fix: strip think tags when model emits leading whitespace before <think> (#327)

Remove ^ anchor from think/Gemma regexes in ui.js; trimStart() before startsWith checks in messages.js streaming path. Fixes MiniMax M2.7 and any model emitting leading newlines before <think>. 10 new tests, 768 total.

CHANGELOG.md

@@ -6,6 +6,13 @@
 ---
 
 
+## [v0.50.5] Think-tag stripping with leading whitespace (PR #327)
+
+- **Fix think-tag rendering for models that emit leading whitespace** (e.g. MiniMax M2.7): Some models emit one or more newlines before the `<think>` opening tag. The previous regex used a `^` anchor, so it only matched when `<think>` was the very first character. When the anchor failed, the raw `</think>` tag appeared in the rendered message body.
+  - `static/ui.js` (stored messages): removed `^` anchor from `<think>` and Gemma channel-token regexes; switched from `.slice()` to `.replace()` + `.trimStart()` so stripping works regardless of position
+  - `static/messages.js` (live stream): `trimStart()` before `startsWith`/`indexOf` checks; partial-tag-prefix guard also uses trimmed buffer
+  - 10 new tests in `tests/test_sprint38.py`; 768 tests total (up from 758)
+
 ## [v0.50.3] Onboarding completes gracefully for pre-configured providers (PR #323, fixes #322)
 
 - **OAuth/CLI-configured providers no longer blocked by onboarding** (closes #322): Users with providers already set up via the CLI (`openai-codex`, `copilot`, `nous`, etc.) hit `Unsupported provider for WebUI onboarding` when clicking "Open Hermes" on the finish page. The wizard now marks onboarding complete and lets them through — the agent setup is already done, no wizard steps needed.

static/index.html

@@ -526,7 +526,7 @@
                 <div class="settings-section-title">System</div>
                 <div class="settings-section-meta">Instance version and access controls.</div>
               </div>
-              <span class="settings-version-badge">v0.50.3</span>
+              <span class="settings-version-badge">v0.50.5</span>
             </div>
             <div class="settings-field" style="border-top:1px solid var(--border);padding-top:12px;margin-top:8px">
               <label for="settingsPassword" data-i18n="settings_label_password">Access Password</label>

static/messages.js

@@ -116,18 +116,21 @@ async function send(){
   function _streamDisplay(){
     const raw=assistantText;
     for(const {open,close} of _thinkPairs){
-      if(raw.startsWith(open)){
+      // Trim leading whitespace before checking for the open tag — some models
-        const ci=raw.indexOf(close,open.length);
+      // (e.g. MiniMax) emit newlines before <think>.
+      const trimmed=raw.trimStart();
+      if(trimmed.startsWith(open)){
+        const ci=trimmed.indexOf(close,open.length);
         if(ci!==-1){
           // Thinking block complete — strip it, show the rest
-          return raw.slice(ci+close.length).replace(/^\s+/,'');
+          return trimmed.slice(ci+close.length).replace(/^\s+/,'');
         }
         // Still inside thinking block — show placeholder
         return '';
       }
       // Hide partial tag prefixes while streaming so users don't see
       // `<thi`, `<think`, etc. before the model finishes the token.
-      if(open.startsWith(raw)) return '';
+      if(open.startsWith(trimmed)) return '';
     }
     return raw;
   }

static/ui.js

@@ -801,19 +801,20 @@ function renderMessages(){
     if(!thinkingText && m.reasoning){
       thinkingText=m.reasoning;
     }
-    // Parse inline thinking tags from plain text: <think>...</think> (DeepSeek, QwQ, etc.)
+    // Parse inline thinking tags from plain text: <think>...</think> (DeepSeek, QwQ, MiniMax, etc.)
     // and Gemma 4 channel tokens: <|channel>thought\n...<channel|>
+    // Note: no ^ anchor — some models emit leading whitespace/newlines before <think>.
     if(!thinkingText && typeof content==='string'){
-      const thinkMatch=content.match(/^<think>([\s\S]*?)<\/think>\s*/);
+      const thinkMatch=content.match(/<think>([\s\S]*?)<\/think>/);
       if(thinkMatch){
         thinkingText=thinkMatch[1].trim();
-        content=content.slice(thinkMatch[0].length);
+        content=content.replace(/<think>[\s\S]*?<\/think>\s*/,'').trimStart();
       }
       if(!thinkingText){
-        const gemmaMatch=content.match(/^<\|channel>thought\n([\s\S]*?)<channel\|>\s*/);
+        const gemmaMatch=content.match(/<\|channel>thought\n([\s\S]*?)<channel\|>/);
         if(gemmaMatch){
           thinkingText=gemmaMatch[1].trim();
-          content=content.slice(gemmaMatch[0].length);
+          content=content.replace(/<\|channel>thought\n[\s\S]*?<channel\|>\s*/,'').trimStart();
         }
       }
     }

