function startEventStream(message) {
    if (isStreaming) return;
    if (!currentChatId) {
        console.error("Cannot start stream without a current chat ID.");
        return;
    }
    setStreamingState(true);

    if (currentEventSource) {
        currentEventSource.close();
    }

    const selectedRagTag = ragSelect.value; // Keep RAG selection logic
    const selectedAiModelValue = aiModelSelect.value;
    const selectedAiModelName = aiModelSelect.options[aiModelSelect.selectedIndex].getAttribute('model');

    if (!selectedAiModelName) {
        console.error("No AI model name selected!");
        setStreamingState(false);
        appendMessage("错误：未选择有效的 AI 模型。", true, false);
        return;
    }

    // --- WORKAROUND START ---
    // 1. Get chat history
    const chatData = getChatData(currentChatId);
    const history = chatData ? chatData.messages : [];

    // 2. Format history into a single string to prepend
    let historyString = "";
    // Limit history length to avoid excessively long URLs (adjust maxHistory as needed)
    const maxHistory = 10; // Example: Keep last 10 messages
    const startIndex = Math.max(0, history.length - maxHistory);

    for (let i = startIndex; i < history.length; i++) {
        const msg = history[i];
        if (typeof msg.content === 'string' && typeof msg.isAssistant === 'boolean') {
            // Important: Exclude <think> tags from the history string sent to the model
            // unless your model is specifically trained to handle them as part of the prompt.
            // Usually, you only want the actual conversation turns.
            const contentWithoutThink = msg.content.replace(/<think>.*?<\/think>/gs, '').trim();
            if (contentWithoutThink) { // Only add if there's actual content after removing think tags
                historyString += (msg.isAssistant ? "Assistant: " : "User: ") + contentWithoutThink + "\n";
            }
        }
    }

    // 3. Prepend history to the current message
    const combinedMessage = historyString + "User: " + message; // Clearly mark the new message
    // --- WORKAROUND END ---


    let url;
    const base = `http://localhost:7080/api/v1/${selectedAiModelValue}`;

    // --- Send the COMBINED message in the 'message' parameter ---
    const params = new URLSearchParams({
        // Send the combined history+current message string
        message: combinedMessage,
        model: selectedAiModelName
        // NO 'history' parameter here
    });

    if (selectedRagTag) {
        params.append('ragTag', selectedRagTag);
        // Decide how RAG interacts with history prepending.
        // Does the backend RAG process need the raw message or the combined one?
        // Assuming backend handles RAG based on the full 'message' param for now.
        url = `${base}/generate_stream_rag?${params.toString()}`;
    } else {
        url = `${base}/generate_stream?${params.toString()}`;
    }
    // --- END MODIFICATION ---

    console.log("Streaming URL (Workaround):", url); // URL will have a long 'message' param
    console.log("Combined Message sent:", combinedMessage); // Log the combined string

    currentEventSource = new EventSource(url);
    let accumulatedContent = '';
    let tempMessageWrapper = null;
    let streamEnded = false;
    const messageId = `ai-message-${Date.now()}`;

    // --- Create Unified Placeholder ---
    if (chatArea.style.display === 'none') {
        chatArea.style.display = 'block';
        welcomeMessage.style.display = 'none';
    }
    tempMessageWrapper = document.createElement('div');
    tempMessageWrapper.className = 'flex w-full mb-4 message-bubble justify-start';
    tempMessageWrapper.id = messageId;
    tempMessageWrapper.innerHTML = `
        <div class="flex gap-3 max-w-4xl w-full">
             <div class="w-8 h-8 rounded-full bg-green-100 flex items-center justify-center flex-shrink-0 mt-1 shadow-sm">
                <span class="text-green-600 text-sm font-semibold">AI</span>
            </div>
            <div class="message-content-wrapper bg-white border border-gray-200 px-4 py-3 rounded-lg shadow-sm min-w-[80px] flex-grow markdown-body">
                 <span class="streaming-cursor animate-pulse">▋</span>
            </div>
        </div>
    `;
    chatArea.appendChild(tempMessageWrapper);
    let messageContentWrapper = tempMessageWrapper.querySelector('.message-content-wrapper');
    let hasInjectedDetails = false;
    requestAnimationFrame(() => {
        chatArea.scrollTop = chatArea.scrollHeight;
    });


