MakerWorld 3MFs sliced for P2S (and likely other Bambu printers) ship
project_settings.config entries with "-1" on fields BambuStudio writes
to mean "inherit from the parent process preset". The headless slicer
CLI's StaticPrintConfig validator runs against the embedded settings
*before* --load-settings overrides apply, so the sentinel trips the
field's lower-bound check and the CLI exits non-zero before the supplied
profile triplet is consulted. Both slice paths (with-profiles and the
embedded-settings fallback) read the same config and fail the same way,
so the user surfaces the error.
Surgical fix: open Metadata/project_settings.config, remove allowlisted
keys when their value is exactly "-1", re-zip. Allowlist starts with the
two from this report (raft_first_layer_expansion, tree_support_wall_count)
plus prime_tower_brim_width (a known sentinel cited in earlier reports).
Non-allowlisted "-1" values are left alone so a blanket strip can't
corrupt legitimate negative values. Other zip entries pass through
byte-identical — no risk of the failure mode the previous full-strip
experiment hit (silent CLI exit on initialisation).
Sanitiser runs before both slice_with_profiles and slice_without_profiles
paths since both fail on the same sentinel.
13 new unit tests in test_project_settings_sentinel_sanitiser.py cover
the allowlist removal contract (parametrised across all sentinel keys),
preservation of unaffected values, byte-identical round-trip of unrelated
zip entries, and defensive fallbacks for non-zip / malformed / no-config
inputs.
Adding new sentinel keys is one-line: append to
_PROJECT_SETTINGS_SENTINEL_KEYS in library.py.
maziggy
aecf8283b5