen_model: imageGenModelId,
                image_edit_model: imageEditModelId,
                research_sub_agent_model: researchSubAgentConfig?.model || null,
                research_sub_agent_endpoint: researchSubAgentConfig?.endpoint || null,
                research_sub_agent_token: researchSubAgentConfig?.token || null,
                research_sub_agent_extra_params: researchSubAgentConfig?.extraParams || null,
                research_parallel_workers: currentSettings.researchParallelWorkers || null,
                research_max_websites: currentSettings.researchMaxWebsites || null,
                agent_id: tabId.toString(),  // Send unique tab ID for sandbox sessions
                parent_agent_id: parentAgentId,  // Parent agent ID for abort propagation
                frontend_context: getFrontendContext()  // Dynamic context for system prompts
            })
        });

        if (!response.ok) {
            throw new Error(`HTTP error! status: ${response.status}`);
        }

        const reader = response.body.getReader();
        const decoder = new TextDecoder();
        let buffer = '';
        let fullResponse = '';
        let currentMessageEl = null;
        let progressHidden = false;

        // Flush any accumulated assistant text to the timeline
        // Call before adding tool/code/report timeline events to preserve ordering
        function flushResponseToTimeline() {
            if (fullResponse && tabId !== undefined) {
                const evIdx = addTimelineEvent(tabId, 'assistant', fullResponse);
                if (currentMessageEl) currentMessageEl.dataset.timelineIndex = evIdx;
                fullResponse = '';
            }
        }

        while (true) {
            const { done, value } = await reader.read();
            if (done) break;

            buffer += decoder.decode(value, { stream: true });
            const lines = buffer.split('\n');
            buffer = lines.pop() || '';

            for (const line of lines) {
                if (line.startsWith('data: ')) {
                    const data = JSON.parse(line.slice(6));

                    // Hide progress widget on first meaningful response
                    if (!progressHidden && data.type !== 'generating' && data.type !== 'retry' && !data.type.startsWith('debug_')) {
                        hideProgressWidget(chatContainer);
                        progressHidden = true;
                    }

                    // Handle different message types from backend
                    if (data.type === 'thinking') {
                        // Assistant thinking - create message if not exists
                        if (!currentMessageEl) {
                            currentMessageEl = createAssistantMessage(chatContainer);
                        }
                        fullResponse += data.content;
                        appendToMessage(currentMessageEl, resolveGlobalFigureRefs(parseMarkdown(fullResponse)));
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'code') {
                        // Code execution result - update the last code cell
                        updateLastCodeCell(chatContainer, data.output, data.error, data.images);
                        currentMessageEl = null;  // Reset for next thinking
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'code_start') {
                        // Code cell starting execution - show with spinner
                        flushResponseToTimeline();
                        createCodeCell(chatContainer, data.code, null, false, true);
                        currentMessageEl = null;
                        scrollChatToBottom(chatContainer);
                        // Add to timeline - show code snippet preview
                        const codePreview = data.code ? data.code.split('\n')[0] : 'code execution';
                        const codeEvIdx = addTimelineEvent(tabId, 'assistant', codePreview, null, { tag: 'CODE' });
                        chatContainer.lastElementChild.dataset.timelineIndex = codeEvIdx;

                    } else if (data.type === 'upload') {
                        // File upload notification
                        flushResponseToTimeline();
                        createUploadMessage(chatContainer, data.paths, data.output);
                        currentMessageEl = null;
                        scrollChatToBottom(chatContainer);
                        // Add to timeline
                        const upEvIdx = addTimelineEvent(tabId, 'assistant', data.paths?.join(', ') || 'files', null, { tag: 'UPLOAD' });
                        chatContainer.lastElementChild.dataset.timelineIndex = upEvIdx;

                    } else if (data.type === 'download') {
                        // File download notification
                        flushResponseToTimeline();
                        createDownloadMessage(chatContainer, data.paths, data.output);
                        currentMessageEl = null;
                        scrollChatToBottom(chatContainer);
                        // Add to timeline
                        const dlEvIdx = addTimelineEvent(tabId, 'assistant', data.paths?.join(', ') || 'files', null, { tag: 'DOWNLOAD' });
                        chatContainer.lastElementChild.dataset.timelineIndex = dlEvIdx;

                    } else if (data.type === 'generating') {
                        // Still generating - no action needed

                    } else if (data.type === 'result') {
                        // References are globally namespaced by the backend (e.g., figure_T3_1)
                        const resultText = data.content || '';

                        // Populate global registry
                        if (data.figures) {
                            for (const [name, figData] of Object.entries(data.figures)) {
                                if (new RegExp(`</?${name}>`, 'i').test(resultText)) {
                                    globalFigureRegistry[name] = figData;
                                }
                            }
                        }

                        // Agent result - update command center widget
                        updateActionWidgetWithResult(tabId, resultText, data.figures || {});

                    } else if (data.type === 'result_preview') {
                        // Show result preview
                        flushResponseToTimeline();
                        // Replace <figure_x> tags with placeholders BEFORE markdown processing
                        let previewContent = data.content;
                        const figurePlaceholders = {};

                        if (data.figures) {
                            for (const [figureName, figureData] of Object.entries(data.figures)) {
                                // Use %%% delimiters to avoid markdown interpretation
                                const placeholderId = `%%%FIGURE_${figureName}%%%`;
                                figurePlaceholders[placeholderId] = figureData;

                                // Handle both <figure_x> self-closing and <figure_x></figure_x> pairs
                                // First replace paired tags, preserving them as block elements
                                const pairedTag = new RegExp(`<${figureName}></${figureName}>`, 'gi');
                                previewContent = previewContent.replace(pairedTag, `\n\n${placeholderId}\n\n`);

                                // Then replace remaining self-closing tags or orphaned closing tags
                                const singleTag = new RegExp(`</?${figureName}>`, 'gi');
                                previewContent = previewContent.replace(singleTag, `\n\n${placeholderId}\n\n`);
                            }
                        }

                        // Process markdown
                        let html = parseMarkdown(previewContent);

