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devolutions (@devolutions) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Vdbe Opcode Port by devolutions — Agent Skill

Name: Vdbe Opcode Port
Author: devolutions

Vdbe Opcode Port

How to port or align a VDBE opcode between Turso's Rust `Insn` and Ahtola's C# `VdbeOpcode`, preserving semantics. Use this when implementing, fixing, or reviewing an opcode in the execution engine or the program builder.

devolutions 4bbfaf6 3.0 KB Updated Sep 17, 2026

File contents

VDBE opcode porting

The execution engine runs a VDBE-style bytecode program (Turso calls these Insn; Ahtola calls them VdbeOpcode). Programs are built by the Compilation layer and executed by the Execution layer. Opcode semantics must match Turso/SQLite exactly — the conformance corpus checks the observable behavior, and the on-disk/transactional invariants depend on it.

Where things live

Concern	Ahtola (C#)	Turso (Rust)
Opcode enum	`src/Ahtola.Core/Execution/VdbeProgram.cs` → `enum VdbeOpcode`	`turso-src/core/vdbe/insn.rs` → `pub enum Insn`
Execution loop	`src/Ahtola.Core/Execution/` (`VdbeProgram.cs`, `VdbeArithmetic.cs`, `VdbeTransaction.cs`, `VdbeParameterBinding.cs`)	`turso-src/core/vdbe/execute.rs`
Program builder	`src/Ahtola.Core/Compilation/` (`*ProgramBuilder.cs`, `DmlStatementCompiler.cs`, `SelectStatementCompiler.cs`)	`turso-src/core/vdbe/builder.rs`
Explain	`src/Ahtola.Core/Execution/VdbeExplain.cs`	`turso-src/core/vdbe/explain.rs`
Sorter / rowset / hash table	`Execution/` + `Compilation/BufferedWindowProgramBuilder.cs`	`turso-src/core/vdbe/sorter.rs`, `rowset.rs`, `hash_table.rs`, `bloom_filter.rs`

Porting an opcode

Find the Rust Insn in turso-src/core/vdbe/insn.rs and its execute arm in execute.rs. Read the full arm — including the ?/error paths and any Label/jump resolution.
Find or add the C# VdbeOpcode in VdbeProgram.cs. The integer values are stable (consumed by the builder and serialized in explain output) — do not renumber existing opcodes; append new ones.
Mirror the semantics, not the call style: register/cursor/sorter indices map to Ahtola's Register/Cursor/Sorter/Accumulator record structs. Preserve operand order, jump-target resolution, and the exact error conditions. Replace Rust IOResult/yield with async/sync managed flow (see the async-io-port skill).
Wire the builder: if the opcode is emitted by a program builder, mirror the builder side in Compilation/ so the compiler emits it in the same situations Turso does.
Exercise it: add or find a conformance case that hits the opcode, run it through Invoke-ManagedTestSuite.ps1 -Filter ... -MinimumExecutedTests 1, then the full conformance lane.

Do not

Do not invent opcodes that have no upstream counterpart without a strong reason and a doc comment explaining why. If you must, mark it clearly as an Ahtola extension in VdbeExplain output.
Do not change an opcode's observable behavior to "simplify" it. If Turso raises an error at step N, Ahtola must raise the same error at the same step.
Do not break explain output: the opcode names/values are part of the debugging contract.

---name: vdbe-opcode-portdescription: How to port or align a VDBE opcode between Turso's Rust `Insn` and Ahtola's C# `VdbeOpcode`, preserving semantics. Use this when implementing, fixing, or reviewing an opcode in the execution engine or the program builder.---# VDBE opcode portingThe execution engine runs a VDBE-style bytecode program (Turso calls these`Insn`; Ahtola calls them `VdbeOpcode`). Programs are built by theCompilation layer and executed by the Execution layer. **Opcode semanticsmust match Turso/SQLite exactly** — the conformance corpus checks theobservable behavior, and the on-disk/transactional invariants depend on it.## Where things live| Concern | Ahtola (C#) | Turso (Rust) || --- | --- | --- || Opcode enum | `src/Ahtola.Core/Execution/VdbeProgram.cs` → `enum VdbeOpcode` | `turso-src/core/vdbe/insn.rs` → `pub enum Insn` || Execution loop | `src/Ahtola.Core/Execution/` (`VdbeProgram.cs`, `VdbeArithmetic.cs`, `VdbeTransaction.cs`, `VdbeParameterBinding.cs`) | `turso-src/core/vdbe/execute.rs` || Program builder | `src/Ahtola.Core/Compilation/` (`*ProgramBuilder.cs`, `DmlStatementCompiler.cs`, `SelectStatementCompiler.cs`) | `turso-src/core/vdbe/builder.rs` || Explain | `src/Ahtola.Core/Execution/VdbeExplain.cs` | `turso-src/core/vdbe/explain.rs` || Sorter / rowset / hash table | `Execution/` + `Compilation/BufferedWindowProgramBuilder.cs` | `turso-src/core/vdbe/sorter.rs`, `rowset.rs`, `hash_table.rs`, `bloom_filter.rs` |## Porting an opcode1. **Find the Rust `Insn`** in `turso-src/core/vdbe/insn.rs` and its execute arm in `execute.rs`. Read the full arm — including the `?`/error paths and any `Label`/`jump` resolution.2. **Find or add the C# `VdbeOpcode`** in `VdbeProgram.cs`. The integer values are stable (consumed by the builder and serialized in explain output) — do **not** renumber existing opcodes; append new ones.3. **Mirror the semantics**, not the call style: register/cursor/sorter indices map to Ahtola's `Register`/`Cursor`/`Sorter`/`Accumulator` record structs. Preserve operand order, jump-target resolution, and the exact error conditions. Replace Rust `IOResult`/yield with `async`/sync managed flow (see the `async-io-port` skill).4. **Wire the builder**: if the opcode is emitted by a program builder, mirror the builder side in `Compilation/` so the compiler emits it in the same situations Turso does.5. **Exercise it**: add or find a conformance case that hits the opcode, run it through `Invoke-ManagedTestSuite.ps1 -Filter ... -MinimumExecutedTests 1`, then the full conformance lane.## Do not- Do not invent opcodes that have no upstream counterpart without a strong reason and a doc comment explaining why. If you must, mark it clearly as an Ahtola extension in `VdbeExplain` output.- Do not change an opcode's observable behavior to "simplify" it. If Turso raises an error at step N, Ahtola must raise the same error at the same step.- Do not break explain output: the opcode names/values are part of the debugging contract.

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