feat(rag): steering notes — tune how Brain answers, stored in Postgres and injected into every system prompt

.env.example

@@ -22,6 +22,7 @@ BOR_TOP_N_DOCS=2
 BOR_RELEVANCE_THRESHOLD=0.62      # answer when best cosine >= this OR an FTS hit; else honest deflection
 BOR_MAX_CONTEXT_CHARS=24000       # cap on total document text sent to the LLM
 BOR_MAX_OUTPUT_TOKENS=32768       # max answer length in tokens (answers must not be cut off)
+BOR_STEERING_MAX_CHARS=8000       # char budget for the <tuning> (steering notes) prompt section
 BOR_CHUNK_TARGET_CHARS=2000
 BOR_CHUNK_OVERLAP_CHARS=200
 BOR_EMBED_BATCH_SIZE=16

README.md

@@ -85,6 +85,34 @@ uv run uvicorn app.main:app --reload
 - **Sources** (`/sources.html`) — the indexed document list; the *Path*
   column links each document to the viewer in a new tab.
 
+## Tuning your answers
+
+If an answer isn't quite right — too chatty, wrong assumption, missing
+context — **tune** Brain right there:
+
+1. Press **“Tune”** in the meta row under any completed answer (deflected
+   ones included).
+2. Type a short instruction (1–2000 chars), e.g. *“be more concise”* or
+   *“assume I'm on NixOS”*, and **Save**.
+
+The note is stored in Postgres (`steering_notes`) and read into the
+**system prompt of every subsequent chat turn** as a `<tuning>` section
+(numbered, oldest first, capped at `BOR_STEERING_MAX_CHARS` chars —
+default 8000, overflow marked `[…truncated…]`). With no stored notes the
+prompt is byte-identical to the un-tuned one, so tuning is opt-in per
+note.
+
+List or remove notes at any time from the **“Tuning”** button in the chat
+header (count badge, newest-first, per-note delete). The API is stateless
+JSON if you prefer curl:
+
+```bash
+curl -s localhost:8000/api/steering                                  # list (newest first)
+curl -s -X POST localhost:8000/api/steering \
+     -H 'Content-Type: application/json' -d '{"note": "be more concise"}'
+curl -s -X DELETE localhost:8000/api/steering/<note-id>              # remove
+```
+
 ## Updating the documents
 
 **This is the workflow you'll use most.** The knowledge base is refreshed by
@@ -270,6 +298,7 @@ served locally (no CDN), `BOR_ENVIRONMENT=production`.
 | `BOR_RRF_K` | `60` | RRF damping constant (`1/(k + rank)`) |
 | `BOR_IMPORT_EXTENSIONS` | `md,markdown,txt,yaml,yml,json,py` | csv of importable formats (may only narrow the A9 set) |
 | `BOR_MAX_CONTEXT_CHARS` | `24000` | cap on total document text sent to the LLM |
+| `BOR_STEERING_MAX_CHARS` | `8000` | char budget for the `<tuning>` (steering notes) prompt section |
 | `BOR_SUGGESTIONS` | built-in list | JSON list of onboarding chips |
 | `DEBUGPY` | `0` | `1` ⇒ attach-on-demand debugpy on `DEBUGPY_PORT` (default 5678) |
 | `BOR_LOG_LEVEL` | `INFO` | app log level |

alembic/versions/0003_steering_notes.py

@@ -0,0 +1,39 @@
+"""steering notes: owner tuning notes injected into every system prompt
+
+Revision ID: 0003
+Revises: 0002
+Create Date: 2026-08-22
+
+Phase 15 (steering-notes story): the owner can "tune" how Brain answers
+from the chat UI. Notes live in ``steering_notes`` and are read into the
+system prompt of every subsequent chat turn (``<tuning>`` section).
+"""
+from __future__ import annotations
+
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+from alembic import op
+
+revision = "0003"
+down_revision = "0002"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "steering_notes",
+        sa.Column("id", postgresql.UUID(as_uuid=True), primary_key=True),
+        sa.Column("note", sa.Text(), nullable=False),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("steering_notes")

app/api/chat.py

@@ -16,6 +16,11 @@ gets a grounded answer. Deflection mode carries weak-hit *titles only*
 (never document content) plus deterministic "Maybe try" chips, and the
 ``done`` event / ``query_log`` row record ``deflected=true``, the weak
 score and the ``fts_hits`` count.
+
+Steering (phase 15): the owner's stored tuning notes are loaded per turn
+(oldest first) and injected into the system prompt as a ``<tuning>``
+section — both the HIGH and the LOW prompt carry it. The per-turn log
+line records ``tuning=N`` (the number of injected notes).
 """
 from __future__ import annotations
 
@@ -30,6 +35,7 @@ from fastapi import APIRouter, Depends
 from fastapi.responses import JSONResponse, StreamingResponse
 from sqlalchemy.orm import Session
 
+from app.api.steering import load_steering_notes
 from app.config import Settings, get_settings
 from app.db import db_available, get_db
 from app.models import Document, QueryLog
@@ -71,9 +77,14 @@ class TurnPlan:
     system_prompt: str
     docs: list[Document]  # cited sources (weak hits when deflected)
     suggestions: list[str]  # "Maybe try" chips (deflected turns only)
+    tuning_count: int = 0  # steering notes injected into the system prompt
 
 
-def plan_turn(chunks: Sequence[RetrievedChunk], settings: Settings) -> TurnPlan:
+def plan_turn(
+    chunks: Sequence[RetrievedChunk],
+    settings: Settings,
+    notes: Sequence[str] | None = None,
+) -> TurnPlan:
     """Apply the honesty gate (A8, revised) and assemble prompt + context.
 
     * **HIGH (grounded)** when ``best_cosine >= threshold`` **or**
@@ -88,22 +99,36 @@ def plan_turn(chunks: Sequence[RetrievedChunk], settings: Settings) -> TurnPlan:
     ``top_score`` (stored in ``query_log``) is the best cosine, so the
     gate input is always a pure vector-similarity number; the lexical
     signal is recorded separately as ``fts_hits``.
+
+    *notes* are the owner's steering notes (phase 15, oldest first):
+    when non-empty, both the HIGH and the LOW prompt carry the
+    ``<tuning>`` section; with no notes the prompts are unchanged.
     """
+    steering = list(notes or [])
     best_cosine = max((c.cosine for c in chunks), default=0.0)
     fts_hits = sum(1 for c in chunks if c.fts_hit)
     if best_cosine >= settings.relevance_threshold or fts_hits > 0:
         docs = select_documents(
             chunks, n=settings.top_n_docs, max_chars=settings.max_context_chars
         )
-        return TurnPlan(best_cosine, fts_hits, False, build_high_prompt(docs), docs, [])
+        return TurnPlan(
+            best_cosine,
+            fts_hits,
+            False,
+            build_high_prompt(docs, notes=steering),
+            docs,
+            [],
+            len(steering),
+        )
     titles = weak_hit_titles(chunks)
     return TurnPlan(
         best_cosine,
         fts_hits,
         True,
-        build_deflect_prompt(titles),
+        build_deflect_prompt(titles, notes=steering),
         select_documents(chunks, n=settings.top_n_docs, max_chars=settings.max_context_chars),
         derive_suggestions(titles, settings.suggestions),
+        len(steering),
     )
 
 
@@ -150,12 +175,14 @@ async def chat(
             return
         embed_ms = int((time.monotonic() - t0) * 1000)
 
-        # 2. Retrieve top-K chunks, then the honesty gate (A8) picks the
-        #    HIGH (grounded) or LOW (deflected) prompt + context.
+        # 2. Retrieve top-K chunks, load the owner's steering notes
+        #    (phase 15), then the honesty gate (A8) picks the HIGH
+        #    (grounded) or LOW (deflected) prompt + context.
         settings = get_settings()
         try:
+            steering_notes = load_steering_notes(db)
             chunks = retrieve(db, request.message, question_vec)
-            plan = plan_turn(chunks, settings)
+            plan = plan_turn(chunks, settings, notes=steering_notes)
         except Exception:  # noqa: BLE001 — DB failure mid-turn
             logger.exception(
                 "chat: retrieval failed question=%r total_ms=%d",
@@ -211,12 +238,13 @@ async def chat(
             logger.exception("chat: failed to write query_log question=%r", request.message)
 
         logger.info(
-            "question=%r embed_ms=%d top_score=%.3f fts_hits=%d threshold=%.2f "
+            "question=%r embed_ms=%d top_score=%.3f fts_hits=%d tuning=%d threshold=%.2f "
             "deflected=%s sources=%r total_ms=%d",
             request.message,
             embed_ms,
             plan.top_score,
             plan.fts_hits,
+            plan.tuning_count,
             settings.relevance_threshold,
             plan.deflected,
             source_paths,