                        // Replace placeholders with actual images AFTER markdown processing
                        for (const [placeholderId, figureData] of Object.entries(figurePlaceholders)) {
                            let imageHtml = '';
                            if (figureData.type === 'png' || figureData.type === 'jpeg') {
                                imageHtml = `<img src="data:image/${figureData.type};base64,${figureData.data}" style="max-width: 400px; max-height: 400px; height: auto; border-radius: 4px; margin: 12px 0; display: block;" onclick="openImageModal(this.src)">`;
                            } else if (figureData.type === 'svg') {
                                imageHtml = `<div style="margin: 12px 0;">${atob(figureData.data)}</div>`;
                            }
                            // Replace both the placeholder and any paragraph-wrapped version
                            html = html.replace(new RegExp(`<p>${placeholderId}</p>`, 'g'), imageHtml);
                            html = html.replace(new RegExp(placeholderId, 'g'), imageHtml);
                        }

                        // Store raw result as hidden assistant message for history reconstruction
                        const resultMsg = document.createElement('div');
                        resultMsg.className = 'message assistant';
                        resultMsg.style.display = 'none';
                        resultMsg.innerHTML = `<div class="message-content">${escapeHtml(data.content)}</div>`;
                        chatContainer.appendChild(resultMsg);

                        // Create result block
                        const resultDiv = document.createElement('div');
                        resultDiv.className = 'agent-result';
                        resultDiv.innerHTML = `
                            <div class="result-header">Result</div>
                            <div class="result-content">${html}</div>
                        `;
                        chatContainer.appendChild(resultDiv);
                        scrollChatToBottom(chatContainer);
                        // Add result dot to parent research timeline
                        const figCount = data.figures ? Object.keys(data.figures).length : 0;
                        const reportDesc = figCount > 0 ? `${figCount} figures` : (data.content?.replace(/<[^>]+>/g, '').trim().substring(0, 60) || 'done');
                        const resEvIdx = addTimelineEvent(tabId, 'assistant', reportDesc, null, { tag: 'RESULT' });
                        resultDiv.dataset.timelineIndex = resEvIdx;

                    } else if (data.type === 'status') {
                        // Research status update
                        createStatusMessage(chatContainer, data.message, data.iteration, data.total_iterations);
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'queries') {
                        // Research queries generated
                        createQueriesMessage(chatContainer, data.queries, data.iteration);
                        scrollChatToBottom(chatContainer);
                        // Register each query as a virtual sub-agent in the timeline
                        const startIdx = Object.keys(researchQueryTabIds).length;
                        for (let qi = 0; qi < data.queries.length; qi++) {
                            const globalIdx = startIdx + qi;
                            const virtualId = `research-${tabId}-q${globalIdx}`;
                            researchQueryTabIds[globalIdx] = virtualId;
                            registerAgentInTimeline(virtualId, 'search', data.queries[qi], tabId);
                            setTimelineGenerating(virtualId, true);
                        }

                    } else if (data.type === 'progress') {
                        // Research progress
                        updateProgress(chatContainer, data.message, data.websites_visited, data.max_websites);
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'source') {
                        // Research source found - now includes query grouping
                        createSourceMessage(chatContainer, data);
                        scrollChatToBottom(chatContainer);
                        // Add source as dot in virtual sub-agent timeline
                        const sourceVirtualId = researchQueryTabIds[data.query_index];
                        if (sourceVirtualId) {
                            addTimelineEvent(sourceVirtualId, 'assistant', data.title || data.url || 'source');
                        } else if (data.query_index === -1) {
                            // Browse result — create a virtual browse entry if needed
                            const browseId = `research-${tabId}-browse-${Date.now()}`;
                            registerAgentInTimeline(browseId, 'browse', data.url || 'webpage', tabId);
                            addTimelineEvent(browseId, 'assistant', data.title || data.url || 'page');
                            setTimelineGenerating(browseId, false);
                        }

                    } else if (data.type === 'query_stats') {
                        // Update query statistics
                        updateQueryStats(data.query_index, {
                            relevant: data.relevant_count,
                            irrelevant: data.irrelevant_count,
                            error: data.error_count
                        });
                        // Mark search sub-agent as done
                        const statsVirtualId = researchQueryTabIds[data.query_index];
                        if (statsVirtualId) {
                            setTimelineGenerating(statsVirtualId, false);
                        }

                    } else if (data.type === 'assessment') {
                        // Research completeness assessment
                        createAssessmentMessage(chatContainer, data.sufficient, data.missing_aspects, data.findings_count, data.reasoning);
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'report') {
                        // Final research report
                        flushResponseToTimeline();
                        createReportMessage(chatContainer, data.content, data.sources_count, data.websites_visited);
                        scrollChatToBottom(chatContainer);
                        // Add to timeline
                        const rptEvIdx = addTimelineEvent(tabId, 'assistant', `${data.sources_count || 0} sources, ${data.websites_visited || 0} sites`, null, { tag: 'RESULT' });
                        chatContainer.lastElementChild.dataset.timelineIndex = rptEvIdx;

                    } else if (data.type === 'tool_start') {
                        // Agent tool execution starting — create a tool-cell box (like code cells)
                        flushResponseToTimeline();
                        currentMessageEl = null;

                        const toolLabels = {
                            'web_search': 'SEARCH',
                            'read_url': 'READ',
                            'screenshot_url': 'SCREENSHOT',
                            'generate_image': 'GENERATE',
                            'edit_image': 'EDIT',
                            'read_image_url': 'LOAD IMAGE',
                            'read_image': 'LOAD IMAGE',
                            'save_image': 'SAVE IMAGE',
                            'show_html': 'HTML'
                        };
                        const toolDescriptions = {
                            'web_search': data.args?.query || '',
                            'read_url': data.args?.url || '',
                            'screenshot_url': data.args?.url || '',
                            'generate_image': data.args?.prompt || '',
                            'edit_image': `${data.args?.prompt || ''} (from ${data.args?.source || ''})`,
                            'read_image_url': data.args?.url || '',
                            'read_image': data.args?.source || '',
                            'save_image': `${data.args?.source || ''} → ${data.args?.filename || ''}`,
                            'show_html': data.args?.source?.substring(0, 80) || ''
                        };
                        const label = toolLabels[data.tool] || data.tool.toUpperCase();
                        const description = toolDescriptions[data.tool] || '';

