diff --git a/backend/app/api/misc.py b/backend/app/api/misc.py
index a47e1d6..3064cf5 100644
--- a/backend/app/api/misc.py
+++ b/backend/app/api/misc.py
@@ -1,7 +1,7 @@
-"""Glossary + Triggers routes."""
+"""Glossary + Triggers + public UI settings routes."""
 from __future__ import annotations
 
-from typing import List
+from typing import Any, Dict, List
 from uuid import UUID
 
 from sqlalchemy import select
@@ -11,12 +11,37 @@ from fastapi import APIRouter, Depends, HTTPException
 
 from app.db import get_db_dep
 from app.deps import get_current_user
-from app.models import DeferredTrigger, GlossaryEntry, Session, User, World
+from app.models import DeferredTrigger, GlossaryEntry, Session, Setting, User, World
 from app.schemas import GlossaryEntryOut, TriggerOut
 
 router = APIRouter(prefix="/api", tags=["misc"])
 
 
+# Public, unauthenticated UI settings (logo URL etc.) — used by the frontend
+# on the login/register/home pages BEFORE the user is authenticated, so the
+# branding (logo, eventually theme) shows up everywhere.
+#
+# Only a curated subset of settings is exposed here. Anything sensitive (api
+# keys, internal URLs, admin tokens) MUST stay behind /api/admin/settings.
+PUBLIC_SETTING_KEYS = ("ui.logo_url",)
+_PUBLIC_DEFAULTS: Dict[str, Any] = {"ui.logo_url": "/logo.png"}
+
+
+@router.get("/settings/public")
+async def get_public_settings(db: AsyncSession = Depends(get_db_dep)):
+    """Return UI settings that are safe to expose without authentication.
+
+    Used by the frontend to render the logo (and other public branding) on
+    every page, including login/register. The response shape is a flat
+    `{key: value}` dict.
+    """
+    out: Dict[str, Any] = dict(_PUBLIC_DEFAULTS)
+    rows = await db.execute(select(Setting).where(Setting.key.in_(PUBLIC_SETTING_KEYS)))
+    for row in rows.scalars().all():
+        out[row.key] = row.value
+    return out
+
+
 @router.get("/worlds/{world_id}/glossary", response_model=List[GlossaryEntryOut])
 async def list_glossary(
     world_id: UUID,
diff --git a/backend/app/api/sessions.py b/backend/app/api/sessions.py
index 8aa9789..7eaf367 100644
--- a/backend/app/api/sessions.py
+++ b/backend/app/api/sessions.py
@@ -14,7 +14,7 @@ from sse_starlette.sse import EventSourceResponse
 
 from app.db import get_db_dep
 from app.deps import get_current_user
-from app.engine.orchestrator import run_iteration
+from app.engine.orchestrator import generate_intro_scene, run_iteration
 from app.models import Message, Session, User, World
 from app.schemas import IterationRequest, MessageOut, SessionCreate, SessionOut
 
@@ -142,6 +142,35 @@ async def iterate_session(
     return EventSourceResponse(event_generator())
 
 
+@router.post("/{session_id}/intro")
+async def intro_session(
+    session_id: UUID,
+    db: AsyncSession = Depends(get_db_dep),
+    user: User = Depends(get_current_user),
+):
+    """SSE stream that generates the opening cinematic scene for a new session."""
+    result = await db.execute(
+        select(Session).join(World, Session.world_id == World.id).where(Session.id == session_id)
+    )
+    session = result.scalars().first()
+    if not session:
+        raise HTTPException(status_code=404, detail="session_not_found")
+    w_result = await db.execute(select(World).where(World.id == session.world_id))
+    world = w_result.scalars().first()
+    if not world or (world.owner_id != user.id and not user.is_admin):
+        raise HTTPException(status_code=403, detail="forbidden")
+
+    async def event_generator():
+        try:
+            async for event in generate_intro_scene(db=db, user_id=user.id, session_id=session_id):
+                yield {"event": event["type"], "data": json.dumps(event.get("data", {}), ensure_ascii=False, default=str)}
+        except Exception as e:
+            yield {"event": "error", "data": json.dumps({"message": str(e)}, ensure_ascii=False)}
+            yield {"event": "done", "data": "{}"}
+
+    return EventSourceResponse(event_generator())
+
+
 @router.delete("/{session_id}", status_code=204)
 async def delete_session(
     session_id: UUID,
diff --git a/backend/app/api/worlds.py b/backend/app/api/worlds.py
index bd869ba..976f819 100644
--- a/backend/app/api/worlds.py
+++ b/backend/app/api/worlds.py
@@ -12,6 +12,7 @@ from fastapi import APIRouter, Depends, HTTPException
 from app.db import get_db_dep
 from app.deps import get_current_user
 from app.engine.world_builder import commit_world_builder, continue_world_builder, start_world_builder
+from app.engine.world_editor import edit_world_via_chat, reset_editor_dialogue
 from app.models import User, World
 from app.schemas import (
     WorldBuilderCommit,
@@ -19,6 +20,8 @@ from app.schemas import (
     WorldBuilderReply,
     WorldBuilderStart,
     WorldCreate,
+    WorldEditorChatReply,
+    WorldEditorChatRequest,
     WorldOut,
     WorldUpdate,
 )
@@ -159,3 +162,56 @@ async def builder_commit(
         raise HTTPException(status_code=400, detail=str(e))
     except Exception as e:
         raise HTTPException(status_code=500, detail=f"builder_commit_failed: {e}")
+
+
+
+# === World Editor (AI-assisted editing of an existing world) ===
+
+@router.post("/{world_id}/chat", response_model=WorldEditorChatReply)
+async def world_editor_chat(
+    world_id: UUID,
+    payload: WorldEditorChatRequest,
+    db: AsyncSession = Depends(get_db_dep),
+    user: User = Depends(get_current_user),
+):
+    """Chat with the AI to edit an existing world's definition.
+
+    Returns the AI's prose reply plus the proposed new definition. The
+    frontend must call PATCH /worlds/{id} to actually persist the change.
+    """
+    result = await db.execute(select(World).where(World.id == world_id))
+    world = result.scalars().first()
+    if not world:
+        raise HTTPException(status_code=404, detail="world_not_found")
+    if world.owner_id != user.id and not user.is_admin:
+        raise HTTPException(status_code=403, detail="forbidden")
+    try:
+        ai_message, new_defn, changed = await edit_world_via_chat(
+            db=db, user=user, world=world, message=payload.message,
+        )
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"world_editor_chat_failed: {e}")
+    return WorldEditorChatReply(
+        ai_message=ai_message,
+        definition=new_defn,
+        changed=changed,
+    )
+
+
+@router.post("/{world_id}/chat/reset")
+async def world_editor_chat_reset(
+    world_id: UUID,
+    db: AsyncSession = Depends(get_db_dep),
+    user: User = Depends(get_current_user),
+):
+    """Clear the cached editor dialogue for a world (start fresh)."""
+    result = await db.execute(select(World).where(World.id == world_id))
+    world = result.scalars().first()
+    if not world:
+        raise HTTPException(status_code=404, detail="world_not_found")
+    if world.owner_id != user.id and not user.is_admin:
+        raise HTTPException(status_code=403, detail="forbidden")
+    reset_editor_dialogue(world_id)
+    return {"ok": True}
diff --git a/backend/app/core/llm.py b/backend/app/core/llm.py
index 074ea4b..7570ca9 100644
--- a/backend/app/core/llm.py
+++ b/backend/app/core/llm.py
@@ -16,6 +16,37 @@ from app.models import LlmCallLog
 log = get_logger("llm")
 
 
+# vendor-specific end-of-sequence / control tokens that some local models
+# emit into the content stream. Strip them so they don't leak to the user.
+_EOS_TOKENS = (
+    "<eos>",
+    "</s>",
+    "<|endoftext|>",
+    "<|im_end|>",
+    "<|end|>",
+    "<|eot_id|>",
+    "<|eom_id|>",
+)
+
+
+def _clean_model_text(text: str) -> str:
+    """Remove vendor-specific end-of-sequence tokens and collapse whitespace.
+
+    Some local models leak control tokens into the visible content stream.
+    We strip them so they never reach the user.
+    """
+    if not text:
+        return text
+    cleaned = text
+    for tok in _EOS_TOKENS:
+        cleaned = cleaned.replace(tok, "")
+    while "\n\n\n" in cleaned:
+        cleaned = cleaned.replace("\n\n\n", "\n\n")
+    return cleaned
+
+
+
+
 class LlmResponse:
     """Non-streaming response wrapper."""
 
