[BUG] fail to call tools with XML format

[ionettr-hub]

Problem (one or two sentences)

Newer versions cannot parse XML tool call requests.

Context (who is affected and when)

Happens whenever a tool is called

Reproduction steps

VS Code version: 1.107.1
Auto-Approve: Read, Write, Browse
Mode: code
Prompt: /init

Roo said
[TOOL_CALL]
{tool => "read_file", args => {
--path ".claude/CLAUDE.md"
}}
[/TOOL_CALL]
[TOOL_CALL]
{tool => "list_files", args => {
--path ".roo"
}}
[/TOOL_CALL]

Model Response Incomplete
The model failed to use any tools in its response. This typically happens when the model provides only text/reasoning without calling the required tools to complete the task.Details

Roo is having trouble...
This may indicate a failure in the model's thought process or inability to use a tool properly, which can be mitigated with some user guidance (e.g. "Try breaking down the task into smaller steps").

Expected result

Tool calling

Actual result

Cannot tool call

Variations tried (optional)

I rolled back to version 3.36.16, and under Providers, changed its Tool Call Protocol to XML.

Then everything worked fine—it could read files, create summaries, and modify files.
However, after upgrading to newest version, problem has emerged.
And there is no "Tool Call Protocol" option on newer versions. It should be brought back.

App Version

3.46.2

API Provider (optional)

OpenAI Compatible

Model Used (optional)

No response

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

I've analyzed this issue and found the following:

Root Cause:
The extension now requires native function/tool calling support from API providers. When a model doesn't support native tool calling (as is common with some OpenAI-compatible proxies), it outputs tool calls in text format instead. The extension currently rejects these text-based tool calls with an error.

Analysis:
Looking at your tool call format:

[TOOL_CALL]
{tool => "read_file", args => {
--path ".claude/CLAUDE.md"
}}
[/TOOL_CALL]

This indicates your model is attempting to call tools but doesn't have native function calling enabled in the API. The extension is receiving this as plain text instead of a structured tool call.

Proposed Implementation Plan:

There's already an existing (unmerged) feature branch (feature/xml-tool-call-fallback-11011) that implements XML tool call fallback parsing. I propose extending this approach to:

1. Add XML tool call fallback parsing - Parse XML-formatted tool calls (e.g., <read_file><path>...</path></read_file>) from text responses when native tool calling fails
2. Include the custom format parser - Also parse the [TOOL_CALL]...[/TOOL_CALL] format your model outputs
3. Modify presentAssistantMessage - Instead of rejecting non-native tool calls with an error, attempt to parse and execute them as a fallback

This approach maintains backward compatibility while supporting providers that don't have full native tool calling support.

Alternative: If you prefer, we could add a provider-level setting (like the old "Tool Call Protocol" option) to explicitly choose between native and text-based tool calling.

Please mention @roomote in a comment saying whether you approve this plan (or prefer the alternative approach), and I'll proceed with the implementation.

[ionettr-hub]

@roomote approve

[roomote]

I've seen your approval and will start working on the XML tool call fallback implementation. I'll open a PR to share progress shortly.

[roomote]

Opened a draft PR with my attempt at addressing this: #11288

The PR adds an XML tool call fallback parser that detects tool calls in text responses (e.g. <read_file><path>...</path></read_file>) when the model does not support native function calling. The fallback only activates when no native tool_use blocks are found, so there is zero impact on providers that already work. Feedback welcome!