                        // Store tool call in DOM for history reconstruction
                        // Reuse currentMessageEl (from thinking) if it exists, like launch events do
                        let toolCallMsg = currentMessageEl;
                        if (!toolCallMsg) {
                            toolCallMsg = document.createElement('div');
                            toolCallMsg.className = 'message assistant';
                            toolCallMsg.style.display = 'none';
                            chatContainer.appendChild(toolCallMsg);
                        }
                        toolCallMsg.setAttribute('data-tool-call', JSON.stringify({
                            tool_call_id: data.tool_call_id,
                            function_name: data.tool,
                            arguments: data.arguments,
                            thinking: data.thinking || ''
                        }));

                        // Create tool-cell box (similar to code-cell)
                        const toolCell = document.createElement('div');
                        toolCell.className = 'tool-cell';
                        if (document.getElementById('collapseToolsCheckbox')?.checked) {
                            toolCell.classList.add('collapsed');
                        }
                        toolCell.setAttribute('data-tool-name', data.tool);
                        const descHtml = description ? `<span class="tool-cell-desc">${escapeHtml(description)}</span>` : '';
                        toolCell.innerHTML = `
                            <div class="tool-cell-label"><div class="widget-collapse-toggle${document.getElementById('collapseToolsCheckbox')?.checked ? ' collapsed' : ''}"></div><span>${label}</span>${descHtml}${createSpinnerHtml()}</div>
                            <div class="tool-cell-input">${escapeHtml(description)}</div>
                        `;
                        setupCollapseToggle(toolCell, '.tool-cell-label');
                        chatContainer.appendChild(toolCell);
                        scrollChatToBottom(chatContainer);
                        const toolEvIdx = addTimelineEvent(tabId, 'assistant', description, null, { tag: label });
                        toolCell.dataset.timelineIndex = toolEvIdx;

                    } else if (data.type === 'tool_result') {
                        // Agent tool result — populate the last tool-cell with output
                        const lastToolCell = chatContainer.querySelector('.tool-cell:last-of-type');

                        // Remove spinner
                        if (lastToolCell) {
                            const spinner = lastToolCell.querySelector('.tool-spinner');
                            if (spinner) spinner.remove();
                        }

                        // Store tool response in DOM for history reconstruction
                        const toolResponseMsg = document.createElement('div');
                        toolResponseMsg.className = 'message tool';
                        toolResponseMsg.style.display = 'none';
                        toolResponseMsg.setAttribute('data-tool-response', JSON.stringify({
                            tool_call_id: data.tool_call_id,
                            content: data.response || ''
                        }));
                        chatContainer.appendChild(toolResponseMsg);

                        // Build output HTML based on tool type
                        let outputHtml = '';

                        if (data.tool === 'web_search' && data.result?.results) {
                            try {
                                const results = typeof data.result.results === 'string' ? JSON.parse(data.result.results) : data.result.results;
                                if (Array.isArray(results)) {
                                    outputHtml = '<div class="search-results-content">' +
                                        results.map(r =>
                                            `<div class="search-result-item"><a href="${escapeHtml(r.url)}" target="_blank">${escapeHtml(r.title)}</a><span class="search-snippet">${escapeHtml(r.snippet)}</span></div>`
                                        ).join('') + '</div>';
                                }
                            } catch(e) { /* ignore parse errors */ }
                        } else if (data.tool === 'read_url') {
                            const len = data.result?.length || 0;
                            const markdown = data.result?.markdown || '';
                            const summaryText = len > 0 ? `Extracted ${(len / 1000).toFixed(1)}k chars` : 'No content extracted';
                            if (markdown) {
                                const toggleId = `read-content-${Date.now()}-${Math.random().toString(36).slice(2, 7)}`;
                                outputHtml = `<div class="tool-cell-read-summary">${summaryText} <button class="read-content-toggle" onclick="const el=document.getElementById('${toggleId}');el.classList.toggle('expanded');this.textContent=el.classList.contains('expanded')?'Hide':'Show content'">Show content</button></div><div id="${toggleId}" class="read-content-body">${parseMarkdown(markdown)}</div>`;
                            } else {
                                outputHtml = `<div class="tool-cell-read-summary">${summaryText}</div>`;
                            }
                        } else if (data.tool === 'screenshot_url' && data.image) {
                            outputHtml = `<img src="data:image/png;base64,${data.image}" alt="Screenshot" class="screenshot-img" />`;
                        } else if ((data.tool === 'generate_image' || data.tool === 'edit_image' || data.tool === 'read_image_url' || data.tool === 'read_image') && data.image) {
                            const imgName = data.image_name || 'image';
                            outputHtml = `<img src="data:image/png;base64,${data.image}" alt="${escapeHtml(imgName)}" class="generated-img" />`;
                        } else if ((data.tool === 'generate_image' || data.tool === 'edit_image' || data.tool === 'read_image_url' || data.tool === 'read_image') && !data.image) {
                            const errMsg = data.response || 'Failed to process image';
                            outputHtml = `<div class="tool-cell-read-summary">${escapeHtml(errMsg)}</div>`;
                        } else if (data.tool === 'save_image' && data.image) {
                            const filename = data.result?.filename || '';
                            outputHtml = `<img src="data:image/png;base64,${data.image}" alt="${escapeHtml(filename)}" class="generated-img" /><div class="tool-cell-read-summary">Saved as ${escapeHtml(filename)}</div>`;
                        } else if (data.tool === 'save_image' && !data.image) {
                            const errMsg = data.response || 'Failed to save image';
                            outputHtml = `<div class="tool-cell-read-summary">${escapeHtml(errMsg)}</div>`;
                        } else if (data.tool === 'show_html' && data.result?.html) {
                            // Create iframe programmatically to avoid escaping issues with srcdoc
                            if (lastToolCell) {
                                const outputEl = document.createElement('div');
                                outputEl.className = 'tool-cell-output';
                                const iframe = document.createElement('iframe');
                                iframe.className = 'show-html-iframe';
                                iframe.sandbox = 'allow-scripts allow-same-origin';
                                iframe.srcdoc = data.result.html;
                                outputEl.appendChild(iframe);
                                lastToolCell.appendChild(outputEl);
                            }
                        } else if (data.tool === 'show_html' && !data.result?.html) {
                            const errMsg = data.response || 'Failed to load HTML';
                            outputHtml = `<div class="tool-cell-read-summary">${escapeHtml(errMsg)}</div>`;
                        }

