diff --git a/action.yml b/action.yml
index da07125..1782a5b 100644
--- a/action.yml
+++ b/action.yml
@@ -108,9 +108,8 @@ runs:
           taskbound_args+=(--scope-llm "$scope_llm")
         fi
 
-        node "$GITHUB_ACTION_PATH/dist/index.js" "${taskbound_args[@]}" --format markdown | tee "$report_file"
-        node "$GITHUB_ACTION_PATH/dist/index.js" "${taskbound_args[@]}" --format json > "$json_file"
-        node "$GITHUB_ACTION_PATH/dist/index.js" "${taskbound_args[@]}" --format github
+        node "$GITHUB_ACTION_PATH/dist/index.js" "${taskbound_args[@]}" --format github --markdown-output "$report_file" --json-output "$json_file"
+        cat "$report_file"
 
         if [ -n "${GITHUB_STEP_SUMMARY:-}" ]; then
           cat "$report_file" >> "$GITHUB_STEP_SUMMARY"
diff --git a/src/index.ts b/src/index.ts
index 1d215f0..9f566ec 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,9 @@
 #!/usr/bin/env node
 
+import { writeFile } from 'node:fs/promises';
 import { fileURLToPath } from 'node:url';
 import { renderReport, type ReportFormat } from './report.js';
+import type { BoundReport } from './report.js';
 import { runTaskReview } from './review.js';
 import { resolveTaskSource } from './task-source.js';
 
@@ -56,10 +58,21 @@ async function runReviewCommand(argv: string[]): Promise<number> {
           scopeLlmModel: parsed.scopeLlmModel
         });
 
+  await writeSupplementalOutputs(report, parsed);
   process.stdout.write(renderReport(report, parsed.format));
   return 0;
 }
 
+async function writeSupplementalOutputs(
+  report: BoundReport,
+  options: { markdownOutput?: string; jsonOutput?: string }
+): Promise<void> {
+  await Promise.all([
+    options.markdownOutput ? writeFile(options.markdownOutput, renderReport(report, 'markdown'), 'utf8') : undefined,
+    options.jsonOutput ? writeFile(options.jsonOutput, renderReport(report, 'json'), 'utf8') : undefined
+  ]);
+}
+
 type ParsedReviewArgs =
   | {
       ok: true;
@@ -68,6 +81,8 @@ type ParsedReviewArgs =
       githubEventPath?: string;
       scopeContext?: string;
       scopeLlmModel?: string;
+      markdownOutput?: string;
+      jsonOutput?: string;
       oldRoot: string;
       newRoot: string;
       format: ReportFormat;
@@ -79,6 +94,8 @@ type ParsedReviewArgs =
       githubEventPath?: string;
       scopeContext?: string;
       scopeLlmModel?: string;
+      markdownOutput?: string;
+      jsonOutput?: string;
       repo: string;
       base: string;
       head: string;
@@ -91,6 +108,8 @@ function parseReviewArgs(argv: string[]): ParsedReviewArgs {
   let githubEventPath: string | undefined;
   let scopeContext: string | undefined;
   let scopeLlmModel: string | undefined;
+  let markdownOutput: string | undefined;
+  let jsonOutput: string | undefined;
   let oldRoot: string | undefined;
   let newRoot: string | undefined;
   let base: string | undefined;
@@ -114,6 +133,18 @@ function parseReviewArgs(argv: string[]): ParsedReviewArgs {
     } else if (arg === '--scope-llm') {
       scopeLlmModel = value;
       index += 1;
+    } else if (arg === '--markdown-output') {
+      if (!value) {
+        return { ok: false, error: 'Missing required --markdown-output <file> argument.' };
+      }
+      markdownOutput = value;
+      index += 1;
+    } else if (arg === '--json-output') {
+      if (!value) {
+        return { ok: false, error: 'Missing required --json-output <file> argument.' };
+      }
+      jsonOutput = value;
+      index += 1;
     } else if (arg === '--old') {
       oldRoot = value;
       index += 1;
@@ -156,7 +187,20 @@ function parseReviewArgs(argv: string[]): ParsedReviewArgs {
       return { ok: false, error: 'Missing required --head <ref> argument.' };
     }
 
-    return { ok: true, mode: 'git', task, githubEventPath, scopeContext, scopeLlmModel, repo, base, head, format };
+    return {
+      ok: true,
+      mode: 'git',
+      task,
+      githubEventPath,
+      scopeContext,
+      scopeLlmModel,
+      markdownOutput,
+      jsonOutput,
+      repo,
+      base,
+      head,
+      format
+    };
   }
 
   if (!oldRoot) {
@@ -167,7 +211,19 @@ function parseReviewArgs(argv: string[]): ParsedReviewArgs {
     return { ok: false, error: 'Missing required --new <dir> argument.' };
   }
 
