---
id: T02
parent: S02
milestone: M003
provides: []
requires: []
affects: []
key_files: ["backend/pipeline/llm_client.py"]
key_decisions: ["strip_think_tags uses re.DOTALL regex for multiline support", "Thinking modality appends JSON instructions to system prompt instead of using response_format", "INFO log on every LLM request shows model, modality, and response_model"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "strip_think_tags passes all 5 test cases"
completed_at: 2026-03-30T01:47:59.356Z
blocker_discovered: false
---

# T02: LLMClient now supports chat/thinking modality with model override and think-tag stripping

> LLMClient now supports chat/thinking modality with model override and think-tag stripping

## What Happened
---
id: T02
parent: S02
milestone: M003
key_files:
  - backend/pipeline/llm_client.py
key_decisions:
  - strip_think_tags uses re.DOTALL regex for multiline support
  - Thinking modality appends JSON instructions to system prompt instead of using response_format
  - INFO log on every LLM request shows model, modality, and response_model
duration: ""
verification_result: passed
completed_at: 2026-03-30T01:47:59.356Z
blocker_discovered: false
---

# T02: LLMClient now supports chat/thinking modality with model override and think-tag stripping

**LLMClient now supports chat/thinking modality with model override and think-tag stripping**

## What Happened

Rewrote LLMClient.complete() to accept modality ('chat'/'thinking') and model_override parameters. Chat modality preserves current behavior (response_format json_object). Thinking modality skips response_format, appends JSON instructions to system prompt, and strips <think>...</think> blocks from output. Added strip_think_tags() utility with regex-based stripping. All 5 test cases pass (single block, multiline, multiple blocks, no tags, empty).

## Verification

strip_think_tags passes all 5 test cases

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `cd backend && python3 -c "from pipeline.llm_client import strip_think_tags; ...assert tests..."` | 0 | ✅ pass — ALL PASS | 250ms |


## Deviations

None.

## Known Issues

None.

## Files Created/Modified

- `backend/pipeline/llm_client.py`


## Deviations
None.

## Known Issues
None.
