fix: record fallback routing metadata

Release MY (v0.51.386): voice mode survives dropped speechSynthesis onend (#3983)

CHANGELOG.md

@@ -3,6 +3,42 @@
 
 ## [Unreleased]
 
+## [v0.51.386] — 2026-06-13 — Release MY (voice mode survives a dropped speechSynthesis onend, #3983)
+
+### Fixed
+
+- **Hands-free voice mode no longer dead-ends after the first browser-TTS reply (#3983).** Chromium intermittently drops the `speechSynthesis` utterance's `onend` event, which left voice mode stuck "speaking" and never re-armed listening. A watchdog now forces a return to listening if `onend` never fires, with the recovery handles cleared on normal completion and on deactivation. The fix is scoped to the browser `speechSynthesis` path — the Edge `Audio` branch (which has a reliable `onended`) is untouched. (#3983)
+
+## [v0.51.385] — 2026-06-13 — Release MX (profile-cookie env var aligned to HERMES_WEBUI_ prefix, #803)
+
+### Changed
+
+- **The profile-cookie name env var now uses the standard `HERMES_WEBUI_` prefix (#803).** Set the per-instance session-profile cookie name via `HERMES_WEBUI_PROFILE_COOKIE_NAME`, matching every other WebUI setting's prefix; the original `WEBUI_PROFILE_COOKIE_NAME` keeps working as a deprecated fallback (warned once per process). Lets multiple WebUI instances on the same host+port disambiguate their profile cookies without env-var-naming surprises. (#803)
+
+## [v0.51.384] — 2026-06-13 — Release MW (no false streaming / activity-timer reset on session switch, #3900)
+
+### Fixed
+
+- **An idle session no longer shows streaming chrome (Stop/spinner/thinking) right after a sidebar switch, and switching back to a live stream no longer resets its activity timer (#3900).** `loadSession` now clears `S.busy` / `S.activeStreamId` as soon as the session metadata confirms there is no `active_stream_id` — before the async message-load gap — so the previous session's busy flag can't bleed onto an idle chat. On switch-away it snapshots the live-turn DOM before replacing the message pane (seeding an `INFLIGHT` bucket if needed) and restores that HTML on the active-stream return path instead of rebuilding the worklog shell from scratch, so the elapsed timer and live trace survive the round-trip. (#3900)
+
+## [v0.51.383] — 2026-06-13 — Release MV (desktop tab title keeps active session name on bot-name refresh, #4086)
+
+### Fixed
+
+- **Desktop tab titles keep the active session name when profile/settings boot paths refresh the assistant name (#4086).** `applyBotName()` now leaves `document.title` alone while a chat session is active, so `syncTopbar()` remains the owner of the per-session `"<session> — <assistant>"` title and desktop tabs no longer collapse to the same fallback name. (#4086)
+
+## [v0.51.382] — 2026-06-13 — Release MU (Stable Assistant Turn Anchors: activity-scene projection, inert, #4093)
+
+### Added
+
+- **Stable Assistant Turn Anchors activity-scene projection (#4093, #3926).** Adds `projectAssistantTurnAnchorActivityScene` to the frozen `HermesAssistantTurnAnchors` surface — a renderer-neutral projection that turns the anchor owner's classified events into ordered activity-scene rows for the future Transparent Stream / Compact Worklog convergence. This slice is **inert**: no render path consumes the scene projection yet (the only live anchor consumer remains the #4092 settled final-answer projection, which still receives a pre-flattened string), so there is zero rendering change in this release. (#4093)
+
+## [v0.51.381] — 2026-06-13 — Release MT (Stable Assistant Turn Anchors: settled final-answer projection, #4092)
+
+### Changed
+
+- **Settled assistant final answers now route through the Stable Assistant Turn Anchor owner (#4092, #3926).** As the first RFC Phase 3 wiring slice, `renderMessages()` derives each *settled* assistant message's final-answer text via `projectAssistantTurnAnchorSettledMessageFinalAnswer` (the anchor registry's settled-message projection) instead of reading the raw content directly. The projection is a faithful identity transform for normal string content (verified by unit echo across plain/markdown/inline-think/unicode/whitespace/code, a real-transcript A/B render that was byte-identical to master, and a live-build `applied:true` echo check), is wrapped in a try/catch that falls back to the original content on any error, and only applies when it produces a usable string — so there is no visible rendering change today; it moves the settled-final derivation onto the single anchor owner that live/replay/settled sources will converge on. Live (`_live`) turns and non-string content are untouched. (#4092)
+
 ## [v0.51.380] — 2026-06-13 — Release MS (tool-iteration-limit stops surfaced explicitly, #3821)
 
 ### Fixed
@@ -247,6 +283,7 @@
 
 - **Worklog details settings now align with the live-to-final model.** The old "Activity expanded by default" setting is renamed to **Worklog details** (default folded), the legacy "Compact tool activity" preference is deprecated, and the Worklog renderer stays enabled for older installs that had saved `simplified_tool_calling=false`. (#3400, #3820)
 
+
 ## [v0.51.346] — 2026-06-09 — Release LJ (PWA notification controls)
 
 ### Added

api/helpers.py

@@ -495,11 +495,36 @@ def read_body(handler) -> dict:
 # ── Profile cookie helpers (issue #798) ─────────────────────────────────────
 
 PROFILE_COOKIE_NAME = 'hermes_profile'
+_PROFILE_COOKIE_ENV = 'HERMES_WEBUI_PROFILE_COOKIE_NAME'
+_LEGACY_PROFILE_COOKIE_ENV = 'WEBUI_PROFILE_COOKIE_NAME'
+_legacy_profile_cookie_warned = False
 
 
 def get_profile_cookie_name() -> str:
-    """Return the cookie name used to persist the active WebUI profile."""
-    return os.getenv('WEBUI_PROFILE_COOKIE_NAME', PROFILE_COOKIE_NAME)
+    """Return the cookie name used to persist the active WebUI profile.
+
+    Honours ``HERMES_WEBUI_PROFILE_COOKIE_NAME`` so multiple WebUI instances
+    sharing a hostname (different ports) can use distinct profile-cookie names
+    instead of trampling each other; browsers scope cookies by host, not
+    host+port (RFC 6265). The original ``WEBUI_PROFILE_COOKIE_NAME`` is still
+    honoured as a deprecated fallback (warned once per process, since this is
+    called on every request).
+    """
+    name = os.getenv(_PROFILE_COOKIE_ENV, '').strip()
+    if name:
+        return name
+    legacy = os.getenv(_LEGACY_PROFILE_COOKIE_ENV, '').strip()
+    if legacy:
+        global _legacy_profile_cookie_warned
+        if not _legacy_profile_cookie_warned:
+            logger.warning(
+                '%s is deprecated; use %s instead.',
+                _LEGACY_PROFILE_COOKIE_ENV,
+                _PROFILE_COOKIE_ENV,
+            )
+            _legacy_profile_cookie_warned = True
+        return legacy
+    return PROFILE_COOKIE_NAME
 
 
 def get_profile_cookie(handler) -> str | None:

api/streaming.py

@@ -7307,6 +7307,27 @@ def _run_agent_streaming(
                     requested_model=resolved_model or model,
                     requested_provider=resolved_provider,
                 )
+                # Synthesize routing metadata from the agent's result when the
+                # hermes fallback chain switched provider/model but didn't
+                # populate llm_gateway_metadata (result carries 'model'/'provider',
+                # not 'used_model'/'used_provider' that _extract_... expects).
+                if not _gateway_routing and isinstance(result, dict):
+                    _result_model = result.get('model') or ''
+                    _result_provider = result.get('provider') or ''
+                    _req_model = resolved_model or model or ''
+                    _req_provider = resolved_provider or ''
+                    if (_result_model and _result_model != _req_model) or \
+                       (_result_provider and _req_provider and _result_provider != _req_provider):
+                        _gateway_routing = _normalize_gateway_routing_metadata(
+                            {
+                                'used_model': _result_model,
+                                'used_provider': _result_provider,
+                                'requested_model': _req_model,
+                                'requested_provider': _req_provider,
+                            },
+                            requested_model=_req_model,
+                            requested_provider=_req_provider,
+                        )
                 if _gateway_routing:
                     s.gateway_routing = _gateway_routing
                     _history = list(getattr(s, 'gateway_routing_history', None) or [])

docs/architecture/stable-assistant-turn-anchor-phase0.md

@@ -21,9 +21,15 @@ streaming or rendering yet.
   anchor seed excludes renderer presentation state, terminal states are exposed
   as constants with alias normalization, and replay + settlement ordering is
   pinned by tests before visible wiring begins.
-- The next independently reviewable boundary is Phase 3 settlement through the
-  anchor owner. `S.messages`, `INFLIGHT`, stream-local state, and DOM nodes remain
-  projection/cache layers until that wiring lands.
+- Slice 4 starts RFC Phase 3 by routing settled assistant final prose through the
+  anchor owner before `renderMessages()` renders the final assistant body.
+- Slice 5 starts RFC Phase 5 by projecting anchor-owned activity events into a
+  renderer-neutral activity scene that Compact Worklog and Transparent Stream
+  can later consume from the same ordered rows.
+- The next independently reviewable boundary is wiring one current renderer to
+  the activity scene. `S.messages`, `INFLIGHT`, stream-local state, and DOM nodes
+  remain projection/cache layers outside the settled final-prose path and the
+  inert activity-scene projection.
 
 ## State Layers
 
@@ -114,6 +120,41 @@ event identity, lifecycle, final answer reference, and activity events.
 until the matching field is explicitly moved. The fallback order is journal
 replay first, settled transcript second, `INFLIGHT` only for gaps.
 
