Code	Origin	Repair primitive	Retry budget
`T0_CHECKERBOARD`	Imagen/Gemini rendering fake transparency	Route change → `gpt-image-1` (`background:"transparent"`), Ideogram v3 (`style:"transparent"`), Recraft V3	2
`T0_ALPHA_MISSING`	RGB-only output on transparency-required asset	Matte via `asset_remove_background` (BiRefNet preferred, RMBG fallback)	1
`T0_DIMENSIONS`	wrong `width`/`height` API params	Fix params, regenerate	1
`T0_SAFE_ZONE`	subject bleeds outside platform center	Regenerate with explicit `"centered with 20% padding on all sides"`	1
`T0_FILE_SIZE` (SVG)	path count blows budget	`asset_save_inline_svg` → SVGO → K-means color reduction → vtracer	1
`T0_DCT_ENTROPY`	solid-color / NSFW-filter hit	Regenerate same params once; if repeats, change prompt	1
`T1_PALETTE_DRIFT`	model ignored hex constraint	Recraft with `controls.colors` or recolor post-process (K-means remap in LAB)	1
`T1_TEXT_MISSPELL`	diffusion garbled wordmark	Drop text, composite SVG type (retry Ideogram 3 if text-only asset)	0 in-diffusion / 1 on Ideogram
`T1_LOW_CONTRAST`	pale palette at 16×16 or over background	Regenerate with explicit contrast instruction; else post-boost luminance	2
`T1_VQASCORE`	prompt-image alignment weak	Defect area <15% → inpaint; else full regenerate	2
`T2_BRAND_DRIFT`	style diverges from brand refs	Seed sweep (N=4, rank by CLIPScore + HPSv2); augment brand bundle	1
`T2_COMPOSITION`	off-center, cluttered, poor whitespace	img2img at low denoise (0.35) — preserves layout, fixes style	1

When a budget exhausts: stop retrying, report to user with diagnostic payload. Do not loop.

Diagnosis tree

asset_validate() returns warnings[]
   └─ for each warning:
      ├─ read code + affected tier
      ├─ classify failure class:
      │    local   (<15% image area)         → inpaint / post-process
      │    global  (style/palette-wide)      → route change / regenerate
      │    compositional (safe-zone/framing) → regenerate with centering prompt
      └─ select repair primitive (table above)
         ├─ apply
         ├─ re-validate
         └─ if same code fires again:
              ├─ retry_count < budget → try next primitive in fallback chain
              └─ retry_count ≥ budget → escalate to user

Repair primitives — cost / ROI

Primitive	Cost relative to 1× generation	When to choose
SVGO / palette remap / recolor	0.01–0.05×	Deterministic fix, no model call
Matte (BiRefNet / RMBG)	0.05×	alpha missing, no regeneration needed
Inpaint (masked edit)	0.3×	defect area <15%, composition is right
img2img low-denoise	1×	global style drift, preserve layout
ControlNet tile reinjection	1.5×	preserve structure, regen detail
Full regenerate	4×	architectural failure (checkerboard, wrong model)
Seed sweep (N=4)	4× + selection	brand drift, pick best

Prefer cheaper primitives first when they apply.

Route-change rules for architectural failures

Symptom	Current route	Change to
Checkerboard	Imagen / Gemini	`gpt-image-1` (first), Ideogram v3, Recraft V3
Wordmark garbled	any diffusion	Ideogram 3 Turbo (first), `gpt-image-1` (second), composite SVG (always works)
Palette drift after 2 tries	any	Recraft (hard palette lock via `controls.colors`)
Subject misrendered	SDXL	Flux.1 [dev], `gpt-image-1`
Path count >200 on SVG	Recraft SVG	inline_svg mode + strict path budget

Proactive (pre-generation) checks

Prevent 70% of failures by validating the brief before calling asset_generate_*:

BRIEF:
☐ asset_type in closed enum (logo|app_icon|favicon|og_image|splash_screen|
                             illustration|icon_pack|sticker|hero|transparent_mark)
☐ subject noun concrete (not just adjectives)
☐ prompt ≥ 10 words OR brand_bundle provides style refs

TEXT-IN-IMAGE:
☐ quoted string ≤ 12 chars? else composite SVG type
☐ string > 5 words? force composite, skip diffusion-text path

PALETTE:
☐ brand.palette provided?
☐ hex codes ≤ 4 (over-constraint degrades Flux/SDXL)

TRANSPARENCY:
☐ transparency required + model in [Imagen, Gemini]?   → reroute
☐ transparency required + gpt-image-1?                  → set API `background:"transparent"`
☐ transparency required + Flux/SDXL?                    → plan post-matte

ROUTING:
☐ text required + model ≠ Ideogram/gpt-image-1?         → suggest reroute
☐ native SVG needed + model ≠ Recraft?                  → suggest Recraft or inline_svg

Where the codes come from

asset_validate (and every generator that runs a tier-0 pass before returning) emits the codes as a structured array:

{
  "pass": false,
  "warnings": [...],
  "failures": [
    { "code": "T0_CHECKERBOARD", "tier": 0, "detail": "checkerboard pattern detected in 42.7% of analyzed pixels; reject and route to native-RGBA provider", "data": { "ratio": 0.427 } },
    { "code": "T1_PALETTE_DRIFT", "tier": 1, "detail": "...", "data": { "avg_delta_e2000": 14.2, "threshold": 10 } }
  ],
  "tier0": { "width": 1024, "height": 1024, "has_alpha": false, ... }
}

Read validations.failures (when consuming an AssetBundle) or the top-level failures (when calling asset_validate directly). The data field on each failure carries enough context (bbox coords, ΔE value, Levenshtein distance) to pick a repair primitive without re-running the check. Source: packages/mcp-server/src/pipeline/validate.ts, ValidationFailure type in types.ts.

Integration with systematic debugging

Four-phase loop per failure:

Gather evidence — read validate output; log model, seed, guidance, prompt_hash.
Pattern analysis — match to failure code; classify local/global/compositional.
Hypothesis — pick cheapest repair primitive from the matrix.
Verify — re-validate; if same code recurs, step down the route-change ladder, not the same primitive.

Red flags (stop, escalate):

Same failure code 3+ times in a row
Two different route changes failed for the same asset
Cascading repairs (matte → vectorize → safe-zone) — brief is structurally wrong

Evidence to log per pipeline boundary

GENERATION:   model, seed, guidance_scale, num_steps, prompt_hash, latency_ms, status
MATTE:        tool (birefnet|rmbg|difference), alpha_px_before, alpha_px_after, checker_probe
VECTORIZE:    path_count_before, path_count_after, color_count, tool (recraft|vtracer|potrace)
EXPORT:       variants[].{path, format, w, h, size_bytes}
VALIDATE:     tier0{...}, tier1{palette_de: x, vqa: y, ocr_lev: z}, tier2{sim: w}

Research

docs/research/14-negative-prompting-artifacts/14b-artifact-taxonomy.md — taxonomy + origin points
docs/research/14-negative-prompting-artifacts/14c-regenerate-vs-repair-strategies.md — primitives, cost/time tradeoffs
docs/research/03-evaluation-metrics/3e-asset-specific-eval.md — VQAScore, OCR, WCAG, CSD thresholds
docs/research/24-skills-for-p2a/06-validation-debug-skill.md — full design spec

asset-validation-debug

Asset validation + repair

Failure code → repair table