Merge commit 'cea0ff8d' into ms-zset

context/adr/007-stable-identities-amendment-1.md

@@ -178,10 +178,11 @@ different thing that generates the same slug: the merged file declares that id t
 and the load is refused naming both. Stable identity across copies of a file is not
 promised (improvise-8tk5).
 
-**Built code.** `crates/improvise-core/src/model/id.rs` implements the accepted steps
-(`context/code/core.md` §20). A follow-up must replace rather than strip, collapse
-`_`, trim a trailing `_` and both ends' `-`, prepend `n`, make `claim` refuse what a
-generated id could not be, and add the virtual views and `IdKind::Group`.
+**Built code.** `crates/improvise-core/src/model/id.rs` implements this clause
+(`context/code/core.md` §20): `slugify` follows the six steps, `is_id_syntax` is the
+syntax, `claim` refuses what a generated id could not be, `VIRTUAL_IDS` holds the five
+virtual ids, `IdKind::Group` exists, and `natural_cmp` and `display_suffixes` implement
+natural order and clause 2's suffixes. No other code calls them yet.
 
 ### 5. Persistence
 
@@ -310,7 +311,7 @@ therefore shows B as `east-1`, never as a bare `east`.
 - Scripts that name things by display break and must be rewritten over ids.
 - Two measures can share a display, and are shown as `Profit` and `Profit #2`.
 - Old files' `_Measure` declarations and hyphen- or digit-led names change on first save.
-- `id.rs` and its tests need the follow-up in clause 4.
+- `id.rs` implements clause 4; the code that sorts, shows and creates ids does not call it yet.
 
 ## Open questions
 

context/code/core.md

@@ -1688,48 +1688,63 @@ probability (`> ||[||]` is a self-parent), so `generated_file_parses` accepts a
 
 ## 20. How an id is made — `model/id.rs` (ADR 007 clause 4, improvise-cq1q.2)
 
-`slugify` and `IdAllocator` are the first piece of ADR 007. They are pure
-functions of the display and the allocator's own history. Nothing calls them
-yet: the creation sites move onto them in the re-key step (improvise-cq1q.4).
+`slugify`, `IdAllocator`, `natural_cmp` and `display_suffixes` are the first
+piece of ADR 007. They are pure functions of their arguments and the
+allocator's own history. Nothing calls them yet: the creation sites move onto them in the re-key step (improvise-cq1q.4).
 Each rule traces to ADR 007's clause 4 (slugify, the counter, hand-written
-ids) or clause 1 (reserved ids).
+ids, natural order), clause 1 (reserved ids) or clause 2 (display suffixes),
+as amended by amendment 1.
 
 **Case folding is full Unicode folding, and it comes from `unicase`.**
-`str::to_lowercase` is not folding: `ß` lowercases to itself and is then
-stripped, so `Straße` would slug to `strae` (clause 4, step 1: full case folding). The same goes for `ſ`
-(long s) and the `fi` ligature. `unicase` 2.9 is `no_std` and has no
+`str::to_lowercase` is not folding: `ß` lowercases to itself and then
+becomes `_`, so `Straße` would slug to `stra_e` (clause 4, step 1: full case
+folding). The same goes for `ſ` (long s) and the `fi` ligature. `unicase` 2.9 is `no_std` and has no
 dependencies, so it passes the wasm gate. Its `to_folded_case` applies the
 C+F mappings of Unicode's CaseFolding.txt, and its own tests pin `Maße` →
-`masse`. Most of what folding produces is stripped anyway: only an ASCII
-letter survives step 3. Deriving that ASCII-producing subset of the table by
-hand was rejected. It is a second copy of the Unicode data, and nothing would
+`masse`. Most of what folding produces becomes `_` anyway: only ASCII
+letters, digits and `-` survive step 2. Deriving that ASCII-producing subset of
+the table by hand was rejected. It is a second copy of the Unicode data, and nothing would
 say when it drifted.
 
-**A "space" is U+0020.** The accepted clause 4 says "replace each run of spaces
-with one `_`". A tab or a no-break space is not a space here, so it is
-stripped by step 3. Only a run of U+0020 becomes one `_`. An underscore the
-display already had is never merged with the one a space run makes. So `a_ b`
-slugs to `a__b`: the steps are applied as written, and no extra
-underscore-collapsing step exists. A trailing run survives, so `East ` slugs
-to `east_`. Only *leading* underscores are removed (step 4).
+**Slugify is the amendment's six steps** (ADR 007 amendment 1, clause 4):
+casefold; every character outside `a`–`z`, `0`–`9` and `-` becomes `_`; runs of
+`_` collapse; leading and trailing `_` and `-` are removed, all of them (the
+trim is `trim_matches` over both characters, so `_-_East-_-` is `east`);
+`n` is prepended to a slug that starts with a digit; nothing left is the
+caller's `<kind>-<n>`. The order matters in one place: the trim runs before
+the `n`, so `-_7up` is `n7up` and a leading `-` can never be hidden behind the
+prefix. Whitespace of every kind, punctuation and every non-ASCII letter
+become `_`, so `Region(code)` is `region_code` and `Crème Brûlée` is
+`cr_me_br_l_e`. Folding is `unicase`'s, which maps `ß` to `ss`; a character
+that folds to a combining mark (`İ` folds to `i` plus U+0307) leaves the `i`
+and turns the mark into `_`, which the trim then removes. A hyphen between
+underscores survives (`a - b` is `a_-_b`).
 
-**ADR 007's amendment changes these rules, and this code predates it.** The
-amendment (`context/adr/007-stable-identities-amendment-1.md`, accepted 2026-10-09)
-says in its clause 4:
-- every character outside `a`–`z`, `0`–`9` and `-` becomes `_` instead of being
-  stripped (not only U+0020), so `Region(code)` slugs to `region_code`, while
-  `Q1-2024` keeps its `-`;
-- runs of `_` collapse, so `a_ b` and `a__b` both slug to `a_b`;
-- leading and trailing `_` and `-` are removed, so `East ` → `east`, `-East-` →
-  `east`, and `-` alone takes `<kind>-<n>`;
-- `n` is prepended to a slug that starts with a digit, so `2024` → `n2024`;
-- a hand-written id must obey every syntax rule of a generated one.
+**The id syntax has one validator, `is_id_syntax`**: a lower-case ASCII
+letter, then `a`–`z`, `0`–`9`, `-` and single underscores, never ending in
+`_` or `-`. Slugify's non-empty output always satisfies it and is a fixed point
+of itself, and a `-<n>` suffix keeps the shape, so a generated id always
+validates (properties in `model::id::tests`). A virtual id fails it by design,
+because the leading `_` is the reservation.
 
-This section, `slugify`, and the tests
-`slugify_collapses_a_run_of_spaces_to_one_underscore` (its `east_` case) and
-`slugify_keeps_an_underscore_the_display_already_had` describe the earlier rule
-above. They change in a follow-up the amendment calls for. The amendment's
-clause 4 lists every difference.
+**Natural order is `natural_cmp`** (clause 4, "Ids are always sorted in
+natural order"). An id is split into alternating digit and non-digit runs, and
+the runs are compared pairwise: non-digit runs by bytes; digit runs by value
+(strip leading zeros, shorter is smaller, then bytes), and a tie on value goes
+to the run with fewer leading zeros, immediately and not after the later runs.
+The id that runs out of runs first sorts first. No digit run is parsed into an
+integer, so a run of any length compares correctly. Where two ids disagree
+about the kind of run at a position (only possible for text that is not an
+id), the runs compare as bytes. It is a total order and equal only for equal
+strings. **Nothing calls it yet**: `CellKey`, `DataStore`, the writer and the GP
+dataset still sort with `String::cmp` until the re-key step.
+
+**Equal displays are suffixed by `display_suffixes`** (clause 2). Given
+`(id, display)` pairs it returns what each is shown as, in input order: the
+first of a group of equal displays in natural id order keeps the bare display,
+the rest get ` #2`, ` #3`, …, and a number is skipped when a literal display
+already reads `<display> #<n>` anywhere in the scope. Displays are equal
+byte for byte, not case-folded. It is pure and nothing renders through it yet.
 
 **The allocator records every id it admits and releases none.** That is the
 whole of retirement (clause 4, "within a session a removed id is never handed
@@ -1750,17 +1765,14 @@ name happens to be free, because clause 4 spells the result
 `<kind>-<n>`.
 
 **`claim` is the only door for a hand-written id.** It checks, in this order:
-the alphabet (non-empty, `a`–`z`, `0`–`9`, `-`, `_`), the reserved leading
-`_` (only `_index`, `_dim` and `_measure` may carry one, per clause 1, and
-the match is exact: `_indexer` and `_measure-1` are Reserved, since "no other
-id may start with `_`"), and
-duplicates. It accepts `-`, `-x`, `x-`, `a__b` and `2024`, all of which the
-amendment refuses (a hand-written id obeys the syntax of a generated one). It never renames.
-Refusing is the loader's job, and the loader
+the reserved leading `_` (only `_index`, `_dim`, `_measure`, `_records` and
+`_drill` may carry one, and the match is exact: `_indexer` and `_measure-1`
+are Reserved), the syntax (`is_id_syntax`; `-x`, `x-`, `2024`, `a__b` and `x_`
+are Malformed, `east-1`, `item-4`, `a-7` and `q1_-_2024` pass), and
+duplicates. A virtual id skips the syntax check, since it fails it by design.
+It never renames. Refusing is the loader's job, and the loader
 must name both lines of a duplicate; `ClaimError` carries only the id, so the
-loader keeps the line numbers. The virtual views `_records` and `_drill` are
-not yet in `VIRTUAL_IDS`. improvise-p003 item 1 asks for them, and they arrive
-with the ADR text fix (improvise-cq1q.1) rather than ahead of it.
+loader keeps the line numbers. `IdKind::Group` spells `group-<n>`.
 
