Fix DeepSeek reasoning error.

docs/sdk-model-catalog/implementation-plan.md

@@ -564,8 +564,9 @@ Uncomment each and confirm the call site compiles against the contract. If anyth
 - Read `src/core/api/providers/deepseek.ts`. Confirm `getModel()` reads `modelId`/`modelInfo` from passed-in config, not a static map.
 - If a static-map lookup exists, replace with read from passed-in config. Add test: `getModel().info` equals the passed-in info.
 - Verify `cline-session-factory.ts` resolves provider config via `ProviderConfigStore` and snapshots at task start.
+- Audit every auxiliary field the legacy provider panel could set, not just `modelId`/`modelInfo`. For DeepSeek this includes reasoning/thinking state (`enabled`, `effort`, and budget tokens). The migrated runtime must either carry each auxiliary field through the SDK provider settings/session config coherently, or explicitly document that field as out of scope for the picker migration. In particular, disabled thinking must clear any orphaned reasoning effort before inference; otherwise provider switches can tear configuration across providers.
 
-**Exit:** Runtime test passes. `cline-session-factory` does not import `deepSeekModels`.
+**Exit:** Runtime test passes. `cline-session-factory` does not import `deepSeekModels`. Auxiliary-field tests prove DeepSeek does not send contradictory thinking/reasoning options after switching from a provider with reasoning enabled.
 
 ### Step 6.3 — End-to-end live test
 

src/sdk/cline-session-factory.test.ts

@@ -8,6 +8,7 @@ import {
 	buildStartSessionInput,
 	createHistoryItemFromSession,
 	getHistoryItemById,
+	normalizeProviderReasoningSettings,
 	updateHistoryItem,
 } from "./cline-session-factory"
 
@@ -123,6 +124,36 @@ describe("buildResumeSessionInput", () => {
 	})
 })
 
+// ---------------------------------------------------------------------------
+// normalizeProviderReasoningSettings
+// ---------------------------------------------------------------------------
+
+describe("normalizeProviderReasoningSettings", () => {
+	it("does not emit reasoningEffort when thinking is disabled", () => {
+		const result = normalizeProviderReasoningSettings({ enabled: false, effort: "medium" })
+
+		expect(result).toEqual({ thinking: false })
+	})
+
+	it("treats effort none as disabled thinking", () => {
+		const result = normalizeProviderReasoningSettings({ effort: "none" })
+
+		expect(result).toEqual({ thinking: false })
+	})
+
+	it("passes enabled reasoning with a concrete effort", () => {
+		const result = normalizeProviderReasoningSettings({ enabled: true, effort: "high" })
+
+		expect(result).toEqual({ thinking: true, reasoningEffort: "high" })
+	})
+
+	it("leaves explicit effort-only settings enabled by SDK/provider defaults", () => {
+		const result = normalizeProviderReasoningSettings({ effort: "medium" })
+
+		expect(result).toEqual({ reasoningEffort: "medium" })
+	})
+})
+
 // ---------------------------------------------------------------------------
 // createHistoryItemFromSession
 // ---------------------------------------------------------------------------

src/sdk/cline-session-factory.ts

@@ -8,7 +8,12 @@
 //
 // The factory does NOT handle UI concerns — that's the SdkController's job.
 
-import { type ClineCoreStartInput, type CoreSessionConfig, type StartSessionResult } from "@cline/core"
+import {
+	type ClineCoreStartInput,
+	type CoreSessionConfig,
+	type ProviderSettings,
+	type StartSessionResult,
+} from "@cline/core"
 import { buildClineSystemPrompt } from "@cline/shared"
 import type { ApiConfiguration } from "@shared/api"
 import type { HistoryItem } from "@shared/HistoryItem"
@@ -106,6 +111,67 @@ function resolveWorkspaceName(workspacePath: string): string {
 	return name || "workspace"
 }
 
+type ReasoningEffort = NonNullable<CoreSessionConfig["reasoningEffort"]>
+type ProviderReasoningSettings = NonNullable<ProviderSettings["reasoning"]>
+type SessionReasoningConfig = Pick<CoreSessionConfig, "thinking" | "reasoningEffort">
+
+function isReasoningEffort(value: unknown): value is ReasoningEffort {
+	return value === "low" || value === "medium" || value === "high" || value === "xhigh"
+}
+
+function hasStaleDisabledReasoningFields(reasoning: ProviderReasoningSettings | undefined): boolean {
+	return reasoning?.enabled === false && (reasoning.effort !== undefined || reasoning.budgetTokens !== undefined)
+}
+
+/**
+ * Convert SDK provider-level reasoning settings into the SDK session fields that
+ * are actually forwarded as model options. Keep `thinking` and
+ * `reasoningEffort` coherent: a disabled/none state must never carry an effort.
+ */
+export function normalizeProviderReasoningSettings(reasoning: ProviderReasoningSettings | undefined): SessionReasoningConfig {
+	if (!reasoning) {
+		return {}
+	}
+
+	if (reasoning.enabled === false || reasoning.effort === "none") {
+		return { thinking: false }
+	}
+
+	if (reasoning.enabled === true) {
+		return {
+			thinking: true,
+			...(isReasoningEffort(reasoning.effort) ? { reasoningEffort: reasoning.effort } : {}),
+		}
+	}
+
+	return isReasoningEffort(reasoning.effort) ? { reasoningEffort: reasoning.effort } : {}
+}
+
+function resolveProviderReasoningConfig(providerId: string): SessionReasoningConfig {
+	try {
+		const manager = getProviderSettingsManager(resolveDataDir())
+		const settings = manager.getProviderSettings(providerId)
+		if (!settings) {
+			return {}
+		}
+
+		if (hasStaleDisabledReasoningFields(settings.reasoning)) {
+			const sanitizedSettings: ProviderSettings = {
+				...settings,
+				reasoning: { enabled: false },
+			}
+			manager.saveProviderSettings(sanitizedSettings, { setLastUsed: false })
+			Logger.warn(`[SessionFactory] Cleared stale disabled reasoning fields for provider=${providerId}`)
+			return normalizeProviderReasoningSettings(sanitizedSettings.reasoning)
+		}
+
+		return normalizeProviderReasoningSettings(settings.reasoning)
+	} catch (error) {
+		Logger.warn("[SessionFactory] Provider reasoning resolution failed:", error)
+		return {}
+	}
+}
+
 // ---------------------------------------------------------------------------
 // Provider → API key field mapping
 // ---------------------------------------------------------------------------
@@ -365,6 +431,7 @@ export async function buildSessionConfig(input: SessionConfigInput): Promise<Cor
 	providerId = providerId ?? "cline"
 	modelId = modelId ?? "openai/gpt-5.4"
 	apiKey = apiKey ?? ""
+	const reasoningConfig = resolveProviderReasoningConfig(providerId)
 
 	// Build the system prompt using the shared prompt builder. Core still
 	// expects callers to provide a concrete systemPrompt, but the prompt builder
@@ -423,7 +490,7 @@ export async function buildSessionConfig(input: SessionConfigInput): Promise<Cor
 		enableAgentTeams: false,
 		disableMcpSettingsTools: true,
 		mode: mode === "plan" ? "plan" : "act",
-		thinking: false,
+		...reasoningConfig,
 		maxIterations: undefined,
 		logger: sdkLogger,
 		extensionContext: {