improvise/context/test-evidence/clients.md

Test evidence: browser client, hosts, harness

What each of these tests proves, what fault was injected to prove it can fail, and — where it applies — the bug it was written against. Keyed by exact test name; a renamed test orphans its entry, which scripts/check-comment-runs.py --check-evidence reports.

The design argument each of these belongs to is in context/code/clients.md.

---

improvise-worker-server/src/worker.rs

an_edit_is_persisted_without_the_client_asking_to_save

The persistence half of improvise-9x6's acceptance criterion 2, and the reason the worker saves on its own behalf: there is no ModelCommand::Save for a client to send, because effect::Save is ViewOnly and the wire vocabulary is derived from the model effects. So an edit must reach storage with the client having asked for nothing but the edit. The test writes one cell over the wire and reopens the document through the same VFS.

a_partly_refused_batch_does_not_leave_disk_and_memory_disagreeing

improvise-955n's second-order effect, which nobody had written down until it was found while declining the ticket: on_frame skipped persist() when any frame in the answer was Rejected, so a batch that did apply its earlier command before being refused left the document moved in memory and not written back — disk and worker disagreeing, silently.

Two changes close it independently, which is why this is worth a test of its own rather than trusting either: the batch no longer applies partially at all (improvise-955n), and the persist trigger is now the document's own dirtiness rather than "was anything rejected" (improvise-gv9r), so a batch that did change something would be written whatever else the answer contained.

The fixture is a refused frame with a command behind the refusal, and the assertion is that the axes on disk and the axes in memory agree. Under the settled contract the refusal comes from the frame's basis — answered once, on the first command that carries one — so that is where the staleness is injected; a later command carries no answer of its own.

an_explicit_save_is_not_retried_by_the_automatic_write

Found by Copilot on PR #26. A failed write leaves model_state.dirty set — deliberately, so the next frame retries — and the automatic trigger runs after every frame. A save frame therefore attempted the same write twice: extra I/O on a permanent failure, and on a transient one something worse, because the answer is composed from the first attempt, so the client is told SaveFailed about a document that is now on disk.

The fix is a per-frame question rather than a per-document one, and that is the right shape precisely because the automatic write exists for edits nobody asked to save; one that was asked for has already been answered.

The fixture is a Storage backend whose writes always fail and that counts them. Counting is the point: "it was refused" is true whether the write was attempted once or twice, so a test asserting only the refusal would pass against the bug. Failing is the point too: a successful save clears dirty, so the redundant second attempt never happens and the bug is invisible from the happy path.

a_key_resolved_on_the_host_moves_state_no_client_can_hear

Why the Key arm answers nothing, demonstrated rather than asserted in prose.

A worker can call reduce_key — it holds the authoritative App, which is the thing a socket server lacks. What neither has is a way to tell a client that the host's own ViewState moved: a client's slice advances only by folding Commands, and resolving a keypress produces none. So the two slices diverge, and ClientSession::viewport goes on reading the mirror's cursor, which means the grid does not even follow. That is improvise-bpq2's real cost, and it is a ticket rather than plumbing. The test asserts all three: the authoritative cursor moved, the mirror did not, and nothing reduce_key emits would let a client catch up.

---

improvise-worker-server/src/vfs.rs

an_entry_that_holds_no_document_is_seeded_over

The first browser run of the deployed page failed here, and no host test could see it: attach(create: true) leaves a zero-byte entry behind, documents listed it, and open therefore took the seed as already applied and read an empty file. The precondition is asserted before the act, because a test that only opens cannot tell "the seed landed" from "there was nothing in the way". The rule it pins is the one gotcha 45 states for the index: what is indexed is a document, and an entry nobody has written bytes to is not one.

This entry exists because the test cites this file and --check-evidence now requires that (improvise-lyyc); it was written from the test, so read the test first if the two ever disagree.

---

improvise-ws-server

distinct_stems_both_open

doctrine(check_the_checker) for colliding_stems_are_fatal: inject the fault that test rules out — distinct stems — and both documents must open. Otherwise an open_all that failed on every second file would pass the collision test.

a_bystander_on_the_same_document_is_projected_the_edit

doctrine(check_the_checker) for an_edit_is_projected_only_to_the_edited_documents_clients: put the bystander on the same document and the assertion must flip. Without it, an isolation test that passed because nobody is ever projected anything looks identical.

the_other_document_would_also_have_a_cursor_to_invalidate

doctrine(check_the_checker) for a_broadcast_does_not_cross_a_document_boundary. The fault to rule out is the other document being incapable of producing the broadcast at all — then a server-wide relay would be silent over there for the wrong reason and the isolation test would pass without proving isolation. So the checker drives the same TransposeAxes against beta and asserts it does produce a ResetCursor there; beta's silence in the isolation test is the routing and nothing else.

Both tests moved from Command::SwitchView to ModelCommand::TransposeAxes with improvise-jytm: a view switch is now addressed to one session and relays nothing, so it can no longer carry an isolation test. ResetCursor is the surviving Broadcast::ToAll.

a_load_that_fails_rebases_nobody

doctrine(check_the_checker) for a_rebase_stops_at_the_document_boundary: inject a load that cannot happen. The generation does not move, so nobody is rebased — which is also what a routing bug that sent Snapshot to nobody would look like, so the rebase test needs this one beside it to mean anything.

a_reopened_document_would_have_lost_the_edit_and_the_basis

doctrine(check_the_checker) for the_last_session_leaving_does_not_close_the_document: inject the eviction — a document freshly opened from the same fixture, which is exactly what closing on last-disconnect would hand the next client. Both assertions in the lifecycle test fail against it, so neither passes for a reason other than the document having stayed put.

a_rebase_stops_at_the_document_boundary

Fixture note, and it is gotcha 39's warning: the swapped-in document keeps the same active view name and changes only its shape. A rename would make apply_model broadcast a SwitchView, the client would fold it, and the stale cursor would then be read under a key nothing has written — right by accident, with the bug invisible.

a_client_on_a_socket_is_seeded_and_gets_its_edit_back

(crates/improvise-ws-server/tests/socket.rs, and its neighbours in that file.) Everything the socket test asserts is already asserted in host.rs without a socket, and deliberately so: its subject is the shell, not the decisions. It earns its place by covering what the unit tests structurally cannot — the handshake rule, JSON framing in both directions, the routing from a SessionId back to the connection it came from, and the one fact that lives only in a URL: which document the connection asked for. If it ever starts being the place a behaviour is pinned, that behaviour belongs in host.rs or registry.rs.

Two disciplines inside it are load-bearing rather than stylistic. The write is composed from the surrogate the server projected (ADR 002) — a CellKey there would be the test knowing something a browser does not — and the basis is composed from what the server published, because a basis the test built itself would be a client claiming to have seen something it was never sent.

---

improvise-wasm-client/src/keys.rs

text_entry_modes (a fixture, not a test)

Not a test — a fixture, and its limitation is the evidence. The comment here used to claim a new mode "shows up as a missing line rather than as untested behaviour". It does not: this is a hand-written list and nothing checks it against AppMode, so a new text-entry mode is simply absent and silently uncovered — which is what happened to save_prompt (improvise-lae) until it was added by hand. There is a second hand-written copy in the command crate's keymap::tests::text_entry_modes_with_exits. Deriving both from one place is filed, not done.

a_modified_character_now_types_because_the_fallback_is_the_shared_one

The old classifier sent a modified character upstream in a text-entry mode, because the host's AnyChar fallback matches under any modifier and a hand-written rule could only safely be a subset of it. Reading the same table removes the question: Ctrl-x falls through to AnyChar here exactly as it does on the host.

search_typing_writes_the_query_and_not_a_buffer

Search typing resolves on the client for the first time, and only because the keymap is shared: SearchMode binds append-char ["search"], and the name "search" is ViewState::search_query rather than an entry in buffers (improvise-gdl). The old classifier sent every search key upstream into an empty vec. The negative half of the test matters too: Esc stays upstream, because exit-search-mode owns the query and is the host's.

the_command_names_that_still_need_the_host_are_these

The command names this client cannot execute, one by one, so that closing one of these gaps has to come here and say so. This replaced a list of keys, and that is the whole gain of sharing the keymap: a rebinding no longer invalidates the list, and a new binding for an already-executable command works in a browser with no change to this crate. Each entry is driven through the key that reaches it, because a name that is not bound anywhere would otherwise sit in the list forever looking like a gap.

a_prompt_this_client_cannot_commit_is_never_entered

The refusal list above is only half the property. Upstream says the key produced no Command; it does not say the client stayed put, and the bug being guarded is precisely entering a room with no exit.

Found by Copilot on PR #27. Without strands_the_user, Ctrl-W resolved enter-mode save-prompt locally — ChangeMode(SavePrompt), a perfectly good Command — and the user then typed a path into a prompt whose Enter goes nowhere. Ctrl-E did the same into ExportPrompt and had done since before that branch.

The negative arm has two halves, and both are needed. Half one: a mode that is not refused is still entered — the half that goes through strands_the_user, so the only thing that can fail when the predicate degenerates to "refuse everything". ? is honest here where : was not: Help has no commit at all, so nothing a user types into it can be swallowed, and Esc closes it locally. (Its page keys are upstream, which makes page navigation inert — but inert navigation loses no work, which is the line the predicate draws.) Half two: the property is about finishing, not entering, so something has to press Enter and observe. The first version of this test asserted only that : entered its mode, and : is itself a dead room — so that arm was certifying the very behaviour it existed to rule out.

the_command_line_cannot_be_committed_by_this_client

The evidence behind listing CommandMode in strands_the_user, rather than the assertion that it is listed. : opens locally and typing appends locally, but Enter is [execute-command, clear-buffer] and step has no execute-command arm — so the whole sequence fails to resolve, Host::handle drops the frame, and every ex-command behind : is inert. That is what makes refusing the mode cost no working surface. When improvise-e24v gives this client execute-command, this is the test that should start failing, and the CommandMode arm of strands_the_user is what it points at.

a_commit_in_the_last_cell_exits_editing_instead_of_advancing

At the bottom-right corner EnterAdvance returns AbortChain, so the re-entry is skipped and the commit leaves the user in normal mode. That abort is a fact about the host's effect chain and it has to be mirrored, or the browser would sit in an editor on a cell the terminal has left. The fixture is a one-by-one grid, so the only cell is the corner.

a_move_that_goes_nowhere_follows_the_command_it_mirrors

Which widgets say nothing about a move that goes nowhere is not a rule of keys.rs — it is whatever the Cmd being mirrored does, and the three differ: Move emits even when it clamps, MovePanelCursor returns nothing when the cursor does not move, MoveTileCursor emits regardless. The grid arm carries its own check-the-checker inline (a j that does move), so "emits when clamped" cannot pass against a fixture that is simply inert.

i_on_an_aggregate_declines_out_loud

i on an aggregate must not go upstream: Host::handle answers a Key frame with an empty vec, so that would be a keypress the user sees do nothing at all (doctrine(an_upstream_key_is_a_black_hole)).

enter_commits_the_cell_advances_and_re_enters_editing

Enter in Editing is [commit-cell-edit editing, clear-buffer edit], and every part of that sequence shows up in what the client composes — including the trailing clear that empties the buffer EnterEditAtCursor has just seeded. That ordering looks wrong and is exactly what the TUI does; mirroring it line for line is the contract.

---

improvise-wasm-client — lib, socket, state, render

a_client_with_no_basis_composes_nothing

The fourth None, and the one ADR 001 adds: a client that has not been told the document's basis has nothing truthful to say about what it composed against, so it composes nothing. That is the property that makes the basis check unforgeable from a browser — BasisCache::claim is the only constructor, and it withholds.