 ## 21. A display beside the key (ADR 007 clause 2, improvise-cq1q.3)
 
@@ -1812,11 +1824,33 @@ beside the key and never in its place:
 - The browser's render model keeps its field names and carries the display in them
   (`RenderPageAxis.cat`, `RenderCatRow.label`), so `web/` is unchanged.
 
-Still keys: `GridLayout::row_label`/`col_label` (commands and the status line
-match on them), `edit_text`, the active-view marker, and everything status
-messages and the view title say (improvise-cq1q.13). A display change alone does
-not move `layout_fingerprint`, so it resets no cursor; no production path changes
-one yet.
+Still keys: `GridLayout::row_label`/`col_label` (commands match on them),
+`edit_text` and the active-view marker. A display change alone does not move
+`layout_fingerprint`, so it resets no cursor; no production path changes one yet.
+
+**What the third slice covers (improvise-cq1q.13):** the view title and every
+message that names a thing which exists. The title is the active view's display:
+the TUI reads `app.view().display()`, the browser `ViewListCache::display_of`
+(key when the list lacks the view). The statuses are the axis change (panel and
+tile bar), `Filter:`, `Deleted category/item`, the non-item
+refusal, and the item-add prompt. Both ends say them through the same
+`viewmodel` builders, so a wording is not spelled twice. The host reads
+`Model::category_display`/`item_display`; the client reads
+`CategoryTreeCache::category_display`/`item_display`. Each falls back to the key.
+
+**A message that names something which does not exist says what was typed.**
+`Unknown category 'x'`, `No view named "x"`, `View 'x' not found` and the
+`workbook.rs` errors are lookup misses: there is no display to find, and the typed
+text is what the person needs to correct. `Added category "x"` is optimistic and
+names what was just typed, whose display equals its key at creation. A stray
+coordinate in `non_item_refusal` is a key for the same reason; only the category
+beside it is a display. **A display must never reach a lookup**: the item-add
+mode keeps the category key (`AppMode::item_add_shown(key, shown)`) and the prompt
+alone carries the display. A formula-result refusal still says the target's key
+(improvise-cq1q.13 deferred it). A target in `_Measure` is implied by its formula
+and is no item, so it has no display to read. One in a regular category is a real
+item, but `CellId::Derived` carries only the target, so neither end can find its
+category. Both need that surrogate to carry the category first.
 
 `AxisFrame::cat_displays` is projected and validated, but nothing paints it yet
 (the corner label has no consumer); that is a gap to close when one does, not a

context/test-evidence/core.md

@@ -1914,30 +1914,108 @@ identity on the view.
 header stays for the sibling quarter that has data. Rival: `prune_axis_items`
 keying open runs by level alone. This test and the `NESTED` enumeration fail.
 
-## `model/id.rs` (ADR 007 clause 4, improvise-cq1q.2)
+## `model/id.rs` (ADR 007 clause 4 and amendment 1, improvise-cq1q.2, improvise-cq1q.14)
 
-These tests were written before `slugify` and `IdAllocator` had bodies. With
-`todo!()` bodies all eleven failed. Each rival below was then injected into the
-finished module, run against `cargo test -p improvise-core --lib model::id`, and
+Each rival below was injected into the finished module, run against `cargo test -p improvise-core --lib model::id`, and
 reverted. The reasoning is `context/code/core.md` §20.
 
 ### model::id::tests::slugify_case_folds_rather_than_lowercases
 
 Rival: `display.to_lowercase()` in place of `unicase`'s full folding. Only
-this test fails: `left: "strae"`, `right: "strasse"`. `ß` lowercases to itself
-and step 3 strips it. `slugify_follows_the_adrs_examples` cannot see this rival,
+this test fails: `ß` lowercases to itself and becomes `_`, so `stra_e` against
+`strasse`. `slugify_follows_the_amendments_table` cannot see this rival,
 because each of its displays lowercases and folds alike.
 
-### model::id::tests::slugify_collapses_a_run_of_spaces_to_one_underscore
+### model::id::tests::slugify_follows_the_amendments_table
 
-Rival: every space becomes `_`, with runs not collapsed. Only this test fails:
-`"time___period"`. No other fixture has two spaces in a row.
+Every row of the amendment's clause 4 table, plus `-`, `%` and the empty
+display. Rivals, each of which fails this test: trimming only leading `_`
+(`East_` stays), trimming `_` and not `-` (`-East-`), not collapsing runs of
+`_` (`a__b`), not prepending `n` (`2024`), and stripping instead of replacing
+(`Region(code)` is `regioncode`). The last also fails
+`slugify_keeps_a_hyphen_between_underscores` and
+`a_slug_taken_by_another_kind_takes_a_suffix`.
 
-### model::id::tests::slugify_keeps_an_underscore_the_display_already_had
+### model::id::tests::slugify_trims_hyphens_and_underscores_until_neither_is_at_an_end
 
-Rival: `.replace("__", "_")` after the space step, which reads the accepted
-clause 4 as "no doubled underscores". Only this test fails: `left: "a_b"`. The rule
-collapses runs of *spaces*. An underscore that was in the display is kept.
+Rival: trim leading `_` only, or `_` only at both ends. `_-_East-_-` keeps a
+hyphen, and `-_-` is not empty. A single `trim_matches` over both characters
+passes; two sequential single-character trims would not.
+
+### model::id::tests::slugify_trims_before_it_prepends_the_n
+
+Rival: no `n` prefix, which fails this test, the table and the property below.
+`-_7up` is `n7up` only if the trim runs first; prepending first would leave the
+`-_` in front of the `n`.
+
+### model::id::tests::slugify_output_has_the_id_syntax_and_is_a_fixed_point
+
+The property over arbitrary displays: a non-empty slug satisfies
+`is_id_syntax` and slugifying it returns it. Rivals that fail it (and
+`generated_ids_are_distinct_well_formed_and_never_reserved`): no `_`
+collapse, no `n` prefix, keeping a trailing `_` or `-`.
+
+### model::id::tests::id_syntax_agrees_with_an_independent_checker
+
+`is_id_syntax` against a hand-written scanner of `^[a-z](_?[a-z0-9-])*$` that
+does not end in `-`, over `[a-cA-C0-9 _%é-]{0,8}`, so uppercase, space, symbols
+and non-ASCII are reached. Dropping the alphabet check also fails it. Rivals:
+allowing `__`, allowing a leading digit and allowing a trailing `-` each fail
+here and in `claim_refuses_what_a_generated_id_could_not_be`.
+
+### model::id::tests::natural_order_decides_the_zeros_tie_at_its_own_run_not_after_the_rest
+
+Rival: compare leading zeros only after every run compares equal in value.
+`a-7c` then sorts after `a-007b`, and this test fails alone.
+
+### model::id::tests::suffixed_displays_are_distinct_when_literals_already_hold_suffixes
+
+Displays are drawn from `A`, `A #2`, `A #3` and `B`, so literal suffixes meet
+generated ones. Rival: numbering without the skip fails it.
+
+### model::id::tests::claim_refuses_what_a_generated_id_could_not_be
+
+Rival: `claim` keeps the old alphabet-only check. `-x`, `x-`, `2024`, `a__b`,
+`x_` and `-` are admitted, and the test fails. It also pins the accepted ids
+`east-1`, `item-4`, `a-7` and `q1_-_2024`.
+
+### model::id::tests::claim_admits_each_virtual_id_once
+
+Rival: `VIRTUAL_IDS` without `_records` and `_drill`. The test spells the five
+ids out instead of iterating the constant, because an iteration over the
+constant passes with the constant shortened (the first version did).
+
+### model::id::tests::natural_order_puts_a_counter_suffix_in_numeric_order
+
+Rivals: comparing digit runs as strings (`profit-10` before `profit-2`) fails
+this test, `natural_order_compares_digit_runs_of_any_length_by_value` and
+`a_suffix_numbers_equal_displays_in_natural_id_order`; plain `str::cmp` fails
+those and `natural_order_ties_on_value_go_to_fewer_leading_zeros`.
+
+### model::id::tests::natural_order_ties_on_value_go_to_fewer_leading_zeros
+
+Rivals: more zeros first, or no tie-break (`a-7` equal to `a-007`). Both fail this test and the any-length test (`x000` after `x0`).
+
+### model::id::tests::natural_order_puts_the_id_that_runs_out_of_runs_first
+
+Rival: the longer id first. Only this test fails.
+
+### model::id::tests::natural_order_is_a_total_order
+
+Antisymmetry, equality only for equal strings and transitivity over
+`[a-c0-3_-]{0,7}`, which includes ids starting with a digit.
+
+### model::id::tests::a_suffix_numbers_equal_displays_in_natural_id_order
+
+Rival: ordering the group by `str::cmp` on the ids. `profit-10` is numbered
+before `profit-2` and this test fails alone.
+
+### model::id::tests::a_suffix_skips_a_number_a_literal_display_already_holds
+
+Rival: numbering without the skip. A literal `Profit #2` and a generated
+`Profit #2` are then both shown, and this test fails alone. A rival that starts
+numbering at ` #1` also fails it and
+`a_suffix_is_gapless_when_a_thing_goes_away`.
 