                        if (outputHtml && lastToolCell) {
                            const outputEl = document.createElement('div');
                            outputEl.className = 'tool-cell-output';
                            outputEl.innerHTML = outputHtml;
                            lastToolCell.appendChild(outputEl);
                        }

                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'content') {
                        // Regular streaming content (non-code agents)
                        if (!currentMessageEl) {
                            currentMessageEl = createAssistantMessage(chatContainer);
                        }
                        fullResponse += data.content;
                        appendToMessage(currentMessageEl, resolveGlobalFigureRefs(parseMarkdown(fullResponse)));
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'launch') {
                        // Tool-based agent launch from command center
                        pendingAgentLaunches++;
                        const agentType = data.agent_type;
                        const initialMessage = data.initial_message;
                        const taskId = data.task_id;
                        const toolCallId = data.tool_call_id;

                        // Add tool call data to existing message (from thinking) or create new one
                        // This keeps content + tool_calls together for proper history reconstruction
                        let toolCallMsg = currentMessageEl;
                        if (!toolCallMsg) {
                            toolCallMsg = document.createElement('div');
                            toolCallMsg.className = 'message assistant';
                            toolCallMsg.innerHTML = '<div class="message-content"></div>';
                            chatContainer.appendChild(toolCallMsg);
                        }
                        toolCallMsg.setAttribute('data-tool-call', JSON.stringify({
                            agent_type: agentType,
                            message: initialMessage,
                            tool_call_id: toolCallId
                        }));

                        // Add tool response so LLM knows the tool was executed
                        const toolResponseMsg = document.createElement('div');
                        toolResponseMsg.className = 'message tool';
                        toolResponseMsg.style.display = 'none';
                        toolResponseMsg.setAttribute('data-tool-response', JSON.stringify({
                            tool_call_id: toolCallId,
                            content: `Launched ${agentType} agent with task: ${initialMessage}`
                        }));
                        chatContainer.appendChild(toolResponseMsg);

                        // The action widget will show the launch visually
                        handleActionToken(agentType, initialMessage, (targetTabId) => {
                            showActionWidget(chatContainer, agentType, initialMessage, targetTabId, taskId);
                            // Store tool call ID for this agent tab so we can send result back
                            toolCallIds[targetTabId] = toolCallId;
                        }, taskId, tabId);

                        // Reset current message element so any subsequent thinking starts fresh
                        currentMessageEl = null;

                    } else if (data.type === 'debug_call_input') {
                        // Debug: LLM call input (before API call)
                        if (!debugHistory[tabId]) debugHistory[tabId] = [];
                        debugHistory[tabId].push({
                            call_number: data.call_number,
                            timestamp: new Date().toLocaleTimeString(),
                            input: data.messages,
                            output: null,
                            error: null
                        });
                        if (document.getElementById('debugPanel')?.classList.contains('active')) loadDebugMessages();

                    } else if (data.type === 'debug_call_output') {
                        // Debug: LLM call output (after API call)
                        // Match the last pending call (call_numbers reset per streaming request)
                        const calls = debugHistory[tabId] || [];
                        const call = calls.findLast(c => c.output === null && c.error === null);
                        if (call) {
                            call.output = data.response || null;
                            call.error = data.error || null;
                        }
                        if (document.getElementById('debugPanel')?.classList.contains('active')) loadDebugMessages();

                    } else if (data.type === 'aborted') {
                        // Agent was aborted by user
                        hideProgressWidget(chatContainer);
                        removeRetryIndicator(chatContainer);

                        // Mark the action widget as aborted (show × instead of ✓)
                        const widget = actionWidgets[tabId];
                        if (widget) {
                            const orbitIndicator = widget.querySelector('.orbit-indicator');
                            if (orbitIndicator) {
                                const abortedIndicator = document.createElement('div');
                                abortedIndicator.className = 'done-indicator aborted';
                                orbitIndicator.replaceWith(abortedIndicator);
                            }
                        }

                        // For timeline agent boxes, mark as aborted
                        if (timelineData[tabId]) {
                            timelineData[tabId].aborted = true;
                        }

                        break;  // Stop reading stream

                    } else if (data.type === 'done') {
                        // Remove retry indicator on success
                        removeRetryIndicator(chatContainer);

                        // Reset research state when research agent completes
                        if (agentType === 'research' && typeof resetResearchState === 'function') {
                            // Mark all research virtual sub-agents as done
                            for (const virtualId of Object.values(researchQueryTabIds)) {
                                setTimelineGenerating(virtualId, false);
                            }
                            researchQueryTabIds = {};
                            resetResearchState();
                        }

                        // Check for action tokens in regular agents (legacy support)
                        if (fullResponse) {
                            const actionMatch = fullResponse.match(/<action:(agent|code|research|chat)>([\s\S]*?)<\/action>/i);
                            if (actionMatch) {
                                const action = actionMatch[1].toLowerCase();
                                const actionMessage = actionMatch[2].trim();

                                // Remove action token from fullResponse
                                const cleanedResponse = fullResponse.replace(/<action:(agent|code|research|chat)>[\s\S]*?<\/action>/i, '').trim();

                                // Update the display to remove action tags
                                if (cleanedResponse.length === 0 && currentMessageEl) {
                                    currentMessageEl.remove();
                                } else if (currentMessageEl) {
                                    // Clear and replace the entire message content
                                    const messageContent = currentMessageEl.querySelector('.message-content');
                                    if (messageContent) {
                                        messageContent.innerHTML = parseMarkdown(cleanedResponse);
                                        linkifyFilePaths(messageContent);
                                    }
                                }

                                handleActionToken(action, actionMessage, (targetTabId) => {
                                    showActionWidget(chatContainer, action, actionMessage, targetTabId);
                                }, null, tabId);
                            }
                        }

