oven-sh/bun · error · Error

Wrong first byte

Error message

Wrong first byte

What it means

Validation of the binary lockfile's package section rejected the list length header: it exceeds u32::MAX - 1, an impossible package count (src/install/lockfile/Package.rs:3191-3193). The check exists to refuse absurd allocations before trusting the header.

Source

Thrown at bench/snippets/buffer-concat.mjs:30

  const buffers = [first, second, third];

  const fmt =
    size > 1024 * 1024
      ? 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");

View on GitHub (pinned to 8c5296ac45)

Solutions

1. Restore bun.lockb from git
2. Otherwise delete it and run `bun install` to regenerate

When it happens

Trigger: A bun.lockb whose length field is random/garbage bytes - e.g. a non-lockfile file at that path, severe corruption, or a file mangled in transfer.

Common situations: Binary merge damage, wrong file committed as bun.lockb, storage corruption.

Related errors

• Wrong second byte
• Wrong third byte
• First buffer was modified
• not 200
• picsum ${p.id}: ${res.status}

AI-assisted analysis of oven-sh/bun@8c5296ac45 (2026-08-16). Data as JSON: /api/errors/2592bbcce16be9cc. Report an issue: GitHub.