Timeline & rewind

Long conversations get a timeline that you can skim. When a thread takes a wrong turn, you can rewind it to an earlier point and carry on from there. This works in topics and chats, and in agent sessions with a few differences.

One dash per turn. Hover one to preview it, and jump to it or rewind there.

The timeline rail

A conversation with two or more turns shows a column of short dashes on the right edge of the transcript. A turn is one prompt plus everything up to the next prompt: the reply, tool calls, and any compaction marker. Each turn gets one dash.

• Dashes for turns on screen are brighter. The turn you're reading is blue: the last one whose prompt has scrolled past the top. At the bottom, it's the latest turn. The prompt of that turn gets a short blue bar on its right edge, in the same blue, so you can see which message the dash stands for.
• A turn that contains a compaction marker is amber.
• Hover a dash, or move to it with the keyboard, for a preview card. It shows the turn number, the time, and the start of the prompt and of the reply.
• Click a dash to jump to that turn. The rail covers the whole conversation, including older turns not yet loaded: jumping to one loads the history in between first.

The dashes sit at a fixed spacing, centred on the right edge of the transcript. In a very long conversation they get closer together so they all still fit.

Looking at the timeline changes nothing. Only an explicit rewind does.

Rewinding

Rewind is always a two-step action, so you see what will go before anything changes.

1. Pick the point. You can start a rewind from three places:
   • A dash's preview card: Rewind here or Edit & resend.
   • Any prompt's hover toolbar: the history icon for Rewind here, the pencil for Edit & resend. While you're scrolled back, the toolbar of the prompt with the blue bar stays visible without hovering.
   • The Reading turn N of M bar above the composer, shown while you're scrolled back: Rewind to here. That bar also has a Latest button that takes you back to the bottom.
2. Check the preview. A dashed conversation restarts here line marks the cut. The turns after it are greyed out and their dashes turn red. The bar above the composer says how many turns will be deleted. Choose Rewind to go ahead, or Cancel (or press Esc) to back out.

The preview shows exactly what a rewind would delete before you confirm.

There are two ways to rewind:

	Keeps	Deletes	Then
Rewind here	the chosen turn, prompt and reply	every later turn	type the next prompt as usual
Edit & resend	the turns before it	the chosen turn and every later one	its prompt is back in the composer, ready to edit and send

Edit & resend puts only the prompt's text back in the composer. Attach any files again yourself.

Undo

After you confirm, the turns disappear right away. An undo bar counts down for 8 seconds, for example "Rewound · 7 turns removed · undo in 8s". Undo brings the turns back. For Edit & resend, it also restores what was in the composer, unless you've already started editing the prompt.

Once the countdown ends, the turns are deleted for good, along with their attachments, just like deleting a message. Precursor deletes them straight away if you send a new prompt or leave the conversation, so a new turn never ends up inside a cut.

Rewinding past a compaction marker removes the marker too. The model then works from the full history before the cut again.

While a reply is streaming

You can't rewind while a reply is being generated. The buttons are disabled, and the server refuses with 409 so the reply can't land after a cut. Stop the reply or wait for it to finish first.

In agent sessions

An agent's Activity tab has the same rail, preview card, prompt toolbar and Reading turn N of M bar. A turn is one prompt you sent, plus everything the agent did up to your next prompt. The continued autonomously prompts that the goal loop sends stay inside the turn they continue: they don't get dashes of their own.

An agent rewind is previewed like a chat's, but it's final once you confirm.

The conversation an agent works from lives in its Copilot session, not in Precursor's transcript. So a rewind cuts both: the session's history first, so the model no longer sees the dropped turns, then the transcript. That changes a few things:

• No undo. The Copilot session can't bring dropped turns back. The preview says This can't be undone, and the turns are gone as soon as you confirm.
• Only when the agent is at rest. Rewind is unavailable while a turn is running or waiting for an approval. Stop the agent, or let it finish, first.
• Only the current session. A new run usually starts a new Copilot session, for example a fresh start or /clear. So only the turns of the session the agent is in now can be rewound: the current run's, and those of an earlier run that carried on the same session (editing the agent's task restarts it on a new run but keeps the conversation). Turns from other sessions, and turns recorded before rewind existed, stay on the rail for navigation only.
• Not on a workflow step. While the agent's current run is driven by a workflow step, rewind is unavailable: the workflow has already passed that step's output on. Replay the step from the workflow instead.
• Not past a compaction. Once a compaction has folded turns into a summary, the session can't return to them. Precursor says so instead of rewinding.
• The run is reset. The agent rests as idle, with the last kept answer as its summary. Progress, a raised question and the goal loop's step count are cleared, and artifacts the run published from the dropped turns on are deleted.

An agent exchange mirrored into a topic or chat is a separate copy. Rewinding the agent doesn't touch it, and rewinding the topic or chat doesn't touch the agent.

Experimental

Agent rewind uses an experimental Copilot SDK API, which may change.

Restoring files

A rewind can also put back the files the dropped turns changed. When you start one, Precursor asks the agent's Copilot session which files those turns created, edited or deleted, and the confirmation bar offers Also restore N files with the total lines added and removed. Show files lists them. The box is unticked every time: leave it, and only the conversation is rewound.

Restoring files is opt-in for each rewind, and the list shows what would change.

• Files go back to how they were before the first dropped turn.
• A file you changed after the agent did is left alone. After the rewind, a note says how many files were restored and how many were left as they were. Hover it to see which ones, and why.
• File restore happens before the conversation is cut. If it fails, the conversation is left as it was and Precursor says whether every file was put back. If some couldn't be, check the agent's files before you try again.
• It needs a session that tracked its file changes from its first turn. New sessions do, unless you turn off Track file changes for rewind in Settings → Agents. For an older session, or a remote one, the bar says the files will stay as they are.

Runs on the rail

With All runs selected, the rail shows every run's turns. A short gap separates one run from the next, and the preview card names the run, for example Run #12 · Schedule. The runs you can rewind are marked current session.

Keyboard

Press Tab to reach the rail. Then:

Key	Action
↑ / ↓, Home / End	Move between turns. The preview card follows the focus.
Enter	Jump to the turn.
R	Preview Rewind here on the turn.
E	Preview Edit & resend on the turn.
Esc	Close the card, or cancel a preview.

Screen readers hear each dash as "Turn N of M" followed by its prompt. The current turn is announced as the current step, and the preview, removal and undo are announced as status updates.

Over the API

The rail and rewind use two endpoints, available on both topics and chats: GET …/messages/turns and POST …/messages/rewind. Agents use GET /api/agents/{id}/rewind/preview and POST /api/agents/{id}/rewind, and build their turns from the transcript. See the API reference.