[Bug]: OpenCode project-local agents are missing from the agent picker

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Create a project-local OpenCode agent at .opencode/agent/readonly.md inside a project's folder, not global config:

   ---
   description: Read-only agent for inspecting the project.
   mode: all
   permission:
     edit: deny
     bash: deny
     todowrite: deny
   ---
   
   You are a read-only agent.
   

2. From the project directory, run:

   opencode agent list
   

3. Confirm that OpenCode reports the project-local agent:

   build (primary)
   plan (primary)
   readonly (all)
   

4. Add or open the same directory as a project in T3 Code.

5. Select the OpenCode provider and open the agent selector.

Expected behavior

T3 Code should include visible project-local OpenCode agents whose mode is primary or all.

The readonly agent should appear alongside the built-in build and plan agents, matching the agents OpenCode reports when invoked from that project directory.

Actual behavior

The project-local readonly agent is absent from the T3 Code agent selector.

The OpenCode provider cache contains only the globally discovered build and plan agents, even though:

• The chat session is started with the correct project directory.
• opencode agent list from that directory reports readonly (all).
• The agent definition is valid and available in the native OpenCode interface.

This appears to happen because OpenCode agent capabilities are cached at the provider-instance level using a discovery directory that can differ from the selected project's directory. Project-local agents are therefore not represented in the cached model capabilities used by the composer.

Impact

Major degradation or frequent failure

Project-specific agents are a supported OpenCode configuration mechanism. Their absence means workflows and permission profiles defined by individual projects cannot be selected through T3 Code.

Version or commit

• T3 Code: 0.0.40
• OpenCode: 1.18.31

Environment

Linux, T3 Code web/server mode, OpenCode provider.

Logs or stack traces

# From the affected project:
$ opencode agent list

build (primary)
compaction (primary)
explore (subagent)
general (subagent)
plan (primary)
summary (primary)
title (primary)
readonly (all)

# Agent options represented in ~/.t3/caches/opencode.json:
[
  "build",
  "plan"
]

The corresponding OpenCode session metadata confirms that T3 starts the chat with the affected project as its working directory.

Related issues

• #7853 reported globally configured custom agents being omitted. It was closed after #8480 changed discovery to OpenCode's native app.agents API. This report is different: globally available built-ins are discovered, but agents defined under a specific project's .opencode/agent/ directory are still absent.
• #9833 concerns the separate client-side feature flag that hides the built-in plan agent. It does not cover project-local agent discovery.

Workaround

Use the project-local agent through the native OpenCode tui or web ui. No T3 Code workaround is currently known.

Start in apps/server and trace OpenCode provider capability discovery and its provider-level cache, paying attention to the discovery directory versus the selected project directory. Reproduce with a project-local .opencode/agent/readonly.md and compare the cached agents with opencode agent list. Done means project-local agents with primary or all mode appear in the T3 Code agent selector.