diff --git a/AI_REFACTOR_PLAN.md b/AI_REFACTOR_PLAN.md
index 3da1ac0..9781fe2 100644
--- a/AI_REFACTOR_PLAN.md
+++ b/AI_REFACTOR_PLAN.md
@@ -248,6 +248,8 @@ Tools must use **camelCase** field names (Drizzle maps them to snake_case intern
 > **Objective:** Backend manages all agent configuration, scheduling, orchestration, and cloud data fetching. Two agent types: **Local Directory Agent** (backend triggers Electron to read files, then AI analyzes) and **Cloud Connector Agent** (backend fetches Gmail/Teams data directly, AI analyzes, pushes results to Electron via WS tool_call). All extracted items use existing WS tool infrastructure to insert into Electron's local DB with `is_ai_suggested=True`.
 >
 > **Electron Phase 3 plan:** `../adiuva/AI_REFACTOR_PLAN.md` Phase 3 section.
+>
+> **Electron UI status (2025):** Steps 3.6, 3.7, 3.8 of the Electron plan are ✅ complete. Agents are configured inside the Settings page (`/settings?section=agents`) — not a standalone route. The `JourneyDialog` (Step 3.8) is embedded inline in the Settings → Agents section. `LocalAgentConfigPanel` and `CloudAgentConfigPanel` (Step 3.7) are also inline. This affects the journey API contract (see Step 3.5 below).
 
 ### Architecture
 
@@ -412,22 +414,27 @@ Cloud Agent:
 - **Outcome:** Backend drives all agent execution — both local (via WS file request) and cloud (direct API calls — stub until Step 3.6).
 
 ### Step 3.5 — Chatbot Journey endpoint
-- [ ] Create `app/api/routes/agent_setup.py`:
+- [x] Create `app/api/routes/agent_setup.py`:
   - `POST /api/v1/agents/journey/start`:
-    - Body: `{ agent_type: "local"|"cloud", data_types: ["tasks", "notes", ...] }`
+    - Body: `{ agent_type: "local"|"cloud", agent_id: str | None }`
+      - `agent_type`: which kind of agent this journey configures.
+      - `agent_id`: optional — if provided, the session is pre-seeded with the existing agent's `prompt_template` so the user can refine it. If absent, fresh journey.
+      - **No `data_types` field** — data types are determined through the conversation itself, not sent upfront.
     - Creates a journey session (in-memory or Redis-backed)
     - Returns first AI message: contextual question based on agent type
       - Local: "What kind of files are in the directories you want to monitor? (emails, documents, logs, etc.)"
       - Cloud: "What kind of emails/messages should I look for? (client communications, invoices, meeting notes, etc.)"
     - Response: `{ session_id, message, done: false }`
+    - **Electron note:** `proxyPost` auto-converts camelCase keys to snake_case. Electron sends `{ agentType, agentId }` → backend receives `{ agent_type, agent_id }`.
   - `POST /api/v1/agents/journey/message`:
     - Body: `{ session_id, message }`
     - AI processes user's answer, asks follow-up questions (max 5 turns)
     - System prompt: "You are configuring a data extraction agent for a freelancer. Ask about file format, what data to extract (tasks, notes, checkpoints), naming conventions, priority rules, and any special mapping. After 3-5 questions, generate a detailed prompt_template."
     - When AI determines enough context: `{ session_id, message: "Here's your configuration...", done: true, prompt_template: "..." }`
     - The `prompt_template` is a structured instruction for the extraction LLM (e.g. "Extract tasks from email. Subject becomes task title. If body contains 'urgent' or 'ASAP', set priority to 'high'. Extract due dates if mentioned.")
+    - **Electron note:** `toCamelCase` converts the response → Electron reads `promptTemplate` from the final message and auto-fills the agent config panel. User clicks "Save & apply" which calls `agent.local.update` / `agent.cloud.update` tRPC mutation.
