fix(llamaswap): use A1111 /sdapi/v1/txt2img so seed is honored

The OpenAI /v1/images/generations endpoint ignores `seed` on our
stable-diffusion.cpp build — every render of a given prompt comes back
byte-identical, so a drawbot batch of N collapsed to one image. Switch the
image provider to sd-server's A1111 /sdapi/v1/txt2img endpoint, which honors
`seed` (verified live: distinct seeds -> distinct images on SDXL and
Qwen-Image). Size is split into width/height; llama-swap still routes by the
`model` field. Tests + ADR-0016 updated.

.gitea/workflows/adversarial-review.yml

@@ -1,12 +1,8 @@
-# Gadfly — agentic adversarial PR reviewer (https://gitea.stevedudenhoeffer.com/steve/gadfly).
-#
-# Runs the published Gadfly image (pinned to an immutable :sha- tag — act_runner
-# caches :latest, and this build is what carries foreman provider-type support)
-# as a specialist swarm and posts
-# ONE consolidated review comment as gitea-actions. Advisory only — never blocks a
-# merge. This reviews majordomo PRs with 9 ollama-cloud models + the M5 Mac
-# (3-lens suite). Gadfly is a simple system — findings are advisory; always
-# double-check before acting.
+# Gadfly adversarial review — subscribes to steve/gadfly's reusable workflow and
+# INHERITS its default swarm. This stub holds only the triggers, the actor gate,
+# secret forwarding, and the allow-list; the swarm config (models, lenses,
+# concurrency, timeouts) lives centrally in gadfly's review-reusable.yml so it is
+# tuned in ONE place. Advisory only — never blocks a merge.
 
 name: Adversarial Review (Gadfly)
 
