Skip to content

Subagent Compilation Checker

Problem

Large coding tasks often involve multiple independent components (e.g., microservices, libraries). Having the main agent handle compilation and error checking for every component in-context:

  • Blows Up Context Length: Including entire build logs or bytecode in the prompt is impractical.
  • Slows Down Inference: Sending full build commands and parsing verbose output in-context uses excessive tokens.

Additionally, when the agent's single "compile-and-run" step fails, it's hard to pinpoint which submodule caused the error without a more granular approach.

Solution

Spawn specialized "Compilation Subagents" to independently build and verify each code submodule, reporting back only:

1. Error Summary: File paths, line numbers, and error messages. 2. Binary Artifacts (if needed): Reference IDs (e.g., paths to compiled object files) rather than raw binaries.

Workflow: - Main Agent Request: "Compile module auth-service." - Spawn CompileSubagent(auth-service) - Subagent runs mvn clean install or go build ./auth-service. - Returns a structured error list or location of compiled artifact. - Main Agent: Updates its context with the concise error report (e.g., [{file: "auth_controller.go", line: 85, error: "undefined: UserModel"}]).

Example

sequenceDiagram MainAgent->>CompileSubagent: "Compile service A" CompileSubagent->>BuildEnv: go build ./serviceA alt Build Success CompileSubagent-->>MainAgent: {status: "success", artifact: "serviceA.bin"} else Build Failure CompileSubagent-->>MainAgent: [{file: "fileA.go", line: 10, error: "Syntax error"}] end MainAgent->>Context: Inject concise error summary

How to use it

  • Subagent Definition: Each subagent is a lightweight container or process with the appropriate runtime (e.g., JVM for Java code, Node for JavaScript).
  • Integration in RL Loop: Treat each subagent invocation as a tool call within the RL environment.
  • Error-Driven Reward: If the error list is non-empty, assign a negative reward proportional to the number of errors (e.g., reward = −len(error_list)), to encourage the agent to fix compile errors quickly.

Trade-offs

  • Pros:
  • Modular Isolation: The main agent never needs to load entire build logs into its context.
  • Parallel Builds: Multiple subagents can compile different modules in parallel, speeding up end-to-end workflow.
  • Cons/Considerations:
  • Infrastructure Overhead: Requires a mechanism to spin up and tear down multiple build environments.
  • Subagent Synchronization: If one module depends on another's build artifact, coordination policies must ensure the correct build order.

References

  • Inspired by "Subagent Spawning" for code-related subtasks in the Open Source Agent RL talk (May 2025).
  • Will Brown's note on decoupling long I/O-bound steps from the main model's inference to avoid context explosion.