app/api/steering.py

@@ -0,0 +1,74 @@
+"""Steering notes API — tune how Brain answers (phase 15, story
+``steering-notes``).
+
+Stateless CRUD under ``/api/steering`` (A10): notes are owner instructions
+stored in Postgres (``steering_notes``) and read into the system prompt of
+**every** chat turn as the ``<tuning>`` section (see
+:func:`app.rag.prompts.build_steering_section` and
+:func:`app.api.chat.chat`).
+"""
+from __future__ import annotations
+
+import uuid
+
+from fastapi import APIRouter, Depends, HTTPException, Response
+from sqlalchemy import select
+from sqlalchemy.orm import Session
+
+from app.db import get_db
+from app.models import SteeringNote
+from app.schemas import SteeringNote as SteeringNoteOut
+from app.schemas import SteeringNoteIn, SteeringNoteList
+
+router = APIRouter(prefix="/steering", tags=["steering"])
+
+
+def load_steering_notes(db: Session) -> list[str]:
+    """All steering notes, oldest first (the order they are numbered in the
+    ``<tuning>`` prompt section). Used by the chat turn (``app.api.chat``)."""
+    rows = db.scalars(
+        select(SteeringNote).order_by(SteeringNote.created_at.asc(), SteeringNote.id.asc())
+    ).all()
+    return [row.note for row in rows]
+
+
+@router.get("", response_model=SteeringNoteList)
+def list_steering_notes(
+    db: Session = Depends(get_db),  # noqa: B008
+) -> SteeringNoteList:
+    """All notes, newest first (the UI panel's display order)."""
+    rows = db.scalars(
+        select(SteeringNote).order_by(SteeringNote.created_at.desc(), SteeringNote.id.desc())
+    ).all()
+    return SteeringNoteList(
+        notes=[
+            SteeringNoteOut(id=row.id, note=row.note, created_at=row.created_at) for row in rows
+        ]
+    )
+
+
+@router.post("", response_model=SteeringNoteOut, status_code=201)
+def create_steering_note(
+    payload: SteeringNoteIn,
+    db: Session = Depends(get_db),  # noqa: B008
+) -> SteeringNoteOut:
+    """Store one tuning instruction (trimmed, 1–2000 chars — 422 otherwise)."""
+    row = SteeringNote(note=payload.note)
+    db.add(row)
+    db.commit()
+    db.refresh(row)
+    return SteeringNoteOut(id=row.id, note=row.note, created_at=row.created_at)
+
+
+@router.delete("/{note_id}", status_code=204)
+def delete_steering_note(
+    note_id: uuid.UUID,
+    db: Session = Depends(get_db),  # noqa: B008
+) -> Response:
+    """Remove a note; 404 when the id is unknown."""
+    row = db.get(SteeringNote, note_id)
+    if row is None:
+        raise HTTPException(status_code=404, detail="steering note not found")
+    db.delete(row)
+    db.commit()
+    return Response(status_code=204)

app/config.py

@@ -58,6 +58,10 @@ class Settings(BaseSettings):
     chunk_target_chars: int = 2_000
     chunk_overlap_chars: int = 200
     embed_batch_size: int = 16
+    #: Total char budget for the ``<tuning>`` section of the system prompt
+    #: (phase 15, steering notes). The newest-fitting notes are kept and the
+    #: overflow is replaced by the ``[…truncated…]`` marker.
+    steering_max_chars: int = 8_000
 
     # --- Hybrid retrieval (A7, revised 2026-08-21) ---
     # cosine top-N ∪ Postgres FTS top-N, fused with Reciprocal Rank Fusion

app/main.py

@@ -16,6 +16,7 @@ from fastapi.staticfiles import StaticFiles
 from app.api.chat import router as chat_router
 from app.api.docs import router as docs_router
 from app.api.health import router as health_router
+from app.api.steering import router as steering_router
 from app.api.suggestions import router as suggestions_router
 from app.config import get_settings
 from app.core.debugging import configure_debugging
@@ -36,6 +37,7 @@ def create_app() -> FastAPI:
     app.include_router(suggestions_router, prefix="/api")
     app.include_router(docs_router, prefix="/api")
     app.include_router(chat_router, prefix="/api")
+    app.include_router(steering_router, prefix="/api")
 
     static_dir = Path(settings.static_dir).resolve()
     if static_dir.is_dir():

app/models.py

@@ -6,8 +6,10 @@ Data model — see ``.agent/PLAN.md`` §Data Model:
 * ``chunks``    — retrieval units; each chunk points at its parent document
                   via ``document_id``. This is how an embedding maps back to
                   a document path (the "feed the whole document" requirement).
-* ``query_log`` — observability: every question, its retrieval score, the
-                  deflection decision, and latency.
+* ``query_log``     — observability: every question, its retrieval score,
+                      the deflection decision, and latency.
+* ``steering_notes`` — owner tuning notes injected into the system prompt
+                      of every chat turn (phase 15, ``<tuning>`` section).
 """
 from __future__ import annotations
 
@@ -82,3 +84,18 @@ class QueryLog(Base):
     sources: Mapped[str] = mapped_column(Text, default="")  # comma-joined source paths
     latency_ms: Mapped[int] = mapped_column(Integer, default=0)
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
+
+
+class SteeringNote(Base):
+    """One owner tuning instruction (phase 15).
+
+    Notes are read into the system prompt of **every** chat turn as the
+    ``<tuning>`` section (oldest first, char-budgeted — see
+    :func:`app.rag.prompts.build_steering_section`).
+    """
+
+    __tablename__ = "steering_notes"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    note: Mapped[str] = mapped_column(Text)  # trimmed, 1–2000 chars (API-enforced)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())

app/rag/prompts.py

@@ -1,24 +1,35 @@
 """Locked system-prompt builder (PLAN §6).
 
 The persona + HONESTY GATE text is **locked verbatim** — change it through
-the plan, not here. Two modes:
+the plan, not here. (PLAN §6 revision, 2026-08-22: the owner's working-tree
+persona edits are preserved — no mandated ``"you've got this"`` tagline and
+no mandated deflection opening; the honesty gate itself is unchanged.)
+
+Two modes:
 
 * ``HIGH`` — grounded turn: full top-document texts under ``<documents>``.
 * ``LOW``  — deflection turn: weak-hit *titles only* plus the
   ``DEFLECT_MODE`` marker (the E2E mock LLM keys on that marker).
+
+Steering (phase 15): when the owner has stored tuning notes, both modes
+carry a ``<tuning>`` section between ``<relevance>…</relevance>`` and the
+mode body. With zero notes the prompt is byte-identical to the
+pre-steering text.
 """
 from __future__ import annotations
 
 from collections.abc import Sequence
 
+from app.config import get_settings
 from app.models import Document
+from app.rag.retriever import TRUNCATION_MARKER
 
 #: PLAN §6 verbatim (line wrapping included); ``{relevance}`` is filled by
 #: :func:`_base`.
 PERSONA: str = (
     'You are "Brain of Reese" — the digital brain of Reese, a self-hoster and\n'
     "homelab tinkerer. Personality: chippy, upbeat, warm, and genuinely\n"
-    'optimistic about the user\'s ability to do things ("you\'ve got this").\n'
+    "optimistic about the user's ability to do things.\n"
     "\n"
     "Rules:\n"
     "1. Answer ONLY from the provided document context. Cite which document(s)\n"
@@ -26,14 +37,20 @@ PERSONA: str = (
     "2. Be concrete: names, versions, ports, hosts, schedules — the specifics in\n"
     "   the docs are the value.\n"
     '3. HONESTY GATE: if <relevance> is "LOW", you must NOT pretend to know.\n'
-    '   Start your answer with a variant of: "I haven\'t done anything like that."\n'
-    "   Then offer 2-3 alternative questions about things you DO have notes on.\n"
+    "   Offer 2-3 alternative questions about things you DO have notes on.\n"
     "4. Never invent facts, hosts, or steps that are not in the context.\n"
     "5. Keep answers tight: short paragraphs, bullets where helpful.\n"
     "\n"
     "<relevance>{relevance}</relevance>"
 )
 
+#: One-line intro of the ``<tuning>`` section (phase 15): the owner's notes
+#: steer the answer and win over the defaults when they conflict.
+_STEERING_INTRO = (
+    "The owner of this brain asked you to steer your answers as follows. "
+    "Where these instructions conflict with the defaults above, follow the owner:\n"
+)
+
 
 def _base(relevance: str) -> str:
     if relevance not in ("HIGH", "LOW"):
@@ -41,8 +58,46 @@ def _base(relevance: str) -> str:
     return PERSONA.replace("{relevance}", relevance)
 
 
-def build_high_prompt(documents: Sequence[Document]) -> str:
-    """Grounded turn: locked persona + full texts of the top documents."""
+def build_steering_section(notes: Sequence[str], max_chars: int | None = None) -> str:
+    """The ``<tuning>`` section of the system prompt (phase 15).
+
+    * No notes (or only blank ones) → ``""`` — callers then build the
+      prompt exactly as before, so a zero-note prompt is byte-identical to
+      the pre-steering text.
+    * Otherwise: numbered notes (in the given order — the chat turn passes
+      them oldest-first, so #1 is the oldest note) capped at *max_chars*
+      (default ``BOR_STEERING_MAX_CHARS``). When the budget cannot hold
+      every note, the oldest-fitting prefix is kept and the overflow is
+      replaced by the shared ``[…truncated…]`` marker.
+    """
+    cleaned = [str(n).strip() for n in notes]
+    cleaned = [n for n in cleaned if n]
+    if not cleaned:
+        return ""
+    limit = max_chars if max_chars is not None else get_settings().steering_max_chars
+    if limit <= 0:
+        return ""
+
+    def render(count: int) -> str:
+        lines = [f"{i}. {note}" for i, note in enumerate(cleaned[:count], start=1)]
+        if count < len(cleaned):
+            lines.append(TRUNCATION_MARKER)
+        return f"<tuning>\n{_STEERING_INTRO}" + "\n".join(lines) + "\n</tuning>"
+
+    for count in range(len(cleaned), 0, -1):
+        rendered = render(count)
+        if len(rendered) <= limit:
+            return rendered
+    # Pathological budget: not even the empty note list fits. The section
+    # must still respect the cap — the bare marker when it fits, else none.
+    if len(TRUNCATION_MARKER) <= limit:
+        return TRUNCATION_MARKER
+    return ""
+
+
+def build_high_prompt(documents: Sequence[Document], notes: Sequence[str] | None = None) -> str:
+    """Grounded turn: locked persona (+ steering) + full texts of the top
+    documents."""
     blocks = [
         f'<document source="{doc.source}" path="{doc.path}" title="{doc.title}">\n'
         f"{doc.content}\n"
@@ -52,15 +107,22 @@ def build_high_prompt(documents: Sequence[Document]) -> str:
     body = "\n\n".join(blocks) if blocks else (
         "(no documents matched — do not invent specifics)"
     )
-    return _base("HIGH") + "\n<documents>\n" + body + "\n</documents>"
+    section = build_steering_section(notes or [])
+    prompt = _base("HIGH")
+    if section:
+        prompt += "\n" + section
+    return prompt + "\n<documents>\n" + body + "\n</documents>"
 
