Compaction coverage floor

Error message

Compaction coverage floor: {label} was dropped; history was not replaced.

What it means

`require_text_survives` is a targeted survival check for a specific labeled text needle (summary snippet, key content). It searches the replacement history for a message whose Text or ToolResult content contains the needle; if nothing keeps it, the rewrite is rejected. Used by `validate_survival_contract` and the duplicate-summary test.

Solutions

Keep the message containing the labeled text in the replacement history.
If the label/needle is stale (test drift), update the needle to match the current anchor content.
Check that rewrite does not drop Text blocks inside ToolResult content.
Run `second_compact_does_not_duplicate_prior_summaries` / `validate_survival_contract` tests to locate the anchor.

Example fix

// before: replacement drops the anchored message
let replacement = summarized_only;
// after: retain the anchor message
let replacement = [summarized_only, anchor_msgs.as_slice()].concat();

Defensive patterns

Strategy: validation

Validate before calling

fn keeps_needle(replacement: &[Message], needle: &str) -> bool {
    replacement.iter().any(|m| m.blocks.iter().any(|b| match b {
        ContentBlock::Text { text, .. } => text.contains(needle),
        ContentBlock::ToolResult { content, .. } => content.contains(needle),
        _ => false,
    }))
}

Try / catch

match compaction::apply_replacement(&replacement) {
    Err(e) if e.to_string().contains("was dropped") => keep_original_history(),
    other => other,
}

Prevention

Identify anchor texts (prior receipts, key snippets) and never drop their messages
Update labeled needles when anchor content legitimately changes
Search both Text and ToolResult content in checks
Run validate_survival_contract before swapping history

When it happens

Trigger: `require_text_survives(original, replacement, label, needle)` runs and no block in the replacement (Text content or ToolResult content) contains the needle substring.

Common situations: A rewrite drops the message containing the labeled anchor (e.g. prior compaction receipt text or a required snippet); a test fixture expects an anchor that the new rewrite no longer preserves.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of Hmbown/CodeWhale@73e0f67d83 (2026-09-22). Data as JSON: /api/errors/3f1113ae960381da. Report an issue: GitHub.

Appendix: source

Thrown at crates/tui/src/compaction/last_round.rs:439

pub(crate) fn require_text_survives(
    replacement: &[Message],
    needle: &str,
    label: &str,
) -> Result<()> {
    let needle = needle.trim();
    if needle.is_empty() {
        return Ok(());
    }
    let kept = replacement.iter().any(|message| {
        message.content.iter().any(|block| match block {
            ContentBlock::Text { text, .. } => text.contains(needle),
            ContentBlock::ToolResult { content, .. } => content.contains(needle),
            _ => false,
        })
    });
    if !kept {
        anyhow::bail!("Compaction coverage floor: {label} was dropped; history was not replaced.");
    }
    Ok(())
}

pub(crate) fn validate_survival_contract(
    original: &[Message],
    replacement: &[Message],
    anchors: Option<&str>,
) -> Result<()> {
    validate_last_round_coverage(original, replacement)?;
    let checkpoints = replacement
        .iter()
        .filter(|message| is_compaction_checkpoint_message(message))
        .count();
    if checkpoints == 0 {
        anyhow::bail!(
            "Compaction coverage floor: checkpoint receipt was dropped; history was not replaced."
        );

View on GitHub (pinned to 73e0f67d83)