refactor(retrieval): one registry for every surface's floor and budget (#4102)

Groundwork for the step's real change. The operator's decision is that the
floor is chosen and adjusted by the model using it, not shipped as a value
somebody has to defend:

  "we need a model consistent surface for the adjustment of these floor values.
   the user should be able to touch it but the model should be the thing
   handling it 9 times out of 10."

A tuning surface cannot be consistent across six arms that each spell their
configuration differently, so the arms stop owning their numbers.
`retrieval_surfaces.SURFACES` names each one, its floor key and default, its
budget key and default, and — because they are rendered by the tuning tool and
the Settings UI — what it asks, over what corpus, and how often it fires. A
floor cannot be moved responsibly by anyone who does not know those three.

Three things fall out:

- **`k` becomes a real budget everywhere.** Only auto-inject had a configurable
  one; `RULEHINT_LIMIT`, `PROMPTRULE_LIMIT` and `reply_preferences.LIMIT` were
  constants. `k` is what binds under a low floor, so it has to be settable per
  surface — and per surface is the point, since `pre_tool_rule` fires before
  every Bash call while `prompt_rule` fires once a turn.
- **`write_path` gets its own budget, inherited not reset.** It shared
  auto-inject's outright on the argument that "how many titles at once" means
  the same thing on both. It does not, for the same reason. Unset, it still
  reads auto-inject's key, so an install that tuned the shared knob does not
  silently drop to a new default.
- **The duplicated read-and-clamp goes.** That shape is canon #2860 across 295
  of 372 judged siblings. Survivable while the numbers were constants; not once
  they are meant to move.

The long measurement comments stay exactly where they are — #2223's noise-floor
probe, #3853's command-vs-code split, #3851's band measurement. The constants
they annotate now alias the registry, so there is one value and the reasoning
still sits beside it.

Tests build the write-path config from the registry (`helpers.writepath_cfg`)
instead of from hand-written dicts. That is not tidiness: the rule arms read
their numbers inside a fail-open `except`, so a dict missing one key does not
raise where a reader would see it — the arm silently becomes a no-op that reads
exactly like "fired and found nothing". Ten hand-written dicts each looked
complete on the day they were typed.

tests/test_retrieval_surfaces.py pins the identity everything rests on: a
surface's name IS its telemetry source. Nothing in the type system says so —
`record_retrieval(source="pre_tool_rule")` is a literal in another file — and
renaming one without the other yields an arm that can be tuned and not
measured, or measured and not tuned, with no symptom either way.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/services/plugin_context.py

@@ -31,6 +31,12 @@ from scribe.services.embeddings import semantic_search_notes, semantic_search_ru
 from scribe.services.note_usage import record_surfaced
 from scribe.services.rule_usage import record_rule_surfaced
 from scribe.services.supersession import superseded_ids
+from scribe.services.retrieval_surfaces import (
+    MAX_BUDGET,
+    SURFACES,
+    budget_for,
+    floor_for,
+)
 from scribe.services.retrieval_telemetry import record_retrieval
 from scribe.services.settings import get_setting
 
@@ -54,12 +60,16 @@ _GOAL_CHARS = 200
 # and are meant to be tuned from retrieval_logs (source='auto_inject') once data
 # accrues — they're exposed in the Settings UI, no restart needed.
 AUTOINJECT_ENABLED_KEY = "kb_autoinject_enabled"
-AUTOINJECT_THRESHOLD_KEY = "kb_autoinject_threshold"
-AUTOINJECT_TOP_K_KEY = "kb_autoinject_top_k"
+# The key and the value both live in the registry now (#4102); these names
+# survive because the comments above them are where each number's measurement
+# is recorded, and because the Settings UI agreement test pairs them with the
+# Vue refs by name. One definition, two readable places.
+AUTOINJECT_THRESHOLD_KEY = SURFACES["auto_inject"].floor_key
+AUTOINJECT_TOP_K_KEY = SURFACES["auto_inject"].budget_key
 
 AUTOINJECT_DEFAULT_ENABLED = True
-AUTOINJECT_DEFAULT_THRESHOLD = 0.55
-AUTOINJECT_DEFAULT_TOP_K = 3
+AUTOINJECT_DEFAULT_THRESHOLD = SURFACES["auto_inject"].floor_default
+AUTOINJECT_DEFAULT_TOP_K = SURFACES["auto_inject"].budget_default
 