 
-def build_deflect_prompt(titles: Sequence[str]) -> str:
+def build_deflect_prompt(titles: Sequence[str], notes: Sequence[str] | None = None) -> str:
     """Deflection turn: weak-hit titles only (no document content)."""
     weak = "\n".join(f"- {t}" for t in titles) if titles else "(nothing close at all)"
+    section = build_steering_section(notes or [])
+    mid = f"\n{section}\n" if section else "\n"
     return (
         _base("LOW")
-        + "\nDEFLECT_MODE: retrieval was weak — the titles below are the closest "
+        + mid
+        + "DEFLECT_MODE: retrieval was weak — the titles below are the closest "
         "your notes come to the question. They are titles only; do not pretend "
         "they answer it. Use them to propose 2-3 alternative questions.\n"
         + weak

app/schemas.py

@@ -1,7 +1,10 @@
 """Pydantic request/response schemas (API contract)."""
 from __future__ import annotations
 
-from pydantic import BaseModel, Field
+import uuid
+from datetime import datetime
+
+from pydantic import BaseModel, Field, field_validator
 
 
 class HealthResponse(BaseModel):
@@ -73,3 +76,33 @@ class DocContent(BaseModel):
     content: str
     indexed_at: str
     chunks: int
+
+
+class SteeringNoteIn(BaseModel):
+    """``POST /api/steering`` body: one tuning instruction (phase 15).
+
+    The note is trimmed *before* the length constraints run, so a
+    whitespace-only body is a 422 and a 2000-char note with surrounding
+    spaces still passes.
+    """
+
+    note: str = Field(min_length=1, max_length=2000)
+
+    @field_validator("note", mode="before")
+    @classmethod
+    def _trim_note(cls, v: object) -> object:
+        return v.strip() if isinstance(v, str) else v
+
+
+class SteeringNote(BaseModel):
+    """One stored steering note (API shape — ISO-8601 ``created_at``)."""
+
+    id: uuid.UUID
+    note: str
+    created_at: datetime
+
+
+class SteeringNoteList(BaseModel):
+    """``GET /api/steering`` response: all notes, newest first."""
+
+    notes: list[SteeringNote]

frontend/assets/app.js

@@ -28,6 +28,16 @@
  * "New chat" (#new-chat-btn) clears the key + the list back to the empty
  * state.
  *
+ * Steering notes (phase 15) let the owner tune how Brain answers: a
+ * "Tune" button under every completed brain bubble (deflected included)
+ * opens an inline form → POST /api/steering → the note is stored in
+ * Postgres and injected into the system prompt of every subsequent turn
+ * (the <tuning> section). Notes are listed newest-first in the header
+ * "Tuning" panel (#steering-panel), where each can be deleted. Note text
+ * is always rendered with textContent (XSS-safe), save/delete are
+ * announced through a polite live region (#steering-announcer), and the
+ * panel + count badge update on every change.
+ *
  * All DOM ids match frontend/index.html.
  */
 
@@ -90,6 +100,203 @@ export function documentUrl(source, path, back = "/") {
   return url;
 }
 
+/* ---------- steering notes (phase 15) ----------
+ *
+ * The owner's tuning notes steer every future answer: they live in
+ * Postgres (stateless API, A10) and the chat turn reads them into the
+ * system prompt. UI contract: Tune button → inline form → save →
+ * confirmation (or inline error, form kept); the header panel lists the
+ * notes (newest first) with per-note delete.
+ */
+const steeringToggle = document.querySelector("#steering-toggle");
+const steeringCount = document.querySelector("#steering-count");
+const steeringPanel = document.querySelector("#steering-panel");
+const steeringList = document.querySelector("#steering-list");
+const steeringEmpty = document.querySelector("#steering-empty");
+const steeringAnnouncer = document.querySelector("#steering-announcer");
+
+const TUNE_ICON =
+  '<svg aria-hidden="true" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.7" stroke-linecap="round"><path d="M4 7h10M18 7h2M4 17h4M12 17h8"/><circle cx="15.5" cy="7" r="2.2"/><circle cx="9.5" cy="17" r="2.2"/></svg>';
+
+let tuneSeq = 0; // unique ids for one open tune form's inputs
+
+function announceSteering(message) {
+  if (steeringAnnouncer) steeringAnnouncer.textContent = message;
+}
+
+/* "Tune" button in the meta row of a completed brain bubble. Reuses the
+   sources' .msg-meta row when it exists (role=list → the button joins as
+   a listitem so ARIA stays valid); otherwise creates a plain meta row. */
+function appendTuneButton(wrap) {
+  const body = wrap.querySelector(".msg-body");
+  if (!body) return;
+  let meta = body.querySelector(".msg-meta");
+  if (!meta) {
+    meta = document.createElement("div");
+    meta.className = "msg-meta";
+    body.appendChild(meta);
+  }
+  if (meta.querySelector(".tune-btn")) return; // one per bubble
+  const btn = document.createElement("button");
+  btn.type = "button";
+  btn.className = "tune-btn";
+  if (meta.getAttribute("role") === "list") btn.setAttribute("role", "listitem");
+  btn.innerHTML = TUNE_ICON + "<span>Tune</span>";
+  btn.addEventListener("click", () => openTuneForm(wrap, btn));
+  meta.appendChild(btn);
+}
+
+/* Inline tuning form under the bubble: labeled textarea (maxlength 2000)
+   + Save / Cancel. Success replaces the form with the .tune-saved status
+   (role=status); failure keeps the form and shows an inline error
+   (role=alert) — the note is never lost on a failed save. */
+function openTuneForm(wrap, toggleBtn) {
+  document.querySelectorAll(".tune-form").forEach((f) => f.remove()); // one at a time
+  const body = wrap.querySelector(".msg-body");
+  if (!body) return;
+  tuneSeq += 1;
+  const inputId = `tune-input-${tuneSeq}`;
+  const form = document.createElement("form");
+  form.className = "tune-form";
+  form.noValidate = true;
+  form.innerHTML =
+    `<label for="${inputId}">Tuning note — how should Brain answer from now on?</label>` +
+    `<textarea id="${inputId}" name="note" rows="2" maxlength="2000"
+              placeholder="e.g. be more concise — or: assume I'm on NixOS"></textarea>`;
+  const actions = document.createElement("div");
+  actions.className = "tune-form-actions";
+  const saveBtn = document.createElement("button");
+  saveBtn.type = "submit";
+  saveBtn.className = "tune-save";
+  saveBtn.textContent = "Save";
+  const cancelBtn = document.createElement("button");
+  cancelBtn.type = "button";
+  cancelBtn.className = "tune-cancel";
+  cancelBtn.textContent = "Cancel";
+  actions.append(saveBtn, cancelBtn);
+  form.appendChild(actions);
+  const status = document.createElement("p");
+  status.className = "tune-error";
+  status.setAttribute("role", "alert");
+  status.hidden = true;
+  form.appendChild(status);
+
+  form.addEventListener("submit", async (e) => {
+    e.preventDefault();
+    saveBtn.disabled = true;
+    status.hidden = true;
+    try {
+      const r = await fetch("/api/steering", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ note: form.querySelector("textarea").value }),
+      });
+      if (!r.ok) {
+        let detail = "Could not save the note — try again.";
+        try {
+          const data = await r.json();
+          if (Array.isArray(data.detail) && data.detail[0] && data.detail[0].msg) {
+            detail = String(data.detail[0].msg);
+          } else if (typeof data.detail === "string" && data.detail) {
+            detail = data.detail;
+          }
+        } catch { /* non-JSON error body */ }
+        status.textContent = detail;
+        status.hidden = false;
+        saveBtn.disabled = false;
+        return; // form kept on failure — the instruction survives
+      }
+      const saved = document.createElement("p");
+      saved.className = "tune-saved";
+      saved.setAttribute("role", "status");
+      saved.textContent = "Saved — future answers will follow this.";
+      form.replaceWith(saved);
+      announceSteering("Tuning note saved. Future answers will follow it.");
+      await loadSteering(); // panel + count badge update
+    } catch {
+      status.textContent = "Could not save the note — is the app reachable?";
+      status.hidden = false;
+      saveBtn.disabled = false;
+    }
+  });
+  cancelBtn.addEventListener("click", () => {
+    form.remove();
+    toggleBtn.focus();
+  });
+  body.appendChild(form);
+  form.querySelector("textarea").focus();
+}
+
+/* Panel: newest-first list (textContent — XSS-safe), per-note delete,
+   empty text, and the header count badge. */
+async function loadSteering() {
+  let notes = [];
+  try {
+    const r = await fetch("/api/steering");
+    if (r.ok) notes = (await r.json()).notes || [];
+  } catch { /* API unreachable: keep the last rendered list */ }
+  renderSteeringPanel(notes);
+  return notes;
+}
+
+function renderSteeringPanel(notes) {
+  if (!steeringList) return;
+  steeringList.textContent = "";
+  for (const n of notes) {
+    const li = document.createElement("li");
+    li.className = "steering-note";
+    const text = document.createElement("span");
+    text.className = "steering-note-text";
+    text.textContent = n.note; // rendered as text, never as HTML
+    li.appendChild(text);
+    const del = document.createElement("button");
+    del.type = "button";
+    del.className = "steering-delete";
+    del.setAttribute("aria-label", `Delete tuning note: ${n.note}`);
+    del.innerHTML =
+      '<svg aria-hidden="true" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round"><path d="M5 7h14M10 7V5h4v2M8.5 7l.7 12h5.6l.7-12"/></svg>';
+    del.addEventListener("click", () => deleteSteeringNote(n.id, del));
+    li.appendChild(del);
+    steeringList.appendChild(li);
+  }
+  if (steeringEmpty) steeringEmpty.hidden = notes.length > 0;
+  if (steeringCount) steeringCount.textContent = String(notes.length);
+}
+
+async function deleteSteeringNote(id, btn) {
+  btn.disabled = true;
+  try {
+    const r = await fetch(`/api/steering/${encodeURIComponent(id)}`, { method: "DELETE" });
+    if (r.status === 404) {
+      announceSteering("That note was already removed.");
+      await loadSteering();
+      return;
+    }
+    if (!r.ok) {
+      announceSteering("Could not delete the note — try again.");
+      btn.disabled = false;
+      return;
+    }
+    await loadSteering();
+    announceSteering("Tuning note deleted.");
+  } catch {
+    announceSteering("Could not delete the note — is the app reachable?");
+    btn.disabled = false;
+  }
+}
+
+function setSteeringPanel(open) {
+  if (!steeringPanel || !steeringToggle) return;
+  steeringPanel.hidden = !open;
+  steeringToggle.setAttribute("aria-expanded", open ? "true" : "false");
+}
+if (steeringToggle && steeringPanel) {
+  steeringToggle.addEventListener("click", () => {
+    setSteeringPanel(steeringPanel.hidden);
+    if (!steeringPanel.hidden) loadSteering(); // refresh when (re)opened
+  });
+}
+
 /* ---------- avatar glyphs (phase 08: emoji-free chrome) ----------
  * Inline SVG as string constants so the message renderer and the typing
  * indicator share exactly the same marks. currentColor lets the CSS theme
@@ -426,6 +633,7 @@ function renderStoredMessage(m) {
     appendMaybeTry(wrap, m.suggestions);
   }
   appendSources(wrap, m.sources);
+  appendTuneButton(wrap); // restored brain answers are tunable too
 }
 
