diff --git a/packages/core/src/tools/edit.ts b/packages/core/src/tools/edit.ts
index cbf151bfc7..c00ea4c0da 100644
--- a/packages/core/src/tools/edit.ts
+++ b/packages/core/src/tools/edit.ts
@@ -28,7 +28,6 @@ import { buildFilePathArgsPattern } from '../policy/utils.js';
 import type { MessageBus } from '../confirmation-bus/message-bus.js';
 import { ToolErrorType } from './tool-error.js';
 import { makeRelative, shortenPath } from '../utils/paths.js';
-import { resolvePlanPath } from '../utils/planUtils.js';
 import { isNodeError } from '../utils/errors.js';
 import { correctPath } from '../utils/pathCorrector.js';
 import type { Config } from '../config/config.js';
diff --git a/packages/core/src/tools/exit-plan-mode.ts b/packages/core/src/tools/exit-plan-mode.ts
index 5318e56889..86d3cccd6f 100644
--- a/packages/core/src/tools/exit-plan-mode.ts
+++ b/packages/core/src/tools/exit-plan-mode.ts
@@ -226,28 +226,19 @@ export class ExitPlanModeInvocation extends BaseToolInvocation<
       const exitMessage = getPlanModeExitMessage(newMode);
 
       return {
-        llmContent: `${exitMessage}
- 
-The approved implementation plan is stored at: ${resolvedPlanPath}
-Read and follow the plan strictly during implementation.`,
+        llmContent: `${exitMessage}\n\nThe approved implementation plan is stored at: ${resolvedPlanPath}\nRead and follow the plan strictly during implementation.`,
         returnDisplay: `Plan approved: ${resolvedPlanPath}`,
       };
     } else {
       const feedback = payload?.feedback?.trim();
       if (feedback) {
         return {
-          llmContent: `Plan rejected. User feedback: ${feedback}
- 
-The plan is stored at: ${resolvedPlanPath}
-Revise the plan based on the feedback.`,
+          llmContent: `Plan rejected. User feedback: ${feedback}\n\nThe plan is stored at: ${resolvedPlanPath}\nRevise the plan based on the feedback.`,
           returnDisplay: `Feedback: ${feedback}`,
         };
       } else {
         return {
-          llmContent: `Plan rejected. No feedback provided.
- 
-The plan is stored at: ${resolvedPlanPath}
-Ask the user for specific feedback on how to improve the plan.`,
+          llmContent: `Plan rejected. No feedback provided.\n\nThe plan is stored at: ${resolvedPlanPath}\nAsk the user for specific feedback on how to improve the plan.`,
           returnDisplay: 'Rejected (no feedback)',
         };
       }
diff --git a/packages/core/src/tools/write-file.test.ts b/packages/core/src/tools/write-file.test.ts
index e276f1f792..0e889ddd90 100644
--- a/packages/core/src/tools/write-file.test.ts
+++ b/packages/core/src/tools/write-file.test.ts
@@ -1176,6 +1176,10 @@ describe('WriteFileTool', () => {
       const planFilePath = `${plansDirName}/tracks/fibsqrt_20260519/spec.md`;
       const params = { file_path: planFilePath, content: '# Spec' };
       const invocation = tool.build(params);
+
+      expect(
+        (invocation as unknown as { resolvedPath: string }).resolvedPath,
+      ).toBe(path.resolve(plansDir, 'tracks/fibsqrt_20260519/spec.md'));
     });
   });
 });
diff --git a/packages/core/src/tools/write-file.ts b/packages/core/src/tools/write-file.ts
index 080b3f1bf8..9ec19b879f 100644
--- a/packages/core/src/tools/write-file.ts
+++ b/packages/core/src/tools/write-file.ts
@@ -29,7 +29,6 @@ import {
 import { buildFilePathArgsPattern } from '../policy/utils.js';
 import { ToolErrorType } from './tool-error.js';
 import { makeRelative, shortenPath } from '../utils/paths.js';
-import { resolvePlanPath } from '../utils/planUtils.js';
 import { getErrorMessage, isNodeError } from '../utils/errors.js';
 import { ensureCorrectFileContent } from '../utils/editCorrector.js';
 import { detectLineEnding } from '../utils/textUtils.js';
diff --git a/packages/core/src/utils/planUtils.test.ts b/packages/core/src/utils/planUtils.test.ts
index 5cf6ce0bc8..56719c6fd3 100644
--- a/packages/core/src/utils/planUtils.test.ts
+++ b/packages/core/src/utils/planUtils.test.ts
@@ -11,7 +11,7 @@ import os from 'node:os';
 import {
   validatePlanPath,
   validatePlanContent,
-  resolvePlanPath,
+  resolveAndValidatePlanPath,
 } from './planUtils.js';
 
 describe('planUtils', () => {
@@ -80,9 +80,9 @@ describe('planUtils', () => {
     });
   });
 
-  describe('resolvePlanPath', () => {
+  describe('resolveAndValidatePlanPath', () => {
     it('should resolve simple filenames relative to plansDir', () => {
-      const result = resolvePlanPath(
+      const result = resolveAndValidatePlanPath(
         'implementation_plan.md',
         plansDir,
         tempRootDir,
@@ -97,7 +97,7 @@ describe('planUtils', () => {
         'fibsqrt_20260519',
         'spec.md',
       );
-      const result = resolvePlanPath(planPath, plansDir, tempRootDir);
+      const result = resolveAndValidatePlanPath(planPath, plansDir, tempRootDir);
       expect(result).toBe(
         path.join(plansDir, 'tracks', 'fibsqrt_20260519', 'spec.md'),
       );
@@ -105,16 +105,17 @@ describe('planUtils', () => {
 
     it('should resolve paths relative to plansDir if they contain subdirectories', () => {
       const planPath = path.join('tracks', 'fibsqrt_20260519', 'spec.md');
-      const result = resolvePlanPath(planPath, plansDir, tempRootDir);
+      const result = resolveAndValidatePlanPath(planPath, plansDir, tempRootDir);
       expect(result).toBe(
         path.join(plansDir, 'tracks', 'fibsqrt_20260519', 'spec.md'),
       );
     });
 
-    it('should fallback to safe basename when escaping', () => {
+    it('should throw access denied when escaping', () => {
       const planPath = '../../escaped.md';
-      const result = resolvePlanPath(planPath, plansDir, tempRootDir);
-      expect(result).toBe(path.join(plansDir, 'escaped.md'));
+      expect(() =>
+        resolveAndValidatePlanPath(planPath, plansDir, tempRootDir),
+      ).toThrow(/Access denied/);
     });
   });
 
diff --git a/packages/core/src/utils/planUtils.ts b/packages/core/src/utils/planUtils.ts
index a1a869edd0..39750ea954 100644
--- a/packages/core/src/utils/planUtils.ts
+++ b/packages/core/src/utils/planUtils.ts
@@ -22,6 +22,14 @@ export const PlanErrorMessages = {
   READ_FAILURE: (detail: string) => `Failed to read plan file: ${detail}`,
 } as const;
 
+/**
+ * Resolves a plan file path and strictly validates it against the plans directory boundary.
+ * Useful for tools that need to write or read plans.
+ * @param planPath The untrusted file path provided by the model.
+ * @param plansDir The authorized project plans directory.
+ * @returns The safely resolved path string.
+ * @throws Error if the path is empty, malicious, or escapes boundaries.
+ */
 export function resolveAndValidatePlanPath(
   planPath: string,
   plansDir: string,