Regression after 1.3.12: tool-call failures (PowerShell + malformed JSON behavior) on official Kimi provider #20658

Description

Description

Title
Regression after 1.3.12: tool-call failures (PowerShell + malformed behavior) on official Kimi provider

Description
I’m seeing a regression between opencode-ai@1.3.12 and newer builds. Kimi is having trouble using Tools and using commands in powershell and WSL.

Repro matrix

• npx opencode-ai@1.3.12 → ✅ works
• newer build (latest) → ❌ tool-call errors / malformed behavior
• only reproduces with official Kimi coding-plan/provider
• same Kimi model via other providers works fine
• also seeing issues specifically involving PowerShell tool execution

Symptoms

• tool calls fail or behave incorrectly
• sometimes looks like malformed tool-call flow (bad follow-ups / unexpected structure)
• PowerShell-related tools behave inconsistently (execution/output issues)

Why this looks like a regression in core runtime (not model quality)

• same model works via other providers

• regression is strictly version-bound (1.3.12 → latest)

• strongly suggests OpenCode-side change in:

  • provider handling
  • tool execution
  • or message/tool-call flow

Likely culprit commits

Based on commit history after 1.3.12, these stand out:

Primary suspect

• refactor(shell): use Effect ChildProcess for shell command execution
• refactor(bash): use Effect ChildProcess for bash tool execution (#20496)

Reason:

• aligns directly with PowerShell/tool execution issues
• likely affects process spawning, env inheritance, stdio, exit handling

Secondary suspects (provider/message path)

• refactor(prompt): use Provider service in effect layers (#20167)
• refactor: use Effect services instead of async facades in provider, ...
• refactor: add Effect-returning versions of MessageV2 functions (#20374)

Reason:

• regression is provider-specific (official Kimi only)
• these commits change provider resolution, prompt construction, and message handling
• could affect tool-call formatting or follow-up turns

Expected behavior

• tool calls should behave the same as in 1.3.12 and previous versions
• no provider-specific breakage for the same model
• PowerShell tools should execute reliably

Actual behavior

• tool-call failures / malformed behavior in latest version
• reproducible only on official Kimi provider
• PowerShell tool execution unreliable

Plugins

none related

OpenCode version

OpenCode version: 1.3.13

Steps to reproduce

Just use kimi from the kimi codingp lan and ask it to read some skills, about 70% of the time it fails.
It also is adding : in the start of the commands when trying to run powershell commands (making invalid),
mixing xml tags in the json requests to use tools

Screenshot and/or share link

Operating System

Windows 11

Terminal

Warp, powershell, windows temrinal