Handling Midnight SDK Breaking Changes: A Developer's Survival Guide

[Sascha]

Every developer building on early-stage blockchain SDKs has lived through this: you run npm install after a team member updates the lockfile, and suddenly nothing compiles. Midnight's SDK is actively evolving, and breaking changes are frequent enough that you need a systematic approach to handling them.

This guide covers practical strategies for managing Midnight SDK upgrades — from detecting breaking changes before they break production, to a step-by-step migration workflow, to maintaining backward compatibility when you can't upgrade immediately.

---

Why Midnight SDK Changes Break More Than Normal Libraries​

Midnight SDK upgrades are more disruptive than typical library updates for a structural reason: proving keys are cryptographically bound to specific circuit versions.

When you upgrade the SDK, even a minor version bump can:

1. Change the circuit constraint system
2. Invalidate your existing proving keys
3. Require regeneration of proving and verification keys
4. Break existing proofs generated against the old keys

Unlike a typical API change where you update a function call, a circuit change means any proofs generated before the upgrade are incompatible with contracts deployed after it.

This creates a hard migration surface on two dimensions:

• Your development environment: compilation and proof generation
• Your deployment state: on-chain contracts vs. client-generated proofs

---

Step 1: Track Changes Before Upgrading​

Never upgrade blindly. Before changing any @midnight-ntwrk/* version:

Check the changelog:

# In your repo, view the current versions
cat package.json | grep "@midnight-ntwrk"

# On npm, check what changed between versions
npx npm-check-updates --filter "@midnight-ntwrk/*" --dry-run

Read the release notes directly:

The Midnight SDK publishes changelogs at: https://github.com/midnight-ntwrk/midnight-js/releases

Look specifically for entries labeled:

• BREAKING CHANGE — requires code changes
• Circuit change — requires key regeneration
• API rename — function/interface names changed
• Type change — TypeScript types modified (common source of silent breakage)

Check the migration guide:
If a migration guide exists, read it in full before starting. The 15 minutes of reading saves hours of debugging.

---

Step 2: Pin Exact Versions (Never Use ^ or ~)​

// DANGEROUS — floating versions
{
  "dependencies": {
    "@midnight-ntwrk/compact-runtime": "^0.14.0",
    "@midnight-ntwrk/midnight-js-types": "~0.14.0"
  }
}

// CORRECT — pinned exact versions
{
  "dependencies": {
    "@midnight-ntwrk/compact-runtime": "0.14.0",
    "@midnight-ntwrk/midnight-js-types": "0.14.0",
    "@midnight-ntwrk/midnight-js-contracts": "0.14.0",
    "@midnight-ntwrk/midnight-js-network-id": "0.14.0"
  }
}

Lockfile discipline:
Commit package-lock.json (or yarn.lock). Never .gitignore it. Your CI should install with npm ci (not npm install) to use the exact lockfile versions.

---

Step 3: Upgrade in an Isolated Branch​

Never upgrade the Midnight SDK directly on main. Create an upgrade branch:

git checkout -b upgrade/midnight-sdk-0.15.0

This lets you:

• Run the full migration without disrupting other work
• Revert cleanly if something breaks badly
• Get a code review of the upgrade diff before merging

---

Step 4: Update Versions and Recompile Contracts​

Update package.json manually (don't use npm update with floating versions):

# Update to specific new version
npm install @midnight-ntwrk/compact-runtime@0.15.0 \
  @midnight-ntwrk/midnight-js-types@0.15.0 \
  @midnight-ntwrk/midnight-js-contracts@0.15.0 \
  --save-exact

Then recompile all Compact contracts:

# Recompile all .compact files
find ./contracts -name "*.compact" | while read contract; do
  echo "Compiling: $contract"
  npx compactc "$contract" -o "$(dirname "$contract")/build"
done

If compilation fails, the error messages from compactc are usually clear about what changed. Common patterns:

Error: 'disclose' function signature changed in 0.15.0
# Fix: Update all disclose() calls to new signature

Error: Type 'Uint64' is no longer assignable to 'Field'
# Fix: Use explicit conversion via toField()

---

Step 5: Regenerate Proving Keys​

After any compilation success, regenerate proving and verification keys. Even if the circuit didn't visibly change, don't trust old keys.

# Script to regenerate all keys
#!/bin/bash
set -euo pipefail

CONTRACTS_DIR="./contracts"
KEYS_DIR="./keys"

mkdir -p "$KEYS_DIR"

for contract_dir in "$CONTRACTS_DIR"/*/build; do
  contract_name=$(basename "$(dirname "$contract_dir")")

  echo "Generating keys for: $contract_name"

  npx compact-cli keygen \
    --circuit "$contract_dir/circuit.json" \
    --proving-key "$KEYS_DIR/${contract_name}.pk" \
    --verification-key "$KEYS_DIR/${contract_name}.vk"

  echo "✅ Keys generated for $contract_name"
done

echo "All keys regenerated. Commit the new keys."

Important: Proving keys must be committed to your repository. They're large (often 50-200MB), so use Git LFS if needed:

git lfs track "*.pk"
git lfs track "*.vk"
echo "*.pk filter=lfs diff=lfs merge=lfs -text" >> .gitattributes
echo "*.vk filter=lfs diff=lfs merge=lfs -text" >> .gitattributes
git add .gitattributes
git lfs install

---

Step 6: Update the Witness Implementation​

After recompiling, review your TypeScript witness implementations. These are the most failure-prone area because TypeScript doesn't always catch circuit-level mismatches at compile time.

