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The human chose the second option: a route sits beside the key rather than replacing it. So `slug` renames what a bundle is served at, in every language, and identity stays derived from the path — which is exactly what keeps ADR-0033 intact, since series membership is the directory. A series landing page can now be renamed without orphaning its chapters, and there is a test that says so. `Site` resolves routes at index time, because only it can see whether every variant agrees. Disagreement is dropped rather than resolved, as is a slug landing where another bundle already answers — the same rule colliding keys and contested aliases already follow. The key a slug moved away from stops answering, so the old address does not quietly keep working. Two bugs surfaced doing this, both older than this change: An alias naming its own bundle's former key was rejected as "an alias that names a real bundle" — which made rename-plus-alias, the entire point of ADR-0008's alias mechanism, impossible. The check now asks what a request asks: is anything actually served there. Aliases were counted per declaring *file*, so a bundle whose two language variants both listed the same alias looked like two rival claimants and lost the alias. It is a set of keys now. This one only appears with translated content, which is why no fixture had caught it since entry 4 — the real binary did, on the first multilingual rename.
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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. Not its address — a slug moves the address and leaves the key alone, so link with .URL or .Canonical and never by assembling a key (ADR-0035) |
.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. Absolute when the site declares base, since a canonical link is resolved by machines rather than by the page (ADR-0039) |
.Alternates |
every language this key exists in, as .Lang and .URL, for hreflang. Absolute on the same terms |
.Site |
what the site declared about itself: .Site.Base and .Site.Title, either possibly empty |
.Sequence |
the series this page sits in, absent when it sits in none (ADR-0033) |
.Sequence carries the reading order and this page's place in it:
| Field | Contents |
|---|---|
.Sequence.Title, .Sequence.URL |
the series' title (may be empty) and its permalink |
.Sequence.Members |
every entry in reading order, each as an .Items entry — ascending, unlike a dated listing |
.Sequence.Index, .Sequence.Count |
this page's 1-based position and the total; Index is 0 when this page is the series landing itself |
.Sequence.Prev, .Sequence.Next |
the neighbours, absent at the ends and on a landing page. Prev is the earlier entry — the opposite sense of a listing's .PrevURL |
.Sequence.First, .Sequence.Last |
the ends of the series, present whenever it has members |
A landing page therefore renders an archive from .Members and a chapter renders navigation from
.Prev/.Next, both from one field. Membership and order are the engine's business
(content-model.md); a theme never sorts.
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 |
Chrome text and formatting
Three functions, available in every template including a site root's own blocks. They exist so no template hardcodes English: the words the engine supplies are the engine's to localise (ADR-0034).
| Call | Gives |
|---|---|
{{t .Lang "newer"}} |
one phrase in that language. Extra arguments fill %s placeholders in order |
{{num .Lang .Page}} |
an integer in that language's digits — 12, ১২ |
{{day .Lang .Date}} |
a date as that language reads it — 8 March 2026, ৮ মার্চ ২০২৬; empty for a zero date |
Phrase keys today: newer, older, empty, page-of (two arguments), position (two arguments). An
unknown language falls back to the default locale and an unknown key returns itself, so a missing
translation can never blank a page or fail a render.
Three rules a theme must keep: put the machine-readable form in the attribute and the localised form in the
text — <time datetime="{{.Date.Format "2006-01-02"}}">{{day .Lang .Date}}</time>; never localise
.Title, .HTML or anything else the author wrote; and never pass a URL, key or path segment through
these functions. An address is not chrome (content-model.md).
A site root cannot add or override a phrase yet. A theme needing its own words writes them in its own
block; site-supplied strings wait for the settings cascade (ideas/deferred-decisions.md).
Shortcode fragments
templates/shortcodes.html holds one named template per shortcode, and that is where a shortcode's markup
lives — the engine parses the call and supplies its data, never any HTML (ADR-0036).
Every fragment receives the same two fields (ADR-0037):
| Field | Contents |
|---|---|
.Args |
the call's key="value" pairs, exactly as the author wrote them |
.Items |
a list the engine gathered, empty unless that shortcode gathers one |
| Shortcode | Template | Receives |
|---|---|---|
{{< figure src="…" alt="…" caption="…" >}} |
figure |
.Args.src, .Args.alt, .Args.caption |
{{< gallery >}} |
gallery |
.Items — the picture filenames beside the bundle, in filename order |
{{< include file="…" >}} has no fragment: an included file is content, so it renders as Markdown in
place and a theme has nothing to style about it (ADR-0038).
Authored and engine-supplied data are kept apart so a src argument can never be confused with a src the
engine found. Arguments are escaped by html/template like any other data, in whichever context the
template puts them — which is what keeps an author's text out of the markup. A call whose template is
missing renders nothing and logs; it never fails the page.
A gallery entry is a bare filename, relative to the bundle, so a template writes it straight into src. It
carries no alt text or dimensions, because nothing in a filename supplies either.
The set is overlaid the same way as the page kinds: a site's templates/shortcodes.html is parsed after
the embedded one, so redefining figure replaces it and any fragment left alone is inherited. Argument
names are contract, added but never renamed.
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 — live, see above |
| 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). Each set is built from named files
and only those are overlaid — base.html plus that kind's block file (page.html or list.html), and
shortcodes.html on its own. 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:
- the contract extension — new fields, new named blocks, new queries, new URLs;
- a note stating what a theme must do to use it, precise enough to act on without this conversation;
- 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.