@@ -33,60 +29,26 @@ concurrency:
 jobs:
   review:
     # Security: only trusted users may trigger a secret-bearing run via a PR
-    # comment (pull_request + workflow_dispatch are already trusted). Mirrors
-    # GADFLY_ALLOWED_USERS, the in-container belt-and-suspenders check.
+    # comment (pull_request + workflow_dispatch are already trusted). Mirrors the
+    # allowed_users input below (the in-container belt-and-suspenders check) — both
+    # lists must stay in sync; a workflow if: can't read a workflow_call input.
     if: >-
       github.event_name != 'issue_comment'
       || (github.event.issue.pull_request
           && (github.actor == 'steve'
               || github.actor == 'fizi'
               || github.actor == 'dazed'))
-    runs-on: ubuntu-latest
-    # Fleet: 9 cloud (lens fan-out) + the M5 Mac via foreman. The slow local
-    # lane dominates wall time, so allow plenty of headroom. (M1 was dropped —
-    # consistently slow for zero real findings.)
-    timeout-minutes: 90
-    steps:
-      - uses: docker://gitea.stevedudenhoeffer.com/steve/gadfly:sha-d7f364d
-        env:
-          GITEA_API: ${{ github.server_url }}/api/v1/repos/${{ github.repository }}
-          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
-          OLLAMA_CLOUD_API_KEY: ${{ secrets.OLLAMA_CLOUD_API_KEY }}
-          # Local Mac, reached through its foreman queue (native Ollama on the
-          # wire). GADFLY_ENDPOINT_M5 registers provider "m5", a foreman-preset
-          # Ollama client at the secret's URL, of the form:
-          #   foreman|https://<foreman-host>|<token>
-          # Needs an image with foreman provider-type support (this one). If the Mac
-          # is offline that model's comment shows an error and the others still post.
-          # (Gitea secrets aren't auto-exposed — map each explicitly.)
-          GADFLY_ENDPOINT_M5: ${{ secrets.GADFLY_ENDPOINT_M5 }}
-          # Fleet: 9 cloud + M5 Max. Cloud concurrency lives in the LENSES: cloud
-          # models run a few at a time (ollama-cloud=3) with their 3 lenses
-          # concurrent (LENS ollama-cloud=3) so comments land sooner; the Mac runs
-          # one model, lenses serial (its foreman queue serializes anyway). Both
-          # provider lanes run parallel.
-          GADFLY_MODELS: "minimax-m3:cloud,glm-5.2:cloud,glm-5.1:cloud,kimi-k2.7-code:cloud,deepseek-v4-pro:cloud,nemotron-3-super:cloud,gpt-oss:120b-cloud,qwen3-coder:480b-cloud,gemma4:cloud,m5/qwen3.6:35b-mlx"
-          GADFLY_PROVIDER_CONCURRENCY: "ollama-cloud=3,m5=1"
-          GADFLY_PROVIDER_LENS_CONCURRENCY: "ollama-cloud=3"
-          # Default => the 3-lens suite (security, correctness, error-handling).
-          # Set the repo var GADFLY_SPECIALISTS to override (csv / "all" / "auto").
-          GADFLY_SPECIALISTS: ${{ vars.GADFLY_SPECIALISTS || 'security,correctness,error-handling' }}
-          # Per-lens deadline + bounded steps so the slow local models stay sane.
-          GADFLY_TIMEOUT_SECS: "600"
-          GADFLY_MAX_STEPS: "14"
-          # Allow-list for the comment trigger (mirrors the job-level if: guard).
-          GADFLY_ALLOWED_USERS: "steve,fizi,dazed"
-          # --- findings telemetry: POST runs + findings to the gadfly-reports store ---
-          # Advisory & off unless GADFLY_FINDINGS_URL is set; failures only log to
-          # stderr and never affect the review. GADFLY_REPO / GADFLY_PR are derived
-          # in-container; the URL + token are user-scope secrets.
-          GADFLY_FINDINGS_URL: ${{ secrets.GADFLY_FINDINGS_URL }}
-          GADFLY_FINDINGS_TOKEN: ${{ secrets.GADFLY_FINDINGS_TOKEN }}
-          # --- event context (leave as-is) ---
-          EVENT_NAME: ${{ github.event_name }}
-          PR: ${{ github.event.pull_request.number || github.event.issue.number || github.event.inputs.pr_number }}
-          PR_BRANCH: ${{ github.head_ref }}
-          IS_DRAFT: ${{ github.event.pull_request.draft }}
-          COMMENT_BODY: ${{ github.event.comment.body }}
-          COMMENT_ID: ${{ github.event.comment.id }}
-          ACTOR: ${{ github.actor }}
+    # Tracks gadfly's v1 release tag — a curated pointer re-moved on each release
+    # (unlike @main, which moves on every push). Central swarm tuning propagates
+    # here automatically; the tradeoff vs a full sha pin is that v1 is mutable.
+    uses: steve/gadfly/.gitea/workflows/review-reusable.yml@7bc3c982fa7b72367034c673f7812bf05e9c503e
+    # Least privilege: forward only the review secrets (not `secrets: inherit`,
+    # which would expose every repo secret). GITEA_TOKEN is the automatic token.
+    secrets:
+      OLLAMA_CLOUD_API_KEY:    ${{ secrets.OLLAMA_CLOUD_API_KEY }}
+      CLAUDE_CODE_OAUTH_TOKEN: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
+      GADFLY_FINDINGS_URL:     ${{ secrets.GADFLY_FINDINGS_URL }}
+      GADFLY_FINDINGS_TOKEN:   ${{ secrets.GADFLY_FINDINGS_TOKEN }}
+    with:
+      # Consumer-specific allow-list; everything else is inherited.
+      allowed_users: "steve,fizi,dazed"

CLAUDE.md

@@ -142,9 +142,11 @@ Ship work through PRs and let Gadfly review it before merge:
 
 - **Push to a PR, never straight to `main`.** Branch, push, open a PR.
   `.gitea/workflows/adversarial-review.yml` runs Gadfly (the standalone
-  agentic adversarial reviewer) — a fleet of 9 ollama-cloud models +
-  the M5 Mac via foreman, each running the 3-lens suite (security,
-  correctness, error-handling). Advisory only; it never blocks the merge.
+  agentic adversarial reviewer) by subscribing to gadfly's reusable workflow
+  and inheriting its default swarm — 3 cloud models + the Claude Code engine
+  (sonnet/opus/opus:max), each running the 5-lens suite (security, correctness,
+  maintainability, performance, error-handling). The swarm is tuned centrally
+  in gadfly, not here. Advisory only; it never blocks the merge.
 - **Wait for Gadfly to finish, then read its output.** Don't merge while the
   review is still running. Each model posts one consolidated comment; weigh
   every finding on its merits and fix the real ones (Gadfly is a simple