                    } else if (data.type === 'info') {
                        // Info message (e.g., sandbox restart)
                        const infoDiv = document.createElement('div');
                        infoDiv.className = 'system-message';
                        infoDiv.innerHTML = `<em>${escapeHtml(data.content)}</em>`;
                        infoDiv.style.color = 'var(--theme-accent)';
                        chatContainer.appendChild(infoDiv);
                        scrollChatToBottom(chatContainer);

                    } else if (data.type === 'retry') {
                        // Show retry indicator
                        showRetryIndicator(chatContainer, data);

                    } else if (data.type === 'error') {
                        // Remove any retry indicator before showing error
                        removeRetryIndicator(chatContainer);
                        const errorDiv = document.createElement('div');
                        errorDiv.className = 'message assistant';
                        errorDiv.innerHTML = `<div class="message-content" style="color: #c62828;">Error: ${escapeHtml(data.content)}</div>`;
                        chatContainer.appendChild(errorDiv);
                        scrollChatToBottom(chatContainer);

                        // Propagate error to parent action widget
                        updateActionWidgetWithResult(tabId, `Error: ${data.content}`, {});
                        const errorWidget = actionWidgets[tabId];
                        if (errorWidget) {
                            const doneIndicator = errorWidget.querySelector('.done-indicator');
                            if (doneIndicator) {
                                doneIndicator.classList.add('errored');
                            }
                        }
                    }
                }
            }
        }

        // Add assistant response to timeline
        if (fullResponse && tabId !== undefined) {
            const finalEvIdx = addTimelineEvent(tabId, 'assistant', fullResponse);
            if (currentMessageEl) currentMessageEl.dataset.timelineIndex = finalEvIdx;
        }
    } catch (error) {
        hideProgressWidget(chatContainer);
        if (error.name === 'AbortError') {
            // User-initiated abort — show as a result block
            const abortResultText = 'Generation aborted by user.';
            const resultDiv = document.createElement('div');
            resultDiv.className = 'agent-result';
            resultDiv.innerHTML = `
                <div class="result-header">Result</div>
                <div class="result-content"><p>${abortResultText}</p></div>
            `;
            chatContainer.appendChild(resultDiv);

            // Send abort result to parent action widget (so command center knows it was aborted)
            updateActionWidgetWithResult(tabId, abortResultText, {});

            // Override the done indicator to show × instead of ✓
            const widget = actionWidgets[tabId];
            if (widget) {
                const doneIndicator = widget.querySelector('.done-indicator');
                if (doneIndicator) {
                    doneIndicator.classList.add('aborted');
                }
            }

            // Mark timeline data as aborted
            if (timelineData[tabId]) {
                timelineData[tabId].aborted = true;
            }
        } else {
            const errorDiv = document.createElement('div');
            errorDiv.className = 'message assistant';
            errorDiv.innerHTML = `<div class="message-content" style="color: #c62828;">Connection error: ${escapeHtml(error.message)}</div>`;
            chatContainer.appendChild(errorDiv);
        }
        if (tabId) {
            setTabGenerating(tabId, false);
        }
    } finally {
        // Clean up abort controller
        delete activeAbortControllers[tabId];
    }
}

function createAssistantMessage(chatContainer) {
    const msg = document.createElement('div');
    msg.className = 'message assistant';
    msg.innerHTML = '<div class="message-content"></div>';
    chatContainer.appendChild(msg);
    return msg;
}

function appendToMessage(messageEl, content) {
    const contentEl = messageEl.querySelector('.message-content');
    if (contentEl) {
        contentEl.innerHTML = content;
        linkifyFilePaths(contentEl);
    }
}

function createSpinnerHtml() {
    return `<div class="tool-spinner"><span></span><span></span><span></span></div>`;
}

function createCodeCell(chatContainer, code, output, isError, isExecuting = false) {
    const codeCell = document.createElement('div');
    codeCell.className = 'code-cell';

    let outputHtml = '';
    const cleanedOutput = cleanCodeOutput(output);
    if (cleanedOutput && !isExecuting) {
        outputHtml = `<div class="code-cell-output${isError ? ' error' : ''}">${escapeHtml(cleanedOutput)}</div>`;
    }

    const spinnerHtml = isExecuting ? createSpinnerHtml() : '';

    codeCell.innerHTML = `
        <div class="code-cell-label"><div class="widget-collapse-toggle"></div><span>CODE</span>${spinnerHtml}</div>
        <div class="code-cell-code"><pre><code class="language-python">${escapeHtml(code)}</code></pre></div>
        ${outputHtml}
    `;
    setupCollapseToggle(codeCell, '.code-cell-label');
    chatContainer.appendChild(codeCell);

    // Apply syntax highlighting
    if (typeof Prism !== 'undefined') {
        const codeBlock = codeCell.querySelector('code.language-python');
        if (codeBlock) {
            Prism.highlightElement(codeBlock);
        }
    }
}

function createFileTransferCell(chatContainer, type, paths, output, isExecuting = false) {
    const cell = document.createElement('div');
    cell.className = 'action-widget';

    const label = type === 'upload' ? 'UPLOAD' : 'DOWNLOAD';
    const hasError = output && output.includes('Error:');

    // Indicator: spinner while executing, checkmark when done
    const indicatorHtml = isExecuting
        ? `<div class="orbit-indicator"><span></span><span></span><span></span></div>`
        : `<div class="done-indicator"></div>`;