 - **Files:** `app/api/routes/agent_setup.py`, `app/main.py`
-- **Outcome:** Users configure AI prompts through guided conversation, not manual text editing.
+- **Outcome:** Users configure AI prompts through guided conversation. Journey can refine an existing config when `agent_id` is provided. ✅
 
 ### Step 3.6 — Cloud provider integrations
 - [ ] Create `app/integrations/gmail.py`:
diff --git a/app/api/routes/agent_setup.py b/app/api/routes/agent_setup.py
new file mode 100644
index 0000000..2cc755a
--- /dev/null
+++ b/app/api/routes/agent_setup.py
@@ -0,0 +1,317 @@
+"""Chatbot Journey endpoints — guided conversation to build an agent prompt_template.
+
+Endpoints:
+  POST /agents/journey/start    — start a new journey session
+  POST /agents/journey/message  — continue the conversation
+
+Sessions are stored in-memory with a 30-minute TTL.  Stale entries are
+cleaned up lazily on access.  Upgrade to Redis for multi-instance deployments.
+
+Journey flow:
+  1. Client sends ``{ agent_type, agent_id? }`` to ``/start``.
+  2. Server creates a session, calls the LLM with a contextual system prompt,
+     and returns the first question.
+  3. Client sends follow-up messages to ``/message``.
+  4. After 3-5 turns the LLM wraps up by emitting a ``prompt_template`` block
+     delimited by ``PROMPT_TEMPLATE_START`` / ``PROMPT_TEMPLATE_END``.
+  5. Server parses the block, sets ``done=True``, and returns the template.
+
+The ``prompt_template`` from the final response is meant to be stored in
+``LocalAgentConfig.prompt_template`` or ``CloudAgentConfig.prompt_template``
+by the Electron client (via the agent CRUD endpoints).
+"""
+
+from __future__ import annotations
+
+import logging
+import time
+import uuid
+from dataclasses import dataclass, field
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from langchain_core.messages import AIMessage, HumanMessage, SystemMessage
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.api.deps import get_current_user
+from app.core.llm import get_llm
+from app.db import get_session
+from app.models import CloudAgentConfig, LocalAgentConfig
+from app.schemas import (
+    JourneyMessageRequest,
+    JourneyResponse,
+    JourneyStartRequest,
+    UserProfile,
+)
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/agents/journey", tags=["agents"])
+
+# ── Session TTL ───────────────────────────────────────────────────────────
+
+_SESSION_TTL_SECONDS: int = 1800  # 30 minutes
+
+# Sentinel strings used to delimit the LLM-produced prompt_template.
+_TEMPLATE_START = "PROMPT_TEMPLATE_START"
+_TEMPLATE_END = "PROMPT_TEMPLATE_END"
+
+# Maximum number of conversation turns before the LLM is nudged to wrap up.
+_MAX_TURNS: int = 5
+
+# ── In-memory session store ───────────────────────────────────────────────
+
+
+@dataclass
+class _JourneySession:
+    session_id: str
+    user_id: str
+    agent_type: str  # "local" | "cloud"
+    history: list[dict[str, Any]] = field(default_factory=list)
+    created_at: float = field(default_factory=time.monotonic)
+
+    def is_expired(self) -> bool:
+        return (time.monotonic() - self.created_at) > _SESSION_TTL_SECONDS
+
+
+# session_id → session
+_sessions: dict[str, _JourneySession] = {}
+
+
+def _get_session(session_id: str, user_id: str) -> _JourneySession:
+    """Retrieve session; raise 404 on missing, expired, or wrong owner."""
+    s = _sessions.get(session_id)
+    if s is None or s.is_expired():
+        _sessions.pop(session_id, None)
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Journey session not found or expired")
+    if s.user_id != user_id:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Journey session not found or expired")
+    return s
+
+
+# ── System prompt builder ─────────────────────────────────────────────────
+
+_LOCAL_PREAMBLE = """\
+What kind of files are in the directories you want to monitor? \
+(for example: emails saved as .eml, documents in .pdf or .txt, markdown notes, etc.)"""
