zed-industries/zed · error

could not locate suffix lines

Error message

could not locate suffix lines

What it means

The suffix context lines echoed by the model could not be located at a line boundary in the original text after the prefix, so the replacement end offset is unknown. The model's suffix context drifted from the actual buffer content.

Source

Thrown at crates/zeta_prompt/src/zeta_prompt.rs:4412

        let (new_text, suffix_context) = rest
            .split_once("<|fim_suffix|>\n")
            .or_else(|| rest.split_once("<|fim_suffix|>"))
            .unwrap_or((rest, ""));

        let suffix_context = if prefix_context.is_empty() && !suffix_context.is_empty() {
            suffix_context.strip_prefix('\n').unwrap_or(suffix_context)
        } else {
            suffix_context
        };

        let prefix_offset = find_substring_at_line_boundary(context, prefix_context)
            .ok_or_else(|| anyhow!("could not locate prefix lines"))?
            + prefix_context.len();
        let suffix_offset = if suffix_context.is_empty() {
            context.len()
        } else {
            find_substring_at_line_boundary(&context[prefix_offset..], suffix_context)
                .ok_or_else(|| anyhow!("could not locate suffix lines"))?
                + prefix_offset
        };

        let edit_range = prefix_offset..suffix_offset;
        return Ok((edit_range, new_text.to_string()));
    }

    fn find_substring_at_line_boundary(haystack: &str, needle: &str) -> Option<usize> {
        if needle.is_empty() {
            return Some(0);
        }

        haystack.match_indices(needle).find_map(|(offset, _)| {
            let matched_line_start = offset == 0 || haystack[..offset].ends_with('\n');
            matched_line_start.then_some(offset)
        })
    }

View on GitHub (pinned to f4178619ac)

Solutions

1. Retry the request for a verbatim suffix context
2. Use fuzzy or whitespace-insensitive suffix matching as a fallback
3. Reject the edit when suffix context cannot be trusted

When it happens

Trigger: Thrown at crates/zeta_prompt/src/zeta_prompt.rs:4412 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of zed-industries/zed@f4178619ac (2026-08-20). Data as JSON: /api/errors/c6afea4bef2c7220. Report an issue: GitHub.