Build Fix — Universal Build Error Resolver

Detects language from error output, loads the appropriate reference, classifies the error by fixability, applies the fix, and chains into mk:verify to confirm the build is green.

When to Use

• Build command fails (npm run build, tsc, go build, python -m build, cargo build)
• Type check errors (TypeScript TS\d{4}, mypy)
• Compilation errors in any language
• Triggers: "build failed", "fix build", "compilation error", "type error"

Phase Anchor

Phase: 3 (Build GREEN) Handoff: If mk:verify passes → proceed to Phase 4 (Review). If 3 attempts exhausted → escalate to user.

Process

Step 1: Capture Error Output

Run the failing build command and capture full output. If error output was passed as input, use that directly.

Step 2: Detect Language

Match error patterns in order (first match wins):

Pattern	Language	Reference
error TS\d{4}:	TypeScript	references/typescript-errors.md
SyntaxError: or ModuleNotFoundError: or IndentationError:	Python	references/python-errors.md
cannot find package or undefined: or syntax error near (Go)	Go	references/general-errors.md
error[E\d{4}] (Rust)	Rust	references/general-errors.md
Any other pattern	Unknown	references/general-errors.md

Load the matched reference file before proceeding to Step 3.

Step 3: Classify Error Fixability

After loading the reference, classify the error:

Class	Description	Action
auto-fixable	Syntax errors, missing imports, simple type mismatches	Apply fix immediately
suggest-with-confidence	Wrong argument types, missing interface properties	Propose fix, apply after brief explanation
report-only	Runtime errors, architectural issues, circular dependencies	Describe the problem and root cause; do not auto-fix

Auto-fixable examples: TS1005 Expected semicolon, TS2307 Cannot find module (missing import) Suggest-with-confidence examples: TS2322 type mismatch, TS2345 argument type mismatch Report-only examples: Circular dependency, architectural type mismatch requiring refactor

Step 4: Apply Fix

For auto-fixable and suggest-with-confidence:

• Apply the minimal change that resolves the error
• Do not refactor beyond what the error requires (YAGNI)
• Follow security-rules.md — do NOT use any type as a fix

For report-only:

• Describe what needs to change and why
• Stop — do not modify files
• Return the diagnosis to the developer

Step 5: Verify Fix

Run mk:verify (or the project's build command directly if verify not available).

Step 6: Iterate (Max 3 Attempts)

If the build still fails after applying a fix:

• Attempt 2: re-classify with updated error output, try different approach
• Attempt 3: re-classify one final time with a different approach

After 3 failed attempts, escalate to user with:

• All 3 error outputs
• All 3 attempted fixes and why each failed
• Suspected root cause
• Suggested next steps (architectural review, dependency update, etc.)

Attempt Counter

Track attempts in the session. Reset counter when switching to a different error. Per tdd-rules.md Rule 4: max 3 self-healing attempts, then escalate.

Reference Files

• references/typescript-errors.md — TS error codes with fix patterns
• references/python-errors.md — Python exception types with fix patterns
• references/general-errors.md — Framework-agnostic build error patterns

Security Constraint

NEVER use TypeScript any as a fix for type errors. Always use unknown + type guards or fix the actual type mismatch. See security-rules.md — any type is a blocked pattern.

Gotchas

• Stale .tsbuildinfo hides real errors on warm incremental builds — tsc --incremental skips files it thinks are unchanged; a corrupt or out-of-date .tsbuildinfo causes TS to report 0 errors while the actual output is broken; delete .tsbuildinfo and rerun tsc --noEmit before declaring the build clean.
• Platform-specific native binaries fail silently after npm ci on a different OS — packages like esbuild, sharp, @swc/core ship OS-specific binaries; a node_modules/ copied from macOS to Linux (or via Docker volume mount) silently uses wrong binaries until a cryptic "invalid ELF header" or "exec format error" appears at runtime; always run npm ci fresh inside the container, never share node_modules across platforms.
• Peer dependency warnings mask fatal version mismatches — npm install prints peer dep warnings as non-fatal by default; a eslint@8 peer warning can hide the real problem that @typescript-eslint/parser@6 requires eslint@8 but 9 is installed, causing TypeError: eslint.linter is not a constructor at runtime; always resolve peer warnings before treating the build as clean.
• Different error output on cold vs warm cache means fixing the wrong error — a first clean build often surfaces errors that incremental builds skip; fix errors only after a full clean build (rm -rf dist .tsbuildinfo && tsc) to ensure you're seeing the complete error set, not just the delta from last run.
• Circular dependencies aren't caught by tsc but break bundlers at runtime — TypeScript compiles circular imports without error; Vite/webpack may emit a broken bundle where one module resolves to {} because the other hadn't initialized yet; run madge --circular src/ to detect cycles as part of build triage.