+## Slice 4 Settled Final Projection
+
+`HermesAssistantTurnAnchors.projectAssistantTurnAnchorSettledMessageFinalAnswer()`
+projects one settled assistant transcript message through a local anchor
+registry. The settled transcript message reference remains the semantic
+authority (`content.final_message_ref`); `content.final_answer` is a derived
+render snapshot for the existing markdown pipeline.
+
+`renderMessages()` uses that projection only for settled assistant messages
+(`!isUser && !m._live`) and only after preserving the current content-array
+flattening behavior. It then continues through the existing inline-thinking and
+markdown rendering pipeline. If the anchor helper is unavailable or cannot
+produce a final answer, `renderMessages()` falls back to the existing message
+content path.
+
+This is intentionally narrower than render-scene ownership: live stream tokens,
+replay hydration, worklog rows, transparent-stream rows, tool cards, `INFLIGHT`,
+and DOM continuity are still not consumed by the anchor registry in this slice.
+
+## Slice 5 Activity Scene Projection
+
+`HermesAssistantTurnAnchors.projectAssistantTurnAnchorActivityScene()` projects
+an anchor or registry into `activity_scene_v1`: identity, lifecycle,
+`final_answer`, `final_message_ref`, terminal state, and an ordered
+`activity_rows` list.
+
+The rows are renderer-neutral. Compact Worklog receives display hints such as
+`main_prose`, `collapsed_thinking`, `tool_row`, and `terminal_status_row`.
+Transparent Stream receives the same row IDs, order, kinds, roles, text, tool
+IDs, and sanitized payloads with a chronological display hint. This pins the
+shared input shape before either renderer is rewired.
+
+This slice is still inert. No current UI module consumes the activity scene.
+`renderMessages()` and the live streaming hot path are unchanged by this slice.
+
 ## Source Event Classification
 
 Phase 0 classifies current sources before changing render behavior:

static/assistant_turn_anchors.js

@@ -1,9 +1,9 @@
 // Stable Assistant Turn Anchors scaffold (#3926).
 //
-// This file is intentionally inert: it defines the current ownership inventory,
-// event classifications, and small owner helpers, but it does not register
-// anchors globally or change any renderer. Later phases can wire these helpers into
-// send(), attachLiveStream(), replay hydration, and renderMessages().
+// This file defines the current ownership inventory, event classifications, and
+// small owner helpers. It does not register anchors globally. The only renderer
+// wiring in this slice is settled assistant final-answer projection; live
+// streaming, replay hydration, tools, and DOM ownership remain unwired.
 (function(){
   const ROOT=(typeof window!=='undefined')?window:globalThis;
 
