filesystem read_multiple_files and edit_file Input validation error: Invalid arguments: expected array, received string

[audioscavenger]

Before submitting your bug report

• I've tried finding an answer on the Continue docs site
• I'm not able to find an open issue that reports the same bug
• I've seen the troubleshooting guide on the Continue Docs

Relevant environment info

- OS: Windows 10 LTSC 21H2
- Continue version: 2.0.0
- IDE version: VSCodium 1.135.06.55
- Model: qwen3.8:27b
- config:
  
name: Local Max VRAM Config
version: 1.0.0
schema: v1
models:
  - name: Qwen 3.8 27b (256K)
    provider: ollama
    model: qwen3.8:27b
    contextLength: 64000
    defaultCompletionOptions:
      temperature: 0
      contextLength: 32000
      maxTokens: 16000
    capabilities:
      - tool_use
    roles: [chat, edit, apply, summarize]
    timeout: 120000

  - name: Qwen 2.5 coder 32b (32K)
    provider: ollama
    model: qwen2.5-coder:32b
    contextLength: 32000
    defaultCompletionOptions:
      temperature: 0
      contextLength: 32000
      maxTokens: 16000
    roles: [chat, edit, apply, autocomplete]
    timeout: 120000

  - name: Apply model
    provider: ollama
    model: qwen2.5-coder:1.5b
    contextLength: 32000
    defaultCompletionOptions:
      temperature: 0
      contextLength: 32000
      maxTokens: 16000
    roles: [apply, autocomplete]
    timeout: 120000

  - name: Nomic Embed
    provider: ollama
    model: nomic-embed-text:latest
    roles:
      - embed
mcpServers:
  - name: filesystem
    command: node
    args:
      - "E:\\GPT\\Ollama\\mcp-tee.js"
      - "-y"
      - "@modelcontextprotocol/server-filesystem"
      - "E:\\www\\letbox\\docker\\dms\\dms-gui"
  

VScodium about:

Version: 1.135.06055
Commit: 1a46a584725d5dd330e0bcd7f5510f24990efcf2
Date: 2026-08-25T14:26:52Z
Electron: 42.8.1
ElectronBuildId: undefined
Chromium: 148.0.7778.280
Node.js: 24.18.1
V8: 14.8.178.38-electron.0
@github/copilot: Unknown
@github/copilot-sdk: Unknown
OS: Windows_NT x64 10.0.19044

Description

Continue intermittently fails to pass an array to the tools requiring an array. I got the bug with read_file and therefore, resorted to use nodeJS mcp filesystem tool with same problems.

• project: classic ReactJS I am trying to fix bugs for
• prompt: Fix the blatant bugs in @DataTable.jsx and offer code change with comments above the changes, directly into the file. Add more context by reading maximum 3 files that either use this component or are critical for the component to work.
• result:

• Errors seen from the IDE:

filesystem_read_multiple_files failed with the message: [{"type":"text","text":"MCP error -32602: Input validation error: Invalid arguments for tool read_multiple_files: Invalid input: expected array, received string at paths"}]
filesystem_edit_file failed with the message: [{"type":"text","text":"MCP error -32602: Input validation error: Invalid arguments for tool edit_file: Invalid input: expected array, received string at edits\nInvalid input: expected boolean, received string at dryRun"}]

To reproduce

I have concentrated my research on filesystem_read_multiple_files because it's easy to reproduce. The first call works, it reads the files, the second call fails, always.

In both cases, the TRACE log from ollama always reports the same command:

time=2026-10-05T16:30:29.366-07:00 level=TRACE source=qwen3coder.go:117 msg="qwen events parsed" events="[{raw:\n<function=filesystem_read_multiple_files>\n<parameter=paths>\n[\"common.mjs\",\"frontend/src/frontend.mjs\", \"frontend/src/components/AlertMessage.jsx\"]\n</parameter>\n</function>\n}]" state=0 acc=""
time=2026-10-05T16:30:42.541-07:00 level=TRACE source=qwen3coder.go:117 msg="qwen events parsed" events="[{raw:\n<function=filesystem_read_multiple_files>\n<parameter=paths>\n[\"frontend/src/pages/Logins.jsx\",\"frontend/src/pages/Accounts.jsx\",\"frontend/src/components/Translate.jsx\"]\n</parameter>\n</function>\n}]" state=0 acc=""

VSCodium dev console logs nothing at all, so I resorted to a trick to log what Continue sends to the filesystem server: Put a small wrapper between Continue and the server that copies everything Continue sends it into a file.

const { spawn } = require('child_process');
const fs = require('fs');
const log = fs.createWriteStream('"E:\\GPT\\Ollama\\mcp-tee.log', { flags: 'a' });
const child = spawn('npx.cmd', process.argv.slice(2), { stdio: ['pipe', 'inherit', 'inherit'], shell: true });
process.stdin.on('data', d => { log.write(d); child.stdin.write(d); });
process.stdin.on('end', () => child.stdin.end());
child.on('exit', c => process.exit(c));

The config.yaml reflects the use of that wrapper. The wrapper log is telling!

{"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"continue-client","version":"1.0.0"}},"jsonrpc":"2.0","id":0}
{"method":"notifications/initialized","jsonrpc":"2.0"}
{"method":"tools/list","params":{},"jsonrpc":"2.0","id":1}
{"method":"tools/call","params":{"name":"read_multiple_files","arguments":{"paths":["common.mjs","frontend/src/frontend.mjs","frontend/src/components/AlertMessage.jsx"]}},"jsonrpc":"2.0","id":2}
{"method":"tools/call","params":{"name":"read_multiple_files","arguments":{"paths":"[\"frontend/src/pages/Accounts.jsx\",\"frontend/src/components/Translate.jsx\"]"}},"jsonrpc":"2.0","id":3}
{"method":"tools/call","params":{"name":"read_text_file","arguments":{"path":"frontend/src/pages/Accounts.jsx"}},"jsonrpc":"2.0","id":4}
{"method":"tools/call","params":{"name":"read_text_file","arguments":{"path":"frontend/src/components/Translate.jsx"}},"jsonrpc":"2.0","id":5}

That capture is the strongest evidence: the same tool, the same schema, and the same kind of valid model output, yet call 3 arrives at the server as a quoted string while call 2 arrives as a real array.

So the string is created before Continue writes to the MCP server. The wrapper only sees the end of the chain, so it can't say whether Ollama returned a string or Continue stringified it.

The two suspects are:

• Ollama's qwen3coder parser
• Continue after it receives the call.

It's really sad because everything else almost work.

Log output

filesystem_read_multiple_files failed with the message: [{"type":"text","text":"MCP error -32602: Input validation error: Invalid arguments for tool read_multiple_files: Invalid input: expected array, received string at paths"}]
filesystem_edit_file failed with the message: [{"type":"text","text":"MCP error -32602: Input validation error: Invalid arguments for tool edit_file: Invalid input: expected array, received string at edits\nInvalid input: expected boolean, received string at dryRun"}]

[audioscavenger]

something is definitely breaking the use of arrays with tools, after the first call that always works. The first tool call can be anything with use of arrays or not, but all subsequent calls to any tool using arrays like edit_file etc, will fail:

[bunnysayzz]

Root cause is in how the agent serializes tool arguments before sending them to the model. When a tool call returns and the agent builds the next request, array-type arguments are being serialized as a JSON string (e.g. "["file1", "file2"]") instead of a proper JSON array. The model then sends back the string form, which fails the Zod schema validation that expects an array.

This is a TypeScript/Node VS Code extension — cannot build and run the test suite in this environment. Posting the plan here; will open the PR from a Node environment once I've traced the exact serialization site.