 ### model::id::tests::the_suffix_is_the_next_counter_value_not_the_lowest_free_number
 
@@ -2144,3 +2222,81 @@ The display "Eastern Seaboard" against the key "E" gives 17, not the 4 minimum.
 Rival: `col_groups` labels a run with `g.name`. The browser test for group displays
 covered row groups only; this one folds a column frame whose group "Q1" is shown as
 "First quarter" and fails on the key.
+
+### draw::content_tests::the_grid_title_names_the_views_display_not_its_key
+
+improvise-cq1q.13, TUI half. The view is displayed "Quarterly overview of regional
+sales" under the key "Default", and the whole frame is drawn through `draw`. Rival:
+`draw_content` passes `app.view_state.active_view` to the widget; the title reads
+`View: Default` and this test fails on both assertions.
+
+### render::tests::the_title_names_the_active_views_display_not_its_key
+
+The browser half. Rival: `render_model` takes `view_name` from
+`state.view.active_view`; the test fails. The second half is the control: a view
+the list does not hold falls back to its key rather than to an empty title.
+
+### resolve::display_tests::a_panel_status_names_what_a_person_sees_not_the_keys
+
+The browser resolver's panel statuses: axis cycle, filter, delete category, delete
+item. Displays are 36 to 38 characters against keys of 4 to 6. Rivals, each run:
+the cycle status passes the key; the filter composes `SetPageSelection` with the
+item's display; the item removal names the display. Each fails here, the last two
+on the `Region/North` and `RemoveItem` assertions that pin the lookup to keys.
+
+### resolve::display_tests::a_tile_status_names_the_display
+
+Rival: the tile route passes `tile.category`; fails on the key.
+
+### resolve::display_tests::the_item_prompt_names_the_display_and_the_mode_keeps_the_key
+
+Rival: the mode is built with the display as its category
+(`item_add_shown(shown, ..)`); the prompt reads right and the commit would add to
+a category that does not exist. The test fails on `category == "Region"`.
+
+### resolve::display_tests::a_refused_cell_names_the_category_it_shows
+
+Rival: the non-item refusal gets the category key. The stray coordinate stays a key
+because it names no item and has no display.
+
+### command::cmd::panel::tests::a_panel_status_names_what_a_person_sees_not_the_keys
+
+The host half of the panel statuses and the item-add prompt. Rivals, each run: the
+axis status passes `cat_name` (fails); the filter status passes the item key
+(fails); the item-add mode is built from the display (fails on the
+`category: "Type"` assertion).
+
+Review follow-up: the same test now also pins the operands. Rivals: the host
+`RemoveCategory` and `SetPageSelection` given the display fail on the
+`RemoveCategory("Type")` and `item: "Food"` assertions. The client twin fails the
+same way on `RemoveCategory`.
+
+### command::cmd::tile::tests::a_tile_status_names_the_display_not_the_key
+
+Rival: the status formats `name`. It fails on both the present display and the
+absent key.
+
+### ui::app::non_item_key_tests::a_non_item_refusal_names_the_categorys_display
+
+Rival, run once per site: the refusal in `EditOrDrill` (the `i` key) and the one in
+`CmdContext::value_cell_key` (the `p` key) each pass the key. Each fails here.
+
+### ui::app::non_item_key_tests::a_commit_on_a_non_item_cell_names_the_categorys_display
+
+The third site, `uneditable` in `cmd/core.rs`, which only a commit reaches once an
+editor is open (`:enter-mode editing`). Rival: it passes the key; the two tests
+above stay green and this one fails.
+
+### ui::app::non_item_key_tests::a_refused_wire_write_names_the_category_it_shows
+
+The wire's own refusal in `Grids::unwritable`. Rival: the category key; fails. The
+formula arm (once a third copy of the derived wording, now `derived_refusal`) is
+pinned to its wording so the consolidation cannot change what it says.
+
+### resolve::display_tests::the_declines_an_advance_and_a_commit_reach_name_the_category_it_shows
+
+From the Opus review of #339: the browser's `declined_at` non-item arm could pass the
+key with the whole suite green. It is reached by `reopened_at` (an advance),
+`refused_here` (a commit) and `settle_declined_editor`. Rival: the arm passes
+`category`; the test fails on all three assertions, and the display is 36 characters
+against the key "Region".

crates/improvise-command/src/command/cmd/core.rs

@@ -39,7 +39,9 @@ pub fn uneditable(model: &Model, layout: &GridLayout, row: usize, col: usize) ->
             .to_string(),
         ),
         Some(CellId::Derived { target }) => Some(derived_refusal(&target)),
-        Some(CellId::NonItem { category, item }) => Some(non_item_refusal(&category, &item)),
+        Some(CellId::NonItem { category, item }) => {
+            Some(non_item_refusal(model.category_display(&category), &item))
+        }
         Some(CellId::Record(_) | CellId::Create(_) | CellId::Coordinate { .. }) | None => None,
     }
 }
@@ -133,7 +135,10 @@ impl<'a> CmdContext<'a> {
             Some(CellId::Create(_) | CellId::Coordinate { .. }) => {
                 Err(NO_VALUE_REFUSAL.to_string())
             }
-            Some(CellId::NonItem { category, item }) => Err(non_item_refusal(&category, &item)),
+            Some(CellId::NonItem { category, item }) => Err(non_item_refusal(
+                self.model.category_display(&category),
+                &item,
+            )),
             None => Err(match self.cell_key() {
                 Some(_) => NO_VALUE_REFUSAL,
                 None => NO_CELL,

crates/improvise-command/src/command/cmd/mode.rs

@@ -393,7 +393,8 @@ impl Cmd for EditOrDrill {
         // refused later, under a minibuffer that hides why (improvise-yc9r).
         if let Some(improvise_protocol::CellId::NonItem { category, item }) = ctx.cursor_cell_id() {
             return vec![effect::refuse(improvise_protocol::non_item_refusal(
-                &category, &item,
+                ctx.model.category_display(&category),
+                &item,
             ))];
         }
         vec![

crates/improvise-command/src/command/cmd/panel.rs

@@ -1,4 +1,6 @@
-use improvise_protocol::viewmodel::axis_change_status;
+use improvise_protocol::viewmodel::{
+    axis_change_status, deleted_category_status, deleted_item_status, filter_status,
+};
 
 use crate::ui::app::AppMode;
 use crate::ui::effect::{self, Effect, Panel, ViewTarget};
@@ -186,6 +188,57 @@ mod tests {
         );
     }
 
+    /// improvise-cq1q.13: evidence in `context/test-evidence/core.md`.
+    #[test]
+    fn a_panel_status_names_what_a_person_sees_not_the_keys() {
+        const TYPE: &str = "Kind of food and drink";
+        const FOOD: &str = "Foodstuffs of every sort";
+        let mut wb = two_cat_model();
+        let ty = wb.model.category_mut("Type").unwrap();
+        ty.set_display(TYPE);
+        ty.set_item_display("Food", FOOD);
+        let layout = make_layout(&wb);
+        let reg = make_registry();
+        let mut ctx = make_ctx(&wb, &layout, &reg);
+        let expanded = std::collections::HashSet::from(["Type".to_string()]);
+        ctx.expanded_cats = &expanded;
+        let said = |effects: &[Box<dyn Effect>]| format!("{:?}", effects.last().unwrap());
+
+        ctx.cat_panel_cursor = 3;
+        assert_eq!(ctx.cat_at_cursor().as_deref(), Some("Type"), "setup");
+        assert!(said(&CycleAxisAtCursor.execute(&ctx)).contains(&format!("{TYPE} → ")));
+        assert!(said(&DeleteCategoryAtCursor.execute(&ctx)).contains(&format!("'{TYPE}'")));
+        let removal = format!("{:?}", DeleteCategoryAtCursor.execute(&ctx));
+        assert!(removal.contains("RemoveCategory(\"Type\")"), "{removal}");
+        let prompt = format!("{:?}", OpenItemAddAtCursor.execute(&ctx));
+        assert!(
+            prompt.contains(&format!("add item to {TYPE}: ")),
+            "{prompt}"
+        );
+        assert!(
+            prompt.contains("category: \"Type\""),
+            "the key stays: {prompt}"
+        );
+
+        ctx.cat_panel_cursor = 4;
+        let filtering = format!("{:?}", FilterToItem.execute(&ctx));
+        assert!(filtering.contains("item: \"Food\""), "keys: {filtering}");
+        let filter = said(&FilterToItem.execute(&ctx));
+        assert!(
+            filter.contains(&format!("Filter: {TYPE} = {FOOD}")),
+            "{filter}"
+        );
+        let delete = format!("{:?}", DeleteCategoryAtCursor.execute(&ctx));
+        assert!(
+            delete.contains(&format!("Deleted item '{FOOD}' from '{TYPE}'")),
+            "{delete}"
+        );
+        assert!(
+            delete.contains("item: \"Food\""),
+            "the effect still names the key: {delete}"
+        );
+    }
+
     #[test]
     fn cycle_panel_focus_with_no_panels_open() {
         let m = two_cat_model();
@@ -718,8 +771,12 @@ impl Cmd for CycleAxisAtCursor {
                 ViewTarget::Active,
                 cat_name.clone(),
             ))];
-            effects
-                .extend(cycled.map(|axis| effect::set_status(axis_change_status(&cat_name, axis))));
+            effects.extend(cycled.map(|axis| {
+                effect::set_status(axis_change_status(
+                    ctx.model.category_display(&cat_name),
+                    axis,
+                ))
+            }));
             effects
         } else {
             vec![effect::refuse(
@@ -738,7 +795,10 @@ impl Cmd for OpenItemAddAtCursor {
     }
     fn execute(&self, ctx: &CmdContext) -> Vec<Box<dyn Effect>> {
         if let Some(cat_name) = ctx.cat_at_cursor() {
-            vec![effect::change_mode(AppMode::item_add(cat_name))]
+            let shown = ctx.model.category_display(&cat_name).to_string();
+            vec![effect::change_mode(AppMode::item_add_shown(
+                cat_name, &shown,
+            ))]
         } else {
             vec![effect::refuse(
                 "No category selected. Press n to add a category first.",
@@ -790,7 +850,10 @@ impl Cmd for FilterToItem {
                         category: cat_name.clone(),
                         item: item_name.clone(),
                     }),
-                    effect::set_status(format!("Filter: {cat_name} = {item_name}")),
+                    effect::set_status(filter_status(
+                        ctx.model.category_display(&cat_name),
+                        ctx.model.item_display(&cat_name, &item_name),
+                    )),
                 ]
             }
             Some(CatTreeEntry::Category { .. }) => {
@@ -816,7 +879,7 @@ impl Cmd for DeleteCategoryAtCursor {
             Some(CatTreeEntry::Category { name, .. }) => {
                 vec![
                     Box::new(effect::RemoveCategory(name.clone())),
-                    effect::set_status(format!("Deleted category '{name}'")),
+                    effect::set_status(deleted_category_status(ctx.model.category_display(&name))),
                 ]
             }
             Some(CatTreeEntry::Item {
@@ -829,7 +892,10 @@ impl Cmd for DeleteCategoryAtCursor {
                         category: cat_name.clone(),
                         item: item_name.clone(),
                     }),
-                    effect::set_status(format!("Deleted item '{item_name}' from '{cat_name}'")),
+                    effect::set_status(deleted_item_status(
+                        ctx.model.item_display(&cat_name, &item_name),
+                        ctx.model.category_display(&cat_name),
+                    )),
                 ];
                 effects.extend(retreat_from_deleted_item(ctx));
                 effects

