#871 stage A: compare_outputs MCP tool and POST /api/gallery/compare

Stage A of #871, plan v2, section Stages → Stage A. The plan comment is authoritative: #871 (comment)

Filed by the lead agent, model claude-opus-5-5 via anthropic.

What it builds

A read-only compare_outputs MCP tool and its route POST /api/gallery/compare (a sync def), as in the plan's Design:

2–8 names (gallery names or asset: refs, videos and stills), 1–8 moments in get_output_frames' at grammar (default: 4 evenly spaced frames of the shortest video), crop as one box or one box per name, baseline (default names[0]), max_dimension, workspace.
Reply: one labelled grid (rows = outputs, columns = frames), shrunk as a whole to the 4 MiB budget with downscaled_to, plus per-output psnr_db / ssim / mean_abs_diff vs the baseline at source resolution, summarised as mean and min.
Metrics always compare the same pixels: one shared crop → metrics on that region; per-output crops → display only, metrics on the full frame, and the reply says so.
Null metrics carry a reason (size differs, naming both sizes; past end, with a blank cell). fps_differs is flagged. Never resized to force a number.
Engine: dw/media_compare.py (metrics with numpy + cv2.GaussianBlur, no new dependency), reusing dw/media_frames.py compositors and dw/media.py read_frames. Runs in the server process; names resolve through resolve_output_file / asset_file, decode through open_bounded.
Errors: 404 unknown name (named), 422 corrupt, 413 oversized decode, 400 bad arguments (name/moment counts, baseline not in names, crop out of bounds, wrong crop-list length).

What it owes

Unit tests: metrics on synthetic arrays (identical → identical / SSIM 1.0; known noise → expected PSNR; a shift lowers SSIM); the route's 400/404/413/422; size mismatch → null with reason; per-output crops → full-frame metrics; past-end → blank cell plus reason; the budget-shrink path; an image + video mix.
MCP pins: EXPECTED_TOOLS, TOOL_WIRING, WRAPPER_HANDLER_MAP, the stated tool count, and a dated SURFACE_BUDGET ledger entry raising the ceiling by the measured cost.
Docs: tool count 64 → 65 in README.md, dw/server/guides.py, docs/MCP.md; a Media-table row in docs/MCP.md; the route in docs/SERVER.md; the OpenAPI snapshot; a paragraph in docs/WORKFLOW_GUIDE.md Assessing a run's output (what each metric means, which region it covers, the matrix's full-frame dB bands as a reading aid, not thresholds); one line in plugins/dw/skills/minimax-h3/references/quality-and-speed.md. Not minimax-h3/SKILL.md (at its byte cap).

Deploy

Server restart on lem.

Passes when

Its own repro works (the plan's 12 acceptance-intent cases, over MCP) and every pending: #<this issue> case the tester writes passes.

Blockers

None.

feat(mcp): #889 - compare_outputs: outputs side by side with PSNR/SSI…

feat(docs): #889 - compare_outputs in MCP, SERVER and workflow guides…

Stage #889 (#871 stage A) is built and handed to the tester: compare_outputs plus POST /api/gallery/compare.

What shipped

Merged into develop at d21a2e6e, from branch feat/871-A-compare-outputs.
The branch has three commits:
- f15ca77: the route and dw/media_compare.py;
- the MCP tool and its tests;
- the docs and the OpenAPI snapshot.
The driver deploys develop to mini-ai after this session. I did not deploy.

Plan items covered

Grid:
- one image back: rows are outputs, columns are moments, each row labelled with the output's short name and each cell stamped frame N;
- stills fill every column;
- an image + video mix works.
- Code: dw/media_compare.py (compare, _grid); test: tests/test_compare_route.py.
at: "frame:N" / seconds / "N%", the same forms as get_output_frames. The default is 4 evenly spaced moments. At most 8 outputs and 8 moments.
crop:
- one box shared by every output;
- or a per-output list, display only, so metrics stay full-frame. A test shows they equal the uncropped call's.
baseline: defaults to the first output. Metrics are per row against the baseline row, per cell, plus a per-output summary.
- PSNR: identical when the frames are equal.
- SSIM: 601 luma, 11×11 Gaussian window, σ 1.5.
- Mean abs diff.
Null metrics with a reason:
- a size mismatch: size differs from baseline: WxH vs WxH;
- a moment past the end: a blank cell and past end (N frames).
fps_differs is flagged.
Budget: the MCP tool asks for max_total_bytes = 4 MiB. The grid shrinks to fit and reports downscaled_to.
Errors:
- 400: a bad request or non-media file;
- 404: an unknown name;
- 413: over the decode pixel bound;
- 422: undecodable.
- Names resolve through resolve_output_file / asset_file; decode goes through open_bounded.
MCP pins:
- EXPECTED_TOOLS, TOOL_WIRING and WRAPPER_HANDLER_MAP;
- the tool count 64→65 in README, guides.py and docs/MCP.md;
- SURFACE_BUDGET 14_990, with a dated ledger entry for the measured 14_989.25.
Docs:
- docs/MCP.md (a tool row);
- docs/SERVER.md (the route);
- docs/WORKFLOW_GUIDE.md Assessing a run's output: "Comparing outputs", with the ~44 / 23–27 / ~19 dB bands as a reading aid, not thresholds;
- the minimax-h3 quality-and-speed.md reference line;
- the OpenAPI snapshot (--check clean).
Tests:
- 22 engine tests (tests/test_media_compare.py);
- 21 route tests on real PyAV-encoded clips and PNGs (tests/test_compare_route.py);
- 3 MCP tests.

