fix(config): properly handle prompt_append for Prometheus agent

[gabriel-ecegi]

Summary

Fixes #723 — prompt_append in agent overrides is ignored for Prometheus agent.

Problem

When using prompt_append in oh-my-opencode.json for Prometheus:

{
  "agents": {
    "prometheus": {
      "prompt_append": "## Custom Rules\nUse max 2 commits."
    }
  }
}

The prompt_append was ignored because config-handler.ts used shallow spread:

agentConfig["prometheus"] = { ...prometheusBase, ...prometheusOverride }

This leaves prompt_append as a separate property instead of appending it to the prompt field.

Solution

Extract prompt_append from the override and explicitly append it to the base prompt:

const { prompt_append, ...restOverride } = prometheusOverride;
const merged = { ...prometheusBase, ...restOverride };
if (prompt_append && merged.prompt) {
  merged.prompt = merged.prompt + "\n" + prompt_append;
}

Changes

• src/plugin-handlers/config-handler.ts: Handle prompt_append properly for Prometheus
• src/plugin-handlers/config-handler.test.ts: Add test verifying prompt_append is appended

Testing

• All 12 existing tests pass
• New test verifies prompt_append content appears at end of prompt
• Typecheck passes

Related

• Fixes [Bug]: oh-my-opencode.json tools and permissions agent overrides not working as expected. #723
• Related to Agent overrides for reasoningEffort/variant not applied to Prometheus/Metis/Momus #1219 (agent overrides not applied)
• Supersedes stalled PR fix(agent-config): use mergeAgentConfig for prometheus and opencode-builder #719 (which had test import issues and malformed code)

---

Summary by cubic

Properly appends prompt_append from Prometheus agent overrides to the base prompt instead of ignoring it. Fixes #723 and ensures custom rules appear at the end of the final prompt.

• Bug Fixes
  • Extracts prompt_append from the override and appends it to merged.prompt.
  • Replaces shallow spread that discarded prompt_append.
  • Adds a test to confirm base prompt is preserved and ends with the custom instructions.

^{Written for commit 2094b33. Summary will update on new commits.}

[github-actions]

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[gabriel-ecegi]

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[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.