docs/adr/0016-imagegen-interface.md

@@ -42,3 +42,22 @@ asked for "a new ai image interface as opposed to llm".
   callers (additive fields/options).
 - No health/failover for image models yet; if needed it can be added as a
   separate chain type rather than retrofitting the chat chain.
+
+## Update — optional per-request settings
+
+`Request` gained additive optional overrides — `Steps *int`, `CFGScale *float64`,
+`NegativePrompt string`, `Sampler string`, `Seed *int64` — with mirror options
+(`WithSteps`, …). nil/"" means "leave the backend's per-model default", so the v1
+contract is unchanged for callers that don't set them. `provider/llamaswap`
+forwards them to sd-server as `steps`/`cfg_scale`/`negative_prompt`/`sample_method`/
+`seed` (omitempty). This realizes the "seeds/steps … additive fields" note above;
+img2img/masks/streaming remain deferred.
+
+## Update — A1111 txt2img endpoint (seed support)
+
+`provider/llamaswap` now POSTs to sd-server's **`/sdapi/v1/txt2img`** (A1111)
+instead of the OpenAI `/v1/images/generations`. That OpenAI endpoint **ignores
+`seed`** on the stable-diffusion.cpp build we run — every render of a prompt is
+byte-identical, so a batch of N collapses to one image. `/sdapi/v1/txt2img`
+honours `seed`, restoring real per-render variety. llama-swap still routes by
+the `model` field in the body; `Size` is split into `width`/`height`.

imagegen/imagegen.go

@@ -38,6 +38,29 @@ type Request struct {
 	// Size is the requested resolution, e.g. "512x512" or "1024x1024";
 	// "" = provider default.
 	Size string
+
+	// The fields below are optional per-request overrides. Their zero value
+	// (nil pointer or empty string) means "leave the backend's own default" —
+	// for stable-diffusion.cpp that is the per-model default baked into the
+	// llama-swap launch flags. A caller overrides only what it explicitly sets.
+
+	// Steps is the number of diffusion steps; nil = backend default.
+	Steps *int
+
+	// CFGScale is the classifier-free-guidance scale; nil = backend default.
+	// Architecture-sensitive (SDXL likes ~7, Flux wants 1), so prefer leaving
+	// it nil unless the caller knows the target model.
+	CFGScale *float64
+
+	// NegativePrompt steers generation away from concepts; "" = none.
+	NegativePrompt string
+
+	// Sampler selects the sampling method (e.g. "euler", "euler_a");
+	// "" = backend default.
+	Sampler string
+
+	// Seed fixes the RNG seed for reproducible output; nil = random.
+	Seed *int64
 }
 
 // Result is the canonical image-generation result.
@@ -60,6 +83,21 @@ func WithN(n int) Option { return func(r *Request) { r.N = n } }
 // WithSize sets the requested resolution (e.g. "1024x1024").
 func WithSize(size string) Option { return func(r *Request) { r.Size = size } }
 
+// WithSteps overrides the number of diffusion steps.
+func WithSteps(n int) Option { return func(r *Request) { r.Steps = &n } }
+
+// WithCFGScale overrides the classifier-free-guidance scale.
+func WithCFGScale(s float64) Option { return func(r *Request) { r.CFGScale = &s } }
+
+// WithNegativePrompt sets a negative prompt.
+func WithNegativePrompt(s string) Option { return func(r *Request) { r.NegativePrompt = s } }
+
+// WithSampler overrides the sampling method (e.g. "euler", "euler_a").
+func WithSampler(s string) Option { return func(r *Request) { r.Sampler = s } }
+
+// WithSeed fixes the RNG seed for reproducible output.
+func WithSeed(seed int64) Option { return func(r *Request) { r.Seed = &seed } }
+
 // Apply returns a copy of the request with all options applied. Providers call
 // this once at the top of Generate.
 func (r Request) Apply(opts ...Option) Request {

