Logico — Follow the logic, together.

A VS Code extension that points to the one piece of code you should read next.

GitHub Copilot anticipates the code you will write next. Logico anticipates the code you will read next. As you read, Logico infers what you are following and prepares a single next location. Press Ctrl+L to jump there.

When it helps

You inherited a large repository and don't know where to start reading
The real implementation hides behind an interface and is hard to reach
You want to trace where a value is created and where it gets changed
You know what a feature does, but not where it lives in the code
You are about to review a change and want to know where to start

Highlights

Always one candidate. No list to compare. Logico skips the side paths, such as loggers and validation, and picks the code that matters.
One key: Ctrl+L. Press once to jump to the next location. Press twice quickly to search in plain words.
Follows how you read. From your cursor movements, Logico infers whether you are following the control flow, a value, or the overall structure.
Stays out of your way. It never moves your cursor on its own and never edits your code. While you read, there are no pop-ups or panels, only quiet hints in the status bar and at the end of the line.

Getting started

You need VS Code 1.101.0 or later and your own Jev (TypeSafe) API Key.

Search for Wisteria30.logico in the Extensions view and install Logico.
Open the project folder you want to read.
Run Logico: Set Up… from the Command Palette, choose Set Jev API Key, and paste your key. You can get a key at TypeSafe.
In the same list, choose Check the connection to Jev.

That's it. Logico appears on the right of the status bar, and a next location is prepared as you read.

The extension is free. Jev usage is subject to TypeSafe's pricing and rate limits.

Usage

Three actions on one key

Ctrl+L on Windows, Linux, and macOS alike.

Action	What happens
Press Ctrl+L once	Jump to the location shown as `Next ready`
Press Ctrl+L twice quickly	Describe what you want to find, then pick from the top 5
Select text, then press Ctrl+L once	Find places that show what the selected value or text means, then pick from the top 5

Jump to the next location

As you read, Logico infers which of three ways you are reading, collects matching candidates, and picks one.

Reading	What it follows	Examples of the next location
Control Flow	The flow of execution	The function being called, the concrete implementation behind an interface, a function called later on
Data Flow	The flow of a value	Where the value is created, written, or injected, or where it is used
Structure	The overall shape	The core public API of a class or module

When the next location is ready, the status bar shows Next ready, and the end of the line you are reading shows a faint hint of where you will jump. Clicking the hint jumps too.

const intent = await this.gateway.createPaymentIntent(order);  ⇢ StripeGateway.createPaymentIntent (src/gateway.ts:42)

Keep reading where you land, and Logico prepares the next one.

Find a place in plain words

Press Ctrl+L twice quickly to open the input box. You don't need to know function names. Describe the feature or its role, in English or Japanese.

the API entry point that accepts payments
where the configuration file is loaded
the code that updates the search index
the authentication code changed in last month's PRs

The top 5 candidates are listed by likelihood. Press Enter to jump. Your request also becomes your reading goal and guides how later next locations are chosen.

Jump from a selection

Select some text and press Ctrl+L once. Logico looks at functions that receive the value, definitions, where the value comes from or goes, and other occurrences of the same text, and shows the top 5 places that explain what you selected. For example, selecting o-1 in createOrder("o-1") puts the definition createOrder(id: string) first.

Review changes (REVIEW mode)

When you review a change, first skim all of it and decide where to start. REVIEW mode lays out the changes on your branch since it left the default branch, plus uncommitted changes (including new files), in the order to read them. A pull request checked out with the GitHub Pull Requests extension works the same way. The places that deserve the most attention in testing deserve it in review too, so Logico checks each changed file for five traits and puts files with more of them first:

Recent: new code, or code that has been changing lately
Core: the main features the product exists for
Risk: a mistake would hurt users or the code that depends on it (public APIs, schemas, persisted data, authentication, rarely exercised paths)
Problematic: code that has needed bug fixes again and again
Expertise: code that only a few people understand

Core and Risk are judged by Jev from the change itself. Recent, Problematic, and Expertise are computed from the file's git history (recent commits, bug-fix commits, and how concentrated its authorship is), relative to the other files in the same review.

Open a changed file from Source Control. Logico asks whether to start REVIEW mode. You can also run Logico: Start Review, or click Start Review in the Logico Review Order view in Source Control.
The Logico Review Order view lists the changed files in that order, tagged with the traits that apply, with the lines added and removed and the changed declarations. A changelog or release-note entry comes first, tagged Overview, so you see what the change is for before reading the code.
Click a file to open its diff against HEAD. Files you have opened are checked off, and the status bar shows Review 2/9.
To finish, click × in the view or run Logico: End Review. If you have been reading outside the changes for a while, Logico asks whether to end.

Logico only shows the order. It doesn't jump for you or flag "suspicious" code; where to look is up to you.