crates/improvise-command/src/command/cmd/tile.rs

@@ -8,6 +8,28 @@ mod tests {
     use super::*;
     use crate::command::cmd::test_helpers::*;
 
+    #[test]
+    fn a_tile_status_names_the_display_not_the_key() {
+        let mut m = two_cat_model();
+        m.model
+            .category_mut("Type")
+            .unwrap()
+            .set_display("Kind of food and drink");
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let mut ctx = make_ctx(&m, &layout, &reg);
+        ctx.tile_cat_idx = ctx
+            .view
+            .tileable_cats(&ctx.model.category_names())
+            .iter()
+            .position(|c| *c == "Type")
+            .unwrap();
+        let effects = TileAxisOp { axis: None }.execute(&ctx);
+        let said = format!("{:?}", effects.last().unwrap());
+        assert!(said.contains("Kind of food and drink → "), "{said}");
+        assert!(!said.contains("Type →"), "the key was said: {said}");
+    }
+
     #[test]
     fn tile_axis_cycle_produces_cycle_effect() {
         let m = two_cat_model();
@@ -161,7 +183,10 @@ impl Cmd for TileAxisOp {
                 }),
                 None => Box::new(effect::CycleAxis(ViewTarget::Active, name.to_string())),
             };
-            let status = format!("{} → {}", name, new_axis.plain_label());
+            let status = improvise_protocol::viewmodel::axis_change_status(
+                ctx.model.category_display(name),
+                new_axis,
+            );
             vec![axis_effect, effect::set_status(status)]
         } else {
             vec![]

crates/improvise-command/src/ui/app.rs

@@ -332,12 +332,9 @@ impl Grids<'_> {
     pub fn unwritable(&self, view: &str, cell: &RecordCell) -> Option<String> {
         let key = self.resolve_cell(view, cell)?;
         let model = &self.app.model_state.workbook.model;
-        let derived = model.formula_for(&key).map(|f| {
-            format!(
-                "{} is computed by a formula — edit the formula, not the cell",
-                f.target
-            )
-        });
+        let derived = model
+            .formula_for(&key)
+            .map(|f| crate::command::cmd::core::derived_refusal(&f.target));
         let refusal = self.app.non_item_refusal(&key).or(derived);
         refusal.or_else(|| self.aggregate_refusal(view, cell.record, &key))
     }
@@ -772,9 +769,9 @@ impl App {
     /// (improvise-b114, improvise-nacd). See `context/code/command.md`.
     fn non_item_refusal(&self, key: &CellKey) -> Option<String> {
         let model = &self.model_state.workbook.model;
-        model
-            .first_non_item(key)
-            .map(|(cat, name)| improvise_protocol::non_item_refusal(cat, name))
+        model.first_non_item(key).map(|(cat, name)| {
+            improvise_protocol::non_item_refusal(model.category_display(cat), name)
+        })
     }
 
     /// Point **this client's** slice at `name`, if the document has such a view,
@@ -5620,6 +5617,71 @@ mod non_item_key_tests {
         assert_eq!(app.view_state.status_msg, refusal("Mars"));
     }
 
+    #[test]
+    fn a_refused_wire_write_names_the_category_it_shows() {
+        const REGION: &str = "Sales territory of the whole company";
+        let mut app = paged_app("East");
+        let stray = CellKey::new(vec![
+            ("Month".into(), "Jan".into()),
+            ("Region".into(), "Mars".into()),
+            ("_Measure".into(), "Revenue".into()),
+        ]);
+        let model = &mut app.model_state.workbook.model;
+        model.set_cell(stray.clone(), CellValue::Number(2.0));
+        model.category_mut("Region").unwrap().set_display(REGION);
+        model.add_formula(
+            crate::formula::parse_formula("Profit = Revenue - 1", "_Measure").unwrap(),
+        );
+        let refused = |key: &CellKey, measure: &str| {
+            let cell = RecordCell {
+                record: RecordHash::of(key),
+                measure: Some(measure.into()),
+            };
+            app.unwritable(app.view_name(), &cell)
+        };
+        let why = refused(&stray, "Revenue").expect("a non-item is refused");
+        assert!(why.contains(REGION), "{why}");
+        assert!(
+            why.starts_with("Mars "),
+            "the stray coordinate is a key: {why}"
+        );
+        let profit = CellKey::new(vec![
+            ("Month".into(), "Jan".into()),
+            ("Region".into(), "East".into()),
+            ("_Measure".into(), "Profit".into()),
+        ]);
+        let why = refused(&profit, "Profit").expect("a formula's result is refused");
+        assert!(why.starts_with("Profit is computed by a formula"), "{why}");
+    }
+
+    #[test]
+    fn a_non_item_refusal_names_the_categorys_display() {
+        let mut app = paged_app("Mars");
+        app.model_state
+            .workbook
+            .model
+            .category_mut("Region")
+            .unwrap()
+            .set_display("Sales territory of the whole company");
+        press(&mut app, "i");
+        assert_eq!(
+            app.view_state.status_msg,
+            improvise_protocol::non_item_refusal("Sales territory of the whole company", "Mars"),
+        );
+        app.view_state.yanked = Some(CellValue::Number(7.0));
+        press(&mut app, "p");
+        assert!(
+            app.view_state
+                .status_msg
+                .ends_with(&improvise_protocol::non_item_refusal(
+                    "Sales territory of the whole company",
+                    "Mars"
+                )),
+            "{}",
+            app.view_state.status_msg
+        );
+    }
+
     /// improvise-yc9r: `p` on a non-item cell writes no orphan. Evidence file.
     #[test]
     fn p_on_a_non_item_cell_writes_nothing() {
@@ -5655,6 +5717,21 @@ mod non_item_key_tests {
         assert!(status.ends_with(&refusal("Mars")), "{status}");
     }
 
+    #[test]
+    fn a_commit_on_a_non_item_cell_names_the_categorys_display() {
+        const REGION: &str = "Sales territory of the whole company";
+        let mut app = paged_app("Mars");
+        let region = app.model_state.workbook.model.category_mut("Region");
+        region.unwrap().set_display(REGION);
+        press(&mut app, ":enter-mode editing\n");
+        press(&mut app, "5\n");
+        let said = &app.view_state.status_msg;
+        assert!(
+            said.ends_with(&improvise_protocol::non_item_refusal(REGION, "Mars")),
+            "{said}"
+        );
+    }
+
     /// `uneditable` declines a non-item cell, so an advance re-opens no editor
     /// on one (#265 meets #277). Evidence: `context/test-evidence/command.md`.
     #[test]

crates/improvise-core/src/model/id.rs

@@ -1,6 +1,7 @@
-//! How an id is made: `slugify`, and the document's `IdAllocator` (ADR 007 clause 4).
-//! Reasoning: `context/code/core.md` §20.
-use std::collections::HashSet;
+//! How an id is made: `slugify`, and the document's `IdAllocator` (ADR 007 clause 4
+//! and its amendment). Reasoning: `context/code/core.md` §20.
+use std::cmp::Ordering;
+use std::collections::{HashMap, HashSet};
 
 /// What a generated id names; spells the `<kind>` of an empty slug's `<kind>-<n>`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -9,6 +10,7 @@ pub enum IdKind {
     Item,
     Formula,
     View,
+    Group,
 }
 
 impl IdKind {
@@ -18,38 +20,111 @@ impl IdKind {
             IdKind::Item => "item",
             IdKind::Formula => "formula",
             IdKind::View => "view",
+            IdKind::Group => "group",
         }
     }
 }
 
-/// The only ids that may begin with `_` (answer 23).
-pub const VIRTUAL_IDS: [&str; 3] = ["_index", "_dim", "_measure"];
+/// The only ids that may begin with `_` (amendment 1, clause 1).
+pub const VIRTUAL_IDS: [&str; 5] = ["_index", "_dim", "_measure", "_records", "_drill"];
 
-/// A display name's slug; empty when nothing survives (answers 16, 18, 21, 23, 26).
+/// A display name's slug; empty when nothing survives (amendment 1, clause 4).
 pub fn slugify(display: &str) -> String {
     let folded = unicase::UniCase::new(display).to_folded_case();
-    let kept: String = underscore_space_runs(&folded)
+    let mut slug = String::new();
+    for c in folded
         .chars()
-        .filter(|&c| in_id_alphabet(c))
-        .collect();
-    kept.trim_start_matches('_').to_string()
+        .map(|c| if in_slug_alphabet(c) { c } else { '_' })
+    {
+        if !(c == '_' && slug.ends_with('_')) {
+            slug.push(c);
+        }
+    }
+    let trimmed = slug.trim_matches(|c| c == '_' || c == '-');
+    if trimmed.starts_with(|c: char| c.is_ascii_digit()) {
+        format!("n{trimmed}")
+    } else {
+        trimmed.to_string()
+    }
 }
 