media/media.go

@@ -5,10 +5,16 @@
 // already satisfies the target's llm.Capabilities. Images that do not fit
 // are decoded, downscaled (never upscaled), and re-encoded into an allowed
 // format and byte budget. Anything that cannot honestly be made to fit —
-// undecodable formats, impossible byte budgets, too many images, images for
-// a text-only target — fails with an error wrapping llm.ErrUnsupported so a
-// failover chain can advance to a more capable target without a health
-// penalty.
+// undecodable formats, impossible byte budgets, images for a text-only
+// target — fails with an error wrapping llm.ErrUnsupported so a failover
+// chain can advance to a more capable target without a health penalty.
+//
+// Over-count is the exception: a request carrying more images than
+// MaxImagesPerReq does NOT fail — the oldest images are replaced with a short
+// text placeholder and the most-recent MaxImagesPerReq are kept, because a hard
+// refuse exhausts a chain whose targets share the same cap (e.g. an agent loop
+// accumulating a preview image per iteration). MaxImagesPerReq remains the
+// per-model knob (0 = no image support).
 //
 // Why a separate package: every provider would otherwise duplicate the same
 // decode/scale/encode pipeline. Providers keep only a cheap capability
@@ -52,15 +58,21 @@ func Normalize(req llm.Request, caps llm.Capabilities) (llm.Request, error) {
 	if !caps.SupportsImages() {
 		return llm.Request{}, fmt.Errorf("media: %w: target does not accept image input (request carries %d image(s))", llm.ErrUnsupported, total)
 	}
-	// Why error instead of dropping the overflow: silently removing an image
-	// changes the question the caller asked; the honest move is to refuse and
-	// let a chain try a roomier target.
+	// Over-cap images are elided in the same copy-on-write pass below: the
+	// OLDEST excess are replaced with a placeholder and the most-recent
+	// MaxImagesPerReq kept (see the package doc for why we elide rather than
+	// refuse). toElide is how many of the first images, front-to-back, to drop.
+	toElide := 0
 	if total > caps.MaxImagesPerReq {
-		return llm.Request{}, fmt.Errorf("media: %w: request carries %d images, target allows at most %d per request", llm.ErrUnsupported, total, caps.MaxImagesPerReq)
+		toElide = total - caps.MaxImagesPerReq
 	}
 
+	// Single copy-on-write pass: for each image, the first toElide become a text
+	// placeholder; the rest are size-normalized against caps. The Messages slice
+	// and an affected message's Parts slice are copied at most once.
 	out := req
 	copiedMessages := false
+	seen := 0
 	for mi := range req.Messages {
 		copiedParts := false
 		for pi, part := range req.Messages[mi].Parts {
@@ -68,13 +80,22 @@ func Normalize(req llm.Request, caps llm.Capabilities) (llm.Request, error) {
 			if !ok {
 				continue
 			}
-			norm, changed, err := normalizeImage(ip, caps)
-			if err != nil {
-				return llm.Request{}, fmt.Errorf("media: message %d, part %d: %w", mi, pi, err)
-			}
-			if !changed {
-				continue
+			seen++
+
+			var replacement llm.Part
+			if seen <= toElide {
+				replacement = llm.Text(imageOverflowPlaceholder)
+			} else {
+				norm, changed, err := normalizeImage(ip, caps)
+				if err != nil {
+					return llm.Request{}, fmt.Errorf("media: message %d, part %d: %w", mi, pi, err)
+				}
+				if !changed {
+					continue
+				}
+				replacement = norm
 			}
+
 			if !copiedMessages {
 				out.Messages = make([]llm.Message, len(req.Messages))
 				copy(out.Messages, req.Messages)
@@ -86,12 +107,17 @@ func Normalize(req llm.Request, caps llm.Capabilities) (llm.Request, error) {
 				out.Messages[mi].Parts = parts
 				copiedParts = true
 			}
-			out.Messages[mi].Parts[pi] = norm
+			out.Messages[mi].Parts[pi] = replacement
 		}
 	}
 	return out, nil
 }
 
