diff --git a/docs/AB_TESTING.md b/docs/AB_TESTING.md
index 2f0766eb7..6f2cf9757 100644
--- a/docs/AB_TESTING.md
+++ b/docs/AB_TESTING.md
@@ -3,31 +3,23 @@
 A/B testing in Codex shows two translation suggestions side‑by‑side once in a while so you can pick the better one. This helps us learn which retrieval and prompting strategies work best without slowing you down.
 
 ## How it works
-- Triggering: Tests run at random with a small probability (default 15%).
+- Triggering: Tests run at random with a hardcoded probability of 1% (1 in 100). This is defined by `AB_TEST_PROBABILITY` in `src/utils/abTestingRegistry.ts`.
 - Variants: When triggered, two candidates are generated in parallel.
 - Auto‑apply: If the two results are effectively identical, we apply one automatically and no modal is shown.
 - Choosing: If they differ, a simple chooser appears; click the option that reads best. Dismissing the modal after choosing just closes it.
-- Frequency control: In the chooser, “See less/See more” nudges how often you’ll be asked in the future.
 
 ## What’s being compared
 - Search algorithm for few‑shot retrieval: `fts5-bm25` vs `sbs`.
 - Few‑shot example format: `source-and-target` vs `target-only`.
 (Model comparisons are disabled by default.)
 
-## Settings
-- `codex-editor-extension.abTestingEnabled`: turn A/B testing on/off.
-- `codex-editor-extension.abTestingProbability`: probability (0–1) for running a true A/B test. Default: `0.15` (15%).
-
-Change these in VS Code Settings → Extensions → Codex Editor.
-
 ## Results & privacy
 - Local log: Each choice is appended to `files/ab-test-results.jsonl` in your workspace (newline‑delimited JSON).
 - Win rates: The editor may compute simple win‑rates by variant label and show them in the chooser.
 - Network: If analytics posting is enabled in code, the extension may attempt to send anonymized A/B summaries to a configured endpoint. If your environment blocks network access, the extension continues without error.
 
 ## Disable A/B testing
-- Set `codex-editor-extension.abTestingEnabled` to `false`, or
-- Set `codex-editor-extension.abTestingProbability` to `0`.
+Set `AB_TEST_PROBABILITY` to `0` in `src/utils/abTestingRegistry.ts`.
 
 ## Developer pointers (optional)
 - Registry and helpers: `src/utils/abTestingRegistry.ts`, `src/utils/abTestingSetup.ts`.
diff --git a/package.json b/package.json
index ccef3077b..e91b61fe2 100644
--- a/package.json
+++ b/package.json
@@ -931,20 +931,6 @@
                         "default": false,
                         "description": "When enabled, AI will only use translation pairs that have been validated by users as examples for few-shot prompting. This ensures higher quality examples but may reduce the number of available examples."
                     },
-                    "codex-editor-extension.abTestingEnabled": {
-                        "title": "Enable A/B Testing",
-                        "type": "boolean",
-                        "default": true,
-                        "description": "Enables lightweight A/B tests during completions. Tests are globally gated by probability and each comparison shows exactly two options."
-                    },
-                    "codex-editor-extension.abTestingProbability": {
-                        "title": "A/B Testing Probability",
-                        "type": "number",
-                        "default": 0.15,
-                        "minimum": 0,
-                        "maximum": 1,
-                        "description": "Probability (0-1) that any eligible event will run a true A/B test. When not triggered, the system returns identical variants to keep UX consistent without doubling compute."
-                    },
                     "codex-editor-extension.searchAlgorithm": {
                         "title": "Search Algorithm",
                         "type": "string",
diff --git a/src/copilotSettings/copilotSettings.ts b/src/copilotSettings/copilotSettings.ts
index 42aea35ce..168337706 100644
--- a/src/copilotSettings/copilotSettings.ts
+++ b/src/copilotSettings/copilotSettings.ts
@@ -340,7 +340,6 @@ export async function generateChatSystemMessage(
             numberOfFewShotExamples: 0,
             debugMode: false,
             useOnlyValidatedExamples: false,
-            abTestingEnabled: false,
             allowHtmlPredictions: allowHtmlPredictions,
             fewShotExampleFormat: "source-and-target",
         };
diff --git a/src/projectManager/utils/migrationUtils.ts b/src/projectManager/utils/migrationUtils.ts
index 3beb532e3..577c342a2 100644
--- a/src/projectManager/utils/migrationUtils.ts
+++ b/src/projectManager/utils/migrationUtils.ts
@@ -1186,9 +1186,6 @@ export const migration_lineNumbersSettings = async (context?: vscode.ExtensionCo
     }
 };
 