-fn underscore_space_runs(s: &str) -> String {
-    let (out, _) = s
-        .chars()
-        .fold((String::new(), false), |(mut out, prev), c| {
-            let space = c == ' ';
-            if !(space && prev) {
-                out.push(if space { '_' } else { c });
-            }
-            (out, space)
-        });
-    out
+fn in_slug_alphabet(c: char) -> bool {
+    matches!(c, 'a'..='z' | '0'..='9' | '-')
 }
 
-fn in_id_alphabet(c: char) -> bool {
-    matches!(c, 'a'..='z' | '0'..='9' | '-' | '_')
+/// Whether `id` has the syntax of a generated id: a letter, then `a`-`z`, `0`-`9`,
+/// `-` and single underscores, never ending in `_` or `-`. A virtual id fails it.
+pub fn is_id_syntax(id: &str) -> bool {
+    let b = id.as_bytes();
+    let edges = matches!(b.first(), Some(b'a'..=b'z')) && !matches!(b.last(), Some(b'_' | b'-'));
+    edges && b.windows(2).all(|w| w != b"__") && id.chars().all(|c| in_slug_alphabet(c) || c == '_')
+}
+
+/// Ids in natural order: digit runs by value, then fewer leading zeros first.
+pub fn natural_cmp(a: &str, b: &str) -> Ordering {
+    let (mut ra, mut rb) = (runs(a), runs(b));
+    loop {
+        match (ra.next(), rb.next()) {
+            (None, None) => return Ordering::Equal,
+            (None, Some(_)) => return Ordering::Less,
+            (Some(_), None) => return Ordering::Greater,
+            (Some(x), Some(y)) => match run_cmp(x, y) {
+                Ordering::Equal => {}
+                other => return other,
+            },
+        }
+    }
+}
+
+fn runs(s: &str) -> impl Iterator<Item = &str> {
+    let mut rest = s;
+    std::iter::from_fn(move || {
+        let digit = rest.chars().next()?.is_ascii_digit();
+        let end = rest
+            .find(|c: char| c.is_ascii_digit() != digit)
+            .unwrap_or(rest.len());
+        let (run, tail) = rest.split_at(end);
+        rest = tail;
+        Some(run)
+    })
+}
+
+fn run_cmp(x: &str, y: &str) -> Ordering {
+    let digits = |r: &str| r.starts_with(|c: char| c.is_ascii_digit());
+    if digits(x) && digits(y) {
+        let (vx, vy) = (x.trim_start_matches('0'), y.trim_start_matches('0'));
+        vx.len()
+            .cmp(&vy.len())
+            .then_with(|| vx.cmp(vy))
+            .then_with(|| x.len().cmp(&y.len()))
+    } else {
+        x.cmp(y)
+    }
+}
+
+/// What each `(id, display)` pair is shown as: equal displays get ` #2`, ` #3`, …
+/// in natural id order, skipping numbers a literal display already holds.
+pub fn display_suffixes(items: &[(&str, &str)]) -> Vec<String> {
+    let literal: HashSet<&str> = items.iter().map(|&(_, d)| d).collect();
+    let mut groups: HashMap<&str, Vec<usize>> = HashMap::new();
+    for (i, &(_, d)) in items.iter().enumerate() {
+        groups.entry(d).or_default().push(i);
+    }
+    let mut shown: Vec<String> = items.iter().map(|&(_, d)| d.to_string()).collect();
+    for (display, mut at) in groups {
+        at.sort_by(|&i, &j| natural_cmp(items[i].0, items[j].0));
+        let mut n = 2;
+        for &i in at.iter().skip(1) {
+            shown[i] = loop {
+                let candidate = format!("{display} #{n}");
+                n += 1;
+                if !literal.contains(candidate.as_str()) {
+                    break candidate;
+                }
+            };
+        }
+    }
+    shown
 }
 
 /// Why a hand-written id cannot enter the document.
@@ -81,12 +156,13 @@ impl IdAllocator {
         Self::default()
     }
 
-    /// Admit a hand-written id verbatim: it is canonical and never renamed (answer 29).
+    /// Admit a hand-written id verbatim: it is canonical and never renamed.
     pub fn claim(&mut self, id: &str) -> Result<(), ClaimError> {
-        let refusal = if id.is_empty() || !id.chars().all(in_id_alphabet) {
-            Some(ClaimError::Malformed(id.to_string()))
-        } else if id.starts_with('_') && !VIRTUAL_IDS.contains(&id) {
+        let virtual_id = VIRTUAL_IDS.contains(&id);
+        let refusal = if id.starts_with('_') && !virtual_id {
             Some(ClaimError::Reserved(id.to_string()))
+        } else if !virtual_id && !is_id_syntax(id) {
+            Some(ClaimError::Malformed(id.to_string()))
         } else if self.seen.contains(id) {
             Some(ClaimError::Duplicate(id.to_string()))
         } else {
@@ -132,16 +208,26 @@ mod tests {
     use proptest::prelude::*;
 
     #[test]
-    fn slugify_follows_the_adrs_examples() {
+    fn slugify_follows_the_amendments_table() {
         let cases = [
-            ("East", "east"),
             ("Time Period", "time_period"),
-            ("Coastal_East", "coastal_east"),
-            ("Q1-2024", "q1-2024"),
-            ("Region(code)", "regioncode"),
-            ("Café", "caf"),
-            ("_Draft", "draft"),
+            ("Time\tPeriod", "time_period"),
+            ("Time \u{200B} Period", "time_period"),
+            ("a_ b", "a_b"),
+            ("a__b", "a_b"),
+            ("Q1 - 2024", "q1_-_2024"),
+            ("East ", "east"),
+            ("East_", "east"),
+            ("-East-", "east"),
+            ("Region(code)", "region_code"),
+            ("Crème Brûlée", "cr_me_br_l_e"),
+            ("2024", "n2024"),
+            ("_2024", "n2024"),
+            ("2024-Q1", "n2024-q1"),
             ("Ü", ""),
+            ("-", ""),
+            ("%", ""),
+            ("", ""),
         ];
         for (display, slug) in cases {
             assert_eq!(slugify(display), slug, "slugify({display:?})");
@@ -153,18 +239,25 @@ mod tests {
         assert_eq!(slugify("Straße"), "strasse");
         assert_eq!(slugify("ſtate"), "state");
         assert_eq!(slugify("file"), "file");
+        assert_eq!(slugify("İ"), "i");
     }
 
     #[test]
-    fn slugify_collapses_a_run_of_spaces_to_one_underscore() {
-        assert_eq!(slugify("Time   Period"), "time_period");
-        assert_eq!(slugify("East "), "east_");
+    fn slugify_trims_hyphens_and_underscores_until_neither_is_at_an_end() {
+        assert_eq!(slugify("_-_East-_-"), "east");
+        assert_eq!(slugify("-_-"), "");
     }
 
     #[test]
-    fn slugify_keeps_an_underscore_the_display_already_had() {
-        assert_eq!(slugify("a_ b"), "a__b");
-        assert_eq!(slugify("a__b"), "a__b");
+    fn slugify_trims_before_it_prepends_the_n() {
+        assert_eq!(slugify("-_7up"), "n7up");
+        assert_eq!(slugify("n-7"), "n-7");
+    }
+
+    #[test]
+    fn slugify_keeps_a_hyphen_between_underscores() {
+        assert_eq!(slugify("a - b"), "a_-_b");
+        assert_eq!(slugify("a_-b"), "a_-b");
     }
 
     #[test]
@@ -173,6 +266,8 @@ mod tests {
         assert_eq!(ids.generate(IdKind::Category, "Ü"), "category-1");
         assert_eq!(ids.generate(IdKind::Item, "Ö"), "item-2");
         assert_eq!(ids.generate(IdKind::View, ""), "view-3");
+        assert_eq!(ids.generate(IdKind::Group, "-"), "group-4");
+        assert_eq!(ids.generate(IdKind::Formula, "%"), "formula-5");
     }
 
     #[test]
@@ -197,6 +292,15 @@ mod tests {
         assert_eq!(ids.generate(IdKind::Item, "EAST"), "east-3");
     }
 
+    #[test]
+    fn a_hyphenated_slug_and_a_counter_suffix_never_collide() {
+        let mut ids = IdAllocator::new();
+        assert_eq!(ids.generate(IdKind::Item, "East"), "east");
+        assert_eq!(ids.generate(IdKind::Item, "East-1"), "east-1");
+        assert_eq!(ids.generate(IdKind::Item, "east"), "east-2");
+        assert_eq!(ids.generate(IdKind::Item, "East-1"), "east-1-3");
+    }
+
     #[test]
     fn a_claimed_id_keeps_its_spelling_and_generation_steps_past_it() {
         let mut ids = IdAllocator::new();
@@ -224,10 +328,21 @@ mod tests {
         );
     }
 
+    #[test]
+    fn claim_refuses_what_a_generated_id_could_not_be() {
+        let mut ids = IdAllocator::new();
+        for bad in ["-x", "x-", "2024", "a__b", "x_", "-", "a b", "é"] {
+            assert_eq!(ids.claim(bad), Err(ClaimError::Malformed(bad.into())));
+        }
+        for good in ["east-1", "item-4", "a-7", "q1_-_2024", "a_b", "x"] {
+            assert_eq!(ids.claim(good), Ok(()), "{good}");
+        }
+    }
+
     #[test]
     fn claim_refuses_an_id_that_only_begins_like_a_virtual_one() {
         let mut ids = IdAllocator::new();
-        for lookalike in ["_indexer", "_measure-1", "_dim_2", "_measures"] {
+        for lookalike in ["_indexer", "_measure-1", "_dim_2", "_measures", "_recordsx"] {
             assert_eq!(
                 ids.claim(lookalike),
                 Err(ClaimError::Reserved(lookalike.into()))
@@ -235,10 +350,20 @@ mod tests {
         }
     }
 
