diff --git a/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts b/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
index 155370da1757d..6d87fb75aa190 100644
--- a/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
+++ b/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
@@ -4879,7 +4879,7 @@ describe("ClaudeAdapterV2 background wake turns", () => {
       turn: Effect.Success<ReturnType<typeof openPlanTurn>>,
       toolName: string,
       toolInput: Record<string, unknown>,
-      options?: { toolUseID: string; agentID?: string },
+      options?: { toolUseID: string; agentID?: string; decisionReasonType?: "mode" | "hook" },
     ) {
       const decision = yield* Effect.promise(() =>
         turn.canUseTool(toolName, toolInput, {
@@ -4887,6 +4887,9 @@ describe("ClaudeAdapterV2 background wake turns", () => {
           toolUseID: options?.toolUseID ?? "tool-plan-write",
           requestId: "request-plan-write",
           ...(options?.agentID === undefined ? {} : { agentID: options.agentID }),
+          ...(options?.decisionReasonType === undefined
+            ? {}
+            : { decisionReasonType: options.decisionReasonType }),
         }),
       ).pipe(Effect.forkScoped);
       const first = yield* Effect.raceFirst(
@@ -4950,6 +4953,55 @@ describe("ClaudeAdapterV2 background wake turns", () => {
         ),
     );
 
+    // regression: #23918 the CLI asks again in Plan despite the session rule it was given
+    it.effect("does not ask again for an MCP tool approved for the session in Plan", () =>
+      Effect.gen(function* () {
+        const turn = yield* openPlanTurn("full-access");
+        const toolName = "mcp__t3-code__t3_thread_read";
+        const first = yield* requestWrite(
+          turn,
+          toolName,
+          { threadId: "thread-a", afterPosition: -1 },
+          { toolUseID: "read-page-1", decisionReasonType: "mode" },
+        );
+        assert.equal(first.first.type, "request");
+        if (first.first.type !== "request") return;
+        yield* turn.runtime.respondToRuntimeRequest({
+          requestId: first.first.event.runtimeRequest.id,
+          decision: "acceptForSession",
+        });
+        assert.equal((yield* Fiber.join(first.decision))?.behavior, "allow");
+
+        const second = yield* requestWrite(
+          turn,
+          toolName,
+          { threadId: "thread-a", afterPosition: 1 },
+          { toolUseID: "read-page-2", decisionReasonType: "mode" },
+        );
+        assert.equal(second.first.type, "decision", "the session approval asked again");
+        if (second.first.type !== "decision") return;
+        assert.equal(second.first.result?.behavior, "allow");
+
+        const hooked = yield* requestWrite(
+          turn,
+          toolName,
+          { threadId: "thread-a", afterPosition: 3 },
+          { toolUseID: "read-page-3", decisionReasonType: "hook" },
+        );
+        assert.equal(hooked.first.type, "request", "a hook's ask was answered from the grant");
+      }).pipe(
+        Effect.scoped,
+        Effect.provide(
+          Layer.mergeAll(
+            IdAllocator.layer,
+            McpProviderSessions.layer,
+            NodeServices.layer,
+            NodeCrypto.layer,
+          ),
+        ),
+      ),
+    );
+
     it.effect("denies Plan writes without asking when approvals are never allowed", () =>
       Effect.gen(function* () {
         const turn = yield* openPlanTurn("full-access", "never");
diff --git a/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts b/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
index b3c1fd1c1fed4..6419397238d7a 100644
--- a/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
+++ b/apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
@@ -5629,6 +5629,8 @@ export const makeClaudeAdapterV2 = Effect.fn("makeClaudeAdapterV2")(function* (
           new Map<string, PendingClaudeRuntimeRequest>(),
         );
         const mcpElicitationSessionGrants = yield* Ref.make(new Set<string>());
+        // Plan asks for a tool without a read-only annotation even when a session rule allows it.
+        const planSessionToolGrants = yield* Ref.make(new Set<string>());
         // Background local_bash tasks can trigger wake turns on the query stream with no active provider turn.
         const lastTurnRouteByNativeThread = yield* Ref.make(
           new Map<
@@ -11677,6 +11679,22 @@ export const makeClaudeAdapterV2 = Effect.fn("makeClaudeAdapterV2")(function* (
             } satisfies PermissionResult;
           }
 
+          // The SDK passes decisionReasonType but leaves it out of its types. Only the mode's own
+          // ask is answered from a grant: a hook, an ask rule or a safety check still asks.
+          if (
+            "decisionReasonType" in callbackOptions &&
+            callbackOptions.decisionReasonType === "mode" &&
+            callbackOptions.matchedAskRule === undefined &&
+            callbackOptions.suppressAlwaysAllowRule !== true &&
+            (yield* Ref.get(planSessionToolGrants)).has(toolName)
+          ) {
+            return {
+              behavior: "allow",
+              updatedInput: toolInput,
+              toolUseID: callbackOptions.toolUseID,
+            } satisfies PermissionResult;
+          }
+
           const requestKind = providerRequestKindFromClaudeTool(toolName);
           // The user approves the command itself; Claude's title and description only summarize it.
           const command = inputRecordValue(nativeToolInput, "command");
@@ -11743,7 +11761,7 @@ export const makeClaudeAdapterV2 = Effect.fn("makeClaudeAdapterV2")(function* (
           );
           if (!(yield* Deferred.isDone(decision))) yield* cancelWithdrawnRequest(artifacts);
 
-          return permissionResultFromDecision({
+          const result = permissionResultFromDecision({
             toolName,
             ...resolvedDecision,
             toolInput,
@@ -11753,6 +11771,20 @@ export const makeClaudeAdapterV2 = Effect.fn("makeClaudeAdapterV2")(function* (
               ? {}
               : { suggestions: callbackOptions.suggestions }),
           });
+          if (
+            result.behavior === "allow" &&
+            result.updatedPermissions?.some(
+              (update) =>
+                update.type === "addRules" &&
+                update.behavior === "allow" &&
+                update.rules.some(
+                  (rule) => rule.toolName === toolName && rule.ruleContent === undefined,
+                ),
+            ) === true
+          ) {
+            yield* Ref.update(planSessionToolGrants, (current) => new Set(current).add(toolName));
+          }
+          return result;
         });
 
         const canUseTool: CanUseTool = (toolName, toolInput, callbackOptions) =>