diff --git a/src/lib/llmParams.ts b/src/lib/llmParams.ts
new file mode 100644
index 0000000..d1a79aa
--- /dev/null
+++ b/src/lib/llmParams.ts
@@ -0,0 +1,317 @@
+// Ollama advanced `options` parameters (T5.2) — the single source of truth that
+// drives the Settings ▸ AI advanced form: rendering, defaults, per-field reset,
+// and only-send-if-changed. System prompt / think / keep_alive are top-level
+// request fields handled separately in the UI; everything here goes in `options`.
+//
+// Defaults + ranges per the Ollama Modelfile/API reference.
+
+export type OllamaGroup = "sampling" | "repetition" | "mirostat" | "context" | "hardware";
+
+export interface OllamaOption {
+  key: string;
+  group: OllamaGroup;
+  label: string;
+  kind: "number" | "bool" | "enum" | "tags";
+  /** Undefined = "auto" (no fixed default): the field is empty until set. */
+  default?: number | boolean;
+  min?: number;
+  max?: number;
+  step?: number;
+  enumOptions?: { value: number; label: string }[];
+  help: string;
+  /** Dimmed unless Mirostat is enabled (mirostat != 0). */
+  needsMirostat?: boolean;
+}
+
+export const OLLAMA_OPTIONS: OllamaOption[] = [
+  // ── Sampling ──────────────────────────────────────────────────────────────
+  {
+    key: "temperature",
+    group: "sampling",
+    label: "Temperature",
+    kind: "number",
+    default: 0.8,
+    min: 0,
+    max: 2,
+    step: 0.05,
+    help: "Randomness / creativity. Higher is more creative.",
+  },
+  {
+    key: "top_k",
+    group: "sampling",
+    label: "Top K",
+    kind: "number",
+    default: 40,
+    min: 0,
+    max: 200,
+    step: 1,
+    help: "Sample only from the K most likely tokens.",
+  },
+  {
+    key: "top_p",
+    group: "sampling",
+    label: "Top P",
+    kind: "number",
+    default: 0.9,
+    min: 0,
+    max: 1,
+    step: 0.05,
+    help: "Nucleus sampling cumulative probability.",
+  },
+  {
+    key: "min_p",
+    group: "sampling",
+    label: "Min P",
+    kind: "number",
+    default: 0.0,
+    min: 0,
+    max: 1,
+    step: 0.01,
+    help: "Minimum probability relative to the top token.",
+  },
+  {
+    key: "typical_p",
+    group: "sampling",
+    label: "Typical P",
+    kind: "number",
+    default: 1.0,
+    min: 0,
+    max: 1,
+    step: 0.05,
+    help: "Locally-typical sampling.",
+  },
+  {
+    key: "tfs_z",
+    group: "sampling",
+    label: "Tail-free (tfs_z)",
+    kind: "number",
+    default: 1.0,
+    min: 0,
+    max: 2,
+    step: 0.05,
+    help: "Tail-free sampling. 1.0 disables it (legacy).",
+  },
+  {
+    key: "seed",
+    group: "sampling",
+    label: "Seed",
+    kind: "number",
+    default: 0,
+    min: 0,
+    step: 1,
+    help: "Fixed seed → reproducible output. 0 = random.",
+  },
+  {
+    key: "num_predict",
+    group: "sampling",
+    label: "Max tokens (num_predict)",
+    kind: "number",
+    default: -1,
+    min: -2,
+    step: 1,
+    help: "Max tokens to generate. -1 = unlimited, -2 = fill context.",
+  },
+
+  // ── Repetition ────────────────────────────────────────────────────────────
+  {
+    key: "repeat_penalty",
+    group: "repetition",
+    label: "Repeat penalty",
+    kind: "number",
+    default: 1.1,
+    min: 0,
+    max: 2,
+    step: 0.05,
+    help: "How strongly to penalize repetition.",
+  },
+  {
+    key: "repeat_last_n",
+    group: "repetition",
+    label: "Repeat lookback",
+    kind: "number",
+    default: 64,
+    min: -1,
+    step: 1,
+    help: "Tokens to look back for repetition. 0 = off, -1 = num_ctx.",
+  },
+  {
+    key: "presence_penalty",
+    group: "repetition",
+    label: "Presence penalty",
+    kind: "number",
+    default: 0.0,
+    min: -2,
+    max: 2,
+    step: 0.1,
+    help: "Penalize tokens that already appeared.",
+  },
+  {
+    key: "frequency_penalty",
