oven-sh/bun · error · Error

First buffer was modified

Error message

First buffer was modified

What it means

The package list byte range [begin_at, end_at] read from the lockfile header falls outside the declared buffer end or is inverted (begin > end) (src/install/lockfile/Package.rs:3218-3221, re-checked later at 3401-3407).

Source

Thrown at bench/snippets/buffer-concat.mjs:35

      ? new Intl.NumberFormat(undefined, { unit: "megabyte", style: "unit" })
      : size > 1024
        ? new Intl.NumberFormat(undefined, { unit: "kilobyte", style: "unit" })
        : new Intl.NumberFormat(undefined, { unit: "byte", style: "unit" });

  bench(
    `Buffer.concat(${fmt.format(
      Number((size > 1024 * 1024 ? size / 1024 / 1024 : size > 1024 ? size / 1024 : size).toFixed(2)),
    )} x 3)`,
    () => {
      const result = Buffer.concat(buffers);
      if (check) {
        if (result.byteLength != size * 3) throw new Error("Wrong length");
        if (result[0] != 1) throw new Error("Wrong first byte");
        if (result[size] != 2) throw new Error("Wrong second byte");
        if (result[size * 2] != 3) throw new Error("Wrong third byte");

        result[0] = 10;
        if (first[0] != 1) throw new Error("First buffer was modified");

        result[size] = 20;
        if (second[0] != 2) throw new Error("Second buffer was modified");

        result[size * 2] = 30;
        if (third[0] != 3) throw new Error("Third buffer was modified");
      }
    },
  );
}

const chunk = Buffer.alloc(16);
chunk.fill("3");
const array = Array.from({ length: 100 }, () => chunk);
bench("Buffer.concat 100 tiny chunks", () => {
  return Buffer.concat(array);
});

View on GitHub (pinned to 8c5296ac45)

Solutions

1. Restore bun.lockb from version control
2. Otherwise delete it and run `bun install` to rebuild
3. Avoid killing installs mid-save and keep bun.lockb out of filters/merges

When it happens

Trigger: Corrupted offset fields in bun.lockb - partial writes, bit rot, or a file assembled from mismatched pieces.

Common situations: Same corruption class as the other validation failures: interrupted saves, binary merge conflicts, transfer mangling.

Related errors

• Wrong first byte
• Wrong second byte
• Wrong third byte
• not 200
• picsum ${p.id}: ${res.status}

AI-assisted analysis of oven-sh/bun@8c5296ac45 (2026-08-16). Data as JSON: /api/errors/d0651b4b15a06410. Report an issue: GitHub.