@@ -93,7 +124,7 @@ class LlmClient:
                 data = resp.json()
             choice = (data.get("choices") or [{}])[0]
             msg = choice.get("message", {})
-            text = msg.get("content") or ""
+            text = _clean_model_text(msg.get("content") or "")
             tool_calls = msg.get("tool_calls") or []
             usage = data.get("usage") or {}
         except httpx.ConnectError as e:
@@ -206,8 +237,10 @@ class LlmClient:
                             continue
                         delta = choices[0].get("delta", {})
                         if delta.get("content"):
-                            full_text_parts.append(delta["content"])
-                            yield {"type": "delta", "content": delta["content"]}
+                            piece = _clean_model_text(delta["content"])
+                            if piece:
+                                full_text_parts.append(piece)
+                                yield {"type": "delta", "content": piece}
                         if delta.get("tool_calls"):
                             for tc in delta["tool_calls"]:
                                 idx = tc.get("index", 0)
diff --git a/backend/app/core/settings_service.py b/backend/app/core/settings_service.py
index 75bcce6..665a9bb 100644
--- a/backend/app/core/settings_service.py
+++ b/backend/app/core/settings_service.py
@@ -34,6 +34,8 @@ EDITABLE_SETTING_KEYS = {
     "embedding.model": str,           # e.g. text-embedding-3-small, bge-m3, nomic-embed-text
     "embedding.dim": int,             # vector dimension; 0 = auto-probe from endpoint
     "embedding.request_timeout": int, # request timeout, seconds
+    # UI customization (logo URL/path shown in navbar + home page + favicon)
+    "ui.logo_url": str,               # e.g. "/logo.png", "https://.../logo.png", or "data:image/png;base64,..."
 }
 
 
diff --git a/backend/app/engine/orchestrator.py b/backend/app/engine/orchestrator.py
index cdb9423..448b4b7 100644
--- a/backend/app/engine/orchestrator.py
+++ b/backend/app/engine/orchestrator.py
@@ -72,21 +72,39 @@ async def run_iteration(
     settings_map = await get_all_settings(db)
     llm = LlmClient(settings_map)
 
-    # Save the player's action as a message
-    next_seq = await _next_seq(db, session_id)
-    player_msg = Message(
-        session_id=session_id,
-        seq=next_seq,
-        role="user",
-        kind="player_action",
-        content=action_text,
-        payload={},
-        is_pinned=True,
-        hidden=False,
+    # Save the player's action as a message — UNLESS this is a retry of the
+    # previous action (frontend re-sent the same action_text after an error).
+    # In that case we reuse the existing player_action row so the chat
+    # history doesn't fill up with duplicates.
+    last_msg_result = await db.execute(
+        select(Message)
+        .where(Message.session_id == session_id)
+        .order_by(Message.seq.desc())
+        .limit(1)
     )
-    db.add(player_msg)
-    await db.commit()
-    await db.refresh(player_msg)
+    last_msg = last_msg_result.scalars().first()
+    is_retry = (
+        last_msg is not None
+        and last_msg.kind == "player_action"
+        and last_msg.content == action_text
+    )
+    if is_retry:
+        player_msg = last_msg
+    else:
+        next_seq = await _next_seq(db, session_id)
+        player_msg = Message(
+            session_id=session_id,
+            seq=next_seq,
+            role="user",
+            kind="player_action",
+            content=action_text,
+            payload={},
+            is_pinned=True,
+            hidden=False,
+        )
+        db.add(player_msg)
+        await db.commit()
+        await db.refresh(player_msg)
 