The other three None shapes — an aggregate, id: None, and a position outside the grid — are pinned against the same composition in socket.rs's typing_into_a_cell_that_is_not_a_record_composes_nothing. They were asserted twice, once against each of two compositions, until improvise-r4lo left only one.

a_refused_batch_is_kept_as_a_rejection_and_not_only_as_a_sentence

A refused batch must reach the person who composed it, and it must reach them as more than a sentence. ADR 001 makes rejection a normal outcome, and the obligation that comes with it is that the client keeps the typing and can re-compose. Force needs the Rejection itself — RecordGone cannot be forced at all where RecordMoved can — so collapsing it into status_msg would throw away the input to the very feature rejection exists to enable. Both halves are asserted, because setting the string alone is the plausible half-fix, and the revision bump is asserted too: a renderer polls the revision, and a rejection it cannot see is a rejection it cannot draw.

every_rejection_message_says_the_edit_did_not_land

Found by the PR #12 Copilot review: DocumentReplaced read "the document was replaced — reloading", and nothing in fold_frame reloads anything. A message that names an action the code does not take is worse than a vague one, because the user waits for it. The per-variant wording still differs — the classes are different things to be told — but the one fact they share is the one the ADR guarantees, so it is asserted over all of them rather than one at a time.

a_typed_string_is_classified_as_the_host_classifies_it

The three-way split, matching commit_regular_cell_value: a number is a number, anything else is text, and empty clears rather than writing an empty string. This test states an obligation it does not discharge: it asserts the three outcomes by hand rather than comparing with the host's function, so the two copies could drift and stay green. See context/code/clients.md for why the duplication exists and what the real fix is.

a_cell_projection_that_overtakes_its_labels_is_lost

Gotcha 33, carried across this crate's dispatch. The protocol crate pins the drop inside GridCache::apply; what is this crate's is that nothing between the socket and that cache buffers, sorts or retries — so the same early Cells is still lost after routing. The second half of the test feeds the same three updates in frame-first order and requires them to land, so "everything is dropped" cannot pass it.

bootstrapping_from_a_compaction_lands_where_the_stream_lands

doctrine(fold_tests_must_test_order_not_the_axiom): a client that bootstraps from a compaction of the host's state must end up where a client that folded the whole stream is. The seed is the host's current state expressed as projections, not the head of the history.

the_selection_is_placed_by_subtracting_the_scroll_offset

(render.rs.) The conversion that looks right until the first scroll: the grid is viewport-indexed, the cursor is not. The offsets in the fixture are nonzero and unequal, which is what separates "reconciles" from "ignores the offset" and from "swaps the two offsets".

column_groups_coalesce_by_name_as_the_tui_does

(render.rs.) The run boundary must be the name alone, because that is what src/ui/grid.rs uses (group_name != prev_group) and the two ends must not disagree about where a span begins. Collapse is category-scoped, so two adjacent groups from different categories may legally share a name and differ in it. Keying the run on the pair would start a second run — a second indicator the TUI suppresses — which is a front-end divergence of exactly the kind improvise-anr9 exists to remove (raised by Copilot on PR #23).

a_keyboard_edit_in_progress_is_part_of_the_render_model

(render.rs.) A keyboard edit has to be visible, and what is visible is decided in Rust rather than in the page. The failure this rules out is quiet: a client that resolved i locally would change its mode label, put the typing into buffers["edit"], and draw the cell's old value the whole time — so the user sees a keystroke do nothing, types over it, and commits something they never read. None outside an editing mode is the other half: a stale buffer must not draw an editor that is not open.

---

improvise-wasm-client/tests/browser_round_trip.rs

The file's scope is improvise-1ey's, quoted: "open an existing document server-side, view it in the browser, type a number into a cell, see the server value update and the projection arrive with the new value." Everything in that sentence except the DOM is Rust on both sides, so the test drives the whole of it: a real Host over an authoritative App, and a real Client reached only through the string calls the page makes. The socket is the one thing left out, and it is covered by improvise-ws-server's own tests/socket.rs; what this adds is the half that crate cannot reach — that the browser client seeds, renders, composes and folds correctly against it.

The discipline that makes it evidence rather than decoration: the client is touched only through Client::viewport, Client::on_frame, Client::render_model and Client::typed_cell — strings in and out — and it learns the cell to write from its own render model, never from the fixture. A CellKey anywhere in it would be the test knowing something a browser does not (ADR 002).

a_grouped_row_axis_does_not_shift_the_write

A group header is a row of the render model and not a row of the grid, and a write composed against the wrong one lands on a different record — silently, because both are usize. FirstEditable therefore returns two numbers.

A fixture with no groups makes them coincide, which is exactly how an earlier version of the first_editable helper handed a visual index to typed_cell and passed (Copilot, PR #23). This test is the fixture the main round trip cannot be: a Coastal header sits between the two rows, so for the second row visual_row and data_row differ. Injecting the confusion — passing at.visual_row to typed_cell — leaves East unwritten. Note the ordering of the fixture is load-bearing: West comes first and ungrouped, because a header before the first row is dropped by AxisFrame::body_from and the two coordinates would coincide again.

a_commit_keypress_is_one_mutation_among_view_commands_and_is_accepted

improvise-955n: the one real producer of a multi-command frame must still be accepted. CheckedBatch::against answers a frame's basis before applying any of it, and every mutation answers for its own records. Getting that check right is the easy half; the expensive half is not tightening it until the browser stops working. A commit keypress is exactly the shape at risk — one SetCell plus the mode change, the scroll offsets and the re-seeded buffer around it — and it is produced by keys.rs::commit, which no test in the command crate can reach.

So it drives a real keypress through a real Host and asserts the frame is accepted and lands: ServerFrame::Rejected anywhere in the answer, or an unchanged cell, is the regression. Asserting only "no rejection" would pass against a host that dropped the frame on the floor. The "exactly one mutation" assertion is a characterization of what keys::commit emits, not a protocol constraint — a frame may carry more than one — so that if commit ever started batching two, the test would be exercising something else and should be re-read rather than silently re-scoped. And the fixture types 888 after i has seeded the buffer, so the assertion is on the appended value: 888 alone would also be produced by a client that ignored the seed.

---

improvise-wasm-client/tests/lockstep.rs

src/keys.rs decides a small set of keypresses without the document. The claim that makes that safe is not "the rule looks the same" but the two ends land in the same ViewState, and that is checkable: the host's reduce_key runs the real keymap, registry and effect pipeline against an authoritative App, and ViewState is the protocol's own type on both sides. So every local outcome is driven through both and compared.

This is why the command crate is a dev-dependency. Dev-dependencies are not built for --target wasm32-unknown-unknown, so nothing the host owns reaches the browser bundle.

a_locally_typed_character_lands_where_the_host_would_put_it

Driving one mode would say nothing about the others (doctrine(one_arm_of_a_symmetric_rule_is_evidence_about_that_arm_only)), so every text-entry mode is driven, and each with a non-empty buffer so an append that silently replaced the buffer would be visible.

a_forwarded_key_reaches_the_host_unchanged

An unresolvable key must reach the host as a keypress, and what the host then does to its copy of this client's view slice is what the client will be told. Pinned as the shape the transport owes: the message carries the code and modifiers, and they survive the round trip. Enter rather than an arrow key, because since improvise-bpq2 the arrows resolve locally and enter-advance is one of the movements deliberately left upstream — it aborts the rest of its batch at the bottom-right corner, which is a fact about the host's effect chain and not a cursor position.

a_locally_resolved_cursor_move_lands_where_the_host_would_put_it

The headline claim for improvise-bpq2's first gap: a cursor key resolved on the client lands where the host would have put it — including the scroll that follows it, and including the clamp at the end of the grid.

The fixture is six rows in a three-row window, and the keys walk past the bottom of the window (so row_offset must move) and then past the bottom of the grid (so the clamp must hold). A client reading its bound off the row frame's length would stop at row 2 and never scroll; one that clamped against nothing would run off the end. Both are visible. Eight presses for six rows: the last three are the clamp.

The fixture's one column is deliberate. The two ends measure their windows differently: the host's visible_rows is term_height - 8 and its visible_cols is computed from column widths, while a browser announces both outright. term_height can be chosen to match the rows; nothing can be chosen to match the columns, so the fixture removes the question rather than guessing at an answer.

a_locally_resolved_panel_cursor_agrees_with_the_host

improvise-bpq2's second named gap, which turned out not to be one: the category panel's flattening depends on expanded_cats, but the derivation already lives in improvise_protocol::viewmodel and both ends call it (improvise-edp). So this is not two derivations agreeing by luck — it is one derivation, and the test says so by expanding a category, which changes the flattened length the cursor clamps against. A client that counted categories would stop several rows early.

the_buffer_i_seeds_is_the_value_the_host_would_seed

i seeds the edit buffer from the cell's display value, and the two ends must agree on what that is: the host reads App::display_value_at_cursor, the client reads the text the server projected into its GridCache. Those are two paths to one string, and this is the assertion that they are the same string.

entering_typing_and_cancelling_an_edit_agrees_with_the_host

Esc rather than Enter for the cancel arm, because it is a Binding::Sequence and so exercises the all-or-nothing rule: half of it — a cleared buffer in a mode the user has not left — is worse than none.

a_locally_committed_edit_leaves_both_ends_in_the_same_place

What is not compared is the document, and deliberately: the client answers with a Command::Model, which reduce_view drops, while reduce_key writes through the effect pipeline. The write's composition is asserted in keys.rs against typed_cell's own — the shared one — so what is left to prove here is the half a unit test cannot see, which is that the advance and the re-entry land in the same place.

client_ready_to_edit (a fixture, not a test)

The published basis a real client folds before it is allowed to compose a write (ADR 001). The tiers are the ones lockstep never checks — the host applies the keypress directly rather than the client's Command::Model — but BasisCache::claim withholds until it has something, so a client without one resolves no commit at all.

---

harness/ — the browser specs

These are Playwright tests, so the checker's --check-evidence pass (which scans Rust fn names) cannot see their names. They are recorded here under their exact test("…") titles anyway, because they are where the JavaScript evidence lives.

harness/tests/shell.spec.js — the file's own scope

The three assertions improvise-hwpi could not write. That ticket fixed four things and said of itself that the fixes were "as unverified as the bugs", because three of them are one-assertion tests that needed a browser. These are those three, plus the watchdog — which was found by reading, and only because someone went looking. Until this file, web/app.js and web/worker.js had never been rendered or run.

Two fixtures are load-bearing. NO_WEBSOCKET_HERE is a peer that accepts the TCP connection and then refuses the WebSocket upgrade — the harness's own static file server — deterministic where a closed port is not: a refused port's close timing is a property of the host's network stack, and on the GitHub runner it did not arrive inside the window. The page cannot tell the two apart and neither can web/app.js: in both cases the socket never opened. HANDSHAKE_TIMEOUT_MS restates web/app.js's own constant, because two tests have to outlast it and a number that silently disagreed with the page would make them pass for the wrong reason. logStatus records every distinct #status, not just the last one, because several of these tests are about a message being replaced, which the final value cannot see.

"a frame the client cannot fold says so on screen"

improvise-hwpi: on_frame returns a Result, which wasm-bindgen throws. Thrown in a bare listener it reached the devtools console and nothing else — the grid simply stopped updating with nothing on screen saying why. The fault is injected at the peer, not in the page — a mocked socket that answers the handshake with a frame the client cannot fold — so this exercises the real on_frame and the real catch.

