diff --git a/docs/gateway/configuration-reference.md b/docs/gateway/configuration-reference.md
index 50f40998ca1..f428a20546a 100644
--- a/docs/gateway/configuration-reference.md
+++ b/docs/gateway/configuration-reference.md
@@ -718,9 +718,14 @@ Time format in system prompt. Default: `auto` (OS preference).
 }
 ```
 
+- `model`: accepts either a string (`"provider/model"`) or an object (`{ primary, fallbacks }`).
+  - String form sets only the primary model.
+  - Object form sets primary plus ordered failover models.
+- `imageModel`: accepts either a string (`"provider/model"`) or an object (`{ primary, fallbacks }`).
+  - Only used if the selected/default model cannot accept image input.
 - `model.primary`: format `provider/model` (e.g. `anthropic/claude-opus-4-6`). If you omit the provider, OpenClaw assumes `anthropic` (deprecated).
 - `models`: the configured model catalog and allowlist for `/model`. Each entry can include `alias` (shortcut) and `params` (provider-specific: `temperature`, `maxTokens`).
-- `imageModel`: only used if the primary model lacks image input.
+- Config writers that mutate these fields (for example `/models set`, `/models set-image`, and fallback add/remove commands) save canonical object form and preserve existing fallback lists when possible.
 - `maxConcurrent`: max parallel agent runs across sessions (each session still serialized). Default: 1.
 
 **Built-in alias shorthands** (only apply when the model is in `agents.defaults.models`):
diff --git a/src/agents/agent-scope.ts b/src/agents/agent-scope.ts
index 6249eef9954..c48cea9f690 100644
--- a/src/agents/agent-scope.ts
+++ b/src/agents/agent-scope.ts
@@ -1,5 +1,6 @@
 import path from "node:path";
 import type { OpenClawConfig } from "../config/config.js";
+import { resolveAgentModelFallbackValues } from "../config/model-input.js";
 import { resolveStateDir } from "../config/paths.js";
 import { createSubsystemLogger } from "../logging/subsystem.js";
 import {
@@ -205,10 +206,7 @@ export function resolveEffectiveModelFallbacks(params: {
   if (!params.hasSessionModelOverride) {
     return agentFallbacksOverride;
   }
-  const defaultFallbacks =
-    typeof params.cfg.agents?.defaults?.model === "object"
-      ? (params.cfg.agents.defaults.model.fallbacks ?? [])
-      : [];
+  const defaultFallbacks = resolveAgentModelFallbackValues(params.cfg.agents?.defaults?.model);
   return agentFallbacksOverride ?? defaultFallbacks;
 }
 
diff --git a/src/agents/model-fallback.ts b/src/agents/model-fallback.ts
index 7a7a192e8d4..b0050602590 100644
--- a/src/agents/model-fallback.ts
+++ b/src/agents/model-fallback.ts
@@ -1,4 +1,8 @@
 import type { OpenClawConfig } from "../config/config.js";
+import {
+  resolveAgentModelFallbackValues,
+  resolveAgentModelPrimaryValue,
+} from "../config/model-input.js";
 import {
   ensureAuthProfileStore,
   getSoonestCooldownExpiry,
@@ -151,26 +155,13 @@ function resolveImageFallbackCandidates(params: {
   if (params.modelOverride?.trim()) {
     addRaw(params.modelOverride, false);
   } else {
-    const imageModel = params.cfg?.agents?.defaults?.imageModel as
-      | { primary?: string }
-      | string
-      | undefined;
-    const primary = typeof imageModel === "string" ? imageModel.trim() : imageModel?.primary;
+    const primary = resolveAgentModelPrimaryValue(params.cfg?.agents?.defaults?.imageModel);
     if (primary?.trim()) {
       addRaw(primary, false);
     }
   }
 
-  const imageFallbacks = (() => {