+    #[test]
+    fn claim_admits_each_virtual_id_once() {
+        let mut ids = IdAllocator::new();
+        for v in ["_index", "_dim", "_measure", "_records", "_drill"] {
+            assert_eq!(ids.claim(v), Ok(()));
+            assert_eq!(ids.claim(v), Err(ClaimError::Duplicate(v.into())));
+        }
+    }
+
     #[test]
     fn a_display_with_leading_spaces_never_slugs_into_the_reserved_space() {
         assert_eq!(slugify(" Draft"), "draft");
         assert_eq!(slugify("  _ Draft"), "draft");
+        assert_eq!(slugify("_Drill"), "drill");
     }
 
     #[test]
@@ -272,7 +397,159 @@ mod tests {
         assert_eq!(run(), run());
     }
 
+    #[test]
+    fn natural_order_puts_a_counter_suffix_in_numeric_order() {
+        let mut ids = vec!["profit-10", "profit-2", "profit", "profit-1"];
+        ids.sort_by(|a, b| natural_cmp(a, b));
+        assert_eq!(ids, ["profit", "profit-1", "profit-2", "profit-10"]);
+    }
+
+    #[test]
+    fn natural_order_ties_on_value_go_to_fewer_leading_zeros() {
+        assert_eq!(natural_cmp("a-7", "a-007"), Ordering::Less);
+        assert_eq!(natural_cmp("a-007", "a-7"), Ordering::Greater);
+        assert_eq!(natural_cmp("a-07", "a-007"), Ordering::Less);
+        assert_eq!(natural_cmp("a-7", "a-7"), Ordering::Equal);
+    }
+
+    #[test]
+    fn natural_order_compares_digit_runs_of_any_length_by_value() {
+        let big = "9".repeat(40);
+        let bigger = format!("1{}", "0".repeat(40));
+        assert_eq!(
+            natural_cmp(&format!("x{big}"), &format!("x{bigger}")),
+            Ordering::Less
+        );
+        assert_eq!(natural_cmp("x9", "x10"), Ordering::Less);
+        assert_eq!(natural_cmp("x000", "x0"), Ordering::Greater);
+    }
+
+    #[test]
+    fn natural_order_decides_the_zeros_tie_at_its_own_run_not_after_the_rest() {
+        assert_eq!(natural_cmp("a-7c", "a-007b"), Ordering::Less);
+        assert_eq!(natural_cmp("a-7b", "a-007a"), Ordering::Less);
+        assert_eq!(natural_cmp("a-007a", "a-7b"), Ordering::Greater);
+    }
+
+    #[test]
+    fn natural_order_puts_the_id_that_runs_out_of_runs_first() {
+        assert_eq!(natural_cmp("a", "a-1"), Ordering::Less);
+        assert_eq!(natural_cmp("a-1", "a-1-b"), Ordering::Less);
+        assert_eq!(natural_cmp("a-1b", "a-1"), Ordering::Greater);
+    }
+
+    #[test]
+    fn natural_order_compares_non_digit_runs_by_bytes() {
+        assert_eq!(natural_cmp("b1", "a2"), Ordering::Greater);
+        assert_eq!(natural_cmp("a-1", "a_1"), Ordering::Less);
+    }
+
+    #[test]
+    fn a_suffix_numbers_equal_displays_in_natural_id_order() {
+        let items = [
+            ("profit-10", "Profit"),
+            ("profit", "Profit"),
+            ("profit-2", "Profit"),
+            ("profit-1", "Profit"),
+            ("cost", "Cost"),
+        ];
+        assert_eq!(
+            display_suffixes(&items),
+            ["Profit #4", "Profit", "Profit #3", "Profit #2", "Cost"]
+        );
+    }
+
+    #[test]
+    fn a_suffix_skips_a_number_a_literal_display_already_holds() {
+        let items = [
+            ("profit", "Profit"),
+            ("profit-1", "Profit"),
+            ("profit-2", "Profit"),
+            ("p2", "Profit #2"),
+        ];
+        assert_eq!(
+            display_suffixes(&items),
+            ["Profit", "Profit #3", "Profit #4", "Profit #2"]
+        );
+    }
+
+    #[test]
+    fn a_suffix_is_gapless_when_a_thing_goes_away() {
+        let three = [("p", "Profit"), ("p-1", "Profit"), ("p-2", "Profit")];
+        assert_eq!(
+            display_suffixes(&three),
+            ["Profit", "Profit #2", "Profit #3"]
+        );
+        let two = [("p", "Profit"), ("p-2", "Profit")];
+        assert_eq!(display_suffixes(&two), ["Profit", "Profit #2"]);
+    }
+
+    #[test]
+    fn a_unique_display_is_shown_unchanged() {
+        let items = [("a", "East"), ("b", "West")];
+        assert_eq!(display_suffixes(&items), ["East", "West"]);
+        assert!(display_suffixes(&[]).is_empty());
+    }
+
+    /// `^[a-z](_?[a-z0-9-])*$` and not ending in `-`, without the crate's own helpers.
+    fn regex_free_match(id: &str) -> bool {
+        let mut cs = id.chars().peekable();
+        if !matches!(cs.next(), Some('a'..='z')) {
+            return false;
+        }
+        while cs.peek().is_some() {
+            if cs.peek() == Some(&'_') {
+                cs.next();
+            }
+            if !matches!(cs.next(), Some('a'..='z' | '0'..='9' | '-')) {
+                return false;
+            }
+        }
+        !id.ends_with('-')
+    }
+
+    fn id_text() -> impl Strategy<Value = String> {
+        "[a-c0-3_-]{0,7}"
+    }
+
     proptest! {
+        #[test]
+        fn slugify_output_has_the_id_syntax_and_is_a_fixed_point(display in ".{0,12}") {
+            let slug = slugify(&display);
+            prop_assert!(slug.is_empty() || is_id_syntax(&slug), "{slug:?}");
+            prop_assert_eq!(slugify(&slug), slug);
+        }
+
+        #[test]
+        fn id_syntax_agrees_with_an_independent_checker(id in "[a-cA-C0-9 _%é-]{0,8}") {
+            prop_assert_eq!(is_id_syntax(&id), regex_free_match(&id), "{}", id);
+        }
+
+        #[test]
+        fn natural_order_is_a_total_order(a in id_text(), b in id_text(), c in id_text()) {
+            prop_assert_eq!(natural_cmp(&a, &b), natural_cmp(&b, &a).reverse());
+            prop_assert_eq!(natural_cmp(&a, &b) == Ordering::Equal, a == b);
+            if natural_cmp(&a, &b) != Ordering::Greater && natural_cmp(&b, &c) != Ordering::Greater {
+                prop_assert!(natural_cmp(&a, &c) != Ordering::Greater);
+            }
+        }
+
+        #[test]
+        fn suffixed_displays_are_distinct_when_literals_already_hold_suffixes(
+            shared in proptest::collection::vec(0usize..4, 0..8)
+        ) {
+            let displays = ["A", "A #2", "A #3", "B"];
+            let ids: Vec<String> = (0..shared.len()).map(|n| format!("x-{n}")).collect();
+            let items: Vec<(&str, &str)> = ids
+                .iter()
+                .zip(&shared)
+                .map(|(i, &d)| (i.as_str(), displays[d]))
+                .collect();
+            let shown = display_suffixes(&items);
+            let distinct: HashSet<&String> = shown.iter().collect();
+            prop_assert_eq!(distinct.len(), shown.len());
+        }
+
         #[test]
         fn generated_ids_are_distinct_well_formed_and_never_reserved(
             displays in proptest::collection::vec(".{0,6}", 0..24)
@@ -281,8 +558,7 @@ mod tests {
             let mut out = HashSet::new();
             for d in &displays {
                 let id = ids.generate(IdKind::Item, d);
-                prop_assert!(!id.is_empty() && !id.starts_with('_'), "{id:?}");
-                prop_assert!(id.chars().all(|c| matches!(c, 'a'..='z' | '0'..='9' | '-' | '_')));
+                prop_assert!(is_id_syntax(&id), "{id:?}");
                 prop_assert!(out.insert(id.clone()), "reissued {id:?}");
             }
         }

crates/improvise-protocol/src/lib.rs

@@ -402,7 +402,14 @@ impl AppMode {
     }
 
     pub fn item_add(category: String) -> Self {
-        let prompt = format!("add item to {category}: ");
+        let shown = category.clone();
+        Self::item_add_shown(category, &shown)
+    }
+
+    /// The prompt names the category by what a person sees; `category` stays the
+    /// key the commit adds the item to (improvise-cq1q.13).
+    pub fn item_add_shown(category: String, shown: &str) -> Self {
+        let prompt = format!("add item to {shown}: ");
         Self::ItemAdd {
             category,
             minibuf: MinibufferConfig {

crates/improvise-protocol/src/render.rs

@@ -68,8 +68,8 @@ pub enum CellId {
     NonItem { category: String, item: String },
 }
 
