Toss Bank Introduces 'Stylepack' Feedback Loop to Resolve Coding Agent Team Rule Violations

Toss Bank ML Engineer Kim Kyung-yoon unveiled Stylepack, a plugin designed to help Coding Agents adhere to team code conventions. The previous approach injected rules via Global Instructions such as AGENTS.md, but the 'Lost in the Middle' phenomenon, where initial rules are ignored in long conversations, led to frequent rule violations in the latter part of sessions.

Adding a Feedback Loop to the Agent Loop

Stylepack utilizes Hooks to provide immediate feedback like a Linter. The Hook executed immediately after file creation selects relevant rules using regex and filename patterns to inject into the Agent. By excluding AI calls, it minimizes latency, and injecting a maximum of 2 rules at a time prevents Context pollution.

Resolving Multi-File Dependency Issues

To catch multi-file dependency violations (e.g., referencing implementations instead of interfaces) that are difficult to detect with single-file checks, a second Hook was introduced to re-inspect the entire git diff at the end of the Agent Loop. This final safety net recognizes all changed files as a single unit, pointing out violations and prompting fixes.

Rule Management and Scalability

Stylepack resolves template aging issues by synchronizing the latest rules from a central repository. Rules are managed separately as 'Rule' for immediate shape-based judgment and 'Context' for runtime issue detection. Additionally, a process that promotes repeated feedback from PR reviews into rules reduces False Positives and systematizes team conventions.