-    const imageModel = params.cfg?.agents?.defaults?.imageModel as
-      | { fallbacks?: string[] }
-      | string
-      | undefined;
-    if (imageModel && typeof imageModel === "object") {
-      return imageModel.fallbacks ?? [];
-    }
-    return [];
-  })();
+  const imageFallbacks = resolveAgentModelFallbackValues(params.cfg?.agents?.defaults?.imageModel);
 
   for (const raw of imageFallbacks) {
     addRaw(raw, true);
@@ -220,14 +211,7 @@ function resolveFallbackCandidates(params: {
     if (!sameModelCandidate(normalizedPrimary, configuredPrimary)) {
       return []; // Override model failed → go straight to configured default
     }
-    const model = params.cfg?.agents?.defaults?.model as
-      | { fallbacks?: string[] }
-      | string
-      | undefined;
-    if (model && typeof model === "object") {
-      return model.fallbacks ?? [];
-    }
-    return [];
+    return resolveAgentModelFallbackValues(params.cfg?.agents?.defaults?.model);
   })();
 
   for (const raw of modelFallbacks) {
diff --git a/src/agents/model-selection.ts b/src/agents/model-selection.ts
index 00334d3fd12..6f6e6d10f09 100644
--- a/src/agents/model-selection.ts
+++ b/src/agents/model-selection.ts
@@ -1,5 +1,5 @@
 import type { OpenClawConfig } from "../config/config.js";
-import { resolveAgentModelPrimaryValue } from "../config/model-input.js";
+import { resolveAgentModelPrimaryValue, toAgentModelListLike } from "../config/model-input.js";
 import { createSubsystemLogger } from "../logging/subsystem.js";
 import { resolveAgentConfig, resolveAgentEffectiveModelPrimary } from "./agent-scope.js";
 import { DEFAULT_MODEL, DEFAULT_PROVIDER } from "./defaults.js";
@@ -309,9 +309,7 @@ export function resolveDefaultModelForAgent(params: {
             defaults: {
               ...params.cfg.agents?.defaults,
               model: {
-                ...(typeof params.cfg.agents?.defaults?.model === "object"
-                  ? params.cfg.agents.defaults.model
-                  : undefined),
+                ...toAgentModelListLike(params.cfg.agents?.defaults?.model),
                 primary: agentModelOverride,
               },
             },
diff --git a/src/agents/tools/image-tool.helpers.ts b/src/agents/tools/image-tool.helpers.ts
index ae98e40ba26..a1581cb2b94 100644
--- a/src/agents/tools/image-tool.helpers.ts
+++ b/src/agents/tools/image-tool.helpers.ts
@@ -1,5 +1,9 @@
 import type { AssistantMessage } from "@mariozechner/pi-ai";
 import type { OpenClawConfig } from "../../config/config.js";
+import {
+  resolveAgentModelFallbackValues,
+  resolveAgentModelPrimaryValue,
+} from "../../config/model-input.js";
 import { extractAssistantText } from "../pi-embedded-utils.js";
 
 export type ImageModelConfig = { primary?: string; fallbacks?: string[] };
@@ -51,12 +55,8 @@ export function coerceImageAssistantText(params: {
 }
 
 export function coerceImageModelConfig(cfg?: OpenClawConfig): ImageModelConfig {
-  const imageModel = cfg?.agents?.defaults?.imageModel as
-    | { primary?: string; fallbacks?: string[] }
-    | string
-    | undefined;
-  const primary = typeof imageModel === "string" ? imageModel.trim() : imageModel?.primary;
-  const fallbacks = typeof imageModel === "object" ? (imageModel?.fallbacks ?? []) : [];
+  const primary = resolveAgentModelPrimaryValue(cfg?.agents?.defaults?.imageModel);
+  const fallbacks = resolveAgentModelFallbackValues(cfg?.agents?.defaults?.imageModel);
   return {
     ...(primary?.trim() ? { primary: primary.trim() } : {}),
     ...(fallbacks.length > 0 ? { fallbacks } : {}),
