[BUG] GLM-5 via NVIDIA NIM emits malformed MCP tool JSON (Expected '}') in OpenCode v1.2.6

[chindris-mihai-alexandru]

Description

When using z-ai/glm5 via the NVIDIA NIM provider in OpenCode 1.2.6, tool calls intermittently emit malformed JSON arguments.

This causes repeated tool failures and retry loops with errors like:

Invalid input for tool tavily_tavily_search: JSON parsing failed: Text: {\"query\":\"Geoffrey Huntley LinkedIn Ralph Wiggum most viral reposts\".
Error message: JSON Parse error: Expected '}'

Similar malformed payloads occurred for multiple web tools in the same session (tavily_tavily_search, brave-search_brave_web_search, webfetch).

Environment

• OpenCode version: 1.2.6
• Model: z-ai/glm5
• Provider: NVIDIA NIM
• OS: macOS Sequoia 15.7.4

Steps to reproduce

1. Configure OpenCode to use z-ai/glm5 through NVIDIA NIM.
2. Ask for a web-research task that triggers multiple MCP/web tool calls.
3. Observe some tool calls being emitted with malformed JSON (missing closing braces / truncated payloads).
4. Session may enter repeated invalid-call retries.

Expected behavior

Tool arguments should always be valid JSON before execution (or be rejected/recovered with a structured retry).

Actual behavior

Some tool calls are emitted as malformed JSON and fail parser validation, often repeatedly in the same session.

Additional context

Potentially related issues (similar parsing symptoms across models/providers):

• [Bug] JSON Parse Error with Zhipu GLM-4.7: Stream chunks are concatenated incorrectly #7692
• [BUG] Parsing Issue on GLM-4.7 #10731
• 🐛 Bug Report: MCP Tool JSON Parsing Errors on OpenCode (GLM-4.7) #8102
• Error message: JSON Parse error: Expected '}' #12425

I’m unsure whether root cause is parser-side, stream chunk handling, provider behavior, or interaction between them; sharing this report in case the 1.2.x + GLM-5 + NIM combination has a distinct failure mode.

[github-actions]

This issue might be a duplicate of or closely related to existing issues. Please check:

• Error message: JSON Parse error: Expected '}' #12425: Error message: JSON Parse error: Expected '}' (similar exact error, affects multiple tools and models)
• 🐛 Bug Report: MCP Tool JSON Parsing Errors on OpenCode (GLM-4.7) #8102: MCP Tool JSON Parsing Errors on OpenCode (GLM-4.7) (similar core issue with invalid JSON tool arguments)

While this report is specific to GLM-5 via NVIDIA NIM, the underlying JSON parsing failure pattern appears consistent with these existing issues.

[chindris-mihai-alexandru]

Update: also reported upstream on NVIDIA Developer Forums with the same repro and error signature:
https://forums.developer.nvidia.com/t/nim-glm-5-malformed-tool-call-json-missing-via-openai-compatible-endpoint-opencode/360809

This should help confirm whether root cause is model output, serving/stream chunking, or client-side parser recovery in this stack combination.

[chindris-mihai-alexandru]

Added minimal reproducible prompt + exact malformed payloads gist: https://gist.github.com/chindris-mihai-alexandru/f3c114915f18618406030e6a2d8fa59b

[rekram1-node]

yeah the nvidia provider has been giving me some weirdness, it says openai compat but maybe there is something we arent properly sending them...