+// imageOverflowPlaceholder replaces an image elided to fit a target's
+// per-request image cap. It keeps the message turn intact and tells the model
+// an earlier image was omitted rather than silently changing the conversation.
+const imageOverflowPlaceholder = "[earlier image omitted to fit this model's per-request image limit]"
+
 // Info reports an image part's sniffed format ("jpeg", "png", "gif", or
 // "webp") and pixel dimensions. It is a cheap metadata read — the pixels are
 // never decoded. webp is recognized by signature but not decodable with the

media/media_test.go

@@ -149,18 +149,48 @@ func TestNormalizeImagesUnsupported(t *testing.T) {
 	}
 }
 
-func TestNormalizeTooManyImages(t *testing.T) {
-	img := llm.Image("image/png", encPNG(t, gradient(4, 4)))
+func TestNormalizeOverCount(t *testing.T) {
+	// 3 distinguishable images across 2 messages; cap = 2. Over-count no longer
+	// errors — the OLDEST image is replaced with a placeholder and the most-recent
+	// two (the relevant ones in an iterative run) are kept, in order.
+	a := llm.Image("image/png", encPNG(t, gradient(2, 2))).(llm.ImagePart)
+	b := llm.Image("image/png", encPNG(t, gradient(4, 4))).(llm.ImagePart)
+	c := llm.Image("image/png", encPNG(t, gradient(8, 8))).(llm.ImagePart)
 	req := llm.Request{Messages: []llm.Message{
-		llm.UserParts(img, img),
-		llm.UserParts(img),
+		llm.UserParts(a, b),
+		llm.UserParts(c),
 	}}
-	_, err := Normalize(req, llm.Capabilities{MaxImagesPerReq: 2})
-	if !errors.Is(err, llm.ErrUnsupported) {
-		t.Fatalf("err = %v, want ErrUnsupported", err)
+	caps := llm.Capabilities{MaxImagesPerReq: 2, MaxImageDimension: 64, MaxImageBytes: 1 << 20, AllowedImageMIME: []string{"image/png"}}
+	out, err := Normalize(req, caps)
+	if err != nil {
+		t.Fatalf("over-count should not error: %v", err)
 	}
-	if !strings.Contains(err.Error(), "3 images") || !strings.Contains(err.Error(), "at most 2") {
-		t.Errorf("err message %q lacks the counts", err)
+	var imgs []llm.ImagePart
+	placeholders := 0
+	for _, m := range out.Messages {
+		for _, p := range m.Parts {
+			switch v := p.(type) {
+			case llm.ImagePart:
+				imgs = append(imgs, v)
+			case llm.TextPart:
+				if v.Text == imageOverflowPlaceholder {
+					placeholders++
+				}
+			}
+		}
+	}
+	// The exact survivors are the most-recent two, in order: b then c (a elided).
+	if len(imgs) != 2 || !bytes.Equal(imgs[0].Data, b.Data) || !bytes.Equal(imgs[1].Data, c.Data) {
+		t.Fatalf("kept %d images; want exactly [b, c] (the most-recent two)", len(imgs))
+	}
+	if placeholders != 1 {
+		t.Errorf("placeholders = %d, want 1 for the elided oldest image", placeholders)
+	}
+	// Input request untouched (copy-on-write): the first part is still image a,
+	// not a placeholder — a len check alone wouldn't catch in-place substitution.
+	first, ok := req.Messages[0].Parts[0].(llm.ImagePart)
+	if !ok || !bytes.Equal(first.Data, a.Data) {
+		t.Errorf("input request was mutated; first part = %+v", req.Messages[0].Parts[0])
 	}
 }
 

provider/llamaswap/image.go

@@ -5,6 +5,7 @@ import (
 	"encoding/base64"
 	"fmt"
 	"net/http"
+	"strconv"
 	"strings"
 
 	"gitea.stevedudenhoeffer.com/steve/majordomo/imagegen"
@@ -27,25 +28,32 @@ type imageModel struct {
 	id string
 }
 