    // The rest of the onmessage, onerror, DOM handling logic remains the same
    // as in the previous snippet. The AI's response (accumulatedContent)
    // is still processed and displayed identically.
    currentEventSource.onmessage = function (event) {
        // ... (SAME onmessage logic as before - handling stream data, <think> tags, DOM updates) ...
        if (streamEnded) return;

        try {
            const data = JSON.parse(event.data);

            if (data.result?.output?.text !== undefined) {
                const newContent = data.result.output.text ?? '';
                accumulatedContent += newContent;

                // --- Process Accumulated Content ---
                const thinkRegex = /<think>(.*?)<\/think>/gs;
                let thinkingSteps = '';
                let match;
                const localThinkRegex = /<think>(.*?)<\/think>/gs;
                while ((match = localThinkRegex.exec(accumulatedContent)) !== null) {
                    thinkingSteps += match[1] + '\n';
                }
                thinkingSteps = thinkingSteps.trim();
                const finalAnswer = accumulatedContent.replace(/<think>.*?<\/think>/gs, '').trim();

                // --- Update DOM Dynamically ---
                messageContentWrapper = document.getElementById(messageId)?.querySelector('.message-content-wrapper');
                if (!messageContentWrapper) {
                    console.error("Message wrapper not found!");
                    return;
                }

                if (thinkingSteps && !hasInjectedDetails) {
                    messageContentWrapper.innerHTML = `
                        <details class="thinking-process" open>
                            <summary class="cursor-pointer text-sm text-gray-600 hover:text-gray-800 mb-2 focus:outline-none select-none">
                                思考过程... <span class="text-xs opacity-70">(点击展开/折叠)</span>
                            </summary>
                            <div class="thinking-steps-content markdown-body border-t border-gray-100 pt-2 pl-2 text-xs opacity-80 min-h-[20px]">

                            </div>
                        </details>
                        <div class="final-answer markdown-body pt-3">

                        </div>
                    `;
                    hasInjectedDetails = true;
                }

                // --- Populate Content ---
                if (hasInjectedDetails) {
                    const thinkingStepsDiv = messageContentWrapper.querySelector('.thinking-steps-content');
                    const finalAnswerDiv = messageContentWrapper.querySelector('.final-answer');

                    if (thinkingStepsDiv) {
                        thinkingStepsDiv.innerHTML = sanitizeHTML(marked.parse(thinkingSteps + '<span class="streaming-cursor animate-pulse">▋</span>'));
                        applyHighlightingAndCopyButtons(thinkingStepsDiv);
                    }
                    if (finalAnswerDiv) {
                        finalAnswerDiv.innerHTML = finalAnswer
                            ? sanitizeHTML(marked.parse(finalAnswer))
                            : '<span class="text-gray-400 text-sm">正在处理...</span>';
                        applyHighlightingAndCopyButtons(finalAnswerDiv);
                    }
                } else {
                    messageContentWrapper.innerHTML = sanitizeHTML(marked.parse(finalAnswer + '<span class="streaming-cursor animate-pulse">▋</span>'));
                    applyHighlightingAndCopyButtons(messageContentWrapper);
                }

                requestAnimationFrame(() => {
                    chatArea.scrollTop = chatArea.scrollHeight;
                });
            }

            // --- Handle Stream End ---
            if (data.result?.metadata?.finishReason === 'stop' || data.result?.metadata?.finishReason === 'STOP') {
                streamEnded = true;
                currentEventSource.close();

                // --- Final Processing of accumulatedContent ---
                const thinkRegex = /<think>(.*?)<\/think>/gs;
                let finalThinkingSteps = '';
                let match;
                const localThinkRegex = /<think>(.*?)<\/think>/gs; // Use new instance
                while ((match = localThinkRegex.exec(accumulatedContent)) !== null) {
                    finalThinkingSteps += match[1] + '\n';
                }
                finalThinkingSteps = finalThinkingSteps.trim();
                const finalFinalAnswer = accumulatedContent.replace(/<think>.*?<\/think>/gs, '').trim();