     yield {"type": "status", "data": {"message": "planning"}}
 
@@ -476,3 +494,122 @@ def _safe_parse_json(s: str) -> Any:
         return json.loads(s) if s else {}
     except Exception:
         return s
+
+
+
+async def generate_intro_scene(
+    db: AsyncSession,
+    user_id: uuid.UUID,
+    session_id: uuid.UUID,
+) -> AsyncIterator[Dict[str, Any]]:
+    """Generate the opening cinematic scene for a freshly-created session.
+
+    Yields the same SSE event stream shape as `run_iteration` so the
+    frontend can consume it identically. Saves a `narrative_step` message
+    of kind `intro_scene` (still kind=narrative_step for compatibility,
+    but with payload.kind=intro so the UI can style it differently if
+    desired).
+    """
+    result = await db.execute(select(Session).where(Session.id == session_id))
+    session = result.scalars().first()
+    if not session:
+        yield {"type": "error", "data": {"message": "session_not_found"}}
+        return
+    result = await db.execute(select(World).where(World.id == session.world_id))
+    world = result.scalars().first()
+    if not world:
+        yield {"type": "error", "data": {"message": "world_not_found"}}
+        return
+
+    settings_map = await get_all_settings(db)
+    llm = LlmClient(settings_map)
+
+    yield {"type": "status", "data": {"message": "writing_scene"}}
+
+    import json as _json
+    defn = world.definition or {}
+    player_state = world.state.get("player", {}) if world.state else {}
+    system_prompt = get_prompt("intro_scene", world.language).format(
+        setting_description=defn.get("setting_description", "")[:1200],
+        current_time=world.current_time or "",
+        player_state=_json.dumps(player_state, ensure_ascii=False)[:800],
+        plot_rails=_json.dumps(defn.get("plot_rails", {}), ensure_ascii=False)[:600],
+        world_language=world.language or "en",
+    )
+
+    step_resp = await llm.chat(
+        messages=[{"role": "system", "content": system_prompt}],
+        tools=STEP_WRITER_TOOL_SCHEMAS,
+        temperature=float(cast_setting("llm.step_temperature", settings_map.get("llm.step_temperature", 0.85))),
+        max_tokens=1500,
+        purpose="intro_scene",
+        user_id=user_id,
+        session_id=session_id,
+        db=db,
+    )
+
+    step_text = step_resp.text or ""
+    step_options: List[str] = []
+    for tc in (step_resp.tool_calls or []):
+        if tc.get("function", {}).get("name") == "submit_scene":
+            args_str = tc.get("function", {}).get("arguments", "{}")
+            try:
+                scene_data = _json.loads(args_str) if args_str else {}
+                if scene_data.get("narrative"):
+                    step_text = scene_data["narrative"]
+                if scene_data.get("options") and isinstance(scene_data["options"], list):
+                    step_options = [str(o) for o in scene_data["options"]][:5]
+            except _json.JSONDecodeError:
+                log.warning("intro_scene_invalid_json", args=args_str[:200])
+            break
+    else:
+        # Fallback: extract JSON from text.
+        import re as _re
+        json_match = _re.search(r"\{[\s\S]*\}", step_resp.text or "")
+        if json_match:
+            try:
+                step_data = _json.loads(json_match.group(0))
+                if "narrative" in step_data:
+                    step_text = step_data["narrative"]
+                if "options" in step_data and isinstance(step_data["options"], list):
+                    step_options = [str(o) for o in step_data["options"]][:5]
+            except _json.JSONDecodeError:
+                pass
+
+    # Save as a narrative_step message flagged as intro in payload.
+    step_seq = await _next_seq(db, session_id)
+    step_msg = Message(
+        session_id=session_id,
+        seq=step_seq,
+        role="assistant",
+        kind="narrative_step",
+        content=step_text,
+        payload={
+            "kind": "intro",
+            "options": step_options,
+            "world_time": world.current_time,
+            "player_state": world.state.get("player", {}),
+        },
+        is_pinned=True,
+        hidden=False,
+    )
+    db.add(step_msg)
+    session.last_played_at = datetime.now(timezone.utc)
+    await db.commit()
+    await db.refresh(step_msg)
+
+    yield {
+        "type": "step_complete",
+        "data": {
+            "message_id": str(step_msg.id),
+            "seq": step_msg.seq,
+            "narrative": step_text,
+            "options": step_options,
+            "state": world.state,
+            "world_time": world.current_time,
+            "player_state": world.state.get("player", {}),
+            "fired_triggers": [],
+            "is_intro": True,
+        },
+    }
+    yield {"type": "done", "data": {}}
diff --git a/backend/app/engine/world_editor.py b/backend/app/engine/world_editor.py
new file mode 100644
index 0000000..6f1a405
--- /dev/null
+++ b/backend/app/engine/world_editor.py
@@ -0,0 +1,279 @@
+"""AI-assisted editor for an EXISTING world.
+
+The player chats with the AI; each turn the AI returns:
+  - a short player-facing message describing what it changed / will change,
+  - an updated `definition` (the full new WorldDefinition).
+
+The caller (API endpoint) decides whether to persist the new definition
+to the World row. The editor itself is stateless aside from the in-memory
+dialogue cache (keyed by world_id), so the player can iterate.
+"""
+from __future__ import annotations
+
+import json
+import uuid
+from typing import Any, Dict, List, Optional, Tuple
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.llm import LlmClient
+from app.core.settings_service import cast_setting, get_all_settings
+from app.logging_setup import get_logger
+from app.models import User, World
+from app.prompts.templates import get_prompt
+from app.schemas import WorldDefinition
+from app.engine.tools.tools import WORLD_BUILDER_TOOL_SCHEMAS
+
+log = get_logger("world_editor")
+
+
+# In-memory dialogue cache: world_id -> list of messages.
+_DIALOGUES: Dict[uuid.UUID, Dict[str, Any]] = {}
+
+
+async def edit_world_via_chat(
+    db: AsyncSession,
+    user: User,
+    world: World,
+    message: str,
+) -> Tuple[str, Optional[Dict[str, Any]], bool]:
+    """Run one turn of AI-assisted world editing.
+
+    Returns (ai_message, new_definition_dict_or_None, changed).
+      - ai_message: short prose reply for the player (in world.language).
+      - new_definition_dict: the full updated definition if the AI proposed
+        changes this turn, else None.
+      - changed: True if new_definition_dict is not None and differs from
+        the current world.definition.
+    """
+    settings_map = await get_all_settings(db)
+    llm = LlmClient(settings_map)
+
+    # Get / init dialogue state for this world.
+    dialogue = _DIALOGUES.get(world.id)
+    if not dialogue:
+        system_prompt = _build_system_prompt(world)
+        dialogue = {
+            "user_id": user.id,
+            "messages": [
+                {"role": "system", "content": system_prompt},
+                {"role": "user", "content": _build_seed_message(world)},
+            ],
+        }
+        _DIALOGUES[world.id] = dialogue
+
+    # Authorization: only the owner (or admin) may continue an existing dialogue.
+    if dialogue["user_id"] != user.id and not user.is_admin:
+        raise ValueError("forbidden")
+
+    dialogue["messages"].append({"role": "user", "content": message})
+
+    response = await llm.chat(
+        messages=dialogue["messages"],
+        tools=WORLD_BUILDER_TOOL_SCHEMAS,
+        temperature=float(cast_setting("llm.temperature", settings_map.get("llm.temperature", 0.7))),
+        purpose="world_editor",
+        user_id=user.id,
+        db=db,
+    )
+
+    ai_message, new_defn, _is_final = _extract_world_definition(
+        response.text, response.tool_calls,
+    )
+
+    # If the model did not return a tool call but did emit JSON in text,
+    # _extract_world_definition handles it. If still None, just return the
+    # conversational message without changes.
+    if new_defn is None:
+        dialogue["messages"].append({
+            "role": "assistant",
+            "content": response.text or "",
+            "tool_calls": response.tool_calls or None,
+        })
+        return ai_message, None, False
+
+    new_defn_dict = new_defn.model_dump()
+    changed = new_defn_dict != (world.definition or {})
+
+    dialogue["messages"].append({
+        "role": "assistant",
+        "content": response.text or "",
+        "tool_calls": response.tool_calls or None,
+    })
+    return ai_message, new_defn_dict, changed
+
+
+def reset_editor_dialogue(world_id: uuid.UUID) -> None:
+    """Drop the cached editor dialogue for a world (e.g. after manual save)."""
+    _DIALOGUES.pop(world_id, None)
+
+
+def _build_system_prompt(world: World) -> str:
+    """System prompt for the world editor.
+
+    Reuses the world-builder prompt but overrides the workflow: instead of
+    designing from scratch, the AI is told to MODIFY the existing definition.
+    """
+    base = get_prompt("world_builder", world.language)
+    override = (
+        "\n\nADDITIONAL CONTEXT — YOU ARE EDITING AN EXISTING WORLD:\n"
+        "The world already exists with the definition provided in the first "
+        "user message. The player will give you edit instructions in their "
+        "language ({world_language}). For EACH instruction:\n"
+        "1. Call `submit_world_definition` with the FULL updated definition "
+        "(not just the changed fields — the entire object, all required keys).\n"
+        "2. Your text response should briefly summarize what you changed in "
+        "the player's language. 2-4 sentences max.\n"
+        "3. NEVER set `is_final=true` — the player will commit changes "
+        "manually via the Save button.\n"
+        "4. Preserve `initial_state` consistency with `world_schema`. If you "
+        "change the schema, update the state accordingly.\n"
+        "5. Preserve `initial_time` and `calendar` unless the player asks to "
+        "change them.\n"
+    ).format(world_language=world.language or "en")
+    return base + override
+
+
+def _build_seed_message(world: World) -> str:
+    """First user message: dumps the current world definition as context."""
+    defn = world.definition or {}
+    parts = [
+        "=== CURRENT WORLD DEFINITION ===",
+        f"Name: {world.name}",
+        f"Language: {world.language}",
+        f"Current time: {world.current_time or '(none)'}",
+        f"Definition JSON:\n```json\n{json.dumps(defn, ensure_ascii=False, indent=2)}\n```",
+        f"Live state JSON:\n```json\n{json.dumps(world.state or {}, ensure_ascii=False, indent=2)[:2000]}\n```",
+        "",
+        "The player will now give you edit instructions. Apply each one by "
+        "calling submit_world_definition with the FULL updated definition.",
+    ]
+    return "\n".join(parts)
+
+
+# === Output extraction (mirrors world_builder._extract_world_definition) ===
+def _extract_world_definition(
+    text: str,
+    tool_calls: Optional[List[Dict[str, Any]]],
+) -> Tuple[str, Optional[WorldDefinition], bool]:
+    import re as _re
+
+    proposed: Optional[WorldDefinition] = None
+    is_final = False
+    ai_text = _sanitize_model_text(text or "")
+
+    if tool_calls:
+        for tc in tool_calls:
+            if tc.get("function", {}).get("name") == "submit_world_definition":
+                args_str = tc.get("function", {}).get("arguments", "{}")
+                data = _safe_json_loads(args_str, {})
+                if data:
+                    proposed = _try_build_definition(data)
+                    is_final = bool(data.get("is_final", False))
+                    break
+
+    if proposed is None:
+        json_str = _extract_json_block(ai_text)
+        if json_str:
+            data = _safe_json_loads(json_str, None)
+            if isinstance(data, dict):
+                target = data
+                if "proposed_definition" in data and isinstance(data["proposed_definition"], dict):
+                    target = data["proposed_definition"]
+                    if "is_final" in data:
+                        is_final = bool(data["is_final"])
+                    if "ai_message" in data and isinstance(data["ai_message"], str):
+                        ai_text = data["ai_message"]
+                else:
+                    if "is_final" in data:
+                        is_final = bool(data["is_final"])
+                proposed = _try_build_definition(target)
+
+    if proposed is not None:
+        ai_text = _strip_json_blocks(ai_text).strip()
+        if not ai_text:
+            ai_text = "(definition updated)"
+
+    return ai_text, proposed, is_final
+
+
+def _sanitize_model_text(text: str) -> str:
+    if not text:
+        return ""
+    import re as _re
+    cleaned = _re.sub(r"<\s*/?\s*[a-zA-Z]+\s*>", "", text)
+    cleaned = _re.sub(r"\n{3,}", "\n\n", cleaned)
+    return cleaned.strip()
+
+
+def _strip_json_blocks(text: str) -> str:
+    if not text:
+        return ""
+    import re as _re
+    cleaned = _re.sub(r"```[a-zA-Z]*\s*[\s\S]*?```", "", text)
+    m = _re.search(r"\n\{[\s\S]*\}\s*$", cleaned)
+    if m:
+        cleaned = cleaned[: m.start()] + cleaned[m.end():]
+    return cleaned
+
+
+def _safe_json_loads(s: str, default: Any) -> Any:
+    if not s:
+        return default
+    try:
+        return json.loads(s)
+    except json.JSONDecodeError:
+        pass
+    import re as _re
+    repaired = _re.sub(r",\s*([}\]])", r"\1", s)
+    try:
+        return json.loads(repaired)
+    except json.JSONDecodeError:
+        pass
+    try:
+        repaired2 = repaired.replace("'", '"')
+        return json.loads(repaired2)
+    except json.JSONDecodeError:
+        return default
+
+
+def _try_build_definition(data: Dict[str, Any]) -> Optional[WorldDefinition]:
+    try:
+        return WorldDefinition.model_validate(data)
+    except Exception as e:
+        log.warning("world_editor_definition_invalid", error=str(e), keys=list(data.keys()))
+        return None
+
+
+def _extract_json_block(text: str) -> Optional[str]:
+    if not text:
+        return None
+    import re as _re
+    m = _re.search(r"```(?:json)?\s*(\{[\s\S]*?\})\s*```", text)
+    if m:
+        return m.group(1)
+    start = text.find("{")
+    if start == -1:
+        return None
+    depth = 0
+    in_str = False
+    esc = False
+    for i in range(start, len(text)):
+        c = text[i]
+        if in_str:
+            if esc:
+                esc = False
+            elif c == "\\":
+                esc = True
+            elif c == '"':
+                in_str = False
+        else:
+            if c == '"':
+                in_str = True
+            elif c == "{":
+                depth += 1
+            elif c == "}":
+                depth -= 1
+                if depth == 0:
+                    return text[start:i + 1]
+    return None
diff --git a/backend/app/migrations/init_db.py b/backend/app/migrations/init_db.py
index b864316..368c763 100644
--- a/backend/app/migrations/init_db.py
+++ b/backend/app/migrations/init_db.py
@@ -52,6 +52,8 @@ DEFAULT_SETTINGS = [
     ("embedding.model", settings.default_embedding_model, "Embedding model name (e.g. text-embedding-3-small, bge-m3, nomic-embed-text)"),
     ("embedding.dim", settings.default_embedding_dim, "Vector dimension. 0 = auto-probe from endpoint on first use"),
     ("embedding.request_timeout", settings.default_embedding_request_timeout, "Embeddings request timeout, seconds"),
+    # UI customization
+    ("ui.logo_url", "/logo.png", "Logo image URL or path shown in navbar, home page, and favicon. Use a URL (https://...), an absolute path (/logo.png), or a data: URI. Default is the bundled Mikan logo."),
 ]
 