-// Gently migrate A/B testing probability from older explicit 25% to 5% with user consent
-// (removed) migration_abTestingProbabilityDefault — intentionally deleted for now
-
 async function analyzeFileForLineNumbers(fileUri: vscode.Uri): Promise<boolean> {
     try {
         // Read the file content using serializer for proper deserialization
diff --git a/src/providers/translationSuggestions/llmCompletion.ts b/src/providers/translationSuggestions/llmCompletion.ts
index 17215eb4f..b42227efd 100644
--- a/src/providers/translationSuggestions/llmCompletion.ts
+++ b/src/providers/translationSuggestions/llmCompletion.ts
@@ -7,7 +7,7 @@ import { CodexCellTypes } from "../../../types/enums";
 import { getAutoCompleteStatusBarItem } from "../../extension";
 import { tokenizeText } from "../../utils/nlpUtils";
 import { buildFewShotExamplesText, buildMessages, fetchFewShotExamples, getPrecedingTranslationPairs } from "./shared";
-import { abTestingRegistry } from "../../utils/abTestingRegistry";
+import { abTestingRegistry, AB_TEST_PROBABILITY } from "../../utils/abTestingRegistry";
 
 // Helper function to build A/B test context object
 function buildABTestContext(
@@ -249,23 +249,21 @@ export async function llmCompletion(
             // A/B testing is disabled during batch operations (chapter autocomplete, batch transcription)
             // to avoid interrupting the user with variant selection UI
             const extConfig = vscode.workspace.getConfiguration("codex-editor-extension");
-            const abEnabled = Boolean(extConfig.get("abTestingEnabled") ?? true) && !isBatchOperation;
-            const abProbabilityRaw = extConfig.get<number>("abTestingProbability");
-            const abProbability = Math.max(0, Math.min(1, typeof abProbabilityRaw === "number" ? abProbabilityRaw : 0.15));
+            // A/B testing is always enabled but skipped during batch operations.
+            // Probability is hardcoded in AB_TEST_PROBABILITY (single source of truth).
+            const abEnabled = !isBatchOperation;
             const randomValue = Math.random();
-            const triggerAB = abEnabled && randomValue < abProbability;
+            const triggerAB = abEnabled && randomValue < AB_TEST_PROBABILITY;
 
             if (completionConfig.debugMode) {
-                console.debug(`[llmCompletion] A/B testing: enabled=${abEnabled}, isBatchOperation=${isBatchOperation}, probability=${abProbability}, random=${randomValue.toFixed(3)}, trigger=${triggerAB}`);
+                console.debug(`[llmCompletion] A/B testing: enabled=${abEnabled}, isBatchOperation=${isBatchOperation}, probability=${AB_TEST_PROBABILITY}, random=${randomValue.toFixed(3)}, trigger=${triggerAB}`);
             }
 
             if (!triggerAB && completionConfig.debugMode) {
                 if (isBatchOperation) {
                     console.debug(`[llmCompletion] A/B testing disabled during batch operation`);
-                } else if (!abEnabled) {
-                    console.debug(`[llmCompletion] A/B testing disabled in settings`);
                 } else {
-                    console.debug(`[llmCompletion] A/B test not triggered (random ${randomValue.toFixed(3)} >= probability ${abProbability})`);
+                    console.debug(`[llmCompletion] A/B test not triggered (random ${randomValue.toFixed(3)} >= probability ${AB_TEST_PROBABILITY})`);
                 }
             }
 