@@ -696,6 +696,352 @@
     });
   }
 
+  function _contextValue(context, keys){
+    return _firstOwn(context&&typeof context==='object'?context:{},keys);
+  }
+
+  function _messageValue(message, keys){
+    return _firstOwn(message&&typeof message==='object'?message:{},keys);
+  }
+
+  function _rawIndexMessageRef(context){
+    const rawIdx=_contextValue(context,['raw_idx','rawIdx']);
+    if(rawIdx===undefined||rawIdx===null||rawIdx==='') return '';
+    return 'raw_idx:'+String(rawIdx);
+  }
+
+  function projectAssistantTurnAnchorSettledMessageFinalAnswer(input, context){
+    const message=(input&&typeof input==='object')?input:{};
+    const ctx=(context&&typeof context==='object')?context:{};
+    const sessionId=_cleanString(_contextValue(ctx,['session_id','sessionId']))
+      ||_cleanString(_messageValue(message,['session_id','sessionId']));
+    if(!sessionId){
+      return Object.freeze({applied:false,reason:'missing_session',final_answer:'',final_message_ref:null,registry:null});
+    }
+    const role=_cleanString(_messageValue(message,['role']))||'assistant';
+    if(role&&role!=='assistant'){
+      return Object.freeze({applied:false,reason:'non_assistant',final_answer:'',final_message_ref:null,registry:null});
+    }
+    const runId=_cleanString(_contextValue(ctx,['run_id','runId']))
+      ||_cleanString(_messageValue(message,['run_id','runId','_run_id','runtime_run_id']));
+    const streamId=_cleanString(_contextValue(ctx,['stream_id','streamId']))
+      ||_cleanString(_messageValue(message,['stream_id','streamId','_stream_id']));
+    const messageRef=_firstTextValue(
+      _messageValue(message,['message_id','id','local_id']),
+      _contextValue(ctx,['message_id','messageId','local_id','localId'])
+    )||_rawIndexMessageRef(ctx);
+    const turnId=_cleanString(_contextValue(ctx,['turn_id','turnId']))
+      ||_cleanString(_messageValue(message,['turn_id','turnId']))
+      ||[
+        'settled',
+        sessionId,
+        runId||streamId||messageRef||'assistant',
+      ].join(':');
+    const registry=createAssistantTurnAnchorRegistry({
+      session_id:sessionId,
+      turn_id:turnId,
+      run_id:runId||null,
+      stream_id:streamId||null,
+      local_id:messageRef||null,
+      source_message_refs:messageRef?[messageRef]:[],
+    });
+    const payload={
+      role:'assistant',
+      id:messageRef||null,
+      content:_hasOwn(ctx,'content')?_own(ctx,'content'):_own(message,'content'),
+    };
+    const usage=_own(message,'usage');
+    const turnUsage=_own(message,'_turnUsage');
+    if(usage&&typeof usage==='object') payload.usage=usage;
+    if(turnUsage&&typeof turnUsage==='object') payload._turnUsage=turnUsage;
+    const result=applyAssistantTurnAnchorSourceEvent(registry,{
+      source_type:'settled_message',
+      payload,
+      local_id:messageRef||null,
+    },{
+      session_id:sessionId,
+      turn_id:turnId,
+      run_id:runId||null,
+      stream_id:streamId||null,
+    });
+    if(!result.applied){
+      return Object.freeze({
+        applied:false,
+        reason:result.reason||null,
+        final_answer:'',
+        final_message_ref:null,
+        registry,
+      });
+    }
+    const rawFinalAnswer=registry.anchor&&registry.anchor.content&&registry.anchor.content.final_answer;
+    const rawFinalMessageRef=registry.anchor&&registry.anchor.content&&registry.anchor.content.final_message_ref;
+    const finalAnswer=typeof rawFinalAnswer==='string'?rawFinalAnswer:'';
+    const finalMessageRef=typeof rawFinalMessageRef==='string'?rawFinalMessageRef:null;
+    return Object.freeze({
+      applied:!!result.applied,
+      reason:result.reason||null,
+      final_answer:finalAnswer,
+      final_message_ref:finalMessageRef,
+      registry,
+    });
+  }
+
+  function _anchorFromProjectionInput(input){
+    if(!input||typeof input!=='object') return null;
+    if(input.anchor&&typeof input.anchor==='object') return input.anchor;
+    if(input.identity&&typeof input.identity==='object') return input;
+    return null;
+  }
+
+  function _activityRowId(event, index){
+    const eventId=_cleanString(_own(event,'event_id'));
+    if(eventId) return eventId;
+    const runId=_cleanString(_own(event,'run_id'));
+    const seq=_own(event,'seq');
+    if(runId&&seq!==undefined&&seq!==null&&seq!=='') return [runId,String(seq)].join(':');
+    const localId=_cleanString(_own(event,'local_id'));
+    if(localId){
+      const sourceType=_cleanString(_own(event,'source_event_type'))||_cleanString(_own(event,'kind'))||'event';
+      return [localId,sourceType,String(index)].join(':');
+    }
+    return 'activity:'+String(index);
+  }
+
+  function _activityRowText(event){
+    const payload=_own(event,'payload')||{};
+    return _firstTextValue(
+      _own(payload,'text'),
+      _own(payload,'content'),
+      _own(payload,'message'),
+      _own(payload,'summary'),
+      _own(payload,'result'),
+      _own(payload,'output')
+    );
+  }
+
+  function _isToolActivityKind(kind){
+    return kind==='tool_started'||kind==='tool_updated'||kind==='tool_completed';
+  }
+
+  function _activityRowToolId(event, kind){
+    if(!_isToolActivityKind(kind)) return null;
+    const payload=_own(event,'payload')||{};
+    return _firstTextValue(
+      _own(payload,'tool_call_id'),
+      _own(payload,'tool_use_id'),
+      _own(payload,'call_id'),
+      _own(payload,'tid'),
+      _own(payload,'id')
+    )||null;
+  }
+
+  function _activityPayloadFirst(payload, keys){
+    return _firstOwn(payload||{},keys);
+  }
+
+  function _activityRowToolDone(kind, status, payload){
+    if(payload&&typeof _own(payload,'done')==='boolean') return _own(payload,'done');
+    if(kind==='tool_completed') return true;
+    if(kind==='tool_started'||kind==='tool_updated') return false;
+    if(status==='completed'||status==='error'||status==='failed') return true;
+    if(status==='running'||status==='pending') return false;
+    return null;
+  }
+
+  function _activityRowToolIsError(status, payload){
+    if(payload&&typeof _own(payload,'is_error')==='boolean') return _own(payload,'is_error');
+    const raw=_cleanString(status).toLowerCase();
+    if(raw==='error'||raw==='failed'||raw==='failure') return true;
+    return false;
+  }
+
+  function _activityRowGroup(event, payload, index){
+    const activitySegmentSeq=_activityPayloadFirst(payload,['activitySegmentSeq','activity_segment_seq','segmentSeq','segment_seq']);
+    const activityBurstId=_activityPayloadFirst(payload,['activityBurstId','activity_burst_id','burstId','burst_id']);
+    const assistantMsgIdx=_activityPayloadFirst(payload,['assistant_msg_idx','assistantMessageIndex','assistant_msg_index']);
+    const cleanSegment=activitySegmentSeq!==undefined&&activitySegmentSeq!==null&&String(activitySegmentSeq)!==''
+      ? activitySegmentSeq
+      : null;
+    const cleanBurst=activityBurstId!==undefined&&activityBurstId!==null&&String(activityBurstId)!==''
+      ? activityBurstId
+      : null;
+    const cleanAssistant=assistantMsgIdx!==undefined&&assistantMsgIdx!==null&&String(assistantMsgIdx)!==''
+      ? assistantMsgIdx
+      : null;
+    const fallbackSeq=_own(event,'seq');
+    const fallbackKey=fallbackSeq!==undefined&&fallbackSeq!==null&&fallbackSeq!==''?`event:${String(fallbackSeq)}`:`activity:${String(index)}`;
+    const groupKey=cleanSegment!==null
+      ? `segment:${String(cleanSegment)}`
+      : cleanBurst!==null
+        ? `burst:${String(cleanBurst)}`
+        : cleanAssistant!==null
+          ? `assistant:${String(cleanAssistant)}`
+          : fallbackKey;
+    return Object.freeze({
+      group_key:groupKey,
+      activity_burst_id:cleanBurst,
+      activity_segment_seq:cleanSegment,
+      assistant_msg_idx:cleanAssistant,
+    });
+  }
+
+  function _activityRowThinking(event, kind, text){
+    if(kind!=='reasoning') return null;
+    const payload=_own(event,'payload')||{};
+    const thinkingText=_firstTextValue(
+      _own(payload,'thinking'),
+      _own(payload,'reasoning'),
+      _own(payload,'text'),
+      text
+    );
+    const preview=thinkingText?String(thinkingText).replace(/\s+/g,' ').trim():'';
+    return Object.freeze({
+      text:thinkingText||'',
+      preview:preview.length>180?`${preview.slice(0,177)}...`:preview,
+      dedupe_key:preview?`thinking:${preview.toLowerCase()}`:'',
+    });
+  }
+
+  function _activityRowTool(event, kind, status, text, toolCallId){
+    if(!_isToolActivityKind(kind)) return null;
+    const payload=_own(event,'payload')||{};
+    const toolName=_cleanString(
+      _activityPayloadFirst(payload,['name','tool_name','function_name'])||
+      (_own(payload,'function')&&_own(_own(payload,'function'),'name'))
+    )||'tool';
+    const args=_activityPayloadFirst(payload,['args','arguments','input','params']);
+    const preview=_firstTextValue(
+      _own(payload,'preview'),
+      _own(payload,'summary'),
+      text
+    );
+    const snippet=_firstTextValue(
+      _own(payload,'snippet'),
+      _own(payload,'result'),
+      _own(payload,'output')
+    );
+    const done=_activityRowToolDone(kind,status,payload);
+    const isError=_activityRowToolIsError(status,payload);
+    const signatureParts=[
+      toolName,
+      toolCallId||'',
+      JSON.stringify(_sanitizePayload(args||{})),
+    ];
+    return Object.freeze({
+      id:toolCallId,
+      name:toolName,
+      args:_sanitizePayload(args||{}),
+      preview:preview||'',
+      snippet:snippet||'',
+      result:_sanitizePayload(_own(payload,'result'))??null,
+      output:_sanitizePayload(_own(payload,'output'))??null,
+      done,
+      is_error:isError,
+      duration:_activityPayloadFirst(payload,['duration','duration_seconds','elapsed'])??null,
+      started_at:_activityPayloadFirst(payload,['started_at','startedAt'])??null,
+      signature:signatureParts.join('|'),
+    });
+  }
+
+  function _activityRowRole(kind){
+    if(kind==='process_prose') return 'prose';
+    if(kind==='reasoning') return 'thinking';
+    if(_isToolActivityKind(kind)) return 'tool';
+    if(kind==='lifecycle_status') return 'lifecycle';
+    if(kind==='control_boundary') return 'control';
+    if(kind==='terminal_status') return 'terminal';
+    return 'activity';
+  }
+
+  function _activityRowDisplayHint(kind, mode){
+    if(mode==='transparent_stream') return 'chronological_activity';
+    if(kind==='process_prose') return 'main_prose';
+    if(kind==='reasoning') return 'collapsed_thinking';
+    if(_isToolActivityKind(kind)) return 'tool_row';
+    if(kind==='lifecycle_status') return 'quiet_lifecycle_row';
+    if(kind==='control_boundary') return 'control_boundary_row';
+    if(kind==='terminal_status') return 'terminal_status_row';
+    return 'activity_row';
+  }
+
+  function _activityRowDisplayHints(kind){
+    return Object.freeze({
+      compact_worklog:_activityRowDisplayHint(kind,'compact_worklog'),
+      transparent_stream:_activityRowDisplayHint(kind,'transparent_stream'),
+    });
+  }
+
+  function _activitySceneRow(event, index, mode){
+    const payload=_own(event,'payload');
+    const kind=_cleanString(_own(event,'kind'))||'activity';
+    const status=_cleanString(_own(event,'status'))||null;
+    const text=_activityRowText(event);
+    const toolCallId=_activityRowToolId(event,kind);
+    const sanitizedPayload=_sanitizePayload(payload);
+    return Object.freeze({
+      row_id:_activityRowId(event,index),
+      order_index:index,
+      kind,
+      role:_activityRowRole(kind),
+      display_hint:_activityRowDisplayHint(kind,mode),
+      display_hints:_activityRowDisplayHints(kind),
+      source_event_type:_cleanString(_own(event,'source_event_type'))||null,
+      event_id:_cleanString(_own(event,'event_id'))||null,
+      local_id:_cleanString(_own(event,'local_id'))||null,
+      run_id:_cleanString(_own(event,'run_id'))||null,
+      stream_id:_cleanString(_own(event,'stream_id'))||null,
+      seq:_own(event,'seq')??null,
+      status,
+      created_at:_own(event,'created_at')??null,
+      identity:Object.freeze({
+        event_id:_cleanString(_own(event,'event_id'))||null,
+        local_id:_cleanString(_own(event,'local_id'))||null,
+        run_id:_cleanString(_own(event,'run_id'))||null,
+        stream_id:_cleanString(_own(event,'stream_id'))||null,
+        seq:_own(event,'seq')??null,
+      }),
+      group:_activityRowGroup(event,payload||{},index),
+      text,
+      thinking:_activityRowThinking(event,kind,text),
+      tool_call_id:toolCallId,
+      tool:_activityRowTool(event,kind,status,text,toolCallId),
+      payload:sanitizedPayload,
+    });
+  }
+
+  function projectAssistantTurnAnchorActivityScene(input, options){
+    const anchor=_anchorFromProjectionInput(input);
+    const opts=(options&&typeof options==='object')?options:{};
+    const requestedMode=_cleanString(_own(opts,'mode'));
+    const mode=requestedMode==='transparent_stream'?'transparent_stream':'compact_worklog';
+    if(!anchor){
+      return Object.freeze({
+        version:'activity_scene_v1',
+        mode,
+        identity:Object.freeze({source_message_refs:Object.freeze([])}),
+        lifecycle:Object.freeze({}),
+        final_answer:'',
+        final_message_ref:null,
+        terminal_state:null,
+        activity_rows:Object.freeze([]),
+      });
+    }
+    const rows=(Array.isArray(anchor.activity_events)?anchor.activity_events:[])
+      .map((event,index)=>_activitySceneRow(event,index,mode));
+    const lifecycle=_copyObject(anchor.lifecycle);
+    const content=anchor.content&&typeof anchor.content==='object'?anchor.content:{};
+    return Object.freeze({
+      version:'activity_scene_v1',
+      mode,
+      identity:_frozenIdentityCopy(anchor.identity||{}),
+      lifecycle:Object.freeze(lifecycle),
+      final_answer:typeof content.final_answer==='string'?content.final_answer:'',
+      final_message_ref:typeof content.final_message_ref==='string'?content.final_message_ref:null,
+      terminal_state:_cleanString(_own(lifecycle,'terminal_state'))||null,
+      activity_rows:Object.freeze(rows),
+    });
+  }
+
   function createAssistantTurnAnchorSeed(input){
     const opts=(input&&typeof input==='object')?input:{};
     const sessionId=_cleanString(opts.session_id);
@@ -755,7 +1101,7 @@
   }
 
   ROOT.HermesAssistantTurnAnchors=Object.freeze({
-    version:'slice3-registry-shadow',
+    version:'slice5-activity-scene',
     activityEventKinds:ACTIVITY_EVENT_KINDS,
     stateLayers:STATE_LAYERS,
     sourceEventClassification:SOURCE_EVENT_CLASSIFICATION,
@@ -772,6 +1118,8 @@
     applyAssistantTurnAnchorSourceEvent,
     applyAssistantTurnAnchorSourceEvents,
     createAssistantTurnAnchorShadowSnapshot,
+    projectAssistantTurnAnchorSettledMessageFinalAnswer,
+    projectAssistantTurnAnchorActivityScene,
     isAssistantTurnAnchorActivityKind,
   });
 })();

static/boot.js

@@ -853,8 +853,48 @@ window._micPendingSend=window._micPendingSend||false;
   // a different session's last assistant reply if the user navigated away
   // between send and stream completion. (Opus pre-release advisor.)
   let _voiceModeThinkingSid=null;
+  let _browserTtsKeepAlive=null;
+  let _browserTtsWatchdog=null;
+  let _browserTtsSuppressNextErrorRearm=false;
   const SILENCE_MS=1800; // auto-send after 1.8s silence
 