 
diff --git a/backend/app/prompts/templates.py b/backend/app/prompts/templates.py
index 3e94e48..276f083 100644
--- a/backend/app/prompts/templates.py
+++ b/backend/app/prompts/templates.py
@@ -133,6 +133,35 @@ Call the `submit_trigger_result` tool with:
 Your text response is ignored — only the tool call is used."""
 
 
+
+
+
+# === Intro Scene (opening scene generated when a session starts) ===
+INTRO_SCENE_SYSTEM = """You are the narrative writer of a role-playing game. The player has just created a new session and you must write the OPENING scene that sets the stage for the adventure.
+
+CONTEXT:
+- Setting: {setting_description}
+- Initial world time: {current_time}
+- Player state: {player_state}
+- Plot rails (main goal + hooks): {plot_rails}
+
+YOUR JOB:
+1. Call the `submit_scene` tool with:
+   - `narrative`: 250-500 words of cinematic, second-person ("You...") prose that:
+     a) establishes the setting and mood,
+     b) introduces the player character based on `player_state`,
+     c) plants the seed of the main goal / first hook from `plot_rails`,
+     d) ends with a clear decision moment or call to action.
+   - `options`: exactly 3 short (5-12 words) options for the player's first action.
+
+CRITICAL:
+- Write the narrative in {world_language}.
+- Do NOT assume the player has done anything yet — this is the very first scene.
+- Do NOT use the player's name if it is empty or generic; address them as "you".
+- Set the tone: atmospheric, evocative, but grounded in the setting.
+- Your text response is ignored — only the `submit_scene` tool call is used.
+"""
+
 PROMPTS = {
     "en": {
         "world_builder": WORLD_BUILDER_SYSTEM,
@@ -141,6 +170,7 @@ PROMPTS = {
         "summarizer": SUMMARIZER_SYSTEM,
         "subagent": SUBAGENT_SYSTEM,
         "trigger_runner": TRIGGER_RUNNER_SYSTEM,
+        "intro_scene": INTRO_SCENE_SYSTEM,
     },
     # Russian keys kept for backward compatibility but always return the English
     # prompts — system content is always English per the project convention.
@@ -151,6 +181,7 @@ PROMPTS = {
         "summarizer": SUMMARIZER_SYSTEM,
         "subagent": SUBAGENT_SYSTEM,
         "trigger_runner": TRIGGER_RUNNER_SYSTEM,
+        "intro_scene": INTRO_SCENE_SYSTEM,
     },
 }
 
diff --git a/backend/app/schemas/__init__.py b/backend/app/schemas/__init__.py
index 0de50cd..3a74192 100644
--- a/backend/app/schemas/__init__.py
+++ b/backend/app/schemas/__init__.py
@@ -237,3 +237,15 @@ class TriggerCreate(BaseModel):
     fire_at: str
     description: str
     payload: Dict[str, Any] = Field(default_factory=dict)
+
+
+
+# === World Editor (AI-assisted editing of an existing world) ===
+class WorldEditorChatRequest(BaseModel):
+    message: str = Field(min_length=1, max_length=4000)
+
+
+class WorldEditorChatReply(BaseModel):
+    ai_message: str
+    definition: Optional[Dict[str, Any]] = None
+    changed: bool = False
diff --git a/frontend/index.html b/frontend/index.html
index 0dd4b7f..1ba4c7f 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -1,8 +1,9 @@
 <!doctype html>
-<html lang="ru">
+<html lang="en">
   <head>
     <meta charset="UTF-8" />
-    <link rel="icon" type="image/svg+xml" href="/vite.svg" />
+    <link rel="icon" type="image/png" href="/logo.png" />
+    <link rel="apple-touch-icon" href="/logo.png" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>AI RPG</title>
   </head>
diff --git a/frontend/public/logo.png b/frontend/public/logo.png
new file mode 100644
index 0000000..73039fc
Binary files /dev/null and b/frontend/public/logo.png differ
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index 6de96dd..99acaea 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -1,5 +1,7 @@
+import { useEffect } from "react";
 import { Routes, Route, Navigate } from "react-router-dom";
 import { useAuthStore } from "@/store/auth";
+import { useUiStore } from "@/store/ui";
 import { Navbar } from "@/components/ui/Navbar";
 import { HomePage } from "@/pages/HomePage";
 import { LoginPage } from "@/pages/LoginPage";
@@ -26,6 +28,15 @@ function AdminRoute({ children }: { children: JSX.Element }) {
 }
 
 export default function App() {
+  // Load public UI settings (logo URL, etc.) once on app boot. These are
+  // unauthenticated and cached by the api layer, so subsequent navigations
+  // do not re-fetch. The admin panel calls load(true) after saving to
+  // pick up a new logo URL without a full page reload.
+  const loadUi = useUiStore((s) => s.load);
+  useEffect(() => {
+    loadUi();
+  }, [loadUi]);
+
   return (
     <div className="min-h-screen flex flex-col">
       <Navbar />
diff --git a/frontend/src/api/index.ts b/frontend/src/api/index.ts
index 6fa0681..790ba04 100644
--- a/frontend/src/api/index.ts
+++ b/frontend/src/api/index.ts
@@ -229,4 +229,41 @@ export const miscApi = {
   },
 };
 
+// Public UI settings — no auth required. Used on login/register/home pages
+// to render branding (logo, eventually theme). Caches the result in-process
+// so multiple components can call getPublicSettings() without re-fetching.
+export type PublicUiSettings = {
+  logo_url?: string;
+};
+
+let _publicSettingsCache: PublicUiSettings | null = null;
+let _publicSettingsPromise: Promise<PublicUiSettings> | null = null;
+
+export const uiApi = {
+  /** Fetch public UI settings (logo URL, etc.). Cached after first call. */
+  getPublicSettings: async (force = false): Promise<PublicUiSettings> => {
+    if (_publicSettingsCache && !force) return _publicSettingsCache;
+    if (_publicSettingsPromise && !force) return _publicSettingsPromise;
+    _publicSettingsPromise = (async () => {
+      try {
+        const { data } = await api.get("/settings/public");
+        _publicSettingsCache = {
+          logo_url: data["ui.logo_url"] || "/logo.png",
+        };
+      } catch {
+        _publicSettingsCache = { logo_url: "/logo.png" };
+      } finally {
+        _publicSettingsPromise = null;
+      }
+      return _publicSettingsCache;
+    })();
+    return _publicSettingsPromise;
+  },
+  /** Reset the in-memory cache. Call after admin saves new ui.logo_url. */
+  resetCache: () => {
+    _publicSettingsCache = null;
+    _publicSettingsPromise = null;
+  },
+};
+
 export const SSE_ENDPOINT = "/api/sessions";
diff --git a/frontend/src/components/ui/Navbar.tsx b/frontend/src/components/ui/Navbar.tsx
index 81d4ad1..e3ef0d0 100644
--- a/frontend/src/components/ui/Navbar.tsx
+++ b/frontend/src/components/ui/Navbar.tsx
@@ -3,6 +3,7 @@ import { useTranslation } from "react-i18next";
 import { Link, useNavigate } from "react-router-dom";
 import { LogOut, Shield, Globe, BookOpen } from "lucide-react";
 import { useAuthStore } from "@/store/auth";
+import { useUiStore } from "@/store/ui";
 import { Button } from "./Button";
 import { cn } from "./cn";
 