diff --git a/src/commands/auth-choice.apply.github-copilot.ts b/src/commands/auth-choice.apply.github-copilot.ts
index cd67ae1cbdf..1ef474682af 100644
--- a/src/commands/auth-choice.apply.github-copilot.ts
+++ b/src/commands/auth-choice.apply.github-copilot.ts
@@ -1,3 +1,4 @@
+import { toAgentModelListLike } from "../config/model-input.js";
 import { githubCopilotLoginCommand } from "../providers/github-copilot-auth.js";
 import type { ApplyAuthChoiceParams, ApplyAuthChoiceResult } from "./auth-choice.apply.js";
 import { applyAuthProfileConfig } from "./onboard-auth.js";
@@ -49,9 +50,7 @@ export async function applyAuthChoiceGitHubCopilot(
         defaults: {
           ...nextConfig.agents?.defaults,
           model: {
-            ...(typeof nextConfig.agents?.defaults?.model === "object"
-              ? nextConfig.agents.defaults.model
-              : undefined),
+            ...toAgentModelListLike(nextConfig.agents?.defaults?.model),
             primary: model,
           },
         },
diff --git a/src/commands/model-picker.ts b/src/commands/model-picker.ts
index 6b1c8691e02..db794210354 100644
--- a/src/commands/model-picker.ts
+++ b/src/commands/model-picker.ts
@@ -10,6 +10,7 @@ import {
   resolveConfiguredModelRef,
 } from "../agents/model-selection.js";
 import type { OpenClawConfig } from "../config/config.js";
+import { resolveAgentModelPrimaryValue } from "../config/model-input.js";
 import type { WizardPrompter, WizardSelectOption } from "../wizard/prompts.js";
 import { formatTokenK } from "./models/shared.js";
 import { OPENAI_CODEX_DEFAULT_MODEL } from "./openai-codex-model-default.js";
@@ -77,11 +78,7 @@ function createProviderAuthChecker(params: {
 }
 
 function resolveConfiguredModelRaw(cfg: OpenClawConfig): string {
-  const raw = cfg.agents?.defaults?.model as { primary?: string } | string | undefined;
-  if (typeof raw === "string") {
-    return raw.trim();
-  }
-  return raw?.primary?.trim() ?? "";
+  return resolveAgentModelPrimaryValue(cfg.agents?.defaults?.model) ?? "";
 }
 
 function resolveConfiguredModelKeys(cfg: OpenClawConfig): string[] {
diff --git a/src/commands/models/list.configured.ts b/src/commands/models/list.configured.ts
index a4300ea563a..fed70a4fe47 100644
--- a/src/commands/models/list.configured.ts
+++ b/src/commands/models/list.configured.ts
@@ -5,6 +5,10 @@ import {
   resolveModelRefFromString,
 } from "../../agents/model-selection.js";
 import type { OpenClawConfig } from "../../config/config.js";
+import {
+  resolveAgentModelFallbackValues,
+  resolveAgentModelPrimaryValue,
+} from "../../config/model-input.js";
 import type { ConfiguredEntry } from "./list.types.js";
 import { DEFAULT_MODEL, DEFAULT_PROVIDER, modelKey } from "./shared.js";
 
@@ -37,16 +41,9 @@ export function resolveConfiguredEntries(cfg: OpenClawConfig) {
 
   addEntry(resolvedDefault, "default");
 
-  const modelConfig = cfg.agents?.defaults?.model as
-    | { primary?: string; fallbacks?: string[] }
-    | undefined;
-  const imageModelConfig = cfg.agents?.defaults?.imageModel as
-    | { primary?: string; fallbacks?: string[] }
-    | undefined;
-  const modelFallbacks = typeof modelConfig === "object" ? (modelConfig?.fallbacks ?? []) : [];
-  const imageFallbacks =
-    typeof imageModelConfig === "object" ? (imageModelConfig?.fallbacks ?? []) : [];
-  const imagePrimary = imageModelConfig?.primary?.trim() ?? "";
+  const modelFallbacks = resolveAgentModelFallbackValues(cfg.agents?.defaults?.model);