+  function _clearBrowserTtsRecovery(){
+    if(_browserTtsKeepAlive){
+      clearInterval(_browserTtsKeepAlive);
+      _browserTtsKeepAlive=null;
+    }
+    if(_browserTtsWatchdog){
+      clearTimeout(_browserTtsWatchdog);
+      _browserTtsWatchdog=null;
+    }
+  }
+
+  function _armBrowserTtsRecovery(clean, rate){
+    _clearBrowserTtsRecovery();
+    _browserTtsSuppressNextErrorRearm=false;
+    const safeRate=(Number.isFinite(rate)&&rate>0)?rate:1;
+    // Chromium can drop utter.onend on later turns, so force a recovery path.
+    const watchdogMs=Math.max(4000,Math.round((String(clean||'').length/(12*safeRate))*1000)+10000);
+    _browserTtsWatchdog=setTimeout(()=>{
+      if(!_voiceModeActive||_voiceModeState!=='speaking') return;
+      _browserTtsSuppressNextErrorRearm=true;
+      try{ speechSynthesis.cancel(); }catch(_){}
+      _clearBrowserTtsRecovery();
+      _startListening();
+    },watchdogMs);
+    _browserTtsKeepAlive=setInterval(()=>{
+      if(!_voiceModeActive||_voiceModeState!=='speaking'){
+        _clearBrowserTtsRecovery();
+        return;
+      }
+      if(!speechSynthesis.speaking) return;
+      try{
+        speechSynthesis.pause();
+        speechSynthesis.resume();
+      }catch(_){}
+    },10000);
+  }
+
   function _setState(state){
     _voiceModeState=state;
     indicator.className='voice-mode-indicator '+state;
@@ -867,6 +907,7 @@ window._micPendingSend=window._micPendingSend||false;
 
   function _startListening(){
     if(!_voiceModeActive) return;
+    _clearBrowserTtsRecovery();
     _setState('listening');
 
     _recognition=new SpeechRecognition();
@@ -1057,14 +1098,27 @@ window._micPendingSend=window._micPendingSend||false;
     if(!isNaN(savedPitch)) utter.pitch=Math.min(2,Math.max(0,savedPitch));
 
     utter.onend=()=>{
+      _browserTtsSuppressNextErrorRearm=false;
+      _clearBrowserTtsRecovery();
       // After speaking, go back to listening
-      if(_voiceModeActive) setTimeout(()=>_startListening(),500);
+      if(_voiceModeActive&&_voiceModeState==='speaking') setTimeout(()=>_startListening(),500);
     };
     utter.onerror=()=>{
+      _clearBrowserTtsRecovery();
+      if(_browserTtsSuppressNextErrorRearm){
+        _browserTtsSuppressNextErrorRearm=false;
+        return;
+      }
       if(_voiceModeActive) setTimeout(()=>_startListening(),1000);
     };
 
-    speechSynthesis.speak(utter);
+    _armBrowserTtsRecovery(clean, utter.rate);
+    try{
+      speechSynthesis.speak(utter);
+    }catch(_){
+      _clearBrowserTtsRecovery();
+      if(_voiceModeActive) setTimeout(()=>_startListening(),1000);
+    }
   }
 
   // Hook into response completion — observe when the agent finishes
@@ -1121,10 +1175,12 @@ window._micPendingSend=window._micPendingSend||false;
     _voiceModeActive=false;
     _voiceModeState='idle';
     _voiceModeThinkingSid=null;
+    _browserTtsSuppressNextErrorRearm=false;
     modeBtn.classList.remove('active');
     _setButtonTooltip(modeBtn, t('voice_mode_toggle'));
     bar.style.display='none';
     clearTimeout(_silenceTimer);
+    _clearBrowserTtsRecovery();
     try{ if(_recognition) _recognition.abort(); }catch(_){}
     _recognition=null;
     if(typeof stopTTS==='function') stopTTS();
@@ -1761,7 +1817,7 @@ function applyBotName(){
   // The saved assistant name applies to the default profile only.
   // Non-default profiles use their own profile names.
   const name=assistantDisplayName();
-  document.title=name;
+  if(!S.session) document.title=name;
   const sidebarH1=document.querySelector('.sidebar-header h1');
   if(sidebarH1) sidebarH1.textContent=name;
   const logo=document.querySelector('.sidebar-header .logo');

static/sessions.js

@@ -878,6 +878,22 @@ async function loadSession(sid){
     // close streams for the session the user actually landed on (#1060 guard,
     // extended to cover the new pre-switch await).
     if (_loadingSessionId !== sid) return;
+    // Snapshot the live turn before msgInner is replaced. Preserves the activity
+    // timer, partial response, and tool cards so switching back does not rebuild
+    // the stream UI from scratch.
+    if(
+      (S.busy||S.activeStreamId||(INFLIGHT&&INFLIGHT[currentSid]))&&
+      typeof snapshotLiveTurnHtmlForSession==='function'
+    ){
+      if(!INFLIGHT[currentSid]){
+        INFLIGHT[currentSid]={
+          messages:Array.isArray(S.messages)?[...S.messages]:[],
+          uploaded:[],
+          toolCalls:Array.isArray(S.toolCalls)?[...S.toolCalls]:[],
+        };
+      }
+      snapshotLiveTurnHtmlForSession(currentSid);
+    }
   }
   if (currentSid !== sid || forceReload) {
     // #3306: When force-reloading the currently-active session (e.g. external
@@ -1040,14 +1056,21 @@ async function loadSession(sid){
   if(typeof startSessionStream==='function') startSessionStream(S.session.session_id);
 
   const activeStreamId=S.session.active_stream_id||null;
-  // If the server says the session is idle, discard any browser-side inflight
-  // cache left behind by a crashed/restarted stream. Otherwise the UI can keep
-  // showing a permanent thinking/running state even though active_streams=0.
-  if(!activeStreamId&&INFLIGHT[sid]){
-    delete INFLIGHT[sid];
-    if(typeof clearInflightState==='function') clearInflightState(sid);
+  // If the server says the session is idle, reset browser-side streaming flags
+  // NOW — before the async _ensureMessagesLoaded gap below. Without this,
+  // S.busy can remain true from a still-running stream in the PREVIOUS session
+  // while S.session.session_id has already advanced to the new one.
+  // _isSessionLocallyStreaming() checks (isActive && S.busy), so during the
+  // async window the new session would appear locally-streaming (sidebar spinner,
+  // Stop button, thinking state on an idle chat). Also clears stale INFLIGHT
+  // entries left behind by a crashed/restarted stream.
+  if(!activeStreamId){
     S.activeStreamId=null;
     S.busy=false;
+    if(INFLIGHT[sid]){
+      delete INFLIGHT[sid];
+      if(typeof clearInflightState==='function') clearInflightState(sid);
+    }
   }
 
   function _mergePendingSessionMessage(session,messages){
@@ -1262,10 +1285,15 @@ async function loadSession(sid){
       updateSendBtn();
       setStatus('');
       setComposerStatus('');
-      // syncTopbar();renderMessages();appendThinking();loadDir('.');
       syncTopbar();renderMessages(sameSessionForceReload?{preserveScroll:true}:undefined);
-      if(typeof ensureLiveWorklogShell==='function') ensureLiveWorklogShell();
-      else appendThinking();
+      let restoredLiveTurn=false;
+      if(typeof restoreLiveTurnHtmlForSession==='function'){
+        restoredLiveTurn=restoreLiveTurnHtmlForSession(sid);
+      }
+      if(!restoredLiveTurn){
+        if(typeof ensureLiveWorklogShell==='function') ensureLiveWorklogShell();
+        else appendThinking();
+      }
       loadDir('.');
       updateQueueBadge(sid);
       startApprovalPolling(sid);

static/ui.js

@@ -8747,6 +8747,26 @@ function _renderMessagesWithScrollSnapshot(options){
   renderMessages({...(options||{}),preserveScroll:true});
   _restoreMessageScrollSnapshotSameFrame(scrollSnapshot);
 }
+let _assistantTurnAnchorSettledFinalAnswerWarned=false;
+function _assistantTurnAnchorSettledFinalAnswer(message, content, context){
+  try{
+    const api=(typeof window!=='undefined')?window.HermesAssistantTurnAnchors:null;
+    if(!api||typeof api.projectAssistantTurnAnchorSettledMessageFinalAnswer!=='function') return null;
+    const result=api.projectAssistantTurnAnchorSettledMessageFinalAnswer(message,{
+      session_id:context&&context.session_id,
+      raw_idx:context&&context.raw_idx,
+      content,
+    });
+    const finalAnswer=result&&typeof result.final_answer==='string'?result.final_answer:'';
+    return finalAnswer?finalAnswer:null;
+  }catch(err){
+    if(!_assistantTurnAnchorSettledFinalAnswerWarned&&typeof console!=='undefined'&&console.warn){
+      _assistantTurnAnchorSettledFinalAnswerWarned=true;
+      console.warn('assistant turn anchor settled-final projection failed',err);
+    }
+    return null;
+  }
+}
 function _scrollAfterMessageRender(preserveScroll, scrollSnapshot){
   // Terminal stream renders can happen after S.activeStreamId is cleared.
   // In that case, preserveScroll asks the normal pin-state helper to decide:
@@ -9077,6 +9097,13 @@ function renderMessages(options){
     if(Array.isArray(content)){
       content=content.filter(p=>p&&p.type==='text').map(p=>p.text||p.content||'').join('\n');
     }
+    if(m.role==='assistant'&&!m._live&&typeof content==='string'){
+      const anchorFinal=_assistantTurnAnchorSettledFinalAnswer(m, content, {
+        session_id:sid,
+        raw_idx:rawIdx,
+      });
+      if(anchorFinal!==null) content=anchorFinal;
+    }
     if(typeof content==='string'){
       if(typeof window!=='undefined'&&typeof window._extractInlineThinkingFromContentForRender==='function'){
         const split=window._extractInlineThinkingFromContentForRender(content, thinkingText);

