kernel(validate): resolution invariants

Widen Validate.run to take the rite's sanctoral layer alongside the rite
itself (Calendar.year needs both), and add five checks over the fully
resolved liturgical year, on top of the existing temporal-only pass:

- observed: a day's observed celebration never also appears among that
  same day's own commemorations/omissions.
- lost: no sanctoral entry is silently dropped. Per slug, the number of
  times it is actually sighted (observed + commemorations + omitted,
  summed over the year) must never fall below the number of times its
  own Date_spec resolves within the year's span -- also fires if
  resolving the year raises at all, the most total form of loss.
- duplicated: the same per-slug count must never exceed the number of
  Date_spec resolutions either. Deliberately NOT "no slug appears
  twice": a fixed date can legitimately resolve twice in the ~20% of
  liturgical years whose 371-day span reaches it on both ends (30
  November/St Andrew is the worked example in validate.mli).
- unconverged: no day's omitted reason indicates Calendar's placement
  pass hit its round guard before reaching a fixed point.
- admission: the rite's own rules.admit is a fixed point on what it
  already admitted -- the rite-agnostic form of "the admission limit
  was not exceeded" available without embedding a rite's own numeric
  caps (RG 111's, for EF) into kernel code.

Each check has a dedicated negative fixture in the synthetic rite
(test_validate.ml), hand-traced against Calendar's actual resolution
mechanics before writing the assertion, and verified to fail for the
right reason against the code before this change. One pair
(unconverged/duplicated) is not fully independent: hitting the round
guard genuinely also trips duplicated, a real consequence of Calendar's
own accounting once a candidate is simultaneously sighted at its
permanent natural date and wherever the last placement round left it --
documented in guard_rules's own comment, not papered over.

test_validate.ml's ef_rite/run now use the real Rite_ef.context and the
real bootstrapped data/ef layer (Precedence_ef and the sanctoral
bootstrap did not exist when this scaffolding was first written) rather
than the earlier placeholder rules. Validate is clean across the whole
1583..9999 domain against real EF data except the one already-documented
year-9999 truncation case (test_year_9999_does_not_raise).

3 files changed, 458 insertions, 27 deletions

diff --git a/lib/kernel/validate.ml b/lib/kernel/validate.ml
index c6501a9..d8de31b 100644
--- a/lib/kernel/validate.ml
+++ b/lib/kernel/validate.ml
@@ -20,7 +20,20 @@ let has_duplicate strings =
   let rec go = function a :: (b :: _ as rest) -> a = b || go rest | _ -> false in
   go sorted
 
