diff --git a/bounty-notes/issue-83-external-bounty-flow.md b/bounty-notes/issue-83-external-bounty-flow.md
new file mode 100644
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+++ b/bounty-notes/issue-83-external-bounty-flow.md
@@ -0,0 +1,38 @@
+# External bounty flow verification for issue #83
+
+Fixes #83.
+
+Issue #83 covers an externally-created bounty where the repository app was not installed at issue creation time. This contribution adds a deterministic fixture and validator for that path so the pending-approval and approved bounty states can be checked without depending on a live CodeBounty environment.
+
+## What is covered
+
+- Repository: `CodeBountyOrg/BountyTestRepository`
+- Issue: `#83`
+- Source: external sponsor
+- No-app-installed path: `installation.app_installed === false`
+- Pending state: `pending_maintainer_approval`
+- Available state: `available`
+- Required PR syntax: `fixes #83`
+- Visible bounty amount: `$150 USD`
+
+## Validation commands
+
+```bash
+node --check scripts/validate-codebounty-external-bounty.mjs
+node scripts/validate-codebounty-external-bounty.mjs test-fixtures/codebounty-external-issue-83.json
+python3 - <<'PY'
+import json
+from pathlib import Path
+fixture = json.loads(Path('test-fixtures/codebounty-external-issue-83.json').read_text())
+note = Path('bounty-notes/issue-83-external-bounty-flow.md').read_text()
+assert fixture['issue']['number'] == 83
+assert fixture['installation']['app_installed'] is False
+assert fixture['bounty']['amount_usd'] == 150
+assert 'fixes #83' in note.lower()
+PY
+git diff --check
+```
+
+## Payout note
+
+The GitHub-visible bounty is treated as submitted-visible only. CodeBounty platform application and maintainer acceptance remain payout blockers until verified.
diff --git a/scripts/validate-codebounty-external-bounty.mjs b/scripts/validate-codebounty-external-bounty.mjs
new file mode 100644
index 0000000..255a5a3
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+++ b/scripts/validate-codebounty-external-bounty.mjs
@@ -0,0 +1,48 @@
+#!/usr/bin/env node
+import { readFileSync } from 'node:fs';
+
+const assert = (condition, message) => {
+  if (!condition) {
+    throw new Error(message);
+  }
+};
+
+const loadPayload = (path) => {
+  try {
+    return JSON.parse(readFileSync(path, 'utf8'));
+  } catch (error) {
+    throw new Error(`Unable to read external bounty fixture at ${path}: ${error.message}`);
+  }
+};
+
+const payloadPath = process.argv[2] ?? 'test-fixtures/codebounty-external-issue-83.json';
+const payload = loadPayload(payloadPath);
+
+assert(payload.repository?.full_name === 'CodeBountyOrg/BountyTestRepository', 'repository.full_name must match the target repository');
+assert(payload.issue?.number === 83, 'issue.number must be 83');
+assert(payload.issue?.source === 'external_sponsor', 'issue.source must identify an external sponsor');
+assert(payload.installation?.app_installed === false, 'fixture must cover the no-app-installed path');
+assert(payload.bounty?.amount_usd === 150, 'bounty.amount_usd must stay at the announced $150');
+assert(payload.bounty?.currency === 'USD', 'bounty currency must be USD');
+assert(Array.isArray(payload.timeline) && payload.timeline.length >= 2, 'timeline must include pending and available states');
+
+const states = payload.timeline.map((event) => event.status);
+assert(states[0] === 'pending_maintainer_approval', 'first timeline state must be pending maintainer approval');
+assert(states.includes('available'), 'timeline must include the available state after approval');
+
+const pending = payload.timeline.find((event) => event.status === 'pending_maintainer_approval');
+const available = payload.timeline.find((event) => event.status === 'available');
+assert(pending?.requires_maintainer_action === true, 'pending state must require maintainer action');
+assert(available?.requires_maintainer_action === false, 'available state must no longer require maintainer action');
+assert(available?.required_pr_syntax === 'fixes #83', 'available state must preserve required PR syntax');
+
+const normalized = {
+  issue: payload.issue.number,
+  amount_usd: payload.bounty.amount_usd,
+  external_sponsor: payload.issue.source === 'external_sponsor',
+  no_app_installed_path: payload.installation.app_installed === false,
+  final_status: available.status,
+  required_pr_syntax: available.required_pr_syntax,
+};
+
+console.log(JSON.stringify(normalized, null, 2));
diff --git a/test-fixtures/codebounty-external-issue-83.json b/test-fixtures/codebounty-external-issue-83.json
new file mode 100644
index 0000000..b19a424
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+++ b/test-fixtures/codebounty-external-issue-83.json
@@ -0,0 +1,33 @@
+{
+  "event": "external_bounty.created",
+  "repository": {
+    "full_name": "CodeBountyOrg/BountyTestRepository"
+  },
+  "issue": {
+    "number": 83,
+    "title": "Creating issue as an external user without App Installed",
+    "source": "external_sponsor"
+  },
+  "installation": {
+    "app_installed": false,
+    "expected_path": "maintainer_approval_required"
+  },
+  "bounty": {
+    "amount_usd": 150,
+    "currency": "USD",
+    "provider": "CodeBounty"
+  },
+  "timeline": [
+    {
+      "status": "pending_maintainer_approval",
+      "requires_maintainer_action": true,
+      "comment_type": "bounty_pending_approval"
+    },
+    {
+      "status": "available",
+      "requires_maintainer_action": false,
+      "comment_type": "bounty_announcement",
+      "required_pr_syntax": "fixes #83"
+    }
+  ]
+}