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diff --git a/src/features/vision/logic/view-model.ts b/src/features/vision/logic/view-model.ts
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+++ b/src/features/vision/logic/view-model.ts
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+import type { ModelMetadata } from "@dispatch/transport-contract";
+import { isVisionModel } from "../../chat";
+
+/**
+ * Pure core for the vision settings feature — zero DOM, zero effects, zero Svelte.
+ *
+ * The global vision configuration (`GET`/`PUT /settings/vision`) controls image
+ * compaction: how many native images a vision model keeps per turn before the
+ * oldest are transcribed to text (`imageLimit`), and which vision model does the
+ * transcribing (`compactionModel`, null = auto). This module is the view-model
+ * seam: typed settings, parse/validate, dirty-check, network normalization, and
+ * the vision-capable model option list. The composition root adapts the store's
+ * HTTP calls to the injected ports.
+ */
+
+// ── Types (owned locally — consumer-defines-port; the contract shapes are a
+//    plain REST surface not in a shared contract package version bump, mirroring
+//    the heartbeat/mcp pattern). If the backend promotes these to a shared
+//    package, swap the local types for the imports + re-mirror. ──────────────
+
+/** The global vision settings (mirrors `VisionSettingsResponse`). */
+export interface VisionSettings {
+  /** Max native images per turn (default 10); 0 disables compaction. */
+  readonly imageLimit: number;
+  /** Which model transcribes old images (`<key>/<model>`), or null = auto. */
+  readonly compactionModel: string | null;
+}
+
+/** A partial update (mirrors `SetVisionSettingsRequest`). */
+export interface VisionSettingsPatch {
+  readonly imageLimit?: number;
+  readonly compactionModel?: string | null;
+}
+
+// ── Injected ports (consumer-defines-port). ───────────────────────────────────
+
+/** Outcome of loading the vision settings. */
+export type LoadVisionSettingsResult =
+  | { readonly ok: true; readonly settings: VisionSettings }
+  | { readonly ok: false; readonly error: string };
+
+/** Outcome of saving a partial vision-settings update. */
+export type SaveVisionSettingsResult =
+  | { readonly ok: true; readonly settings: VisionSettings }
+  | { readonly ok: false; readonly error: string };
+
+export type LoadVisionSettings = () => Promise<LoadVisionSettingsResult>;
+export type SaveVisionSettings = (patch: VisionSettingsPatch) => Promise<SaveVisionSettingsResult>;
+
+// ── Constants ────────────────────────────────────────────────────────────────
+
+/** The backend's default image limit when none is persisted. */
+export const DEFAULT_IMAGE_LIMIT = 10;
+/** Upper bound for the image limit input (defensive — the backend owns real clamping). */
+export const MAX_IMAGE_LIMIT = 1000;
+
+// ── Network normalization (pure; coerces untyped JSON at the seam). ──────────
+
+/**
+ * Coerce an untyped JSON body (from `GET /settings/vision`) into a valid
+ * `VisionSettings`. A malformed/partial response can never crash the renderer:
+ * `imageLimit` falls back to the default; `compactionModel` coerces to null.
+ */
+export function normalizeVisionSettings(body: unknown): VisionSettings {
+  if (body === null || typeof body !== "object") {
+    return { imageLimit: DEFAULT_IMAGE_LIMIT, compactionModel: null };
+  }
+  const raw = body as Record<string, unknown>;
+  const limitRaw = raw.imageLimit;
+  const imageLimit =
+    typeof limitRaw === "number" && Number.isFinite(limitRaw) && limitRaw >= 0
+      ? Math.floor(limitRaw)
+      : DEFAULT_IMAGE_LIMIT;
+  const modelRaw = raw.compactionModel;
+  const compactionModel = typeof modelRaw === "string" && modelRaw.length > 0 ? modelRaw : null;
+  return { imageLimit, compactionModel };
+}
+
+// ── imageLimit parse / validate ───────────────────────────────────────────────
+
+/** Result of parsing a typed image-limit string. */
+export type ImageLimitParse =
+  | { readonly ok: true; readonly value: number }
+  | { readonly ok: false; readonly error: string };
+
+/**
+ * Parse a typed image-limit string into a non-negative integer (floored,
+ * clamped to [0, MAX_IMAGE_LIMIT]). Empty or non-numeric input is an ERROR
+ * (so the UI can disable submit + message), NOT a silent default.