tests/test_inflight_stream_reuse.py

@@ -254,7 +254,10 @@ def test_load_session_reattaches_when_inflight_is_in_memory_and_marked_for_reatt
     pins the gate's shape so future refactors don't drop the flag check.
     """
     body = _function_body(SESSIONS_JS, "loadSession")
-    inflight_idx = body.find("if(INFLIGHT[sid]){")
+    # Anchor on the Phase-2 INFLIGHT restore branch (the later occurrence): #3899
+    # added an earlier if(INFLIGHT[sid]){ idle-reset block, so .find() would grab
+    # the wrong one. rfind = the substantive restore branch.
+    inflight_idx = body.rfind("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
     inflight_block = body[inflight_idx : inflight_idx + 4200]
     assert "INFLIGHT[sid].reattach" in inflight_block, (
@@ -283,9 +286,17 @@ def test_load_session_attaches_sse_before_auxiliary_work():
     active_branch = body[body.find("if(activeStreamId){") : body.find("}else{", body.find("if(activeStreamId){"))]
     active_attach = active_branch.find("attachLiveStream(sid, activeStreamId")
     assert active_attach != -1
+    # #3899 inserted restoreLiveTurnHtmlForSession between renderMessages and
+    # appendThinking, and renderMessages now takes a preserveScroll arg — so the
+    # old contiguous "syncTopbar();renderMessages();appendThinking();loadDir('.');"
+    # literal no longer exists. Assert each auxiliary call individually; all must
+    # still run AFTER attachLiveStream (the invariant this test protects).
     for marker in (
         "updateSendBtn();",
-        "syncTopbar();renderMessages();appendThinking();loadDir('.');",
+        "syncTopbar();",
+        "renderMessages(",
+        "appendThinking();",
+        "loadDir('.');",
         "updateQueueBadge(sid);",
         "startApprovalPolling(sid)",
     ):
@@ -1013,7 +1024,9 @@ def test_load_session_discards_cursor_only_inflight_before_reattach():
     guard = "if(activeStreamId&&INFLIGHT[sid]&&!_inflightHasVisibleLiveState(INFLIGHT[sid]))"
     assert guard in compact_load
     guard_pos = compact_load.find(guard)
-    inflight_branch_pos = compact_load.find("if(INFLIGHT[sid]){")
+    # rfind: anchor on the Phase-2 restore branch, not #3899's earlier idle-reset
+    # if(INFLIGHT[sid]){ block (which now precedes the guard).
+    inflight_branch_pos = compact_load.rfind("if(INFLIGHT[sid]){")
     assert 0 <= guard_pos < inflight_branch_pos
 
 

tests/test_issue3306_loadsession_carry_forward.py

@@ -26,7 +26,10 @@ SESSIONS_JS = (REPO / "static" / "sessions.js").read_text(encoding="utf-8")
 def _load_session_clear_block() -> str:
     """The if(currentSid!==sid||forceReload){...} block in loadSession()."""
     start = SESSIONS_JS.index("async function loadSession(sid)")
-    return SESSIONS_JS[start: start + 4000]
+    # Window widened to 6500: #3899's idle-reset + live-turn-snapshot blocks added
+    # code earlier in loadSession, pushing the carry-forward snapshot past the old
+    # 4000-char window.
+    return SESSIONS_JS[start: start + 6500]
 
 
 def _ensure_messages_loaded_body() -> str:

tests/test_issue3983_browser_tts_watchdog.py

@@ -0,0 +1,82 @@
+from pathlib import Path
+import re
+
+
+REPO = Path(__file__).resolve().parents[1]
+
+
+def _extract_function(src: str, name: str) -> str:
+    anchor = f"function {name}("
+    start = src.find(anchor)
+    assert start != -1, f"{name}() must exist"
+    body_start = src.find("{", start)
+    assert body_start != -1, f"{name}() must have a body"
+    depth = 1
+    idx = body_start + 1
+    while depth and idx < len(src):
+        if src[idx] == "{":
+            depth += 1
+        elif src[idx] == "}":
+            depth -= 1
+        idx += 1
+    assert depth == 0, f"{name}() body must balance braces"
+    return src[start:idx]
+
+
+def test_boot_js_declares_browser_tts_recovery_helpers():
+    src = (REPO / "static" / "boot.js").read_text(encoding="utf-8")
+    assert "let _browserTtsKeepAlive=null;" in src
+    assert "let _browserTtsWatchdog=null;" in src
+    assert "let _browserTtsSuppressNextErrorRearm=false;" in src
+    assert "function _clearBrowserTtsRecovery()" in src
+    assert "function _armBrowserTtsRecovery(clean, rate)" in src
+
+
+def test_browser_tts_watchdog_rearms_listening_if_onend_drops():
+    src = (REPO / "static" / "boot.js").read_text(encoding="utf-8")
+    arm_body = _extract_function(src, "_armBrowserTtsRecovery")
+    assert "_browserTtsWatchdog=setTimeout" in arm_body
+    assert "_voiceModeState!=='speaking'" in arm_body
+    assert "_browserTtsSuppressNextErrorRearm=true;" in arm_body
+    assert "speechSynthesis.cancel()" in arm_body
+    assert "_startListening();" in arm_body
+    assert "_browserTtsKeepAlive=setInterval" in arm_body
+    assert "speechSynthesis.pause();" in arm_body
+    assert "speechSynthesis.resume();" in arm_body
+
+
+def test_browser_tts_callbacks_and_deactivate_clear_recovery_handles():
+    src = (REPO / "static" / "boot.js").read_text(encoding="utf-8")
+    speak_body = _extract_function(src, "_speakResponse")
+    assert "const utter=new SpeechSynthesisUtterance(clean);" in speak_body
+    assert "utter.onend=()=>{" in speak_body
+    assert "utter.onerror=()=>{" in speak_body
+    assert speak_body.count("_clearBrowserTtsRecovery();") >= 2, (
+        "Both browser TTS completion callbacks must clear watchdog/keep-alive handles."
+    )
+    assert "_browserTtsSuppressNextErrorRearm=false;" in speak_body
+    assert "_voiceModeActive&&_voiceModeState==='speaking'" in speak_body
+    assert "if(_browserTtsSuppressNextErrorRearm){" in speak_body
+    assert "_armBrowserTtsRecovery(clean, utter.rate);" in speak_body
+
+    deactivate_body = _extract_function(src, "_deactivate")
+    assert "_clearBrowserTtsRecovery();" in deactivate_body, (
+        "_deactivate() must clear browser TTS watchdog/keep-alive handles."
+    )
+    assert "_browserTtsSuppressNextErrorRearm=false;" in deactivate_body
+
+
+def test_edge_audio_branch_stays_separate():
+    src = (REPO / "static" / "boot.js").read_text(encoding="utf-8")
+    edge_match = re.search(
+        r'if\(engine==="edge"\)\{(.*?)\n\s+return;\n\s+\}',
+        src,
+        re.DOTALL,
+    )
+    assert edge_match, "Edge audio branch must exist"
+    edge_body = edge_match.group(1)
+    assert "const audio = new Audio(url);" in edge_body
+    assert "audio.onended = () => {" in edge_body
+    assert "_armBrowserTtsRecovery" not in edge_body, (
+        "The browser speechSynthesis workaround must not be injected into the Edge audio branch."
+    )

tests/test_issue4086_document_title_owner.py

@@ -0,0 +1,40 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+BOOT_JS = ROOT / "static" / "boot.js"
+UI_JS = ROOT / "static" / "ui.js"
+
+
+def _extract_function(src: str, signature: str) -> str:
+    start = src.find(signature)
+    assert start != -1, f"{signature} not found"
+    depth = 0
+    for idx in range(start, len(src)):
+        ch = src[idx]
+        if ch == "{":
+            depth += 1
+        elif ch == "}":
+            depth -= 1
+            if depth == 0:
+                return src[start : idx + 1]
+    raise AssertionError(f"{signature} body did not terminate")
+
+
+def test_apply_bot_name_does_not_overwrite_active_session_document_title():
+    """Session titles belong to syncTopbar() while a chat session is active."""
+    src = BOOT_JS.read_text()
+    body = _extract_function(src, "function applyBotName(){")
+
+    assert "if(!S.session) document.title=name;" in body
+    assert "document.title=name;" not in body.replace(
+        "if(!S.session) document.title=name;",
+        "",
+    )
+
+
+def test_sync_topbar_remains_session_document_title_owner():
+    src = UI_JS.read_text()
+    body = _extract_function(src, "function syncTopbar(){")
+
+    assert "document.title=sessionTitle+' \\u2014 '+assistantDisplayName();" in body

tests/test_issue803.py

@@ -13,6 +13,7 @@ Covers:
   4. switch_profile(process_wide=False) does NOT mutate process globals
   5. Concurrent requests on different threads see independent profiles
 """
+import logging
 import os
 import threading
 from pathlib import Path
@@ -230,6 +231,60 @@ class TestProfileCookieHelpers:
         assert get_profile_cookie(handler) is None
 
 
+# ── 1b. Profile cookie name resolution (env > legacy env > default) ───────────
+
+class TestProfileCookieNameResolution:
+
+    def test_default_when_unset(self, monkeypatch):
+        from api.helpers import PROFILE_COOKIE_NAME, get_profile_cookie_name
+        monkeypatch.delenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', raising=False)
+        monkeypatch.delenv('WEBUI_PROFILE_COOKIE_NAME', raising=False)
+        assert get_profile_cookie_name() == PROFILE_COOKIE_NAME
+
+    def test_canonical_env_overrides_default(self, monkeypatch):
+        from api.helpers import get_profile_cookie_name
+        monkeypatch.delenv('WEBUI_PROFILE_COOKIE_NAME', raising=False)
+        monkeypatch.setenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', 'hermes_profile_alt')
+        assert get_profile_cookie_name() == 'hermes_profile_alt'
+
+    def test_legacy_env_still_honoured(self, monkeypatch):
+        from api.helpers import get_profile_cookie_name
+        monkeypatch.delenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', raising=False)
+        monkeypatch.setenv('WEBUI_PROFILE_COOKIE_NAME', 'hermes_profile_legacy')
+        assert get_profile_cookie_name() == 'hermes_profile_legacy'
+
+    def test_canonical_takes_precedence_over_legacy(self, monkeypatch):
+        from api.helpers import get_profile_cookie_name
+        monkeypatch.setenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', 'canonical')
+        monkeypatch.setenv('WEBUI_PROFILE_COOKIE_NAME', 'legacy')
+        assert get_profile_cookie_name() == 'canonical'
+
+    def test_blank_canonical_falls_back_to_legacy(self, monkeypatch):
+        from api.helpers import get_profile_cookie_name
+        monkeypatch.setenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', '   ')
+        monkeypatch.setenv('WEBUI_PROFILE_COOKIE_NAME', 'hermes_profile_legacy')
+        assert get_profile_cookie_name() == 'hermes_profile_legacy'
+
+    def test_blank_envs_fall_back_to_default(self, monkeypatch):
+        from api.helpers import PROFILE_COOKIE_NAME, get_profile_cookie_name
+        monkeypatch.setenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', '   ')
+        monkeypatch.setenv('WEBUI_PROFILE_COOKIE_NAME', '')
+        assert get_profile_cookie_name() == PROFILE_COOKIE_NAME
+
+    def test_legacy_deprecation_warns_only_once(self, monkeypatch, caplog):
+        # get_profile_cookie_name() runs on every request, so the deprecation
+        # warning for the legacy env var must be emitted once per process.
+        import api.helpers as helpers
+        monkeypatch.delenv('HERMES_WEBUI_PROFILE_COOKIE_NAME', raising=False)
+        monkeypatch.setenv('WEBUI_PROFILE_COOKIE_NAME', 'hermes_profile_legacy')
+        monkeypatch.setattr(helpers, '_legacy_profile_cookie_warned', False)
+        with caplog.at_level(logging.WARNING, logger='api.helpers'):
+            for _ in range(3):
+                assert helpers.get_profile_cookie_name() == 'hermes_profile_legacy'
+        warned = [r for r in caplog.records if 'deprecated' in r.getMessage()]
+        assert len(warned) == 1
+
+
 # ── 2. Thread-local request context ──────────────────────────────────────────
 
