Files
khosra/docs/theme-contract.md
T
Claude Opus 5andbdeshi c8006e7358 add paginated section index pages
The first collection page earns the Query primitive: content.Query{Section, Lang}
with Site.Run, newest first, undated after dated, ties broken by key so the same
query always answers in the same order. No cache signature — nothing caches, and a
signature with no consumer is speculation.

Pagination lives in the path (ADR-0028): page one is the bare listing URL,
/page/1/ redirects to it, and a page past the end is 404 rather than an empty page,
because an empty page is a URL that means nothing. `page` is therefore a reserved
segment inside a section, now recorded in content-model.md.

Two kinds of page means two parsed template sets already — base plus the block that
kind defines — which is ADR-0019's per-type shape arriving by need rather than by
anticipation. A head struct is embedded in both Page and List so base.html has one
contract, and theme-contract.md gains the listing fields.

Bundle gains Date, accepting an unquoted YAML date or an RFC 3339 string, since
yaml.v3 hands back time.Time for one and a string for the other.

Evidence: 12 posts → /posts/ shows 10 with rel=next to /posts/page/2/,
/posts/page/2/ shows 3 with rel=prev to /posts/, ordering is post-12 11 10,
/posts/page/1/ 301s to /posts/, /posts/page/9/ is 404, /bn/posts/ is 200.
2026-07-30 02:08:12 +06:00

5.7 KiB

Theme contract

What the engine promises a theme, and the only thing this repository is bound to (ADR-0023). A theme's markup, layout and styling are not the engine's business; a theme's inputs are.

STATUS: partly live. The fields under Live today exist and are gated; everything else is the shape the contract takes when the feature arrives. All of it is engine obligation, not theme instruction — a theme may ignore any of it.

Live today

A bundle page receives:

Field Contents
.Title may be empty; a template falls back to .Key rather than failing
.Lang the locale of this variant, always set
.Key the bundle's identity, without language or extension
.HTML the rendered body, already escaped
.Extra every frontmatter key the parser does not name (ADR-0002)
.Style the reference theme's stylesheet, inlined so a bare site root needs no asset route
.Canonical the permalink of the variant actually served — not the URL requested, which differs when the fallback chain supplied another language
.Alternates every language this key exists in, as .Lang and .URL, for hreflang

Two named templates: base is executed for every page; main is the block each kind of page defines and a theme redefines. There is one parsed set per kind — bundle and listing today — so two kinds may both define main without colliding (ADR-0019).

A listing page receives .Title, .Lang, .Canonical, .Style as above, plus:

Field Contents
.Items entries on this page: .Title, .Key, .URL, .Date
.Page, .Pages 1-based position and total, Pages at least 1
.PrevURL, .NextURL empty at the ends; newer is prev, because the order is newest first

The stability rule

Fields and names are added, never renamed or removed. Absence is always legal: a template reading a field that does not exist gets the zero value and must not crash, and the engine must not make a missing field fatal at request time (ADR-0002, invariant 1). This is the View-layer freeze from architecture.md, arriving as soon as a theme exists rather than at Arc 2.

Breaking the contract is not a feature — it is a new contract version, and it needs an ADR.

What the engine provides

Provides Detail
the page object known fields plus an Extra bag carrying unknown frontmatter (ADR-0002)
the resolved cascade settings after site → section → bundle resolution (ideas/deferred-decisions.md)
queries the page needs its sequence neighbours, its taxonomy terms, its section's members
named template lookup per-type sets; a theme redefines a named block and inherits the rest (ADR-0019)
URLs every path the engine emits, so a theme never constructs one by hand
per-page assets the styles / scripts frontmatter lists, resolved relative to the bundle
chrome strings looked up by key and language, never hardcoded English in a template
validity windows a template that renders time-dependent output declares one

Extras view

For a request under a bundle's extras directory (ideas/deferred-decisions.md) the engine additionally provides:

Field Contents
.Extras.Entries the tree: Name, Path, URL, RawURL, Kind, Size, IsDir, ModTime
.Extras.Selected nil on the bare listing; otherwise the chosen entry
.Extras.Selected.HTML rendered output for markdown and text kinds; empty otherwise
.Extras.Selected.RawURL always present — for <img src>, <object data>, or a download link

.Bundle is the parent, so a theme has its title, language and breadcrumb. Selecting an entry is an ordinary link and a full re-render, so a sidebar-plus-pane layout needs no JavaScript; swapping the pane client-side is a later enhancement over working markup, never a requirement.

What the engine does not provide

Layout, class names, CSS, client-side behaviour, and any choice about how something looks — including how media is embedded, how a listing is arranged, and whether something appears in a sidebar. Those are theme decisions, and a request touching them is split: a contract extension here, a change there.

The engine also does not provide a component library, a CSS build step, or a JavaScript runtime. conventions.md holds the output floor the engine itself meets — semantic HTML, zero-JS, every image carrying width, height and alt — and a theme is expected to stay inside it, but the engine does not enforce a theme's markup.

The reference theme

The binary embeds a reference theme — templates plus one small stylesheet — so a bare site root renders (ADR-0026). It exists to make this document executable: it implements every field and block named here and nothing else, and a golden-file test through it catches contract regressions before a real theme does.

It is not a design. Legibility only, no branding, no visual opinions, no JavaScript — verify.sh fails on a <script tag in it. If it starts accumulating taste, it has stopped being a reference.

It demonstrates the contract; it is not the contract. Changing it does not change what a theme may rely on — which is why verify.sh also fails when it changes without this document changing, since in practice the two drift together.

Splitting a request

When a feature spans engine and theme, this repo delivers:

  1. the contract extension — new fields, new named blocks, new queries, new URLs;
  2. a note stating what a theme must do to use it, precise enough to act on without this conversation;
  3. embedded defaults updated far enough to prove the extension works.

It does not deliver the theme. Claiming otherwise is the same error as claiming to have migrated content in a site root this repo cannot see.