 # The write-path trigger (#2082) gets its own on/off switch, its own threshold,
 # and shares only top-k. It originally shared the threshold too, on the argument
@@ -83,9 +93,9 @@ AUTOINJECT_DEFAULT_TOP_K = 3
 # pull-through (#2085) once a real corpus accrues; a cross-encoder rerank
 # (#1038) would subsume this bump.
 WRITEPATH_ENABLED_KEY = "kb_writepath_enabled"
-WRITEPATH_THRESHOLD_KEY = "kb_writepath_threshold"
+WRITEPATH_THRESHOLD_KEY = SURFACES["write_path"].floor_key
 WRITEPATH_DEFAULT_ENABLED = True
-WRITEPATH_DEFAULT_THRESHOLD = 0.68
+WRITEPATH_DEFAULT_THRESHOLD = SURFACES["write_path"].floor_default
 
 # The standing-rule arm (milestone 307) gets its own bar — the split #2223 made
 # one surface down, now made for the THIRD corpus. It inherited 0.68 above, and
@@ -133,8 +143,8 @@ WRITEPATH_DEFAULT_THRESHOLD = 0.68
 # case 0.72 was calibrated on, and the telemetry says it is working — the
 # write-path rule arm speaks on 37% of its calls and its refused mass sits at
 # p50 0.6989, comfortably under the bar rather than piled against it.
-RULEHINT_THRESHOLD_KEY = "kb_rulehint_threshold"
-RULEHINT_DEFAULT_THRESHOLD = 0.72
+RULEHINT_THRESHOLD_KEY = SURFACES["write_path_rule"].floor_key
+RULEHINT_DEFAULT_THRESHOLD = SURFACES["write_path_rule"].floor_default
 
 # THE COMMAND ARM'S OWN BAR, AND WHY IT IS NOT THE WRITE PATH'S (#3853).
 #
@@ -193,8 +203,8 @@ RULEHINT_DEFAULT_THRESHOLD = 0.72
 # eligible. Retrieval is ownership-scoped, not project-scoped. Scoping it
 # would drop that ceiling and widen the 0.0115, which is the larger fix and
 # the reason to settle project scoping before tuning this number twice.
-TOOLRULE_THRESHOLD_KEY = "kb_toolrule_threshold"
-TOOLRULE_DEFAULT_THRESHOLD = 0.68
+TOOLRULE_THRESHOLD_KEY = SURFACES["pre_tool_rule"].floor_key
+TOOLRULE_DEFAULT_THRESHOLD = SURFACES["pre_tool_rule"].floor_default
 
 # A SET OF RULES PER ACT, NOT THE SINGLE BEST ONE (#3851).
 #
@@ -223,7 +233,10 @@ TOOLRULE_DEFAULT_THRESHOLD = 0.68
 # and nothing else, so a moment with one clearly-relevant rule still shows
 # one, and a moment with four shows four. The corpus decides, not a constant.
 # The cap survives as a ceiling on the worst case, not as the usual answer.
-RULEHINT_LIMIT = 5
+# NOW A DEFAULT RATHER THAN A CAP (#4102): both rule act-arms read their own
+# budget from the registry, so this is the value an install starts at and not
+# the value it is stuck with. The reasoning below is why 5 is where it starts.
+RULEHINT_LIMIT = SURFACES["write_path_rule"].budget_default
 
 # MEASURED, NOT REASONED — and the reasoning it replaced was wrong (#3851).
 #
@@ -433,7 +446,11 @@ _CONCEPT_MIN_CHARS = 16
 _AUTOINJECT_BAND = 0.10
 # Hard ceiling on top-k regardless of the user's setting — this is an
 # awareness menu (titles only), never a content dump.
-_AUTOINJECT_MAX_TOP_K = 10
+# The budget ceiling, now shared by every surface rather than owned by this
+# one (#4102). It bounds the same thing everywhere — how many lines a single
+# unsolicited injection may occupy — so one surface having a private ceiling
+# was an accident of which arm got a configurable budget first.
+_AUTOINJECT_MAX_TOP_K = MAX_BUDGET
 