-// imageRequest is the OpenAI /v1/images/generations request shape. We always
-// request b64_json so the bytes come back inline (no second fetch).
-type imageRequest struct {
-	Model          string `json:"model"`
-	Prompt         string `json:"prompt"`
-	N              int    `json:"n,omitempty"`
-	Size           string `json:"size,omitempty"`
-	ResponseFormat string `json:"response_format"`
+// txt2imgRequest is the stable-diffusion.cpp sd-server A1111 request shape
+// (POST /sdapi/v1/txt2img). We use this endpoint rather than the OpenAI
+// /v1/images/generations one because that endpoint IGNORES `seed` on this
+// sd-server build — every render of a given prompt comes back byte-identical,
+// so a batch of N collapses to one image. /sdapi/v1/txt2img honours `seed`,
+// giving real variety. llama-swap still routes by the `model` field in the
+// body. Optional fields are pointers/omitempty so an unset value falls back to
+// the model's baked default (the per-model --steps/--cfg-scale/etc. flags).
+type txt2imgRequest struct {
+	Model          string   `json:"model"`
+	Prompt         string   `json:"prompt"`
+	NegativePrompt string   `json:"negative_prompt,omitempty"`
+	Seed           *int64   `json:"seed,omitempty"`
+	Steps          *int     `json:"steps,omitempty"`
+	CFGScale       *float64 `json:"cfg_scale,omitempty"`
+	Width          *int     `json:"width,omitempty"`
+	Height         *int     `json:"height,omitempty"`
+	SampleMethod   string   `json:"sample_method,omitempty"`
+	BatchCount     int      `json:"batch_count,omitempty"`
 }
 
-type imageResponse struct {
-	Created int64 `json:"created"`
-	Data    []struct {
-		B64JSON string `json:"b64_json"`
-		URL     string `json:"url"`
-	} `json:"data"`
+type txt2imgResponse struct {
+	Images []string `json:"images"`
 }
 
-// Generate implements imagegen.Model via POST {base}/v1/images/generations.
+// Generate implements imagegen.Model via POST {base}/sdapi/v1/txt2img.
 func (m *imageModel) Generate(ctx context.Context, req imagegen.Request, opts ...imagegen.Option) (*imagegen.Result, error) {
 	req = req.Apply(opts...)
 	if strings.TrimSpace(req.Prompt) == "" {
@@ -55,32 +63,35 @@ func (m *imageModel) Generate(ctx context.Context, req imagegen.Request, opts ..
 		return nil, fmt.Errorf("%w: image count N must be >= 0, got %d", llm.ErrUnsupported, req.N)
 	}
 
-	wire := imageRequest{
-		Model:          m.id,
-		Prompt:         req.Prompt,
-		N:              req.N,
-		Size:           req.Size,
-		ResponseFormat: "b64_json",
+	width, height, err := parseSize(req.Size)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", llm.ErrUnsupported, err)
 	}
 
-	var resp imageResponse
-	if err := m.p.doJSON(ctx, http.MethodPost, "/v1/images/generations", m.id, &wire, &resp); err != nil {
+	wire := txt2imgRequest{
+		Model:          m.id,
+		Prompt:         req.Prompt,
+		NegativePrompt: req.NegativePrompt,
+		Seed:           req.Seed,
+		Steps:          req.Steps,
+		CFGScale:       req.CFGScale,
+		Width:          width,
+		Height:         height,
+		SampleMethod:   req.Sampler,
+		BatchCount:     req.N,
+	}
+
+	var resp txt2imgResponse
+	if err := m.p.doJSON(ctx, http.MethodPost, "/sdapi/v1/txt2img", m.id, &wire, &resp); err != nil {
 		return nil, err
 	}
 
 	out := &imagegen.Result{Raw: &resp}
-	for i, d := range resp.Data {
-		if d.B64JSON == "" {
-			// Why error rather than skip: a url-only entry means the backend
-			// ignored response_format; we don't fetch remote content (mirrors
-			// llm.ImagePart's bytes-only contract), so surface it.
-			return nil, &llm.APIError{
-				Provider: m.p.name,
-				Model:    m.id,
-				Message:  fmt.Sprintf("image %d returned no inline b64_json data", i),
-			}
+	for i, b64 := range resp.Images {
+		if b64 == "" {
+			continue
 		}
-		raw, err := base64.StdEncoding.DecodeString(d.B64JSON)
+		raw, err := base64.StdEncoding.DecodeString(b64)
 		if err != nil {
 			return nil, fmt.Errorf("llama-swap: decode image %d: %w", i, err)
 		}
@@ -96,6 +107,25 @@ func (m *imageModel) Generate(ctx context.Context, req imagegen.Request, opts ..
 	return out, nil
 }
 