"a peer that cannot be reached is named, and not called a disconnect"

improvise-hwpi: without an error listener, a connection that never opened left #status blank, and "the server is not running" read exactly like "still connecting". This test no longer says anything about the watchdog, and the paragraph below is why it never could. shell.arm runs only after await transport.ready, which resolves on open — so on a socket that never opens the watchdog is never armed at all, and denying its message here denies an unreachable event.

That sentence was already in this file, five lines above an assertion that contradicted it. PR #65 added the watchdog clause and edited this very paragraph, inserting "runFor(10s) advances the watchdog" immediately before the sentence saying it is never armed. Reverting PR #21's routing, or stripping fail() of its sawFrame(), both left that clause passing. So a PR whose subject was "a deleted guard went unnoticed" planted the same shape one level up: three injections, three distinct test names, and two of them proving nothing. What the test guards now is the naming — close on a socket that never opened must not read as "disconnected" (improvise-taxx) — which is the half injection 3 really does exercise.

The mechanism, so it cannot come back. outlastTheWatchdog now asks the page timesArmed() > 0 before jumping, and a watchdog denial re-added to this path fails by name. It asks ever armed rather than armed now: by the time the disconnect test jumps, a correct page has already disarmed — that is the property — so armed() would have denied the passing case. Building that guard is what surfaced the distinction, which no amount of reading had.

"a socket that opened and then dropped reads as disconnected, and stays that way"

The other arm, which must keep working when the first is fixed: a socket that really did open and then dropped IS a disconnect, and saying so is the whole reason close cannot simply be suppressed.

It runs past HANDSHAKE_TIMEOUT_MS on purpose — through page.clock, not through a real wait. On this arm the watchdog IS armed — armWatchdog runs after transport.ready resolves, i.e. on open — so "disconnected" is written while a timer is pending, and the only reason it survives is that close goes through setShellFailure, which clears it. That was argued in a comment and asserted nowhere, and the argument was got wrong from the outside: a bug report (improvise-xps8) claimed the timer fired 8s later and overwrote "disconnected" with "sent no document". It had been measured, honestly, but against a tree predating PR #21 — and the "confirmation" that it survived PR #21 simulated only that PR's opened flag and not its other half, routing BOTH close arms through setShellFailure. A simulated fix that is not the fix you named reproduces a bug the real code does not have, and reads exactly like a confirmation. The ticket was filed and closed invalid. Hence this assertion rather than another paragraph — proved discriminating by making setShellFailure skip its clearTimeout, which makes it fail. Same rule as doctrine(an_injected_fault_must_be_the_fault_you_named), one level up.

And it was lost a third time, by the PR that was arguing about exactly this. PR #61 split the browser tests into boundary contracts (Playwright) and unit tests (node --test), and merged these two tests into one that kept only the last-value assertions. shell.test.js's "a loud failure DISARMS the watchdog" covers createShell in isolation and cannot see whether app.js routes the close event through fail() rather than setShell() — which is the half PR #21 fixed and the half that keeps getting lost. Reverting both socket arms to setShell left the node suite 26/26 and Playwright 13/13 green. Restored under their original names, and re-proved with that exact revert: the two-arm revert and the close-arm-only revert each fail "…and stays that way", and dropping the opened flag fails "…the watchdog stays out of it". Three injections, three different tests, none of them the unit test.

And the helper guards its own premise. page.clock.runFor on a page where clock.install() was never called does nothing and throws nothing, so a test that forgot the install would assert "the watchdog never spoke" against a watchdog never given the chance — vacuous, and green. outlastTheWatchdog reads Date.now() inside the page either side of the jump and requires it to have moved. Demonstrated both ways: with the install removed the suite passed 6/6, and with the guard in place the same omission fails by name.

The window is single-homed, and that is the second half of the same finding. HANDSHAKE_TIMEOUT_MS lived twice — once in web/app.js, once in the spec — with a comment saying a silent disagreement "would pass for the wrong reason" and nothing checking it. Setting the spec's copy to 1000 against the page's 8000 made the whole suite green against the reverted routing: the jump landed inside the window, the watchdog had not yet fired, and the denial held vacuously. It is now exported from web/shell.js and imported by both, so the two cannot disagree; shrinking it in its one home still catches the routing revert, which is the demonstration that the guard did not go quiet.

The faked clock is what makes the restoration cheap without weakening it, and the injections are the proof of that too: if page.clock.runFor did not really advance the page's timers, a broken routing could not surface the watchdog's message and those injections would have passed. They failed. The test keeps the real page, the real socket, the real listeners and the real setTimeout call — only the passage of time is simulated, and 9 seconds of wall clock became 75 milliseconds.

The measurement that could not become a CI guard. Both of the above were once asserted as test.fail expected-failures and had to be removed: neither reproduced on the GitHub runner, where close does not follow error within the window. An expected-failure is green when the bug is present and red when it is absent, so one whose trigger is platform-dependent does not merely flake — it inverts CI's meaning, and it failed the build twice saying "expected to fail, but passed". The lesson stands even though the second bug did not: assert the PROPERTY THAT MUST HOLD, which is portable, rather than the fault, whose trigger is the host's network stack.

The first of the two, for the record, was real: the socket's close listener was unconditional, so on a connection that never opened it overwrote "cannot reach …" with "disconnected". FIXED by PR #21. An opened flag is the only discriminator — readyState at close time cannot tell the two apart, and neither can the CloseEvent: both cases are code 1006, wasClean: false.

"a peer that accepts and then says nothing trips the watchdog"

The first-frame watchdog, found by reading. The condition is one no per-transport check would catch: the peer accepted the connection and then said nothing. The mock accepts and never answers.

"the page draws the demo document out of the worker"

No ?ws=, so web/app.js spawns the in-page worker over OPFS: the whole application, with no server process. If this draws a grid, then worker.js, bindings.rs, OpfsFs, vfs::open and the seed fetch all ran.

"committing an edit sends one frame and shows the host's value"

A commit round-trips through the host, and what lands on screen is the host's value rather than the string that was typed. 20000 is typed and 20,000 asserted: the number format is applied by the host and relayed back, so a page that echoed the input would fail.

This is deliberately NOT named for improvise-hwpi's third fix (the closed re-entry guard in edit), which Copilot asked for on PR #24. That guard is not observable from the DOM, measured rather than assumed: with it removed, close still runs exactly twice, the frame is still sent exactly once, #grid still takes exactly two childList mutations, and the final text is identical. The only difference is one extra entry into repaint() that produces no output — because the second close is close(false), so it does not re-send, and everything else it does is idempotent. That is precisely why hwpi called it "harmless before, but only by accident". Counting repaint() entries would need a test hook inside web/app.js, which would be a page that knows it is being tested. So the test name says what is checked and this entry says what is not. What is observable is asserted: the editor is gone and did not come back, so no stray <input> is left behind and the host's value is not overwritten by the original text the second close writes before repainting.

"the harness can see a failure"

Check the checker, and it runs first: a green run against a worker that never started is the failure this repo has a doctrine about. run_canary drives the same reporting path every real check uses, and the spec asserts it is reported as a failure with its message intact.

"every check in the battery runs and passes"

The battery is asserted complete before any of it is believed: the report's names must equal EXPECTED exactly, so a build that dropped a check fails rather than passing with fewer.

"what OPFS held survives a reload, and a committed delete does not"

The one thing no in-page check can establish. A delete is visible immediately and lands in OPFS at the end of the batch — so "commit_deletes actually removed it" is only answered by a fresh page. This is also the storage half of improvise-bck's persistence criterion.

The opfs-contract checks (harness/opfs-contract/src/lib.rs)

• an_attached_but_unwritten_entry_is_not_a_document — attach must create the file to obtain a sync access handle for a document that does not exist yet, and that created file is zero bytes, which is NOT a document. Storage::list promises document names, so an attached-but-unwritten name must not be listed. Indexing it is exactly the improvise-9x6 browser failure: the seed was skipped as "already there" and load_from got an empty buffer. The check also opens a second instance, which shares no index, because the filter has to be in refresh and not only in the omission from attach — and then writes through the handle to show it is real and the name IS then a document.
• a_directory_entry_is_not_a_document — keys() yields DIRECTORIES as well as files, and getFileHandle on a directory rejects with TypeMismatchError. Treating that as "could not measure, so assume a document" would list an entry that can never be attached or read — the same picker bug the zero-byte filter removes (Copilot, PR #24). OpfsFs never creates a directory, so the harness makes one itself, and asserts a real file beside it IS listed — the precondition, so the check cannot pass by the directory never having been created, and evidence that keys() walked the root at all.
• refresh_walks_every_key_and_sorts_them — the hand-rolled keys() async-iterator walk in refresh is the least certain code in opfs.rs (improvise-xf1 named it). One entry could pass by accident; several, out of order, cannot. It wipes first, like every other check: a battery whose steps depend on the leftovers of the step before breaks when one is inserted, which is exactly what inserting the directory check did.
• read_and_write_are_absolute_at_offset_zero — FileSystemReadWriteOptions' at handling, the other thing xf1 called out. A write that appended instead of overwriting, or a read that started anywhere but 0, is invisible on a single short write and obvious across a long one followed by a short one.
• storage_contract_at_… — the point of the whole exercise. attach is hoisted out because acquiring a handle is the async half and Storage::write cannot await; the contract itself is the shared function, not a transcription of it.
• a_delete_is_visible_at_once_and_lands_on_commit — both halves, because either one alone would pass against a backend that got the timing exactly backwards.

a_locally_cycled_panel_focus_agrees_with_the_host

cycle-panel-focus is bound to Tab in Normal only: PanelKeymap's spine binds Tab to enter-mode normal inside every panel (gotcha 12), so the wrap arms of CyclePanelFocus — the ones that start from the focused panel — are unreachable by keypress. The test therefore asserts the one reachable path and says so, rather than looping three times and passing on a mode that never moved. The first draft did loop, and failed on step 1 with the mode back at Normal; that failure is the evidence for this paragraph.

a_locally_resolved_tile_axis_change_agrees_with_the_host

Both of TileAxisOp's names in one walk, because the command names itself off its axis field: r takes the Some arm (SetAxis) and Enter the None arm (CycleAxis), and a test that drove only one would leave a whole Cmd unmirrored. Injecting parse_axis("row") => Axis::Column fails it.

the_category_panel_bindings_agree_with_the_host

The fixture sits on a header row for Space/a and on an item row for Enter/d, and then on a header again for a second d. Both of FilterToItem's arms and both of DeleteCategoryAtCursor's arms are therefore reached. That is not decoration: the first version sat only on the item row, and injecting a wrong sentence into the category arm of delete_at_cat_cursor did not fail it. One fixture position, one arm — and a check that passes against an arm it never enters is the defect this repo keeps finding.

the_view_panel_bindings_agree_with_the_host

Two views in the fixture, and the cursor moved to 1 before Enter, because view_at_cursor reading .get(0) is the natural wrong implementation and a single-view fixture cannot tell it from the right one. Injecting .get(0) fails it.

It presses d as well, and that was added after the fact: the first version said "create, switch and delete" in its doc comment and pressed only n and Enter, so delete_view_at_cursor — whose only decision is the cursor step-back it makes away from the top of the list — was never run. The adversarial review of PR #50 deleted that step-back and the workspace stayed at 1322 passing. d is pressed at index 1 so the decision is reached, and both_ends now compares every cursor (see below), without which the deletion would still be invisible.

a_locally_committed_minibuffer_agrees_with_the_host

commit-buffer for all three kinds, driven as keystrokes so the TextEntry spine's clear-buffer weld is part of what is compared. CommitKind::Item carries its category, resolved from AppMode::ItemAdd — so the mode the test starts in is load-bearing, not scene-setting. Injecting AddCategory in place of AddItem fails it on the document comparison.