diff --git a/src/test/suite/validatedOnlyExamples.test.ts b/src/test/suite/validatedOnlyExamples.test.ts
index 1e78ef4b8..1633acbe6 100644
--- a/src/test/suite/validatedOnlyExamples.test.ts
+++ b/src/test/suite/validatedOnlyExamples.test.ts
@@ -117,8 +117,6 @@ suite("Validated-only examples behavior", () => {
             if (section === "codex-editor-extension") {
                 return {
                     get: (key: string) => {
-                        if (key === "abTestingEnabled") return true;
-                        if (key === "abTestingProbability") return 1; // force
                         if (key === "useOnlyValidatedExamples") return true;
                         if (key === "searchAlgorithm") return "sbs";
                         return (cfg as any)?.get?.(key);
diff --git a/src/utils/abTestingRegistry.ts b/src/utils/abTestingRegistry.ts
index 559cad989..3c441d593 100644
--- a/src/utils/abTestingRegistry.ts
+++ b/src/utils/abTestingRegistry.ts
@@ -1,3 +1,9 @@
+/**
+ * Probability (0–1) that any eligible completion triggers a local A/B test.
+ * 0.01 = 1 in 100.  Change this single constant to adjust frequency everywhere.
+ */
+export const AB_TEST_PROBABILITY = 0.01;
+
 type ABTestResultPayload<TVariant> = TVariant[] | {
   variants: TVariant[];
   isAttentionCheck?: boolean;
diff --git a/src/utils/llmUtils.ts b/src/utils/llmUtils.ts
index 85fddca98..584d240f4 100644
--- a/src/utils/llmUtils.ts
+++ b/src/utils/llmUtils.ts
@@ -340,7 +340,6 @@ export interface CompletionConfig {
     numberOfFewShotExamples: number;
     debugMode: boolean;
     useOnlyValidatedExamples: boolean;
-    abTestingEnabled: boolean; // legacy flag; kept for type compatibility
     allowHtmlPredictions?: boolean; // whether to preserve HTML in examples and predictions
     fewShotExampleFormat: string; // format for few-shot examples: 'source-and-target' or 'target-only'
 }
@@ -369,8 +368,6 @@ export async function fetchCompletionConfig(): Promise<CompletionConfig> {
             numberOfFewShotExamples: (config.get("numberOfFewShotExamples") as number) || 30,
             debugMode: config.get("debugMode") === true || config.get("debugMode") === "true",
             useOnlyValidatedExamples: useOnlyValidatedExamples as boolean,
-            // A/B testing flag kept for compatibility; registry handles gating
-            abTestingEnabled: (config.get("abTestingEnabled") as boolean) ?? true,
             allowHtmlPredictions: (config.get("allowHtmlPredictions") as boolean) || false,
             fewShotExampleFormat: (config.get("fewShotExampleFormat") as string) || "source-and-target",
         };
diff --git a/types/index.d.ts b/types/index.d.ts
index 676bed2f6..accc8bc3b 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -2163,8 +2163,7 @@ type EditorReceiveMessages =
     }
     | { type: "providerUpdatesTextDirection"; textDirection: "ltr" | "rtl"; }
     | { type: "providerSendsLLMCompletionResponse"; content: { completion: string; cellId: string; }; }
-    | { type: "providerSendsABTestVariants"; content: { variants: string[]; cellId: string; testId: string; testName?: string; names?: string[]; abProbability?: number; }; }
-    | { type: "abTestingProbabilityUpdated"; content: { value: number; }; }
+    | { type: "providerSendsABTestVariants"; content: { variants: string[]; cellId: string; testId: string; testName?: string; names?: string[]; }; }
     | { type: "jumpToSection"; content: string; }
     | { type: "providerUpdatesNotebookMetadataForWebview"; content: CustomNotebookMetadata; }
     | { type: "updateVideoUrlInWebview"; content: string; }
diff --git a/webviews/codex-webviews/src/CodexCellEditor/CodexCellEditor.tsx b/webviews/codex-webviews/src/CodexCellEditor/CodexCellEditor.tsx
index 66a9c80e9..6951e675a 100755
--- a/webviews/codex-webviews/src/CodexCellEditor/CodexCellEditor.tsx
+++ b/webviews/codex-webviews/src/CodexCellEditor/CodexCellEditor.tsx
@@ -355,7 +355,6 @@ const CodexCellEditor: React.FC = () => {
         testId: string;
         testName?: string;
         names?: string[];
-        abProbability?: number;
     }>({
         isActive: false,
         variants: [],
@@ -1373,7 +1372,7 @@ const CodexCellEditor: React.FC = () => {
         },
         setAudioAttachments: setAudioAttachments,
         showABTestVariants: (data) => {
-            const { variants, cellId, testId, testName, names, abProbability } = data as any;
+            const { variants, cellId, testId, testName, names } = data as any;
             const count = Array.isArray(variants) ? variants.length : 0;
             debug("ab-test", "Received A/B test variants:", { cellId, count });
 
@@ -1423,7 +1422,6 @@ const CodexCellEditor: React.FC = () => {
                     testId,
                     testName,
                     names,
-                    abProbability,
                 });
                 return;
             }