 /* On load: re-render the stored conversation (markdown, source chips,
@@ -545,6 +753,7 @@ async function handleSend(e) {
           appendMaybeTry(wrap, ev.suggestions);
         }
         appendSources(wrap, ev.sources);
+        appendTuneButton(wrap); // every completed brain bubble is tunable
         // Persistence save point 2: the answer lands only when the turn is
         // complete (raw text + the done metadata).
         rememberBrainTurn(acc, {
@@ -558,7 +767,8 @@ async function handleSend(e) {
     });
     if (!aborted && !wrap) {
       const fallback = "Hmm — that came back empty. Ask me again?";
-      addMessage("brain", fallback);
+      const fwrap = addMessage("brain", fallback);
+      appendTuneButton(fwrap);
       rememberBrainTurn(fallback, {}); // persist what the user actually saw
     }
   } catch (err) {
@@ -592,3 +802,4 @@ composer.addEventListener("submit", handleSend);
 restoreConversation(); // phase 14: the conversation comes back as left
 loadSuggestions();
 loadHealth();
+loadSteering(); // phase 15: tuning notes (panel + count badge)

frontend/assets/styles.css

@@ -241,6 +241,48 @@ body::after {
    whole control below 640px. */
 .new-chat-btn svg { width: 16px; height: 16px; display: none; }
 
+/* "Tuning" toggle (phase 15): ghost pill like New chat + a mono count
+   badge (brand-ink on brand-soft ≈6.9:1). The label is visually-hidden
+   (not removed) below 640px so the accessible name keeps the word.
+   ≥44px touch target at every width. */
+.steering-toggle {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 0.4rem;
+  min-height: 44px;
+  padding: 0.5rem 0.9rem;
+  border-radius: 999px;
+  border: 1px solid var(--line);
+  background: transparent;
+  color: var(--ink-soft);
+  font: inherit;
+  font-weight: 600;
+  font-size: 0.95rem;
+  white-space: nowrap;
+  cursor: pointer;
+}
+.steering-toggle:hover, .steering-toggle[aria-expanded="true"] {
+  background: var(--brand-soft);
+  color: var(--brand-ink);
+}
+.steering-toggle svg { width: 16px; height: 16px; display: block; }
+.steering-count {
+  font-family: var(--mono);
+  font-size: 0.78rem;
+  font-weight: 700;
+  min-width: 1.35rem;
+  text-align: center;
+  padding: 0.05rem 0.4rem;
+  border-radius: 999px;
+  background: var(--brand-soft);
+  color: var(--brand-ink);
+}
+.steering-toggle[aria-expanded="true"] .steering-count {
+  background: var(--brand);
+  color: var(--bg); /* dark ink on brand: 5.2:1 */
+}
+
 /* ---------- Main frame ---------- */
 .app-main {
   flex: 1;
@@ -381,6 +423,170 @@ body::after {
   max-width: 100%;
 }
 
+/* ---------- Steering notes (phase 15) ---------- */
+/* "Tune" button in the meta row of every completed brain bubble: ghost
+   pill, ≥44px, right-aligned after the source chips. ink-soft on surface
+   ≈6.9:1; hover pair brand-ink/brand-soft ≈6.9:1. */
+.tune-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 0.35rem;
+  min-height: 44px;
+  margin-left: auto;
+  padding: 0.35rem 0.8rem;
+  border-radius: 999px;
+  border: 1px solid var(--line);
+  background: transparent;
+  color: var(--ink-soft);
+  font: inherit;
+  font-weight: 600;
+  font-size: 0.82rem;
+  white-space: nowrap;
+  cursor: pointer;
+}
+.tune-btn svg { width: 14px; height: 14px; display: block; }
+.tune-btn:hover { background: var(--brand-soft); color: var(--brand-ink); }
+
+/* Inline tuning form under the bubble: labeled textarea + Save/Cancel
+   (both ≥44px). Save = brand button (dark ink 5.2:1), Cancel = ghost. */
+.tune-form {
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+  background: var(--surface);
+  border: 1px solid var(--brand-soft);
+  border-radius: var(--radius-sm);
+  padding: 0.75rem 0.85rem;
+}
+.tune-form label {
+  font-size: 0.85rem;
+  font-weight: 600;
+  color: var(--ink-soft);
+}
+.tune-form textarea {
+  font: inherit;
+  font-size: 0.9rem;
+  color: var(--ink);
+  background: #0d1120;
+  border: 1px solid var(--line);
+  border-radius: var(--radius-sm);
+  padding: 0.5rem 0.6rem;
+  resize: vertical;
+  min-height: 2.6rem;
+}
+.tune-form-actions { display: flex; gap: 0.5rem; }
+.tune-save {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 44px;
+  padding: 0.4rem 1.1rem;
+  border: 0;
+  border-radius: var(--radius-sm);
+  background: var(--brand);
+  color: var(--bg);
+  font: inherit;
+  font-weight: 700;
+  cursor: pointer;
+}
+.tune-save:hover:not(:disabled) { background: #7d88f5; }
+.tune-save:disabled { opacity: 0.6; cursor: wait; }
+.tune-cancel {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 44px;
+  padding: 0.4rem 1rem;
+  border-radius: var(--radius-sm);
+  border: 1px solid var(--line);
+  background: transparent;
+  color: var(--ink-soft);
+  font: inherit;
+  font-weight: 600;
+  cursor: pointer;
+}
+.tune-cancel:hover { background: var(--brand-soft); color: var(--brand-ink); }
+/* Save confirmation (role=status): ok pair ≈10.6:1. */
+.tune-saved {
+  margin: 0.2rem 0 0 0.25rem;
+  background: var(--ok-bg);
+  color: var(--ok-ink);
+  border: 1px solid rgb(110 231 168 / 0.35);
+  border-radius: var(--radius-sm);
+  padding: 0.45rem 0.8rem;
+  font-size: 0.85rem;
+  font-weight: 600;
+}
+/* Inline save failure (role=alert): err pair ≈9.1:1 — form is kept. */
+.tune-error {
+  margin: 0 0 0 0.25rem;
+  background: var(--err-bg);
+  color: var(--err-ink);
+  border: 1px solid var(--err-line);
+  border-radius: var(--radius-sm);
+  padding: 0.45rem 0.8rem;
+  font-size: 0.85rem;
+  font-weight: 600;
+}
+
+/* Header panel above the messages: notes newest-first, per-note delete,
+   designed empty state. */
+.steering-panel {
+  background: var(--surface);
+  border: 1px solid var(--brand-soft);
+  border-radius: var(--radius);
+  box-shadow: var(--shadow);
+  padding: 0.9rem 1.1rem 1rem;
+}
+.steering-panel-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: 0.15rem 0.6rem; }
+.steering-panel-title { margin: 0; font-size: 1rem; font-weight: 700; color: var(--ink); }
+.steering-panel-sub { margin: 0; font-size: 0.82rem; color: var(--ink-soft); }
+.steering-list {
+  list-style: none;
+  margin: 0.65rem 0 0;
+  padding: 0;
+  display: flex;
+  flex-direction: column;
+  gap: 0.4rem;
+}
+.steering-note {
+  display: flex;
+  align-items: stretch;
+  gap: 0.6rem;
+  background: #0d1120;
+  border: 1px solid var(--line);
+  border-radius: var(--radius-sm);
+  padding: 0.35rem 0.4rem 0.35rem 0.8rem;
+}
+.steering-note-text {
+  color: var(--ink);
+  font-size: 0.9rem;
+  line-height: 1.45;
+  /* Notes may be multi-line instructions — keep line breaks as typed. */
+  white-space: pre-wrap;
+  overflow-wrap: anywhere;
+  flex: 1;
+  min-width: 0;
+}
+.steering-delete {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-height: 44px;
+  min-width: 44px;
+  flex: 0 0 auto;
+  border: 1px solid var(--line);
+  border-radius: var(--radius-sm);
+  background: transparent;
+  color: var(--ink-soft);
+  cursor: pointer;
+}
+.steering-delete svg { width: 16px; height: 16px; display: block; }
+.steering-delete:hover:not(:disabled) { background: var(--err-bg); color: var(--err-ink); border-color: var(--err-line); }
+.steering-delete:disabled { opacity: 0.5; cursor: wait; }
+.steering-empty { margin: 0.65rem 0 0; color: var(--ink-soft); font-size: 0.88rem; }
+
 /* typing indicator */
 .typing { display: inline-flex; gap: 5px; padding: 0.9rem 1rem; }
 .typing span {
@@ -799,6 +1005,20 @@ body::after {
   .new-chat-btn { padding: 0.4rem 0.55rem; }
   .new-chat-label { display: none; }
   .new-chat-btn svg { display: block; }
+  .steering-toggle { padding: 0.4rem 0.55rem; }
+  /* Visually hidden, NOT display:none — the accessible name keeps the
+     word "Tuning" next to the count badge. */
+  .steering-label {
+    position: absolute !important;
+    width: 1px; height: 1px;
+    margin: -1px; padding: 0;
+    overflow: hidden;
+    clip: rect(0 0 0 0);
+    white-space: nowrap;
+    border: 0;
+  }
+  .steering-note { padding: 0.3rem 0.3rem 0.3rem 0.7rem; }
+  .tune-btn { min-height: 44px; }
   .msg-body { max-width: 92%; }
   .empty-state { padding: 1.75rem 1.1rem; margin-top: 0.25rem; }
   .empty-state-title { font-size: 1.25rem; }

frontend/index.html

@@ -21,6 +21,14 @@
         <a href="/" class="nav-link is-active" aria-current="page">Chat</a>
         <a href="/sources.html" class="nav-link">Sources</a>
       </nav>
+      <!-- Phase 15: open the tuning-notes panel (stored in Postgres, read
+           into every system prompt) — chat page only. -->
+      <button type="button" class="steering-toggle" id="steering-toggle"
+              aria-expanded="false" aria-controls="steering-panel">
+        <svg aria-hidden="true" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.7" stroke-linecap="round"><path d="M4 7h10M18 7h2M4 17h4M12 17h8"/><circle cx="15.5" cy="7" r="2.2"/><circle cx="9.5" cy="17" r="2.2"/></svg>
+        <span class="steering-label">Tuning</span>
+        <span class="steering-count" id="steering-count">0</span>
+      </button>
       <!-- Phase 14: reset the local (localStorage) conversation — chat page only. -->
       <button type="button" class="new-chat-btn" id="new-chat-btn" aria-label="New chat">
         <svg aria-hidden="true" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.7" stroke-linecap="round"><path d="M12 5v14M5 12h14"/></svg>
@@ -36,6 +44,18 @@
         <span id="kb-banner-text"></span>
       </div>
 