    // Format paths as list items (make local paths clickable for downloads)
    const pathsList = paths.map(p => {
        if (type === 'download') {
            const arrowIdx = p.indexOf(' -> ');
            if (arrowIdx !== -1) {
                const localPath = p.substring(arrowIdx + 4);
                return `<li>${escapeHtml(p.substring(0, arrowIdx + 4))}<a class="transfer-path-link" href="#" data-path="${escapeHtml(localPath)}">${escapeHtml(localPath)}</a></li>`;
            }
        }
        return `<li>${escapeHtml(p)}</li>`;
    }).join('');

    let outputHtml = '';
    if (output && !isExecuting) {
        const outputClass = hasError ? 'transfer-output error' : 'transfer-output';
        outputHtml = `<div class="${outputClass}">${escapeHtml(output)}</div>`;
    }

    cell.innerHTML = `
        <div class="action-widget-header">
            <div class="widget-collapse-toggle"></div>
            <span class="action-widget-type">${label}</span>
            <div class="action-widget-bar-right">${indicatorHtml}</div>
        </div>
        <div class="action-widget-body">
            <ul class="transfer-paths">${pathsList}</ul>
            ${outputHtml}
        </div>
    `;
    cell.querySelector('.action-widget-header').style.cursor = 'pointer';
    cell.querySelector('.action-widget-header').addEventListener('click', () => {
        cell.classList.toggle('collapsed');
        cell.querySelector('.widget-collapse-toggle').classList.toggle('collapsed');
    });
    // Make download path links clickable to navigate in file explorer
    cell.querySelectorAll('.transfer-path-link').forEach(link => {
        link.addEventListener('click', (e) => {
            e.preventDefault();
            navigateToFileInExplorer(link.dataset.path);
        });
    });
    chatContainer.appendChild(cell);
    return cell;
}

function createUploadMessage(chatContainer, paths, output) {
    createFileTransferCell(chatContainer, 'upload', paths, output, false);
}

function createDownloadMessage(chatContainer, paths, output) {
    createFileTransferCell(chatContainer, 'download', paths, output, false);
}

function updateLastCodeCell(chatContainer, output, isError, images) {
    const codeCells = chatContainer.querySelectorAll('.code-cell');
    if (codeCells.length === 0) return;

    const lastCell = codeCells[codeCells.length - 1];

    // Remove spinner if present
    const spinner = lastCell.querySelector('.tool-spinner');
    if (spinner) {
        spinner.remove();
    }

    // Remove existing output if any
    const existingOutput = lastCell.querySelector('.code-cell-output');
    if (existingOutput) {
        existingOutput.remove();
    }

    // Add images if any
    if (images && images.length > 0) {
        for (const img of images) {
            const imgDiv = document.createElement('div');
            imgDiv.className = 'code-cell-image';

            // Add figure label if available
            if (img.name) {
                const label = document.createElement('div');
                label.className = 'figure-label';
                label.textContent = img.name;
                imgDiv.appendChild(label);
            }

            if (img.type === 'png' || img.type === 'jpeg') {
                const imgEl = document.createElement('img');
                imgEl.src = `data:image/${img.type};base64,${img.data}`;
                imgEl.onclick = function() { openImageModal(this.src); };
                imgDiv.appendChild(imgEl);
            } else if (img.type === 'svg') {
                const svgContainer = document.createElement('div');
                svgContainer.innerHTML = atob(img.data);
                imgDiv.appendChild(svgContainer);
            }

            lastCell.appendChild(imgDiv);
        }
    }

    // Add text output
    const cleanedOut = cleanCodeOutput(output);
    if (cleanedOut) {
        const outputDiv = document.createElement('div');
        outputDiv.className = `code-cell-output${isError ? ' error' : ''}`;
        outputDiv.textContent = cleanedOut;
        lastCell.appendChild(outputDiv);
    }
}

function showActionWidget(chatContainer, action, message, targetTabId, taskId = null) {
    const widget = document.createElement('div');
    widget.className = 'action-widget';
    if (document.getElementById('collapseAgentsCheckbox')?.checked) {
        widget.classList.add('collapsed');
    }
    widget.dataset.targetTabId = targetTabId;

    // Display task_id as title if provided
    const titleDisplay = taskId ? taskId : action.toUpperCase();
    const agentCollapsed = document.getElementById('collapseAgentsCheckbox')?.checked;

    widget.innerHTML = `
        <div class="action-widget-clickable">
            <div class="action-widget-header">
                <div class="widget-collapse-toggle${agentCollapsed ? ' collapsed' : ''}"></div>
                <span class="action-widget-type">${action.toUpperCase()}: ${escapeHtml(titleDisplay)}</span>
                <div class="action-widget-bar-right">
                    <div class="orbit-indicator">
                        <span></span><span></span><span></span>
                    </div>
                </div>
            </div>
        </div>
        <div class="action-widget-body">
            <div class="section-label">QUERY</div>
            <div class="section-content">${parseMarkdown(message)}</div>
        </div>
    `;

    // Collapse toggle — stop propagation so it doesn't navigate to the agent tab
    const collapseToggle = widget.querySelector('.widget-collapse-toggle');
    collapseToggle.addEventListener('click', (e) => {
        e.stopPropagation();
        widget.classList.toggle('collapsed');
        collapseToggle.classList.toggle('collapsed');
    });

    // Make header clickable to jump to the agent
    const clickableArea = widget.querySelector('.action-widget-clickable');

    const clickHandler = () => {
        const tabId = parseInt(targetTabId);
        // Check if the tab still exists (use .tab to avoid matching timeline elements)
        const tab = document.querySelector(`.tab[data-tab-id="${tabId}"]`);
        if (tab) {
            // Tab exists, just switch to it
            switchToTab(tabId);
        } else {
            // Tab was closed - restore from timeline data
            const notebook = timelineData[tabId];
            if (notebook) {
                reopenClosedTab(tabId, notebook);
            }
        }
    };

    clickableArea.addEventListener('click', clickHandler);

    chatContainer.appendChild(widget);
    scrollChatToBottom(chatContainer);

    // Store widget for later updates
    actionWidgets[targetTabId] = widget;
}

async function updateActionWidgetWithResult(tabId, resultContent, figures) {
    const widget = actionWidgets[tabId];
    if (!widget) return;

    // Replace orbiting dots with checkmark
    const orbitIndicator = widget.querySelector('.orbit-indicator');
    if (orbitIndicator) {
        const doneIndicator = document.createElement('div');
        doneIndicator.className = 'done-indicator';
        orbitIndicator.replaceWith(doneIndicator);
    }

    // Process and display result content FIRST (before async operations)
    // Replace <figure_x> tags with placeholders BEFORE markdown processing
    let processedContent = resultContent;
    const figurePlaceholders = {};

    if (figures) {
        for (const [figureName, figureData] of Object.entries(figures)) {
            // Use %%% delimiters to avoid markdown interpretation
            const placeholderId = `%%%FIGURE_${figureName}%%%`;
            figurePlaceholders[placeholderId] = figureData;

