# Browser4 Fix Bug > Fix bugs in code using a compile-test-fix loop: run the build/tests, read the error, locate the faulty lines, edit, and re-verify until green. Use when the user reports a build failure, test failure, crash, or asks to fix an error in Browser4 plugins, Kotlin, TS/JS, Python, or scripts. - Skill: `platonai/browser4-fix-bug` (Agent Skill) - Install (CLI): `npx skillmds@latest add platonai/browser4-fix-bug` - Raw SKILL.md: https://api.skillmd.com/api/skills/platonai/browser4-fix-bug/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: platonai (https://skillmd.com/u/platonai) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/platonai/browser4-fix-bug --- # browser4-fix-bug ## Quick Start ```text coding.shell(command="mvn -pl -am compile -DskipTests") # 1. reproduce the error coding.readLines(path=, startLine=, endLine=) # 2. read the failing code coding.replace(path=, old="...", new="...") # 3. smallest possible edit coding.shell(command="mvn -pl -am compile -DskipTests") # 4. re-verify until green ``` Drive a bug from "it fails" to "it passes" with a disciplined compile-test-fix loop. Never guess — read the actual error, make the smallest edit, and re-verify. ## When to Use - User reports a build/compile failure or a failing test - A plugin, skill script, JS, or shell script errors at runtime - User says "fix this error", "the build is broken", "tests fail", "it crashes" - LSP diagnostics (`coding.diagnostics`) report errors in a file ## How It Works The compile-test-fix loop is error-driven: reproduce the failure, read the exact error, locate the faulty lines with minimal context, make the smallest possible edit, and re-verify. Never guess — every iteration starts from the actual error output. ## Patterns ### 1. Build/compile failure ```text coding.shell(command="mvn -pl -am compile -DskipTests") coding.readLines(path=, startLine=, endLine=) coding.replace(path=, old="...", new="...") coding.shell(command="mvn -pl -am compile -DskipTests") ``` ### 2. Failing test ```text coding.shell(command="mvn test -pl -Dtest=") coding.readLines(path=, startLine=, endLine=) coding.replace(path=, old="...", new="...") ``` ### 3. Runtime error in plugin/script ```text coding.diagnostics(path=) coding.readLines(path=, startLine=, endLine=) coding.replace(path=, old="...", new="...") ``` ## Flags `coding` tools take structured arguments, not CLI flags — see Workflow below for each tool's parameters. ## Errors & Recovery | Symptom | Cause | Fix | |---------|-------|-----| | Build still fails after an edit | Edit didn't address the real error | Re-read the error output; check the exact line numbers | | Edit had no effect | Wrong file or path | Verify the path with `coding.readLines` before editing | | Loop never goes green | Fix introduced a new error | Revert (`coding.revert`), then make a smaller edit | ## Workflow ### 1. Reproduce — get the concrete error ``` coding.shell(command="mvn -pl -am compile -DskipTests") # Kotlin/Maven coding.shell(command="tsc --noEmit") # TS coding.shell(command="python -m py_compile .py") # Python coding.shell(command="bash -n .sh") # Bash tab.eval(expression=) + tab.console() # Browser JS ``` If LSP servers are available, prefer instant pre-checks first: `coding.diagnostics(path=)` — structured errors with line numbers. ### 2. Locate — read the failing code, not the whole file ``` coding.readLines(path=, startLine=, endLine=) coding.references(path=, symbol=) # impact check before edits coding.diff(path=) # what changed recently ``` ### 3. Fix — smallest possible edit | Symptom | Tool | |---------|------| | Wrong string | `coding.replace(path, oldStr, newStr)` | | Pattern-based | `coding.replaceRegex(path, regex, replacement)` | | Whole block | `coding.editLines(path, startLine, endLine, content)` | | Add a line | `coding.insertAfter(path, anchor, content)` | | Edit went wrong | `coding.revert(path)` then redo | ### 4. Verify — rerun the exact command from step 1 Loop 1→4 until green. **Do not** make multiple unrelated edits between verifications — one fix, one check, so you always know which edit worked. ### 5. Report Summarize: root cause (one line), fix (file:line), verification result (build/test output tail). If the fix took more than 3 attempts, re-read the error output carefully before continuing — do not fire-and-forget edits. ## Rules 1. **Read before you write.** Never edit a line you have not seen. 2. **One change per verify cycle.** Batch edits only after each is proven. 3. **Use diagnostics when available.** `coding.lspServers` tells you which language servers are installed; prefer `coding.diagnostics` over a full build for TS/JS/Python. 4. **Prefer editLines/insertAfter over replace** for block edits — less chance of matching the wrong occurrence. 5. **Revert is cheap.** If an edit makes things worse, `coding.revert` restores the pre-edit snapshot, then retry with a different approach. 6. **Stop and escalate** after 5 failed attempts — report the exact error and your attempted fixes rather than degrading the code. ## Examples ``` User: 编译报错了，browser4-seo 插件 mvn compile 失败 Agent: 1. coding.shell(command="mvn -pl browser4-plugins/browser4-seo -am compile -DskipTests") 2. → error: SeoToolExecutor.kt:42 Unresolved reference 'foo' 3. coding.readLines(path="browser4-plugins/browser4-seo/src/main/kotlin/ai/platon/pulsar/seo/tools/SeoToolExecutor.kt", startLine=34, endLine=50) 4. coding.replace(path=..., oldStr="foo", newStr="bar") 5. coding.shell(command="mvn -pl browser4-plugins/browser4-seo -am compile -DskipTests") → BUILD SUCCESS 6. 报告：根因 import 拼写；修复 SeoToolExecutor.kt:42；mvn compile 通过 ```