fix(tui): resolve wrong provider prefix when session has model without modelProvider (#25874)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: f0953a7284
Co-authored-by: lbo728 <72309817+lbo728@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/agents/model-selection.test.ts

@@ -3,6 +3,7 @@ import type { OpenClawConfig } from "../config/config.js";
 import { resetLogger, setLoggerOverride } from "../logging/logger.js";
 import {
   buildAllowedModelSet,
+  inferUniqueProviderFromConfiguredModels,
   parseModelRef,
   buildModelAliasIndex,
   modelKey,
@@ -134,6 +135,85 @@ describe("model-selection", () => {
     });
   });
 
+  describe("inferUniqueProviderFromConfiguredModels", () => {
+    it("infers provider when configured model match is unique", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            models: {
+              "anthropic/claude-sonnet-4-6": {},
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      expect(
+        inferUniqueProviderFromConfiguredModels({
+          cfg,
+          model: "claude-sonnet-4-6",
+        }),
+      ).toBe("anthropic");
+    });
+
+    it("returns undefined when configured matches are ambiguous", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            models: {
+              "anthropic/claude-sonnet-4-6": {},
+              "minimax/claude-sonnet-4-6": {},
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      expect(
+        inferUniqueProviderFromConfiguredModels({
+          cfg,
+          model: "claude-sonnet-4-6",
+        }),
+      ).toBeUndefined();
+    });
+
+    it("returns undefined for provider-prefixed model ids", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            models: {
+              "anthropic/claude-sonnet-4-6": {},
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      expect(
+        inferUniqueProviderFromConfiguredModels({
+          cfg,
+          model: "anthropic/claude-sonnet-4-6",
+        }),
+      ).toBeUndefined();
+    });
+
+    it("infers provider for slash-containing model id when allowlist match is unique", () => {
+      const cfg = {
+        agents: {
+          defaults: {
+            models: {
+              "vercel-ai-gateway/anthropic/claude-sonnet-4-6": {},
+            },
+          },
+        },
+      } as OpenClawConfig;
+
+      expect(
+        inferUniqueProviderFromConfiguredModels({
+          cfg,
+          model: "anthropic/claude-sonnet-4-6",
+        }),
+      ).toBe("vercel-ai-gateway");
+    });
+  });
+
   describe("buildModelAliasIndex", () => {
     it("should build alias index from config", () => {
       const cfg: Partial<OpenClawConfig> = {