+  const imageFallbacks = resolveAgentModelFallbackValues(cfg.agents?.defaults?.imageModel);
+  const imagePrimary = resolveAgentModelPrimaryValue(cfg.agents?.defaults?.imageModel) ?? "";
 
   modelFallbacks.forEach((raw, idx) => {
     const resolved = resolveModelRefFromString({
diff --git a/src/commands/models/list.status-command.ts b/src/commands/models/list.status-command.ts
index 5929d5e3653..830aefdf0af 100644
--- a/src/commands/models/list.status-command.ts
+++ b/src/commands/models/list.status-command.ts
@@ -26,6 +26,10 @@ import {
 import { formatCliCommand } from "../../cli/command-format.js";
 import { withProgressTotals } from "../../cli/progress.js";
 import { CONFIG_PATH, loadConfig } from "../../config/config.js";
+import {
+  resolveAgentModelFallbackValues,
+  resolveAgentModelPrimaryValue,
+} from "../../config/model-input.js";
 import {
   formatUsageWindowSummary,
   loadProviderUsageSummary,
@@ -87,24 +91,14 @@ export async function modelsStatusCommand(
         defaultModel: DEFAULT_MODEL,
       });
 
-  const modelConfig = cfg.agents?.defaults?.model as
-    | { primary?: string; fallbacks?: string[] }
-    | string
-    | undefined;
-  const imageConfig = cfg.agents?.defaults?.imageModel as
-    | { primary?: string; fallbacks?: string[] }
-    | string
-    | undefined;
-  const rawDefaultsModel =
-    typeof modelConfig === "string" ? modelConfig.trim() : (modelConfig?.primary?.trim() ?? "");
+  const rawDefaultsModel = resolveAgentModelPrimaryValue(cfg.agents?.defaults?.model) ?? "";
   const rawModel = agentModelPrimary ?? rawDefaultsModel;
   const resolvedLabel = `${resolved.provider}/${resolved.model}`;
   const defaultLabel = rawModel || resolvedLabel;
-  const defaultsFallbacks = typeof modelConfig === "object" ? (modelConfig?.fallbacks ?? []) : [];
+  const defaultsFallbacks = resolveAgentModelFallbackValues(cfg.agents?.defaults?.model);
   const fallbacks = agentFallbacksOverride ?? defaultsFallbacks;
-  const imageModel =
-    typeof imageConfig === "string" ? imageConfig.trim() : (imageConfig?.primary?.trim() ?? "");
-  const imageFallbacks = typeof imageConfig === "object" ? (imageConfig?.fallbacks ?? []) : [];
+  const imageModel = resolveAgentModelPrimaryValue(cfg.agents?.defaults?.imageModel) ?? "";
+  const imageFallbacks = resolveAgentModelFallbackValues(cfg.agents?.defaults?.imageModel);
   const aliases = Object.entries(cfg.agents?.defaults?.models ?? {}).reduce<Record<string, string>>(
     (acc, [key, entry]) => {
       const alias = typeof entry?.alias === "string" ? entry.alias.trim() : undefined;
diff --git a/src/commands/models/scan.ts b/src/commands/models/scan.ts
index 74b17b8ab86..c62ca0e107a 100644
--- a/src/commands/models/scan.ts
+++ b/src/commands/models/scan.ts
@@ -4,6 +4,7 @@ import { type ModelScanResult, scanOpenRouterModels } from "../../agents/model-s
 import { withProgressTotals } from "../../cli/progress.js";
 import { loadConfig } from "../../config/config.js";
 import { logConfigUpdated } from "../../config/logging.js";
+import { toAgentModelListLike } from "../../config/model-input.js";
 import type { RuntimeEnv } from "../../runtime.js";
 import {
   stylePromptHint,
@@ -297,9 +298,7 @@ export async function modelsScanCommand(
         nextModels[entry] = {};
       }
     }
-    const existingImageModel = cfg.agents?.defaults?.imageModel as
-      | { primary?: string; fallbacks?: string[] }
-      | undefined;
+    const existingImageModel = toAgentModelListLike(cfg.agents?.defaults?.imageModel);
