diff --git a/CHANGELOG.md b/CHANGELOG.md
index 549ea9b434f..9fe149e57a3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Agents/models: keep per-agent primary models strict when `fallbacks` is omitted, so probe-only custom providers are not tried as hidden fallback candidates unless the agent explicitly opts in. Fixes #73332. Thanks @haumanto.
 - Cron/Telegram: preserve explicit `:topic:` delivery targets over stale session-derived thread IDs when isolated cron announces to Telegram forum topics. Carries forward #59069; refs #49704 and #43808. Thanks @roytong9.
 - Build/runtime: write the runtime-postbuild stamp after `pnpm build` writes the build stamp, so the next CLI invocation does not re-sync runtime artifacts after a successful build. Fixes #73151. Thanks @bittoby.
 - CLI/model probes: reject empty or whitespace-only `infer model run --prompt` values before calling local providers or the Gateway, so smoke checks do not spend provider calls on invalid turns. Fixes #73185. Thanks @iot2edge.
diff --git a/docs/concepts/model-failover.md b/docs/concepts/model-failover.md
index d9d5bd22533..620484526ff 100644
--- a/docs/concepts/model-failover.md
+++ b/docs/concepts/model-failover.md
@@ -58,7 +58,8 @@ That prevents a failed fallback retry from overwriting newer unrelated session m
 
 OpenClaw separates the selected provider/model from why it was selected. That source controls whether the fallback chain is allowed:
 
-- **Configured default**: `agents.defaults.model.primary` (or an agent-specific primary) uses the configured fallback chain.
+- **Configured default**: `agents.defaults.model.primary` uses `agents.defaults.model.fallbacks`.
+- **Agent primary**: `agents.list[].model` is strict unless that agent model object includes its own `fallbacks`. Use `fallbacks: []` to make the strict behavior explicit, or provide a non-empty list to opt that agent into model fallback.
 - **Auto fallback override**: a runtime fallback writes `providerOverride`, `modelOverride`, and `modelOverrideSource: "auto"` before retrying. That auto override can keep walking the configured fallback chain and is cleared by `/new`, `/reset`, and `sessions.reset`.
 - **User session override**: `/model`, the model picker, `session_status(model=...)`, and `sessions.patch` write `modelOverrideSource: "user"`. That is an exact session selection. If the selected provider/model fails before producing a reply, OpenClaw reports the failure instead of answering from an unrelated configured fallback.
 - **Legacy session override**: older session entries may have `modelOverride` without `modelOverrideSource`. OpenClaw treats those as user overrides so an explicit old selection is not silently converted into fallback behavior.
@@ -217,7 +218,7 @@ If all profiles for a provider fail, OpenClaw moves to the next model in `agents
 
 Overloaded and rate-limit errors are handled more aggressively than billing cooldowns. By default, OpenClaw allows one same-provider auth-profile retry, then switches to the next configured model fallback without waiting. Provider-busy signals such as `ModelNotReadyException` land in that overloaded bucket. Tune this with `auth.cooldowns.overloadedProfileRotations`, `auth.cooldowns.overloadedBackoffMs`, and `auth.cooldowns.rateLimitedProfileRotations`.
 
-When a run starts from the configured primary, a cron job primary, or an auto-selected fallback override, OpenClaw can walk the configured fallback chain. Explicit user selections (for example `/model ollama/qwen3.5:27b`, the model picker, `sessions.patch`, or one-off CLI provider/model overrides) are strict: if that provider/model is unreachable or fails before producing a reply, OpenClaw reports the failure instead of answering from an unrelated fallback.
+When a run starts from the configured default primary, a cron job primary, an agent primary with explicit fallbacks, or an auto-selected fallback override, OpenClaw can walk the matching configured fallback chain. Agent primaries without explicit fallbacks and explicit user selections (for example `/model ollama/qwen3.5:27b`, the model picker, `sessions.patch`, or one-off CLI provider/model overrides) are strict: if that provider/model is unreachable or fails before producing a reply, OpenClaw reports the failure instead of answering from an unrelated fallback.
 
 ### Candidate chain rules
 
diff --git a/docs/gateway/config-agents.md b/docs/gateway/config-agents.md
index 87cbfac7fea..ffd5090301d 100644
--- a/docs/gateway/config-agents.md
+++ b/docs/gateway/config-agents.md
@@ -969,7 +969,7 @@ for provider examples and precedence.
 
