schlenks/dispatching-parallel-agents

Dispatching Parallel Agents

When to Use

Use when:

• 3+ test files failing with different root causes
• Multiple subsystems broken independently
• Each problem can be understood without context from others
• No shared state between investigations

Don't use when:

• Failures are related (fix one might fix others)
• Need to understand full system state
• Agents would interfere with each other (editing same files, using same resources)
• Exploratory debugging (you don't know what's broken yet)

The Pattern

1. Identify Independent Domains

Group failures by what's broken (e.g., File A: tool approval flow, File B: batch completion, File C: abort functionality). Each domain is independent -- fixing one doesn't affect the others.

2. Create Focused Agent Tasks

Each agent gets: specific scope (one test file/subsystem), clear goal (make these tests pass), constraints (don't change other code), expected output (summary of findings and fixes).

3. Dispatch in Parallel

Task("Fix agent-tool-abort.test.ts failures")
Task("Fix batch-completion-behavior.test.ts failures")
Task("Fix tool-approval-race-conditions.test.ts failures")
// All three run concurrently

Platform mapping: Claude uses Task/run_in_background; Codex uses spawn_agent and wait_agent. In Codex, define each worker's file ownership, tell workers they are not alone in the repo, and keep write scopes disjoint.

4. Review and Integrate

Read each summary, verify fixes don't conflict, run full test suite, integrate all changes.

Agent Prompt Structure

Three rules for good agent prompts:

1. Focused -- one clear problem domain
2. Self-contained -- all context needed to understand the problem
3. Specific about output -- what should the agent return?

Example:

Fix the 3 failing tests in src/agents/agent-tool-abort.test.ts:
1. "should abort tool with partial output capture" - expects 'interrupted at'
2. "should handle mixed completed and aborted tools" - fast tool aborted
3. "should properly track pendingToolCount" - expects 3 results, gets 0

These are timing/race condition issues. Replace arbitrary timeouts with
event-based waiting. Do NOT just increase timeouts.
Return: Summary of root cause and changes made.

See references/agent-prompt-example.md for full annotated version.

Common Mistakes

• Too broad ("Fix all the tests") -> Be specific ("Fix agent-tool-abort.test.ts")
• No context ("Fix the race condition") -> Paste error messages and test names
• No constraints (agent refactors everything) -> Scope explicitly ("Fix tests only")
• Vague output ("Fix it") -> Request summary ("Return root cause and changes")

Verification

After agents return:

1. Review each summary -- understand what changed
2. Check for conflicts -- did agents edit same code?
3. Run full suite -- verify all fixes work together
4. Spot check -- agents can make systematic errors

Reference Files

• references/agent-prompt-example.md: full annotated prompt example with test names and constraints
• references/real-session-example.md: complete scenario: dispatch, results, integration, time saved
• references/real-world-impact.md: stats from debugging session (2025-10-03)

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