[BUG] failed to read file

[superguo]

Problem (one or two sentences)

Expected to read the specified file successfully but failed in VS Code. There was no such an error in the previous version.

Context (who is affected and when)

Happens when I enter the prompt involving accessing a local file.

Reproduction steps

1. Environment:
   macOS: Tahoe 26.0.1
   VS Code version: 1.107.1
   Auto-Approve: Read, Write, Browse
2. Action:
   mode: Architect
   primpt message: It seems you are going to create a new screen to tailor new section each. But I just want to do the tailoring inplace - just tap an icon button right next to the editor of each section so the user can tailor it. Can you just modify the plan ( /docs/1-page-resume/ai-prompts-for-resume/08-remaining-phases-plan.md ) before you implement it?
3. What I saw of each step:
   Roo said
   I need to read the existing plan document to understand the current plan and then modify it according to the user's feedback about in-place tailoring (adding icon buttons next to each section editor) rather than creating separate tailoring screens.

<read_file>


docs/1-page-resume/ai-prompts-for-resume/08-remaining-phases-plan.md


</read_file>

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 said
<read_file>



docs/1-page-resume/ai-prompts-for-resume/08-remaining-phases-plan.md



</read_file>

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 said
I need to use the correct tool format. Let me read the file using the read_file tool.

<read_file>


docs/1-page-resume/ai-prompts-for-resume/08-remaining-phases-plan.md


</read_file>

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

The task starts and modifies the expected file

Actual result

Failed to read the file

Variations tried (optional)

No response

App Version

3.37.1

API Provider (optional)

DeepSeek

Model Used (optional)

deepseek-chat

Roo Code Task Links (optional)

No response

Relevant logs or errors (optional)

[roomote]

I've analyzed this issue and here's my proposed implementation plan:

Root Cause Analysis

The issue occurs because the DeepSeek model (deepseek-chat) is outputting XML-style tool call syntax in its text response (e.g., <read_file>...</read_file>) instead of using the native OpenAI-format function calling API. This causes the "Model Response Incomplete - The model failed to use any tools in its response" error.

The codebase correctly configures DeepSeek to use native tools:

• supportsNativeTools: true in model config
• Tools are passed via the OpenAI-compatible API
• System prompt instructs: "Use the provider-native tool-calling mechanism. Do not include XML markup or examples."

However, DeepSeek models sometimes ignore these instructions and output XML-style tool calls in their text response instead of making proper API tool calls.

Proposed Solution

Add a fallback XML tool parser specifically for DeepSeek (and potentially other OpenAI-compatible providers) that:

1. Detects XML tool calls in text responses when native tool calling was expected but no tool_use blocks were received
2. Parses the XML tool syntax and converts it to proper tool_use format
3. Executes the tools as if they were native tool calls

Implementation Details

1. Create a new utility src/core/assistant-message/XmlToolFallbackParser.ts:

   • Parse XML-style tool calls from text content (e.g., <read_file><path>...</path></read_file>)
   • Convert to ToolUse format compatible with the existing tool execution pipeline
   • Generate synthetic tool_use IDs for the tool_result blocks

2. Modify Task.ts in the streaming completion handler (around line 3200-3320):

   • After streaming completes, if using native protocol AND no tool_use blocks were found AND text contains XML tool patterns:
     • Parse the XML tool calls from the text
     • Add them to assistantMessageContent as proper ToolUse objects
     • Continue with normal tool execution flow

3. Add provider-specific configuration in packages/types/src/providers/deepseek.ts:

   • Add xmlToolFallbackEnabled: true to DeepSeek model configs
   • This allows enabling/disabling the fallback per provider

Benefits

• Non-breaking: Only activates when native tools fail and XML patterns are detected
• Provider-specific: Can be enabled only for providers known to have this issue
• Preserves native tool calling: Doesn't change the primary flow, just adds a fallback
• Minimal code changes: Reuses existing XML parsing logic from AssistantMessageParser

Alternative Considered

Adding stronger system prompt guidance for DeepSeek was considered, but this is unreliable since model behavior varies and users may have custom system prompts.

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.

[superguo]

3.37.0 CHANGELOG says that the XML tool calling is deprecated but actually the file reading is something XML like. Can I tell Roo Code to read files by command shells as workaround?

[daniel-lxs]

Hey @superguo Try creating a new task and see if this keeps happening