Files
khosra/docs/theme-contract.md
T
bdeshi b14658094e add tag listings, global and section-narrowed
One global namespace (ADR-0018): /tags/{term}/ spans every section and
/{section}/tags/{term}/ narrows it. Listings group by section so one busy term
stays readable, which needed List.Groups alongside Items — list.html renders
whichever is set.

This is Query's second use, so it gained a Tag field rather than being generalised
on speculation: one filter, two callers. Tag slugs lowercase and hyphenate,
preserving script, so "Long Monsoon" and "long monsoon" are one term while Bengali
passes through unchanged. Hand-chosen slugs per term still wait for the type
declaration that owns overrides.

`tags` is reserved at the top level and inside every section, alongside `page` and
the language prefixes. A tag listing redirects to its canonical URL only once it is
known to exist, matching the rule bundles already followed — otherwise a canonical
URL for nothing confirms what is not there.

One stale test expectation fixed rather than worked around: it asserted tags land
in Extra, which stopped being true when tags became a named field.

Evidence: /tags/monsoon/ lists Hello World under posts and First Rain under comics;
/comics/tags/monsoon/ shows one; /tags/monsoon 301s; /tags/nothing/ and /tags/ 404.
2026-08-01 02:23:34 +06:00

6.5 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
.Groups set instead of .Items when entries are grouped — a tag listing groups by section, each .Name and .Items

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.

Overriding it

A site root's templates/ is parsed after the embedded set, and the last definition of a name wins, so a theme redefines one named block and inherits the document (ADR-0019). Per kind, exactly two files are overlaid — base.html and that kind's block file (page.html or list.html). Overlaying every site template into every set would let a listing's main leak into bundle pages, which is the collision per-kind sets exist to prevent.

templates/theme.css in the site root replaces the reference stylesheet entirely; there is no merging.

static/ in the site root is served verbatim under /static/. Directory paths answer 404 rather than listing their contents.

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.