+
+_CLOUD_PREAMBLE = """\
+What kind of emails or messages should I look for? \
+(for example: client communications, invoices, meeting notes, project updates, etc.)"""
+
+_SYSTEM_PROMPT_TEMPLATE = """\
+You are a friendly assistant helping a freelancer configure a data-extraction agent.
+Your job is to understand exactly what data the user wants to extract from their {source_description} \
+and produce a detailed prompt_template that a separate AI will use as its instruction set.
+
+Ask concise, focused questions one at a time.  Cover these topics (not necessarily in this order):
+  1. The type and format of the source content.
+  2. Which data types to extract: tasks, notes, checkpoints, and/or projects.
+  3. How fields should be mapped (e.g. email subject → task title).
+  4. Priority or status rules (e.g. "urgent" keyword → high priority).
+  5. Any special handling, date extraction, or exclusions.
+
+After 3-5 questions (when you have enough information), output the final prompt_template between \
+these exact markers on their own lines:
+
+{template_start}
+<the complete extraction prompt here>
+{template_end}
+
+The prompt_template must be a self-contained instruction for an AI that receives a document/email/message \
+and must return a JSON array of records in this shape:
+  [{{ "table": "<tasks|notes|checkpoints|projects>", "data": {{ <field: value> }} }}, ...]
+
+Rules for the generated template:
+  - Be explicit about field names (camelCase: title, status, priority, dueDate, projectId, content, etc.).
+  - Include concrete examples of mappings.
+  - Mention that Electron adds id/createdAt/updatedAt automatically.
+  - Set isAiSuggested: true and isApproved: false on every record.
+{existing_section}\
+Do not ask more than {max_turns} questions total. Start with your first question now.\
+"""
+
+
+def _build_system_prompt(agent_type: str, existing_template: str | None) -> str:
+    source_description = (
+        "files in local directories" if agent_type == "local" else "emails and messages from cloud providers"
+    )
+    existing_section = (
+        f"\nThe user already has the following prompt_template — refine it based on their answers:\n"
+        f"---\n{existing_template}\n---\n"
+        if existing_template
+        else ""
+    )
+    return _SYSTEM_PROMPT_TEMPLATE.format(
+        source_description=source_description,
+        template_start=_TEMPLATE_START,
+        template_end=_TEMPLATE_END,
+        existing_section=existing_section,
+        max_turns=_MAX_TURNS,
+    )
+
+
+def _first_question(agent_type: str) -> str:
+    return _LOCAL_PREAMBLE if agent_type == "local" else _CLOUD_PREAMBLE
+
+
+# ── Template extraction ───────────────────────────────────────────────────
+
+
+def _extract_template(text: str) -> str | None:
+    """Return the text between PROMPT_TEMPLATE_START and PROMPT_TEMPLATE_END, or None."""
+    if _TEMPLATE_START not in text or _TEMPLATE_END not in text:
+        return None
+    start_idx = text.index(_TEMPLATE_START) + len(_TEMPLATE_START)
+    end_idx = text.index(_TEMPLATE_END)
+    return text[start_idx:end_idx].strip() or None
+
+
+# ── LLM call ─────────────────────────────────────────────────────────────
+
+
+async def _call_llm(system_prompt: str, history: list[dict[str, Any]]) -> str:
+    """Build LangChain messages from history and invoke the LLM."""
+    messages: list[Any] = [SystemMessage(content=system_prompt)]
+    for turn in history:
+        if turn["role"] == "user":
+            messages.append(HumanMessage(content=turn["content"]))
+        else:
+            messages.append(AIMessage(content=turn["content"]))
+
+    llm = get_llm(model=None, temperature=0.4)
+    response = await llm.ainvoke(messages)
+    return response.content  # type: ignore[return-value]
+
+
+# ── Existing-config loader ────────────────────────────────────────────────
+
+
+async def _load_existing_template(
+    agent_id: str,
+    user_id: str,
+    db: AsyncSession,
+) -> str | None:
+    """Return the prompt_template of an existing agent config, or None."""