-/// Why a cell whose coordinate names no item takes no write. One wording for the
-/// projection's decline and the host's refusal (improvise-gk51).
+/// Why a cell naming no item takes no write (improvise-gk51). `category` is a
+/// display; `item` is the stray key, which has none (`core.md` §21).
 pub fn non_item_refusal(category: &str, item: &str) -> String {
     format!("{item} is no item of {category}, so there is no one cell to write")
 }
@@ -838,6 +838,19 @@ impl CategoryTreeCache {
     pub fn category(&self, name: &str) -> Option<&CategoryRow> {
         self.categories.iter().find(|c| c.name == name)
     }
+
+    /// What a person sees for a category key; the key when the cache lacks it.
+    /// For a message only: never pass the result to a lookup (core.md §21).
+    pub fn category_display<'a>(&'a self, name: &'a str) -> &'a str {
+        self.category(name).map_or(name, |c| c.display.as_str())
+    }
+
+    /// What a person sees for an item of `cat`; the key when either is absent.
+    pub fn item_display<'a>(&'a self, cat: &str, item: &'a str) -> &'a str {
+        self.category(cat)
+            .and_then(|c| c.items.iter().find(|i| i.name == item))
+            .map_or(item, |i| i.display.as_str())
+    }
 }
 
 /// Three mutations, because the effects are three *shapes*. `Items` and
@@ -955,6 +968,17 @@ pub struct ViewListCache {
     pub views: Vec<ViewSummary>,
 }
 
+impl ViewListCache {
+    /// What a person sees for a view key; the key when the list lacks it.
+    /// For a title or a message only, never a lookup (core.md §21).
+    pub fn display_of<'a>(&'a self, key: &'a str) -> &'a str {
+        self.views
+            .iter()
+            .find(|v| v.name == key)
+            .map_or(key, |v| v.display.as_str())
+    }
+}
+
 impl WidgetCache for ViewListCache {
     type Update = Vec<ViewSummary>;
 

crates/improvise-protocol/src/resolve.rs

@@ -7,7 +7,10 @@ use serde::{Deserialize, Serialize};
 use crate::client::{ClientState, Opened, OpenedCell, OpenedTarget};
 use crate::frame::ClientFrame;
 use crate::keymap::{Binding, Keymaps, ModeKey};
-use crate::viewmodel::{CatTreeEntry, axis_change_status, flatten_cat_tree};
+use crate::viewmodel::{
+    CatTreeEntry, axis_change_status, deleted_category_status, deleted_item_status, filter_status,
+    flatten_cat_tree,
+};
 use crate::{
     AppMode, CellId, CellValue, Command, CreateKind, FormulaId, FormulaSlot, GridExtent, HelpPage,
     KeyCode, KeyEvent, ModelCommand, Panel, RECORD_COORDS_CANNOT_BE_EMPTY, RecordCell, ViewState,
@@ -579,8 +582,9 @@ fn composed(
                         category: cat.clone(),
                     },
                 )?];
+                let shown = state.categories.category_display(&cat);
                 commands
-                    .extend(cycled.map(|axis| Command::SetStatus(axis_change_status(&cat, axis))));
+                    .extend(cycled.map(|axis| Command::SetStatus(axis_change_status(shown, axis))));
                 commands
             }
             None => vec![Command::SetStatus(
@@ -592,7 +596,10 @@ fn composed(
         "delete-formula-at-cursor" => delete_formula_at_cursor(state),
 
         "open-item-add-at-cursor" => Some(match cat_at_cursor(state) {
-            Some(cat) => vec![Command::ChangeMode(AppMode::item_add(cat))],
+            Some(cat) => {
+                let shown = state.categories.category_display(&cat).to_string();
+                vec![Command::ChangeMode(AppMode::item_add_shown(cat, &shown))]
+            }
             None => vec![Command::SetStatus(
                 "No category selected. Press n to add a category first.".to_string(),
             )],
@@ -961,7 +968,7 @@ fn edit_or_drill(state: &ClientState, mode: AppMode) -> Option<Vec<Command>> {
         // them; declining rather than `None` keeps that a door, not a hole.
         CellId::Create(_) => Some(vec![Command::SetStatus(not_yet("creating a column"))]),
         CellId::NonItem { category, item } => Some(vec![Command::SetStatus(
-            crate::non_item_refusal(category, item),
+            crate::non_item_refusal(state.categories.category_display(category), item),
         )]),
     }
 }
@@ -1400,7 +1407,10 @@ pub(crate) fn declined_at(state: &ClientState, row: usize, col: usize) -> Option
     match projected_at(state, row, col)?.id.as_ref()? {
         CellId::Aggregate(_) => Some(AGGREGATE_DECLINE.to_string()),
         CellId::Derived { target } => Some(derived_decline(target)),
-        CellId::NonItem { category, item } => Some(crate::non_item_refusal(category, item)),
+        CellId::NonItem { category, item } => Some(crate::non_item_refusal(
+            state.categories.category_display(category),
+            item,
+        )),
         CellId::Record(_) | CellId::Create(_) | CellId::Coordinate { .. } => None,
     }
 }
@@ -1613,7 +1623,7 @@ fn filter_to_item_at(state: &ClientState, index: usize) -> Option<Vec<Command>>
         Some(CatTreeEntry::Item {
             cat_name,
             item_name,
-            ..
+            display,
         }) => Some(vec![
             model(
                 state,
@@ -1631,7 +1641,10 @@ fn filter_to_item_at(state: &ClientState, index: usize) -> Option<Vec<Command>>
                     item: item_name.clone(),
                 },
             )?,
-            Command::SetStatus(format!("Filter: {cat_name} = {item_name}")),
+            Command::SetStatus(filter_status(
+                state.categories.category_display(&cat_name),
+                &display,
+            )),
         ]),
         Some(CatTreeEntry::Category { .. }) => Some(toggle_cat_expand_at(state, index)),
         None => Some(Vec::new()),
@@ -1642,14 +1655,14 @@ fn filter_to_item_at(state: &ClientState, index: usize) -> Option<Vec<Command>>
 /// row deletes the item, and an empty tree says so.
 fn delete_at_cat_cursor(state: &ClientState) -> Option<Vec<Command>> {
     match cat_tree_entry(state) {
-        Some(CatTreeEntry::Category { name, .. }) => Some(vec![
+        Some(CatTreeEntry::Category { name, display, .. }) => Some(vec![
             model(state, ModelCommand::RemoveCategory(name.clone()))?,
-            Command::SetStatus(format!("Deleted category '{name}'")),
+            Command::SetStatus(deleted_category_status(&display)),
         ]),
         Some(CatTreeEntry::Item {
             cat_name,
             item_name,
-            ..
+            display,
         }) => {
             let mut commands = vec![
                 model(
@@ -1659,7 +1672,10 @@ fn delete_at_cat_cursor(state: &ClientState) -> Option<Vec<Command>> {
                         item: item_name.clone(),
                     },
                 )?,
-                Command::SetStatus(format!("Deleted item '{item_name}' from '{cat_name}'")),
+                Command::SetStatus(deleted_item_status(
+                    &display,
+                    state.categories.category_display(&cat_name),
+                )),
             ];
             commands.extend(retreat_from_deleted_item(state));
             Some(commands)
@@ -1786,7 +1802,7 @@ fn tile_axis_at(state: &ClientState, index: usize, axis: Option<Axis>) -> Option
     };
     Some(vec![
         model(state, cmd)?,
-        Command::SetStatus(axis_change_status(&tile.category, new_axis)),
+        Command::SetStatus(axis_change_status(&tile.display, new_axis)),
     ])
 }
 
