validation failed - requirement present in multiple…

Error message

${specName} validation failed - requirement present in multiple sections (${c.a} and ${c.b}) for header "### Requirement: ${c.name}"

What it means

Pre-validation in buildUpdatedSpec: the same normalized requirement name appears in two different delta sections (e.g. ADDED and REMOVED), which the conflicts list records pairwise. The first conflict is reported; applying both operations to one requirement is contradictory.

Solutions

Keep the requirement in only one delta section and remove it from the other
If it was replaced, express that as MODIFIED rather than ADDED+REMOVED

Defensive patterns

Strategy: validation

When it happens

Trigger: Thrown at src/core/specs-apply.ts:289 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Fission-AI/OpenSpec@6926ccb18a (2026-08-25). Data as JSON: /api/errors/846313fe98edbe48. Report an issue: GitHub.

Appendix: source

Thrown at src/core/specs-apply.ts:289

        `${specName} validation failed - requirement present in multiple sections (RENAMED and REMOVED) for header "### Requirement: ${from}"` +
          (removedFoldMatch === fromNorm ? '' : ` (REMOVED spells it "${removedFoldMatch}")`)
      );
    }
    if (modifiedNames.has(fromNorm)) {
      throw new Error(
        `${specName} validation failed - when a rename exists, MODIFIED must reference the NEW header "### Requirement: ${to}"`
      );
    }
    // Detect ADDED colliding with a RENAMED TO
    if (addedNames.has(toNorm)) {
      throw new Error(
        `${specName} validation failed - RENAMED TO header collides with ADDED for "### Requirement: ${to}"`
      );
    }
  }
  if (conflicts.length > 0) {
    const c = conflicts[0];
    throw new Error(
      `${specName} validation failed - requirement present in multiple sections (${c.a} and ${c.b}) for header "### Requirement: ${c.name}"`
    );
  }
  const hasAnyDelta = plan.added.length + plan.modified.length + plan.removed.length + plan.renamed.length > 0;
  if (!hasAnyDelta) {
    throw new Error(
      `Delta parsing found no operations for ${update.id}. ` +
        `Provide ADDED/MODIFIED/REMOVED/RENAMED sections in change spec.`
    );
  }

  // Load or create base target content
  const deltaPurpose = extractPurposeSection(changeContent);
  let targetContent: string;
  let isNewSpec = false;
  assertTrustedSpecPath(update.targetRoot, update.target);
  try {
    targetContent = await fs.readFile(update.target, 'utf-8');

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