+// parseSize splits a "WxH" string into width/height pointers. "" yields
+// (nil, nil) so the model's own default resolution applies.
+func parseSize(size string) (*int, *int, error) {
+	size = strings.TrimSpace(size)
+	if size == "" {
+		return nil, nil, nil
+	}
+	parts := strings.SplitN(strings.ToLower(size), "x", 2)
+	if len(parts) != 2 {
+		return nil, nil, fmt.Errorf("invalid size %q (want WxH)", size)
+	}
+	w, err1 := strconv.Atoi(strings.TrimSpace(parts[0]))
+	h, err2 := strconv.Atoi(strings.TrimSpace(parts[1]))
+	if err1 != nil || err2 != nil || w <= 0 || h <= 0 {
+		return nil, nil, fmt.Errorf("invalid size %q (want WxH)", size)
+	}
+	return &w, &h, nil
+}
+
 // sniffImageMIME identifies the image format from its leading bytes, defaulting
 // to image/png (stable-diffusion.cpp emits PNG) when detection is inconclusive.
 func sniffImageMIME(data []byte) string {

provider/llamaswap/llamaswap_test.go

@@ -166,11 +166,11 @@ func TestRunningRaw(t *testing.T) {
 func TestImageGenerate(t *testing.T) {
 	var gotBody map[string]any
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.URL.Path != "/v1/images/generations" {
+		if r.URL.Path != "/sdapi/v1/txt2img" {
 			t.Errorf("path = %q", r.URL.Path)
 		}
 		_ = json.NewDecoder(r.Body).Decode(&gotBody)
-		_, _ = w.Write([]byte(`{"created":1,"data":[{"b64_json":"` + onePixelPNG + `"}]}`))
+		_, _ = w.Write([]byte(`{"images":["` + onePixelPNG + `"]}`))
 	}))
 	defer srv.Close()
 
@@ -192,12 +192,51 @@ func TestImageGenerate(t *testing.T) {
 	if len(res.Images[0].Data) == 0 {
 		t.Error("decoded image has no bytes")
 	}
-	// response_format must be forced to b64_json, and options applied.
-	if gotBody["response_format"] != "b64_json" {
-		t.Errorf("response_format = %v, want b64_json", gotBody["response_format"])
+	// Size is split into width/height ints for the A1111 endpoint.
+	if gotBody["width"] != float64(512) || gotBody["height"] != float64(512) {
+		t.Errorf("width/height = %v/%v, want 512/512", gotBody["width"], gotBody["height"])
 	}
-	if gotBody["size"] != "512x512" {
-		t.Errorf("size = %v, want 512x512", gotBody["size"])
+}
+
+func TestImageGenerateSettings(t *testing.T) {
+	var gotBody map[string]any
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_ = json.NewDecoder(r.Body).Decode(&gotBody)
+		_, _ = w.Write([]byte(`{"images":["` + onePixelPNG + `"]}`))
+	}))
+	defer srv.Close()
+
+	p := New(WithBaseURL(srv.URL), WithHTTPClient(srv.Client()))
+	im, _ := p.ImageModel("sd")
+
+	// Unset overrides must be omitted entirely so sd-server keeps its own
+	// per-model defaults.
+	if _, err := im.Generate(context.Background(), imagegen.Request{Prompt: "x"}); err != nil {
+		t.Fatalf("Generate: %v", err)
+	}
+	for _, k := range []string{"steps", "cfg_scale", "negative_prompt", "sample_method", "seed"} {
+		if v, ok := gotBody[k]; ok {
+			t.Errorf("unset request sent %q = %v, want omitted", k, v)
+		}
+	}
+
+	// Set overrides are forwarded with the sd-server-friendly field names.
+	gotBody = nil
+	_, err := im.Generate(context.Background(), imagegen.Request{Prompt: "x"},
+		imagegen.WithSteps(8),
+		imagegen.WithCFGScale(3.5),
+		imagegen.WithNegativePrompt("blurry"),
+		imagegen.WithSampler("euler"),
+		imagegen.WithSeed(42),
+	)
+	if err != nil {
+		t.Fatalf("Generate: %v", err)
+	}
+	want := map[string]any{"steps": float64(8), "cfg_scale": 3.5, "negative_prompt": "blurry", "sample_method": "euler", "seed": float64(42)}
+	for k, w := range want {
+		if gotBody[k] != w {
+			t.Errorf("%s = %v, want %v", k, gotBody[k], w)
+		}
 	}
 }