-let run (rite : ('s, 'r) Rite.t) ~year =
+(* Task 12's "unconverged" check has no structural signal to key off --
+   Calendar's placement pass records its round-guard reason as a plain
+   string in [Liturgical_day.omitted] (calendar.ml's own [unconverged_reason],
+   not exposed as a public constant), and [Liturgical_day.omitted]'s own doc
+   comment says exactly this check is meant to read it. A short, distinctive
+   substring rather than the full literal keeps the coupling to calendar.ml's
+   exact wording as loose as it can be while still being unambiguous: nothing
+   else this kernel emits into [omitted] talks about "converging". *)
+let contains_substring s ~needle =
+  let ls = String.length s and ln = String.length needle in
+  let rec at i = i + ln <= ls && (String.sub s i ln = needle || at (i + 1)) in
+  ln = 0 || at 0
+
+let run (rite : ('s, 'r) Rite.t) (layer : 'r Layer.t) ~year =
   let vocab = rite.Rite.vocab in
   let year_start = rite.Rite.year_start in
   let temporal = rite.Rite.temporal in
@@ -164,4 +177,121 @@ let run (rite : ('s, 'r) Rite.t) ~year =
           if actual <> expected_slug then
             fail date "anchor" (Printf.sprintf "expected slug %S, got %S" expected_slug actual))
     anchor_pairs;
+  (* Resolution invariants (Task 12): everything above only ever asked
+     [rite.temporal] for a date's office in isolation. From here on the
+     LITURGICAL YEAR IS ACTUALLY RESOLVED against [layer] -- occurrence,
+     transfer placement, commemorations, the works (spec §2.4) -- and the
+     result checked for five further properties a temporal-only pass cannot
+     see at all. [days] (the walk built above) is reused rather than
+     recomputed: it names exactly the same [start, stop] span
+     {!Calendar.year} resolves for this [year]. *)
+  (match Calendar.year rite layer year with
+   | exception exn ->
+       (* The kernel contract forbids [run] itself from ever raising on
+          in-range input, and an exception escaping resolution is the most
+          total form of "silently lost" there is: nothing about this year's
+          sanctoral entries could be verified as accounted for at all. *)
+       fail start "lost"
+         (Printf.sprintf "resolving the year raised (%s); nothing could be verified as accounted for"
+            (Printexc.to_string exn))
+   | resolved ->
+       let idx = Layer.index_by_date layer in
+       let bump tbl slug = Hashtbl.replace tbl slug (1 + (try Hashtbl.find tbl slug with Not_found -> 0)) in
+       (* Expected: how many times each layer entry's own Date_spec resolves
+          within [start, stop]. Walking dates and querying [Layer.on_date]
+          (rather than resolving each entry's Date_spec against candidate
+          civil years directly) is what naturally counts a fixed late-
+          November date TWICE in the ~20% of liturgical years whose 371-day
+          span reaches it on both ends -- see validate.mli's own note on 30
+          November / St Andrew. *)
+       let expected : (string, int) Hashtbl.t = Hashtbl.create 64 in
+       List.iter
+         (fun date ->
+           Layer.on_date idx ~month:(Date.month date) ~day:(Date.day date)
+           |> List.iter (fun (e : 'r Layer.entry) ->
+                  bump expected (Slug.to_string e.Layer.cel.Celebration.slug)))
+         days;
+       (* Actual: how many times each slug is actually sighted across the
+          resolved year. Deliberately [observed] + [commemorations] +
+          [omitted] only, NOT [transferred_out]: a successfully transferred
+          celebration is already counted once, via [observed] (+
+          [transferred_in]) on the day it lands; also counting
+          [transferred_out] at the day it left would double-book every clean
+          transfer, which is exactly what this check exists to catch, not
+          cause. *)
+       let actual : (string, int) Hashtbl.t = Hashtbl.create 64 in
+       let bump_cel tbl (c : 'r Celebration.t) = bump tbl (Slug.to_string c.Celebration.slug) in
+       Array.iter
+         (fun (d : ('s, 'r) Liturgical_day.t) ->
+           bump_cel actual d.Liturgical_day.observed;
+           List.iter (fun (c, _) -> bump_cel actual c) d.Liturgical_day.commemorations;
+           List.iter (fun (c, _) -> bump_cel actual c) d.Liturgical_day.omitted)
+         resolved;
+       Hashtbl.fold (fun slug exp acc -> (slug, exp) :: acc) expected []
+       |> List.sort compare (* stable failure order: Hashtbl.iter's own order is hash-seed-dependent *)
+       |> List.iter (fun (slug, exp) ->
+              let act = try Hashtbl.find actual slug with Not_found -> 0 in
+              if act < exp then
+                fail start "lost"
+                  (Printf.sprintf "%s: sighted %d time(s) this year, but its own Date_spec resolves %d"
+                     slug act exp)
+              else if act > exp then
+                fail start "duplicated"
+                  (Printf.sprintf "%s: sighted %d time(s) this year, but its own Date_spec resolves only %d"
+                     slug act exp));
+       Array.iter
+         (fun (d : ('s, 'r) Liturgical_day.t) ->
+           let date = d.Liturgical_day.date in
+           let observed_slug = Slug.to_string d.Liturgical_day.observed.Celebration.slug in
+           let has_slug (c, _) = Slug.to_string c.Celebration.slug = observed_slug in
+           (* "observed": the day's own winner must not ALSO be listed as one
+              of its own losers -- see validate.mli's own note on why this is
+              reachable (two distinct layer entries sharing a slug, one
+              transferred onto the other's natural date, the transferred one
+              winning) despite {!Precedence.resolve}'s fold never letting the
+              SAME candidate value appear as both winner and loser. *)
+           if List.exists has_slug d.Liturgical_day.commemorations
+              || List.exists has_slug d.Liturgical_day.omitted
+           then
+             fail date "observed"
+               (Printf.sprintf
+                  "%s is this day's observed celebration and also appears among its own \
+                   commemorations/omissions"
+                  observed_slug);
+           (* "unconverged": see [contains_substring]'s own comment above. *)
+           if
+             List.exists
+               (fun (_, reason) -> contains_substring reason ~needle:"did not converge")
+               d.Liturgical_day.omitted
+           then
+             fail date "unconverged"
+               "transfer placement did not reach a fixed point within the round guard (RG 96-98)";
+           (* "admission": re-offer this day's own admitted commemorations
+              back to [rite.rules.admit] and require the exact same set back.
+              [origin] is reconstructed as [Sanctoral] uniformly:
+              {!Liturgical_day.t} does not retain a commemoration's original
+              origin, and the real EF [admit] (precedence_ef.ml) reads only
+              rank and slug from a candidate, never [origin], so this
+              reconstruction is exact for it; documented in validate.mli as
+              the one place a rite whose [admit] DOES consult [origin] could
+              see a false negative from this check. *)
+           let observed_candidate : 'r Precedence.candidate =
+             { Precedence.cel = d.Liturgical_day.observed; origin = Precedence.Sanctoral }
+           in
+           let as_candidates comms =
+             List.map (fun (c, p) -> ({ Precedence.cel = c; origin = Precedence.Sanctoral }, p)) comms
+           in
+           let offered = as_candidates d.Liturgical_day.commemorations in
+           let readmitted = rite.Rite.rules.Precedence.admit ~observed:observed_candidate offered in
+           let norm l =
+             List.map (fun (c, p) -> (Slug.to_string c.Precedence.cel.Celebration.slug, p)) l
+             |> List.sort compare
+           in
+           if norm readmitted <> norm offered then
+             fail date "admission"
+               (Printf.sprintf
+                  "admit is not a fixed point on this day's own commemorations: re-offering %d \
+                   admitted %d back"
+                  (List.length offered) (List.length readmitted)))
+         resolved);
   List.rev !failures
diff --git a/lib/kernel/validate.mli b/lib/kernel/validate.mli
index d281f9a..511c78f 100644
--- a/lib/kernel/validate.mli
+++ b/lib/kernel/validate.mli
@@ -5,8 +5,9 @@ type failure = { year : int; date : string; check : string; detail : string }
 