 # --- the prompt-boundary rule arm (#3852) ------------------------------------
 #
@@ -446,7 +463,7 @@ _AUTOINJECT_MAX_TOP_K = 10
 # The operator's message is the only query that exists before one is composed,
 # and this arm is what runs against it. Until now that hook searched notes
 # alone, so no rule had ever been retrieved against a thing the operator said.
-PROMPTRULE_THRESHOLD_KEY = "kb_promptrule_threshold"
+PROMPTRULE_THRESHOLD_KEY = SURFACES["prompt_rule"].floor_key
 # INHERITED FROM THE ACT ARMS, AND NOT YET EARNED HERE. 0.72 was tuned against
 # code and shell commands. An operator's prose is a different query shape
 # against the same documents, and nothing yet says the two distributions line
@@ -458,7 +475,7 @@ PROMPTRULE_THRESHOLD_KEY = "kb_promptrule_threshold"
 # front of a corpus that binds. Every call is logged under `prompt_rule` from
 # the first deploy, so a few days of real traffic settles it — read
 # `near_miss_samples` (#3807) before moving this, not the percentile alone.
-PROMPTRULE_DEFAULT_THRESHOLD = 0.72
+PROMPTRULE_DEFAULT_THRESHOLD = SURFACES["prompt_rule"].floor_default
 
 # MORE THAN THE ACT ARMS' SINGLE SLOT, anchored on this hook's budget rather
 # than theirs. RULEHINT_LIMIT is 1 because that arm fires before EVERY Bash
@@ -469,7 +486,7 @@ PROMPTRULE_DEFAULT_THRESHOLD = 0.72
 # And a prompt genuinely contains more than one act. "Merge to main and then
 # start on X" is two, governed by different rules; k=1 cannot serve that case
 # at all, where the act arms never face it because a command is one thing.
-PROMPTRULE_LIMIT = 3
+PROMPTRULE_LIMIT = SURFACES["prompt_rule"].budget_default
 
 # THE COMPLETION-REPORT ARM'S OWN BAR (services/reply_preferences.py).
 #
@@ -487,8 +504,8 @@ PROMPTRULE_LIMIT = 3
 # Kept at the prose arm's starting value rather than tuned: the split is what
 # makes the two independently movable, and a default is a product decision
 # that this install's corpus cannot settle (rule 115).
-REPORTPREF_THRESHOLD_KEY = "kb_reportpref_threshold"
-REPORTPREF_DEFAULT_THRESHOLD = 0.72
+REPORTPREF_THRESHOLD_KEY = SURFACES["report_preference"].floor_key
+REPORTPREF_DEFAULT_THRESHOLD = SURFACES["report_preference"].floor_default
 
 
 def _slugify(text: str) -> str:
@@ -592,8 +609,18 @@ async def build_process_manifest(user_id: int) -> dict:
 async def get_autoinject_config(user_id: int) -> dict:
     """Resolve a user's auto-inject settings, falling back to the defaults.
 
-    Returns {"enabled": bool, "threshold": float, "top_k": int}, clamped to
-    sane ranges (threshold to [0,1]; top_k to [1, _AUTOINJECT_MAX_TOP_K]).
+    Returns {"enabled": bool, "threshold": float, "top_k": int}.
+
+    THE TWO NUMBERS COME FROM THE REGISTRY NOW (#4102). They used to be read and
+    clamped here, and identically again in `get_writepath_config`, and again in
+    three rule arms, and once more in `reply_preferences` — the duplication the
+    shape ledger counts as canon #2860 across 295 of 372 siblings. That was
+    tolerable while the values were shipped constants. It stops being tolerable
+    once a tool is expected to MOVE them, because a tuning surface cannot be
+    consistent across arms that each spell their configuration differently.
+
+    `enabled` stays here: it is this surface's own switch, not a tunable number,
+    and the registry deliberately holds only the pair a floor-tuner touches.
     """
     enabled_raw = await get_setting(
         user_id, AUTOINJECT_ENABLED_KEY,
@@ -601,21 +628,11 @@ async def get_autoinject_config(user_id: int) -> dict:
     )
     enabled = enabled_raw.strip().lower() in ("true", "1", "yes", "on")
 