            // Handle both <figure_x> self-closing and <figure_x></figure_x> pairs
            // First replace paired tags, preserving them as block elements
            const pairedTag = new RegExp(`<${figureName}></${figureName}>`, 'gi');
            processedContent = processedContent.replace(pairedTag, `\n\n${placeholderId}\n\n`);

            // Then replace remaining self-closing tags or orphaned closing tags
            const singleTag = new RegExp(`</?${figureName}>`, 'gi');
            processedContent = processedContent.replace(singleTag, `\n\n${placeholderId}\n\n`);
        }
    }

    // Process markdown
    let html = parseMarkdown(processedContent);

    // Replace placeholders with actual images AFTER markdown processing
    for (const [placeholderId, figureData] of Object.entries(figurePlaceholders)) {
        let imageHtml = '';
        if (figureData.type === 'png' || figureData.type === 'jpeg') {
            imageHtml = `<img src="data:image/${figureData.type};base64,${figureData.data}" style="max-width: 400px; max-height: 400px; height: auto; border-radius: 4px; margin: 12px 0; display: block;" onclick="openImageModal(this.src)">`;
        } else if (figureData.type === 'svg') {
            imageHtml = `<div style="margin: 12px 0;">${atob(figureData.data)}</div>`;
        }
        // Replace both the placeholder and any paragraph-wrapped version
        html = html.replace(new RegExp(`<p>${placeholderId}</p>`, 'g'), imageHtml);
        html = html.replace(new RegExp(placeholderId, 'g'), imageHtml);
    }

    // Add result section inside the body
    const body = widget.querySelector('.action-widget-body');
    if (body) {
        const resultSection = document.createElement('div');
        resultSection.className = 'action-widget-result-section';
        resultSection.innerHTML = `
            <div class="section-label" style="margin-top: 10px; padding-top: 10px; border-top: 1px solid var(--border-primary);">RESULT</div>
            <div class="section-content">${html}</div>
        `;
        body.appendChild(resultSection);
    }

    // Update the tool response DOM element so getConversationHistory picks up actual results
    const toolCallId = toolCallIds[tabId];
    if (toolCallId) {
        // Find the hidden tool response element with this tool_call_id in the command center
        const commandContainer = document.getElementById('messages-command');
        if (commandContainer) {
            const toolMsgs = commandContainer.querySelectorAll('.message.tool[data-tool-response]');
            for (const toolMsg of toolMsgs) {
                try {
                    const data = JSON.parse(toolMsg.getAttribute('data-tool-response'));
                    if (data.tool_call_id === toolCallId) {
                        data.content = resultContent;
                        toolMsg.setAttribute('data-tool-response', JSON.stringify(data));
                        break;
                    }
                } catch (e) { /* ignore parse errors */ }
            }
        }

        // Also send to backend (non-blocking)
        apiFetch('/api/conversation/add-tool-response', {
            method: 'POST',
            headers: { 'Content-Type': 'application/json' },
            body: JSON.stringify({
                tab_id: '0',
                tool_call_id: toolCallId,
                content: resultContent
            })
        }).catch(error => {
            console.error('Failed to update conversation history with result:', error);
        });
    }
}

function sendMessageToTab(tabId, message) {
    // Programmatically send a message to an existing agent tab
    const content = document.querySelector(`[data-content-id="${tabId}"]`);
    if (!content) return;

    const input = content.querySelector('textarea') || content.querySelector('input[type="text"]');
    if (!input) return;

    // Set the message and trigger send
    input.value = message;
    sendMessage(tabId);
}

function handleActionToken(action, message, callback, taskId = null, parentTabId = null) {
    // Check if an agent with this task_id already exists
    if (taskId && taskIdToTabId[taskId]) {
        const existingTabId = taskIdToTabId[taskId];
        const existingContent = document.querySelector(`[data-content-id="${existingTabId}"]`);

        if (existingContent) {
            // Only reuse if the agent type matches — different type with same task_id should create a new tab
            const existingType = existingContent.querySelector('.chat-container')?.dataset?.agentType;
            if (existingType === action) {
                // Send the message to the existing agent
                sendMessageToTab(existingTabId, message);
                if (callback) {
                    callback(existingTabId);
                }
                return;
            }
        } else {
            // Tab no longer exists, clean up the mapping
            delete taskIdToTabId[taskId];
        }
    }

    // Open the agent with the extracted message as initial prompt
    // Don't auto-switch to the new tab (autoSwitch = false)
    setTimeout(() => {
        const newTabId = createAgentTab(action, message, false, taskId, parentTabId);
        if (callback) {
            callback(newTabId);
        }
    }, 500);
}

function setTabGenerating(tabId, isGenerating) {
    const tab = document.querySelector(`[data-tab-id="${tabId}"]`);
    if (!tab) return;

    const statusIndicator = tab.querySelector('.tab-status');
    if (!statusIndicator) return;

    if (isGenerating) {
        statusIndicator.style.display = 'block';
        statusIndicator.classList.add('generating');
    } else {
        statusIndicator.classList.remove('generating');
        // Keep visible but stop animation
        setTimeout(() => {
            statusIndicator.style.display = 'none';
        }, 300);
    }

    // Toggle SEND/STOP button
    const content = document.querySelector(`[data-content-id="${tabId}"]`);
    if (content) {
        const sendBtn = content.querySelector('.input-container button');
        if (sendBtn) {
            if (isGenerating) {
                sendBtn.textContent = 'STOP';
                sendBtn.classList.add('stop-btn');
                sendBtn.disabled = false;  // Keep enabled so user can click STOP
            } else {
                sendBtn.textContent = 'SEND';
                sendBtn.classList.remove('stop-btn');
            }
        }
    }

    // Update timeline to reflect generating state
    setTimelineGenerating(tabId, isGenerating);

    // Track when a pending agent launch actually starts generating
    if (isGenerating && pendingAgentLaunches > 0 && tabId !== 0 && timelineData[tabId]?.parentTabId === 0) {
        pendingAgentLaunches--;
    }