+    # Try local first, then cloud.
+    local_result = await db.execute(
+        select(LocalAgentConfig).where(
+            LocalAgentConfig.id == agent_id,
+            LocalAgentConfig.user_id == user_id,
+        )
+    )
+    local = local_result.scalar_one_or_none()
+    if local is not None:
+        return local.prompt_template
+
+    cloud_result = await db.execute(
+        select(CloudAgentConfig).where(
+            CloudAgentConfig.id == agent_id,
+            CloudAgentConfig.user_id == user_id,
+        )
+    )
+    cloud = cloud_result.scalar_one_or_none()
+    return cloud.prompt_template if cloud is not None else None
+
+
+# ── Routes ────────────────────────────────────────────────────────────────
+
+
+@router.post("/start", response_model=JourneyResponse, status_code=status.HTTP_200_OK)
+async def start_journey(
+    body: JourneyStartRequest,
+    current_user: UserProfile = Depends(get_current_user),
+    db: AsyncSession = Depends(get_session),
+) -> JourneyResponse:
+    """Start a new Chatbot Journey session.
+
+    If ``agent_id`` is provided the session is pre-seeded with the existing
+    agent's ``prompt_template`` so the user can refine it.
+    """
+    # Load existing template (may be None).
+    existing_template: str | None = None
+    if body.agent_id:
+        existing_template = await _load_existing_template(body.agent_id, current_user.id, db)
+        # If agent_id was given but not found, proceed without seeding (don't 404 —
+        # the user may be starting a fresh journey for a not-yet-persisted config).
+
+    system_prompt = _build_system_prompt(body.agent_type, existing_template)
+    first_question = _first_question(body.agent_type)
+
+    session_id = str(uuid.uuid4())
+    session = _JourneySession(
+        session_id=session_id,
+        user_id=current_user.id,
+        agent_type=body.agent_type,
+        # Seed history with the AI's first question so it stays consistent.
+        history=[{"role": "assistant", "content": first_question}],
+    )
+    # Store the system prompt inside the session for reuse in /message.
+    session.__dict__["_system_prompt"] = system_prompt  # type: ignore[index]
+    _sessions[session_id] = session
+
+    logger.info("Journey session %s started for user %s (agent_type=%s)", session_id, current_user.id, body.agent_type)
+    return JourneyResponse(session_id=session_id, message=first_question, done=False)
+
+
+@router.post("/message", response_model=JourneyResponse, status_code=status.HTTP_200_OK)
+async def send_journey_message(
+    body: JourneyMessageRequest,
+    current_user: UserProfile = Depends(get_current_user),
+    db: AsyncSession = Depends(get_session),
+) -> JourneyResponse:
+    """Send a message in an existing Chatbot Journey session.
+
+    The server appends the user's message to the conversation history,
+    calls the LLM, and appends the AI reply.  When the LLM wraps up with a
+    ``prompt_template`` block the response includes ``done=True`` and the
+    extracted template.
+    """
+    session = _get_session(body.session_id, current_user.id)
+    system_prompt: str = session.__dict__.get("_system_prompt", _build_system_prompt(session.agent_type, None))  # type: ignore[assignment]
+
+    # Append user turn to history.
+    session.history.append({"role": "user", "content": body.message})
+
+    # Call the LLM with the full conversation so far.
+    ai_reply = await _call_llm(system_prompt, session.history)
+
+    # Append AI turn.
+    session.history.append({"role": "assistant", "content": ai_reply})
+
+    # Check if the LLM produced the final template.
+    prompt_template = _extract_template(ai_reply)
+    done = prompt_template is not None
+
+    # Strip the sentinel markers from the message shown to the user.
+    display_message = ai_reply
+    if done:
+        display_message = (
+            ai_reply[: ai_reply.index(_TEMPLATE_START)].strip()
+            or "Here is your agent configuration. You can save it or continue refining."
