Runtime Overrides

A resolved dashboard is not frozen. At resolution time a caller may supply an override set — a flat map of address → value — that adjusts the document before the tree is assembled. Both lattice resolve (via ResolveWithValues) and lattice serve (per request) accept the same override set, so the runtime model is identical whether you re-resolve from the CLI or from the served page.

Overrides are ephemeral: they apply only to that single resolution. The document on disk is never mutated, and an empty override set yields exactly the same resolved tree as a plain resolve. The durable counterpart — a recorded edit to the document itself — is a JSON Patch changeset, gated by the same configurable surface; its application is future work.

Two override kinds, one addressable map

The override set is a single map[string]any whose key is an address. The address shape selects what the value targets:

A key with no . is a variable override; a key of the form <node-id>.<field> is a config override. The two kinds share one map and are routed by address — neither the CLI nor the server has to separate them. A document-scope configurator posts the same shape with a reserved $-keyword as the node half ($theme.<token>, $manifest.<field>).

Variable overrides

A variable override replaces the effective value of a settable variable — see Runtime inputs for the full rules. In short: the value flows through the variable model (override > default), computed variables recompute against it, and dependent ${var} / $var consumers update live. An override for an undeclared name is a no-op; a value that fails the variable’s type / enum check fails fast with the usual VAR_TYPE / VAR_OPTIONS_INVALID codes.

Config overrides

A config override sets one config field of a single resolved node, addressed by <node-id>.<field>. It is applied after interpolation, so it overwrites whatever an interpolated ${var} produced for that field, and is validated against the node’s configurable surface — only a field the item type declares configurable may be overridden. Failures are fail-fast:

• An address whose <field> is not on the node’s configurable surface fails with CONFIG_OVERRIDE_FIELD_UNKNOWN.
• A value that violates the field’s declared type / constraints fails with CONFIG_OVERRIDE_VALUE_INVALID.

Like every override, a config override is ephemeral — it mutates only the resolved instance for that resolution, never the document.

Precedence

Within a single resolution the layers compose top-down, each later layer winning for the value it touches:

1. Declared defaults — the variable default and the node’s authored config.
2. Variable overrides — replace settable variables; computed variables recompute against the new values; ${var} / $var consumers see the result.
3. Config overrides — applied last, after interpolation, so a <node-id>.<field> override wins over whatever the interpolated config produced for that field.

So for a field whose value came from a ${var} template, a variable override changes it through interpolation, while a config override on that same field pins it regardless of interpolation — the config override is the more specific, later-applied layer.

Supplying overrides through serve

lattice serve collects the unified override set from two transports and routes both kinds — variable and config — into the same map:

• URL query parameters. Each ?address=value becomes one override. A bare name (?region=eu) is a variable override; a dotted name (?summary.title=Pinned) is a config override. Query values arrive as text and are coerced to the target’s declared type before validation.
• The /api/resolve endpoint. The served page POSTs a JSON object of the current overrides on every re-resolve. Interactive widget controls post their bound variable as a variable override on change; a client may also include <node-id>.<field> keys to drive config overrides.

For example, serving examples/widgets-dashboard.json and requesting

GET /?region=eu&summary.title=Pinned

resolves the document with region overridden to eu (a variable override that flows through the ${region} template into the summary table) and the summary table’s title config field pinned to Pinned (a config override that wins over the interpolated "${label} — ${region}" title). Both adjustments are ephemeral to that request.