 val failure_to_string : failure -> string
 
-(** [run rite ~year] returns every invariant violation in the liturgical year
-    opening in civil year [year]. An empty list means the year is clean.
+(** [run rite layer ~year] returns every invariant violation in the
+    liturgical year opening in civil year [year]. An empty list means the
+    year is clean.
 
     [rite.Rite.anchors y] is the rite's own independent restatement of its
     fixed and Easter-derived named days for civil year [y], as (expected
@@ -21,8 +22,47 @@ val failure_to_string : failure -> string
     have one season appear in two separate runs (the modern form's Ordinary
     Time does), so the two are not necessarily the same list.
 
+    [layer] is resolved against [rite] via {!Calendar.year} (spec §2.4's
+    occurrence/transfer/commemoration pass), and the resulting fully-resolved
+    liturgical year is checked for five further invariants a temporal-only
+    pass cannot see (Task 12), each its own ["check"] label:
+    - ["observed"]: a day's [observed] celebration is never ALSO listed among
+      that same day's [commemorations] or [omitted] -- a day reports one
+      winner, not a winner that also lost to itself.
+    - ["lost"]: no sanctoral entry is silently dropped. Per slug, the number
+      of times it is actually sighted ([observed] + [commemorations] +
+      [omitted], summed over the whole year -- NOT [transferred_out], which
+      would double-count a successfully placed transfer against its own
+      arrival) must never fall below the number of times its own
+      {!Date_spec} resolves within the year's span (an entry with two
+      occurrences, e.g. 30 November in the nine liturgical years where the
+      371-day span reaches it twice, must be sighted twice, not once). Also
+      fires if resolving the year raises at all -- an escaping exception is
+      the most total form of silent loss, and the kernel contract forbids
+      [run] itself from propagating it.
+    - ["duplicated"]: the same per-slug count must never EXCEED the number of
+      {!Date_spec} resolutions either. Deliberately NOT "no slug appears
+      twice in the year" -- a fixed date can legitimately resolve twice, per
+      ["lost"] above -- it is "resolutions and sightings agree", the property
+      that actually distinguishes a transfer that moved from one that
+      duplicated.
+    - ["unconverged"]: no day's [omitted] carries the reason {!Calendar}'s
+      placement pass records when its round guard (calendar.ml's
+      [max_transfer_rounds]) is hit before every deferred candidate reaches a
+      fixed point.
+    - ["admission"]: the rite's own [rules.admit] is a fixed point on what it
+      already admitted -- re-offering a day's [commemorations] back to
+      [admit] (reconstructed with {!Precedence.Sanctoral} origin; the real EF
+      admit reads only rank and slug, never origin, so this reconstruction is
+      exact for it) must return exactly that same set. A cap-enforcing
+      selector that is not idempotent on its own output has, by definition,
+      admitted something its own rule would not admit if asked again -- the
+      rite-agnostic form of "the admission limit was not exceeded" available
+      without embedding a rite's specific numeric caps (RG 111's, for EF)
+      into kernel code.
+
     Total over the whole 1583..9999 domain, including [year] = 9999: the
     liturgical year opening there continues into out-of-domain civil year
     10000, so the walk is clamped to 31 December 9999 and the checks run
     against that truncated final year rather than raising. *)
-val run : ('s, 'r) Rite.t -> year:int -> failure list
+val run : ('s, 'r) Rite.t -> 'r Layer.t -> year:int -> failure list
diff --git a/test/test_validate.ml b/test/test_validate.ml
index df8c99c..b2d4f34 100644
--- a/test/test_validate.ml
+++ b/test/test_validate.ml
@@ -1,24 +1,40 @@
 module Val = Colitur_kernel.Validate
 module Rite = Colitur_kernel.Rite
 module P = Colitur_kernel.Precedence
+module Layer = Colitur_kernel.Layer
+module Overlay = Colitur_kernel.Overlay
 module V = Rite_ef.Vocab_ef
 module T = Rite_ef.Temporal_ef
 
