diff --git a/changelog.d/fixes/6943-gemini-thinking-none-effort.md b/changelog.d/fixes/6943-gemini-thinking-none-effort.md
new file mode 100644
index 0000000000..0c6f67f2b9
--- /dev/null
+++ b/changelog.d/fixes/6943-gemini-thinking-none-effort.md
@@ -0,0 +1 @@
+- fix(providers): `openai->gemini` transform now maps `reasoning_effort: "none"` to `thinkingConfig.thinkingBudget: 0` (with `includeThoughts: false`), giving callers an explicit, documented off-switch for Gemini thinking; the no-knob-at-all default injection (#4170) is unchanged (#6813, thanks @rafaumeu)
diff --git a/open-sse/translator/request/__tests__/openai-to-gemini.test.ts b/open-sse/translator/request/__tests__/openai-to-gemini.test.ts
new file mode 100644
index 0000000000..2fad3bfa94
--- /dev/null
+++ b/open-sse/translator/request/__tests__/openai-to-gemini.test.ts
@@ -0,0 +1,97 @@
+import { describe, it, expect } from "vitest";
+import { openaiToGeminiRequest } from "../openai-to-gemini";
+
+describe("translator/request/openai-to-gemini.ts", () => {
+  describe("thinking budget handling (issue #6813)", () => {
+    it("should pass budget_tokens: 0 without dropping to default", () => {
+      // Zero budget yields no thoughts, so includeThoughts is false here — this is
+      // the already-merged #6821 fix for #6813 defect 1 (explicit numeric check,
+      // not truthy, so budget_tokens:0 isn't silently dropped to the default).
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        thinking: { type: "enabled", budget_tokens: 0 },
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBe(0);
+      expect(result.generationConfig?.thinkingConfig?.includeThoughts).toBe(false);
+    });
+
+    it("should pass budget_tokens: 1", () => {
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        thinking: { type: "enabled", budget_tokens: 1 },
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBe(1);
+    });
+
+    it("should still inject default thinkingConfig when no knobs present (#4170)", () => {
+      // Modern Gemini 2.5+ models think by default even with no thinkingConfig sent,
+      // so includeThoughts:true must stay on for the no-knob case or the model's
+      // reasoning leaks into visible content instead of reasoning_content (#4170).
+      // The supported off-switch for the "I don't want to pay for thinking" case
+      // (#6813 defect 2) is the explicit `reasoning_effort: "none"` knob below,
+      // not silent no-knob-at-all suppression.
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.includeThoughts).toBe(true);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBeGreaterThan(0);
+    });
+
+    it("should set thinkingBudget 0 (and includeThoughts false) when reasoning_effort: none", () => {
+      // A zero budget yields no thoughts at all, so includeThoughts is false here —
+      // consistent with the explicit budget_tokens:0 handling above (#6821/#6813).
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        reasoning_effort: "none",
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBe(0);
+      expect(result.generationConfig?.thinkingConfig?.includeThoughts).toBe(false);
+    });
+
+    it("should map reasoning_effort: low to thinkingBudget: 1024", () => {
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        reasoning_effort: "low",
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBe(1024);
+    });
+
+    it("should map reasoning_effort: medium to thinkingBudget: 10240", () => {
+      const body = {
+        model: "custom-model",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        reasoning_effort: "medium",
+      };
+      const result = openaiToGeminiRequest("custom-model", body, false);
+      // medium falls back to getDefaultThinkingBudget which may return 8192
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBeGreaterThanOrEqual(1024);
+    });
+
+    it("should map reasoning_effort: high to thinkingBudget: 24576", () => {
+      const body = {
+        model: "gemini/gemini-2.5-flash",
+        messages: [{ role: "user", content: "hi" }],
+        safetySettings: [],
+        reasoning_effort: "high",
+      };
+      const result = openaiToGeminiRequest("gemini/gemini-2.5-flash", body, false);
+      expect(result.generationConfig?.thinkingConfig?.thinkingBudget).toBe(24576);
+    });
+  });
+});
diff --git a/open-sse/translator/request/openai-to-gemini.ts b/open-sse/translator/request/openai-to-gemini.ts
index 2d3fb8811f..a45fb3232d 100644
--- a/open-sse/translator/request/openai-to-gemini.ts
+++ b/open-sse/translator/request/openai-to-gemini.ts
@@ -195,14 +195,17 @@ function openaiToGeminiBase(
   if (model.startsWith("gemma-4")) {
     // gemma-4 models returns - 400: Thinking budget is not supported for this model
   } else {
-    // 1. OpenAI format: reasoning_effort (low/medium/high/auto/max/xhigh)
+    // 1. OpenAI format: reasoning_effort (none/low/medium/high/auto/max/xhigh)
     // "auto", "max", and "xhigh" are clamped to the high-tier budget because Gemini
     // does not accept these strings directly. "auto" signals "use max reasonable effort"
     // which maps to high. "max"/"xhigh" exceed Gemini's accepted range and are clamped.
+    // "none" maps to budget 0 — an explicit, documented off-switch (#6813 defect 2),
+    // distinct from the no-knob-at-all default-injection case below (#4170).
     // Port of decolua/9router#2043 by @nguyenxvotanminh3.
     if (body.reasoning_effort) {
       const highBudget = capThinkingBudget(model, 32768);
       const budgetMap: Record<string, number> = {
+        none: 0,
         low: 1024,
         medium: getDefaultThinkingBudget(model) || 8192,
         high: highBudget,
@@ -214,7 +217,7 @@ function openaiToGeminiBase(
         budgetMap[body.reasoning_effort as string] ?? getDefaultThinkingBudget(model) ?? 8192;
       result.generationConfig.thinkingConfig = {
         thinkingBudget: budget,
-        includeThoughts: true,
+        includeThoughts: budget !== 0,
       };
     }
     // 2. Claude format: thinking (type: enabled, budget_tokens)
@@ -236,7 +239,9 @@ function openaiToGeminiBase(
   // thinking.type), still set includeThoughts so the upstream marks thought
   // parts with thought:true. Without this, the model's reasoning leaks into
   // visible content instead of being routed to reasoning_content by the
-  // response translator. (#4170)
+  // response translator. (#4170) — this default-injection case is intentionally
+  // unconditional (no-knob-at-all still gets includeThoughts:true); the explicit
+  // "reasoning_effort: none" off-switch above (#6813) is the supported opt-out.
   if (!result.generationConfig.thinkingConfig) {
     const modelLower = model.toLowerCase();
     if (