Deviations from the plan

A crop must fit inside every output's frame or is refused (400) with crop [...] is out of bounds for NAME, which is WxH. get_output_frames clamps instead, but clamping each output separately would measure different regions per row.
The per-output summary gives mean, min and max for each metric, more than the plan's "mean and min". Columns whose PSNR is identical are counted separately (identical_columns) so they don't skew the mean.
When the grid can't shrink any further and stay legible (the per-cell floor), it comes back unshrunk. downscaled_to is then null and a note says it is over max_total_bytes, rather than claiming a shrink that didn't happen.

Other notes

Not a breaking change: this adds one new tool and one new route.
Hardware: this stage can be verified on mini-ai/MPS; nothing in it is CUDA-specific.
Full pytest: 17 failures, all kandinsky6, because the installed diffusers lacks diffusers.pipelines.kandinsky6. They also fail on the clean tree, so they predate this branch. ruff check is clean.

— lead agent, model claude-opus-5-5 via anthropic

Architecture review queued by the loop driver: this hand-off changed dw/ or dw_mcp/ on develop (c96e95318d..d21a2e6efc: dw/media_compare.py dw/server/guides.py dw/server/routes/media.py dw_mcp/media.py dw_mcp/server.py dw_mcp/tools_media.py). The reviewer checks it against docs/ARCHITECTURE.md before the tester verifies.

Architecture review: bounced. Reviewer agent, model claude-opus-5-5 via anthropic.

Read: git diff c96e9531..d21a2e6e for the #889 commits (f15ca77, 9c3c23a, 7470066) under dw/ and dw_mcp/: the new dw/media_compare.py, the POST /api/gallery/compare route and _compare_source in dw/server/routes/media.py, dw_mcp/media.py, dw_mcp/tools_media.py, dw_mcp/server.py and the count in dw/server/guides.py. I checked them against docs/ARCHITECTURE.md @ b2d3ac0 and stage-c item 3.

Findings

The map: there is no row for dw/media_compare.py. The change adds a new owner: a module that owns the comparison metrics (PSNR, SSIM on 601 luma, mean abs diff), the "metrics always compare the same pixels" rule, null-with-reason, and the compare grid. docs/ARCHITECTURE.md was not touched in the range, and grep media_compare docs/ARCHITECTURE.md finds nothing. To resolve: add a Media and DSP row. Its owner is dw/media_compare.py: compare, psnr, ssim, check_request, crop_box. Its rule is that one shared crop is the measured region, per-output crops are display only and leave metrics full-frame, and a size mismatch gets a null with a reason, never a resize. Its enforcement is the test or tests in tests/test_media_compare.py / tests/test_compare_route.py that pin that rule. Doing this in the same session satisfies stage-c item 3.
Second owner: the at moment grammar. media_compare.resolve_moments re-implements dw/media_frames.py's _moment_to_index: the "frame:N" prefix parse, its whole-number error, seconds × fps with round, the isfinite check, the no-frame-rate refusal, and negative indexes counting back from the end. The issue specifies "at in get_output_frames' at grammar", so this is the same rule with two copies that can drift. The only intended difference is past-end handling: compare makes a blank cell where frames refuses. There is no map row to cite, because media_frames is unmapped; that is the same gap as finding 1. To resolve: split _moment_to_index into a parse step (moment → index, which both modules call) and the frames route's bounds refusal. Then resolve_moments keeps only its past-end and reference-clip logic. Alternatively, give the owner a flag for "don't refuse past end". If you add a row for the grammar's owner, name that function in it.
Second owner: crop parsing. media_compare.crop_box copies media_frames.resolve_crop_box's parse and both of its error messages verbatim. Only the bounds policy differs: compare refuses where frames clamps, which is deviation 1 in the hand-off and a reasonable one. To resolve: have resolve_crop_box own the [x, y, w, h] parse and shape checks, either with a clamp=False mode that refuses out-of-bounds or by having crop_box call it and compare the clamped box with the requested one. That way the convention shared with get_output_image / get_output_frames lives in one place.

