feat(ai-builder): Add a binary check to validate node references

[lucamattiazzi]

Summary

This PR adds a binary check that validates that all node references refer to nodes upstream.

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
45954	1	45953	2

View the top 1 failed test(s) by shortest run time

createBinaryChecksEvaluator runs deterministic checks without LLM

Stack Traces | 0.002s run time

Error: expect(received).toBe(expected) // Object.is equality

Expected: 17
Received: 18
    at Object.<anonymous> (.../n8n/n8n/packages/@n8n/ai-workflow-builder..../binary-checks/__tests__/index.test.ts:17:27)
    at processTicksAndRejections (node:internal/process/task_queues:104:5)

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[github-actions]

Performance Comparison

Comparing current → latest master → 14-day baseline

Idle baseline with Instance AI module loaded

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
instance-ai-heap-used-baseline	186.35 MB	186.51 MB	186.46 MB (< 3 samples)	-0.1%	-0.1%	—
instance-ai-rss-baseline	344.25 MB	394.55 MB	369.15 MB (< 3 samples)	-12.7%	-6.7%	—

docker-stats

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
docker-image-size-n8n	1269.76 MB	1269.76 MB	1269.76 MB (σ 0.00)	+0.0%	+0.0%	—
docker-image-size-runners	386.00 MB	386.00 MB	387.50 MB (σ 3.00)	+0.0%	-0.4%	✅

Memory consumption baseline with starter plan resources

Metric	Current	Latest Master	Baseline (avg)	vs Master	vs Baseline	Status
memory-heap-used-baseline	113.91 MB	114.53 MB	113.09 MB (σ 1.15)	-0.5%	+0.7%	✅
memory-rss-baseline	281.51 MB	287.07 MB	281.78 MB (σ 34.50)	-1.9%	-0.1%	✅

How to read this table

• Current: This PR's value (or latest master if PR perf tests haven't run)
• Latest Master: Most recent nightly master measurement
• Baseline: Rolling 14-day average from master
• vs Master: PR impact (current vs latest master)
• vs Baseline: Drift from baseline (current vs rolling avg)
• Status: ✅ within 1σ | ⚠️ 1-2σ | 🔴 >2σ regression