                // --- Final DOM Update ---
                messageContentWrapper = document.getElementById(messageId)?.querySelector('.message-content-wrapper');
                if (!messageContentWrapper) {
                    console.error("Message wrapper not found for final update!");
                    return;
                }

                messageContentWrapper.querySelectorAll('.streaming-cursor').forEach(c => c.remove());

                if (finalThinkingSteps) {
                    if (!hasInjectedDetails) {
                        messageContentWrapper.innerHTML = `
                            <details class="thinking-process" open>
                                <summary>思考过程 <span class="text-xs opacity-70">(来自历史记录)</span></summary>
                                <div class="thinking-steps-content markdown-body border-t border-gray-100 pt-2 pl-2 text-xs opacity-80"></div>
                            </details>
                            <div class="final-answer markdown-body pt-3"></div>
                         `;
                        hasInjectedDetails = true;
                    }
                    const thinkingStepsDiv = messageContentWrapper.querySelector('.thinking-steps-content');
                    const finalAnswerDiv = messageContentWrapper.querySelector('.final-answer');

                    if (thinkingStepsDiv) {
                        thinkingStepsDiv.innerHTML = sanitizeHTML(marked.parse(finalThinkingSteps));
                        applyHighlightingAndCopyButtons(thinkingStepsDiv);
                    } else {
                        console.error("Thinking steps div not found in final update!");
                    }

                    if (finalAnswerDiv) {
                        finalAnswerDiv.innerHTML = finalFinalAnswer ? sanitizeHTML(marked.parse(finalFinalAnswer)) : '';
                        applyHighlightingAndCopyButtons(finalAnswerDiv);
                    } else {
                        console.error("Final answer div not found in final update!");
                    }
                    // Update summary text after completion
                    const summaryElement = messageContentWrapper.querySelector('.thinking-process summary');
                    if (summaryElement) summaryElement.innerHTML = `思考过程 <span class="text-xs opacity-70">(点击展开/折叠)</span>`;


                } else {
                    messageContentWrapper.innerHTML = finalFinalAnswer ? sanitizeHTML(marked.parse(finalFinalAnswer)) : '';
                    if (!hasInjectedDetails) {
                        messageContentWrapper.classList.add('markdown-body');
                    }
                    applyHighlightingAndCopyButtons(messageContentWrapper);
                }

                // --- Save the complete message (including <think> tags) ---
                // IMPORTANT: Even with the workaround, save the ORIGINAL AI response
                // (accumulatedContent) to localStorage, *including* any <think> tags,
                // so the history display remains accurate. Don't save the combinedMessage.
                if (currentChatId && accumulatedContent.trim()) {
                    const chatData = getChatData(currentChatId);
                    if (chatData) {
                        chatData.messages.push({content: accumulatedContent, isAssistant: true});
                        localStorage.setItem(`chat_${currentChatId}`, JSON.stringify(chatData));
                        updateChatList();
                    }
                }

                currentEventSource = null;
                setStreamingState(false);
                messageInput.focus();
            }
        } catch (e) {
            console.error('Error processing stream event:', e, event.data);
        }

    };

    currentEventSource.onerror = function (error) {
        // ... (SAME onerror logic as before) ...
        console.error('EventSource encountered an error:', error);
        streamEnded = true;
        if (currentEventSource) {
            currentEventSource.close();
        }

        const errorText = '--- 抱歉，连接中断或发生错误 ---';
        messageContentWrapper = document.getElementById(messageId)?.querySelector('.message-content-wrapper');
        if (messageContentWrapper) {
            messageContentWrapper.querySelectorAll('.streaming-cursor').forEach(c => c.remove());
            const errorP = document.createElement('p');
            errorP.className = 'text-red-500 text-sm font-semibold mt-2 border-t pt-2';
            errorP.textContent = errorText;

            const finalAnswerDiv = messageContentWrapper.querySelector('.final-answer');
            if (finalAnswerDiv) {
                if (finalAnswerDiv.textContent.includes("正在处理")) finalAnswerDiv.innerHTML = '';
                finalAnswerDiv.appendChild(errorP);
            } else {
                if (messageContentWrapper.textContent === '▋') messageContentWrapper.innerHTML = '';
                messageContentWrapper.appendChild(errorP);
            }
            // Update summary text in case of error during thinking display
            const summaryElement = messageContentWrapper.querySelector('.thinking-process summary');
            if (summaryElement && summaryElement.textContent.includes("思考过程...")) {
                summaryElement.innerHTML = `思考过程 <span class="text-xs opacity-70">(已中断)</span>`;
            }

        } else {
            appendMessage(errorText, true, false);
        }

        currentEventSource = null;
        setStreamingState(false);
        messageInput.focus();
    };
}