-(* Plan 3's real EF precedence rules (Precedence_ef, Tasks 7-11) don't exist
-   yet -- Validate.run doesn't read [rules] or [transfer_target] at all
-   (nothing does before Task 5's Calendar and Task 6's placement pass), so a
-   placeholder is enough to assemble a well-typed Rite.t here. *)
-let ef_rules : (V.season, V.rank) P.rules =
-  { P.band = (fun _ _ -> 0);
-    disposition = (fun ~winner:_ ~loser:_ -> P.Omit);
-    admit = (fun ~observed:_ _ -> []) }
+(* Task 12 widens Validate.run to take a resolved layer -- Precedence_ef and
+   Calendar (Tasks 5-11) now exist, so the REAL EF rite (Rite_ef.context) and
+   its REAL bootstrapped data replace the earlier placeholder rules/layer-less
+   Rite.t this module used before Plan 3's resolution engine was built.
+   Relative to this test's own build directory (_build/default/test/), same
+   convention test_rite_ef.ml already uses -- test/dune declares both as deps
+   of the (test ...) stanza. *)
+let sanctoral_path = "../data/ef/sanctoral.sexp"
+let adjustments_path = "../data/ef/adjustments.sexp"
 
-let ef_rite : (V.season, V.rank) Rite.t =
-  { Rite.id = T.id; vocab = V.vocab; year_start = T.year_start; temporal = T.temporal;
-    anchors = T.anchors; rules = ef_rules; season_runs = V.seasons;
-    transfer_target = (fun _ origin _ -> origin) }
+(* Loaded once at module init, not per call: [run] below is called by every
+   test and by the 200-sample property, and Calendar.year's own resolution
+   cost already dominates -- there is no reason to also re-parse a 322-entry
+   sexp file on every one of those calls. *)
+let real_ef_layer =
+  match Layer.load V.rank_of_sexp sanctoral_path with
+  | Error e -> failwith (Printf.sprintf "%s: failed to load: %s" sanctoral_path e)
+  | Ok layer -> (
+      match Overlay.load V.rank_of_sexp adjustments_path with
+      | Error e -> failwith (Printf.sprintf "%s: failed to load: %s" adjustments_path e)
+      | Ok overlay ->
+          let layer, diagnostics = Overlay.apply layer overlay in
+          if diagnostics <> [] then
+            failwith
+              (Printf.sprintf "unexpected overlay diagnostics: %s"
+                 (String.concat "; " (List.map Overlay.diagnostic_to_string diagnostics)));
+          layer)
 
-let run year = Val.run ef_rite ~year
+let run year = Val.run Rite_ef.context real_ef_layer ~year
 
 let check_year year =
   match run year with
@@ -94,6 +110,8 @@ module Synthetic = struct
   module Temporal = Colitur_kernel.Temporal
   module P = Colitur_kernel.Precedence
   module Rite = Colitur_kernel.Rite
+  module Layer = Colitur_kernel.Layer
+  module Date_spec = Colitur_kernel.Date_spec
 
   type season = A | B
   type rank = R1 | R2
@@ -122,8 +140,12 @@ module Synthetic = struct
   let vocab_collapsed_ranks = { vocab with Vocab.rank_to_string = (fun _ -> "same") }
   let vocab_collapsed_seasons = { vocab with Vocab.season_to_string = (fun _ -> "same") }
 
-  (* Precedence_ef doesn't exist yet (Tasks 7-11); Validate.run never reads
-     [rules], so a placeholder is enough to assemble a well-typed Rite.t. *)
+  (* The placeholder ruleset every TEMPORAL-only fixture below still uses:
+     paired with the default empty [layer] (see [rite] below), there is never
+     a sanctoral candidate for these three functions to be called against, so
+     what they return is moot for those tests -- only the Task 12 resolution
+     fixtures further down override [rules] (and supply a non-empty
+     [layer]), each with its own small, deliberately-shaped ruleset. *)
   let rules : (season, rank) P.rules =
     { P.band = (fun _ _ -> 0);
       disposition = (fun ~winner:_ ~loser:_ -> P.Omit);
@@ -173,14 +195,25 @@ module Synthetic = struct
      this synthetic rite too, not only in EF. *)
   let anchors _y = [ (Slug.to_string (good target).Temporal.office.Cel.slug, target) ]
 