@@ -11,6 +12,7 @@ export function Navbar() {
   const { user, logout, isAdmin } = useAuthStore();
   const navigate = useNavigate();
   const [langOpen, setLangOpen] = useState(false);
+  const logoUrl = useUiStore((s) => s.logoUrl);
 
   const handleLogout = () => {
     logout();
@@ -26,7 +28,21 @@ export function Navbar() {
     <header className="border-b border-ink-800 bg-ink-950/80 backdrop-blur sticky top-0 z-40">
       <div className="max-w-7xl mx-auto px-4 py-3 flex items-center justify-between">
         <Link to="/" className="flex items-center gap-2 text-ink-100 hover:text-accent-400 transition-colors">
-          <BookOpen size={20} className="text-accent-500" />
+          {logoUrl ? (
+            <img
+              src={logoUrl}
+              alt="logo"
+              className="w-7 h-7 rounded object-contain"
+              onError={(e) => {
+                // If the configured logo fails to load, hide the broken image
+                // so the navbar degrades gracefully. The bundled /logo.png is
+                // always available as the default fallback.
+                (e.currentTarget as HTMLImageElement).style.display = "none";
+              }}
+            />
+          ) : (
+            <BookOpen size={20} className="text-accent-500" />
+          )}
           <span className="font-serif text-lg font-semibold">{t("app.title")}</span>
         </Link>
 
diff --git a/frontend/src/i18n/en.ts b/frontend/src/i18n/en.ts
index ba0a8b2..32ba217 100644
--- a/frontend/src/i18n/en.ts
+++ b/frontend/src/i18n/en.ts
@@ -59,6 +59,14 @@ export const en = {
     send: "Send",
     accept: "Accept world and create",
     accepting: "Creating world...",
+    editor_chat_title: "AI chat",
+    editor_chat_desc: "Describe changes — the AI will update the world definition.",
+    editor_chat_empty: "Nothing yet. Tell the AI what to change.",
+    editor_chat_ph: "e.g. add a vampire faction in the south...",
+    editor_you: "You",
+    editor_pending_defn: "AI proposed a new definition.",
+    editor_apply: "Apply",
+    editor_reset: "Reset chat",
     status_draft: "Draft",
     status_ready: "Ready",
     status_active: "Active",
@@ -84,6 +92,7 @@ export const en = {
     no_messages: "Start with your first action!",
     new_session: "New session",
     error_iter: "Iteration failed",
+    retry: "Retry",
   },
   admin: {
     title: "Admin panel",
@@ -106,6 +115,12 @@ export const en = {
     trigger_settings_desc: "Fire when in-world time advances (no polling)",
     triggers_enabled: "Enabled",
     triggers_enabled_desc: "Triggers fire automatically inside the orchestrator when world time advances past their scheduled fire_at.",
+    ui_settings: "UI customization",
+    ui_settings_desc: "Branding shown to all users (logo, favicon).",
+    ui_logo_url: "Logo URL",
+    ui_logo_url_hint:
+      "Path (e.g. /logo.png), full URL (https://.../logo.png), or data: URI. Default /logo.png is the bundled Mikan logo. Used in navbar, home page, and browser tab.",
+    ui_logo_preview: "Preview",
     embedding_settings: "Embeddings (RAG)",
     embedding_provider: "Provider",
     embedding_provider_hash: "Hash (offline fallback, no semantics)",
diff --git a/frontend/src/i18n/ru.ts b/frontend/src/i18n/ru.ts
index 31e12fd..1fdf504 100644
--- a/frontend/src/i18n/ru.ts
+++ b/frontend/src/i18n/ru.ts
@@ -59,6 +59,14 @@ export const ru = {
     send: "Отправить",
     accept: "Принять мир и создать",
     accepting: "Создаём мир...",
+    editor_chat_title: "Чат с ИИ",
+    editor_chat_desc: "Опишите изменения — ИИ обновит определение мира.",
+    editor_chat_empty: "Пока пусто. Напишите, что изменить в мире.",
+    editor_chat_ph: "Например: добавь фракцию вампиров на юге...",
+    editor_you: "Вы",
+    editor_pending_defn: "ИИ предложил новое определение.",
+    editor_apply: "Применить",
+    editor_reset: "Сбросить диалог",
     status_draft: "Черновик",
     status_ready: "Готов",
     status_active: "Активен",
@@ -84,6 +92,7 @@ export const ru = {
     no_messages: "Начните с первого действия!",
     new_session: "Новая сессия",
     error_iter: "Ошибка при выполнении итерации",
+    retry: "Повторить",
   },
   admin: {
     title: "Панель администратора",
@@ -106,6 +115,12 @@ export const ru = {
     trigger_settings_desc: "Срабатывают при сдвиге внутриигрового времени (без поллинга)",
     triggers_enabled: "Включены",
     triggers_enabled_desc: "Триггеры срабатывают автоматически внутри оркестратора, когда время мира проходит запланированное fire_at.",
+    ui_settings: "Настройки интерфейса",
+    ui_settings_desc: "Брендинг, видимый всем пользователям (логотип, favicon).",
+    ui_logo_url: "URL логотипа",
+    ui_logo_url_hint:
+      "Путь (напр. /logo.png), полный URL (https://.../logo.png) или data: URI. По умолчанию /logo.png — встроенный логотип Mikan. Используется в навбаре, на главной и во вкладке браузера.",
+    ui_logo_preview: "Превью",
     embedding_settings: "Эмбеддинги (RAG)",
     embedding_provider: "Провайдер",
     embedding_provider_hash: "Hash (офлайн-фолбэк, без семантики)",
diff --git a/frontend/src/pages/AdminPanelPage.tsx b/frontend/src/pages/AdminPanelPage.tsx
index 349484a..c10ecb9 100644
--- a/frontend/src/pages/AdminPanelPage.tsx
+++ b/frontend/src/pages/AdminPanelPage.tsx
@@ -1,8 +1,9 @@
 import { useEffect, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useNavigate } from "react-router-dom";
-import { adminApi } from "@/api";
+import { adminApi, uiApi } from "@/api";
 import type { LlmLog, SettingsOut } from "@/types";
+import { useUiStore } from "@/store/ui";
 import { Button } from "@/components/ui/Button";
 import { Input } from "@/components/ui/Input";
 import { Card, CardBody, CardHeader } from "@/components/ui/Card";
@@ -63,6 +64,12 @@ export function AdminPanelPage() {
       setValues(s.values);
       setSaved(true);
       setTimeout(() => setSaved(false), 2000);
+      // If the admin changed the logo URL, refresh the public-UI cache so
+      // the navbar/favicon update live without a full page reload.
+      if ("ui.logo_url" in payload) {
+        uiApi.resetCache();
+        await useUiStore.getState().load(true);
+      }
     } catch (err: any) {
       setError(err.response?.data?.detail || t("errors.unknown"));
     } finally {
@@ -441,6 +448,40 @@ export function AdminPanelPage() {
             </CardBody>
           </Card>
 