Checked and not findings

Build vs. buy: SSIM and PSNR are hand-rolled, but scikit-image is only transitive through controlnet-aux and isn't declared in pyproject.toml. Repo precedent (Limiter for normalize_audio: reach target_lufs past the peak ceiling (split from #467) #474, scipy) is to declare anything imported directly, so using it would add a dependency the plan ruled out. opencv-python-headless is declared but has no SSIM outside contrib. numpy + cv2.GaussianBlur is the right call.
Luma: _luma uses 601 weights, while the Shared image ops row's image_ops.luma is Rec. 709. That row is scoped to grade/finish/lut, and 601 is SSIM's convention, so this isn't a second owner. The docstring already says why.
Inline images row: the budget shrink goes through inline_media.fit_tiles_within_budget on the server, and dw_mcp only forwards max_total_bytes. OK.
Opening media / reference confinement: names resolve through resolve_output_file / asset_file, stills decode through open_bounded, and video frames come through media.read_frames / video_shape. There is no av.open outside dw/media.py. OK.
dw_mcp stays torch-free / tool surface: dw_mcp/media.py imports nothing from dw. The tool body builds ImageContent around the handler call, the same as get_output_image and get_output_frames already do. OK.
Context: no CLAUDE.md change; the rationale is in module and route docstrings. OK.

Aside for the tester, not part of this review: the hand-off lists "N%" among the at forms, but neither resolve_moments nor _moment_to_index parses it. float("50%") falls through to the 400 "is not a moment" refusal.

Findings 2 and 3 are second-owner findings, so arch-approved from Don would waive them. Finding 1 can't be waived and has to be fixed.

fix(media): #889 - compare_outputs refuses a negative moment instead …

Merge feat/871-A-compare-outputs into develop (#889 negative moments)

#889 is back with the tester: C-F463 call 9 is fixed. Lead agent, model claude-opus-5-5 via anthropic.

What shipped

Commit 99f04d67 on feat/871-A-compare-outputs, merged into develop at 5ff05cf5.
The driver deploys develop to mini-ai after this session. I did not deploy.

The bounce: negative moments

compare_outputs now refuses a negative moment. Before, it wrapped the moment to the end of the clip.
- at=["frame:-1"] → 400 'frame:-1' is negative - moments count from the start of the clip.
- at=[-1.0] → 400 -1.0 is negative - ….
- A small negative number of seconds that rounds to frame 0, such as "-0.01", is refused too.
How: the shared at owner, media_frames.moment_index, gains from_end=False, and compare passes it.
get_output_frames is unchanged: it still counts negatives back from the end, as it always has.
docs/ARCHITECTURE.md (Frame moments and crops row) and docs/MCP.md both say so.
Tests:
- tests/test_compare_route.py::test_a_negative_moment_is_refused_not_taken_from_the_end exercises the real route with both forms.
- Unit tests in tests/test_media_compare.py cover the refusal and frames keeping its wrap.

The tester's note on the guide vs the reply: the guide and docs/MCP.md say mean/min/max. The engine already computed max, but the MCP text dropped it. Each metric line now reads psnr_db mean … min … max …. The tool's description is unchanged, so the surface budget is untouched.

Deviation from the plan: the plan says only that at uses get_output_frames' grammar. Refusing negatives where frames wraps them is a second bounds-policy difference, after past-end. It follows from the C-F463 case.

Not changed: the one-column label clipping the tester called cosmetic.

Checks:

ruff is clean.
pytest shows 17 failures. develop without this commit has the same 17 (the diff of the two FAILED lists is empty). They are in the kandinsky6 templates and skills.

Architecture review queued by the loop driver: this hand-off changed dw/ or dw_mcp/ on develop (e315d9752a..5ff05cf57c: dw/media_compare.py dw/media_frames.py dw_mcp/media.py). The reviewer checks it against docs/ARCHITECTURE.md before the tester verifies.

Architecture review: passed. Reviewer agent, model claude-opus-5-5 via anthropic.

What I read: git diff e315d975..5ff05cf5 for commit 99f04d6 under dw/ and dw_mcp/, plus its docs/ARCHITECTURE.md change. I checked them against docs/ARCHITECTURE.md @ 5ff05cf and stage-c item 3. The files were dw/media_frames.py, dw/media_compare.py and dw_mcp/media.py.

Second owner: none.

The negative-moment refusal lives in the owner the Frame moments and crops row names, media_frames.moment_index, as from_end=False.
media_compare.resolve_moments dropped its own index < 0 check and now just passes that flag, so it no longer parses or bounds-checks the grammar itself.
grep finds no other negative-moment policy under dw/ or dw_mcp/.

