fix: escape regex special characters in log error pattern matching

[kevintraver]

Summary

• Fix crash when log lines contain regex metacharacters (brackets, parentheses, etc.)
• Add fallback to substring matching if regex construction fails

Problem

The calculateErrorPriority function in mcp-server/app/mcp/tools.ts creates a regex pattern from error lines to count how many similar errors have occurred (used to boost priority for recurring errors). The pattern is built by replacing digit sequences with \d+ so that errors differing only in timestamps or line numbers are grouped together.

However, log lines commonly contain characters that have special meaning in regex:

• Timestamps: [12:34:56.789] — square brackets define character classes
• Context info: (connection closed) — parentheses define capture groups
• File paths: C:\Users\... — backslashes are escape characters
• Assertions: expected 5, got 10 — could contain +, *, ?

When these unescaped characters were passed to new RegExp(), it would throw errors like:

Invalid regular expression: Unterminated group
Invalid regular expression: Unterminated character class

This crashed the error analysis flow entirely.

Solution

1. Escape regex metacharacters first: Before replacing digits with \d+, escape all special regex characters ([.*+?^${}()|[\]\\]) using the standard \\$& replacement pattern
2. Add defensive try/catch: If regex construction still fails for an unexpected reason, fall back to simple substring matching (includes()) rather than crashing

// Before (crashed on brackets/parens)
const errorPattern = cleanLine.replace(/\d+/g, "\\d+").substring(0, 100)
const occurrences = allErrors.filter((e) => new RegExp(errorPattern).test(e)).length

// After (safe)
const escapedLine = cleanLine.replace(/[.*+?^${}()|[\]\\]/g, "\\$&")
const errorPattern = escapedLine.replace(/\d+/g, "\\d+").substring(0, 100)
let occurrences = 0
try {
  occurrences = allErrors.filter((e) => new RegExp(errorPattern).test(e)).length
} catch {
  occurrences = allErrors.filter((e) => e.includes(cleanLine.substring(0, 50))).length
}

Test plan

• Build canary and test with logs containing brackets/parentheses
• Verify error priority calculation still works for normal error lines

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🤖 Generated with Claude Code

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