What to look for:

// Old pattern (pre-0.15.0)
import { buildTransferWitness } from '@midnight-ntwrk/compact-runtime';

// New pattern (post-0.15.0) — function renamed
import { createTransferWitness } from '@midnight-ntwrk/compact-runtime';

Run the TypeScript compiler as a first check:

npx tsc --noEmit 2>&1 | head -50

TypeScript errors reveal API changes. Fix all TypeScript errors before running tests.

---

Step 7: Run the Full Test Suite​

After compilation and TypeScript checks pass, run your tests:

npm test

Common test failure modes after upgrades:

1. 
   Constraint violations in tests: If tests fail with "constraint not satisfied," the witness implementation doesn't match the new circuit. Compare the old and new circuit constraint counts.
   
   
2. 
   Proof verification failures: Old proofs in test fixtures are invalid. Regenerate test fixtures.
   
   
3. 
   Timeout failures: A new proving system may be slower. Increase test timeouts:
   

   // In jest.config.ts
   export default {
     testTimeout: 120000, // 2 minutes for proof generation
   };

1. Network interaction failures: If the SDK changed how it connects to the network, update your test setup.

---

Step 8: Test on Local Devnet, Then Testnet​

After local tests pass:

1. Deploy to local devnet (if Midnight provides one)
2. Run integration tests against the devnet
3. Deploy to testnet
4. Run smoke tests on testnet before committing to the upgrade

If you have existing testnet deployments, understand that you may need to redeploy contracts if the circuit changed. Old contracts with new client code will produce proof verification failures.

---

Handling "I Can't Upgrade Right Now" Situations​

Sometimes you learn about a breaking SDK change but you can't migrate immediately (active user base, other ongoing work, etc.).

Strategy 1: Lock the environment completely

Prevent accidental upgrades at the system level:

# .npmrc — add to repo root
package-lock=true
engine-strict=true

# package.json engines field
"engines": {
  "node": ">=18.0.0 <20.0.0"
}

Strategy 2: Document the freeze with a clear exit criteria

Create UPGRADE_BLOCKED.md in the repo:

# Midnight SDK Upgrade Blocked

Current version: 0.14.0
Target version: 0.15.0
Blocked since: 2026-01-15
Blocker: Active testnet deployment with 200+ users
Exit criteria: Testnet migration window scheduled for 2026-02-01
Owner: @yourname

## What breaks in 0.15.0
- [List specific breaking changes]
- [Associated code areas]

## Migration plan
[Brief migration plan when the window opens]

Strategy 3: Run parallel environments

For longer freezes, maintain two deployment environments with different SDK versions. Route traffic based on contract version detected from on-chain state.

---

Diagnosing Proof Generation Failures After Upgrade​

If proof generation fails after a successful upgrade, here's the diagnostic checklist:

1. Check proving key freshness

# Get the modification time of the compiled circuit
stat contracts/my-contract/build/circuit.json

# Compare with proving key
stat keys/my-contract.pk

# If circuit is newer than key: regenerate the key

2. Verify circuit input types

# Inspect the circuit's public inputs
cat contracts/my-contract/build/circuit.json | python3 -c "
import json, sys
circuit = json.load(sys.stdin)
print('Public inputs:')
for name, type_info in circuit.get('public_inputs', {}).items():
    print(f'  {name}: {type_info}')
print('Private inputs:')
for name, type_info in circuit.get('private_inputs', {}).items():
    print(f'  {name}: {type_info}')
"

Compare against your witness implementation and verify the types match exactly.

3. Test with minimal inputs

Isolate the failing constraint with a minimal test:

it('should prove minimal transfer', async () => {
  const proof = await proveTransfer({
    from: testKey,
    to: testAddress,
    amount: 1n,           // minimum amount
    balance: 1n,          // exactly equal to amount
  });
  expect(proof).toBeDefined();
});

4. Enable verbose proving output

COMPACT_PROOF_VERBOSE=1 npm test 2>&1 | grep -E "constraint|witness|error"

---

Automating Upgrade Detection​

Set up a CI job to detect new SDK versions:

# .github/workflows/check-sdk-updates.yml
name: Check Midnight SDK Updates
on:
  schedule:
    - cron: '0 9 * * 1'  # Every Monday 9AM

jobs:
  check-updates:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
      - name: Check for SDK updates
        run: |
          npm install -g npm-check-updates
          UPDATES=$(ncu --filter "@midnight-ntwrk/*" --jsonUpgraded 2>/dev/null || echo "{}")
          if [ "$UPDATES" != "{}" ] && [ "$UPDATES" != "null" ]; then
            echo "New SDK versions available:"
            echo $UPDATES
            # Optionally create a GitHub issue or send a notification
          fi

---

Midnight SDK migrations are painful the first time but routine once you have the workflow down. The key principles:

1. Never upgrade without reading the changelog
2. Always regenerate proving keys after any SDK change
3. Test witness implementations explicitly — TypeScript won't catch circuit mismatches
4. Branch, test, review before merging

The SDK will stabilize as Midnight matures, but for the next 12-18 months, treat every @midnight-ntwrk/* version bump as a potential major event.

Источник: Handling Midnight SDK Breaking Changes: A Developer's Survival Guide https://dev.to/tosh2308/handling-midnight-sdk-breaking-changes-a-developers-survival-guide-56kb