+    group: "repetition",
+    label: "Frequency penalty",
+    kind: "number",
+    default: 0.0,
+    min: -2,
+    max: 2,
+    step: 0.1,
+    help: "Penalize tokens by how often they appear.",
+  },
+  {
+    key: "penalize_newline",
+    group: "repetition",
+    label: "Penalize newlines",
+    kind: "bool",
+    default: true,
+    help: "Apply the repeat penalty to newline tokens.",
+  },
+
+  // ── Mirostat ──────────────────────────────────────────────────────────────
+  {
+    key: "mirostat",
+    group: "mirostat",
+    label: "Mirostat",
+    kind: "enum",
+    default: 0,
+    enumOptions: [
+      { value: 0, label: "Off" },
+      { value: 1, label: "Mirostat 1" },
+      { value: 2, label: "Mirostat 2" },
+    ],
+    help: "Adaptive perplexity control.",
+  },
+  {
+    key: "mirostat_tau",
+    group: "mirostat",
+    label: "Mirostat τ (tau)",
+    kind: "number",
+    default: 5.0,
+    min: 0,
+    max: 10,
+    step: 0.1,
+    help: "Balance of coherence vs diversity.",
+    needsMirostat: true,
+  },
+  {
+    key: "mirostat_eta",
+    group: "mirostat",
+    label: "Mirostat η (eta)",
+    kind: "number",
+    default: 0.1,
+    min: 0,
+    max: 1,
+    step: 0.01,
+    help: "How fast it adapts to feedback.",
+    needsMirostat: true,
+  },
+
+  // ── Context & session ─────────────────────────────────────────────────────
+  {
+    key: "num_ctx",
+    group: "context",
+    label: "Context size (num_ctx)",
+    kind: "number",
+    default: 4096,
+    min: 256,
+    step: 256,
+    help: "Context window in tokens.",
+  },
+  {
+    key: "num_keep",
+    group: "context",
+    label: "Keep tokens (num_keep)",
+    kind: "number",
+    default: 4,
+    min: 0,
+    step: 1,
+    help: "Tokens kept from the start of the prompt when truncating.",
+  },
+  {
+    key: "stop",
+    group: "context",
+    label: "Stop sequences",
+    kind: "tags",
+    help: "Comma-separated strings that end generation.",
+  },
+
+  // ── Runtime & hardware (rarely needed) ────────────────────────────────────
+  {
+    key: "num_batch",
+    group: "hardware",
+    label: "Batch size (num_batch)",
+    kind: "number",
+    default: 512,
+    min: 1,
+    step: 1,
+    help: "Prompt processing batch size.",
+  },
+  {
+    key: "num_gpu",
+    group: "hardware",
+    label: "GPU layers (num_gpu)",
+    kind: "number",
+    min: 0,
+    step: 1,
+    help: "Layers to offload to the GPU. Blank = auto.",
+  },
+  {
+    key: "main_gpu",
+    group: "hardware",
+    label: "Main GPU",
+    kind: "number",
+    default: 0,
+    min: 0,
+    step: 1,
+    help: "Which GPU to use for a single-GPU offload.",
+  },
+  {
+    key: "num_thread",
+    group: "hardware",
+    label: "CPU threads (num_thread)",
+    kind: "number",
+    min: 1,
+    step: 1,
+    help: "Threads for computation. Blank = auto.",
+  },
+  {
+    key: "low_vram",
+    group: "hardware",
+    label: "Low VRAM",
+    kind: "bool",
+    default: false,
+    help: "Reduce VRAM use at the cost of speed.",
+  },
+  {
+    key: "numa",
+    group: "hardware",
+    label: "NUMA",
+    kind: "bool",
+    default: false,
+    help: "Enable NUMA support.",
+  },
+  {
+    key: "use_mmap",
+    group: "hardware",
+    label: "Use mmap",
+    kind: "bool",
+    default: true,
+    help: "Memory-map the model file.",
+  },
+  {
+    key: "use_mlock",
+    group: "hardware",
+    label: "Use mlock",
+    kind: "bool",
+    default: false,
+    help: "Lock the model in RAM (no swap).",
+  },
+];
+
+export const THINK_OPTIONS = ["off", "low", "medium", "high", "max"] as const;
+
+export const OLLAMA_GROUP_LABELS: Record<OllamaGroup, string> = {
+  sampling: "Sampling",
+  repetition: "Repetition",
+  mirostat: "Mirostat",
+  context: "Context & session",
+  hardware: "Runtime & hardware",
+};