+          <Card>
+            <CardHeader
+              title={t("admin.ui_settings")}
+              subtitle={t("admin.ui_settings_desc")}
+            />
+            <CardBody className="space-y-3">
+              <Input
+                label={t("admin.ui_logo_url")}
+                value={values["ui.logo_url"] || ""}
+                onChange={(e) => setValues({ ...values, "ui.logo_url": e.target.value })}
+                placeholder="/logo.png"
+              />
+              <p className="text-xs text-ink-500">{t("admin.ui_logo_url_hint")}</p>
+              {/* Live preview so the admin sees the configured logo before saving. */}
+              <div className="flex items-center gap-3 pt-1">
+                <span className="text-xs text-ink-400">{t("admin.ui_logo_preview")}:</span>
+                <div className="w-10 h-10 rounded border border-ink-700 bg-ink-900 flex items-center justify-center overflow-hidden">
+                  {values["ui.logo_url"] ? (
+                    <img
+                      src={values["ui.logo_url"]}
+                      alt="preview"
+                      className="w-8 h-8 object-contain"
+                      onError={(e) => {
+                        (e.currentTarget as HTMLImageElement).style.display = "none";
+                      }}
+                    />
+                  ) : (
+                    <span className="text-[10px] text-ink-500">—</span>
+                  )}
+                </div>
+              </div>
+            </CardBody>
+          </Card>
+
           <div className="flex justify-end gap-2">
             {saved && <span className="text-sm text-green-400 self-center">{t("admin.saved")}</span>}
             <Button onClick={save} disabled={saving}>
diff --git a/frontend/src/pages/HomePage.tsx b/frontend/src/pages/HomePage.tsx
index cdc465e..8e5ba1f 100644
--- a/frontend/src/pages/HomePage.tsx
+++ b/frontend/src/pages/HomePage.tsx
@@ -1,18 +1,38 @@
 import { useTranslation } from "react-i18next";
 import { Link } from "react-router-dom";
 import { useAuthStore } from "@/store/auth";
+import { useUiStore } from "@/store/ui";
 import { Button } from "@/components/ui/Button";
 import { BookOpen, Sparkles, Cog, Globe } from "lucide-react";
 
 export function HomePage() {
   const { t } = useTranslation();
   const { user } = useAuthStore();
+  const logoUrl = useUiStore((s) => s.logoUrl);
 
   return (
     <div className="max-w-5xl mx-auto px-4 py-12">
       <div className="text-center mb-12">
-        <div className="inline-flex items-center justify-center w-16 h-16 rounded-full bg-accent-500/10 border border-accent-500/30 mb-4">
-          <BookOpen className="text-accent-500" size={32} />
+        <div className="inline-flex items-center justify-center w-16 h-16 rounded-full bg-accent-500/10 border border-accent-500/30 mb-4 overflow-hidden">
+          {logoUrl ? (
+            <img
+              src={logoUrl}
+              alt="logo"
+              className="w-12 h-12 rounded object-contain"
+              onError={(e) => {
+                // Fall back to the BookOpen icon if the configured logo URL
+                // fails to load (e.g. typo in admin settings, dead link).
+                (e.currentTarget as HTMLImageElement).style.display = "none";
+                const sib = (e.currentTarget as HTMLImageElement).nextElementSibling as HTMLElement | null;
+                if (sib) sib.style.display = "block";
+              }}
+            />
+          ) : null}
+          <BookOpen
+            className="text-accent-500"
+            size={32}
+            style={{ display: logoUrl ? "none" : "block" }}
+          />
         </div>
         <h1 className="text-4xl font-serif font-bold text-ink-100 mb-3">{t("app.title")}</h1>
         <p className="text-ink-400 max-w-2xl mx-auto">{t("app.subtitle")}</p>
diff --git a/frontend/src/pages/SessionPage.tsx b/frontend/src/pages/SessionPage.tsx
index 2ad78ba..47949f7 100644
--- a/frontend/src/pages/SessionPage.tsx
+++ b/frontend/src/pages/SessionPage.tsx
@@ -11,7 +11,7 @@ import { Card, CardBody } from "@/components/ui/Card";
 import { Modal } from "@/components/ui/Modal";
 import { GlossaryModal } from "@/components/world/GlossaryModal";
 import { CharacterSheet } from "@/components/world/CharacterSheet";
-import { Send, BookOpen, User, Pencil, Clock, Zap, Loader2 } from "lucide-react";
+import { Send, BookOpen, User, Pencil, Clock, Zap, Loader2, RefreshCw } from "lucide-react";
 import ReactMarkdown from "react-markdown";
 
 export function SessionPage() {
@@ -28,6 +28,7 @@ export function SessionPage() {
   const [iterating, setIterating] = useState(false);
   const [status, setStatus] = useState<string>("");
   const [error, setError] = useState("");
+  const [lastFailedAction, setLastFailedAction] = useState<string | null>(null);
   const [glossaryOpen, setGlossaryOpen] = useState(false);
   const [glossary, setGlossary] = useState<GlossaryEntry[]>([]);
   const [triggers, setTriggers] = useState<Trigger[]>([]);
@@ -61,27 +62,105 @@ export function SessionPage() {
     messagesEndRef.current?.scrollIntoView({ behavior: "smooth" });
   }, [messages, status]);
 
-  const runIteration = async () => {
-    if (!id || !actionText.trim() || iterating) return;
+  // Auto-generate intro scene for fresh sessions (no messages yet).
+  const introTriggeredRef = useRef(false);
+  useEffect(() => {
+    if (!id || introTriggeredRef.current) return;
+    if (messages.length === 0 && !iterating && !error) {
+      introTriggeredRef.current = true;
+      runIntro();
+    }
+  }, [id, messages.length, iterating, error]);
+
+  const runIntro = async () => {
+    if (!id) return;
+    setIterating(true);
+    setStatus(t("session.status_writing_scene"));
     setError("");
+    try {
+      await fetchEventSource(`/api/sessions/${id}/intro`, {
+        method: "POST",
+        headers: {
+          "Content-Type": "application/json",
+          Authorization: `Bearer ${token}`,
+        },
+        body: JSON.stringify({ session_id: id }),
+        openWhenHidden: true,
+        onmessage(ev) {
+          const eventName = ev.event;
+          let data: any = {};
+          try { data = JSON.parse(ev.data || "{}"); } catch { data = {}; }
+          if (eventName === "status") {
+            const msg = data.message || "";
+            if (msg === "writing_scene") setStatus(t("session.status_writing_scene"));
+            else setStatus(msg);
+          } else if (eventName === "step_complete") {
+            const stepMsg: Message = {
+              id: data.message_id || `intro-${Date.now()}`,
+              seq: data.seq || 1,
+              role: "assistant",
+              kind: "narrative_step",
+              content: data.narrative || "",
+              payload: { options: data.options || [], world_time: data.world_time, kind: "intro" },
+              is_pinned: true,
+              hidden: false,
+              created_at: new Date().toISOString(),
+            };
+            setMessages((prev) => [...prev, stepMsg]);
+            if (world && data.world_time) {
+              setWorld({ ...world, current_time: data.world_time, state: data.state || world.state });
+            }
+          } else if (eventName === "error") {
+            setError(data.message || t("session.error_iter"));
+          }
+        },
+        onclose() {
+          setIterating(false);
+          setStatus("");
+        },
+        onerror(err) {
+          setIterating(false);
+          setStatus("");
+          setError(String(err) || t("session.error_iter"));
+          throw err;
+        },
+      });
+    } catch (err: any) {
+      setIterating(false);
+      setStatus("");
+      setError(err.message || t("session.error_iter"));
+    }
+  };
+
+  const runIteration = async (overrideAction?: string) => {
+    if (!id || iterating) return;
+    const rawAction = overrideAction ?? actionText;
+    if (!rawAction.trim()) return;
+    setError("");
+    setLastFailedAction(null);
     setIterating(true);
     setStatus(t("session.status_planning"));
-    const action = actionText.trim();
-    setActionText("");
+    const action = rawAction.trim();
+    if (overrideAction === undefined) setActionText("");
 