     const nextImageModel =
       selectedImages.length > 0
         ? {
@@ -308,9 +307,7 @@ export async function modelsScanCommand(
             ...(opts.setImage ? { primary: selectedImages[0] } : {}),
           }
         : cfg.agents?.defaults?.imageModel;
-    const existingModel = cfg.agents?.defaults?.model as
-      | { primary?: string; fallbacks?: string[] }
-      | undefined;
+    const existingModel = toAgentModelListLike(cfg.agents?.defaults?.model);
     const defaults = {
       ...cfg.agents?.defaults,
       model: {
diff --git a/src/commands/onboard-helpers.ts b/src/commands/onboard-helpers.ts
index 48f9e87c31e..6e029531f50 100644
--- a/src/commands/onboard-helpers.ts
+++ b/src/commands/onboard-helpers.ts
@@ -6,6 +6,7 @@ import { cancel, isCancel } from "@clack/prompts";
 import { DEFAULT_AGENT_WORKSPACE_DIR, ensureAgentWorkspace } from "../agents/workspace.js";
 import type { OpenClawConfig } from "../config/config.js";
 import { CONFIG_PATH } from "../config/config.js";
+import { resolveAgentModelPrimaryValue } from "../config/model-input.js";
 import { resolveSessionTranscriptsDirForAgent } from "../config/sessions.js";
 import { callGateway } from "../gateway/call.js";
 import { normalizeControlUiBasePath } from "../gateway/control-ui-shared.js";
@@ -43,7 +44,7 @@ export function summarizeExistingConfig(config: OpenClawConfig): string {
     rows.push(shortenHomeInString(`workspace: ${defaults.workspace}`));
   }
   if (defaults?.model) {
-    const model = typeof defaults.model === "string" ? defaults.model : defaults.model.primary;
+    const model = resolveAgentModelPrimaryValue(defaults.model);
     if (model) {
       rows.push(shortenHomeInString(`model: ${model}`));
     }
diff --git a/src/media-understanding/runner.ts b/src/media-understanding/runner.ts
index ad7b28328d9..c2ffe584448 100644
--- a/src/media-understanding/runner.ts
+++ b/src/media-understanding/runner.ts
@@ -10,6 +10,10 @@ import {
 } from "../agents/model-catalog.js";
 import type { MsgContext } from "../auto-reply/templating.js";
 import type { OpenClawConfig } from "../config/config.js";
+import {
+  resolveAgentModelFallbackValues,
+  resolveAgentModelPrimaryValue,
+} from "../config/model-input.js";
 import type {
   MediaUnderstandingConfig,
   MediaUnderstandingModelConfig,
@@ -418,28 +422,19 @@ async function resolveKeyEntry(params: {
 }
 
 function resolveImageModelFromAgentDefaults(cfg: OpenClawConfig): MediaUnderstandingModelConfig[] {
-  const imageModel = cfg.agents?.defaults?.imageModel as
-    | { primary?: string; fallbacks?: string[] }
-    | string
-    | undefined;
-  if (!imageModel) {
-    return [];
-  }
   const refs: string[] = [];
-  if (typeof imageModel === "string") {
-    if (imageModel.trim()) {
-      refs.push(imageModel.trim());
-    }
-  } else {
-    if (imageModel.primary?.trim()) {
-      refs.push(imageModel.primary.trim());
-    }
-    for (const fb of imageModel.fallbacks ?? []) {
-      if (fb?.trim()) {
-        refs.push(fb.trim());
-      }
+  const primary = resolveAgentModelPrimaryValue(cfg.agents?.defaults?.imageModel);
+  if (primary?.trim()) {
+    refs.push(primary.trim());
+  }
+  for (const fb of resolveAgentModelFallbackValues(cfg.agents?.defaults?.imageModel)) {
+    if (fb?.trim()) {
+      refs.push(fb.trim());
     }
   }
+  if (refs.length === 0) {
+    return [];
+  }
   const entries: MediaUnderstandingModelConfig[] = [];
   for (const ref of refs) {
     const slashIdx = ref.indexOf("/");