[Bug]: OpenCode skills return zero in provider cache — pipe buffer truncates `opencode debug skill` output at 64KB

[jemini-pro]

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. Install opencode v1.18.20 and T3 Code v0.0.34-nightly.20260821.1151 on macOS arm64
2. Add 15+ skills to ~/.config/opencode/skills/ (each with SKILL.md frontmatter)
3. Start T3 server (t3 serve)
4. Wait for provider snapshot refresh
5. Inspect ~/.t3/caches/opencode.json — skills array is empty

To confirm the pipe truncation directly:

# File redirect — full output (138140 bytes)
opencode debug skill > /tmp/skills.json 2>/dev/null && wc -c /tmp/skills.json
# 138140

# Pipe — truncated at 64KB
opencode debug skill 2>/dev/null | wc -c
# 65536

# PTY — full output
script -q /dev/null opencode debug skill 2>/dev/null | wc -c
# 138302

Expected behavior

T3's OpenCode provider cache should list all discovered skills, same as Claude and Codex providers do. Skills should appear in the composer $ picker.

Actual behavior

T3's OpenCode provider cache reports skills: [] and slashCommands: []. Skills are invisible in the composer. Skills with model invocation disabled cannot be discovered or invoked.

Impact

Major degradation or frequent failure

Version or commit

T3 Code v0.0.34-nightly.20260821.1151, OpenCode v1.18.20 (also reproduced on v1.18.18)

Environment

macOS 26.6.2, Apple Silicon arm64. opencode binary is a Bun-compiled Mach-O executable. 26 skills on disk at ~/.config/opencode/skills/. Pipe output: 65536 bytes (truncated from 138140).

Logs or stack traces

~/.t3/caches/opencode.json after refresh:
{
  "displayName": "OpenCode",
  "enabled": true,
  "installed": true,
  "version": "1.18.20",
  "status": "ready",
  "skills": [],
  "slashCommands": [],
  ...
}

Root cause: opencode debug skill produces ~138KB of JSON. When T3 spawns it as a child process without a PTY, stdout is a pipe. The opencode binary (Bun-compiled) does not flush its write buffer properly to non-TTY stdout, so the pipe receives exactly 65536 bytes (64KB) and the rest is lost. The truncated JSON fails to parse in parseSkillsCliOutput, which silently returns []:

function parseSkillsCliOutput(stdout) {
    const result = decodeOpenCodeSkillsCliOutputExit(stdout);
    return isSuccess$1(result) ? result.value : [];
}

The models (opencode models --verbose) and agents (opencode agent list) commands work fine because their output stays under 64KB.

Workaround

Patch runSkillsCli in bin.mjs to redirect output to a temp file instead of relying on pipe stdout:

const runSkillsCli = () => runOpenCodeCommand({
    binaryPath: "sh",
    args: ["-c", `${input.binaryPath} debug skill > /tmp/.t3_oc_skills_${process.pid}.json && cat /tmp/.t3_oc_skills_${process.pid}.json && rm -f /tmp/.t3_oc_skills_${process.pid}.json`],
    ...commandContext
}).pipe(exit);

This patch is lost on npm install -g t3@nightly. PR #7572 (filesystem-based skill discovery) would fix this properly by reading SKILL.md files directly.

Related

• Fixed OpenCode skills not showing up in the composer #7572 — Fixed OpenCode skills not showing up in the composer (open PR)
• fix(server): bound OpenCode skill discovery output #7675 — fix(server): bound OpenCode skill discovery output (open PR)
• fix(server): report OpenCode skills in the provider snapshot #5683 — fix(server): report OpenCode skills in the provider snapshot (open PR)
• [Bug]: Cursor/OpenCode skill discovery returns zero skills despite skills existing on disk (Claude/Codex discover them fine) #2736 — [Bug]: Cursor/OpenCode skill discovery returns zero skills despite skills existing on disk (open issue)
• [Bug]: OpenCode CLI OSC title leak pollutes agent inventory — Agent not found → UnknownError #7754 — [Bug]: OpenCode CLI OSC title leak pollutes agent inventory (open issue)