Formula was missing from the first version, and it is the kind that matters most: it is the only one whose on_commit() is Some, so a test of the other two cannot see the mode a commit returns to. The review of PR #50 broke both CommitKind::status's and on_commit's Formula arms and nothing failed. Its text is seeded rather than typed, and valid, for the reason the next entry gives.

a_formula_the_client_cannot_parse_diverges_on_the_status_line

The one thing a client cannot mirror about commit-buffer formula, found by widening the test above and kept as a pinned divergence rather than a fix (improvise-cl7y).

CommitBuffer emits its optimistic status first and the add effect last, so on the host a parse failure overwrites "Formula added" with "Formula error: …" (improvise-6t3). The client reproduces the command line for line — which is right — but it cannot parse, so it folds "Formula added" and stops. The user sees a browser confidently report a formula it did not add.

This asserts both sides, so a fix has to come here and change it. That is the difference between a pinned divergence and a comment: a_locally_committed _minibuffer_agrees_with_the_host would otherwise have to use a valid formula forever with no record of why.

panel_focus_cycles_from_the_focused_panel_not_the_first

CyclePanelFocus's wrap arms, driven directly rather than through a key. PanelKeymap's spine binds Tab to enter-mode normal inside every panel (gotcha 12), so no keypress reaches them — which is why the lockstep test asserts only the reachable path and why breaking the start index survived the review's injection pass. Mirroring a Cmd faithfully includes the arms the keymap cannot reach today; testing them takes a direct call.

The fixture leaves the category panel closed, so "the next open one" and "the next one" give different answers and a mirror that walked the array blindly would fail.

a_locally_resolved_clear_and_paste_agree_with_the_host

The two writes ADR 002 lets a thin client name. Note the fixture's cell key has three coordinates: Workbook::add_category puts a new category on Axis::Column, so Product is part of the cell's address and a two-coordinate key names a cell the grid never shows. The first version asserted on the two-coordinate key, and passed the per-key comparisons while asserting against a cell nothing had touched.

walking_off_the_end_of_the_help_pages_agrees_with_the_host

The bug this was written to demonstrate: effect::HelpPageNext clamps and HelpPagePrev saturates, while reduce_view's Command::HelpPage arm wrapped. Two derivations of one fact, in disagreement, invisible because h/l in the help overlay were upstream keys and no client had ever sent the command. It failed on the first press past the end — client 0, host 4 — and the wire was changed to match the effect. Whether both should wrap instead is improvise-trd3.

"? opens help, and its rows carry the keys and the words, not empty frames"

This entry was demoted to prose as Retired when PR #61 deleted the spec. PR #72 restored the coverage under a new name, so the claim is live again and the heading now names the test that exists. What follows is the original evidence; improvise-igxp's stronger assertions are recorded separately below.

improvise-ktv1's acceptance in one place: a browser shows help. ? had entered AppMode::Help since the keymap was shared, and nothing appeared — the mode changed and the page had no overlay, which is worse than a key that does nothing because the user thinks they missed it.

It asserts the shape, not merely that something is visible: the active tab is the shared module's page title (Welcome, then Navigation after l, which also exercises Command::HelpPage folding on the client), and the body has a key row. Two faults were injected and each failed it. Dropping the paintHelp(model) call fails toBeVisible; removing the mode != Help guard in help_rows — so the overlay is never empty and therefore never hidden — fails toBeHidden. The second is the one worth having: an overlay that is always open passes any check that only ever opens it.

It runs against the assembled site like every other test here, so it covers render.rs, the serialized model, web/app.js and the CSS together.

It was gone for a release, and that is why the entry reads oddly. 36ade35 deleted it with the rest of harness/tests/widgets.spec.js and nothing replaced it, so the heading promised coverage that did not exist -- exactly the cost improvise-5ray names, and invisible because the evidence checker then read only ### headings and only Rust names. PR #69 taught it to see both; PR #72 restored the coverage under the current name, with the stronger content assertions improvise-igxp asked for.

The injections above are the original two and still describe the property. The present test is harness/tests/help.spec.js, and its own entry below records what igxp added: the rows are read as dt/dd pairs and asserted as text, so blanking keys.textContent fails it where toBeVisible passed.

the_shipped_demo_seeds_a_worker_whose_raw_cells_are_settable

improvise-ir7l renamed this from ..._whose_every_cell_is_settable and narrowed what it claims. The old loop called MainThread::cell — which panics on anything but a stored cell — over every column including Profit, which web/demo.improv defines as Revenue - Cost. It passed only because a formula target projected CellId::Record, which is the bug the ticket names: a test whose name was false for a third of the grid it walked.

It now walks the two raw columns and asserts separately that the Profit column is CellId::Derived, so it fails if either half moves. That second assertion is what makes the narrowing honest rather than a retreat — dropping the column would have left the page free to offer it again with nothing noticing.

the_page_keys_turn_the_odometer_as_the_command_does

improvise-p1ym. GridCache::page_coords carried (category, selected item) and nothing else, so [/] resolved to a command name the client held but could not compose an argument for. They reached Host::handle, which answers an empty vec — doctrine(an_upstream_key_is_a_black_hole) — so an independent smoke test found them inert against the live page, where Quarter sits on the page axis precisely because paging is a thing a visitor tries.

The test asserts the shape composed, not that something resolved: two page axes, the least significant at Q4, so one press must both wrap Quarter and carry into Year. A resolver that moved only the first axis, or carried the wrong way, fails it.

a_filter_axis_is_projected_but_not_cycled

The gotcha-27 arm. Page and Filter both constrain which records are visible, and GridLayout::page_coords is deliberately filtering_cats() (Page ∪ Filter) because the layout does not care which the user can navigate. The projection copied that verbatim, so a client handed the list would have tried to cycle a drill's fixed coordinate.

PageAxis::items is Some only for Axis::Page, so the difference is in the type rather than in a rule each client remembers. The test adds a Filter entry to a client that is otherwise paging normally and asserts the two Page axes still move while the Filter one does not — an assertion that only the Filter axis is skipped, not that paging stopped.

a_locally_resolved_page_turn_lands_where_the_host_would_put_it

The lockstep claim, and the first version of it was vacuous, which is worth recording because it looked exactly right. It rebuilt the client's cache from the host after every press and then compared the client's cache against that same host's document — two readings of one value. Reversing the odometer's significance in page_cycle left it green.

It now drives two independent documents: one Host fed the commands the client composed, one App fed the same keypress through reduce_key, compared on View::page_selection — the document, never a projection. Proved discriminating by that same injection (for i in (0..axes.len()).rev() → for i in 0..axes.len()), which now reports Q2 against Q3. The assert_ne! against a fresh fixture is the second half: without it, a resolver that emitted nothing at all would pass by moving neither.

harness/tests/widgets.spec.js — the file's own scope

Both files were deleted by PR #61, which moved the pointer's and the widgets' browser halves into harness/tests/contract.spec.js and the rest into node --test web/tests. What follows is the history of how these assertions were arrived at; the assertions themselves now live there.

The file is gone; its subject is not. All four widgets it named were one failure at one boundary — a RenderModel field with no element painting it — and that is now asserted once, from both sides, by web/tests/render_surface.test.js and harness/tests/contract.spec.js. What is not carried over is each key's meaning, which improvise_protocol::resolve decides and tests. Everything below is the history of the bug, and still true.

A user reported three things as broken: "I can't expand categories, and the Tile + View UIs don't work." None of the three was a regression. Driving the assembled site under Chromium separated them, and the separation is the point: two of the three had every layer but the last one, and the layer they were missing was not the same in each case.

Category expand already worked, by keyboard. Shift-C, j, Enter folds Command::ToggleCatExpand client-side and the items appear. What does not work is the mouse: categoryList builds plain <li>s with no listener, so a click on the triangle does nothing at all. That half is improvise-7ybz, and it is a product decision about the whole page's pointer model rather than a defect in an implemented feature — #grid offers a click only on an editable cell, so there is no click-to-select either.

The tile bar and the view panel had the cache, the keymap, the resolver and the host round trip, and no DOM. Before the fix, render_state() in the browser carried five TileBarCache entries and both ViewListCache views; Shift-T entered TileSelect and ArrowRight moved tile_cat_idx; r/c/p reached the host and really did move a category between axes. RenderModel simply had no field for either, and web/index.html had no element. So the keys worked and the user was aiming them at nothing — which reads exactly like "the Tile UI doesn't work". The formula panel was the third of Panel::ALL in the same state and is fixed by the same mechanism.

The fault injection was the unfixed bundle itself. Run against the tree at a3bef6e, the category test passes and the other four fail — #tiles, #views and #formulas resolve to zero elements. That is the evidence the four tests are discriminating, and it is why the category test stays: it is the control that says the harness really is driving the keyboard.

Two assertions in the first draft were wrong, and both corrections are worth keeping. Axis::short_label() is three columns, so a Page tile reads Quarter Pag, not Quarter Page — a test asserting the long spelling would have forced the page to invent a label instead of echoing Axis's own. And switching views leaves the panel open: switch-view-at-cursor returns to Normal and never closes the panel, exactly as src/draw.rs keeps drawing it off view_panel_open alone. Asserting it hidden would have pinned the browser to behaviour the TUI does not have.

The gating rule itself — an empty list is what says a panel is closed, the same rule help follows — is asserted in Rust as well, by a_closed_panel_projects_no_rows_and_an_open_one_does and the_tile_bar_is_always_present_and_only_its_cursor_is_modal, because a browser test cannot distinguish "closed" from "the cache is empty" and those two tests fill the caches first.

What these tests do not cover: the pointer (improvise-7ybz), and the inconsistency that #views/#formulas honour their open flags while #categories is drawn unconditionally because app.js has never read category_panel_open (improvise-wsaw).

One assertion was added after the first green run and is worth naming: the tile test originally asserted only that the tile label changed to Product Col. That is the bar reporting itself, which is exactly the shape of test this repo keeps catching — it would pass against a tile bar that displayed an axis the document had not taken. It now also asserts the grid reshaped: Espresso moves from a tbody row header to a thead column header. .first() is needed there because Product then shares the column axis with _Measure, so the label appears once per header level — which is itself a small confirmation that gotcha 44's multi-level frame reaches the browser.

Three review findings, applied. The second is the one worth carrying.

The page had two spellings of the same triangle, inside the file that declares it has one. indicator() carries the comment "only this spelling is the page's (gotcha 26)" — singular — and categoryList did not call it: it inlined U+25B8/U+25BE (the SMALL triangles) where indicator(), the page's own grid group headers and src/ui/category_panel.rs all draw U+25B6/U+25BC. So the browser's category panel disagreed with the TUI's and with its own grid. categoryList now calls indicator(!row.expanded).

And the first version of this spec pinned the wrong spelling. It asserted /▸ Product/ and ▾ — the divergent pair — so the obvious cure, which the file's own comment implies should already be in place, would have failed a test this work added. That is this repo's characteristic defect exactly: not a wrong line, a test that cements a state the doctrine says is wrong, and it makes the cure more expensive the longer it sits. The spec now asserts ▶/▼, and the change was proved discriminating by running it against the pre-fix bundle, where it fails with Received string: "▸ Product (4) R".

Note what this does not settle: whether glyphs should move to the protocol the way short_label() did. That is improvise-h04z, not answered here — what is fixed is the page contradicting itself. viewRow still spells "▶ " as a literal duplicating src/ui/view_panel.rs:62; the two agree today, which is precisely the state categoryList was in before it drifted.

