Capability presets

Capability flags declare which optional Slack block types the destination surface supports. They are consumed through the capabilities and capabilityOverrides options of convert(); this page documents the underlying exports. For guidance on choosing a profile, see Slack compatibility.

CapabilityFlags

interface CapabilityFlags {
  readonly markdownBlock: boolean;
  readonly tableBlock: boolean;
  readonly preformattedLanguage: boolean;
  readonly headerLevel: boolean;
  readonly dataTable: boolean;
  readonly dataVisualization: boolean;
  readonly containerBlock: boolean;
}

CAPABILITY_PRESETS

A frozen map of preset name → full CapabilityFlags. Presets are cumulative and keyed to Slack changelog dates:

CapabilityPresetName is the union of the names above, also available as a runtime constant object:

import { CAPABILITY_PRESETS, CapabilityPresetName } from "slackmark";

CAPABILITY_PRESETS[CapabilityPresetName.Conservative]; // all flags false

resolveCapabilities()

function resolveCapabilities(
  input: CapabilityPresetName | CapabilityFlags | CapabilityFlagsPartial | undefined,
  overrides?: CapabilityFlagsPartial,
): CapabilityFlags;

The same resolution convert() applies internally, exported for code that needs the effective flags:

• undefined → latest.
• A preset name → that preset. Unknown names throw ConfigurationError (a typo must not silently enable every capability).
• A full flags object → used as-is.
• A partial flags object → merged over latest.
• overrides → merged over the resolved base, flag by flag.

The result is a frozen object.

import { resolveCapabilities } from "slackmark";

const flags = resolveCapabilities("2025-08", { markdownBlock: false });
// { markdownBlock: false, tableBlock: true, ...rest false }