[/diagnose] safePos clips pos to jsonText.length - 1 when the parse error position equals the string length (EOF). This shifts the reported column one character back, which could mislead debugging for truncated or unterminated-string errors. A brief comment explaining the intent would help future readers.

// Clip to last valid index; pos === length (EOF) is safe to round down by one.
const safePos = Math.min(pos, Math.max(0, jsonText.length - 1));

@copilot please address this.

[/diagnose] keyMatch scans all of lineText for the first "key": pattern, regardless of where in the line the error pos falls. For prettified JSON (one key per line) this works fine, but for minified or compacted JSON it could report a key that precedes the actual error position.

const keyMatch = lineText.slice(0, column).match(/"([^"]+)"\s*:\s*$/)
             || lineText.match(/"([^"]+)"\s*:/);

@copilot please address this.

[/tdd] The assertions only verify key and lineText — line and column are part of the returned contract but are unchecked, so regressions in position arithmetic would silently pass.

expect(context?.line).toBe(5);   // "GITHUB_HOST" is on line 5 of invalidConfig
expect(context?.column).toBeGreaterThan(0);

@copilot please address this.

[/tdd] No test covers the null return path — when parseErrorMessage contains no "position N" substring the function silently returns null, but that branch is never exercised.

it("returns null when error message has no position info", () => {
  const context = getJSONParseErrorContext('{"x":1}', 'Unexpected token');
  expect(context).toBeNull();
});

@copilot please address this.