## 📜 History Editing

If a conversation goes off track, you can surgically edit your conversation history using the interactive history editing mode. This allows you to rewind to a specific point, modify messages, or remove problematic exchanges without starting over.

### Invoking History Editing

Use the `-b` or `--edit-history` flag along with `-F` to specify your chat file:

```bash
./build/drharness -F conversation.json -b
```

*Note: The `-F` flag is required because editing requires an existing chat file.*

### The Rebase Editor Format

When invoked, the harness opens your configured editor with all messages in your conversation listed in order. Each line follows a git rebase-style format:

```
<command> <index> [<role>] <display_content>
```

**Commands:**
- `pick`: Keep the message unchanged
- `edit`: Modify the message content and/or role
- `drop`: Delete the message (or simply remove the line)

**Role:** (optional, only for `edit` commands)
- `[user]`
- `[assistant]`
- `[tool]`

**Display content:** The first line of the message (for reference only)

Lines starting with `#` are comments and are ignored. Empty lines are treated as drops.

### Editing Message Content and Roles

When you mark a message with `edit`, the harness will open your editor again to let you modify the content. The edit prompt shows:
- The previous message as context (for reference)
- The `>8` separator
- The message content you can edit

You can change the role by modifying the role in the rebase line (e.g., `edit 2 [user]`).

### Common Workflows

**Editing a single message:**
```
pick 0 [user] Hello, can you help me?
pick 1 [assistant] Sure! What do you need?
edit 2 [assistant] I misunderstood. Let me try again.
pick 3 [user] That's better, thanks!
```
Then, when editing message 2, you'll be prompted to enter the new content.

**Dropping unwanted messages:**
```
pick 0 [user] Start the project
drop 1 [assistant] Wrong approach
pick 2 [user] Let me try a different way
```
Or simply delete the line:
```
pick 0 [user] Start the project
# pick 1 [assistant] Wrong approach
pick 2 [user] Let me try a different way
```

**Modifying message roles:**
```
pick 0 [user] Write a function
edit 1 [user] I meant write a class instead
```

**Continuing a conversation after editing:**
After saving and exiting the editor, your changes are persisted to the chat file. The program exits, allowing you to inspect the result. To continue the conversation:
```bash
./build/drharness -F conversation.json -m "Continue from where we left off"
```

*Note: The history editor uses strict validation. Any syntax error (invalid command, out-of-range index, invalid role) will cause the editor to abort with an aggregated error message. No partial changes are applied.*