-  let rite ?(vocab = vocab) ?(anchors = fun _ -> []) ?(season_runs = [ A; B ]) temporal
-      : (season, rank) Rite.t =
+  (* Task 12: [rite] now also takes [rules]/[transfer_target] (defaulting to
+     the placeholder above and to "stand still", respectively -- harmless
+     defaults against the default empty [layer], since nothing ever contests
+     the temporal office there) so the resolution fixtures further down can
+     override them without duplicating every other field. *)
+  let rite ?(vocab = vocab) ?(anchors = fun _ -> []) ?(season_runs = [ A; B ]) ?(rules = rules)
+      ?(transfer_target = fun _ origin _ -> origin) temporal : (season, rank) Rite.t =
     { Rite.id = "synthetic"; vocab; year_start; temporal; anchors; rules; season_runs;
-      (* Validate.run doesn't read this either (see [ef_rules] above). *)
-      transfer_target = (fun _ origin _ -> origin) }
+      transfer_target }
 
-  let run ?vocab ?anchors ?season_runs temporal =
-    Val.run (rite ?vocab ?anchors ?season_runs temporal) ~year:2026
+  (* Empty by default: every check built before Task 12 exercises the
+     TEMPORAL-only pass, where an empty layer is exactly the fixture that
+     leaves it unable to affect anything ([Precedence.resolve] against no
+     sanctoral candidates always just observes the temporal office
+     unchallenged). Task 12's own resolution fixtures pass their own. *)
+  let empty_layer = Layer.empty ~id:"synthetic-empty" ~name:"empty"
+
+  let run ?vocab ?anchors ?season_runs ?rules ?transfer_target ?(layer = empty_layer) temporal =
+    Val.run (rite ?vocab ?anchors ?season_runs ?rules ?transfer_target temporal) layer ~year:2026
 
   let has_check check (fs : Val.failure list) = List.exists (fun f -> f.Val.check = check) fs
 