-    try:
-        threshold = float(await get_setting(
-            user_id, AUTOINJECT_THRESHOLD_KEY, str(AUTOINJECT_DEFAULT_THRESHOLD)))
-    except (TypeError, ValueError):
-        threshold = AUTOINJECT_DEFAULT_THRESHOLD
-    threshold = min(1.0, max(0.0, threshold))
-
-    try:
-        top_k = int(float(await get_setting(
-            user_id, AUTOINJECT_TOP_K_KEY, str(AUTOINJECT_DEFAULT_TOP_K))))
-    except (TypeError, ValueError):
-        top_k = AUTOINJECT_DEFAULT_TOP_K
-    top_k = min(_AUTOINJECT_MAX_TOP_K, max(1, top_k))
-
-    return {"enabled": enabled, "threshold": threshold, "top_k": top_k}
+    return {
+        "enabled": enabled,
+        "threshold": await floor_for(user_id, "auto_inject"),
+        "top_k": await budget_for(user_id, "auto_inject"),
+    }
 
 
 def _record_kind(note) -> str:
@@ -1024,13 +1041,8 @@ async def build_prompt_rule_hint(
         return out
 
     try:
-        try:
-            threshold = float(await get_setting(
-                user_id, PROMPTRULE_THRESHOLD_KEY,
-                str(PROMPTRULE_DEFAULT_THRESHOLD)))
-        except (TypeError, ValueError):
-            threshold = PROMPTRULE_DEFAULT_THRESHOLD
-        threshold = min(1.0, max(0.0, threshold))
+        threshold = await floor_for(user_id, "prompt_rule")
+        limit = await budget_for(user_id, "prompt_rule")
 
         t0 = time.perf_counter()
         _rep: dict = {}
@@ -1041,7 +1053,7 @@ async def build_prompt_rule_hint(
         # sessions — this surface speaks unasked, and a whole-rulebook answer
         # is only right for someone who asked the whole rulebook.
         hits = await semantic_search_rules(
-            user_id, q, limit=PROMPTRULE_LIMIT, threshold=threshold,
+            user_id, q, limit=limit, threshold=threshold,
             report=_rep, project_id=project_id or None,
         )
         duration_ms = (time.perf_counter() - t0) * 1000.0
@@ -1057,7 +1069,7 @@ async def build_prompt_rule_hint(
         # and unverified for this corpus, so the zero rows are the point.
         record_retrieval(
             user_id=user_id, source="prompt_rule", query=q,
-            threshold=threshold, limit=PROMPTRULE_LIMIT,
+            threshold=threshold, limit=limit,
             project_id=project_id,
             is_task=None, results=fresh, duration_ms=duration_ms,
             best_available=_rep.get("best_available_score"),
@@ -1294,52 +1306,37 @@ def concept_query(code: str) -> str:
 
 
 async def get_writepath_config(user_id: int) -> dict:
-    """Write-path trigger settings: its own `enabled` and `threshold`, auto-inject's top_k.
+    """Write-path trigger settings — and the two rule arms' numbers alongside.
 
