Affected Repositories

• PyAutoGalaxy (primary), PyAutoLens (mirror). PyAutoArray unchanged (phase 1 on main).

Branch Survey

Worktree guard clear. Suggested branch: feature/streaming-p2-fit-save-reload

Implementation Steps

1. autogalaxy/interferometer/fit_interferometer.py: profile_visibilities → None when dataset.transformer is None and no galaxy has a light profile; raise exc.DatasetException if one does; profile_subtracted_visibilities → None when data is None; inversion_with_data returns the inversion itself when data is None. galaxies_to_inversion passes transformer=None through (GalaxiesToInversion.transformer tolerates it).
2. autogalaxy/interferometer/model/analysis.py: extract interferometer_hdu_list_from(dataset) — array-free branch writes mask + nufft_precision_operator + dirty_image_native + dirty_beam_native with EXTNAMEs and header scalars SUM_W, DATA_TERM, NOISE_NORM, N_VIS, EPS, TRANSFORMER_CLASS (plus the mask's own header); in-memory branch unchanged except EXTNAMEs; save_attributes uses it and writes transformer_class only when a transformer exists.
3. autogalaxy/aggregator/interferometer/interferometer.py _interferometer_from: _hdu(hdu_list, name) case-insensitive EXTNAME lookup with positional fallback; terms present → aa.SparseTerms(...) from extensions + header → aa.Interferometer.from_sparse_terms(terms, real_space_mask); else existing path.
4. autolens/interferometer/fit_interferometer.py and autolens/interferometer/model/analysis.py: mirror (reuse the autogalaxy helper for the HDU list).
5. Tests: array-free pixelization-only fit parity (numpy + jit) and light-profile typed error in both repos; save_attributes EXTNAME/header assertions for both dataset kinds; aggregator round trip through af.DirectoryPaths in tmp_path with a minimal fit stub exposing .value(name); red-check the round trip against the unpatched loader.
6. Witness in the PR body: end-to-end AnalysisInterferometer (visualization off), dataset.fits EXTNAME listing and size, reloaded log_evidence equal at 1e-8.

Key Files

• autogalaxy/interferometer/fit_interferometer.py, autogalaxy/interferometer/model/analysis.py, autogalaxy/aggregator/interferometer/interferometer.py
• autolens/interferometer/fit_interferometer.py, autolens/interferometer/model/analysis.py
• test_autogalaxy/interferometer/, test_autolens/interferometer/

Streaming phase 2: pixelization-only fits, save_attributes and aggregator reload on array-free datasets

Type: feature
Target: PyAutoGalaxy
Repos:

• PyAutoGalaxy
• PyAutoLens
  Themes:
• interferometer
• sparse-operator
• memory
  Autonomy: supervised
  Priority: medium
  Status: draft
  Epic: streaming-visibilities
  Phase: 2
  Difficulty: medium
  Consequence: judge
  Witness: a pixelization-only ag.FitInterferometer and al.FitInterferometer on an aa.Interferometer.from_stream dataset evaluate figure_of_merit (numpy and jax.jit) equal to the in-memory sparse fit at rel 1e-8; an AnalysisInterferometer run on it completes, save_attributes writes dataset.fits with SparseTerms FITS extensions (EXTNAME lookup) instead of visibilities, and the aggregator rebuilds the dataset via from_sparse_terms with the sparse operator re-attached so the reloaded fit's log_evidence equals the original at 1e-8.
  Review-minutes: 8
  Unattended: ready
  Parent: draft/feature/autoarray/interferometer_from_stream_array_free_dataset.md
  Blocked-by: none (phase 1 merged 2026-09-30, PyAutoArray#593)

Source: https://github.com/orgs/PyAutoLabs/discussions/13 phase 2, sliced 2026-09-30 (decisions (b), (d)).

What

1. profile_visibilities (ag + al) must not form Visibilities.zeros(N_vis) when transformer is None; galaxies_to_inversion /
   tracer_to_inversion accept a missing transformer (GalaxiesToInversion.transformer already tolerates it).
2. save_attributes (ag interferometer/model/analysis.py ~L216-276; al ~L320-380): when the dataset has no arrays, write
   EXTNAMEs MASK, NUFFT_PRECISION_OPERATOR, DIRTY_IMAGE, DIRTY_BEAM and header scalars SUM_W, DATA_TERM,
   NOISE_NORM, N_VIS, EPS, TRANSFORMER_CLASS; keep the visibility layout (now also EXTNAME-tagged) when arrays exist.
3. autogalaxy/aggregator/interferometer/interferometer.py _interferometer_from (autolens imports it): switch from positional
   HDUs to EXTNAME lookup; rebuild via from_sparse_terms when the terms extensions are present.
4. Tests in test_autogalaxy/interferometer (+ model/analysis save/reload round-trip, which has no test today) and the autolens mirrors.