Function migrateConfigStep

packages/migration-legacy/src/steps/config.ts:193–487

(input: ConfigStepInput)

}

export async function migrateConfigStep(input: ConfigStepInput): Promise<ConfigStepResult> {
  let oldText: string;
  try {
    oldText = await readFile(sourceConfigToml(input.sourceHome), 'utf-8');
  } catch {
    return emptyResult();
  }

  let parsedRaw: unknown;
  try {
    parsedRaw = parseToml(oldText);
  } catch {
    // Malformed legacy config.toml: skip config migration rather than aborting
    // the whole run. sessions/MCP/history still migrate.
    return emptyResult();
  }
  const parsed: Record<string, unknown> = isRecord(parsedRaw) ? parsedRaw : {};

  // Decide how the target config.toml is handled: a missing or pristine-stub
  // target is overwritten; a parseable user config is merged into; an
  // unparseable target falls back to a side file (it cannot be merged).
  const configPath = targetConfigFile(input.targetHome);
  let targetText: string | undefined;
  try {
    targetText = await readFile(configPath, 'utf-8');
  } catch {
    targetText = undefined;
  }
  let targetMode: 'overwrite' | 'merge' | 'sibling';
  let targetParsed: Record<string, unknown> = {};
  if (targetText === undefined || targetText === DEFAULT_CONFIG_FILE_TEXT) {
    targetMode = 'overwrite';
  } else {
    try {
      const tp: unknown = parseToml(targetText);
      targetParsed = isRecord(tp) ? tp : {};
      targetMode = 'merge';
    } catch {
      targetMode = 'sibling';
    }
  }

  // Provider names available to migrated models: those kept by this run, plus
  // any already present in the target config being merged into.
  const availableProviderNames = new Set<string>(
    isRecord(targetParsed['providers']) ? Object.keys(targetParsed['providers']) : [],
  );

  // Model alias names already present in the target config being merged into —
  // a migrated `default_model` may legitimately point at one of these.
  const availableModelNames = new Set<string>(
    isRecord(targetParsed['models']) ? Object.keys(targetParsed['models']) : [],
  );

  // 1) Providers — keep only those kimi-code's schema accepts.
  const droppedProviders: string[] = [];
  const keptProviders: Record<string, Record<string, unknown>> = {};
  if (isRecord(parsed['providers'])) {