Page-block canvas draws the generic unknown-block icon for types that render fine but are excluded from the palette (`record:chatter`)

[os-zhuang]

Observation filed unassigned by the domain:ui dev seat implementing #5495 (palette offers the canonical record:discussion). Not a regression that change introduced — the same gap existed before it, on the other spelling — but #5495 moves which spelling is affected, so it is worth recording rather than leaving for the next reader to re-derive.

What was measured

packages/app-shell/src/views/metadata-admin/previews/PageBlockCanvas.tsx draws every node's icon and colour tone from the palette catalogue:

const meta = BLOCK_TYPE_META[typeStr as BlockTypeId];
const Icon = meta?.Icon ?? UnknownBlockIcon;
const tone = resolveBlockTone(typeStr); // -> BLOCK_CATEGORY_TONE['misc'] on a miss

BLOCK_TYPE_META is the palette's offer list, and PALETTE_EXCLUSIONS (same file, block-types.ts) is its documented ledger of block types that are deliberately not offered. Those two lists answer "what may an author drag in", which is a different question from "what may an author already have in this page" — but the canvas chrome reads only the first.

For every exclusion whose reason is "no renderer" (ai:chat_window, element:form, element:record_picker, element:text_input) the generic box is arguably right: those nodes genuinely do not render. One exclusion is different: the record:chatter / record:discussion pair is excluded because the pair is one renderer under two names, so exactly one of the two spellings is always an unoffered type that renders perfectly. Opening an existing page that carries the unoffered spelling shows that node in the outline with UnknownBlockIcon (a plain box) and the neutral misc grey tone, instead of MessageSquare and the blue record tone its twin gets one line above.

blockLabel() is not affected — it never reads BLOCK_TYPE_META, and falls back to the raw type string. The gap is icon + tone only.

Why this is not new, and what #5495 changed about it

Before #5495 the unoffered spelling was the canonical record:discussion — the one packages/plugin-detail/src/synth/buildDefaultPageSchema.ts emits, i.e. the one in every page the platform generates for itself. After #5495 it is the legacy record:chatter alias, which is the rarer spelling. So the change strictly reduces how often this is seen; it does not close it.

Shape of a fix, if it is wanted

The information needed already exists — the pair shares a renderer, a category and an icon. Options, roughly in order of size:

• a small alias→canonical display map consulted by PageBlockCanvas when BLOCK_TYPE_META misses, so an unoffered-but-renderable type borrows its twin's icon and tone without becoming offerable (block-config.test.ts's "no type is both offered and excluded" must keep holding — which is why this cannot simply be a second BLOCK_TYPE_META entry);
• or split the catalogue into "display meta" (every type the canvas can encounter) and "palette offer list" (the subset an author may drag), making the two questions above two lists instead of one.

Either is larger than the S-size #5495 card and touches its hot file, so it was deliberately not folded in.

Refs: #5495 (where it surfaced, and the PR that moves which spelling is affected) · #2943 (the guard that made PALETTE_EXCLUSIONS an explicit ledger).

[claude]

Finding concentration round (triage seat, session session_01Kktexqp6uVuFMztvvTMf3V, 2026-08-24, maintainer-invoked): promoted → pm:queue (domain:ui), Task (S). Give the canvas an icon/tone source that covers renderable-but-unoffered types (e.g. record:chatter): consult the renderer registry (or extend BLOCK_TYPE_META with a non-palette entry class) instead of falling to the unknown-block icon for types the page can legitimately contain.

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[yinlianghui]

Claim: PM loop round 38 (refill slot)
Session: session_01CSoz9uGhaaSgiq3hshtN7L
Branch: claude/issue-5837-canvas-icon-for-unoffered-types
Worktree: objectui-issue-5837
Domain: domain:ui
File surface: packages/app-shell/src/views/metadata-admin/previews/PageBlockCanvas.tsx, block-types.ts (the catalogue + PALETTE_EXCLUSIONS), their tests + a changeset
Container & model: S, mode:subagent, model: opus
Clause-②: no — designer chrome (icon + tone) on a node that already renders. No declaration moves, nothing becomes offerable.

⚠️ SERIAL — a sibling is live in your directory

#5725 is IN FLIGHT in the SAME subtree, packages/app-shell/src/views/metadata-admin/previews/ — its files are view-column-io.ts + its tests + the pin in ViewColumnInspector.identityRead.test.tsx. Different files, so no write collision, but the directory is shared. ⛔ Do not touch view-column-io.ts, FieldsListEditor.tsx, or ViewColumnInspector.*. If your fix needs any of them, ⛔ stop and report.

Other siblings: #5874+#5875 (plugin-kanban, plugin-detail ×2, app-shell/src/utils/ ×2 — ⛔ stay out), #5893 (packages/types/src/{base,plugin-scope}.ts), plus #5903's PR #6053 and #5676's PR #6061 awaiting gate reads.

裁决 — triage's direction

Triage seat, 2026-08-24 (finding concentration round), → pm:queue / Task (S). Verbatim: "Give the canvas an icon/tone source that covers renderable-but-unoffered types (e.g. record:chatter): consult the renderer registry (or extend BLOCK_TYPE_META with a non-palette entry class) instead of falling to the unknown-block icon for types the page can legitimately contain."