@@ -5014,3 +5030,162 @@ mod opened_editor_wire_tests {
         );
     }
 }
+
+#[cfg(test)]
+mod display_tests {
+    use super::*;
+    use crate::{
+        AxisFrame, CategoryItem, CategoryRow, CategoryTreeUpdate, CellDisplay, GridExtent,
+        GridUpdate, KeyModifiers, Projection, Snapshot, TileEntry, ViewState,
+    };
+
+    const REGION: &str = "Sales territory of the whole company";
+    const NORTH: &str = "Northern reaches and the colder coasts";
+
+    fn ev(code: KeyCode) -> KeyEvent {
+        KeyEvent::new(code, KeyModifiers::NONE)
+    }
+
+    fn shown(name: &str, display: &str) -> CategoryItem {
+        CategoryItem {
+            name: name.into(),
+            display: display.into(),
+        }
+    }
+
+    /// Every key differs from, and is far shorter than, what a person sees.
+    fn displayed(cell: Option<CellId>) -> ClientState {
+        let mut state = ClientState::default();
+        let mut first = CellDisplay::number("1");
+        first.id = cell;
+        state.bootstrap(Snapshot {
+            view: ViewState::default(),
+            seed: vec![
+                Projection::CategoryTree(CategoryTreeUpdate::Categories(vec![CategoryRow {
+                    name: "Region".into(),
+                    display: REGION.into(),
+                    items: vec![shown("North", NORTH)],
+                    axis: Axis::Row,
+                }])),
+                Projection::TileBar(vec![TileEntry {
+                    category: "Region".into(),
+                    display: REGION.into(),
+                    axis: Axis::Row,
+                    kind: crate::CategoryKind::Regular,
+                }]),
+                Projection::Grid(GridUpdate::RowFrame(AxisFrame::flat(["North"]))),
+                Projection::Grid(GridUpdate::ColFrame(AxisFrame::flat(["Total"]))),
+                Projection::Grid(GridUpdate::Cells(vec![((0, 0), first)])),
+                Projection::Grid(GridUpdate::Extent(GridExtent { rows: 1, cols: 1 })),
+                Projection::Basis(crate::basis::published(7, 3, Default::default())),
+            ],
+        });
+        state.window = (1, 1);
+        state
+    }
+
+    fn last_status(commands: Vec<Command>) -> String {
+        match commands.last() {
+            Some(Command::SetStatus(said)) => said.clone(),
+            other => panic!("no status last in {commands:?}: {other:?}"),
+        }
+    }
+
+    fn local(state: &ClientState, code: KeyCode) -> Vec<Command> {
+        match resolve(state, ev(code)) {
+            KeyOutcome::Local(commands) => commands,
+            other => panic!("{code:?} did not resolve locally: {other:?}"),
+        }
+    }
+
+    #[test]
+    fn a_panel_status_names_what_a_person_sees_not_the_keys() {
+        let mut state = displayed(None);
+        state.view.mode = AppMode::CategoryPanel;
+        state.view.expanded_cats.insert("Region".into());
+        state.view.cat_panel_cursor = 0;
+        let cycled = last_status(local(&state, KeyCode::Char(' ')));
+        assert_eq!(cycled, format!("{REGION} → Col"));
+        let removal = delete_at_cat_cursor(&state).unwrap();
+        assert!(
+            removal.iter().any(|c| matches!(c, Command::Model {
+                cmd: ModelCommand::RemoveCategory(name), ..
+            } if name == "Region")),
+            "the removal names the key: {removal:?}"
+        );
+        let deleted = last_status(removal);
+        assert_eq!(deleted, format!("Deleted category '{REGION}'"));
+
+        state.view.cat_panel_cursor = 1;
+        let filtering = filter_to_item(&state).unwrap();
+        let named: Vec<String> = filtering
+            .iter()
+            .filter_map(|c| match c {
+                Command::Model {
+                    cmd: ModelCommand::SetPageSelection { category, item, .. },
+                    ..
+                } => Some(format!("{category}/{item}")),
+                _ => None,
+            })
+            .collect();
+        assert_eq!(named, ["Region/North"], "the lookup names keys");
+        let filtered = last_status(filtering);
+        assert_eq!(filtered, format!("Filter: {REGION} = {NORTH}"));
+        let removal = delete_at_cat_cursor(&state).unwrap();
+        assert!(
+            removal.iter().any(|c| matches!(c, Command::Model {
+                cmd: ModelCommand::RemoveItem { category, item }, ..
+            } if category == "Region" && item == "North")),
+            "the removal names keys: {removal:?}"
+        );
+        let deleted = last_status(removal);
+        assert_eq!(deleted, format!("Deleted item '{NORTH}' from '{REGION}'"));
+    }
+
+    #[test]
+    fn a_tile_status_names_the_display() {
+        let mut state = displayed(None);
+        state.view.mode = AppMode::TileSelect;
+        let said = last_status(tile_axis(&state, None).unwrap());
+        assert_eq!(said, format!("{REGION} → Col"));
+    }
+
+    #[test]
+    fn the_item_prompt_names_the_display_and_the_mode_keeps_the_key() {
+        let mut state = displayed(None);
+        state.view.mode = AppMode::CategoryPanel;
+        state.view.cat_panel_cursor = 0;
+        let commands = local(&state, KeyCode::Char('a'));
+        let Some(Command::ChangeMode(AppMode::ItemAdd { category, minibuf })) = commands
+            .iter()
+            .find(|c| matches!(c, Command::ChangeMode(_)))
+        else {
+            panic!("no item-add mode in {commands:?}");
+        };
+        assert_eq!(category, "Region", "the commit adds to the KEY");
+        assert_eq!(minibuf.prompt, format!("add item to {REGION}: "));
+    }
+
+    #[test]
+    fn the_declines_an_advance_and_a_commit_reach_name_the_category_it_shows() {
+        let stray = displayed(Some(CellId::NonItem {
+            category: "Region".into(),
+            item: "Mars".into(),
+        }));
+        let want = crate::non_item_refusal(REGION, "Mars");
+        assert_eq!(declined_at(&stray, 0, 0), Some(want.clone()));
+        assert_eq!(refused_here(&stray, "commit-cell-edit"), Some(want.clone()));
+        let advanced = reopened_at(&stray, 0, 0, AppMode::Normal, false);
+        assert_eq!(advanced, vec![Command::SetStatus(want)]);
+    }
+
+    #[test]
+    fn a_refused_cell_names_the_category_it_shows() {
+        let stray = displayed(Some(CellId::NonItem {
+            category: "Region".into(),
+            item: "Mars".into(),
+        }));
+        let said = last_status(local(&stray, KeyCode::Char('i')));
+        assert!(said.contains(REGION) && said.starts_with("Mars "), "{said}");
+    }
+}

crates/improvise-protocol/src/viewmodel.rs

@@ -37,12 +37,27 @@ impl CatTreeEntry {
     }
 }
 
-/// What a moved axis says on the status line. One home: the tile bar and the
-/// category panel are two routes to one operation — improvise-25bf.
+/// What a moved axis says on the status line: one home for the tile bar and the
+/// panel (improvise-25bf). Takes displays; `core.md` §21.
 pub fn axis_change_status(category: &str, axis: Axis) -> String {
     format!("{category} → {}", axis.plain_label())
 }
 
+/// What `filter-to-item` says; both ends, so one wording (improvise-cq1q.13).
+pub fn filter_status(category: &str, item: &str) -> String {
+    format!("Filter: {category} = {item}")
+}
+
+/// What deleting a category at the panel cursor says.
+pub fn deleted_category_status(category: &str) -> String {
+    format!("Deleted category '{category}'")
+}
+
+/// What deleting an item at the panel cursor says.
+pub fn deleted_item_status(item: &str, category: &str) -> String {
+    format!("Deleted item '{item}' from '{category}'")
+}
+
 /// Flatten the category panel: a header per category, then its items when
 /// expanded. The result index is `ViewState::cat_panel_cursor`.
 pub fn flatten_cat_tree(

crates/improvise-wasm-client/src/render.rs

@@ -243,7 +243,7 @@ pub fn render_model(state: &ClientState) -> RenderModel {
         mode: improvise_protocol::mode_label(&state.view.mode).to_string(),
         status: state.view.status_msg.clone(),
         status_stands: state.status_stands(),
-        view_name: state.view.active_view.clone(),
+        view_name: state.views.display_of(&state.view.active_view).to_string(),
         doc_name: state.document.name.clone(),
         doc_dirty: state.document.dirty,
         doc_stored_as: state.document.stored_as.clone(),
@@ -883,6 +883,24 @@ mod tests {
         assert!(views[0].active, "the active view is still found by its key");
     }
 
+    #[test]
+    fn the_title_names_the_active_views_display_not_its_key() {
+        let mut client = init();
+        let state = client.state_mut();
+        state.fold(&Command::Project(Projection::ViewList(vec![ViewSummary {
+            name: "Default".into(),
+            display: "Quarterly overview of regional sales".into(),
+            axes: vec![],
+        }])));
+        state.view.active_view = "Default".into();
+        assert_eq!(
+            client.model().view_name,
+            "Quarterly overview of regional sales"
+        );
+        client.state_mut().view.active_view = "Unlisted".into();
+        assert_eq!(client.model().view_name, "Unlisted", "no display: the key");
+    }
+
     #[test]
     fn the_grid_page_bar_and_item_rows_paint_displays() {
         use improvise_protocol::{AxisFrame, CategoryItem, FrameGroup};

src/draw.rs

@@ -409,7 +409,7 @@ fn draw_content(f: &mut Frame, area: Rect, app: &App) {
         GridWidget::new(
             &grid_cache,
             app.cursor(),
-            &app.view_state.active_view,
+            app.view().display(),
             &app.layout,
             &app.view_state.mode,
             &app.view_state.search_query,
@@ -1201,6 +1201,30 @@ mod content_tests {
             .collect()
     }
 
+    /// improvise-cq1q.13: evidence in `context/test-evidence/core.md`.
+    #[test]
+    fn the_grid_title_names_the_views_display_not_its_key() {
+        let mut wb = wide_grid();
+        wb.active_view_mut()
+            .set_display("Quarterly overview of regional sales");
+        let mut app = App::new(wb, None);
+        (app.term_width, app.term_height) = (100, 24);
+        let mut terminal = Terminal::new(TestBackend::new(100, 24)).expect("test backend");
+        terminal.draw(|f| draw(f, &app)).expect("draw");
+        let text: String = terminal
+            .backend()
+            .buffer()
+            .content()
+            .iter()
+            .map(|c| c.symbol())
+            .collect();
+        assert!(
+            text.contains("View: Quarterly overview of regional sales"),
+            "the title drew something else"
+        );
+        assert!(!text.contains("View: Default"), "the key was drawn");
+    }
+
     /// improvise-gtn7.1: the cursor went behind a side panel —
     /// `context/test-evidence/tui.md`.
     #[test]

src/ui/grid.rs

@@ -23,7 +23,8 @@ pub struct GridWidget<'a> {
     /// This client's cursor in the active view (improvise-8uz). Passed in
     /// rather than read off `View`, which no longer carries per-client state.
     pub cursor: ViewCursor,
-    pub view_name: &'a str,
+    /// What the title shows: the view's display, never its key (improvise-cq1q.13).
+    pub view_display: &'a str,
     pub layout: &'a GridLayout,
     pub mode: &'a AppMode,
     pub search_query: &'a str,
@@ -36,7 +37,7 @@ impl<'a> GridWidget<'a> {
     pub fn new(
         cache: &'a GridCache,
         cursor: ViewCursor,
-        view_name: &'a str,
+        view_display: &'a str,
         layout: &'a GridLayout,
         mode: &'a AppMode,
         search_query: &'a str,
@@ -46,7 +47,7 @@ impl<'a> GridWidget<'a> {
         Self {
             cache,
             cursor,
-            view_name,
+            view_display,
             layout,
             mode,
             search_query,
@@ -444,7 +445,7 @@ impl<'a> Widget for GridWidget<'a> {
     fn render(self, area: Rect, buf: &mut Buffer) {
         let block = Block::default()
             .borders(Borders::ALL)
-            .title(format!(" View: {} ", self.view_name));
+            .title(format!(" View: {} ", self.view_display));
         let inner = block.inner(area);
         block.render(area, buf);