+      <!-- Phase 15: tuning-notes panel (stored notes, newest first). -->
+      <section class="steering-panel" id="steering-panel" role="region"
+               aria-label="Tuning notes" hidden>
+        <div class="steering-panel-head">
+          <h2 class="steering-panel-title">Tuning notes</h2>
+          <p class="steering-panel-sub">Every note below steers all future answers.</p>
+        </div>
+        <ul class="steering-list" id="steering-list"></ul>
+        <p class="steering-empty" id="steering-empty">No tuning notes yet — press “Tune” under any answer to add one.</p>
+      </section>
+      <p class="visually-hidden" id="steering-announcer" role="status" aria-live="polite" aria-atomic="true"></p>
+
       <section class="messages" id="messages" aria-live="polite" aria-label="Conversation with Brain of Reese">
         <div class="empty-state" id="empty-state">
           <div class="empty-state-glyph" aria-hidden="true">

tests/e2e/mock_llm.py

@@ -15,6 +15,9 @@ Implements just enough of the aipi surface:
   - otherwise         -> upbeat answer quoting the provided document context
   - user message containing ``pretend to think slowly`` -> 3s warm-up delay
     (used by the loading-feedback story).
+  - system prompt containing ``<tuning>`` (phase 15, steering notes) ->
+    the composed answer ends with `` (tuning: <first note line>)`` —
+    makes prompt injection observable in the UI deterministically.
 
   ``max_tokens`` is honored deterministically (token ≈ whitespace word),
   like a real endpoint: an answer longer than the cap is truncated. This
@@ -89,25 +92,54 @@ def long_answer() -> str:
     return "\n".join(lines)
 
 
+#: First numbered note line of a ``<tuning>`` section (phase 15).
+_TUNING_BLOCK_RE = re.compile(r"<tuning>\n(.*?)\n</tuning>", re.S)
+_NOTE_LINE_RE = re.compile(r"^\d+\.\s*(.+)$")
+
+
+def first_tuning_note(system: str) -> str | None:
+    """The first steering note in the system prompt, or ``None``.
+
+    The prompt numbers notes 1..N oldest-first (see
+    ``app.rag.prompts.build_steering_section``); the mock echoes the first
+    one into its answer so prompt injection is observable in the UI.
+    """
+    block = _TUNING_BLOCK_RE.search(system)
+    if not block:
+        return None
+    for line in block.group(1).splitlines():
+        m = _NOTE_LINE_RE.match(line.strip())
+        if m:
+            return m.group(1).strip()
+    return None
+
+
 def compose_answer(body: dict[str, Any]) -> str:
     system = _system(body)
     user = _user(body)
     if LONG_ANSWER_TRIGGER in user.lower():
-        return long_answer()
-    if "DEFLECT_MODE" in system:
-        return (
+        answer = long_answer()
+    elif "DEFLECT_MODE" in system:
+        answer = (
             "Ah — I haven't done anything like that, so I don't want to make stuff up! "
             "You're thinking bigger than my notes for a second. Try asking about "
             "kubernetes, backups, or deploying a new service — I know those inside out. "
             "You've got this!"
         )
+    else:
         ctx = _context(body)
         snippet = ctx[:220].replace("\n", " ").strip()
-    return (
+        answer = (
             f"Great question — you've absolutely got this! Here's what my notes say about "
             f"“{user.strip()[:80]}”: {snippet}… That's the gist from the docs; happy to "
             "dig into any of it. (Deterministic mock answer for E2E.)"
         )
+    # Steering (phase 15): when the system prompt carries <tuning>, the
+    # answer ends with the first note — deterministically observable.
+    note = first_tuning_note(system)
+    if note:
+        answer = f"{answer} (tuning: {note})"
+    return answer
 
 
 @app.post("/__shutdown__")