While reviewing, put the cursor in a change and press Ctrl+L. Besides the usual next location, Logico also considers places outside the change that may need the same fix (an old name or constant left behind, a similarly named function) or that already do what the change does, and Jev picks one when it fits.

What you see

Where	Meaning
Status bar `Logico: Data Flow`	The way Logico thinks you are reading. Data Flow adds `↑` (toward the origin) or `↓` (toward the uses)
Status bar `Next ready: <symbol>`	The next location is ready. Click it to jump
End of the line `⇢ <symbol> (<file:line>)`	Where you will jump
Mark in the gutter	The line of the next location, when it is in the current file
Faint hint after a symbol `: Gateway ⇢ StripeGateway.…`	The type of the symbol you are looking at and the concrete implementation that actually runs
Status bar `Logico index`	The search index is being built. It disappears when ready
Source Control view `Logico Review Order`	The changed files in the order to review them (REVIEW mode)
Status bar `Review 2/9`	REVIEW mode is on: changed files seen / all. Click it to pick a file

Logico computes once when your cursor or scrolling comes to rest. After 5 seconds without activity, or while you are away from the window, it stops computing and sends nothing to Jev.

Languages

Logico works with any language whose language server returns definitions, references, implementations, and symbols. TypeScript and JavaScript work with VS Code's built-in features. For other languages, install the language's extension (Python, Go, Rust, and so on).

The extension's UI follows VS Code's display language: English, or Japanese when VS Code is set to Japanese.

Local embedding model (optional)

Run a local embedding model to make plain-word search more accurate and faster. Code snippets never leave your machine (127.0.0.1). Without it, Logico searches by walking the folders.

In Logico: Set Up…, choose Set up local models.
Point Logico to llama-server from llama.cpp. If it isn't installed, Logico shows how to install it (on macOS: brew install llama.cpp).
After you confirm, Logico downloads the Nemotron-3-Embed-1B embedding model (about 1.2 GB) from Hugging Face, pinned to a revision and verified by SHA-256.
Once it checks that the model works, Logico saves the settings and starts building the search index.

The first build takes time depending on the project size and your machine. Progress appears as Logico index in the status bar. After that, only changed files are updated.

Network and privacy

Logico has no relay server. It talks only to the following:

Destination	What is sent	Why
Jev API (TypeSafe)	Your requests, recent actions, file names, candidate code snippets, and in REVIEW mode the diffs of changed files	Inferring how you read and ranking next locations and search results. Sent directly with your API Key
`llama-server` on `127.0.0.1`	Code snippets	Local embeddings (only if you set them up)
GitHub API	Repository name, PR numbers, versions, workflow file names, branch names	CI results, PR descriptions, and release notes. No code snippets. Uses VS Code's GitHub sign-in
Hugging Face	Nothing	Downloading the local model (only when you set it up)

Use Logico only on projects whose code you are allowed to send to Jev.
Your API Key is stored in the OS keychain through VS Code's SecretStorage, never in settings files.

Jev chooses among candidates that Logico collects. It is not always right, so check the code where you land as you read on.

Settings

Setting	Default	Description
`logico.idleThresholdSeconds`	`5`	Stop computing after this many seconds without activity
`logico.recomputeDebounceMs`	`300`	Wait after activity settles before computing (ms)
`logico.doublePressMs`	`250`	Interval that counts as a double press of Ctrl+L (ms)
`logico.localModel.gpu`	`true`	Run local models on the GPU (Metal on Apple Silicon)
`logico.review.endPromptSeconds`	`120`	In REVIEW mode, ask whether to end after reading outside the changes for this many seconds

Set up local models fills in the local model paths (logico.localModel.llamaServerPath, logico.localModel.embeddingModelPath).

Troubleshooting

Start with Check the connection to Jev in Logico: Set Up… and the Logico channel in the Output panel. Clicking Logico in the status bar opens the list of settings, checks, and logs.

If there is no next location, pressing Ctrl+L tells you why.

Message	Meaning and what to do
Status bar `Logico: Set Up`	The API Key is not set. Click it to set the key
Computing the next location	Waiting for Jev and the language server. It turns into `Next ready` shortly
The cursor is not on a word…	The cursor is on whitespace or a symbol. Put it on an identifier
No candidates were found from “…” here	The language server returned no references, implementations, or declarations. Check that the language's extension is installed and has finished loading
There were N candidates, but Jev judged none of them worth reading	Nothing from here moves your reading forward. Read on a little and press again

Logico: Open Log File opens the log file. Logs contain your requests and code snippets, so review them before sharing.

License

Logico distributed through the Marketplace or as a VSIX may be used for any purpose, including commercial use. Copying, modification, reverse engineering, and redistribution are not permitted. See the bundled LICENSE for details and THIRD_PARTY_NOTICES.txt for notices of bundled third-party libraries.

Logico

Wisteria30