 class TestThreadLocalProfileContext:

tests/test_issue_new_chat_draft_restore.py

@@ -76,7 +76,9 @@ def test_pre_switch_draft_flush_rechecks_stale_loading_guard():
     (Codex pre-release CORE catch, #3471)."""
     start = SESSIONS_JS.find("async function loadSession(")
     assert start != -1, "loadSession not found"
-    body = SESSIONS_JS[start:start + 4000]
+    # Window widened to 6500: #3899's idle-reset + live-turn-snapshot blocks pushed
+    # the destructive S.messages clear past the old 4000-char window.
+    body = SESSIONS_JS[start:start + 6500]
     await_idx = body.find("await _saveComposerDraftNow(currentSid")
     guard_idx = body.find("if (_loadingSessionId !== sid) return;", await_idx)
     clear_idx = body.find("S.messages = [];", await_idx)

tests/test_regressions.py

@@ -426,7 +426,10 @@ def test_loadSession_inflight_restores_live_tool_cards(cleanup_test_sessions):
     """
     src = (REPO_ROOT / "static/sessions.js").read_text()
     # INFLIGHT branch must call appendLiveToolCard
-    inflight_idx = src.find("if(INFLIGHT[sid]){")
+    # Anchor on the Phase-2 INFLIGHT restore branch (the later occurrence); #3899
+    # added an earlier if(INFLIGHT[sid]){ idle-reset block, so .find() would
+    # grab the wrong one. (rfind = the substantive restore branch.)
+    inflight_idx = src.rfind("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
     inflight_block = src[inflight_idx:inflight_idx+4200]
     assert "appendLiveToolCard" in inflight_block,         "loadSession INFLIGHT branch must restore live tool cards via appendLiveToolCard"
@@ -647,7 +650,10 @@ def test_loadSession_inflight_sets_busy_before_renderMessages(cleanup_test_sessi
     session switch.
     """
     src = (REPO_ROOT / "static/sessions.js").read_text()
-    inflight_idx = src.find("if(INFLIGHT[sid]){")
+    # Anchor on the Phase-2 INFLIGHT restore branch (the later occurrence); #3899
+    # added an earlier if(INFLIGHT[sid]){ idle-reset block, so .find() would
+    # grab the wrong one. (rfind = the substantive restore branch.)
+    inflight_idx = src.rfind("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
     inflight_block = src[inflight_idx:inflight_idx+4200]
     busy_pos = inflight_block.find("S.busy=true;")
@@ -662,7 +668,10 @@ def test_loadSession_inflight_sets_busy_before_renderMessages(cleanup_test_sessi
 
 def test_loadSession_inflight_merges_tail_with_persisted_transcript(cleanup_test_sessions):
     src = (REPO_ROOT / "static/sessions.js").read_text()
-    inflight_idx = src.find("if(INFLIGHT[sid]){")
+    # Anchor on the Phase-2 INFLIGHT restore branch (the later occurrence); #3899
+    # added an earlier if(INFLIGHT[sid]){ idle-reset block, so .find() would
+    # grab the wrong one. (rfind = the substantive restore branch.)
+    inflight_idx = src.rfind("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
     inflight_block = src[inflight_idx:inflight_idx+1200]
 
@@ -756,7 +765,10 @@ def test_loadSession_inflight_sets_active_stream_before_replaying_live_tool_card
     counter drops the previously-seen tools after a focus change.
     """
     src = (REPO_ROOT / "static/sessions.js").read_text()
-    inflight_idx = src.find("if(INFLIGHT[sid]){")
+    # Anchor on the Phase-2 INFLIGHT restore branch (the later occurrence); #3899
+    # added an earlier if(INFLIGHT[sid]){ idle-reset block, so .find() would
+    # grab the wrong one. (rfind = the substantive restore branch.)
+    inflight_idx = src.rfind("if(INFLIGHT[sid]){")
     assert inflight_idx >= 0, "INFLIGHT branch not found in loadSession"
     inflight_block = src[inflight_idx:inflight_idx+4200]
     active_pos = inflight_block.find("S.activeStreamId=activeStreamId;")

tests/test_session_switch_busy_race.py

@@ -0,0 +1,87 @@
+"""Regression coverage for session-switch busy-state race and live-turn restore.
+
+Switching from a streaming session to an idle one must clear S.busy before the
+async _ensureMessagesLoaded gap. Otherwise _isSessionLocallyStreaming() treats
+the newly opened session as locally streaming while messages are still loading.
+
+Switching back to a streaming session must restore the snapshotted live turn
+instead of rebuilding thinking/worklog chrome from scratch.
+"""
+
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parents[1]
+SESSIONS_SRC = (REPO / "static" / "sessions.js").read_text(encoding="utf-8")
+UI_SRC = (REPO / "static" / "ui.js").read_text(encoding="utf-8")
+
+
+def _function_body(src: str, signature: str) -> str:
+    start = src.find(signature)
+    assert start != -1, f"missing {signature}"
+    brace = src.find("{", start)
+    assert brace != -1, f"missing opening brace for {signature}"
+    depth = 0
+    for i in range(brace, len(src)):
+        ch = src[i]
+        if ch == "{":
+            depth += 1
+        elif ch == "}":
+            depth -= 1
+            if depth == 0:
+                return src[brace + 1 : i]
+    raise AssertionError(f"could not extract function body for {signature}")
+
+
+def test_loadSession_clears_busy_before_async_message_load_when_server_idle():
+    body = _function_body(SESSIONS_SRC, "async function loadSession(")
+
+    idle_reset = body.find("if(!activeStreamId){")
+    assert idle_reset != -1, "loadSession must gate idle cleanup on missing active_stream_id"
+    idle_block = body[idle_reset : idle_reset + 500]
+    assert "S.busy=false" in idle_block, "idle switch must clear S.busy immediately"
+    assert "S.activeStreamId=null" in idle_block, "idle switch must clear S.activeStreamId immediately"
+
+    ensure_load = body.find("await _ensureMessagesLoaded(sid)")
+    assert ensure_load != -1, "loadSession must still lazy-load messages for idle sessions"
+    assert idle_reset < ensure_load, (
+        "S.busy must be cleared before _ensureMessagesLoaded so session-list polling "
+        "during the async gap does not mark the new session as locally streaming"
+    )
+
+
+def test_loadSession_snapshots_live_turn_before_wiping_message_pane():
+    body = _function_body(SESSIONS_SRC, "async function loadSession(")
+
+    snap_pos = body.find("snapshotLiveTurnHtmlForSession(currentSid)")
+    # Anchor on the actual loading-placeholder marker (unique), not the
+    # whitespace-sensitive innerHTML literal which also matches the
+    # "Session not available" error handler. (Maintainer review.)
+    wipe_pos = body.find("Loading conversation...")
+    assert snap_pos != -1, "loadSession must snapshot the outgoing live turn before switching"
+    assert wipe_pos != -1, "loadSession must still show the loading placeholder on switch"
+    assert snap_pos < wipe_pos, "snapshot must run before msgInner is replaced with the loading placeholder"
+
+
+def test_loadSession_restores_live_turn_on_active_stream_return_path():
+    body = _function_body(SESSIONS_SRC, "async function loadSession(")
+
+    # The restore that actually fires on switch-back is the Phase 2a path: after
+    # loadInflightState() rehydrates INFLIGHT for an active stream, the streaming
+    # branch calls restoreLiveTurnHtmlForSession(sid). (The old Phase-2b idle-branch
+    # call was unreachable — INFLIGHT is always seeded by then — so assert the live
+    # Phase 2a path. Maintainer review.)
+    phase2a = body.find("Phase 2a")
+    assert phase2a != -1, "loadSession must keep the Phase 2a streaming-restore branch"
+    inflight_load = body.find("loadInflightState(sid", phase2a)
+    assert inflight_load != -1, "Phase 2a must rehydrate INFLIGHT from persisted state for an active stream"
+    restore = body.find("restoreLiveTurnHtmlForSession(sid)", inflight_load)
+    assert restore != -1, (
+        "the active-stream return path must restore the snapshotted live-turn HTML "
+        "after rehydrating INFLIGHT (Phase 2a), instead of rebuilding the worklog shell"
+    )
+
+
+def test_activity_timer_reads_pending_started_at():
+    body = _function_body(UI_SRC, "function _activityElapsedStartedAt(")
+    assert "pending_started_at" in body
+    assert "data-turn-started-at" in body or "turnStartedAt" in body

tests/test_stable_assistant_turn_anchor_normalizer.py

@@ -182,7 +182,7 @@ def test_normalizer_maps_live_and_replay_to_same_anchor_event_identity():
     live = data["liveToken"]
     replay = data["replayToken"]
 