tests/test_sprint38.py

@@ -0,0 +1,111 @@
+"""
+Sprint 38 Tests: Think-tag stripping with leading whitespace (PR #327).
+
+Covers the static render path (ui.js regex logic, verified against the JS source)
+and the streaming render path (messages.js _streamDisplay logic).
+"""
+import pathlib
+import re
+
+REPO_ROOT = pathlib.Path(__file__).parent.parent
+UI_JS     = (REPO_ROOT / "static" / "ui.js").read_text()
+MSG_JS    = (REPO_ROOT / "static" / "messages.js").read_text()
+
+
+# ── ui.js: static render path ────────────────────────────────────────────────
+
+def test_think_regex_has_no_anchor():
+    """The <think> regex in ui.js must not use a ^ anchor so leading whitespace is allowed."""
+    # Find the thinkMatch line by locating the .match( call on that line
+    idx = UI_JS.find("const thinkMatch=content.match(")
+    assert idx >= 0, "thinkMatch line not found in ui.js"
+    line = UI_JS[idx:idx+100]
+    # The regex must NOT start with ^ right after the opening /
+    assert "/^<think>" not in line and "(/^" not in line, \
+        f"thinkMatch regex must not use ^ anchor — found: {line.strip()}"
+
+
+def test_gemma_regex_has_no_anchor():
+    """The Gemma channel-token regex in ui.js must not use a ^ anchor."""
+    match = re.search(r'const gemmaMatch=content\.match\((/[^/]+/)\)', UI_JS)
+    assert match, "gemmaMatch line not found in ui.js"
+    pattern = match.group(1)
+    assert not pattern.startswith('/^'), \
+        f"gemmaMatch regex must not use ^ anchor — got {pattern}"
+
+
+def test_think_content_removal_uses_replace_not_slice():
+    """After extracting thinkingText, content must use .replace() not .slice() to remove the tag."""
+    # Find the block that handles thinkMatch
+    idx = UI_JS.find("if(thinkMatch){")
+    assert idx >= 0, "thinkMatch handler block not found"
+    block = UI_JS[idx:idx+200]
+    assert "content.replace(" in block, \
+        "ui.js must use content.replace() to remove <think> block (not .slice())"
+    assert ".trimStart()" in block, \
+        "ui.js must call .trimStart() on content after removing the <think> block"
+
+
+def test_gemma_content_removal_uses_replace_not_slice():
+    """Gemma channel token removal must also use .replace() not .slice()."""
+    idx = UI_JS.find("if(gemmaMatch){")
+    assert idx >= 0, "gemmaMatch handler block not found"
+    block = UI_JS[idx:idx+200]
+    assert "content.replace(" in block, \
+        "ui.js must use content.replace() to remove Gemma channel block (not .slice())"
+    assert ".trimStart()" in block, \
+        "ui.js must call .trimStart() on content after removing the Gemma channel block"
+
+
+# ── messages.js: streaming render path ───────────────────────────────────────
+
+def test_stream_display_trims_before_startswith():
+    """_streamDisplay in messages.js must call .trimStart() before .startsWith() check."""
+    fn_idx = MSG_JS.find("function _streamDisplay()")
+    assert fn_idx >= 0, "_streamDisplay function not found in messages.js"
+    fn_end = MSG_JS.find("\n  }", fn_idx) + 4
+    fn_body = MSG_JS[fn_idx:fn_end]
+    assert "trimStart()" in fn_body, \
+        "_streamDisplay must call trimStart() to handle models that emit leading whitespace before <think>"
+
+
+def test_stream_display_uses_trimmed_for_startswith():
+    """_streamDisplay must check trimmed.startsWith(open), not raw.startsWith(open)."""
+    fn_idx = MSG_JS.find("function _streamDisplay()")
+    fn_end = MSG_JS.find("\n  }", fn_idx) + 4
+    fn_body = MSG_JS[fn_idx:fn_end]
+    assert "trimmed.startsWith(open)" in fn_body, \
+        "_streamDisplay must use trimmed.startsWith(open) not raw.startsWith(open)"
+
+
+def test_stream_display_partial_tag_uses_trimmed():
+    """The partial-tag guard in _streamDisplay must also use trimmed, not raw."""
+    fn_idx = MSG_JS.find("function _streamDisplay()")
+    fn_end = MSG_JS.find("\n  }", fn_idx) + 4
+    fn_body = MSG_JS[fn_idx:fn_end]
+    assert "open.startsWith(trimmed)" in fn_body, \
+        "Partial-tag guard must use open.startsWith(trimmed) not open.startsWith(raw)"
+
+
+def test_stream_display_trims_return_after_close():
+    """After stripping a completed think block, _streamDisplay must trim leading whitespace from the result."""
+    fn_idx = MSG_JS.find("function _streamDisplay()")
+    fn_end = MSG_JS.find("\n  }", fn_idx) + 4
+    fn_body = MSG_JS[fn_idx:fn_end]
+    # The return after finding close must strip whitespace from the result
+    assert ".replace(/^" in fn_body and "s+/,'')" in fn_body, \
+        "_streamDisplay must strip leading whitespace from content after the closing think tag"
+
+
+# ── Regression: existing anchored patterns must be gone ──────────────────────
+
+def test_no_anchored_think_regex_in_ui_js():
+    """The old anchored regex /^<think>/ must not exist in ui.js."""
+    assert "/^<think>" not in UI_JS, \
+        "Old anchored /^<think>/ regex still present in ui.js — fix not applied"
+
+
+def test_no_anchored_gemma_regex_in_ui_js():
+    """The old anchored Gemma regex must not exist in ui.js."""
+    assert "/^<|channel>" not in UI_JS, \
+        "Old anchored /^<|channel>/ regex still present in ui.js — fix not applied"