 - `id`: stable agent id (required).
 - `default`: when multiple are set, first wins (warning logged). If none set, first list entry is default.
-- `model`: string form overrides `primary` only; object form `{ primary, fallbacks }` overrides both (`[]` disables global fallbacks). Cron jobs that only override `primary` still inherit default fallbacks unless you set `fallbacks: []`.
+- `model`: string form sets a strict per-agent primary with no model fallback; object form `{ primary }` is also strict unless you add `fallbacks`. Use `{ primary, fallbacks: [...] }` to opt that agent into fallback, or `{ primary, fallbacks: [] }` to make strict behavior explicit. Cron jobs that only override `primary` still inherit default fallbacks unless you set `fallbacks: []`.
 - `params`: per-agent stream params merged over the selected model entry in `agents.defaults.models`. Use this for agent-specific overrides like `cacheRetention`, `temperature`, or `maxTokens` without duplicating the whole model catalog.
 - `tts`: optional per-agent text-to-speech overrides. The block deep-merges over `messages.tts`, so keep shared provider credentials and fallback policy in `messages.tts` and set only persona-specific values such as provider, voice, model, style, or auto mode here.
 - `skills`: optional per-agent skill allowlist. If omitted, the agent inherits `agents.defaults.skills` when set; an explicit list replaces defaults instead of merging, and `[]` means no skills.
diff --git a/src/agents/agent-scope.test.ts b/src/agents/agent-scope.test.ts
index 7914ab4da72..d46ceecefe9 100644
--- a/src/agents/agent-scope.test.ts
+++ b/src/agents/agent-scope.test.ts
@@ -182,7 +182,7 @@ describe("resolveAgentConfig", () => {
     expect(resolveAgentEffectiveModelPrimary(cfg, "linus")).toBe("anthropic/claude-sonnet-4-6");
     expect(resolveAgentModelFallbacksOverride(cfg, "linus")).toEqual(["openai/gpt-5.4"]);
 
-    // If fallbacks isn't present, we don't override the global fallbacks.
+    // If an agent owns a primary, missing fallbacks means no model fallback.
     const cfgNoOverride: OpenClawConfig = {
       agents: {
         list: [
@@ -195,7 +195,55 @@ describe("resolveAgentConfig", () => {
         ],
       },
     };
-    expect(resolveAgentModelFallbacksOverride(cfgNoOverride, "linus")).toBe(undefined);
+    expect(resolveAgentModelFallbacksOverride(cfgNoOverride, "linus")).toEqual([]);
+    expect(
+      resolveEffectiveModelFallbacks({
+        cfg: cfgNoOverride,
+        agentId: "linus",
+        hasSessionModelOverride: false,
+      }),
+    ).toEqual([]);
+
+    const cfgStringModel: OpenClawConfig = {
+      agents: {
+        list: [
+          {
+            id: "linus",
+            model: "anthropic/claude-sonnet-4-6",
+          },
+        ],
+      },
+    };
+    expect(resolveAgentModelFallbacksOverride(cfgStringModel, "linus")).toEqual([]);
+
+    const cfgStrictAgentWithDefaultFallbacks: OpenClawConfig = {
+      agents: {
+        defaults: {
+          model: {
+            fallbacks: ["custom-opencode-go-extras/deepseek-v4-flash"],
+          },
+        },
+        list: [
+          {
+            id: "linus",
+            model: {
+              primary: "opencode-go/minimax-m2.7",
+            },
+          },
+        ],
+      },
+    };
+    expect(resolveAgentModelFallbacksOverride(cfgStrictAgentWithDefaultFallbacks, "linus")).toEqual(
+      [],
+    );
+    expect(
+      resolveEffectiveModelFallbacks({
+        cfg: cfgStrictAgentWithDefaultFallbacks,
+        agentId: "linus",
+        hasSessionModelOverride: true,
+        modelOverrideSource: "auto",
+      }),
+    ).toEqual([]);
 
     // Explicit empty list disables global fallbacks for that agent.
     const cfgDisable: OpenClawConfig = {
@@ -251,26 +299,19 @@ describe("resolveAgentConfig", () => {
       }),
     ).toEqual([]);
 
-    const cfgInheritDefaults: OpenClawConfig = {
+    const cfgInheritDefaultsWithoutAgentModel: OpenClawConfig = {
       agents: {
         defaults: {
           model: {
             fallbacks: ["openai/gpt-5.4"],
           },
         },
-        list: [
-          {
-            id: "linus",
-            model: {
-              primary: "anthropic/claude-sonnet-4-6",
-            },
-          },
-        ],
+        list: [{ id: "linus" }],
       },
     };
     expect(
       resolveEffectiveModelFallbacks({
-        cfg: cfgInheritDefaults,
+        cfg: cfgInheritDefaultsWithoutAgentModel,
         agentId: "linus",
         hasSessionModelOverride: true,
         modelOverrideSource: "auto",
diff --git a/src/agents/agent-scope.ts b/src/agents/agent-scope.ts
index 482da5afa9e..9c53e36601e 100644
--- a/src/agents/agent-scope.ts
+++ b/src/agents/agent-scope.ts
@@ -156,12 +156,15 @@ export function resolveAgentModelFallbacksOverride(
   agentId: string,
 ): string[] | undefined {
   const raw = resolveAgentConfig(cfg, agentId)?.model;
-  if (!raw || typeof raw === "string") {
+  if (!raw) {
     return undefined;
   }
+  if (typeof raw === "string") {
+    return resolvePrimaryStringValue(raw) ? [] : undefined;
+  }
   // Important: treat an explicitly provided empty array as an override to disable global fallbacks.
   if (!Object.hasOwn(raw, "fallbacks")) {
-    return undefined;
+    return Object.hasOwn(raw, "primary") && resolvePrimaryStringValue(raw) ? [] : undefined;
   }
   return Array.isArray(raw.fallbacks) ? raw.fallbacks : undefined;
 }