+        )
+
+    if done:
+        logger.info("Journey session %s completed for user %s", body.session_id, current_user.id)
+        # Clean up the session immediately on completion.
+        _sessions.pop(body.session_id, None)
+    else:
+        # Nudge the LLM to wrap up after max turns.
+        turns = sum(1 for t in session.history if t["role"] == "user")
+        if turns >= _MAX_TURNS:
+            # Add a system-level nudge as a hidden user message.
+            session.history.append({
+                "role": "user",
+                "content": (
+                    "[System: You have enough information. Please generate the final "
+                    f"prompt_template now, wrapped in {_TEMPLATE_START} / {_TEMPLATE_END} markers.]"
+                ),
+            })
+
+    return JourneyResponse(
+        session_id=body.session_id,
+        message=display_message,
+        done=done,
+        prompt_template=prompt_template,
+    )
diff --git a/app/main.py b/app/main.py
index 8bec4bb..e3303ce 100644
--- a/app/main.py
+++ b/app/main.py
@@ -43,7 +43,7 @@ def create_app() -> FastAPI:
     app.add_middleware(SanitizerMiddleware)
     app.add_middleware(TierRateLimitMiddleware)
 
-    from app.api.routes import agents, auth, backup, billing, chat, device_ws, plans, plugins, storage, vectors
+    from app.api.routes import agent_setup, agents, auth, backup, billing, chat, device_ws, plans, plugins, storage, vectors
 
     app.include_router(auth.router,       prefix="/api/v1")
     app.include_router(chat.router,       prefix="/api/v1")
@@ -54,6 +54,7 @@ def create_app() -> FastAPI:
     app.include_router(plugins.router,    prefix="/api/v1")
     app.include_router(billing.router,    prefix="/api/v1")
     app.include_router(agents.router,     prefix="/api/v1")
+    app.include_router(agent_setup.router, prefix="/api/v1")
     app.include_router(device_ws.router,  prefix="/api/v1")
 
     @app.get("/api/v1/health", tags=["health"])
diff --git a/app/schemas.py b/app/schemas.py
index 997955e..8ec4075 100644
--- a/app/schemas.py
+++ b/app/schemas.py
@@ -347,3 +347,22 @@ class AgentRunLogResponse(BaseModel):
     errors: list[str]
     started_at: int
     completed_at: int | None
+
+
+# ── Chatbot Journey ───────────────────────────────────────────────────
+
+class JourneyStartRequest(BaseModel):
+    agent_type: Literal["local", "cloud"]
+    agent_id: str | None = None
+
+
+class JourneyMessageRequest(BaseModel):
+    session_id: str
+    message: str
+
+
+class JourneyResponse(BaseModel):
+    session_id: str
+    message: str
+    done: bool
+    prompt_template: str | None = None
diff --git a/tests/test_agent_setup.py b/tests/test_agent_setup.py
new file mode 100644
index 0000000..b3fd6ac
--- /dev/null
+++ b/tests/test_agent_setup.py
@@ -0,0 +1,243 @@
+"""Tests for the Chatbot Journey endpoints.
