[Bug]: Librarian agent fails with JSON Parse error: Unexpected EOF

[travka]

Describe the bug

The librarian agent consistently fails with a JSON Parse error: Unexpected EOF when invoked via call_omo_agent or background_task.

Interestingly, the explore agent, configured with the exact same model (google/antigravity-gemini-3-flash), works perfectly.

To Reproduce

1. Configure oh-my-opencode.json with a valid Gemini model for librarian (e.g., google/antigravity-gemini-3-flash).
2. Run a task that triggers the librarian agent, or call it directly:

   call_omo_agent({
     description: "Test librarian",
     prompt: "Search for documentation about X",
     run_in_background: false,
     subagent_type: "librarian"
   })

3. See error: Error: Failed to send prompt: JSON Parse error: Unexpected EOF

Expected behavior

The librarian agent should successfully spawn, perform its search/retrieval tasks, and return a response.

Environment

• oh-my-opencode version: 2.14.0
• OpenCode version: 1.1.12
• Model used: google/antigravity-gemini-3-flash
• Platform: macOS (Darwin)

Additional context

• explore agent works fine with the same model.
• oracle agent (GPT-5.2) works fine.
• The error happens immediately upon sending the prompt.
• Session logs show the user message being sent to the librarian session, but the assistant never responds (EOF reached before response start).

Possible causes:

• Malformed system prompt for the librarian agent causing Gemini to return empty/invalid JSON.
• Transient API issue (though persistent across multiple retries).
• Regression in 2.14.0 related to librarian's tool definitions or instructions.

[MillionthOdin16]

I think the web search exa tool definition in librarian.ts in the prompt may have a bug.

I was getting a high number of invalid tool calls that caused issues and I think there's an extra 'exa' that causes issues.

I changed

websearch_exa_web_search_exa(...)

to

websearch_web_search_exa(...)

diff --git a/src/agents/librarian.ts b/src/agents/librarian.ts
index 27b6a65..[new] 100644
--- a/src/agents/librarian.ts
+++ b/src/agents/librarian.ts
@@ -240,7 +240,7 @@
 | **Official Docs** | context7 | \`context7_resolve-library-id\` → \`context7_query-docs\` |
- | **Find Docs URL** | websearch_exa | \`websearch_exa_web_search_exa("library official documentation")\` |
+ | **Find Docs URL** | websearch_exa | \`websearch_web_search_exa("library official documentation")\` |
 | **Sitemap Discovery** | webfetch | \`webfetch(docs_url + "/sitemap.xml")\` to understand doc structure |
 | **Read Doc Page** | webfetch | \`webfetch(specific_doc_page)\` for targeted documentation |
- | **Latest Info** | websearch_exa | \`websearch_exa_web_search_exa("query 2025")\` |
+ | **Latest Info** | websearch_exa | \`websearch_web_search_exa("query 2025")\` |
 | **Fast Code Search** | grep_app | \`grep_app_searchGitHub(query, language, useRegexp)\` |
 | **Deep Code Search** | gh CLI | \`gh search code "query" --repo owner/repo\` |
 | **Clone Repo** | gh CLI | \`gh repo clone owner/repo \${TMPDIR:-/tmp}/name -- --depth 1\` |

[asim-git]

Still occurring in v3.0.1

I can confirm this issue persists in v3.0.1 and affects multiple agent types:

Affected agents:

• librarian ❌
• oracle ❌
• metis ❌
• momus ❌

Working agents:

• explore ✅
• sisyphus-junior (via category="quick") ✅

Environment:

• oh-my-opencode: 3.0.1
• OS: macOS (Darwin)
• Tested with: Anthropic (claude-sonnet-4-5), OpenCode Zen models

Key observations:

1. The error occurs immediately upon agent spawn, before receiving any response
2. Switching model providers does not help - same error with both Anthropic and Zen
3. explore agent with the SAME model works perfectly
4. delegate_task with category parameter works, but subagent_type fails for these agents

This suggests the issue is specific to how these particular agents (librarian/oracle/metis/momus) are initialized, not a model or API connectivity issue.

[MadKangYu]

Root Cause Analysis Complete

Summary

This is an OpenCode core bug, not an oh-my-opencode plugin bug.

The Problem

1. User config (opencode.json) correctly defines custom models like google.models.antigravity-claude-sonnet-4-5
2. Plugin config correctly assigns these models to agents (e.g., librarian.model = "google/antigravity-claude-sonnet-4-5")
3. opencode debug agent librarian shows the correct model configuration
4. BUT at runtime, when Provider.getModel("google", "antigravity-claude-sonnet-4-5") is called in SessionPrompt.loop, it throws ProviderModelNotFoundError
5. The Provider's runtime state is populated from models.dev cache, and custom config models aren't accessible via Provider.getModel()

Evidence

• Runtime logs show: providerID=anthropic modelID=claude-sonnet-4-5 (fallback) instead of the configured google/antigravity-claude-sonnet-4-5
• The resolved config (opencode debug config) includes antigravity models under provider.google.models ✅
• Agent config shows correct model ✅, but runtime invocation uses wrong provider ❌

Technical Details

In OpenCode's SessionPrompt.loop function:

const model = await Provider.getModel(lastUser.model.providerID, lastUser.model.modelID);
// ...
const taskModel = task.model ? await Provider.getModel(task.model.providerID, task.model.modelID) : model;

Provider.getModel() looks up models in state.providers[providerID].models[modelID], which is populated from models.dev cache. Config-defined custom models under provider.{name}.models are NOT being made accessible through this lookup.

Next Steps

1. File issue with OpenCode upstream about config models not being accessible via Provider.getModel()
2. Workaround: Use models that exist in models.dev cache (standard provider models) instead of custom antigravity-* models for agents

Workaround for Users

Change oh-my-opencode.json to use standard models:

{
  "agents": {
    "librarian": {
      "model": "anthropic/claude-sonnet-4-5"  // instead of google/antigravity-claude-sonnet-4-5
    },
    "explore": {
      "model": "google/gemini-2.5-flash"  // instead of google/antigravity-gemini-3-flash
    }
  }
}

[Jovines]

Hi @travka and everyone,

Just checking if there's any update on this issue? I'm experiencing the same problem with the librarian agent using minimax coding plan model.

Any progress would be appreciated. Thanks!

[travka]

Hi, didnt catch this for a while