-    The threshold OVERRIDES the inherited auto-inject value — code embeddings
-    have a much higher similarity floor than prose, so the two surfaces need
-    different bars. See WRITEPATH_DEFAULT_THRESHOLD for the measurements (#2223).
-    top_k is still shared: "how many titles at once" means the same thing on
-    both surfaces, and nothing suggests they want different ceilings.
+    Three surfaces' worth of configuration arrives in one call because one hook
+    request drives all three arms. They are still three SURFACES with three
+    independent pairs, resolved from the registry (#4102).
+
+    The floors were split apart one at a time, each on its own measurement, and
+    those measurements are recorded where the defaults are: WRITEPATH (#2223 —
+    code embeddings sit on a much higher similarity floor than prose), RULEHINT
+    (a third corpus again), TOOLRULE (#3853 — a shell command is a different
+    query shape from a code payload and scores lower for the same relevance).
+
+    THE BUDGET IS NOW SPLIT TOO. `top_k` used to be auto-inject's outright, on
+    the argument that "how many titles at once" means the same thing on both
+    surfaces. It does not: this arm fires before every Write and Edit while
+    auto-inject fires once a turn, so the same number buys wildly different
+    amounts of attention. `write_path` inherits auto-inject's value when it has
+    none of its own, so no install that tuned the shared knob loses it.
     """
-    cfg = await get_autoinject_config(user_id)
     enabled_raw = await get_setting(
         user_id, WRITEPATH_ENABLED_KEY,
         "true" if WRITEPATH_DEFAULT_ENABLED else "false",
     )
-
-    try:
-        threshold = float(await get_setting(
-            user_id, WRITEPATH_THRESHOLD_KEY, str(WRITEPATH_DEFAULT_THRESHOLD)))
-    except (TypeError, ValueError):
-        threshold = WRITEPATH_DEFAULT_THRESHOLD
-    threshold = min(1.0, max(0.0, threshold))
-
-    try:
-        rule_threshold = float(await get_setting(
-            user_id, RULEHINT_THRESHOLD_KEY, str(RULEHINT_DEFAULT_THRESHOLD)))
-    except (TypeError, ValueError):
-        rule_threshold = RULEHINT_DEFAULT_THRESHOLD
-    rule_threshold = min(1.0, max(0.0, rule_threshold))
-
-    try:
-        tool_rule_threshold = float(await get_setting(
-            user_id, TOOLRULE_THRESHOLD_KEY, str(TOOLRULE_DEFAULT_THRESHOLD)))
-    except (TypeError, ValueError):
-        tool_rule_threshold = TOOLRULE_DEFAULT_THRESHOLD
-    tool_rule_threshold = min(1.0, max(0.0, tool_rule_threshold))
-
     return {
-        **cfg,
         "enabled": enabled_raw.strip().lower() in ("true", "1", "yes", "on"),
-        "threshold": threshold,
-        # Its own bar, for a third corpus — see RULEHINT_DEFAULT_THRESHOLD.
-        "rule_threshold": rule_threshold,
-        # And the COMMAND arm's own bar again, for the same reason one level
-        # down: a shell command is a different query shape from a code payload
-        # and scores lower for the same relevance (#3853). Separate keys, so an
-        # install can move one without the other — which is the whole finding.
-        "tool_rule_threshold": tool_rule_threshold,
+        "threshold": await floor_for(user_id, "write_path"),
+        "top_k": await budget_for(user_id, "write_path"),
+        "rule_threshold": await floor_for(user_id, "write_path_rule"),
+        "rule_top_k": await budget_for(user_id, "write_path_rule"),
+        "tool_rule_threshold": await floor_for(user_id, "pre_tool_rule"),
+        "tool_rule_top_k": await budget_for(user_id, "pre_tool_rule"),
     }
 
 def _rule_band(hits: list) -> list:
@@ -1988,7 +1985,7 @@ async def build_write_path_hint(
         rule_t0 = time.perf_counter()
         _rep_wpr: dict = {}
         hits = await semantic_search_rules(
-            user_id, code or path, limit=RULEHINT_LIMIT,
+            user_id, code or path, limit=cfg["rule_top_k"],
             threshold=cfg["rule_threshold"],
             report=_rep_wpr, project_id=project_id or None,
         )
@@ -2049,7 +2046,7 @@ async def build_write_path_hint(
         # the same readout.
         record_retrieval(
             user_id=user_id, source="write_path_rule", query=code or path,
-            threshold=cfg["rule_threshold"], limit=RULEHINT_LIMIT,
+            threshold=cfg["rule_threshold"], limit=cfg["rule_top_k"],
             project_id=project_id,
             is_task=None, results=fresh, duration_ms=rule_ms,
             best_available=_rep_wpr.get("best_available_score"),
@@ -2145,7 +2142,7 @@ async def build_tool_rule_hint(
         t0 = time.perf_counter()
         _rep_ptr: dict = {}
         hits = await semantic_search_rules(
-            user_id, query, limit=RULEHINT_LIMIT,
+            user_id, query, limit=cfg["tool_rule_top_k"],
             threshold=cfg["tool_rule_threshold"],
             report=_rep_ptr, project_id=project_id or None,
         )
@@ -2168,7 +2165,7 @@ async def build_tool_rule_hint(
         # failure the arm was built to stop.
         record_retrieval(
             user_id=user_id, source="pre_tool_rule", query=query,
-            threshold=cfg["tool_rule_threshold"], limit=RULEHINT_LIMIT,
+            threshold=cfg["tool_rule_threshold"], limit=cfg["tool_rule_top_k"],
             project_id=project_id,
             is_task=None, results=fresh, duration_ms=duration_ms,
             best_available=_rep_ptr.get("best_available_score"),