And the drift was already spreading, which is the evidence that ticket needs. harness/tests/pointer.spec.js, written on a different branch, had independently grown the same ▸/▾ assertions — so the corrected indicator() broke it too. Three files converging on a spelling nothing compares is the failure design-principles §5 predicts, observed rather than argued, and it is what answers "is one duplicated literal worth a protocol change" with data instead of doctrine.

el.tiles.hidden was a no-op, removed with its comment. #tiles declares display: flex, an author-origin rule that beats the UA sheet's [hidden] { display: none } at any specificity, so the guard never hid anything and "an empty tile list draws nothing at all" was false. #views, #formulas and #help declare no display and so are genuinely hidden by the attribute. Worth knowing before anyone "fixes" it: because #tiles is always laid out, its height never changes, so it feeds nothing back into the ResizeObserver — restoring the guard would introduce exactly the first-paint height change the observer argument assumes away.

The ResizeObserver loop is no longer "argued, not tested", and the proof is worth more than the measurement. It was measured: 820 combinations — four panel states (none / views / formulas / tile-select) × heights 360-440 in 2px steps × five widths straddling the COL_PX = 110 boundary, each counting #grid child replacements in a 500ms quiet window. Every size settled; nothing repainted twice. But the reason is structural, so the measurement is a check on it rather than the evidence itself: the frameCost dependency graph is acyclic. frameCost.cols is row_levels, the number of row-axis header levels, which does not depend on how many rows are projected. frameCost.rows derives from col_levels.length and col_groups, which depend on the projected column window, which depends on width and frameCost.cols. So cols → rows, and nothing depends on rows. There is no cycle to oscillate. A change that made either term depend on the projected row count would create one, and that — not the pixel arithmetic — is the thing to check.

A harness port collision can make a run test somebody else's tree, silently. playwright.config.js hard-coded 8099 with reuseExistingServer: true, so a python3 -m http.server left by another worktree is adopted, and the run then exercises that checkout with no warning. The port is now IMPROVISE_HARNESS_PORT, defaulting to 8099 so CI is unchanged. The tell is a result that disagrees with the file you just read: check lsof -a -p <pid> -d cwd on the listener before believing it.

It fires in both directions, and the dangerous one is the false PASS. Two agents hit it in one session. One got a false negative — a glyph fix reported absent, because the adopted tree did not have it — which is merely confusing, since a failure sends you looking. The other got widgets.spec.js reporting 5 passed against a tree it had content-verified as having no #tiles and no paintTiles at all, which is impossible and was caught only because that agent knew what the tree contained and refused to believe the number. A false pass prompts nobody. That is what makes a hard-coded port with reuseExistingServer a correctness bug rather than an inconvenience, and it is the same rule as the rest of this file: a green result is evidence only once you know what it measured.

a_click_focuses_the_panel_moves_its_cursor_and_activates_the_row

improvise-7ybz's whole difficulty in one assertion, and the reason the click resolvers take an index rather than reading the cursor.

A click means three things at once — focus the panel, move its cursor to the row under the pointer, activate that row — and the third is resolved in the same pure call as the first two, before any of them has been folded. So filter_to_item_at(state, index) must be asked about index; asking filter_to_item(state) reads view.cat_panel_cursor, which is still wherever the keyboard last left it. That is why cat_tree_entry, toggle_cat_expand, filter_to_item and tile_axis each gained an _at twin and the cursor-reading form became a one-line call of it: one definition, two entry points.

Injected fault, run: commands.extend(filter_to_item_at(state, index)…) → filter_to_item(state). The test fails with ToggleCatExpand("Region") against ToggleCatExpand("Product") — the panel cursor lands on the row clicked while the expansion happens to the row that was selected before, which is the silent half. The fixture therefore has two categories and clicks the second: with one category, or with a click on the row already under the cursor, the bug is invisible.

The sibling a_click_in_an_already_focused_panel_only_moves_and_activates pins the other half: focus emits only what is not already true, so a click inside the focused panel is not a mode change on every click. Without it, "always emit SetPanelOpen + ChangeMode" passes the first test.

a_cell_click_is_absolute_even_though_the_page_paints_a_window

The pointer's version of the_selection_is_placed_by_subtracting_the_scroll_offset, and it fails the same way: GridCache is viewport-indexed, ViewState::selected is absolute, so a click at painted (2,1) under offsets (12,3) is (14,4). Offsets are nonzero and unequal for the same reason as its sibling — equal offsets cannot separate "reconciles" from "swaps the two". The second half asserts a click past the grid's extent resolves to nothing, which is what stops a click on the padding below the last row selecting a cell that does not exist.

a_click_past_the_last_row_resolves_to_nothing

doctrine(check_the_checker) for the two above: the empty-answer path. Without it, a click that returned Vec::new() unconditionally would pass every "resolves to nothing" expectation while failing silently everywhere else — so this one is only meaningful because its neighbours assert non-empty answers.

harness/tests/pointer.spec.js — the file's own scope

Both files were deleted by PR #61, which moved the pointer's and the widgets' browser halves into harness/tests/contract.spec.js and the rest into node --test web/tests. What follows is the history of how these assertions were arrived at; the assertions themselves now live there.

The file is gone; one test carries it. contract.spec.js's "each clickable surface is wired to its own index" keeps what only a browser can say — the handler is on the element, it passes that element's index, and the answer is painted — against three surfaces. What each click means is improvise_protocol::resolve's, and its tests are named below. The six tests' injection stands as recorded.

The user's ruling on improvise-7ybz ("build it — one entry point per widget") and improvise-wsaw ("honour the flag"), executed in a real browser.

Six tests, and all six fail against the bundle built immediately before them — the tree that already had the three widgets drawn (PR #55) but no click handlers and no category_panel_open read. That is the injection: the sidebar is visible when it should be hidden, and every click() resolves to a <li> that has no listener, so nothing moves. The category test is the sharpest, because the element it clicks exists and looks interactive in the unfixed tree — which is exactly what the user hit.

Two properties here that the Rust tests structurally cannot reach. The pointer and the keyboard are one cursor: the keyboard continues from where the pointer left the cursor clicks a cell, closes the editor, presses ArrowLeft, and requires the move to start from the clicked cell — if the click had only opened an editor (the pre-fix behaviour) the arrow would move from the origin instead. And the tile click is asserted against the grid, not only against its own label: Espresso must appear as a thead header, because a tile bar reporting an axis the document did not take is the failure shape this repo keeps finding.

One fixture note worth keeping: openPanelThenLeave opens the panel with Shift-C and then presses Escape, which returns to Normal without closing the panel (PanelKeymap's Esc is enter-mode normal, nothing more). That is the only state in which the "focus" third of the click is observable — from a freshly opened panel the mode is already CategoryPanel and the assertion would pass without the focus commands existing at all.

harness/tests/drill.spec.js — the file's own scope

The fourth widget the user reported, and the one with a different answer from the other three. The tile bar, view panel and formula panel were each one RenderModel field short — cheap. Drill is not: there is no wire vocabulary for it, which is improvise-gd28, and these tests document the refusal rather than pretending the gap is a bug to be fixed here.

Where it stops, by layer. Everything below the command exists and was verified in the browser, not read: project::grid_of emits CellId::Aggregate, the client receives it ({"Aggregate":"750ab1f5ffa96d5e…"} in render_state), render.rs::editable correctly answers false for it, and resolve.rs reaches the aggregate arm. What is missing is one link: reduce.rs contains no Drill variant at all — not Command, not ModelCommand. The seam is ready and the sentence is not sayable.

Why it was left out is a decision, not an oversight (gotcha 38): drilling creates the _Drill view and writes drill_state, which gotchas 30 and 1 rule session-local — pending_edits are keyed by (row, RecordCol) and belong to whoever staged them. A Command::Model is routed with no SessionId, which is right exactly when a change is addressed to no one session; drill is addressed to precisely one. That is the same argument that removed ApplyAndClearDrill from the wire in improvise-3x3u, so adding ModelCommand::Drill would reintroduce the bug that removal fixed. It needs the addressed form — ADR 001 layer 2.

The two entry points used to fail differently, and that asymmetry was the finding. i/a on an aggregate declines out loud: edit_or_drill answers the CellId::Aggregate arm with a status the user can read. But > (drill-into-cell) was a name resolve::step did not handle, so it became KeyOutcome::Upstream → ClientFrame::Key → Host::handle, whose Key arm is an explicit empty vec — a black hole, not a slow path (gotcha 47). Pressing > in the browser did nothing whatsoever: no status, no mode change, nothing. That is why this read as "never confirmed working" rather than as a refusal.

That silence is now closed, and the closing is what this file ships. step answers "drill-into-cell" with a SetStatus saying drill is not available in the browser yet — an interim the wording of which is load-bearing, since it must be true both today and on the day improvise-gd28 lands. The wire vocabulary is still absent; only the silence was fixed. Note for gd28: when the real drill arrives, a leftover "drill-into-cell" arm in step would shadow it with nothing failing, because a name that resolves never reaches the host.

The TUI is the control and it works: 12 drill tests pass across cmd/grid.rs, cmd/mode.rs, ui/effect.rs and ui/app.rs. So this is isolated to the client/wire, not a general regression.

A fixture fact that is itself part of the answer. web/demo.improv has no aggregate cell at all — gotcha 46 puts exactly one category on each visible axis precisely so every cell is a Record, and tests/web_demo_model.rs asserts it. So on the shipped demo a user cannot even reach the refusal without first changing an axis. anAggregateGrid therefore makes one, through the tile bar, the way a user would: Quarter cycles Page → None and every cell becomes an aggregate. The precondition is then asserted (td.editable count 0) rather than assumed, so neither test can pass against a grid of Records.

Both injections, run — against the tree before the interim, which is what made them two faults rather than one. Replacing the aggregate arm with None — silencing the honest refusal — failed both tests, and the second failed on its check_the_checker control, which is the point: with nothing answering, the control can no longer tell "> is silent" from "the page is dead", and the test correctly refuses to pass. Adding "drill-into-cell" => Some(vec![SetStatus(…)]) to step — making > resolve — failed only the second test and left the first green. Two faults, two different failure signatures, neither test passing for the other's reason. That second injection is now the shipped code, which is why the test it broke was rewritten rather than kept.

That control is load-bearing and not decoration: a test asserting nothing happened passes against a page that has stopped listening, so it presses i afterwards and requires #status to change. Without that, this file would be folklore with a green tick.

the_drill_key_and_an_aggregate_edit_refuse_for_different_reasons

The Rust half of the interim, and the assertion that carries the whole weight. Two keys on the same aggregate cell must both refuse and must not refuse with the same sentence: > says drill is unavailable, i says drilling into an aggregate needs the host. Collapsing them into one message would be the tempting tidy-up and would lose the distinction between "this key does nothing here yet" and "this cell is not one you may write".

The injection, and why it is not the obvious one. Replacing >'s sentence with the aggregate sentence looks like it should fail on the first assertion — and does not: that sentence contains both "drill" and "browser", so it clears the substring check. What fires is the anti-aggregate assertion lower down. The claim that the second assertion is the load-bearing one was doubted on review, tested, and confirmed; record it here because the first assertion reads like the discriminating one and is not.

The harness sibling (drill.spec.js) asserts the same distinction in a browser, but its not.toContainText("aggregate") is decoration under the only injection that exists — Playwright throws at the positive assertion above it first, so that line is never reached. The Rust assertion is the guard; the harness one is end-to-end confirmation that the string survives the wire.

a_view_row_click_focuses_moves_and_switches_to_the_row_clicked

improvise-iioi, and it is the same trap as the category click one level over: the activation must be resolved against the row clicked, never view_panel_cursor, because the SetPanelCursor ahead of it has not been folded when the resolver runs. Injecting exactly that — reading the name at the cursor instead of at index — yields SwitchView("Default") beside SetPanelCursor { cursor: 1 }, i.e. the cursor lands on Plan and the document switches to Default. Silent, and wrong in the half a user does not watch.

