What causes "proposalrun: seq %d recompute: %w" in JuliusBrussee/caveman?

Inspect the wrapped cause (errors.Unwrap / %w chain) and fix or restore the offending row's detail JSON.

proposalrun: seq recompute

Error message

proposalrun: seq %d recompute: %w

What it means

VerifyChain recomputes each row's hash via RowHash; this error wraps a failure from that recomputation (returned with %w, typically from CanonicalDetail failing to canonicalize the stored detail JSON). It means the stored row data itself is unusable for hashing — most often the detail column holds invalid or non-canonicalizable JSON.

Solutions

Inspect the wrapped cause (errors.Unwrap / %w chain) and fix or restore the offending row's detail JSON.
Re-validate detail with json.Valid before rows are written; write only via the library's Append helper.
Restore the affected rows from backup or regenerate them from the original events.
If the wrapped error is an oversized JSON number, re-serialize the detail with bounded numeric precision.

Example fix

// before
Append(action, json.RawMessage(badBytes), cost) // badBytes is not valid JSON
// after
if !json.Valid(badBytes) { return fmt.Errorf("invalid detail") }
Append(action, json.RawMessage(badBytes), cost)

Defensive patterns

Strategy: try-catch

Validate before calling

func detailIsValid(runs []proposalrun.Run) bool {
	for _, r := range runs {
		if !json.Valid(r.Detail) { return false }
	}
	return true
}

Try / catch

if err := proposalrun.VerifyChain(runs); err != nil {
	var inner error
	errors.As(err, &inner) // inspect wrapped recompute cause
	return fmt.Errorf("verify failed: %w", err)
}

Prevention

Check json.Valid(detail) before every append
Restrict detail writes to the library's canonicalization path
Monitor for canonicalization errors in write telemetry

When it happens

Trigger: Calling VerifyChain(runs) where some row's Detail is malformed JSON or otherwise fails CanonicalDetail, causing RowHash to return an error which is wrapped as 'seq %d recompute: %w'.

Common situations: Detail written by non-library code paths with invalid JSON, encoding corrupted by migrations or column type changes, truncated JSON from an oversized payload, invalid JSON numbers as in errors 1510-1515.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

AI-assisted analysis of JuliusBrussee/caveman@3ee70a1026 (2026-09-20). Data as JSON: /api/errors/bb782f2b337b3330. Report an issue: GitHub.

Appendix: source

Thrown at shared/platform/proposalrun/proposalrun.go:361

	if len(runs) == 0 {
		return nil
	}
	sorted := make([]Run, len(runs))
	copy(sorted, runs)
	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Seq < sorted[j].Seq })

	prevHash := ""
	for i, r := range sorted {
		wantSeq := int64(i + 1)
		if r.Seq != wantSeq {
			return fmt.Errorf("proposalrun: seq %d out of order (expected %d)", r.Seq, wantSeq)
		}
		if r.PrevHash != prevHash {
			return fmt.Errorf("proposalrun: seq %d prev_hash does not link to the prior row", r.Seq)
		}
		got, err := RowHash(r.PrevHash, r.Seq, r.Action, r.Detail, r.CostUSD, r.CreatedAt)
		if err != nil {
			return fmt.Errorf("proposalrun: seq %d recompute: %w", r.Seq, err)
		}
		if got != r.RowHash {
			return fmt.Errorf("proposalrun: seq %d row_hash mismatch (tampered)", r.Seq)
		}
		prevHash = r.RowHash
	}
	return nil
}

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