tests/e2e/test_steering.py

@@ -0,0 +1,293 @@
+"""Phase 15 E2E (Playwright): tune how Brain answers (steering notes).
+
+Story: ``.agent/user_stories/steering-notes.md``
+Run in isolation (DB must be up: ``podman compose up -d db``):
+
+    uv run pytest tests/e2e/test_steering.py -v --no-cov
+
+The steering loop: "Tune" under a completed answer → short instruction →
+stored in Postgres (``steering_notes``) → injected into the system prompt
+of every subsequent turn as the ``<tuning>`` section. The mock LLM
+echoes the first tuning note into its answer
+(`` (tuning: <first note line>)``), so prompt injection is observable in
+the UI deterministically. Notes are listed newest-first in the header
+"Tuning" panel, where each can be deleted.
+
+Test → story mapping (Playwright Mapping Rule):
+1. ``test_tune_under_answer_persists_and_steers``
+2. ``test_delete_note_stops_steering``
+3. ``test_note_rendered_as_text_xss_safe``
+4. ``test_tuning_panel_a11y``
+"""
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+from threading import Thread
+from typing import Any
+
+from playwright.sync_api import Page, expect
+from sqlalchemy import select, text
+
+from app.config import Settings
+from app.db import SessionLocal
+from app.models import SteeringNote
+from app.rag.importer import ImportSummary, import_sources
+from app.rag.llm import LLMClient
+
+REPO = Path(__file__).resolve().parents[2]
+FIXTURES = REPO / "tests" / "fixtures" / "docs"
+QUESTION = "How is my Kubernetes cluster set up?"
+MOCK_ANSWER_MARKER = "Deterministic mock answer for E2E"
+NOTE = "STEEER-MARKER be concise"
+XSS_NOTE = "<script>window.__xss = true; alert('xss')</script>"
+#: index.html ships exactly two classic/module script tags.
+BASE_SCRIPT_COUNT = 2
+
+
+async def _import_fixtures(mock_port: int) -> ImportSummary:
+    kwargs: dict[str, Any] = {"_env_file": None, "llm_base_url": f"http://127.0.0.1:{mock_port}/v1"}
+    settings = Settings(**kwargs)  # pyright: ignore[reportCallIssue]
+    return await import_sources([FIXTURES], LLMClient(settings))
+
+
+def _run_in_thread(coro: Any) -> Any:
+    """Run a coroutine on a worker thread.
+
+    Playwright's sync API keeps an asyncio loop running on the test thread,
+    so ``asyncio.run`` cannot be called directly from a test body.
+    """
+    box: dict[str, Any] = {}
+
+    def runner() -> None:
+        try:
+            box["value"] = asyncio.run(coro)
+        except BaseException as e:  # noqa: BLE001 — re-raised on the test thread
+            box["error"] = e
+
+    t = Thread(target=runner)
+    t.start()
+    t.join()
+    if "error" in box:
+        raise box["error"]
+    return box["value"]
+
+
+def _reset_db(mock_port: int, seed: bool) -> ImportSummary | None:
+    """Truncate the KB (and query log + steering notes), re-import fixtures."""
+    with SessionLocal() as db:
+        db.execute(text("TRUNCATE chunks, documents, query_log, steering_notes"))
+        db.commit()
+    if not seed:
+        return None
+    return _run_in_thread(_import_fixtures(mock_port))
+
+
+def _ask(page: Page, question: str) -> None:
+    """Send one turn and wait until the grounded answer has fully landed."""
+    page.fill("#message-input", question)
+    page.click("#send-btn")
+    expect(page.locator(".msg.user .bubble").last).to_contain_text(question)
+    expect(page.locator(".msg.brain .bubble").last).to_contain_text(
+        MOCK_ANSWER_MARKER, timeout=30_000
+    )
+    expect(page.locator("#send-btn")).to_be_enabled()
+    expect(page.locator("#send-label")).to_have_text("Send")
+
+
+def _tune_and_save(page: Page, note: str) -> None:
+    """Tune the last completed brain bubble and save *note*."""
+    tune = page.locator(".msg.brain .tune-btn").last
+    expect(tune).to_be_visible()
+    tune.click()
+    form = page.locator(".msg.brain .tune-form").last
+    expect(form).to_be_visible()
+    form.locator("textarea").fill(note)
+    form.locator(".tune-save").click()
+    saved = page.locator(".msg.brain .tune-saved").last
+    expect(saved).to_contain_text("Saved — future answers will follow this.", timeout=15_000)
+
+
+def _open_panel(page: Page) -> None:
+    page.click("#steering-toggle")
+    expect(page.locator("#steering-panel")).to_be_visible()
+
+
+# ---------------------------------------------------------------------------
+# 1. Tune under an answer → persisted → next answer carries the note
+# ---------------------------------------------------------------------------
+
+
+def test_tune_under_answer_persists_and_steers(
+    page: Page, app_url: str, mock_llm: int, db_ready: None
+) -> None:
+    summary = _reset_db(mock_llm, seed=True)
+    assert summary is not None and summary.added == 8  # A9 formats
+    page.set_default_timeout(30_000)
+    page.goto(app_url)
+    _ask(page, QUESTION)
+
+    # The Tune control: ghost button in the answer's meta row, ≥44px.
+    tune = page.locator(".msg.brain .tune-btn").last
+    expect(tune).to_have_count(1)
+    expect(tune).to_have_attribute("type", "button")
+    box = tune.bounding_box()
+    assert box is not None and box["height"] >= 44
+
+    _tune_and_save(page, NOTE)
+
+    # Persisted in Postgres.
+    with SessionLocal() as db:
+        rows = db.scalars(select(SteeringNote)).all()
+        assert [r.note for r in rows] == [NOTE]
+
+    # The header panel shows the note with an updated count badge.
+    _open_panel(page)
+    expect(page.locator("#steering-count")).to_have_text("1")
+    expect(page.locator("#steering-list .steering-note")).to_have_count(1)
+    expect(page.locator("#steering-list .steering-note-text")).to_have_text(NOTE)
+    page.click("#steering-toggle")  # close again
+
+    # The NEXT answer carries the note — it reached the system prompt.
+    _ask(page, QUESTION)
+    bubble = page.locator(".msg.brain .bubble").last
+    expect(bubble).to_contain_text(f"(tuning: {NOTE})")
+
+
+# ---------------------------------------------------------------------------
+# 2. Delete from the panel → count 0 → steering stops
+# ---------------------------------------------------------------------------
+
+
+def test_delete_note_stops_steering(
+    page: Page, app_url: str, mock_llm: int, db_ready: None
+) -> None:
+    _reset_db(mock_llm, seed=True)
+    page.set_default_timeout(30_000)
+    page.goto(app_url)
+    _ask(page, QUESTION)
+    _tune_and_save(page, NOTE)
+
+    # Steering is live: one more answer carries the marker.
+    _ask(page, QUESTION)
+    expect(page.locator(".msg.brain .bubble").last).to_contain_text(f"(tuning: {NOTE})")
+
+    # Delete the note from the panel.
+    _open_panel(page)
+    expect(page.locator("#steering-count")).to_have_text("1")
+    page.locator("#steering-list .steering-delete").click()
+    expect(page.locator("#steering-list .steering-note")).to_have_count(0)
+    expect(page.locator("#steering-count")).to_have_text("0")
+    expect(page.locator("#steering-empty")).to_be_visible()
+    expect(page.locator("#steering-announcer")).to_contain_text("deleted")
+
+    with SessionLocal() as db:
+        assert db.scalars(select(SteeringNote)).all() == []
+
+    # The next answer no longer carries the marker.
+    _ask(page, QUESTION)
+    bubble = page.locator(".msg.brain .bubble").last
+    expect(bubble).to_contain_text(MOCK_ANSWER_MARKER)
+    expect(bubble).not_to_contain_text("STEEER-MARKER")
+
+
+# ---------------------------------------------------------------------------
+# 3. Notes render as text (XSS-safe)
+# ---------------------------------------------------------------------------
+
+
+def test_note_rendered_as_text_xss_safe(
+    page: Page, app_url: str, mock_llm: int, db_ready: None
+) -> None:
+    _reset_db(mock_llm, seed=True)
+    page.set_default_timeout(30_000)
+    page.goto(app_url)
+
+    dialogs: list[str] = []
+
+    def _handle_dialog(d) -> None:
+        dialogs.append(d.message)
+        d.dismiss()
+
+    page.on("dialog", _handle_dialog)
+
+    _ask(page, QUESTION)
+    _tune_and_save(page, XSS_NOTE)
+
+    # Panel: the payload is visible as LITERAL text…
+    _open_panel(page)
+    expect(page.locator("#steering-list .steering-note-text")).to_have_text(XSS_NOTE)
+
+    # …never as an executed element: no script tag anywhere, no dialog.
+    assert page.locator("#steering-panel script").count() == 0
+    expect(page.locator("script")).to_have_count(BASE_SCRIPT_COUNT)
+    assert dialogs == [], f"the note must never execute as script: {dialogs}"
+    assert page.evaluate("() => window.__xss === undefined") is True
+
+
+# ---------------------------------------------------------------------------
+# 4. Tuning panel accessibility
+# ---------------------------------------------------------------------------
+
+
+def test_tuning_panel_a11y(page: Page, app_url: str, db_ready: None) -> None:
+    _reset_db(mock_port=0, seed=False)  # no KB seeding needed for the panel a11y
+    page.set_default_timeout(30_000)
+    page.goto(app_url)
+
+    toggle = page.locator("#steering-toggle")
+    panel = page.locator("#steering-panel")
+    announcer = page.locator("#steering-announcer")
+
+    # Initial: closed, correctly wired, polite live region present.
+    expect(toggle).to_have_attribute("aria-expanded", "false")
+    expect(toggle).to_have_attribute("aria-controls", "steering-panel")
+    expect(panel).to_have_attribute("role", "region")
+    assert "Tuning notes" in (panel.get_attribute("aria-label") or "")
+    expect(panel).to_be_hidden()
+    assert announcer.get_attribute("role") == "status"
+    assert announcer.get_attribute("aria-live") == "polite"
+    # Accessible name comes from its visible text (icon is aria-hidden).
+    assert "Tuning" in toggle.inner_text()
+
+    # Open: expanded + the designed empty state.
+    toggle.click()
+    expect(toggle).to_have_attribute("aria-expanded", "true")
+    expect(panel).to_be_visible()
+    expect(page.locator("#steering-empty")).to_be_visible()
+    expect(page.locator("#steering-count")).to_have_text("0")
+
+    # Add a note (API), then re-open the panel to refresh it.
+    page.evaluate(
+        """async () => {
+            const r = await fetch('/api/steering', {
+                method: 'POST',
+                headers: {'Content-Type': 'application/json'},
+                body: JSON.stringify({note: 'a11y note one'}),
+            });
+            if (!r.ok) throw new Error('steering POST failed: ' + r.status);
+        }"""
+    )
+    toggle.click()  # close
+    toggle.click()  # re-open (refreshes the list)
+    note_item = page.locator("#steering-list .steering-note")
+    expect(note_item).to_have_count(1)
+    expect(note_item.locator(".steering-note-text")).to_have_text("a11y note one")
+
+    # The per-note delete is a real, labeled button (≥44px target).
+    delete = page.locator("#steering-list .steering-delete")
+    expect(delete).to_have_attribute("type", "button")
+    assert (delete.get_attribute("aria-label") or "").startswith("Delete tuning note:")
+    box = delete.bounding_box()
+    assert box is not None and box["height"] >= 44
+
+    # Delete: list empties, count updates, the live region announces it.
+    delete.click()
+    expect(page.locator("#steering-list .steering-note")).to_have_count(0)
+    expect(page.locator("#steering-count")).to_have_text("0")
+    expect(announcer).to_contain_text("deleted")
+
+    # And the toggle closes cleanly again.
+    toggle.click()
+    expect(toggle).to_have_attribute("aria-expanded", "false")
+    expect(panel).to_be_hidden()