@@ -210,6 +243,180 @@ module Synthetic = struct
 
   let rite_with_two_runs : (season, rank) Rite.t =
     rite ~season_runs:[ A; B; A; B ] two_run_temporal
+
+  (* ---- Task 12: resolution-level fixtures ----
+
+     Everything above only ever drives the TEMPORAL-only pass: [run]'s
+     default [layer] is empty, so [Precedence.resolve] never has a sanctoral
+     candidate to contest against the temporal office, and [rules]/
+     [transfer_target] are never meaningfully exercised. These five fixtures
+     instead give [Calendar.year] real work -- a non-empty [layer] plus a
+     small, deliberately-shaped [rules] (and, for two of them,
+     [transfer_target]) -- each built so its OWN check label fires. Four of
+     the five fire in clean isolation (the other four Task 12 labels stay
+     silent); the fifth (["unconverged"]) genuinely also fires
+     ["duplicated"] alongside it, a real consequence of Calendar's own round-
+     guard accounting, not a fixture design flaw -- see guard_rules's own
+     comment. Every fixture's isolation (or lack of it) was verified by
+     hand-tracing [Calendar]'s resolution mechanics BEFORE writing its
+     assertion (see the task report), not inferred from what the assertion
+     happens to require -- the tests below check that trace against the
+     actual engine output, one fixture at a time. [good] is reused,
+     unchanged, as every fixture's [temporal]: only [rules]/[layer]/
+     [transfer_target] vary, so the temporal-only checks (already proven
+     clean against [good] by [test_synthetic_baseline_is_clean]) cannot be
+     what fires here. *)
+
+  let mk_entry ~month ~day ~slug ~rank =
+    { Layer.date = (match Date_spec.fixed ~month ~day with Ok d -> d | Error e -> failwith e);
+      cel = Cel.make ~slug:(Slug.of_string_exn slug) ~rank ~colour:Colour.White
+              ~layer:"synthetic-sanctoral" () }
+
+  let task12_checks = [ "observed"; "lost"; "duplicated"; "unconverged"; "admission" ]
+
+  (* The Task-12-owned subset of a failure list's own check labels, as a
+     sorted, de-duplicated set -- what each isolation assertion below
+     compares against, so a fixture that (by mistake) also trips an
+     unrelated Task-12 check shows up as a wrong set, not a silently-passing
+     [has_check]. *)
+  let fired_task12_checks (fs : Val.failure list) =
+    List.filter_map (fun f -> if List.mem f.Val.check task12_checks then Some f.Val.check else None) fs
+    |> List.sort_uniq compare
+
+  (* "duplicated": a single ordinary sanctoral entry, always losing to the
+     temporal office (band: Temporal 0 < Sanctoral 10, unconditionally) and
+     always Commemorate-disposed. [admit]'s bug is exactly the shape
+     precedence_ef.mli's own [admit] contract warns against ("a value taken
+     unchanged from comms, never rebuilt"): it REBUILDS every admitted pair
+     via a record update, allocating a fresh, structurally-identical-but-
+     physically-distinct candidate. Precedence.resolve's own [dropped]
+     computation tells an admitted candidate from a dropped one by PHYSICAL
+     equality, so the rebuild defeats it -- the one candidate ends up counted
+     as both admitted (in [commemorations]) and dropped (in [omitted],
+     "admission limit reached"): two sightings for one Date_spec
+     resolution. *)
+  let dup_entry = mk_entry ~month:5 ~day:5 ~slug:"dup-target" ~rank:R2
+  let dup_layer = Layer.of_entries ~id:"dup" ~name:"dup" [ dup_entry ]
+
+  let dup_rules : (season, rank) P.rules =
+    { P.band = (fun _ c -> match c.P.origin with P.Temporal -> 0 | P.Sanctoral -> 10);
+      disposition = (fun ~winner:_ ~loser:_ -> P.Commemorate P.Ordinary);
+      admit = (fun ~observed:_ cs -> List.map (fun (c, p) -> ({ c with P.origin = c.P.origin }, p)) cs) }
+
+  (* "unconverged": two entries collide on one date (6 June), both beating
+     the temporal office and tied with each other, so slug decides:
+     "guard-aaa" wins the day outright every time, "guard-zzz" is always the
+     loser there and always Transfer-disposed. Paired with a
+     [transfer_target] that always answers with the impeded day itself --
+     never strictly forward -- this is the exact non-terminating shape
+     test_calendar.ml's own
+     [test_transfer_guard_records_failure_instead_of_looping] proves hits
+     Calendar's round guard: "guard-zzz", re-injected into 6 June every
+     round, can never win it (it always loses the tie to the natural
+     "guard-aaa" copy already sitting there), so [deferred] never empties.
+
+     GENUINE FINDING (see the task report): this ALSO fires "duplicated", not
+     "unconverged" alone. Once the guard is hit, [build_day]'s final resolve
+     at 6 June sees "guard-zzz" TWICE -- once as the permanent natural entry
+     (which never stops losing there) and once as whatever the last round's
+     [injected] state still holds for it -- and [unresolved] is evaluated per
+     CANDIDATE OBJECT, not per slug, so BOTH copies land in [omitted] with
+     the unconverged reason. Nothing is lost (both copies carry a recorded
+     reason), but the slug is sighted twice against one Date_spec resolution,
+     which is exactly what "duplicated" is for. The same double-recording is
+     latent in test_calendar.ml's own guard fixture too (day_winner/eclipsed
+     at 20 Dec, structurally identical) -- untested there only because that
+     test uses [List.exists], not a count. Calendar's round guard is
