feat: implement DS2API_HISTORY.txt transcript parser to merge history into chat messages

tests/node/chat-history-utils.test.js

@@ -58,3 +58,47 @@ test('chat history strict parser inserts history after system messages', async (
     { role: 'user', content: 'latest' },
   ]);
 });
+
+test('chat history transcript parser replaces current input file placeholder', async () => {
+  const {
+    buildListModeMessages,
+  } = await loadUtils();
+  const t = (key) => key;
+  const item = {
+    messages: [{
+      role: 'user',
+      content: 'Continue from the latest state in the attached DS2API_HISTORY.txt context. Treat it as the current working state and answer the latest user request directly.',
+    }],
+    history_text: [
+      '# DS2API_HISTORY.txt',
+      'Prior conversation history and tool progress.',
+      '',
+      '=== 1. SYSTEM ===',
+      'policy',
+      '',
+      '=== 2. USER ===',
+      'hello',
+      '',
+      '=== 3. ASSISTANT ===',
+      'hi',
+      '',
+      '=== 4. TOOL ===',
+      '[name=search_web tool_call_id=call_1]',
+      '{"ok":true}',
+      '',
+      '=== 5. USER ===',
+      'latest',
+      '',
+    ].join('\n'),
+  };
+
+  const result = buildListModeMessages(item, t);
+  assert.equal(result.historyMerged, true);
+  assert.deepEqual(result.messages, [
+    { role: 'system', content: 'policy' },
+    { role: 'user', content: 'hello' },
+    { role: 'assistant', content: 'hi' },
+    { role: 'tool', content: '[name=search_web tool_call_id=call_1]\n{"ok":true}' },
+    { role: 'user', content: 'latest' },
+  ]);
+});

webui/src/features/chatHistory/chatHistoryUtils.js

@@ -15,12 +15,24 @@ const CURRENT_INPUT_FILE_PROMPT = 'Continue from the latest state in the attache
 const LEGACY_CURRENT_INPUT_FILE_PROMPTS = new Set([
     'The current request and prior conversation context have already been provided. Answer the latest user request directly.',
 ])
+const HISTORY_TRANSCRIPT_TITLE = '# DS2API_HISTORY.txt'
+const HISTORY_TRANSCRIPT_ENTRY_RE = /^===\s+\d+\.\s+([A-Z][A-Z_ -]*)\s+===\s*$/gm
 
 function isCurrentInputFilePrompt(value) {
     const text = String(value || '').trim()
     return text === CURRENT_INPUT_FILE_PROMPT || LEGACY_CURRENT_INPUT_FILE_PROMPTS.has(text)
 }
 
+function normalizeHistoryRole(role) {
+    const normalized = String(role || '').trim().toLowerCase()
+    if (normalized === 'function') return 'tool'
+    if (normalized === 'developer') return 'system'
+    if (normalized === 'system' || normalized === 'user' || normalized === 'assistant' || normalized === 'tool') {
+        return normalized
+    }
+    return normalized || 'system'
+}
+
 export function formatDateTime(value, lang) {
     if (!value) return '-'
     try {
@@ -221,11 +233,37 @@ export function parseStrictHistoryMessages(historyText) {
     return parsed
 }
 
+export function parseTranscriptHistoryMessages(historyText) {
+    const rawText = String(historyText || '')
+    const titleIndex = rawText.indexOf(HISTORY_TRANSCRIPT_TITLE)
+    const transcript = titleIndex >= 0 ? rawText.slice(titleIndex) : rawText
+    const matches = [...transcript.matchAll(HISTORY_TRANSCRIPT_ENTRY_RE)]
+    if (!matches.length) return null
+
+    const parsed = []
+    for (let i = 0; i < matches.length; i += 1) {
+        const match = matches[i]
+        const next = matches[i + 1]
+        const role = normalizeHistoryRole(match[1])
+        const start = (match.index || 0) + match[0].length
+        const end = next ? next.index : transcript.length
+        const content = transcript.slice(start, end).replace(/^\r?\n/, '').trim()
+        if (!content) continue
+        parsed.push({ role, content })
+    }
+
+    return parsed.length ? parsed : null
+}
+
+export function parseHistoryMessages(historyText) {
+    return parseStrictHistoryMessages(historyText) || parseTranscriptHistoryMessages(historyText)
+}
+
 export function buildListModeMessages(item, t) {
     const liveMessages = Array.isArray(item?.messages) && item.messages.length > 0
         ? item.messages
         : [{ role: 'user', content: item?.user_input || t('chatHistory.emptyUserInput') }]
-    const historyMessages = parseStrictHistoryMessages(item?.history_text)
+    const historyMessages = parseHistoryMessages(item?.history_text)
 
     if (!historyMessages?.length) {
         return { messages: liveMessages, historyMerged: false }