The fixture therefore holds two views and clicks the second. With one view, or with a click on the row already under the cursor, the bug is invisible — the same reason a_click_focuses_the_panel_moves_its_cursor_and_activates_the_row clicks Product rather than _Index.

a_formula_row_click_navigates_and_activates_nothing

The negative arm, and it is a statement about the rule rather than about the formula panel. The rule is "go there, then do what Enter does there"; ModeKey::FormulaPanel's keymap binds a/n/o to enter-mode formula-edit and d/Delete to delete, and no Enter at all. So the rule yields navigation and nothing else, and that is the rule applying rather than the fix stopping half way.

This test asserts the exact command vector, which is the whole of what it can say. It once carried a second, explanatory assert! that no FormulaEdit mode change appears — which could never have been the failing assertion, because the assert_eq! above it pins the same three commands and aborts first. A reviewer demonstrated it by injecting a ChangeMode(FormulaEdit) and watching the panic land on the assert_eq! with the explanatory message never printed. It was a comment wearing an assert!, and the argument now lives in context/code/clients.md where a comment run cannot hold it.

the_formula_panel_has_no_enter_to_mirror_and_the_view_panel_does

The guard that the removed assertion was pretending to be. The asymmetry — a view-row click activates, a formula-row click does not — is a fact about the keymap, and nothing tied the click to it. The reviewer proved the gap by adding Enter -> enter-mode formula-edit to ModeKey::FormulaPanel and running the whole workspace: 1381 passing, nothing failed, while click_formula_row still activated nothing. The click and the keyboard then disagree about what a formula row does, silently.

Injecting that same binding now fails this test and only this test. The failure message names click_formula_row as what must change, because the person who adds an Enter binding is not the person reading resolve.rs's click arms. The positive half (ViewPanel does bind Enter) is there so the test cannot pass by asserting that no panel binds anything.

The view and formula row clicks in the browser (improvise-iioi)

These began as two tests in harness/tests/pointer.spec.js. That file no longer exists: PR #61 deleted it and moved the pointer's browser half into harness/tests/contract.spec.js, whose stated scope is the wiring — the handler is on the element and passes that element's index — while what a click MEANS is improvise_protocol::resolve's and tested there. The assertions were merged into that file's own click test rather than restored, because resurrecting a file a merge deleted is how a deliberate removal gets undone by reflex.

They leave the panel open but unfocused — the only state in which the focus third of the click is observable.

History, not current evidence: the original pair was proved against the bundle built immediately before the fix, both failing there while the pre-existing pointer assertions passed. That run was against harness/tests/pointer.spec.js, which no longer exists. What holds the relocated assertions honest is the injection below, run in their new home.

The view test asserts three things — #view-name, the active marker and the selected cursor — because switching ends in NORMAL and a test that only checked the mode would pass against a click that did nothing but leave the panel. The relocation initially dropped two of the three, and a reviewer caught it; they are restored.

And the fixture was vacuous in a way the prose had already warned about. Default is index 0 and holds view_panel_cursor by default, so clicking it — which both the old pointer.spec.js and the first relocated version did — makes index and the cursor the same number, and reading either gives the same name. A reviewer injected switch_view_at(state, state.view.view_panel_cursor) into click_view_row and the whole contract suite passed 3/3: the exact fault this test, the ticket and the Rust test all exist for was invisible to the browser half. The fixture now switches to Default by keyboard, leaving the cursor there, then clicks Plan — so the two readings name different rows and the outcomes differ. Re-running that injection now fails it.

The blindness was inherited rather than introduced: the deleted file clicked Default too. It became worth fixing because the relocated test is now the only browser assertion on that surface.

One fact the reviewer's report supplied and this fix leans on: shipping the cure for one panel and not its two siblings reproduces the original report. A user who has just learned category rows are clickable clicks a view row and reads the silence as broken — which is literally what "I can't expand categories" meant.

The harness port: reuse is now opt-in

reuseExistingServer: !process.env.CI became === "1" on IMPROVISE_HARNESS_REUSE. A default-on reuse adopts a server another checkout left on the port and then tests that tree, which fired in both directions in one session — a false negative and, worse, a false positive. A path-hash default was considered and rejected: it still silently reuses when two agents share a worktree path, where an explicit opt-in cannot. CI is unaffected (it never reused) and a developer wanting the old speed sets the variable.

a_click_that_cannot_compose_its_activation_composes_nothing

improvise-hkr8. click_category_row ended with filter_to_item_at(state, index).unwrap_or_default(), and that None arm is not "nothing to do" — it is BasisCache::claim answering that the server has published no basis yet (gotcha 43), so the document change cannot be composed. The click therefore kept its navigation prefix (focus the panel, move the cursor), dropped its activation, and reported success. The keyboard handles the identical None correctly, by mapping step(..) == None to KeyOutcome::Upstream.

The fixture has to do two things a careless one would not. It expands Region so that row 1 is an Item row — a header row activates via ToggleCatExpand, which needs no basis and so cannot show the bug — and it asserts both preconditions (cat_tree_entry_at is an Item, claim is None) rather than assuming them, because an empty ClientState makes every state-dependent refusal look like the one under test.

Injecting the old unwrap_or_default() fails this test and only this test.

the_same_click_composes_everything_once_a_basis_is_published

The positive arm of the one above, and it is what stops the fix from being "return nothing more often". With a basis published, the same click composes all six commands: open, focus, move the cursor, two Command::Models and the status. Without this, deleting the activation entirely would pass hkr8's test.

a_first_tile_click_selects_without_touching_the_document

The user's ruling: a click selects, a second click cycles. The fixture publishes a basis deliberately, so the absence of a Command::Model is a decision rather than a client that could not compose one — pointed at an unpublished basis this test would pass for hkr8's reason instead of its own.

Both halves are asserted, because "the axis did not change" passes against a page where nothing happened at all: the positive half requires SetTileCatIdx plus ChangeMode(TileSelect), the negative half requires no Command::Model.

Four injections, four distinct signatures. "First click also cycles" fails this test, the_first_click_on_tile_zero_selects_it_like_any_other and clicking_a_different_tile_selects_it_rather_than_cycling_it — and not a_second_click_on_the_selected_tile_cycles_its_axis. "Second click does not cycle" fails only that last one. "already_selected reads the index alone" fails only the tile-zero test. Reverting hkr8 fails only the hkr8 test. No injection passes for another's reason.

t_then_a_click_on_the_leftmost_tile_cycles_it_immediately

Found on review, and it is a defect in the wording rather than the code. T enters TileSelect leaving tile_cat_idx at 0, so a click on the leftmost tile is a click on the already-selected one and cycles on the first gesture. Both loose summaries of the ruling — "a click never mutates on its own" and "a second click cycles" — are false against that probe.

The behaviour is right: a click does what Enter does there, and Enter in TileSelect cycles the tile under the cursor. The resolver cannot see how the state arose and must not try to. So the test exists to name the case rather than to change it, and it asserts the neighbouring tile answers the identical gesture by selecting — because the surprising half is that two adjacent tiles differ, and a reader who meets that in the wild should find it written down.

Note what this means for its sibling a_second_click_on_the_selected_tile_cycles_its_axis: that test sets the state directly rather than by clicking, so it already was the keyboard-entry case. Nothing was untested; the name and the argument were missing.

enter_in_an_empty_view_panel_resolves_locally_rather_than_upstream

switch_view_at returns Option, and its two callers answer the None differently on purpose. From a click_*, None means "this gesture composed nothing" — a dynamic fact, and hkr8's rule. From step, None means "this client cannot execute this command name" — a static fact about the vocabulary, which the_command_names_that_still_need_the_host_are_these exists to keep static. Two questions sharing one type, which is why the asymmetry reads wrong at first. (delete_view_at_cursor already answered Some(Vec::new()) the same way, so this follows the file rather than inventing.)

Nothing held the keyboard side to it until this test. A reviewer removed the unwrap_or_default() so out-of-range propagates None — making Enter in an empty view panel KeyOutcome::Upstream, gotcha 47's black hole — and the whole workspace passed under --no-fail-fast. That would make membership of the host-needed list state-dependent, the one property that list denies. Injecting it now fails this test and only this test.

The assertion is Ignored, not Local(vec![]): KeyOutcome::of maps an empty vec to Ignored by construction, so Local is never empty. What matters is that it is not Upstream.

the_first_click_on_tile_zero_selects_it_like_any_other

The trap in the ruling's own wording. "A second click on the already-selected tile" reads as an index comparison, and tile_cat_idx is 0 before anything has selected anything — so an index-only test would read tile 0 as already selected and cycle it on its very first click, making the non-mutation guarantee true of every tile but one. The condition is mode == TileSelect and tile_cat_idx == index.

clicking_a_different_tile_selects_it_rather_than_cycling_it

The other half of the same trap, from the opposite side: without it, "a click does not mutate" would hold only for the first click of a session, since every click after the first is a "second click" in the loose reading. Clicking A then B must select B.

How to know a launch default has stopped disarming things

The question this left open was how to know you have exhausted the class. Grep does not answer it: grep finds sites that name the flag, and the hazard is a test that merely starts from a default-built state and asserts something downstream, mentioning nothing. Three disarmed tests were found by grepping category_panel_open; that was luck, not method.

Mutation answers it, because it does not care what a test mentions. The recipe, which a reviewer ran across five sites in about twenty minutes:

For every production site that writes, propagates or reads the value, replace it with the constant the default supplies, and run --no-fail-fast. Sites where nothing fails are suspects. Then re-run each suspect with the default inverted. If it now fails something, the test was vacuous — the default disarmed it, and the fix is the fixture. If it still fails nothing, it was simply unguarded — a different problem, pre-existing, and a bead rather than a fixture.

The second step is the one that matters, and without it the two classes are indistinguishable: both look like "nothing failed". It is what established that the class is closed at two (set_panel_open_and_cursor, panel_commands_address_the_named_panel_only) and that two further silent sites are older problems this ruling did not cause:

• ui/app.rs's App::cmd_context propagator — hardcode it true and the whole workspace passes. registry.rs reads it for toggle-panel-and-focus's open-vs-close decision, so C on a closed panel would decide to close and nothing would fail. Invisible because cmd/mod.rs's test helper sets the field explicitly, so no command test reaches the propagator. Filed.
• improvise-wasm-client/src/render.rs's RenderModel field — hardcode it true and Rust sees nothing at all; only the Chromium harness catches it, at contract.spec.js's toBeHidden. That is literally improvise-wsaw reintroduced one layer up, and a Rust-only CI run cannot see it — which is the sharpest argument on file for why the browser job must be able to fail the build.

And a repair needs its own probe, because a repair can be shaped like a fix. The two-step recipe above finds a disarmed test; it does not tell you whether the repair you then write is real. That gap is not hypothetical — the first repair of panel_commands_address_the_named_panel_only folded [open:false, open:true], read as a fix in review, and was still vacuous.

The probe that settles it is a one-directional fault: make the writer if open { set true }, so the flag can be raised but never lowered. A vacuous repair cannot see this, because a test that only ever asserts the true direction is satisfied by a writer that only ever writes true. Injected into both copies at once, it fails set_panel_open_and_cursor and panel_commands_address_the_named_panel_only, each in its own copy — which is what establishes both repairs are genuine rather than merely differently spelled. Prefer it to re-reading the diff: the diff contained open: false in the version that was vacuous.