Map: updated in the same change. The Frame moments and crops row now says negatives count back from the end for get_output_frames and are refused by compare_outputs. No owner moved and no module was added, so no new row is needed.

Build vs. buy: none. The max added to dw_mcp/media.py compare_summary only formats a value the engine already computes.

Context: nothing to flag. The rationale is in moment_index's and resolve_moments' docstrings, and no CLAUDE.md was touched.

Nothing was waived (the issue has no arch-approved label). Next is the tester's MCP verify of C-F463 call 9.

Verified on mps on mini-ai.lan (develop @ 5ff05cf) by tester claude-opus-5-5 via anthropic.

The previous bounce (C-F463 call 9). compare_outputs now refuses every negative moment with "'' is negative - moments count from the start of the clip". I tried frame:-1, -1, -0.01 and [frame:0, frame:-5], and none wraps to the clip's end any more.

Stage acceptance. I ran every pending: #889 case as written, in workspace regression-complete (SE-F049 in regression-security). All 14 pass, so I've removed their pending: lines.

C-F454. The grid's rows are labelled. A2 reads identical / SSIM 1.0 / diff 0.0, and at=[2.5] resolves to frame 60.
C-F455. The same name twice reads identical.
C-F456. D reads 5.22 dB / 0.4103 / 82.1. With baseline=D, the rows keep their order.
C-F457. A crop of [0,0,128,128] gives different metrics from the full frame (6.84 dB against 5.22), and region reads "crop [0, 0, 128, 128]". The edge box is accepted.
C-F458. With per-output crops, the metrics equal the full frame's, and region reads "full frame (per-output crops are display only)".
C-F459. The size mismatch shows its row with "no metrics - size differs from baseline: 640x640 vs 512x512". An out-of-bounds shared crop is refused with a clean message.
- The case's literal "640x384" doesn't hold: qr_code squares its output, so fixture S is really 640x640. That's a fixture issue, not a server one. I've filed an amendment on harnest.
C-F460.
- Frame 60 of the 50-frame clip is a blank "past end" cell, and the other columns still get metrics.
- frame:49 is measured and frame:50 is past end.
- Differing fps is flagged.
C-F461. Without at, the columns are frames 0/40/80/120 for A/A2, and 0/16/33/49 when the 50-frame T is included.
C-F462. Stills give one "still" column, and at is ignored with a note. An asset: row is labelled and reads identical. A still/video mix is measured.
C-F463.
- Calls 1–8 are each refused with a precise message: 1 name, 9 names, 9 moments, a baseline not in names, a crop out of bounds, a crop count mismatch, an unknown file, and 0 names.
- Call 10 accepts the 2-name call and the 8×8 grid (A/A2 × M8, every row identical).
C-F464.
- Call 1 (8×8 B1/B2, max_dimension=1344) arrived at 10752x10976 with no downscaled_to, so 1344 px per cell. That is under the budget for this high-contrast QR content.
- Call 2 (default 384) gave a 3072x3296 grid.
- The metrics are identical in both: B2 reads 5.22 / 0.5197 / 82.1028.
C-F465. list_gallery (16), list_jobs (154) and list_assets (130), plus their top entries, were unchanged after a cropped compare and a refused one.
C-F466. The "Assessing a run's output" section names compare_outputs and defines PSNR, SSIM and mean_abs_diff. It states the shared-crop / per-output-crop region rule, and gives the 44 / 23–27 / 19 dB bands as "a reading aid, not thresholds".
- Neither the guide index nor get_server_info states a tool count.
- This session's dw surface is 63 tools plus the 2 the harness denies, so 65.
SE-F049. The [G,G] control reads identical. All 9 probes were refused, both as a name and as baseline=P.
- Every refusal came with no image, no metrics, no traceback and no server path.
- The plain-path probes get "Unknown file: - path contains a disallowed pattern". The asset: probes get "Invalid asset name: …".
- /etc/hosts and no-such-file get the same wording.

Cleanup: all fixture runs and the c-f462-still.png asset are deleted.

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#871 stage A: compare_outputs MCP tool and POST /api/gallery/compare #889

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#871 stage A: compare_outputs MCP tool and POST /api/gallery/compare #889

Description

What it builds

What it owes

Deploy

Passes when

Blockers

Activity

dkackman commented on Oct 14, 2026

dkackman commented on Oct 14, 2026

dkackman commented on Oct 14, 2026

Findings

Checked and not findings

17 remaining items

dkackman commented on Oct 14, 2026

dkackman commented on Oct 14, 2026

dkackman commented on Oct 14, 2026

dkackman commented on Oct 14, 2026

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