Engine (crates/engine/src/segment/):
- One worker thread owns the model and the encoded photo; the session
sends jobs (with the render job for the model input) and gets results
over channels, never locking what the model holds. In the app
(Segmenter::background) clicks, descriptions, prepares and detail
passes return at once and Session::segment_poll applies results (one
undo step per settled selection, pending clicks shown on the photo);
the CLI/MCP wait for them. Newer requests for the same selection
supersede queued ones.
- Every job runs under catch_unwind: a candle panic becomes an error and
the model is reloaded next time; busy counters are reset by drop
guards; a dead worker is restarted. The model unloads after 10 min idle.
- segment.model.status / .download {acknowledged: true} / .cancel: the
download runs on its own thread; status via atomics (try_lock only).
Without the model every AI request fails at once with "The SAM 3 model
is not installed…"; renders/exports never need it; `seg` params make
AI masks from stored segmentations without it.
- Hostile documents: at most 4 detail patches per component (capped on
deserialize and in the renderer), at most 64 Object clicks.
UI: Object / Describe without the model open "Download the SAM 3
Model?" (size, folder, SAM License link; Not Now / Download, progress,
cancel, Try Again with the reason, Continue once installed); progress in
the Masking panel when the dialog is closed. Reverted the PR's unrelated
default change (mask overlay off + hover-red) to main's behaviour.
tools/install-sam3.*: --fail so error pages never land in files, 416
restarts instead of looping, the weights are verified before they are
moved into place (a bad file is deleted, never resumed from).
Docs: docs/ai-masks.md (in-app download, mirrors, SAM License summary,
no weights in the repo), NOTICE, parity LR-MASK-OBJECTS, What's New,
ROADMAP.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
AI masks from Meta's SAM 3, run in LightCraft itself: a new
`lightcraft-segment` crate ports the Hugging Face transformers
implementation (Apache-2.0) to candle, on the GPU through Metal on macOS
(CPU elsewhere), with no C/C++ and no `unsafe`.
- Object: click to include, ⌥-click to leave a part out (SAM 3's
interactive prompt encoder + two-way mask decoder).
- Describe: a text prompt selects every instance ("sky", "the red car";
"car, road" merges several) via the CLIP text encoder and DETR detector.
- Both as new masks and as Add / Subtract / Intersect components; + / −
buttons under the selected mask combine selections.
- The segmentation is stored with the mask (288² quantized logits, ~10-30
KB), so renders, exports and the web build never need the model.
- A zoomed-in detail pass (background, ~5 s on an M4 Pro) re-segments the
area around a selection from a sharper source: 5-10x finer edges on
small objects.
- Per-selection Edge slider (hard ↔ soft); hovering a mask in the list
shows it in red (the always-on overlay is now off by default, O toggles).
- The engine feature `sam` (on in the desktop app) gates the model; the
image is encoded once per photo in the background, clicks take ~35 ms.
- Weights are not bundled (SAM License): tools/install-sam3.sh / .ps1
download and verify facebook/sam3; docs/ai-masks.md.
- Clearer errors (missing file, missing model) and a stderr logger in the
app (LIGHTCRAFT_LOG=info).
candle is pinned at 0.9.2: later releases make candle-core depend on
tokenizers with the Oniguruma C library. Every stage is checked against
the Python reference (tests/reference.rs, tools/sam3_reference.py): on
Metal the backbone matches to 7e-5 relative error, masks to ~5e-5.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C8BkS7JDqa1EMcjW6spDGA
Brandon Thomas
Guinther Kovalski