Note resolve.rs's panel_open reader is well guarded by contrast: hardcoding it true fails two click tests. So the picture is not "everything touching this flag is untested"; it is specifically the propagators.

the_terminal_constructor_inherits_the_shared_default_rather_than_setting_it

Prospective rather than present-tense, and the doc comment says so. With three panels, the_terminal_app_launches_with_the_category_panel_open and the_other_two_panels_are_shut_at_launch already cover every Panel::ALL member, so this test cannot currently fail without one of them failing too. A reviewer confirmed that by control.

It earns its place the way gotcha 12 describes Panel::ALL: a fourth panel reaches it from one ALL entry, and at that moment it becomes the only test asserting that App::new did not quietly give the TUI its own launch state — the divergence improvise-wsaw closed. Recorded here so nobody later reads a green tick as evidence of something it is not yet checking.

the_terminal_app_launches_with_the_category_panel_open

The user ruled (2026-09-20) that the category sidebar is visible at launch in the TUI as well as the browser, so improvise model.improv opening with it showing is intended. This is the guard on the front end the ruling newly changes: a_fresh_session_opens_with_the_category_panel asserts ViewState::default() in the protocol crate, and nothing downstream of it.

Why not a rendered-frame test: design-principles §7 says not to test ratatui Widget::render, and there is no TestBackend anywhere in this repo. The honest target is the TUI's own constructor. src/draw.rs's one-line read of the flag stays argued-not-tested, as gotcha 48 has it.

Three injections. Putting the shared default back to false fails this test and a_fresh_session_opens_with_the_category_panel. Making App::new override the default (app.view_state.category_panel_open = false) fails this test and the_terminal_constructor_inherits_the_shared_default_rather_than_setting_it — which is the one that would catch a TUI-only launch state being reintroduced, the divergence improvise-wsaw closed. the_other_two_panels_are_shut_at_launch stops "open everything at launch" passing the first.

set_panel_open_and_cursor

The launch default silently disarmed this test, and that is the finding. It did SetPanelOpen { Category, open: true } then asserted the flag was true — but test_app() builds from ViewState::default(), where it is already true. Its Formula and View siblings still default to false, so only the category arm went vacuous.

What that cost, demonstrated: replacing Panel::Category => app.view_state.category_panel_open = self.open with a no-op — so no effect could open or close the TUI's category sidebar at all — left the entire workspace green. C could be made to do nothing in the terminal with 1391 tests passing.

The fix is the fixture stating its own precondition: close the panel first and assert it closed, so the effect has to move the flag before the true direction is asserted. Injecting the no-op now fails this test.

Note the harness cannot see this one, and that is correct rather than a gap: the browser folds Command::SetPanelOpen through reduce_view, a different three-way match in a different crate from effect::SetPanelOpen's. Two derivations of one mapping — which is why the reduce_view guard needed the same repair independently. Since improvise-56ek there is one derivation, so that is history rather than a standing hazard; see below.

a_panel_command_writes_that_panel_and_no_other

The reduce_view half of the one above, and the first repair of it was still vacuous — worth recording because the mistake is subtle. Folding [open: false, open: true] and asserting the final state is true passes against a reducer that folds nothing at all: the default is already true, so neither command needs to land. Only asserting the false direction discriminates, because that is the one the default cannot supply. Caught by injection rather than by reading — the no-op fold reported NONE failing after the first fix.

improvise-56ek then removed the second derivation entirely: ViewState::panel_open_mut and panel_cursor_mut (plus their read halves) are the one place a Panel becomes a field, and both effect::SetPanelOpen::apply and reduce_view call them. The cure is one home, not a test holding two copies in step (doctrine(a_consolidation_that_keeps_its_compatibility_test_is_unfinished)), so there is deliberately no "the two agree" test — a wrong field in the one home is a failure in every caller.

This test replaces panel_commands_address_the_named_panel_only, which drove Panel::Category only and so could not tell one panel from another. It keeps that test's lesson by zeroing every panel before opening one.

Injected fault: point Panel::Category's arm at formula_panel_open. Fails by name for every panel in Panel::ALL.

That injection alone was not enough, and the gap is gotcha 3's shape. The first version asserted only through panel_open/panel_cursor — the read halves of the mapping it was testing. A consistent permutation of all four accessors is a self-consistent bijection: injecting Formula↔Category into panel_open_mut, panel_open, panel_cursor_mut and panel_cursor together left the test passing, while two unrelated tests that read raw fields failed. It caught only a non-injective mapping, which is exactly the injection first recorded here. The test now reads the three field pairs by name once per panel, and the consistent permutation fails it: "Formula is not the field Formula names".

Also corrected here: the claim that consolidation left "no second copy to agree with" was false when written. resolve.rs carried a fourth copy of the same Panel → ViewState three-way match, in the same crate on the same type; it is deleted and its three call sites go through ViewState::panel_open. What remains is not the same mapping: registry.rs maps Panel to CmdContext fields, a different type whose values are copied from view_state, and resolve.rs/registry.rs each map Panel to a (cursor, collection length) pair, which is a second derivation of something else and is lockstep.rs's subject.

a_fresh_session_opens_with_the_category_panel

The user's ruling that the category panel is visible at launch, implemented as the shared ViewState::default() rather than a browser special case — a browser-only default is "the page overrides the flag", which is the same defect as the "the page ignores the flag" bug improvise-wsaw fixed. The consequence, accepted deliberately, is that the TUI opens with the panel too.

The test also asserts the other two panels stay shut, so it cannot pass against a default that simply opens everything.

Two existing tests had to change, and both were pinning the old decision by inheriting it rather than stating it. panel_focus_cycles_from_the_focused_panel_not_the_first is about skipping a closed panel and took "the category panel is closed" from the default; it now spells that precondition. with_categories() is used by tests about a click opening the panel, so it now shuts it explicitly. Neither is the decision being re-made — the decision is re-made only in the harness, deliberately.

The launch state and the tile ruling in the browser

Also merged into harness/tests/contract.spec.js rather than left in the deleted pointer.spec.js — see the note above.

Two states, one mechanism: the sidebar is visible with no keypress, and C still hides it. Proved by injection in a real browser: setting el.categories.hidden = false (the page ignoring the flag) fails on toBeHidden; setting the shared default back to false fails on toBeVisible. Different signatures, different halves.

Only the second is a guard, and an earlier wording here got that wrong. It claimed "either alone passes against the bug wsaw fixed" — but under the new default, visible-at-launch passes for correct code and for a sidebar drawn unconditionally. The launch assertion states the ruling; the toBeHidden after the toggle is the only thing that still catches wsaw.

Note the first C now focuses rather than opens, since the panel is already open — toggle-panel-and-focus closes only when the panel is both open and focused — so the test presses it twice and the hide is the second press.

The tile tests were rewritten rather than adjusted, because the previous one asserted the behaviour the ruling reverses; its failure against the new code was itself the injection. The first-click test waits out a timeout before asserting the axis did not move, since a cycle would arrive asynchronously and an instantaneous assertion would pass against a slow one.

web/tests/ — the Node suite, and what was injected into it

No ### headings here on purpose: --check-evidence resolves a heading to a Rust fn, and a JavaScript test name under one would read as an orphan. These are keyed by file.

Every test below was proved able to fail by patching the code it names, checking the patch was on disk, running the suite and reading the failure — never by the absence of an error. Thirteen injections, thirteen failures:

What shell.test.js cannot reach, and the PR found out the hard way: it tests createShell in isolation, so it sees the watchdog RULE and never the app.js wiring that calls it. That distinction is now written into context/code/clients.md and guarded in shell.spec.js.

shell.test.js — socketUrl stops upgrading ws:// on an https page; composeStatus returns the model fact alone (which fails five tests, because the watchdog's messages are shell facts and vanish with it); fail() stops clearing the timer, so the watchdog pre-empts rather than being disarmed — the bug PR #13 fixed and PR #21 half-lost; extentOf stops subtracting the frame; frameCostOf stops counting the column-group line.

grid_plan.test.js — the data-row index is taken from the row's position in rows, so a group header consumes one (the click coordinate bug gotcha 1 is about); the group label is tested for truthiness, so a group legitimately named "" draws as "in no group"; typing is Boolean(model.editing), so an empty edit buffer reads as no editor open.

serial.test.js — the chain is replaced by Promise.resolve().then(...), which is what an async listener does: the slow first frame is overtaken. The suite also keeps that fault as a passing test in its own right, asserting the unchained pair really does come back swapped, so the ordering test cannot be green for want of a race.

render_surface.test.js — a pub sparkline: String added to RenderModel is reported unpainted; deleting paintTiles reports tiles unpainted; a getElementById that names an id index.html has not got is reported. The first is the shape of the bug the four widgets shared, and the list it checks against currently names doc_name/doc_dirty/doc_stored_as — improvise-5jna, which this test found rather than remembered.

bundle/wasm_surface.test.js — client.render_model() renamed to client.render_modal() fails both its tests. It reads the generated .d.ts, so a missing bundle is an assertion failure and never a skip.

web/assemble.sh — dropping web/shell.js from the copy list, with the page's own imports as the check. The first version of that guard anchored its sed at ^import, so it could not see the multi-line import that is the only one it exists for, and the injection passed: the guard was written, landed, and blind. That is what the injection was for.

harness/tests/contract.spec.js — eight injections into the served page

Patched in harness/serve/app/app.js, which is what the browser loads, so no rebuild stands between the fault and the run. The sidebar ignoring category_panel_open; the tile bar, view panel, formula panel and help overlay each never drawn; click_cell sending a constant row; click_category sending a constant index; and the typed buffer drawn without its caret. All eight fail.

The last one did not fail at first: the test asserted the typing class and not the text, so a cell drawn blank passed. The assertion was strengthened until the injection failed, which is the only reason it is worth having — and it is the same lesson as the eleven tests above: a class is a flag, and a flag is not a pixel.

every_advertised_command_answers_in_its_own_mode

improvise-rmvx. Gotcha 47 says an upstream key is a black hole, and the_command_names_that_still_need_the_host_are_these is the guard that was supposed to keep the list of them honest. It was built with in_mode(AppMode::Normal), so it only ever asked about Normal-mode bindings: add-record-row (RecordsNormal) and delete-formula-at-cursor (FormulaPanel) were outside its reach entirely and could never have failed it. A named list that silently scopes itself to one mode is a guard that looks broader than it is.

This asks it of every mode, and it asks it the only way that is not over-reporting. The naive version resolves every advertised name against an EMPTY ClientState and flags edit-or-drill, commit-cell-edit, create-and-switch-view and page-prev/page-next — but those are handled names refused by STATE, which is correct behaviour and not this bug. So the fixture is furnished: every widget has something in it, a basis is published, and a window is announced, so an Upstream can only mean the name is unhandled.

Two things it does NOT do, each because the first attempt did and was wrong. It does not call step with the advertised args: advertised carries None for "any binding of this command", and step's numeric and mode arguments are mandatory, so that reports move-selection, move-panel-cursor and move-tile-cursor as gaps in every mode. And it does not tokenise the rendered hint string: help::advertised is a table of command NAMES, so the cross-reference is exact and anything reading the rendered text is solving a harder problem than exists. The keys come off Keymap::keys_running, which labels_for now shares so "which keys" and "how are they spelled" cannot give two answers.