src/scribe/services/reply_preferences.py

@@ -61,13 +61,9 @@ import logging
 import time
 
 from scribe.services.embeddings import semantic_search_rules
-from scribe.services.plugin_context import (
-    REPORTPREF_DEFAULT_THRESHOLD,
-    REPORTPREF_THRESHOLD_KEY,
-)
+from scribe.services.retrieval_surfaces import SURFACES, budget_for, floor_for
 from scribe.services.retrieval_telemetry import record_retrieval
 from scribe.services.rule_usage import record_rule_surfaced
-from scribe.services.settings import get_setting
 
 logger = logging.getLogger(__name__)
 
@@ -85,16 +81,20 @@ COMPLETION_QUERY = (
 # A handful, not a menu. More than a few shape preferences for ONE kind of
 # reply would contradict each other before they helped; the limit is here to
 # keep one noisy corpus from turning a status change into a wall of text.
-LIMIT = 3
+# The STARTING budget, not the budget (#4102). Both numbers this arm runs on
+# now come from the surface registry, so the model that reads this arm's
+# telemetry can move either — which matters more here than anywhere else,
+# because a fixed query makes this arm's score a constant and a floor a hair
+# above it produces a dead arm no amount of traffic will ever reveal.
+LIMIT = SURFACES["report_preference"].budget_default
 
 
 async def _threshold(user_id: int) -> float:
-    try:
-        value = float(await get_setting(
-            user_id, REPORTPREF_THRESHOLD_KEY, str(REPORTPREF_DEFAULT_THRESHOLD)))
-    except (TypeError, ValueError):
-        value = REPORTPREF_DEFAULT_THRESHOLD
-    return min(1.0, max(0.0, value))
+    return await floor_for(user_id, SOURCE)
+
+
+async def _limit(user_id: int) -> int:
+    return await budget_for(user_id, SOURCE)
 
 
 async def completion_preferences(user_id: int, *, project_id: int | None = None) -> list[dict]:
@@ -115,16 +115,17 @@ async def completion_preferences(user_id: int, *, project_id: int | None = None)
     """
     try:
         threshold = await _threshold(user_id)
+        limit = await _limit(user_id)
         report: dict = {}
         t0 = time.perf_counter()
         hits = await semantic_search_rules(
-            user_id, COMPLETION_QUERY, limit=LIMIT, threshold=threshold,
+            user_id, COMPLETION_QUERY, limit=limit, threshold=threshold,
             kind="preference", report=report, project_id=project_id,
         )
         hits = [(score, rule) for score, rule in hits if rule.kind == "preference"]
         record_retrieval(
             user_id=user_id, source=SOURCE, query=COMPLETION_QUERY,
-            threshold=threshold, limit=LIMIT, project_id=project_id,
+            threshold=threshold, limit=limit, project_id=project_id,
             is_task=None, results=hits,
             best_available=report.get("best_available_score"),
             best_available_id=report.get("best_available_id"),