-    assert data["version"] == "slice3-registry-shadow"
+    assert data["version"] == "slice5-activity-scene"
     assert live["classification"] == "activity"
     assert live["dedupe_key"] == 'event_id:"run-1:7"'
     assert replay["dedupe_key"] == live["dedupe_key"]

tests/test_stable_assistant_turn_anchor_phase0.py

@@ -88,8 +88,11 @@ def test_phase0_scaffold_is_loaded_before_current_rendering_modules():
     messages_pos = html.index('static/messages.js?v=__WEBUI_VERSION__')
 
     assert anchor_pos < ui_pos < sessions_pos < messages_pos
+    ui_src = _read(UI_JS)
     assert "'./static/assistant_turn_anchors.js' + VQ" in _read(SW_JS)
-    assert "HermesAssistantTurnAnchors" not in _read(UI_JS)
+    assert "projectAssistantTurnAnchorSettledMessageFinalAnswer" in ui_src
+    assert "createAssistantTurnAnchorRegistry" not in ui_src
+    assert "applyAssistantTurnAnchorSourceEvent" not in ui_src
     assert "HermesAssistantTurnAnchors" not in _read(SESSIONS_JS)
     assert "HermesAssistantTurnAnchors" not in _read(MESSAGES_JS)
 

tests/test_stable_assistant_turn_anchor_registry.py

@@ -111,6 +111,150 @@ console.log(JSON.stringify({{
     assert result.returncode == 0, result.stderr
     return json.loads(result.stdout)
 
+def _activity_scene_snapshot() -> dict:
+    assert NODE, "node is required for assistant_turn_anchors.js registry tests"
+    script = f"""
+const fs = require('fs');
+const vm = require('vm');
+const src = fs.readFileSync({json.dumps(str(ANCHORS_JS))}, 'utf8');
+const sandbox = {{window:{{}}}};
+vm.createContext(sandbox);
+vm.runInContext(src, sandbox, {{filename:'assistant_turn_anchors.js'}});
+const api = sandbox.window.HermesAssistantTurnAnchors;
+const registry = api.createAssistantTurnAnchorRegistry({{
+  session_id:'sid-scene',
+  turn_id:'turn-scene',
+}});
+api.applyAssistantTurnAnchorSourceEvents(registry, [
+  {{event:'token', payload:{{text:'progress'}}, event_id:'run-scene:1', seq:1}},
+  {{event:'reasoning', payload:{{text:'private thinking'}}, event_id:'run-scene:2', seq:2}},
+  {{event:'tool', payload:{{
+    tool_call_id:'tool-1',
+    name:'terminal',
+    args:{{command:'rg anchor static'}},
+    preview:'rg anchor static',
+    activityBurstId:7,
+    activitySegmentSeq:3,
+    assistant_msg_idx:12,
+    started_at:1781200000
+  }}, event_id:'run-scene:3', seq:3}},
+  {{event:'tool_update', payload:{{
+    tool_call_id:'tool-1',
+    name:'terminal',
+    text:'running',
+    preview:'searching workspace',
+    activityBurstId:7,
+    activitySegmentSeq:3,
+    assistant_msg_idx:12
+  }}, event_id:'run-scene:4', seq:4}},
+  {{event:'tool_complete', payload:{{
+    tool_call_id:'tool-1',
+    name:'terminal',
+    result:'done',
+    output:'done',
+    snippet:'done',
+    is_error:false,
+    duration:1.25,
+    activityBurstId:7,
+    activitySegmentSeq:3,
+    assistant_msg_idx:12
+  }}, event_id:'run-scene:5', seq:5}},
+  {{event:'done', payload:{{}}, event_id:'run-scene:6', seq:6}},
+  {{source_type:'settled_message', payload:{{role:'assistant', id:'message-scene', content:'final answer'}}}},
+], {{run_id:'run-scene', stream_id:'stream-scene'}});
+const compact = api.projectAssistantTurnAnchorActivityScene(registry, {{mode:'compact_worklog'}});
+const transparent = api.projectAssistantTurnAnchorActivityScene(registry.anchor, {{mode:'transparent_stream'}});
+const empty = api.projectAssistantTurnAnchorActivityScene(null, {{mode:'transparent_stream'}});
+const seqlessRegistry = api.createAssistantTurnAnchorRegistry({{
+  session_id:'sid-seqless',
+  turn_id:'turn-seqless',
+}});
+api.applyAssistantTurnAnchorSourceEvents(seqlessRegistry, [
+  {{event:'tool', payload:{{tool_call_id:'tool-same', name:'terminal'}}}},
+  {{event:'tool_update', payload:{{tool_call_id:'tool-same', text:'running'}}}},
+  {{event:'tool_complete', payload:{{tool_call_id:'tool-same', result:'done'}}}},
+]);
+const seqless = api.projectAssistantTurnAnchorActivityScene(seqlessRegistry, {{mode:'compact_worklog'}});
+const zeroRegistry = api.createAssistantTurnAnchorRegistry({{
+  session_id:'sid-zero',
+  turn_id:'turn-zero',
+}});
+api.applyAssistantTurnAnchorSourceEvents(zeroRegistry, [
+  {{event:'tool', payload:{{
+    tool_call_id:'tool-zero',
+    name:'terminal',
+    activityBurstId:0,
+    activitySegmentSeq:0,
+    assistant_msg_idx:0
+  }}, event_id:'run-zero:0', seq:0}},
+]);
+const zero = api.projectAssistantTurnAnchorActivityScene(zeroRegistry, {{mode:'compact_worklog'}});
+console.log(JSON.stringify({{
+  version:api.version,
+  compact,
+  transparent,
+  empty,
+  seqless,
+  zero,
+}}));
+"""
+    result = subprocess.run([NODE, "-e", script], text=True, capture_output=True, check=False)
+    assert result.returncode == 0, result.stderr
+    return json.loads(result.stdout)
+
+
+def _final_projection_snapshot() -> dict:
+    assert NODE, "node is required for assistant_turn_anchors.js registry tests"
+    script = f"""
+const fs = require('fs');
+const vm = require('vm');
+const src = fs.readFileSync({json.dumps(str(ANCHORS_JS))}, 'utf8');
+const sandbox = {{window:{{}}}};
+vm.createContext(sandbox);
+vm.runInContext(src, sandbox, {{filename:'assistant_turn_anchors.js'}});
+const api = sandbox.window.HermesAssistantTurnAnchors;
+const projected = api.projectAssistantTurnAnchorSettledMessageFinalAnswer({{
+  role:'assistant',
+  id:'message-final',
+  content:'raw content should be replaced by render-preserved content',
+  _turnUsage:{{input_tokens:8, output_tokens:13}},
+}}, {{
+  session_id:'sid-project',
+  raw_idx:7,
+  content:'line one\\nline two',
+}});
+const projectedByRawIdx = api.projectAssistantTurnAnchorSettledMessageFinalAnswer({{
+  role:'assistant',
+  content:'message without id',
+}}, {{
+  session_id:'sid-project',
+  raw_idx:11,
+  content:'raw index final',
+}});
+const missingSession = api.projectAssistantTurnAnchorSettledMessageFinalAnswer({{
+  role:'assistant',
+  id:'message-missing-session',
+  content:'final',
+}}, {{}});
+const nonAssistant = api.projectAssistantTurnAnchorSettledMessageFinalAnswer({{
+  role:'user',
+  id:'message-user',
+  content:'user text',
+}}, {{
+  session_id:'sid-project',
+}});
+console.log(JSON.stringify({{
+  version:api.version,
+  projected,
+  projectedByRawIdx,
+  missingSession,
+  nonAssistant,
+}}));
+"""
+    result = subprocess.run([NODE, "-e", script], text=True, capture_output=True, check=False)
+    assert result.returncode == 0, result.stderr
+    return json.loads(result.stdout)
+
 
 def _hardening_snapshot() -> dict:
     assert NODE, "node is required for assistant_turn_anchors.js registry tests"
@@ -289,7 +433,7 @@ def test_registry_owns_one_anchor_and_dedupes_live_plus_replay_events():
     registry = data["registry"]
     anchor = registry["anchor"]
 
-    assert data["version"] == "slice3-registry-shadow"
+    assert data["version"] == "slice5-activity-scene"
     assert [item["reason"] for item in data["results"][:2]] == [None, "duplicate"]
     assert registry["event_index"]["dedupe_keys"][:2] == [
         'event_id:"run-1:1"',
@@ -389,7 +533,7 @@ def test_registry_does_not_destructively_dedupe_seqless_local_tool_lifecycle():
     registry = data["toolRegistry"]
     anchor = registry["anchor"]
 
-    assert data["version"] == "slice3-registry-shadow"
+    assert data["version"] == "slice5-activity-scene"
     assert data["toolResults"] == [
         {"applied": True, "reason": None},
         {"applied": True, "reason": None},
@@ -439,7 +583,7 @@ def test_shadow_snapshot_feeds_current_source_families_into_one_registry_owner()
     registry = data["registry"]
     anchor = registry["anchor"]
 
-    assert data["version"] == "slice3-registry-shadow"
+    assert data["version"] == "slice5-activity-scene"
     assert data["results"]["live"] == [{"applied": True, "reason": None}]
     assert data["results"]["replay"] == [
         {"applied": False, "reason": "duplicate"},
@@ -462,6 +606,195 @@ def test_shadow_snapshot_feeds_current_source_families_into_one_registry_owner()
     ]
     assert anchor["content"]["final_answer"] == "shadow final"
 