+
+Covers:
+  1. Start journey for local agent → session_id + first question, done=False
+  2. Start journey for cloud agent → contextual email-focused question
+  3. Start journey with existing agent_id → session seeded, first question returned
+  4. Start journey with non-existent agent_id → still succeeds (graceful fallback)
+  5. Message: continue conversation → done=False, follow-up question returned
+  6. Message: LLM wraps up → done=True + prompt_template extracted correctly
+  7. Message with max-turns nudge → no crash, returns response
+  8. Invalid session_id → 404
+  9. Expired session → 404
+  10. Session ownership: user B cannot access user A's session
+  11. No JWT on /start → 401
+  12. No JWT on /message → 401
+"""
+
+from __future__ import annotations
+
+import time
+import uuid
+from unittest.mock import AsyncMock, patch
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.api.routes.agent_setup import (
+    _SESSION_TTL_SECONDS,
+    _TEMPLATE_END,
+    _TEMPLATE_START,
+    _extract_template,
+    _sessions,
+)
+from app.models import LocalAgentConfig
+from tests.conftest import TEST_USER_IDS, auth_header
+
+# ── Helpers ──────────────────────────────────────────────────────────────
+
+
+def _start(client: TestClient, agent_type: str = "local", agent_id: str | None = None, tier: str = "power") -> dict:
+    body: dict = {"agent_type": agent_type}
+    if agent_id:
+        body["agent_id"] = agent_id
+    resp = client.post("/api/v1/agents/journey/start", json=body, headers=auth_header(tier))
+    return resp
+
+
+def _message(client: TestClient, session_id: str, message: str, tier: str = "power") -> dict:
+    return client.post(
+        "/api/v1/agents/journey/message",
+        json={"session_id": session_id, "message": message},
+        headers=auth_header(tier),
+    )
+
+
+# ── Unit: _extract_template ───────────────────────────────────────────────
+
+
+def test_extract_template_present():
+    text = f"Some preamble.\n{_TEMPLATE_START}\nExtract tasks from emails.\n{_TEMPLATE_END}\nTrailing text."
+    result = _extract_template(text)
+    assert result == "Extract tasks from emails."
+
+
+def test_extract_template_absent():
+    assert _extract_template("No markers here.") is None
+
+
+def test_extract_template_empty_content():
+    text = f"{_TEMPLATE_START}\n{_TEMPLATE_END}"
+    assert _extract_template(text) is None
+
+
+# ── Start journey ─────────────────────────────────────────────────────────
+
+
+def test_start_journey_local(client: TestClient):
+    resp = _start(client, agent_type="local")
+    assert resp.status_code == 200
+    body = resp.json()
+    assert "session_id" in body
+    assert body["done"] is False
+    assert body["prompt_template"] is None
+    assert len(body["message"]) > 0
+    # Local question should be about files/directories
+    assert any(w in body["message"].lower() for w in ("file", "director", "document", "monitor"))
+
+
+def test_start_journey_cloud(client: TestClient):
+    resp = _start(client, agent_type="cloud")
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["done"] is False
+    # Cloud question should mention emails or messages
+    assert any(w in body["message"].lower() for w in ("email", "message", "communication"))
+
+
+def test_start_journey_with_agent_id(client: TestClient, db_session: AsyncSession):
+    """When agent_id is provided, session should be created even if agent doesn't exist."""
+    fake_agent_id = str(uuid.uuid4())
+    resp = _start(client, agent_type="local", agent_id=fake_agent_id)
+    # Should succeed gracefully even if the agent_id doesn't exist
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["done"] is False
+
+
+def test_start_journey_with_existing_agent(client: TestClient, db_session: AsyncSession):
+    """When a real local agent is provided, session is seeded with its prompt_template."""
+    import asyncio
+
+    user_id = TEST_USER_IDS["power"]
+    agent = LocalAgentConfig(
+        id=str(uuid.uuid4()),
+        user_id=user_id,
+        name="Test Agent",
+        device_id="device-1",
+        directory_paths=["/home/user/emails"],
+        data_types=["tasks"],
+        prompt_template="Extract tasks from .eml files.",
+        file_extensions=[".eml"],
+        schedule_cron="0 */6 * * *",
+        enabled=True,
+    )
+
+    async def _seed():
+        db_session.add(agent)
+        await db_session.commit()
+
+    asyncio.get_event_loop().run_until_complete(_seed())
+
+    resp = _start(client, agent_type="local", agent_id=agent.id)
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["done"] is False
+    # The session should be stored
+    assert body["session_id"] in _sessions
+
+
+def test_start_journey_requires_auth(client: TestClient):
+    resp = client.post("/api/v1/agents/journey/start", json={"agent_type": "local"})
+    assert resp.status_code == 401
+
+
+# ── Message ───────────────────────────────────────────────────────────────
+
+
+def test_message_continues_conversation(client: TestClient):
+    """A mid-journey reply (no template markers) returns done=False."""