The mechanism, and the one constraint that shapes every fix

PageBlockCanvas.tsx draws icon and tone from the palette catalogue:

const meta = BLOCK_TYPE_META[typeStr as BlockTypeId];
const Icon = meta?.Icon ?? UnknownBlockIcon;
const tone = resolveBlockTone(typeStr); // -> BLOCK_CATEGORY_TONE['misc'] on a miss

⭐ BLOCK_TYPE_META answers "what may an author drag in". The canvas is asking "what may an author already have in this page". Two different questions, one list. That framing is the card's real contribution and it should drive the fix.

For exclusions whose reason is "no renderer" (ai:chat_window, element:form, element:record_picker, element:text_input) the generic box is arguably right — those nodes genuinely do not render. ⚠️ One exclusion is different: record:chatter / record:discussion is excluded because the pair is one renderer under two names, so exactly one of the two spellings is always an unoffered type that renders perfectly. It draws UnknownBlockIcon and the neutral misc grey where its twin one line above gets MessageSquare and the blue record tone.

⛔ The hard constraint: block-config.test.ts's "no type is both offered and excluded" must keep holding. That is why this cannot simply be a second BLOCK_TYPE_META entry — the card says so explicitly, and it is the trap that makes the obvious fix wrong.

The card names two shapes; ✅ either is acceptable and you choose on measurement:

1. a small alias→canonical display map consulted when BLOCK_TYPE_META misses, so an unoffered-but-renderable type borrows its twin's icon and tone without becoming offerable;
2. split the catalogue into display meta (every type the canvas can encounter) and palette offer list (the subset an author may drag) — two questions, two lists.

⚠️ (2) is the honest shape and (1) is the small one. If (2) turns out to be more than an S card's worth, take (1) and say so, naming (2) as the follow-up.

PM mechanism assumptions — measure, do not assume

1. The card is from 2026-08-23 and packages/app-shell moved twice today (fix(console): trim hidden: true fields from the approvals drawer summary card #6031, refactor(app-shell): type RecordDetailView's confirm handler as the published ConfirmationHandler #6035). Re-derive the BLOCK_TYPE_META read, resolveBlockTone, and the PALETTE_EXCLUSIONS ledger on your merge-base; report any delta.
2. ⚠️ Which spelling is currently unoffered is a moving fact. Before The page-editor palette offers the legacy record:chatter and (as of the 17.1.0 pin) explicitly excludes the canonical record:discussion — the pair is advertised under the alias #5495 it was the canonical record:discussion — the one plugin-detail/src/synth/buildDefaultPageSchema.ts emits, i.e. in every page the platform generates for itself. After The page-editor palette offers the legacy record:chatter and (as of the 17.1.0 pin) explicitly excludes the canonical record:discussion — the pair is advertised under the alias #5495 it is the legacy record:chatter. ⛔ Do not hard-code either; the fix must work whichever way the pair is oriented, or a future flip re-opens this.
3. blockLabel() is NOT affected — it never reads BLOCK_TYPE_META and falls back to the raw type string. ⛔ The gap is icon + tone only; do not widen into labels.
4. ⚠️ Do not make the "no renderer" exclusions borrow an icon. They are correctly generic. A fix keyed on "is excluded" rather than "is renderable" would give element:text_input a friendly icon it has not earned. Key on renderability, and say how you determined it.

Verification

Direction predicted before running: a page carrying the unoffered spelling of the pair must draw the same icon and tone as its offered twin; revert and show the pin goes red.

Counter-probes, three, and they are the fix's whole safety margin: (a) block-config.test.ts's "no type is both offered and excluded" must stay green — run it explicitly and quote it; (b) a genuinely unrenderable exclusion (element:text_input) must still draw UnknownBlockIcon and misc; (c) the palette's offer list must be unchanged — nothing became draggable. ⛔ Without (c), "the icon appears" is satisfiable by quietly making the type offerable, which is the exact invariant #2943 made an explicit ledger to protect.

Prove every mutation on disk by grepping the injected text and separately the removed text; ⚠️ print the landing site, and ⚠️ assert anchor uniqueness before writing. Restore under trap … EXIT INT TERM with a cwd-independent restore command — a trap that fires is not a trap that restored (measured on #5926 today). Confirm git diff HEAD --stat empty afterwards.

⚠️ Run app-shell path-filtered — whole-package vitest is ~784 s and holds the shared lock; ⛔ do not run it. Gates by name with exit codes: pnpm --filter @object-ui/app-shell type-check (⚠️ hyphenated; echo the script name; distinguish the unbuilt-closure red from the missing-node_modules red — both hit today, different fixes), the path-filtered vitest including block-config.test.ts, eslint on changed files with merge-base delta. ⚠️ Plain eslint . per package — ⛔ no --no-inline-config.

Run node scripts/check-changeset-presence.mjs rather than guessing. Draft PR, Fixes #5837. ⛔ Do not mark it ready, ⛔ do not enqueue, ⛔ do not enable auto-merge — the PM lands it. Post the terminal report here (plain-text first-line marker os-dev-report; ⛔ avoid short angle-bracket placeholders in prose — the sanitizer ate one on #5926 today) and return it.

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