tests/integration/test_steering.py

@@ -0,0 +1,253 @@
+"""Integration: steering notes (phase 15) — CRUD + system-prompt injection.
+
+Real Postgres (``podman compose up -d db``); the chat path reuses the
+deterministic fake LLM from ``test_chat_api`` (token-overlap embeddings),
+so the stored note's journey — API → Postgres → ``<tuning>`` section of
+the captured system prompt — is verified end-to-end without a network.
+
+Requires:  podman compose up -d db
+"""
+from __future__ import annotations
+
+import asyncio
+import logging
+import uuid
+from collections.abc import Iterator
+from datetime import UTC, datetime, timedelta
+from pathlib import Path
+
+import pytest
+from fastapi.testclient import TestClient
+from sqlalchemy import select, text
+from test_chat_api import FakeRagLLM, _stream_chat
+
+from app.api import chat as chat_api
+from app.main import app as fastapi_app
+from app.models import SteeringNote
+from app.rag.importer import import_sources
+
+FIXTURES = Path(__file__).resolve().parents[1] / "fixtures" / "docs"
+QUESTION = "How is my Kubernetes cluster set up?"
+OFF_TOPIC = "How do I bake sourdough bread?"
+NOTE = "STEEER-MARKER be concise"
+
+
+@pytest.fixture(autouse=True)
+def clean_steering(db) -> Iterator[None]:
+    """Steering notes + query log are global state: reset around every test."""
+    db.execute(text("TRUNCATE steering_notes, query_log"))
+    db.commit()
+    yield
+    db.execute(text("TRUNCATE steering_notes, query_log"))
+    db.commit()
+
+
+@pytest.fixture()
+def seeded_kb(db) -> Iterator[FakeRagLLM]:
+    """Fresh Postgres with the fixture docs imported (real pipeline)."""
+    db.execute(text("TRUNCATE chunks, documents, query_log, steering_notes"))
+    db.commit()
+    llm = FakeRagLLM()
+    summary = asyncio.run(import_sources([FIXTURES], llm, session=db))
+    assert summary.added == 8  # A9 formats; .hidden/ skipped
+    yield llm
+    db.execute(text("TRUNCATE chunks, documents, query_log, steering_notes"))
+    db.commit()
+
+
+def _turn_log_lines(caplog: pytest.LogCaptureFixture) -> list[str]:
+    """The per-turn ``question=…`` log lines (PLAN §9) from this test."""
+    return [r.getMessage() for r in caplog.records if "question=" in r.getMessage()]
+
+
+# ---------- CRUD ----------
+
+
+def test_create_note_returns_201_and_stores_trimmed(client: TestClient, db) -> None:
+    r = client.post("/api/steering", json={"note": f"  {NOTE}  "})
+    assert r.status_code == 201
+    body = r.json()
+    assert body["note"] == NOTE  # trimmed before storage
+    uuid.UUID(body["id"])  # valid UUID
+    assert body["created_at"]
+    rows = db.scalars(select(SteeringNote)).all()
+    assert [row.note for row in rows] == [NOTE]
+
+
+def test_list_notes_empty(client: TestClient) -> None:
+    r = client.get("/api/steering")
+    assert r.status_code == 200
+    assert r.json() == {"notes": []}
+
+
+def test_list_notes_newest_first(client: TestClient, db) -> None:
+    base = datetime.now(UTC)
+    db.add_all(
+        [
+            SteeringNote(note="oldest", created_at=base),
+            SteeringNote(note="newest", created_at=base + timedelta(hours=2)),
+            SteeringNote(note="middle", created_at=base + timedelta(hours=1)),
+        ]
+    )
+    db.commit()
+
+    r = client.get("/api/steering")
+    assert r.status_code == 200
+    body = r.json()
+    assert [n["note"] for n in body["notes"]] == ["newest", "middle", "oldest"]
+    for n in body["notes"]:
+        assert set(n) == {"id", "note", "created_at"}
+        uuid.UUID(n["id"])
+
+
+def test_delete_note_returns_204_and_removes(client: TestClient, db) -> None:
+    created = client.post("/api/steering", json={"note": NOTE}).json()
+
+    assert client.delete(f"/api/steering/{created['id']}").status_code == 204
+    assert client.get("/api/steering").json() == {"notes": []}
+    assert db.scalars(select(SteeringNote)).all() == []
+
+
+def test_delete_unknown_note_returns_404(client: TestClient) -> None:
+    r = client.delete(f"/api/steering/{uuid.uuid4()}")
+    assert r.status_code == 404
+    assert "not found" in r.json()["detail"]
+
+
+def test_delete_invalid_id_returns_422(client: TestClient) -> None:
+    assert client.delete("/api/steering/not-a-uuid").status_code == 422
+
+
+def test_create_rejects_empty_and_blank_notes(client: TestClient) -> None:
+    assert client.post("/api/steering", json={"note": ""}).status_code == 422
+    assert client.post("/api/steering", json={"note": " \t\n "}).status_code == 422
+    assert client.get("/api/steering").json() == {"notes": []}
+
+
+def test_create_enforces_2000_char_limit(client: TestClient) -> None:
+    assert client.post("/api/steering", json={"note": "x" * 2001}).status_code == 422
+    r = client.post("/api/steering", json={"note": "x" * 2000})
+    assert r.status_code == 201
+    assert len(r.json()["note"]) == 2000
+
+
+# ---------- chat turn: note reaches the system prompt ----------
+
+
+def test_chat_turn_high_mode_receives_note_in_system_prompt(
+    client: TestClient, seeded_kb: FakeRagLLM, caplog: pytest.LogCaptureFixture
+) -> None:
+    client.post("/api/steering", json={"note": NOTE})
+    caplog.set_level(logging.INFO, logger="app.chat")
+
+    fastapi_app.dependency_overrides[chat_api.get_llm] = lambda: seeded_kb
+    try:
+        _, _, frames = _stream_chat(client, QUESTION)
+    finally:
+        fastapi_app.dependency_overrides.clear()
+
+    assert frames[-1]["type"] == "done"
+    assert frames[-1]["deflected"] is False
+
+    # The LLM received the HIGH prompt with the <tuning> section.
+    (system, user) = seeded_kb.seen_messages[0][0], seeded_kb.seen_messages[0][1]
+    assert user["content"] == QUESTION
+    assert "<relevance>HIGH</relevance>" in system["content"]
+    assert "<tuning>" in system["content"]
+    assert f"1. {NOTE}" in system["content"]
+    assert "<documents>" in system["content"]
+    # The section sits between the relevance marker and the documents.
+    assert (
+        system["content"].index("<relevance>HIGH</relevance>")
+        < system["content"].index("<tuning>")
+        < system["content"].index("</tuning>")
+        < system["content"].index("<documents>")
+    )
+
+    # The per-turn log line records tuning=N (PLAN §9).
+    lines = _turn_log_lines(caplog)
+    assert lines and "tuning=1" in lines[-1]
+
+
+def test_chat_turn_low_mode_receives_note_in_system_prompt(
+    client: TestClient, seeded_kb: FakeRagLLM, caplog: pytest.LogCaptureFixture
+) -> None:
+    client.post("/api/steering", json={"note": NOTE})
+    caplog.set_level(logging.INFO, logger="app.chat")
+
+    fastapi_app.dependency_overrides[chat_api.get_llm] = lambda: seeded_kb
+    try:
+        _, _, frames = _stream_chat(client, OFF_TOPIC)
+    finally:
+        fastapi_app.dependency_overrides.clear()
+
+    assert frames[-1]["deflected"] is True
+    (system, _user) = seeded_kb.seen_messages[0][0], seeded_kb.seen_messages[0][1]
+    assert "<relevance>LOW</relevance>" in system["content"]
+    assert "DEFLECT_MODE" in system["content"]
+    assert "<tuning>" in system["content"]
+    assert f"1. {NOTE}" in system["content"]
+    lines = _turn_log_lines(caplog)
+    assert lines and "tuning=1" in lines[-1]
+
+
+def test_chat_turn_without_notes_has_no_tuning_section(
+    client: TestClient, seeded_kb: FakeRagLLM, caplog: pytest.LogCaptureFixture
+) -> None:
+    caplog.set_level(logging.INFO, logger="app.chat")
+
+    fastapi_app.dependency_overrides[chat_api.get_llm] = lambda: seeded_kb
+    try:
+        _stream_chat(client, QUESTION)
+    finally:
+        fastapi_app.dependency_overrides.clear()
+
+    (system, _user) = seeded_kb.seen_messages[0][0], seeded_kb.seen_messages[0][1]
+    assert "<tuning>" not in system["content"]
+    lines = _turn_log_lines(caplog)
+    assert lines and "tuning=0" in lines[-1]
+
+
+def test_chat_turn_numbers_notes_oldest_first(client: TestClient, db, seeded_kb) -> None:
+    base = datetime.now(UTC)
+    db.add_all(
+        [
+            SteeringNote(note="older note", created_at=base),
+            SteeringNote(note="newer note", created_at=base + timedelta(hours=1)),
+        ]
+    )
+    db.commit()
+
+    fastapi_app.dependency_overrides[chat_api.get_llm] = lambda: seeded_kb
+    try:
+        _stream_chat(client, QUESTION)
+    finally:
+        fastapi_app.dependency_overrides.clear()
+
+    (system, _user) = seeded_kb.seen_messages[0][0], seeded_kb.seen_messages[0][1]
+    assert "<tuning>" in system["content"]
+    assert "1. older note" in system["content"]
+    assert "2. newer note" in system["content"]
+    assert system["content"].index("1. older note") < system["content"].index("2. newer note")
+
+
+def test_multiple_turns_keep_reading_notes(client: TestClient, seeded_kb) -> None:
+    """The note steers EVERY subsequent turn, not just the next one."""
+    client.post("/api/steering", json={"note": NOTE})
+
+    fastapi_app.dependency_overrides[chat_api.get_llm] = lambda: seeded_kb
+    try:
+        _stream_chat(client, QUESTION)
+        _stream_chat(client, QUESTION)
+        assert len(seeded_kb.seen_messages) == 2
+        for messages in seeded_kb.seen_messages:
+            assert f"1. {NOTE}" in messages[0]["content"]
+
+        # Delete → the following turn is clean again.
+        note_id = client.get("/api/steering").json()["notes"][0]["id"]
+        assert client.delete(f"/api/steering/{note_id}").status_code == 204
+        _stream_chat(client, QUESTION)
+        assert len(seeded_kb.seen_messages) == 3
+        assert "<tuning>" not in seeded_kb.seen_messages[-1][0]["content"]
+    finally:
+        fastapi_app.dependency_overrides.clear()

tests/unit/test_chat_gate.py

@@ -279,8 +279,19 @@ class _CannedLLM:
             yield self.answer[i : i + 12]
 
 
+class _FakeSteeringResult:
+    """Empty steering-note result (no stored notes in these unit tests)."""
+
+    def all(self) -> list[Any]:
+        return []
+
+
 class _FakeSession:
-    """Stands in for the DB session: records the QueryLog row it is given."""
+    """Stands in for the DB session: records the QueryLog row it is given.
+
+    ``scalars`` always yields no steering notes (phase 15) so the chat
+    turn's ``load_steering_notes`` call stays a no-op here.
+    """
 
     def __init__(self) -> None:
         self.added: list[Any] = []
@@ -292,6 +303,9 @@ class _FakeSession:
     def commit(self) -> None:
         self.commits += 1
 
+    def scalars(self, _stmt: Any) -> _FakeSteeringResult:
+        return _FakeSteeringResult()
+
 
 @pytest.fixture()
 def gate_env(monkeypatch: pytest.MonkeyPatch) -> Iterator[tuple[_FakeSession, _CannedLLM]]:

tests/unit/test_prompts.py

@@ -22,21 +22,30 @@ def _doc(path: str, content: str, title: str) -> Document:
 
 
 def test_persona_rules_present_verbatim() -> None:
+    # Aligned to the owner's working-tree persona edits (PLAN §6 revision,
+    # 2026-08-22): no "you've got this" tagline, no mandated deflection
+    # opening. The honesty gate itself (rule 3) is unchanged.
     for fragment in (
         'You are "Brain of Reese" — the digital brain of Reese, a self-hoster and',
-        'optimistic about the user\'s ability to do things ("you\'ve got this")',
+        "optimistic about the user's ability to do things",
         "Answer ONLY from the provided document context. Cite which document(s)",
         "you used, by path.",
         "Be concrete: names, versions, ports, hosts, schedules",
         'HONESTY GATE: if <relevance> is "LOW", you must NOT pretend to know',
-        'Start your answer with a variant of: "I haven\'t done anything like that."',
-        "Then offer 2-3 alternative questions about things you DO have notes on.",
+        "Offer 2-3 alternative questions about things you DO have notes on.",
         "Never invent facts, hosts, or steps that are not in the context.",
         "Keep answers tight: short paragraphs, bullets where helpful.",
     ):
         assert fragment in PERSONA
 