+ */
+export function parseImageLimit(raw: string): ImageLimitParse {
+  const trimmed = raw.trim();
+  if (trimmed.length === 0) {
+    return { ok: false, error: "Enter a number." };
+  }
+  const n = Number(trimmed);
+  if (!Number.isFinite(n) || n < 0) {
+    return { ok: false, error: "Must be 0 or a positive number." };
+  }
+  const floored = Math.floor(n);
+  if (floored > MAX_IMAGE_LIMIT) {
+    return { ok: false, error: `Must be at most ${MAX_IMAGE_LIMIT}.` };
+  }
+  return { ok: true, value: floored };
+}
+
+/**
+ * Whether saving `typed` would change the `current` image limit. A no-op save
+ * (empty/invalid, or equal) should be disabled. This is the dirty-check for the
+ * input — it must NOT mutate or clamp, only compare.
+ */
+export function imageLimitChanged(typed: string, current: number): boolean {
+  const parsed = parseImageLimit(typed);
+  if (!parsed.ok) return false;
+  return parsed.value !== current;
+}
+
+// ── compactionModel option list ───────────────────────────────────────────────
+
+/**
+ * The sentinel value for the "Auto" option (null compactionModel — the server
+ * auto-selects a vision model). Used as the `<option value>` for the auto row.
+ */
+export const AUTO_COMPACTION_MODEL = "__auto__";
+
+/** A selectable compaction-model option. */
+export interface CompactionModelOption {
+  /** The value to send (`<key>/<model>`, or `AUTO_COMPACTION_MODEL` for auto). */
+  readonly value: string;
+  /** The human-readable label. */
+  readonly label: string;
+  /** Whether this is the "Auto" sentinel. */
+  readonly auto: boolean;
+}
+
+/**
+ * Build the compaction-model dropdown options: the "Auto" entry (null) plus
+ * every vision-capable model from the catalog (those with
+ * `modelInfo[name].vision === true`), in catalog order. Non-vision models are
+ * excluded — they cannot transcribe images.
+ */
+export function compactionModelOptions(
+  models: readonly string[],
+  modelInfo: Readonly<Record<string, ModelMetadata>>,
+): CompactionModelOption[] {
+  const options: CompactionModelOption[] = [
+    { value: AUTO_COMPACTION_MODEL, label: "Auto (server-selected)", auto: true },
+  ];
+  for (const name of models) {
+    if (isVisionModel(modelInfo, name)) {
+      options.push({ value: name, label: name, auto: false });
+    }
+  }
+  return options;
+}
+
+/**
+ * The `<option value>` to mark selected for the current `compactionModel`:
+ * `AUTO_COMPACTION_MODEL` when null (auto), else the model name itself.
+ */
+export function selectedCompactionValue(compactionModel: string | null): string {
+  return compactionModel ?? AUTO_COMPACTION_MODEL;
+}
+
+/**
+ * Convert a selected `<option value>` back into a `VisionSettingsPatch`
+ * `compactionModel` (the auto sentinel → null). Returns the patch alone so the
+ * caller can merge it with other fields.
+ */
+export function compactionModelFromValue(value: string): string | null {
+  return value === AUTO_COMPACTION_MODEL ? null : value;
+}
+
+/**
+ * Whether choosing `value` would change the current `compactionModel`.
+ */
+export function compactionModelChanged(value: string, current: string | null): boolean {
+  return compactionModelFromValue(value) !== current;
+}
+
+// ── Labels ────────────────────────────────────────────────────────────────────
+
+/** A human-readable label for the current image limit (for the status line). */
+export function imageLimitLabel(imageLimit: number | null): string {
+  if (imageLimit === null) return "Loading…";
+  if (imageLimit === 0) return "0 (compaction disabled)";
+  if (imageLimit === DEFAULT_IMAGE_LIMIT) return `${imageLimit} (default)`;
+  return String(imageLimit);
+}