src/scribe/services/retrieval_surfaces.py

@@ -0,0 +1,243 @@
+"""One registry of the retrieval surfaces, and the two numbers each one has (#4102).
+
+WHY THIS EXISTS
+
+Six push arms each carried their own loose copy of the same shape: a settings
+key, a default, and a limit that was usually a module constant nobody could
+change. `_threshold()` was duplicated so widely that the shape ledger counts it
+as canon across 295 of 372 judged siblings (snippet #2860). That was survivable
+while the numbers were shipped constants an operator occasionally edited.
+
+It stops being survivable once the numbers are meant to MOVE. The operator's
+decision for this step:
+
+    "the floor should be chosen and adjusted by the model using it. we've come
+    back to something either fails or has to be looked at by the user we need a
+    model consistent surface for the adjustment of these floor values. the user
+    should be able to touch it but the model should be the thing handling it 9
+    times out of 10."
+
+A tuning surface cannot be "model consistent" if every arm spells its own
+configuration differently. So the arms stop owning their numbers and read them
+from here instead, and the tuning tool, the routes and the Settings UI all
+enumerate THIS table rather than hard-coding six special cases.
+
+WHAT A FLOOR IS NOW, AND WHAT IT IS NOT
+
+It is not a relevance judgement. Relevance is decided by the reader, which is
+the only participant that can read a trigger against a situation — that is the
+milestone's whole argument, and the injected line has always said so out loud
+("read it before deciding it does not apply").
+
+A floor answers the cheaper question: *is this worth ranking at all*. `k` is
+what binds, and `k` is a BUDGET — how much of this surface's attention a
+candidate list may spend. An arm that fires before every Bash call cannot
+afford what an arm that fires once a turn can.
+
+WHY THE DEFAULTS BELOW ARE STARTING POINTS AND NOT ANSWERS
+
+A cosine score is a distance in BAAI/bge-small-en-v1.5's vector space, measured
+against THIS corpus. It cannot transfer to an install with different records,
+and rule 115 forbids defending a shipped default from this instance's
+telemetry — which is what made the old design unbuildable: every number was a
+guess everywhere except here, and there was no mechanism that could ever
+improve it.
+
+The mechanism is the fix. Scribe ships a starting point and the means to
+correct it, so the values below carry the measurement that motivated them (see
+the long comments in `plugin_context.py`, which are kept where they are because
+they record how each number was first arrived at) without claiming to be right
+for anybody else.
+
+HOW A FLOOR SHOULD ACTUALLY BE MOVED
+
+By reading the records the floor refused — `retrieval_telemetry(
+near_miss_samples=N)` returns them by id — and never by the percentile alone.
+That is not a style preference; it is the one case where the two disagreed and
+was checked. `report_preference` logged 69 consecutive declines with the
+refused score 0.0006 under the bar, and every percentile said "lower it".
+Reading the refused record showed it was rule 77 "Extract intent from loose
+phrasing", a false positive, so lowering the bar would have delivered that rule
+on every completion report ever written. The statistic and the correct action
+pointed in opposite directions, and only opening the record could tell.
+"""
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from scribe.services.settings import get_setting
+
+# A budget nobody should be able to set past. Not a tuning value — a guard on
+# the worst case, so a mistyped setting cannot turn a menu into a wall of text.
+# Shared by every surface because it bounds the same thing everywhere: how many
+# lines a single unsolicited injection may occupy.
+MAX_BUDGET = 10
+
+
+@dataclass(frozen=True)
+class Surface:
+    """One push arm's tunable pair, plus enough prose to tune it responsibly.
+
+    `asks` / `over` / `fires` are not documentation for this file — they are
+    rendered by the tuning tool and the Settings UI. A floor cannot be moved
+    sensibly by anyone, model or human, who does not know what the query is, what
+    corpus it runs against, or how often it costs something. Those three facts
+    are exactly what separates these arms from each other, and they were
+    previously recoverable only by reading `plugin_context.py`.
+    """
+
+    name: str
+    """The telemetry `source` value, and the join key.
+
+    MUST equal the string this arm passes to `record_retrieval`. Everything
+    useful about tuning depends on that identity: the tool that moves a floor
+    and the table that says what the floor did have to be talking about the same
+    arm. A test asserts it rather than a comment asking nicely.
+    """
+
+    floor_key: str
+    floor_default: float
+    budget_key: str
+    budget_default: int
+    asks: str
+    over: str
+    fires: str
+    budget_falls_back_to: str = ""
+    """A budget key to inherit when this surface has none of its own set.
+
+    Only `write_path` uses it, and only because it USED to share auto-inject's
+    `top_k` outright. Giving it a key without this would silently reset the
+    budget of every install that had tuned the shared one — a behaviour change