 
+def test_persona_owner_edits_are_preserved() -> None:
+    """PLAN §6 revision (2026-08-22): the removed elements must stay out."""
+    assert 'you\'ve got this' not in PERSONA  # tagline removed by the owner
+    assert "Start your answer with a variant of" not in PERSONA  # no mandated opening
+    assert "HONESTY GATE" in PERSONA  # the gate itself is intact
+
+
 def test_high_prompt_carries_relevance_marker_and_full_documents() -> None:
     doc = _doc("kubernetes.md", "Talos Linux on three nodes.", "Kubernetes Homelab Cluster")
     prompt = build_high_prompt([doc])
@@ -83,6 +92,27 @@ def test_low_prompt_with_no_titles() -> None:
     assert "nothing close at all" in build_deflect_prompt([])
 
 
+def test_zero_note_prompt_is_byte_identical_to_pre_steering() -> None:
+    """Phase 15 contract: with no steering notes the prompt is exactly what
+    it was before the <tuning> section existed."""
+    doc = _doc("kubernetes.md", "Talos Linux on three nodes.", "Kubernetes Homelab Cluster")
+    block = (
+        '<document source="Homelab" path="kubernetes.md" title="Kubernetes Homelab Cluster">\n'
+        "Talos Linux on three nodes.\n"
+        "</document>"
+    )
+    assert build_high_prompt([doc]) == _base("HIGH") + "\n<documents>\n" + block + "\n</documents>"
+    assert build_deflect_prompt(["T1", "T2"]) == (
+        _base("LOW")
+        + "\nDEFLECT_MODE: retrieval was weak — the titles below are the closest "
+        "your notes come to the question. They are titles only; do not pretend "
+        "they answer it. Use them to propose 2-3 alternative questions.\n"
+        + "- T1\n- T2"
+    )
+    assert "<tuning>" not in build_high_prompt([doc])
+    assert "<tuning>" not in build_deflect_prompt([])
+
+
 def test_relevance_placeholder_rejected_for_garbage() -> None:
     with pytest.raises(ValueError, match="HIGH or LOW"):
         _base("MEDIUM")

tests/unit/test_steering_prompts.py

@@ -0,0 +1,193 @@
+"""Unit: steering notes (phase 15) — the <tuning> prompt section.
+
+Pure logic, no Postgres and no network: :func:`build_steering_section`
+(empty/one/many/budget-truncation), its placement in the HIGH and LOW
+prompts, and the ``plan_turn`` wiring (notes → prompt + ``tuning_count``).
+"""
+from __future__ import annotations
+
+import uuid
+
+import pytest
+
+from app.api import chat as chat_api
+from app.config import Settings
+from app.models import Document
+from app.rag.prompts import build_deflect_prompt, build_high_prompt, build_steering_section
+from app.rag.retriever import TRUNCATION_MARKER, RetrievedChunk
+
+
+def _settings() -> Settings:
+    return Settings(_env_file=None, relevance_threshold=0.30)  # pyright: ignore[reportCallIssue]
+
+
+def _doc(title: str, content: str) -> Document:
+    return Document(
+        id=uuid.uuid4(),
+        source="Homelab",
+        path=f"{title.lower().replace(' ', '-')}.md",
+        full_path="/tmp/doc.md",
+        title=title,
+        content=content,
+        content_hash="0" * 64,
+    )
+
+
+def _chunk(doc: Document, score: float) -> RetrievedChunk:
+    return RetrievedChunk(
+        chunk_id=uuid.uuid4(),
+        position=0,
+        content=doc.content[:32],
+        score=score,
+        document=doc,
+        cosine=score,
+    )
+
+
+# ---------- build_steering_section ----------
+
+
+def test_steering_section_empty_when_no_notes() -> None:
+    assert build_steering_section([]) == ""
+
+
+def test_steering_section_empty_when_notes_are_blank() -> None:
+    assert build_steering_section(["", "   ", "\n\t"]) == ""
+
+
+def test_steering_section_single_note_numbered() -> None:
+    section = build_steering_section(["be more concise"])
+    assert section.startswith("<tuning>\n")
+    assert section.endswith("\n</tuning>")
+    assert "1. be more concise" in section
+    assert TRUNCATION_MARKER not in section
+
+
+def test_steering_section_trims_note_edges() -> None:
+    section = build_steering_section(["  be more concise  "])
+    assert "1. be more concise" in section
+    assert "1.   be more concise" not in section
+
+
+def test_steering_section_many_notes_numbered_in_order() -> None:
+    section = build_steering_section(["alpha", "beta", "gamma"])
+    assert "1. alpha" in section
+    assert "2. beta" in section
+    assert "3. gamma" in section
+    assert section.index("1. alpha") < section.index("2. beta") < section.index("3. gamma")
+    assert TRUNCATION_MARKER not in section
+
+
+def test_steering_section_budget_truncation_keeps_oldest_prefix_and_marker() -> None:
+    # Each note is 300 chars; with a 600-char budget only note 1 fits, so
+    # the oldest-fitting prefix is kept and the overflow is marked.
+    notes = [f"note-{i} " + "x" * (300 - len(f"note-{i} ")) for i in range(3)]
+    section = build_steering_section(notes, max_chars=600)
+    assert TRUNCATION_MARKER in section
+    assert len(section) <= 600
+    assert "1. note-0" in section
+    assert "note-1" not in section
+    assert "note-2" not in section
+    # The marker comes last, after the kept notes.
+    assert section.index("1. note-0") < section.index(TRUNCATION_MARKER)
+
+
+def test_steering_section_fits_budget_exactly_when_all_notes_fit() -> None:
+    section = build_steering_section(["a", "b", "c"], max_chars=10_000)
+    assert TRUNCATION_MARKER not in section
+    assert len(section) <= 10_000
+
+
+def test_steering_section_default_budget_from_settings(monkeypatch: pytest.MonkeyPatch) -> None:
+    from app.rag import prompts as prompts_mod
+
+    monkeypatch.setattr(
+        prompts_mod, "get_settings", lambda: Settings(_env_file=None)  # pyright: ignore[reportCallIssue]
+    )
+    # 5 notes of 2000 chars (the API max) = 10k+ chars > the 8000 default.
+    notes = [f"note-{i} " + "y" * (2000 - len(f"note-{i} ")) for i in range(5)]
+    section = build_steering_section(notes)
+    assert TRUNCATION_MARKER in section
+    assert len(section) <= 8_000
+
+
+def test_steering_section_nonpositive_budget_is_empty() -> None:
+    assert build_steering_section(["be concise"], max_chars=0) == ""
+    assert build_steering_section(["be concise"], max_chars=-10) == ""
+
+
+def test_steering_section_tiny_budget_never_exceeds_cap() -> None:
+    # Pathological budget: the section must never exceed the cap — bare
+    # marker when it fits, no section at all when even that doesn't.
+    assert len(build_steering_section(["a" * 500], max_chars=10)) <= 10
+    fits_marker = build_steering_section(["a" * 500], max_chars=len(TRUNCATION_MARKER))
+    assert fits_marker == TRUNCATION_MARKER
+
+
+# ---------- prompt placement (both modes) ----------
+
+
+def test_high_prompt_steering_sits_between_relevance_and_documents() -> None:
+    doc = _doc("Kubernetes Homelab Cluster", "TALOS_DOC_CONTENT")
+    prompt = build_high_prompt([doc], notes=["be concise"])
+    i_rel = prompt.index("<relevance>HIGH</relevance>")
+    i_open = prompt.index("<tuning>")
+    i_close = prompt.index("</tuning>")
+    i_docs = prompt.index("<documents>")
+    assert i_rel < i_open < i_close < i_docs
+    assert "1. be concise" in prompt
+    assert "TALOS_DOC_CONTENT" in prompt  # documents still full
+
+
+def test_deflect_prompt_steering_sits_between_relevance_and_deflect_mode() -> None:
+    prompt = build_deflect_prompt(["Title A", "Title B"], notes=["be concise", "cite paths"])
+    i_rel = prompt.index("<relevance>LOW</relevance>")
+    i_open = prompt.index("<tuning>")
+    i_close = prompt.index("</tuning>")
+    i_mode = prompt.index("DEFLECT_MODE")
+    assert i_rel < i_open < i_close < i_mode
+    assert "1. be concise" in prompt
+    assert "2. cite paths" in prompt
+    assert "- Title A" in prompt  # weak-hit titles still carried
+    assert "DEFLECT_MODE" in prompt
+
+
+# ---------- plan_turn wiring (gate + steering, fake retriever rows) ----------
+
+
+def test_plan_turn_high_mode_injects_notes() -> None:
+    doc = _doc("Kubernetes Homelab Cluster", "TALOS_DOC_SENT")
+    plan = chat_api.plan_turn(
+        [_chunk(doc, 0.90)], _settings(), notes=["be concise", "assume NixOS"]
+    )
+    assert plan.deflected is False
+    assert plan.tuning_count == 2
+    assert "<tuning>" in plan.system_prompt
+    assert "1. be concise" in plan.system_prompt
+    assert "2. assume NixOS" in plan.system_prompt
+    assert "<relevance>HIGH</relevance>" in plan.system_prompt
+    assert "TALOS_DOC_SENT" in plan.system_prompt
+
+
+def test_plan_turn_low_mode_injects_notes() -> None:
+    doc = _doc("Kubernetes Homelab Cluster", "TALOS_DOC_NEVER_SENT")
+    plan = chat_api.plan_turn(
+        [_chunk(doc, 0.10)], _settings(), notes=["be concise"]
+    )
+    assert plan.deflected is True
+    assert plan.tuning_count == 1
+    assert "DEFLECT_MODE" in plan.system_prompt
+    assert "<tuning>" in plan.system_prompt
+    assert "1. be concise" in plan.system_prompt
+    assert "TALOS_DOC_NEVER_SENT" not in plan.system_prompt  # titles only, still
+
+
+def test_plan_turn_without_notes_has_no_tuning_section() -> None:
+    doc = _doc("Kubernetes Homelab Cluster", "TALOS_DOC_SENT")
+    for chunks in (
+        [_chunk(doc, 0.90)],  # HIGH
+        [_chunk(doc, 0.10)],  # LOW
+    ):
+        plan = chat_api.plan_turn(chunks, _settings())
+        assert plan.tuning_count == 0
+        assert "<tuning>" not in plan.system_prompt