-    // Optimistic: show user action immediately
-    const optimisticUserMsg: Message = {
-      id: `tmp-${Date.now()}`,
-      seq: messages.length + 1,
-      role: "user",
-      kind: "player_action",
-      content: action,
-      payload: {},
-      is_pinned: true,
-      hidden: false,
-      created_at: new Date().toISOString(),
-    };
-    setMessages((prev) => [...prev, optimisticUserMsg]);
+    // Optimistic: show user action immediately (skip on retry if already shown)
+    const alreadyShown = messages.some(
+      (m) => m.kind === "player_action" && m.content === action && m.id?.startsWith("tmp-")
+    );
+    if (!alreadyShown) {
+      const optimisticUserMsg: Message = {
+        id: `tmp-${Date.now()}`,
+        seq: messages.length + 1,
+        role: "user",
+        kind: "player_action",
+        content: action,
+        payload: {},
+        is_pinned: true,
+        hidden: false,
+        created_at: new Date().toISOString(),
+      };
+      setMessages((prev) => [...prev, optimisticUserMsg]);
+    }
 
     try {
       await fetchEventSource(`/api/sessions/${id}/iterate`, {
@@ -132,6 +211,7 @@ export function SessionPage() {
             }
           } else if (eventName === "error") {
             setError(data.message || t("session.error_iter"));
+            setLastFailedAction(action);
           } else if (eventName === "done") {
             // Final reload to get fresh seq/order
             load();
@@ -147,6 +227,7 @@ export function SessionPage() {
           setIterating(false);
           setStatus("");
           setError(String(err) || t("session.error_iter"));
+          setLastFailedAction(action);
           throw err; // stop retry
         },
       });
@@ -237,27 +318,45 @@ export function SessionPage() {
                 ))}
               </div>
             )}
-            <div className="flex gap-2">
-              <Textarea
-                value={actionText}
-                onChange={(e) => setActionText(e.target.value)}
-                placeholder={t("session.action_placeholder")}
-                disabled={iterating}
-                rows={2}
-                className="min-h-[44px]"
-                onKeyDown={(e) => {
-                  if (e.key === "Enter" && (e.ctrlKey || e.metaKey)) {
-                    e.preventDefault();
-                    runIteration();
-                  }
-                }}
-              />
-              <Button onClick={runIteration} disabled={iterating || !actionText.trim()} className="self-end">
-                <Send size={14} className="mr-1" />
-                {iterating ? t("session.sending") : t("session.send")}
-              </Button>
-            </div>
-            {error && <p className="text-xs text-red-400">{error}</p>}
+            {lastFailedAction ? (
+              <div className="flex gap-2 items-center">
+                <div className="flex-1 text-sm text-red-300 bg-red-950/40 border border-red-800/60 rounded-lg px-3 py-2">
+                  {error || t("session.error_iter")}
+                </div>
+                <Button
+                  variant="secondary"
+                  onClick={() => runIteration(lastFailedAction)}
+                  disabled={iterating}
+                  className="self-end"
+                >
+                  <Loader2 className={iterating ? "animate-spin mr-1" : "hidden"} size={14} />
+                  {!iterating && <RefreshCw size={14} className="mr-1" />}
+                  {iterating ? t("session.sending") : t("session.retry")}
+                </Button>
+              </div>
+            ) : (
+              <div className="flex gap-2">
+                <Textarea
+                  value={actionText}
+                  onChange={(e) => setActionText(e.target.value)}
+                  placeholder={t("session.action_placeholder")}
+                  disabled={iterating}
+                  rows={2}
+                  className="min-h-[44px]"
+                  onKeyDown={(e) => {
+                    if (e.key === "Enter" && (e.ctrlKey || e.metaKey)) {
+                      e.preventDefault();
+                      runIteration();
+                    }
+                  }}
+                />
+                <Button onClick={() => runIteration()} disabled={iterating || !actionText.trim()} className="self-end">
+                  <Send size={14} className="mr-1" />
+                  {iterating ? t("session.sending") : t("session.send")}
+                </Button>
+              </div>
+            )}
+            {error && !lastFailedAction && <p className="text-xs text-red-400">{error}</p>}
           </div>
         </div>
 
diff --git a/frontend/src/pages/WorldEditPage.tsx b/frontend/src/pages/WorldEditPage.tsx
index c886735..a550b50 100644
--- a/frontend/src/pages/WorldEditPage.tsx
+++ b/frontend/src/pages/WorldEditPage.tsx
@@ -1,29 +1,54 @@
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useNavigate, useParams } from "react-router-dom";
+import axios from "axios";
 import { worldsApi, sessionsApi } from "@/api";
+import { useAuthStore } from "@/store/auth";
 import type { World } from "@/types";
 import { Button } from "@/components/ui/Button";
+import { Input, Textarea } from "@/components/ui/Input";
 import { Card, CardBody, CardHeader } from "@/components/ui/Card";
-import { Play } from "lucide-react";
+import { Play, Save, RotateCcw, Send, Sparkles, Loader2 } from "lucide-react";
+
+interface EditorChatMessage {
+  role: "user" | "assistant";
+  text: string;
+}
+
+interface ChatReply {
+  ai_message: string;
+  definition: Record<string, any> | null;
+  changed: boolean;
+}
 
 export function WorldEditPage() {
   const { t } = useTranslation();
   const { id } = useParams<{ id: string }>();
   const navigate = useNavigate();
+  const { token } = useAuthStore();
+
   const [world, setWorld] = useState<World | null>(null);
+  const [name, setName] = useState("");
   const [definitionText, setDefinitionText] = useState("");
   const [stateText, setStateText] = useState("");
   const [loading, setLoading] = useState(true);
   const [saving, setSaving] = useState(false);
   const [error, setError] = useState("");
 
+  // AI chat state
+  const [chatMessages, setChatMessages] = useState<EditorChatMessage[]>([]);
+  const [chatInput, setChatInput] = useState("");
+  const [chatLoading, setChatLoading] = useState(false);
+  const [pendingDefinition, setPendingDefinition] = useState<Record<string, any> | null>(null);
+  const chatScrollRef = useRef<HTMLDivElement>(null);
+
   useEffect(() => {
     (async () => {
       if (!id) return;
       try {
         const w = await worldsApi.get(id);
         setWorld(w);
+        setName(w.name);
         setDefinitionText(JSON.stringify(w.definition, null, 2));
         setStateText(JSON.stringify(w.state, null, 2));
       } catch (err: any) {
@@ -34,6 +59,10 @@ export function WorldEditPage() {
     })();
   }, [id]);
 
+  useEffect(() => {
+    chatScrollRef.current?.scrollIntoView({ behavior: "smooth" });
+  }, [chatMessages, chatLoading]);
+
   const save = async () => {
     if (!id || !world) return;
     setError("");
@@ -42,14 +71,18 @@ export function WorldEditPage() {
       const definition = JSON.parse(definitionText);
       const state = JSON.parse(stateText);
       const updated = await worldsApi.update(id, {
+        name,
         definition,
         state,
         current_time: world.current_time,
         status: world.status === "draft" ? "ready" : world.status,
       });
       setWorld(updated);
+      // Reset chat (definition changed -> stale context)
+      setChatMessages([]);
+      setPendingDefinition(null);
     } catch (err: any) {
-      setError(err.message || t("errors.unknown"));
+      setError(err.message || err.response?.data?.detail || t("errors.unknown"));
     } finally {
       setSaving(false);
     }
@@ -65,13 +98,58 @@ export function WorldEditPage() {
     }
   };
 
+  const sendChatMessage = async () => {
+    if (!id || !chatInput.trim() || chatLoading) return;
+    const msg = chatInput.trim();
+    setChatInput("");
+    setChatMessages((prev) => [...prev, { role: "user", text: msg }]);
+    setChatLoading(true);
+    setError("");
+    try {
+      const { data } = await axios.post<ChatReply>(
+        `/api/worlds/${id}/chat`,
+        { message: msg },
+        { headers: { "Content-Type": "application/json", Authorization: `Bearer ${token}` } }
+      );
+      setChatMessages((prev) => [...prev, { role: "assistant", text: data.ai_message }]);
+      if (data.definition) {
+        setPendingDefinition(data.definition);
+        setDefinitionText(JSON.stringify(data.definition, null, 2));
+      }
+    } catch (err: any) {
+      const detail = err.response?.data?.detail || err.message || t("errors.unknown");
+      setChatMessages((prev) => [...prev, { role: "assistant", text: `⚠️ ${detail}` }]);
+    } finally {
+      setChatLoading(false);
+    }
+  };
+
+  const resetChat = async () => {
+    if (!id) return;
+    try {
+      await axios.post(`/api/worlds/${id}/chat/reset`, {}, {
+        headers: { Authorization: `Bearer ${token}` },
+      });
+      setChatMessages([]);
+      setPendingDefinition(null);
+    } catch (err: any) {
+      setError(err.response?.data?.detail || t("errors.unknown"));
+    }
+  };
+
+  const applyPendingDefinition = () => {
+    if (!pendingDefinition) return;
+    setDefinitionText(JSON.stringify(pendingDefinition, null, 2));
+    setPendingDefinition(null);
+  };
+
   if (loading) return <div className="p-8 text-center text-ink-400">{t("common.loading")}</div>;
   if (!world) return <div className="p-8 text-center text-red-400">{error || t("common.not_found")}</div>;
 
   return (
-    <div className="max-w-5xl mx-auto px-4 py-6">
-      <div className="flex items-center justify-between mb-4">
-        <h1 className="text-xl font-serif text-ink-100">
+    <div className="max-w-7xl mx-auto px-4 py-6">
+      <div className="flex items-center justify-between mb-4 gap-2">
+        <h1 className="text-xl font-serif text-ink-100 flex-1 min-w-0 truncate">
           {t("worlds.edit")}: {world.name}
         </h1>
         <div className="flex gap-2">
@@ -87,29 +165,131 @@ export function WorldEditPage() {
 