+    delivered as a default, which is the shape of regression nobody reports
+    because nothing looks broken.
+    """
+
+
+SURFACES: dict[str, Surface] = {
+    "auto_inject": Surface(
+        name="auto_inject",
+        floor_key="kb_autoinject_threshold",
+        floor_default=0.55,
+        budget_key="kb_autoinject_top_k",
+        budget_default=3,
+        asks="the operator's message, as they typed it",
+        over="notes, snippets, processes and issues",
+        fires="once per operator turn",
+    ),
+    "write_path": Surface(
+        name="write_path",
+        floor_key="kb_writepath_threshold",
+        floor_default=0.68,
+        budget_key="kb_writepath_top_k",
+        budget_default=3,
+        budget_falls_back_to="kb_autoinject_top_k",
+        asks="the code being written, rewritten as a concept query",
+        over="snippets and recorded issues",
+        fires="before every Write and Edit",
+    ),
+    "write_path_rule": Surface(
+        name="write_path_rule",
+        floor_key="kb_rulehint_threshold",
+        floor_default=0.72,
+        budget_key="kb_rulehint_top_k",
+        budget_default=5,
+        asks="the code being written, against rule triggers",
+        over="global rules plus the bound project's own",
+        fires="before every Write and Edit",
+    ),
+    "pre_tool_rule": Surface(
+        name="pre_tool_rule",
+        floor_key="kb_toolrule_threshold",
+        floor_default=0.68,
+        budget_key="kb_toolrule_top_k",
+        budget_default=5,
+        asks="the command about to run, against rule triggers",
+        over="global rules plus the bound project's own",
+        fires="before every Bash call — the busiest arm there is",
+    ),
+    "prompt_rule": Surface(
+        name="prompt_rule",
+        floor_key="kb_promptrule_threshold",
+        floor_default=0.72,
+        budget_key="kb_promptrule_top_k",
+        budget_default=3,
+        asks="the operator's message, against rule triggers",
+        over="global rules plus the bound project's own",
+        fires="once per operator turn",
+    ),
+    "report_preference": Surface(
+        name="report_preference",
+        floor_key="kb_reportpref_threshold",
+        floor_default=0.72,
+        budget_key="kb_reportpref_top_k",
+        budget_default=3,
+        # THE ONE FIXED QUERY, and the reason this arm behaves unlike the rest.
+        # The others score something that varies per call; this one scores a
+        # constant string, so its top score for a given corpus is also a
+        # constant. A floor a hair above that constant is not a quiet arm, it is
+        # a dead one, and no amount of traffic will ever reveal it — which is
+        # precisely how this arm spent 69 calls declining the same record.
+        asks="a fixed question about how to lay out a completion report",
+        over="preferences",
+        fires="when a task finishes",
+    ),
+}
+
+# Reserved slots are deliberately absent. `preference_slot` and `reuse_slot`
+# borrow their parent arm's floor and are hard-limited to one hit each, because
+# their entire purpose is to guarantee a single line to a kind of record that
+# keeps losing a general score contest (#2246, #3894). A budget of "1" is the
+# feature; exposing it as tunable would invite setting it to 0 and silently
+# removing the guarantee.
+
+
+def surface_names() -> list[str]:
+    """Every tunable surface, in a stable order for menus and listings."""
+    return list(SURFACES)
+
+
+def get_surface(name: str) -> Surface:
+    """Look one up, refusing an unknown name loudly.
+
+    A typo'd surface must not be writable. Settings keys are free-form strings
+    in a generic table, so a tuning call naming `pretool_rule` would otherwise
+    write a key nothing ever reads — a change that appears to succeed, reports a
+    new value, and alters nothing.
+    """
+    try:
+        return SURFACES[name]
+    except KeyError:
+        raise ValueError(
+            f"unknown retrieval surface {name!r}. Tunable surfaces are: "
+            + ", ".join(surface_names())
+        ) from None
+
+
+async def floor_for(user_id: int, name: str) -> float:
+    """This install's current floor for a surface, clamped to [0, 1]."""
+    s = get_surface(name)
+    try:
+        value = float(await get_setting(user_id, s.floor_key, str(s.floor_default)))
+    except (TypeError, ValueError):
+        value = s.floor_default
+    return min(1.0, max(0.0, value))
+
+
+async def budget_for(user_id: int, name: str) -> int:
+    """This install's current budget for a surface, clamped to [1, MAX_BUDGET].
+
+    The lower clamp is 1, never 0: a surface turned off is turned off by its
+    `enabled` switch, which says so. A budget of zero would be an arm that runs
+    a search, logs a retrieval, and renders nothing — indistinguishable in the
+    telemetry from a bar nothing cleared, which is the exact confusion this
+    milestone exists to remove.
+    """
+    s = get_surface(name)
+    raw = await get_setting(user_id, s.budget_key, "")
+    if not raw and s.budget_falls_back_to:
+        raw = await get_setting(user_id, s.budget_falls_back_to, "")
+    try:
+        value = int(float(raw)) if raw else s.budget_default
+    except (TypeError, ValueError):
+        value = s.budget_default
+    return min(MAX_BUDGET, max(1, value))