It watches BOTH silent variants, and the first version did not. KeyOutcome has two ways of saying nothing: Upstream, and Ignored — which KeyOutcome::of(vec![]) produces whenever a resolver composes an empty vector. To a user they are the same black hole. The first version asserted resolve(..) == Upstream(event), so three of the six commands this whole change exists to make audible could go completely silent with the entire evidence base green: degrading only add-record-row, delete-formula-at-cursor and view-back to Step::Declined(Vec::new()) left 1397 Rust tests, 19 harness tests and 26 node tests passing, because no browser spec presses those three keys. Found on review of PR #71. The check is now !matches!(.., Upstream(_) | Ignored).

The generalisation is worth more than the fix. KeyOutcome::of turning an empty Local into an honest Ignored is good design and it is also a laundering step: every wrong answer that composes nothing arrives wearing the variant that is usually innocent. So a guard's discriminator has to be state — did anything the user can see change — and never the shape of the return value. That is exactly why the +cat injection in a_locally_committed_creating_column_agrees_with_the_host failed (it compares documents and cursors) and the decline injection passed everywhere (nothing compared a screen).

Widening the check costs ten more entries, all one legitimate boundary case: move-panel-cursor mirrors MovePanelCursor, which returns nothing when the cursor does not move, so a one-row panel or a cursor on an edge answers Ignored for a reason that is not this test's subject. furnished therefore carries three of everything with all three panel cursors seated at index 1. Note what that rules out: seating them at 0 and calling the Up results expected would have hidden the real defect in the same list as the boundary case.

The injection: delete the "toggle-prune-empty" arm from declined. The test fails naming NORMAL: Char('P') and RECORDS: Char('P') — both modes, which is the widening the ticket was about, and a build that ran rather than a compile error. The review's own injection is also kept as a check: degrading the three unpressed declines to empty now fails naming FORMULAS: Char('d'), FORMULAS: Delete, RECORDS: Char('<') and RECORDS: Char('o').

What it found that the ticket did not predict: view-back is advertised in RecordsNormal (<, captioned "back"), so it was a seventh instance of the same class. The ticket had it filed under the Normal-mode host list instead, where being upstream is not a defect.

The five that remain are listed by name with a reason each. Three of them — commit-export, commit-save, execute-command — are reachable only from a mode declined refuses at the door, so a browser never stands in front of the hint; the other two are improvise-gcvb's records-cell commit, which needs record_col.

a_locally_committed_creating_column_agrees_with_the_host

improvise-gcvb. resolve's commit returned None for the whole of records mode, and the reason given was sound for the coordinate and measure columns — a category column renames every measure cell in the row, which needs record_col (gotcha 1). The guard was broader than its reason: a cell at the cursor now projects CellId::Create, and committing one is a single existing ModelCommand over the typed NAME that reads no record_col and writes no cell.

Both halves are proved by injection, and the second is the one that matters. Putting the broad is_records() early return back makes the test fail at "the client must answer this key locally". Deleting the CreateKind::Category early return — so +cat advances like any other column — fails with the client in RecordsEditing where the host is in RecordsNormal: the TUI returns straight after a +cat commit with a RebuildLayout and no cursor move, because an inserted column renumbers every index to its right and the advance was computed from the pre-commit layout (gotcha 23). A client that advanced anyway would land one column off, silently.

both_ends compares the document as .improv text, the mode, the status and every cursor, so neither half can pass by agreeing on the wrong thing. The fixture drives both hosts into records mode with the R key rather than hand-building a _Records view, because twin_of copies only the session slice and a twin without the view would refuse the commit for the wrong reason.

every_minibuffer_mode_paints_what_is_being_typed

improvise-fdt6. commit-buffer formula already resolved on the client — that half of the ticket was closed by an earlier wave — so the browser could enter FormulaEdit, type a formula and commit it. What did not exist was any way to SEE it: RenderModel::editing is populated only when mode.is_editing(), which is the two cell-editing modes, and it reads the "edit" buffer by name. Every character typed into FormulaEdit, CategoryAdd, ItemAdd, SavePrompt, ExportPrompt or CommandMode went into a buffer nothing painted. The mode opened, the user typed, and the screen did not move — which is exactly the dead-room shape the ticket names, arrived at from the rendering side rather than the resolution side.

The value is read with improvise_protocol::read_buffer rather than buffers.get, so the "search" special case (gotcha 11) keeps its one home.

The injection: .filter(|_| state.view.mode.is_editing()) on the new field, which is the pre-fix behaviour exactly. It fails naming "formula".

And the static check was not enough, which is the part worth keeping. web/tests/render_surface.test.js asserts that every pub field of RenderModel appears as model.<field> somewhere in app.js. It passed while the page was still broken: the string model.minibuffer was inside paintMinibuffer, and paintMinibuffer was never called and el.minibuffer was never looked up. A field can be mentioned by a function nothing invokes. harness/tests/keys.spec.js caught it on the first run, in the browser, which is the whole argument for that directory existing (gotcha 48).

nothing_declined_is_also_composed

step is declined then composed, and until this test the claim that the two lists cannot overlap was a doc comment. The dangerous direction is not a typo: it is a future ticket implementing view-back (or toggle-prune-empty, which is one projection field away) in composed and not thinking to delete its declined arm. The browser then goes on saying "not available in the browser yet" while the working code sits unreachable, and nothing notices — the classic shape of a check passing while the thing it names is broken. Raised on review of PR #71.

It is derived from declined itself, not from a list beside it: it walks every (name, args) bound in every mode's keymap — parents and prefix sub-keymaps included, sequence steps included — and for each one declined answers, asserts composed does not. A seventh decline is covered without coming here, which is the property a hand-written list could not have.

The injection: add "view-back" => Some(vec![Command::SwitchView(..)]) to composed. It fails naming NORMAL: view-back [] and RECORDS: view-back [].

It also found a real overlap on its first run. enter-mode is answered by declined for the three stranding modes and by composed for every mode, so composed's arm would have opened SavePrompt, ExportPrompt or CommandMode if declined were ever bypassed. Rather than moving the check, both halves now hold the rule — composed returns None for a stranded mode — so the failure direction if one is removed is the pre-PR Upstream, not a dead room.

harness/tests/help.spec.js — the overlay, asserted as words

PR #61 deleted "? opens help, and its rows are the shared ones" and nothing replaced it, so paintHelp, help, help_page and help_titles reached no assertion at all (improvise-78v6). What contract.spec.js carried in its place said only that a dt was VISIBLE — and an empty dt is a visible dt (improvise-igxp), which is the same shape as the caret bug above: a row is a frame, and a frame is not a word.

The injection both tickets name: blank keys.textContent in paintHelp, patched in harness/serve/app/app.js. Before this work it left all three contract tests passing. It now fails both tests in this file (the Welcome banner reads empty; the advertised key reads empty) and contract.spec.js, whose two help lines were strengthened from toBeVisible to the banner's text and the first dt.help-keys's text.

What the pairs helper is for. The overlay is a <dl>, and the association between a key row and its description is document order — dt then dd. Read as two lists they zip wrong, because a prose row emits no dd at all (deliberately: an empty one would leave a blank grid cell). Welcome is prose end to end, so dd count zero there is an assertion about that rule and not a coincidence.

"a key the overlay advertises does what the overlay says it does"

The assertions above are still about a string on a screen; this one asks whether the string is true. The key for Jump to last row is read OUT OF THE DOM, the overlay closed, the key pressed, and the selection asserted onto the last row. A page drawing a plausible key it does not have — what a hand-spelled table decays into — fails here, and the spec holds no second copy of the keymap.

It presses the FIRST key the row names because a row is a compaction of every binding that reaches the command (h j k l ← ↑ → ↓ is eight).

harness/tests/grouped.spec.js — the first browser run of improvise-anr9

web/demo.improv has no groups and one category per visible axis, deliberately (gotcha 46), so the multi-level header, the group span, the collapse indicator and the inline group row — exactly the code improvise-anr9 added — had never been rendered anywhere a test could see (improvise-plcx). The fixture is harness/fixtures/grouped.improv, served beside the shipped demo by harness/build.sh, and the shipped document is unchanged.

A missing seed is not an error: web/worker.js answers a fetch that 404s with an empty model. So a typo in the filename yields a page that draws a grid, and "a grid is drawn" would pass on it. Every assertion here is about labels the fixture really carries.

openGrouped waits with retrying assertions and the tests then read once. The head and the row labels are read in a single evaluate each, because what these tests assert is the RELATION between the lines — and a one-shot read cannot wait. The grid is painted from the first projection and reframed by the viewport the page then announces, so the helper gates on the head's shape, its first group and the first row's innermost label before anything is read.

Five injections, five distinct failures, patched in harness/serve/ so no rebuild stands between the fault and the run:

• gridPlan slash-joins the level tuples into one line (the exact defect anr9 fixed) — fails all three, because openGrouped waits on the head's shape before any test reads it;
• th.colSpan = 1 on every column group header — fails the span test alone;
• a stray tr.insertCell() on the inline group row — fails the group-row test alone, which is the DOM half of RenderRow::Group carrying no cells;
• indicator(false) hard-coded — fails on ▶ Upland while ▼ Inland still passes, which is why the fixture has one collapsed group and one open one;
• collapsed: Region/Upland removed from the served document — fails on the rows that reappear, so the assertions see the collapse and not just the glyph.

A bug this fixture surfaced rather than predicted. Coastal is the row frame's FIRST entry and its header is never drawn: the spec asserts two group rows where the document has three, with improvise-0o6x named on the line. That count is a record of an open bug, not an endorsement — when 0o6x lands it becomes 3 and this line is where the change must be argued.

harness/tests/landing.spec.js — the front door

docs/index.html is copied to the site root by web/assemble.sh, so the harness has been serving it all along with nothing asserted about it (improvise-bgtf).

Counting the four .ap-player elements proves nothing, and that is the whole reason this is a spec rather than a one-liner: autoPlay is false, so asciinema-player fetches no cast until play is pressed. A page whose every cast path 404s constructs four players, throws no page error, and looks identical to a working one. Injected while the page was being written (./casts/ -> ./cats/) the construction-only check passed on the broken page.

Re-injected into harness/serve/index.html now, the spec fails at the first player: .ap-line elements exist only once there is a cast to lay out. The spec also asserts, BEFORE pressing anything, that no .cast has been requested — without which the network evidence below could be satisfied by a page that fetched them eagerly, which is not the page we ship.

Two assertions where one looks sufficient: the rendering says a cast played, and the recorded responses say four distinct casts answered 200. Three players showing the same recording satisfies the first and fails the second.

"the front door reaches the app it advertises" follows the footer link rather than asserting its text, because whether ./app/ resolves is a fact about the assembled tree. Injecting href="./aplication/" fails it.

harness/tests/contract.spec.js — the ninth injection, and a lost guard

The lost guard. improvise-78v6 asks for the test-name diff over PR #61's range, and it finds a fourth loss beyond the help test: "a click on an item row filters, as Enter does". contract.spec.js asserts the CATEGORY arm of click_category_row (the row expands) and nothing asserts the ITEM arm, whose rule is "do what Enter does here" — filter. Only #status distinguishes them, so a click wired to the wrong arm passed the whole file. Restored inside the click test, and proved by injecting click_category(row.is_category ? index : 0), which fails that line alone.

The diff that finds this is two commands, and is worth running on any PR whose subject is a lost guard:

M=$(gh pr view 61 --json mergeCommit -q .mergeCommit.oid)
for r in "$M^1" "$M"; do
  git ls-tree -r --name-only "$r" -- harness/tests web/tests |
    while read -r f; do git show "$r:$f" | grep -oE 'test\("[^"]*"'; done
done

The other two losses are deliberate: pointer.spec.js's sidebar test was superseded by the open-at-launch ruling, and the widgets file was merged into this one.