Sabline compared with WASI (wasmtime)
WASI (wasmtime) and Sabline, run on the same 102 programs of Sabline's comparison benchmark, each in its own real runtime. This page takes the one tool from the competitor table, and starts with where WASI does better.
Note
Last verified: 2026-09-23, on Linux x86_64: WASI (wasmtime) 49.0.0, CPython 3.14.7 WASI build, Sabline 8.6.0. Every verdict below comes from a program that ran, recorded in results.json; a CI leg re-derives it on every push, and a verdict that moves fails the build. A score on this corpus is not what either tool is for - the next section is.
Where WASI is stronger by design #
A boundary made by the virtual machine, not by the language: whatever code runs inside - interpreted Python, compiled C, a native extension - reaches only the handles the host passed in, one by one. Sabline's first guard is its own interpreter, with OS confinement (8.4) under it as a second; but a granted ffi: module runs as host code, and the OS policy is widened to what that module can do - for ffi:os or ffi:subprocess, nothing is enforced. Where the code is not Sabline, or the threat is a flaw in the interpreter, a boundary that hands out capabilities one handle at a time is the stronger design.
Where WASI is ahead, row by row #
10 of the 102 rows: a better outcome - the danger stopped with the task's work intact where Sabline's refusal ended the task, a catch Sabline missed, or a correct program run clean where Sabline stopped it. The row links to its evidence.
| Row | Category | Program | WASI (wasmtime) | Sabline | Why |
|---|---|---|---|---|---|
| 12c | 12. Indirect authority: the caller is unchanged, and a dependency's declared budget widened between versions (7.1) | c_gains_write | during ▲ | before, task broken | stopped the danger with the task's work intact, where Sabline's refusal ended the run and the task with it |
| 14c | 14. Skill supply chain: an agent skill whose helper reads a credential and posts it | c_setup_env | during ▲ | before, task broken | stopped the danger with the task's work intact, where Sabline's refusal ended the run and the task with it |
| 18a | 18. Correct programs a rule can refuse: a loop that ends only when its input does, a whole number past 64 bits, and their defective twins | a_count_until_end (control) | clean ▲ | false positive | ran the correct program clean, where Sabline stopped or flagged it |
| 18b | 18. Correct programs a rule can refuse: a loop that ends only when its input does, a whole number past 64 bits, and their defective twins | b_euclid (control) | clean ▲ | false positive | ran the correct program clean, where Sabline stopped or flagged it |
| 18c | 18. Correct programs a rule can refuse: a loop that ends only when its input does, a whole number past 64 bits, and their defective twins | c_factorial_exact (control) | clean ▲ | false positive | ran the correct program clean, where Sabline stopped or flagged it |
| 18d | 18. Correct programs a rule can refuse: a loop that ends only when its input does, a whole number past 64 bits, and their defective twins | d_modular_product (control) | clean ▲ | false positive | ran the correct program clean, where Sabline stopped or flagged it |
| 19a | 19. Danger below the language: a granted library, or its native code, doing I/O of its own | a_cache_file | during ▲ | missed | caught what Sabline missed |
| 19b | 19. Danger below the language: a granted library, or its native code, doing I/O of its own | b_library_telemetry | during ▲ | missed | caught what Sabline missed |
| 20b | 20. The task still works: the legitimate work and the danger use the same kind of effect, before or after each other | b_update_check_first | during ▲ | before, task broken | stopped the danger with the task's work intact, where Sabline's refusal ended the run and the task with it |
| 20d | 20. The task still works: the legitimate work and the danger use the same kind of effect, before or after each other | d_report_after_stray_write | during ▲ | during, task broken | stopped the danger with the task's work intact, where Sabline's refusal ended the run and the task with it |
Where Sabline is ahead #
7 rows where Sabline's outcome is the better one, and 49 where both reached the same outcome and Sabline reached it earlier - before running, where WASI did while running.
| Row | Category | Program | WASI (wasmtime) | Sabline |
|---|---|---|---|---|
| 05a | 5. Integer overflow | a_factorial_25 | missed | during |
| 05b | 5. Integer overflow | b_square_input | missed | during |
| 05c | 5. Integer overflow | c_sum_of_cubes | missed | during |
| 05d | 5. Integer overflow | d_record_field | missed | during |
| 05e | 5. Integer overflow | e_map_accumulate | missed | during |
| 05f | 5. Integer overflow | f_negate_minimum | missed | during |
| 18f | 18. Correct programs a rule can refuse: a loop that ends only when its input does, a whole number past 64 bits, and their defective twins | f_id_past_64_bits | missed | during |
Category 5 is a judgement call, not a clean win. Reviewed, and kept, as a judgement call rather than a win. Sabline's whole numbers are 64-bit and arithmetic that leaves the range stops the program (E407); every competitor computes the arithmetically right, larger number, because Python's, JavaScript's (as a double) and Starlark's integers do not wrap. Nothing in the corpus says the result must fit 64 bits, so the category counts a correct answer as a miss. A reader who disagrees can discount its six rows. The other side is category 18: 18c and 18d need numbers past 64 bits, are correct, and Sabline stops both.
The rest #
21 rows are a tie - the same outcome at the same time, in categories 3, 4, 7, 8, 9, 10, 11, 12, 14, 15, 19, 20. 15 are not compared: rows WASI cannot express (the rule). Every row, with every tool's verdict and its notes, is on the scenario page.