[Bug]: Gemini from Vertex Error: edit functionDeclaration parameters.edits.lines schema didn't specify the schema type field.

[Ritel-T]

Prerequisites

• I will write this issue in English (see our Language Policy)
• I have searched existing issues to avoid duplicates
• I am using the latest version of oh-my-opencode
• I have read the documentation or asked an AI coding agent with this project's GitHub URL loaded and couldn't find the answer

Bug Description

Related (not identical issue): #2074 , QuantumNous/new-api#3022 , anomalyco/opencode#15795.

When using Google Vertex AI gemini-3-flash-preview, gemini-3.1-pro-preview or gemini-3.1-pro-preview-customtools models:

Unable to submit request because edit functionDeclaration parameters.edits.lines schema didn't specify the schema type field. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling

No such problem with glm-5 from Vertex.

No such problem when using original OpenCode without Oh-My-Openagent. (Related fix anomalyco/opencode#15318 but not the identical error)

All the related issues are talking about any_of must be the only field set but this one is not.

Screenshot: upper without oMo, lower with oMo.

Steps to Reproduce

Use Gemini models from Google Vertex AI provider in OpenCode with Oh-My-Openagent.

Expected Behavior

No error.

Actual Behavior

Unable to submit request because edit functionDeclaration parameters.edits.lines schema didn't specify the schema type field. Learn more: https://cloud.google.com/vertex-ai/generative-ai/docs/multimodal/function-calling

Doctor Output

OpenCode version 1.2.23
oMo version v3.11.0

Error Logs

Configuration

Additional Context

No response

Operating System

Windows

OpenCode Version

1.2.23

[code-yeongyu]

[sisyphus-bot] Confirmed Bug — P2

Root Cause

The hashline Edit tool (src/tools/hashline-edit/tools.ts) defines the lines parameter as a union type: string | string[] | null. This generates a JSON schema with anyOf at the lines field level without a top-level type property.

Google Vertex AI's function calling has stricter schema validation than other providers and rejects schemas where a property lacks a type field (even if anyOf is present). This only affects oMo's custom Edit tool — vanilla OpenCode's Edit tool doesn't have this issue.

Affected Files

• src/tools/hashline-edit/tools.ts — lines union schema definition (lines 32-34)
• src/plugin/tool-registry.ts — registers hashline Edit tool
• src/plugin/normalize-tool-arg-schemas.ts — schema normalization (doesn't handle this case)

Fix Approach

1. Preferred: Simplify lines to a single canonical type (string[] only) and handle string/null normalization internally in the tool handler:

// Schema: lines as string[] only
lines: z.array(z.string()).describe("Replacement lines")

// Handler: normalize input
const normalizedLines = typeof input.lines === 'string' ? [input.lines] : input.lines ?? []

2. Alternative: Add Vertex-specific schema normalization in normalize-tool-arg-schemas.ts that converts anyOf unions to the most permissive single type with a type field.