       {error && <p className="text-sm text-red-400 mb-4">{error}</p>}
 
-      <div className="grid grid-cols-1 lg:grid-cols-2 gap-4">
-        <Card>
-          <CardHeader title="World definition (JSON)" subtitle="setting, rules, schema, plot_rails, initial_state" />
-          <CardBody>
-            <textarea
-              value={definitionText}
-              onChange={(e) => setDefinitionText(e.target.value)}
-              className="w-full h-[60vh] px-3 py-2 rounded bg-ink-950 border border-ink-700 text-ink-100 font-mono text-xs"
-              spellCheck={false}
-            />
-          </CardBody>
-        </Card>
-        <Card>
-          <CardHeader title="Live world state (JSON)" subtitle="current player/NPC/inventory/time" />
-          <CardBody>
-            <textarea
-              value={stateText}
-              onChange={(e) => setStateText(e.target.value)}
-              className="w-full h-[60vh] px-3 py-2 rounded bg-ink-950 border border-ink-700 text-ink-100 font-mono text-xs"
-              spellCheck={false}
+      {/* World name row */}
+      <Card className="mb-4">
+        <CardHeader title={t("worlds.name")} />
+        <CardBody>
+          <div className="flex gap-2 items-center">
+            <Input
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              className="flex-1"
             />
+            <Button onClick={save} disabled={saving || !name.trim()}>
+              {saving ? <Loader2 size={14} className="animate-spin mr-1" /> : <Save size={14} className="mr-1" />}
+              {saving ? t("common.loading") : t("common.save")}
+            </Button>
+          </div>
+        </CardBody>
+      </Card>
+
+      <div className="grid grid-cols-1 lg:grid-cols-3 gap-4">
+        {/* AI chat panel (1 col) */}
+        <Card className="lg:col-span-1 flex flex-col">
+          <CardHeader
+            title={
+              <span className="flex items-center gap-2">
+                <Sparkles size={14} className="text-accent-400" />
+                {t("worlds.editor_chat_title")}
+              </span> as any
+            }
+            subtitle={t("worlds.editor_chat_desc")}
+          />
+          <CardBody className="flex-1 flex flex-col min-h-0">
+            <div className="flex-1 overflow-y-auto space-y-3 mb-3 max-h-[55vh]">
+              {chatMessages.length === 0 && (
+                <div className="text-xs text-ink-500 italic text-center py-6">
+                  {t("worlds.editor_chat_empty")}
+                </div>
+              )}
+              {chatMessages.map((m, i) => (
+                <div key={i} className={`flex ${m.role === "user" ? "justify-end" : "justify-start"}`}>
+                  <div
+                    className={`max-w-[90%] rounded-xl p-2.5 text-xs whitespace-pre-wrap ${
+                      m.role === "user"
+                        ? "bg-accent-500/20 border border-accent-500/40 text-ink-100"
+                        : "bg-ink-800 border border-ink-700 text-ink-100"
+                    }`}
+                  >
+                    <div className="text-[10px] text-ink-400 mb-1">
+                      {m.role === "user" ? t("worlds.editor_you") : "AI"}
+                    </div>
+                    {m.text}
+                  </div>
+                </div>
+              ))}
+              {chatLoading && (
+                <div className="flex justify-start">
+                  <div className="bg-ink-800 border border-ink-700 rounded-xl p-2.5 text-ink-400 text-xs pulse-soft flex items-center gap-2">
+                    <Loader2 size={12} className="animate-spin" />
+                    {t("common.loading")}
+                  </div>
+                </div>
+              )}
+              <div ref={chatScrollRef} />
+            </div>
+
+            {pendingDefinition && (
+              <div className="mb-3 p-2 rounded-lg bg-accent-500/10 border border-accent-500/40 text-xs text-accent-200 flex items-center justify-between gap-2">
+                <span>{t("worlds.editor_pending_defn")}</span>
+                <Button size="sm" variant="secondary" onClick={applyPendingDefinition}>
+                  {t("worlds.editor_apply")}
+                </Button>
+              </div>
+            )}
+
+            <div className="flex gap-2">
+              <Textarea
+                value={chatInput}
+                onChange={(e) => setChatInput(e.target.value)}
+                placeholder={t("worlds.editor_chat_ph")}
+                disabled={chatLoading}
+                rows={2}
+                className="min-h-[60px] flex-1"
+                onKeyDown={(e) => {
+                  if (e.key === "Enter" && (e.ctrlKey || e.metaKey)) {
+                    e.preventDefault();
+                    sendChatMessage();
+                  }
+                }}
+              />
+              <div className="flex flex-col gap-1">
+                <Button size="sm" onClick={sendChatMessage} disabled={chatLoading || !chatInput.trim()}>
+                  <Send size={14} />
+                </Button>
+                <Button size="sm" variant="ghost" onClick={resetChat} disabled={chatLoading} title={t("worlds.editor_reset")}>
+                  <RotateCcw size={14} />
+                </Button>
+              </div>
+            </div>
           </CardBody>
         </Card>
+
+        {/* JSON editors (2 cols) */}
+        <div className="lg:col-span-2 grid grid-cols-1 md:grid-cols-2 gap-4">
+          <Card>
+            <CardHeader title="World definition (JSON)" subtitle="setting, rules, schema, plot_rails, initial_state" />
+            <CardBody>
+              <textarea
+                value={definitionText}
+                onChange={(e) => setDefinitionText(e.target.value)}
+                className="w-full h-[55vh] px-3 py-2 rounded bg-ink-950 border border-ink-700 text-ink-100 font-mono text-xs"
+                spellCheck={false}
+              />
+            </CardBody>
+          </Card>
+          <Card>
+            <CardHeader title="Live world state (JSON)" subtitle="current player/NPC/inventory/time" />
+            <CardBody>
+              <textarea
+                value={stateText}
+                onChange={(e) => setStateText(e.target.value)}
+                className="w-full h-[55vh] px-3 py-2 rounded bg-ink-950 border border-ink-700 text-ink-100 font-mono text-xs"
+                spellCheck={false}
+              />
+            </CardBody>
+          </Card>
+        </div>
       </div>
 
       <div className="mt-4 flex justify-end gap-2">
diff --git a/frontend/src/store/ui.ts b/frontend/src/store/ui.ts
new file mode 100644
index 0000000..d792780
--- /dev/null
+++ b/frontend/src/store/ui.ts
@@ -0,0 +1,38 @@
+import { create } from "zustand";
+import { uiApi, type PublicUiSettings } from "@/api";
+
+interface UiState {
+  /** Logo URL (or path) to show in navbar, home page, and favicon. */
+  logoUrl: string;
+  /** True while the public UI settings are being fetched for the first time. */
+  loading: boolean;
+  /** Loads public UI settings from /api/settings/public (cached in api layer). */
+  load: (force?: boolean) => Promise<void>;
+}
+
+const DEFAULT_LOGO_URL = "/logo.png";
+
+export const useUiStore = create<UiState>((set) => ({
+  logoUrl: DEFAULT_LOGO_URL,
+  loading: false,
+  load: async (force = false) => {
+    set({ loading: true });
+    try {
+      const s: PublicUiSettings = await uiApi.getPublicSettings(force);
+      const next = s.logo_url || DEFAULT_LOGO_URL;
+      set({ logoUrl: next, loading: false });
+      // Dynamically update the document favicon so a custom logo is reflected
+      // in the browser tab without a page reload.
+      try {
+        const existing = document.querySelector<HTMLLinkElement>('link[rel="icon"]');
+        if (existing && existing.href !== next) {
+          existing.href = next;
+        }
+      } catch {
+        // ignore — DOM might not be ready during SSR/early hydration
+      }
+    } catch {
+      set({ logoUrl: DEFAULT_LOGO_URL, loading: false });
+    }
+  },
+}));
diff --git a/frontend/tsconfig.check.json b/frontend/tsconfig.check.json
new file mode 100644
index 0000000..b8651b7
--- /dev/null
+++ b/frontend/tsconfig.check.json
@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "jsx": "react-jsx",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true,
+    "baseUrl": ".",
+    "paths": { "@/*": ["src/*"] },
+    "typeRoots": ["/tmp/ts-check/node_modules/@types"]
+  },
+  "include": ["src/**/*.ts", "src/**/*.tsx"]
+}