n8n-io/n8n · error · Error

Failed to parse discovery test case ${filePath}: ${error ins

Error message

Failed to parse discovery test case ${filePath}: ${error instanceof Error ? error.message : String(error)}

What it means

Thrown by `parseTestCaseFile()` in data/discovery/index.ts when `JSON.parse()` throws on a discovery test-case file. This is a pure syntax/lexing failure — unmatched braces, trailing commas (forbidden in strict JSON), single-quoted strings, control characters, or a truncated file. The original parse error is appended so the developer sees the JSON-level cause (line/column). Once parsing succeeds, the file is handed to `discoveryTestCaseSchema.safeParse`, which is a different failure path (error 430).

Source

Thrown at packages/@n8n/instance-ai/evaluations/data/discovery/index.ts:70

			}),
		rationale: z.string().optional(),
		maxSteps: z.number().int().positive().optional(),
	})
	.strict();

export interface DiscoveryTestCaseWithFile {
	testCase: DiscoveryTestCase;
	/** Filename without extension, e.g. "slack-oauth-credential-setup" */
	fileSlug: string;
}

function parseTestCaseFile(filePath: string): DiscoveryTestCase {
	const content = readFileSync(filePath, 'utf-8');
	let raw: unknown;
	try {
		raw = JSON.parse(content);
	} catch (error) {
		throw new Error(
			`Failed to parse discovery test case ${filePath}: ${error instanceof Error ? error.message : String(error)}`,
		);
	}
	const parsed = discoveryTestCaseSchema.safeParse(raw);
	if (!parsed.success) {
		const issues = parsed.error.issues
			.map((issue) => `${issue.path.join('.') || '(root)'}: ${issue.message}`)
			.join('; ');
		throw new Error(`Invalid discovery test case ${filePath}: ${issues}`);
	}
	return parsed.data;
}

function parseSubstringList(value: string | undefined): string[] {
	if (!value) return [];
	return value
		.split(',')
		.map((s) => s.trim().toLowerCase())

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Open the file at the path in the error and fix the JSON syntax error cited in the message (line/column from the underlying SyntaxError).
2. Validate with a linter: `npx jsonlint <file>` or your editor's JSON language server to find the exact position.
3. Remove comments, trailing commas, and single quotes; ensure strings use double quotes.
4. If the file was truncated, restore from git: `git checkout HEAD -- <file>`.

Example fix

// before (case.json — invalid)
{
  "id": "slack-setup",
  // trailing comma below:
  "userMessage": "hi",
}
// after
{
  "id": "slack-setup",
  "userMessage": "hi"
}

import { readFileSync } from 'fs';
function tryParseJson(filePath: string): unknown {
  try {
    return JSON.parse(readFileSync(filePath, 'utf-8'));
  } catch (e) {
    throw new Error(`${filePath}: ${(e as Error).message}`);
  }
}

try {
  raw = JSON.parse(content);
} catch (error) {
  // already the path this loader takes — augment with file context
  throw new Error(`Failed to parse discovery test case ${filePath}: ${error instanceof Error ? error.message : String(error)}`);
}

When it happens

Trigger: Hand-edited discovery case file with a trailing comma or comment. A file truncated by a crashed editor or a bad git merge. A file saved as JSONC or JSON5 (this loader uses strict `JSON.parse`). A BOM or CRLF issue on Windows-edited files in rare cases. A copy-paste that introduced smart quotes.

Common situations: Authoring a new discovery case and forgetting JSON's strictness (no comments, no trailing commas). A merge conflict marker left in the file. An editor that auto-inserted a trailing comma.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Invalid discovery test case ${filePath}: ${issues}
• Failed to parse ${label} at ${path}: ${msg}
• Existing manifest at ${manifestPath} is malformed; remove or
• expectedToolInvocations must specify a non-empty `anyOf`, `n
• Nested ${Array.isArray(value) ? 'array' : 'object'} found at

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/753aaa1ad7eda90e. Report an issue: GitHub.