background content is

Error message

background content is %d characters, exceeding the hard limit of %d (aborting)

What it means

loadBackgroundFile counts the runes of the sanitized background content and enforces a hard limit of backgroundHardLimit (8000) characters, aborting the review when exceeded. A softer 2000-character limit only warns. The limit keeps the injected background from consuming too much of the LLM's context and degrading review quality.

Solutions

Trim the file to under 8000 characters, keeping only the most decision-relevant guidance.
Summarize the long document into a condensed bullet list (under the 2000-char soft limit for best quality).
Split content: keep only project-specific rules in --background-file; rely on the commit message fallback or --background for short notes.
Check `wc -m <path>` against the limit before running the review.

Example fix

// before: wc -m background.md -> 14500
// after
head -c important-sections.txt background.md  # manually curate
wc -m background.md  # -> 1800, under the soft limit

Defensive patterns

Strategy: validation

Validate before calling

// shell: check rune/char count against ocr's hard limit before invoking
chars=$(python3 -c "import sys;print(len(open(sys.argv[1],encoding='utf-8').read()))" "$BG_FILE")
[ "$chars" -le 8000 ] || { echo "background file too large: $chars chars"; exit 1; }

Try / catch

out, err := exec.Command("ocr", "review", "--background-file", bg).CombinedOutput()
if err != nil && strings.Contains(string(out), "exceeding the hard limit") {
	return fmt.Errorf("trim %s below 8000 characters: %w", bg, err)
}

Prevention

Keep background files concise; target under the 2000-character soft limit for best review quality.
Run `wc -m background.md` before reviews; CI can enforce a max.
Summarize long docs into bullet lists rather than pasting full documents.

When it happens

Trigger: `ocr review --background-file <path>` where the sanitized file contains more than 8000 characters (runes, not bytes).

Common situations: Dumping an entire architecture wiki page or coding standard document as background; concatenating multiple docs into one background file; a runaway export that pasted a whole codebase README plus design docs.

Related errors

AI-assisted analysis of alibaba/open-code-review@5cf97d0d15 (2026-09-02). Data as JSON: /api/errors/8756ff8e960b2fbb. Report an issue: GitHub.

Appendix: source

Thrown at cmd/opencodereview/background_file.go:102

	}

	cleaned := sanitizeMarkdown(string(raw))
	if cleaned == "" {
		return "", fmt.Errorf("background file %q is empty after sanitisation", path)
	}

	if strings.Contains(cleaned, backgroundOpenTag) || strings.Contains(cleaned, backgroundCloseTag) {
		return "", fmt.Errorf(
			"background file %q must not contain the reserved delimiters %q or %q",
			path, backgroundOpenTag, backgroundCloseTag,
		)
	}

	// Enforce the limits on the cleaned content only: the wrapper delimiters add
	// overhead the user cannot control, so counting them would make the reported
	// character count misleading.
	if n := len([]rune(cleaned)); n > backgroundHardLimit {
		return "", fmt.Errorf(
			"background content is %d characters, exceeding the hard limit of %d (aborting)",
			n, backgroundHardLimit,
		)
	} else if n > backgroundSoftLimit {
		fmt.Fprintf(os.Stderr,
			"[ocr] --background-file content is %d characters, exceeding the recommended %d (continuing but review quality might be impacted)\n",
			n, backgroundSoftLimit,
		)
	}

	return backgroundOpenTag + "\n" + cleaned + "\n" + backgroundCloseTag, nil
}

func sanitizeMarkdown(s string) string {
	var b strings.Builder
	b.Grow(len(s))

	for _, r := range s {

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