+    follow_up = "That looks good. Can you tell me more about priority rules?"
+
+    with patch("app.api.routes.agent_setup._call_llm", new=AsyncMock(return_value=follow_up)):
+        start_resp = _start(client, agent_type="local")
+        assert start_resp.status_code == 200
+        session_id = start_resp.json()["session_id"]
+
+        msg_resp = _message(client, session_id, "I have .eml and .txt files")
+        assert msg_resp.status_code == 200
+        body = msg_resp.json()
+        assert body["done"] is False
+        assert body["prompt_template"] is None
+        assert body["message"] == follow_up
+        assert body["session_id"] == session_id
+
+
+def test_message_produces_template(client: TestClient):
+    """When the LLM includes PROMPT_TEMPLATE markers, done=True and prompt_template is set."""
+    final_template = "Extract tasks from email. Subject → title. 'urgent' → high priority."
+    llm_response = (
+        "Great, I have all the information I need.\n"
+        f"{_TEMPLATE_START}\n{final_template}\n{_TEMPLATE_END}\n"
+    )
+
+    with patch("app.api.routes.agent_setup._call_llm", new=AsyncMock(return_value=llm_response)):
+        start_resp = _start(client, agent_type="cloud")
+        assert start_resp.status_code == 200
+        session_id = start_resp.json()["session_id"]
+
+        msg_resp = _message(client, session_id, "Only invoices from clients")
+        assert msg_resp.status_code == 200
+        body = msg_resp.json()
+        assert body["done"] is True
+        assert body["prompt_template"] == final_template
+        # Session should be cleaned up
+        assert session_id not in _sessions
+
+
+def test_message_invalid_session(client: TestClient):
+    resp = _message(client, "nonexistent-session-id", "hello")
+    assert resp.status_code == 404
+
+
+def test_message_wrong_owner(client: TestClient):
+    """User B cannot access user A's session."""
+    start_resp = _start(client, agent_type="local", tier="power")
+    session_id = start_resp.json()["session_id"]
+
+    # user with "pro" tier (different user_id) tries to send a message
+    resp = client.post(
+        "/api/v1/agents/journey/message",
+        json={"session_id": session_id, "message": "hello"},
+        headers=auth_header("pro"),  # different user
+    )
+    assert resp.status_code == 404
+
+
+def test_message_expired_session(client: TestClient):
+    """Expired sessions return 404."""
+    start_resp = _start(client, agent_type="local")
+    session_id = start_resp.json()["session_id"]
+
+    # Manually expire the session
+    _sessions[session_id].created_at = time.monotonic() - _SESSION_TTL_SECONDS - 1
+
+    resp = _message(client, session_id, "hello")
+    assert resp.status_code == 404
+
+
+def test_message_requires_auth(client: TestClient):
+    resp = client.post(
+        "/api/v1/agents/journey/message",
+        json={"session_id": "any", "message": "hello"},
+    )
+    assert resp.status_code == 401
+
+
+def test_message_max_turns_nudge(client: TestClient):
+    """After _MAX_TURNS user messages, a system nudge is appended but no crash occurs."""
+    from app.api.routes.agent_setup import _MAX_TURNS
+
+    follow_up = "Tell me more about priority rules."
+
+    with patch("app.api.routes.agent_setup._call_llm", new=AsyncMock(return_value=follow_up)):
+        start_resp = _start(client, agent_type="local")
+        session_id = start_resp.json()["session_id"]
+
+        for i in range(_MAX_TURNS):
+            resp = _message(client, session_id, f"Answer {i + 1}")
+            assert resp.status_code == 200
+            # While no template produced, session must still exist
+            if resp.json()["done"]:
+                break  # LLM decided to wrap up early — also fine