    // When a child agent finishes and command center is blocked, check if all agents are done
    if (!isGenerating && commandInputBlocked && tabId !== 0) {
        const anyStillGenerating = Object.values(timelineData).some(
            td => td.parentTabId === 0 && td.isGenerating
        );
        if (!anyStillGenerating && pendingAgentLaunches === 0) {
            commandInputBlocked = false;
            setCommandCenterStopState(false);
            // Auto-continue: call command center again with agent results now in history
            continueCommandCenter();
        }
    }
}


function cleanCodeOutput(text) {
    if (!text) return text;
    return text.split('\n')
        .filter(line => !line.match(/^\[Plot\/Image generated\]$/) && !line.match(/^\[Generated figures:.*\]$/))
        .join('\n')
        .trim();
}

function showRetryIndicator(chatContainer, data) {
    // Remove existing retry indicator if present
    removeRetryIndicator(chatContainer);

    const retryDiv = document.createElement('div');
    retryDiv.className = 'retry-indicator';
    retryDiv.innerHTML = `
        <div class="retry-content">
            <div class="retry-spinner"></div>
            <div class="retry-text">
                <div class="retry-message">${escapeHtml(data.message)}</div>
                <div class="retry-status">Retrying (${data.attempt}/${data.max_attempts}) in ${data.delay}s...</div>
            </div>
        </div>
    `;
    chatContainer.appendChild(retryDiv);
    scrollChatToBottom(chatContainer);

    // Start countdown
    let remaining = data.delay;
    const statusEl = retryDiv.querySelector('.retry-status');
    const countdownInterval = setInterval(() => {
        remaining--;
        if (remaining > 0 && statusEl) {
            statusEl.textContent = `Retrying (${data.attempt}/${data.max_attempts}) in ${remaining}s...`;
        } else {
            clearInterval(countdownInterval);
            if (statusEl) {
                statusEl.textContent = `Retrying (${data.attempt}/${data.max_attempts})...`;
            }
        }
    }, 1000);

    // Store interval ID for cleanup
    retryDiv.dataset.countdownInterval = countdownInterval;
}

function removeRetryIndicator(chatContainer) {
    const existing = chatContainer.querySelector('.retry-indicator');
    if (existing) {
        // Clear countdown interval if exists
        if (existing.dataset.countdownInterval) {
            clearInterval(parseInt(existing.dataset.countdownInterval));
        }
        existing.remove();
    }
}

// Configure marked options once
if (typeof marked !== 'undefined') {
    // Custom renderer to add target="_blank" to links and syntax highlighting
    const renderer = new marked.Renderer();

    // Handle both old API (separate args) and new API (token object)
    renderer.link = function(hrefOrToken, title, text) {
        const href = typeof hrefOrToken === 'object' ? hrefOrToken.href : hrefOrToken;
        const titleVal = typeof hrefOrToken === 'object' ? hrefOrToken.title : title;
        const textVal = typeof hrefOrToken === 'object' ? hrefOrToken.text : text;
        const titleAttr = titleVal ? ` title="${titleVal}"` : '';
        return `<a href="${href}"${titleAttr} target="_blank" rel="noopener noreferrer">${textVal}</a>`;
    };

    renderer.code = function(codeOrToken, language) {
        // Handle both old API (separate args) and new API (token object)
        const code = typeof codeOrToken === 'object' ? codeOrToken.text : codeOrToken;
        const lang = typeof codeOrToken === 'object' ? codeOrToken.lang : language;

        // Use Prism for syntax highlighting if available
        if (typeof Prism !== 'undefined' && lang && Prism.languages[lang]) {
            const highlighted = Prism.highlight(code, Prism.languages[lang], lang);
            return `<pre><code class="language-${lang}">${highlighted}</code></pre>`;
        }
        return `<pre><code>${escapeHtml(code)}</code></pre>`;
    };

    marked.setOptions({
        gfm: true,           // GitHub Flavored Markdown
        breaks: false,       // Don't convert \n to <br>
        pedantic: false,
        renderer: renderer
    });
}

// Resolve <figure_N> and <image_N> references using the global registry
function resolveGlobalFigureRefs(html) {
    return html.replace(/<\/?(figure_(?:T\d+_)?\d+|image_(?:T\d+_)?\d+)>/gi, (match) => {
        // Extract the name (strip < > and /)
        const name = match.replace(/[<>/]/g, '');
        const data = globalFigureRegistry[name];
        if (!data) return match; // Leave unresolved refs as-is
        if (data.type === 'png' || data.type === 'jpeg') {
            return `<img src="data:image/${data.type};base64,${data.data}" style="max-width: 400px; max-height: 400px; height: auto; border-radius: 4px; margin: 12px 0; display: block;" onclick="openImageModal(this.src)">`;
        } else if (data.type === 'svg') {
            return `<div style="margin: 12px 0;">${atob(data.data)}</div>`;
        }
        return match;
    });
}

function parseMarkdown(text) {
    // Use marked library for proper markdown parsing
    let html;
    if (typeof marked !== 'undefined') {
        html = marked.parse(text);
    } else {
        // Fallback: just escape HTML and convert newlines to paragraphs
        html = `<p>${escapeHtml(text).replace(/\n\n/g, '</p><p>').replace(/\n/g, '<br>')}</p>`;
    }

    // Render LaTeX with KaTeX if available
    if (typeof katex !== 'undefined') {
        // Block math: $$ ... $$ (must handle newlines)
        html = html.replace(/\$\$([\s\S]*?)\$\$/g, (match, latex) => {
            try {
                return katex.renderToString(latex.trim(), { displayMode: true, throwOnError: false });
            } catch (e) {
                return `<span class="katex-error">${escapeHtml(match)}</span>`;
            }
        });

        // Inline math: $ ... $ (but not $$ or escaped \$)
        html = html.replace(/(?<!\$)\$(?!\$)([^\$\n]+?)\$(?!\$)/g, (match, latex) => {
            try {
                return katex.renderToString(latex.trim(), { displayMode: false, throwOnError: false });
            } catch (e) {
                return `<span class="katex-error">${escapeHtml(match)}</span>`;
            }
        });
    }

    return html;
}