# tackline

> A tackline is the short length of line on a signal halyard that separates the flags. This tool
> hangs signals on lines of code for an agent to read.

tackline is a terminal app (with a [web version](guides/web.md)) for steering coding agents. You
browse your files or your git diff, select the code you want changed, and write an instruction
right on it. Those notes collect in a session, and the session compiles into one Markdown prompt.

The prompt is plain Markdown, so it works with **Claude Code, Codex, opencode, aider, Cursor**, or
anything else that takes a prompt: paste it, or hand it over from the shell
([how](workflow.md#hand-it-to-your-agent)).

::linkbutton[Get started]{href="getting-started.md"}
::linkbutton[crates.io]{href="https://crates.io/crates/tackline" variant="secondary"}
::linkbutton[GitHub]{href="https://github.com/terminalkitten/tackline" variant="secondary"}

::image[tackline in ten seconds: select code, add a note, review the session, export the prompt]{src="img/demo.gif"}

## Why it exists

Telling an agent *where* to work is the slow part of a prompt. "In `matcher.rs`, the loop around
line 3, no, the one inside `matches`…" costs time and still goes wrong. With tackline you point at
the code itself:

- **Precise.** Every instruction carries its file, line span and the code it's about, so the agent
  doesn't have to guess.
- **Batched.** Collect a dozen small instructions while you read the code, then send them as one
  ordered prompt instead of a dozen chat messages.
- **Durable.** Notes follow the code when the file changes, and are saved as you go. Close the
  app, come back tomorrow, the session is still there.
- **Reviewed before it's sent.** The Session view shows every note with its code in prompt
  order, so you can reorder, edit or drop notes before the agent sees them.

:::note[Steering, not code review]
Notes are instructions and context for an agent ("make this async, keep the signature"), not
verdicts on the code. There's no approve/reject and nothing is posted anywhere: the output is a
prompt.
:::

## How it works

:::steps
1. **Select code** in the Files or Diff view: a line, a block or a few characters.
2. **Press :kbd[c]** and write the instruction. It's saved into the active session.
3. **Press :kbd[3]** to review the session, then **:kbd[y]** to copy the compiled prompt and paste
   it into your agent, or hand it over from the shell.
:::

::image[The Files view: noted code tinted yellow, the note under the cursor in the bottom border]{src="img/files.svg"}

::::cards
:::card[Getting started]{href="getting-started.md"}
Install it and make your first note in two minutes.
:::

:::card[Workflow with your agent]{href="workflow.md"}
From notes to a prompt the agent can act on.
:::

:::card[Notes]{href="guides/notes.md"}
Select, write, edit, move and delete notes.
:::

:::card[Keys]{href="reference/keys.md"}
Every key on one page.
:::
::::