Arcium Program Development

Use this skill to implement and debug Arcium computations end-to-end with strict contracts across Arcis circuits, Anchor program wiring, callback verification, and client/test encryption flow.

Decision Tree (Task Classification)

Classify the request before editing code:

1. Stateless computation (e.g., Coinflip)

• No persistent encrypted state account update.
• Usually one encrypted input and one revealed/encrypted output.
• Read first: references/implementation-playbook.md, references/callback-output-shapes.md.

2. Stateful encrypted account flow (e.g., Voting, Sealed Bid, Blackjack)

• Requires .account(pubkey, offset, len) with exact byte layout.
• Usually callback writes ciphertext + nonce to account state.
• Read first: references/account-layout-offsets.md, references/implementation-playbook.md.

3. Permission-gated flow (e.g., Encrypted DNA matching)

• Constraints and status transitions determine whether queueing is allowed.
• Read first: references/permission-and-state-machines.md, references/examples-patterns.md.

4. Offchain circuit source flow

• init_comp_def uses CircuitSource::OffChain and circuit_hash!.
• Read first: references/docs-and-migrations.md, references/troubleshooting-matrix.md.

5. Migration or compatibility update

• Update Rust/TypeScript dependencies and API call signatures first.
• Read first: references/docs-and-migrations.md, references/anti-patterns.md.

6. Debugging request

• Triaged by stage: encryption -> queue -> callback verify -> finalization.
• Read first: references/troubleshooting-matrix.md, references/test-client-patterns.md.

Mandatory Build Contract

Keep these invariants aligned in every implementation:

1. Circuit function name (#[instruction]) must match comp_def_offset("...") identifier.
2. Program callback macro must match instruction name:

• #[arcium_callback(encrypted_ix = "<ix_name>")]

3. Callback output type must match generated type:

• SignedComputationOutputs<<IxName>Output>

4. Queue and callback contexts must reference the same comp-def account and cluster derivation.
5. Every callback must call verify_output(&cluster_account, &computation_account) before consuming output.
6. init_*_comp_def must exist for every queued encrypted instruction.

ArgBuilder Contract (Strict Ordering)

Enc<Shared, T> input contract

Order is strict and must be preserved:

1. x25519_pubkey(<client_pubkey>)
2. plaintext_u128(<nonce>)
3. encrypted fields in exact circuit argument order (encrypted_u8/u16/u32/u64/u128/bool/...)

Enc<Mxe, T> input contract

Order is strict and must be preserved:

1. plaintext_u128(<mxe_nonce>)
2. encrypted fields in exact circuit argument order

Account-backed encrypted state contract

Use:

• .account(<state_account>, <byte_offset>, <byte_len>)

Rules:

1. Offset must start after Anchor discriminator (8) plus preceding fixed fields.
2. Length must match ciphertext field count times 32 bytes (or packed struct contract).
3. Add inline comments documenting offset derivation.

See detailed formulas and examples in references/account-layout-offsets.md.

Callback Output Parsing Contract

Two common shapes are generated:

1. Simple shape

Ok(MyIxOutput { field_0 }) => field_0

Used for single output structs/values.

2. Nested shape

Ok(MyIxOutput {
    field_0: MyIxOutputStruct0 {
        field_0: a,
        field_1: b,
        field_2: c,
    },
}) => (a, b, c)

Used when return type is a tuple or multi-field struct.

Mandatory checks:

1. Verify output before parsing.
2. Check ciphertext cardinality when business logic expects exact count.
3. Persist/emit only after successful verification and shape checks.

See references/callback-output-shapes.md.

Account Offset Contract

Use this formula for encrypted payload start:

offset = 8 (Anchor discriminator) + sum(size of preceding account fields)

Examples:

• Voting counters: 8 + 1 (discriminator + bump)
• Sealed auction encrypted state: 8 + 1 + 32 + 1 + 1 + 8 + 8 + 1 + 16
• DNA markers block: 8 + 32 + 16 + 32

When adding or reordering account fields, recompute offsets immediately.

Failure Triage Tree

1. Encryption stage failure

• Symptoms: decrypt mismatch, invalid nonce usage, unusable ciphertext.
• Check x25519 keypair generation, nonce serialization (deserializeLE), shared secret pairing.
• Reference: references/test-client-patterns.md, references/troubleshooting-matrix.md.

2. Queue stage failure

• Symptoms: account not found, constraint errors, custom program errors.
• Check cluster offset, PDA derivation, comp-def account offset, account ordering, constraint seeds.
• Reference: references/account-layout-offsets.md, references/permission-and-state-machines.md.

3. Callback verify failure

• Symptoms: AbortedComputation, output parse mismatch.
• Check comp-def alignment, callback macro ix name, generated output shape assumptions.
• Reference: references/callback-output-shapes.md.

4. Finalization stage failure

• Symptoms: queue tx confirmed but no resolved result.
• Check awaitComputationFinalization(...) usage, computation offset mismatch, event listener sequencing.
• Reference: references/test-client-patterns.md, references/troubleshooting-matrix.md.

Templates (Scaffolding)

Use templates in assets/templates to start implementations quickly:

• assets/templates/new-computation/arcis-instruction.rs.tpl
• assets/templates/new-computation/program-flow.rs.tpl
• assets/templates/new-computation/callback.rs.tpl
• assets/templates/new-computation/init-comp-def.rs.tpl
• assets/templates/new-computation/e2e-test.ts.tpl
• assets/templates/offchain-circuit/init-comp-def-offchain.rs.tpl
• assets/templates/permissioned-flow/accounts-and-constraints.rs.tpl

Replace placeholders such as <IX_NAME>, <PROGRAM_ID>, <STATE_OFFSET>, <STATE_LEN>.

Task Routing

• End-to-end implementation workflow: Read references/implementation-playbook.md.

• Pattern selection by example: Read references/examples-patterns.md.

• Account layout and offset math: Read references/account-layout-offsets.md.

• Callback output decoding: Read references/callback-output-shapes.md.

• Permissions and state transitions: Read references/permission-and-state-machines.md.

• Test/client orchestration: Read references/test-client-patterns.md.

• Migrations and deployment: Read references/docs-and-migrations.md.

• Failure triage: Read references/troubleshooting-matrix.md.

• What to avoid: Read references/anti-patterns.md.

Definition of Done

Code changes are complete only when all checks pass:

1. Structural/build checks:

arcium build
cargo check --all
arcium test

2. Skill checks:

python3 /Users/grisahudozestvennyj/.codex/skills/.system/skill-creator/scripts/quick_validate.py /Users/grisahudozestvennyj/Documents/projects/arcium/dna/skills/arcium-program-development
rg -n "[\p{Cyrillic}]" /Users/grisahudozestvennyj/Documents/projects/arcium/dna/skills/arcium-program-development || true

3. Functional acceptance checks:

• Circuit name, comp-def offset, callback macro, and callback output type are aligned.
• ArgBuilder order matches circuit input ownership contract.
• Offset constants match actual account layout and are documented.
• Callback verifies output before parsing/persisting.
• Tests wait for computation finalization and validate expected results.

Delivery Standard

• Produce concrete code edits, not abstract guidance.
• Preserve existing seed derivation and PDA conventions unless migration requires changes.
• State assumptions explicitly when required inputs are missing.
• End with executed validation commands and any remaining risk notes.