-  return { ok: true, mode: 'directories', task, githubEventPath, scopeContext, scopeLlmModel, oldRoot, newRoot, format };
+  return {
+    ok: true,
+    mode: 'directories',
+    task,
+    githubEventPath,
+    scopeContext,
+    scopeLlmModel,
+    markdownOutput,
+    jsonOutput,
+    oldRoot,
+    newRoot,
+    format
+  };
 }
 
 function isReportFormat(value: string | undefined): value is ReportFormat {
@@ -183,8 +239,8 @@ if (invokedPath) {
 function usage(): string {
   return [
     'Usage:',
-    '  taskbound review --task "<stated task>" [--scope-context "<extra context>"] [--scope-llm <model>] --old <dir> --new <dir> [--format text|markdown|json|github]',
-    '  taskbound review --task "<stated task>" [--scope-context "<extra context>"] [--scope-llm <model>] --repo <repo> --base <ref> --head <ref> [--format text|markdown|json|github]',
-    '  taskbound review --github-event <event.json> [--scope-llm <model>] --repo <repo> --base <ref> --head <ref> [--format text|markdown|json|github]'
+    '  taskbound review --task "<stated task>" [--scope-context "<extra context>"] [--scope-llm <model>] --old <dir> --new <dir> [--format text|markdown|json|github] [--markdown-output <file>] [--json-output <file>]',
+    '  taskbound review --task "<stated task>" [--scope-context "<extra context>"] [--scope-llm <model>] --repo <repo> --base <ref> --head <ref> [--format text|markdown|json|github] [--markdown-output <file>] [--json-output <file>]',
+    '  taskbound review --github-event <event.json> [--scope-llm <model>] --repo <repo> --base <ref> --head <ref> [--format text|markdown|json|github] [--markdown-output <file>] [--json-output <file>]'
   ].join('\n');
 }
diff --git a/test/cli-output.test.mjs b/test/cli-output.test.mjs
index f40675f..d36e82b 100644
--- a/test/cli-output.test.mjs
+++ b/test/cli-output.test.mjs
@@ -1,6 +1,8 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
 import { execFile } from 'node:child_process';
+import { mkdtemp, readFile, rm } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
 import { promisify } from 'node:util';
 import { fileURLToPath } from 'node:url';
 import { dirname, join } from 'node:path';
@@ -74,6 +76,47 @@ test('CLI emits GitHub warning annotations', async () => {
   assert.match(stdout, /::warning file=\.github\/workflows\/ci\.yml/);
 });
 
+test('CLI writes supplemental report files from one review', async () => {
+  const oldDir = join(testDir, 'fixtures', 'scope-creep', 'old');
+  const newDir = join(testDir, 'fixtures', 'scope-creep', 'new');
+  const outputDir = await mkdtemp(join(tmpdir(), 'taskbound-output-'));
+  const markdownOutput = join(outputDir, 'taskbound-report.md');
+  const jsonOutput = join(outputDir, 'taskbound-report.json');
+
+  try {
+    const { stdout } = await execFileAsync(
+      process.execPath,
+      [
+        'dist/index.js',
+        'review',
+        '--task',
+        TASK,
+        '--old',
+        oldDir,
+        '--new',
+        newDir,
+        '--format',
+        'github',
+        '--markdown-output',
+        markdownOutput,
+        '--json-output',
+        jsonOutput
+      ],
+      { cwd: packageRoot }
+    );
+
+    const markdown = await readFile(markdownOutput, 'utf8');
+    const json = JSON.parse(await readFile(jsonOutput, 'utf8'));
+
+    assert.match(stdout, /::warning file=\.mcp\.json/);
+    assert.match(markdown, /# TaskBound scope review: CRITICAL/);
+    assert.equal(json.rating, 'critical');
+    assert.ok(json.findings.some((finding) => finding.kind === 'script_pipe_to_shell'));
+  } finally {
+    await rm(outputDir, { recursive: true, force: true });
+  }
+});
+
 test('CLI uses GitHub pull request body as additional scope context', async () => {
   const oldDir = join(testDir, 'fixtures', 'scope-creep', 'old');
   const newDir = join(testDir, 'fixtures', 'scope-creep', 'new');
diff --git a/test/workflow.test.mjs b/test/workflow.test.mjs
index 8789ffc..f3fadf8 100644
--- a/test/workflow.test.mjs
+++ b/test/workflow.test.mjs
@@ -9,6 +9,8 @@ const packageRoot = join(testDir, '..');
 
 test('action.yml can derive task scope from pull request event context', async () => {
   const action = await readFile(join(packageRoot, 'action.yml'), 'utf8');
+  const reviewInvocations = action.match(/node "\$GITHUB_ACTION_PATH\/dist\/index\.js" "\$\{taskbound_args\[@\]\}"/g) ?? [];
+
   assert.match(action, /name: TaskBound/);
   assert.match(action, /task:/);
   assert.match(action, /required: false/);
@@ -21,6 +23,10 @@ test('action.yml can derive task scope from pull request event context', async (
   assert.match(action, /--scope-llm/);
   assert.match(action, /npm ci --ignore-scripts/);
   assert.match(action, /scope-match-count/);
+  assert.equal(reviewInvocations.length, 1);
+  assert.match(action, /--format github/);
+  assert.match(action, /--markdown-output "\$report_file"/);
+  assert.match(action, /--json-output "\$json_file"/);
 });
 
 test('self-dogfood workflow uses trusted action ref with pull request event task fallback', async () => {