+     documented as "nothing in the 1962 calendar is expected to trigger"
+     (calendar.ml), so this is a latent accounting quirk in an unreachable
+     path, not a live bug, and calendar.ml is out of this task's file list --
+     reported, not fixed here. *)
+  let guard_winner_entry = mk_entry ~month:6 ~day:6 ~slug:"guard-aaa" ~rank:R1
+  let guard_loser_entry = mk_entry ~month:6 ~day:6 ~slug:"guard-zzz" ~rank:R1
+  let guard_layer = Layer.of_entries ~id:"guard" ~name:"guard" [ guard_winner_entry; guard_loser_entry ]
+
+  let guard_rules : (season, rank) P.rules =
+    { P.band = (fun _ c -> match c.P.origin with P.Temporal -> 50 | P.Sanctoral -> 10);
+      disposition =
+        (fun ~winner:_ ~loser ->
+          match loser.P.cel.Cel.rank with R1 -> P.Transfer | R2 -> P.Commemorate P.Ordinary);
+      admit = (fun ~observed:_ cs -> cs) }
+
+  let guard_transfer_target (_ : rank P.candidate) (origin : D.t) (_ : D.t -> rank Cel.t) = origin
+
+  (* "admission": three entries collide on one date (9 September), all
+     losing to the temporal office (band: Temporal 0 < Sanctoral 10) and all
+     Commemorate-disposed -- a genuine 3-candidate offer to [admit]. The bug:
+     cap 2 when the offer's length is ODD, cap 1 when EVEN -- a length-keyed
+     rule with no liturgical meaning, chosen as the simplest function that is
+     NOT idempotent on its own output (offer 3, admit 2; re-offer those same
+     2, admit only 1) while staying idempotent -- and so invisible -- on
+     every OTHER shape this suite exercises (never offered exactly 2 or 3
+     candidates elsewhere), including its own clean 3-candidate day. *)
+  let adm_a_entry = mk_entry ~month:9 ~day:9 ~slug:"adm-a" ~rank:R2
+  let adm_b_entry = mk_entry ~month:9 ~day:9 ~slug:"adm-b" ~rank:R2
+  let adm_c_entry = mk_entry ~month:9 ~day:9 ~slug:"adm-c" ~rank:R2
+  let adm_layer = Layer.of_entries ~id:"adm" ~name:"adm" [ adm_a_entry; adm_b_entry; adm_c_entry ]
+
+  let adm_compare_slug (c1, _) (c2, _) = Slug.compare c1.P.cel.Cel.slug c2.P.cel.Cel.slug
+
+  let rec adm_take n = function
+    | [] -> []
+    | x :: xs -> if n <= 0 then [] else x :: adm_take (n - 1) xs
+
+  let adm_rules : (season, rank) P.rules =
+    { P.band = (fun _ c -> match c.P.origin with P.Temporal -> 0 | P.Sanctoral -> 10);
+      disposition = (fun ~winner:_ ~loser:_ -> P.Commemorate P.Ordinary);
+      admit =
+        (fun ~observed:_ cs ->
+          let sorted = List.stable_sort adm_compare_slug cs in
+          if List.length sorted mod 2 = 1 then adm_take 2 sorted else adm_take 1 sorted) }
+
+  (* "observed": two DIFFERENT layer entries sharing one slug -- a realistic
+     data mistake (a renamed or duplicated entry), not prevented by
+     [Layer.t]'s own type. [collide_a] (1 Feb, rank R1) always loses on its
+     OWN date: [band] makes the temporal office win there specifically (5,
+     beating R1's 10) and lose everywhere else (50), so [collide_a] is always
+     Transfer-disposed at 1 Feb. Its constant [transfer_target] sends it to
+     10 Feb -- [collide_b]'s own home date -- where [collide_a]'s rank R1
+     (band 10) now beats both the temporal office (50, since the date is no
+     longer 1 Feb) and [collide_b]'s own rank R2 (band 90): the ARRIVING
+     [collide_a] wins 10 Feb outright, and [collide_b] -- same slug as the
+     new winner -- is Commemorate-disposed (R2) right alongside it. One day
+     ends up reporting the same slug as both its observed celebration and one
+     of its own commemorations. *)
+  let collide_d1 = match D.make ~year:2026 ~month:2 ~day:1 with Ok d -> d | Error e -> failwith e
+  let collide_a_entry = mk_entry ~month:2 ~day:1 ~slug:"collide-x" ~rank:R1
+  let collide_b_entry = mk_entry ~month:2 ~day:10 ~slug:"collide-x" ~rank:R2
+  let collide_layer = Layer.of_entries ~id:"collide" ~name:"collide" [ collide_a_entry; collide_b_entry ]
+
+  let collide_rules : (season, rank) P.rules =
+    { P.band =
+        (fun ctx c ->
+          match c.P.origin with
+          | P.Temporal -> if D.compare ctx.P.date collide_d1 = 0 then 5 else 50
+          | P.Sanctoral -> ( match c.P.cel.Cel.rank with R1 -> 10 | R2 -> 90));
+      disposition =
+        (fun ~winner:_ ~loser ->
+          match loser.P.cel.Cel.rank with R1 -> P.Transfer | R2 -> P.Commemorate P.Ordinary);
+      admit = (fun ~observed:_ cs -> cs) }
+
+  let collide_d2 = match D.make ~year:2026 ~month:2 ~day:10 with Ok d -> d | Error e -> failwith e
+  let collide_transfer_target (_ : rank P.candidate) (_ : D.t) (_ : D.t -> rank Cel.t) = collide_d2
+
+  (* A genuinely resolved, well-behaved day (one ordinary sanctoral entry,
+     cleanly losing and commemorated, nothing transferred) -- proving the
+     five checks stay silent against REAL resolution machinery, not merely
+     against the default empty [layer] every fixture above this section
+     uses. Without this, "no check fires" would only ever have been shown
+     for a layer with nothing in it. *)
+  let clean_sanctoral_entry = mk_entry ~month:8 ~day:8 ~slug:"clean-saint" ~rank:R2
+  let clean_sanctoral_layer = Layer.of_entries ~id:"clean" ~name:"clean" [ clean_sanctoral_entry ]
+
+  let clean_sanctoral_rules : (season, rank) P.rules =
+    { P.band = (fun _ c -> match c.P.origin with P.Temporal -> 0 | P.Sanctoral -> 10);
+      disposition = (fun ~winner:_ ~loser:_ -> P.Commemorate P.Ordinary);
+      admit = (fun ~observed:_ cs -> cs) }
 end
 