+def test_activity_scene_projects_current_activity_events_for_both_render_modes():
+    data = _activity_scene_snapshot()
+    compact = data["compact"]
+    transparent = data["transparent"]
+
+    assert data["version"] == "slice5-activity-scene"
+    assert compact["version"] == "activity_scene_v1"
+    assert transparent["version"] == "activity_scene_v1"
+    assert compact["mode"] == "compact_worklog"
+    assert transparent["mode"] == "transparent_stream"
+    assert compact["final_answer"] == "final answer"
+    assert transparent["final_answer"] == "final answer"
+    assert compact["terminal_state"] == "completed"
+    assert transparent["terminal_state"] == "completed"
+
+    compact_rows = compact["activity_rows"]
+    transparent_rows = transparent["activity_rows"]
+    assert [row["row_id"] for row in compact_rows] == [
+        "run-scene:1",
+        "run-scene:2",
+        "run-scene:3",
+        "run-scene:4",
+        "run-scene:5",
+        "run-scene:6",
+    ]
+    assert [row["row_id"] for row in transparent_rows] == [
+        row["row_id"] for row in compact_rows
+    ]
+    assert [row["kind"] for row in compact_rows] == [
+        "process_prose",
+        "reasoning",
+        "tool_started",
+        "tool_updated",
+        "tool_completed",
+        "terminal_status",
+    ]
+    assert [row["role"] for row in compact_rows] == [
+        "prose",
+        "thinking",
+        "tool",
+        "tool",
+        "tool",
+        "terminal",
+    ]
+    assert [row["display_hint"] for row in compact_rows] == [
+        "main_prose",
+        "collapsed_thinking",
+        "tool_row",
+        "tool_row",
+        "tool_row",
+        "terminal_status_row",
+    ]
+    assert all(row["display_hint"] == "chronological_activity" for row in transparent_rows)
+    assert compact_rows[0]["text"] == "progress"
+    assert compact_rows[0]["tool_call_id"] is None
+    assert compact_rows[2]["tool_call_id"] == "tool-1"
+    assert compact_rows[4]["text"] == "done"
+    assert compact_rows[1]["thinking"] == {
+        "text": "private thinking",
+        "preview": "private thinking",
+        "dedupe_key": "thinking:private thinking",
+    }
+    assert compact_rows[2]["group"] == {
+        "group_key": "segment:3",
+        "activity_burst_id": 7,
+        "activity_segment_seq": 3,
+        "assistant_msg_idx": 12,
+    }
+    assert compact_rows[2]["tool"] == {
+        "id": "tool-1",
+        "name": "terminal",
+        "args": {"command": "rg anchor static"},
+        "preview": "rg anchor static",
+        "snippet": "",
+        "result": None,
+        "output": None,
+        "done": False,
+        "is_error": False,
+        "duration": None,
+        "started_at": 1781200000,
+        "signature": 'terminal|tool-1|{"command":"rg anchor static"}',
+    }
+    assert compact_rows[4]["tool"]["done"] is True
+    assert compact_rows[4]["tool"]["is_error"] is False
+    assert compact_rows[4]["tool"]["duration"] == 1.25
+    assert compact_rows[4]["tool"]["snippet"] == "done"
+    assert compact_rows[4]["display_hints"] == {
+        "compact_worklog": "tool_row",
+        "transparent_stream": "chronological_activity",
+    }
+    seqless_ids = [row["row_id"] for row in data["seqless"]["activity_rows"]]
+    assert len(seqless_ids) == len(set(seqless_ids))
+    assert seqless_ids == [
+        "tool-same:tool:0",
+        "tool-same:tool_update:1",
+        "tool-same:tool_complete:2",
+    ]
+    assert data["zero"]["activity_rows"][0]["group"] == {
+        "group_key": "segment:0",
+        "activity_burst_id": 0,
+        "activity_segment_seq": 0,
+        "assistant_msg_idx": 0,
+    }
+
+
+def test_activity_scene_is_renderer_neutral_and_empty_safe():
+    data = _activity_scene_snapshot()
+    compact = data["compact"]
+    empty = data["empty"]
+
+    assert "final answer" not in [row["text"] for row in compact["activity_rows"]]
+    assert compact["identity"]["session_id"] == "sid-scene"
+    assert compact["identity"]["run_id"] == "run-scene"
+    assert compact["identity"]["stream_id"] == "stream-scene"
+    assert empty == {
+        "version": "activity_scene_v1",
+        "mode": "transparent_stream",
+        "identity": {"source_message_refs": []},
+        "lifecycle": {},
+        "final_answer": "",
+        "final_message_ref": None,
+        "terminal_state": None,
+        "activity_rows": [],
+    }
+
+
+def test_final_projection_routes_settled_assistant_message_through_anchor_owner():
+    data = _final_projection_snapshot()
+    projected = data["projected"]
+    registry = projected["registry"]
+    anchor = registry["anchor"]
+
+    assert data["version"] == "slice5-activity-scene"
+    assert projected["applied"] is True
+    assert projected["reason"] is None
+    assert projected["final_message_ref"] == "message-final"
+    assert projected["final_answer"] == "line one\nline two"
+    assert registry["stats"]["applied"] == 1
+    assert anchor["identity"]["session_id"] == "sid-project"
+    assert anchor["content"]["final_answer"] == "line one\nline two"
+    assert anchor["content"]["final_message_ref"] == "message-final"
+    assert anchor["usage"] == {"input_tokens": 8, "output_tokens": 13}
+    assert [event["source_event_type"] for event in anchor["metadata_events"]] == [
+        "settled_message",
+    ]
+    assert data["projectedByRawIdx"]["final_message_ref"] == "raw_idx:11"
+    assert data["projectedByRawIdx"]["registry"]["anchor"]["identity"][
+        "source_message_refs"
+    ] == ["raw_idx:11"]
+    anchor_src = _read(ANCHORS_JS)
+    assert "if(!result.applied)" in anchor_src
+
+
+def test_final_projection_is_scoped_to_settled_assistant_messages():
+    data = _final_projection_snapshot()
+
+    assert data["missingSession"] == {
+        "applied": False,
+        "reason": "missing_session",
+        "final_answer": "",
+        "final_message_ref": None,
+        "registry": None,
+    }
+    assert data["nonAssistant"] == {
+        "applied": False,
+        "reason": "non_assistant",
+        "final_answer": "",
+        "final_message_ref": None,
+        "registry": None,
+    }
+
+
+def test_render_messages_uses_anchor_projection_only_for_settled_final_prose():
+    src = _read(UI_JS)
+    start = src.index("function renderMessages")
+    end = src.index("function _toolDisplayName", start)
+    render_body = src[start:end]
+
+    flatten_idx = render_body.index("content=content.filter(p=>p&&p.type==='text')")
+    projection_idx = render_body.index("_assistantTurnAnchorSettledFinalAnswer(m, content")
+    thinking_idx = render_body.index("_extractInlineThinkingFromContentForRender(content")
+
+    assert flatten_idx < projection_idx < thinking_idx
+    assert "if(m.role==='assistant'&&!m._live&&typeof content==='string'){" in render_body
+    assert "createAssistantTurnAnchorRegistry" not in render_body
+    assert "applyAssistantTurnAnchorSourceEvent" not in render_body
+    assert "_assistantTurnAnchorSettledFinalAnswerWarned" in src
+    assert "console.warn('assistant turn anchor settled-final projection failed',err)" in src
+
 
 def test_registry_instances_do_not_share_owner_state():
     data = _registry_snapshot()
@@ -472,8 +805,7 @@ def test_registry_instances_do_not_share_owner_state():
     assert isolated["stats"]["applied"] == 0
     assert isolated["anchor"]["activity_events"] == []
 
-
-def test_slice3_registry_is_still_unwired_from_rendering_hot_paths():
+def test_slice5_scene_projection_does_not_wire_activity_scene_into_rendering_hot_paths():
     helper_names = [
         "createAssistantTurnAnchorRegistry",
         "applyAssistantTurnAnchorNormalizedEvent",
@@ -485,3 +817,7 @@ def test_slice3_registry_is_still_unwired_from_rendering_hot_paths():
         assert helper not in _read(UI_JS)
         assert helper not in _read(SESSIONS_JS)
         assert helper not in _read(MESSAGES_JS)
+    assert "projectAssistantTurnAnchorSettledMessageFinalAnswer" in _read(UI_JS)
+    assert "projectAssistantTurnAnchorActivityScene" not in _read(UI_JS)
+    assert "projectAssistantTurnAnchorActivityScene" not in _read(SESSIONS_JS)
+    assert "projectAssistantTurnAnchorActivityScene" not in _read(MESSAGES_JS)

tests/test_stale_stream_cleanup.py

@@ -398,13 +398,19 @@ def test_stale_stream_cleanup_does_not_clobber_concurrent_chat_start(monkeypatch
 
 
 def test_frontend_drops_inflight_cache_when_server_session_is_idle():
-    marker = "If the server says the session is idle, discard any browser-side inflight"
+    # #3900/#3899 generalized this block: on an idle server session it now resets
+    # the streaming flags (S.busy/S.activeStreamId) AND drops the inflight cache,
+    # before the async message-load gap. Anchor on the current comment + assert the
+    # (preserved) cache-drop behavior in the now-nested form.
+    marker = "If the server says the session is idle, reset browser-side streaming flags"
     marker_pos = SESSIONS_SRC.index(marker)
-    window = SESSIONS_SRC[marker_pos:marker_pos + 500]
-    assert "if(!activeStreamId&&INFLIGHT[sid])" in window
+    window = SESSIONS_SRC[marker_pos:marker_pos + 900]
+    assert "if(!activeStreamId){" in window
+    assert "S.busy=false" in window
+    assert "S.activeStreamId=null" in window
+    assert "if(INFLIGHT[sid]){" in window
     assert "delete INFLIGHT[sid]" in window
     assert "clearInflightState" in window
-    assert "S.busy=false" in window
 
 
 def test_service_worker_cache_bumped_for_frontend_fix_delivery():