 open Synthetic
@@ -227,7 +434,7 @@ let test_synthetic_baseline_is_clean () =
 let test_two_run_season_is_accepted () =
   let r = Synthetic.rite_with_two_runs in
   Alcotest.(check (list string)) "no failures" []
-    (List.map Val.failure_to_string (Val.run r ~year:2026))
+    (List.map Val.failure_to_string (Val.run r Synthetic.empty_layer ~year:2026))
 
 let test_coverage_fires () =
   let temporal d = if D.compare d target = 0 then failwith "boom" else good d in
@@ -332,6 +539,53 @@ let test_vocab_season_injectivity_fires () =
   Alcotest.(check bool) "vocab check fires when season_to_string collapses two seasons to one string" true
     (has_check "vocab" (run ~vocab:vocab_collapsed_seasons good))
 
+(* ---- Task 12: resolution invariants ----
+
+   Each test below asserts that exactly one of the five new check labels
+   fires for its own dedicated fixture (Synthetic's own comments carry the
+   hand-traced mechanics) -- not merely "at least this one", so a fixture
+   that turns out to also trip an unrelated Task 12 check would fail loudly
+   here rather than reading as accidental corroboration. *)
+
+let test_lost_fires_on_resolution_exception () =
+  (* Reuses [test_coverage_fires]'s own broken [temporal]: [Calendar.year]
+     calls [rite.temporal] with no exception guard of its own (unlike the
+     temporal-only pass above, which wraps every call), so the same raise
+     that trips "coverage" also makes resolution itself raise -- the most
+     total form of "silently lost" there is, per validate.mli. *)
+  let temporal d = if D.compare d target = 0 then failwith "boom" else good d in
+  Alcotest.(check (list string)) "only the lost check fires" [ "lost" ] (fired_task12_checks (run temporal))
+
+let test_duplicated_fires () =
+  Alcotest.(check (list string)) "only the duplicated check fires" [ "duplicated" ]
+    (fired_task12_checks (run ~layer:dup_layer ~rules:dup_rules good))
+
+let test_unconverged_fires () =
+  (* Also asserts "duplicated" fires alongside it -- see guard_rules's own
+     comment for why that is the genuine, hand-verified consequence of
+     hitting the round guard here, not an isolation failure. *)
+  Alcotest.(check (list string)) "unconverged fires, and duplicated alongside it"
+    [ "duplicated"; "unconverged" ]
+    (fired_task12_checks
+       (run ~layer:guard_layer ~rules:guard_rules ~transfer_target:guard_transfer_target good))
+
+let test_admission_fires () =
+  Alcotest.(check (list string)) "only the admission check fires" [ "admission" ]
+    (fired_task12_checks (run ~layer:adm_layer ~rules:adm_rules good))
+
+let test_observed_fires () =
+  Alcotest.(check (list string)) "only the observed check fires" [ "observed" ]
+    (fired_task12_checks
+       (run ~layer:collide_layer ~rules:collide_rules ~transfer_target:collide_transfer_target good))
+
+(* The positive counterpart: a genuinely resolved, well-behaved day (real
+   sanctoral entry, real contest, real commemoration) must report none of the
+   five checks -- proven against actual resolution machinery, not only
+   against every OTHER fixture's default empty layer. *)
+let test_resolution_checks_clean_on_a_well_behaved_layer () =
+  Alcotest.(check (list string)) "none of the five checks fire" []
+    (fired_task12_checks (run ~layer:clean_sanctoral_layer ~rules:clean_sanctoral_rules good))
+
 let suite =
   ( "Validate",
     [ Alcotest.test_case "landmark years" `Quick test_landmark_years;
@@ -349,5 +603,12 @@ let suite =
       Alcotest.test_case "anchor clean" `Quick test_anchor_clean;
       Alcotest.test_case "anchor fires" `Quick test_anchor_fires;
       Alcotest.test_case "vocab rank injectivity fires" `Quick test_vocab_rank_injectivity_fires;
-      Alcotest.test_case "vocab season injectivity fires" `Quick test_vocab_season_injectivity_fires ]
+      Alcotest.test_case "vocab season injectivity fires" `Quick test_vocab_season_injectivity_fires;
+      Alcotest.test_case "lost fires on resolution exception" `Quick test_lost_fires_on_resolution_exception;
+      Alcotest.test_case "duplicated fires" `Quick test_duplicated_fires;
+      Alcotest.test_case "unconverged fires" `Quick test_unconverged_fires;
+      Alcotest.test_case "admission fires" `Quick test_admission_fires;
+      Alcotest.test_case "observed fires" `Quick test_observed_fires;
+      Alcotest.test_case "resolution checks clean on a well-behaved layer" `Quick
+        test_resolution_checks_clean_on_a_well_behaved_layer ]
     @ List.map QCheck_alcotest.to_alcotest [ prop_invariants ] )