Fix/reasoning close only

[chay2199]

Description

This PR fixes #

Notes for Reviewers

Signed commits

• Yes, I signed my commits.

[codity-chait]

PR Summary

What Changed

• Moved reasoning extraction from pkg/functions into a new pkg/reasoning module to separate parsing logic and make chat integration cleaner.
• Added model-aware reasoning parsing for multiple tag formats, including closing-only and unclosed tag cases, to handle more real model outputs.
• Added forced-open reasoning mode via config and prompt-suffix detection so outputs without opening tags are still parsed correctly in streaming and non-streaming paths.

Key Changes by Area

• Configuration: Added ReasoningConfig with ThinkingForcedOpen so behavior can be controlled per model.
• Chat API: Wired chat endpoint reasoning handling to the new reasoning module and config.
• Reasoning Parsing: Added Extract(...), model-specific tag support, forced-open options, and improved splitting when output starts with reasoning before a closing tag.
• Tests: Expanded coverage for nested, unclosed, empty, mismatched, special-character, and closing-only reasoning outputs.

Files Changed

File	Changes Summary
core/config/model_config.go	Added per-model reasoning config, including forced-open setting.
core/http/endpoints/openai/chat.go	Switched chat reasoning flow to use new reasoning module and config.
pkg/functions/reasoning.go	Removed or reduced old reasoning extraction logic after module move.
pkg/functions/reasoning_test.go	Updated legacy tests to reflect reasoning logic relocation.
pkg/reasoning/config.go	Added reasoning config types for module behavior control.
pkg/reasoning/options.go	Added functional options, including forced-open handling.
pkg/reasoning/reasoning.go	Implemented core extraction logic with model-specific tags and closing-only handling.
pkg/reasoning/reasoning_suite_test.go	Added test suite setup for new reasoning package.
pkg/reasoning/reasoning_test.go	Added broad coverage for tag variants, forced-open mode, and streaming-related cases.

Review Focus Areas

• Confirm behavior when content starts with reasoning and only includes a closing tag, especially split boundaries.
• Check forced-open detection and ThinkingForcedOpen precedence across prompt detection vs config.
• Verify chat endpoint behavior parity after moving logic from pkg/functions to pkg/reasoning.

Architecture

• Design Decisions: The PR isolates reasoning parsing into pkg/reasoning and makes behavior configurable per model, which reduces coupling with chat handlers and supports model-specific output formats.
• Scalability & Extensibility: Adding model-specific tags and options in one module improves reuse when new model formats are added.
• Risks: There is behavior risk around parsing edge cases in mixed content streams, especially where forced-open mode and closing-only tags interact. This looks intentional to support known model outputs but needs close verification.

[codity-chait]

With WithThinkingForcedOpen(), the post-close remainder is reparsed by extractFromTags, which treats closing-only tags as reasoning blocks. This incorrectly reclassifies normal response content as reasoning when the remainder contains a stray closing tag, and removes that content from cleanedContent. Concrete failing case: "Reasoning</think>content</thinking>more" currently returns reasoning "Reasoning\n\ncontent" instead of "Reasoning", matching the failing test in pkg/reasoning/reasoning_test.go (should find earliest closing tag).

Suggested fix

		if strings.Contains(cleanedContent, "<thinking>") ||
			strings.Contains(cleanedContent, "<think>") ||
			strings.Contains(cleanedContent, "<|START_THINKING|>") ||
			strings.Contains(cleanedContent, "<|inner_prefix|>") ||
			strings.Contains(cleanedContent, "<seed:think>") ||
			strings.Contains(cleanedContent, "[THINK]") {
			additionalReasoning, finalContent := extractFromTags(cleanedContent)
			if additionalReasoning != "" {
				if reasoning != "" {
					reasoning = reasoning + "\n\n" + additionalReasoning
				} else {
					reasoning = additionalReasoning
				}
			}
			cleanedContent = finalContent
		}

Prompt for AI assistance

Copy the prompt below and paste it into ChatGPT, Claude, or any LLM:

You are an expert bash developer with deep knowledge of security, performance, and best practices.

### Context

File: pkg/reasoning/reasoning.go
Lines: 102-110
Issue Type: functional-medium
Severity: medium

Issue Description:
With `WithThinkingForcedOpen()`, the post-close remainder is reparsed by `extractFromTags`, which treats closing-only tags as reasoning blocks. This incorrectly reclassifies normal response content as reasoning when the remainder contains a stray closing tag, and removes that content from `cleanedContent`. Concrete failing case: `"Reasoning</think>content</thinking>more"` currently returns reasoning `"Reasoning\n\ncontent"` instead of `"Reasoning"`, matching the failing test in `pkg/reasoning/reasoning_test.go` (`should find earliest closing tag`).

Current Code:
		additionalReasoning, finalContent := extractFromTags(cleanedContent)
		if additionalReasoning != "" {
			if reasoning != "" {
				reasoning = reasoning + "\n\n" + additionalReasoning
			} else {
				reasoning = additionalReasoning
			}
		}
		cleanedContent = finalContent

---

### Instructions

1. Fix the issue described above
2. Maintain the exact indentation and code style from the original
3. Follow bash best practices and language-specific idioms
4. Ensure the fix addresses the root cause, not just the symptoms
5. Add brief inline comments explaining the fix if needed

### Constraints

- Do not change functionality beyond fixing the identified issue
- Preserve existing variable names and function signatures unless they are part of the problem
- Ensure the fix is production-ready

---

[codity-chait]

License Compliance Scan

Metric	Value
Packages Scanned	334
High Risk (Strong Copyleft)	0
Medium Risk (Weak Copyleft)	4
Low Risk (Permissive)	263
Unknown License	67

Weak copyleft licenses found - verify compatibility

Some packages have unknown licenses - manual review required

Medium Risk Licenses - 4 packages

MPL-2.0 (4 packages):

• github.com/libp2p/go-yamux/v5 5.0.1
• github.com/hashicorp/golang-lru 1.0.2
• github.com/hashicorp/golang-lru/v2 2.0.7
• github.com/shoenig/go-m1cpu 0.1.6

Unknown Licenses - 67 packages

• github.com/prometheus/otlptranslator 1.0.0
• github.com/rymdport/portal 0.4.2
• github.com/srwiley/oksvg 0.0.0-20221011165216-be6e8873101c
• github.com/wlynxg/anet 0.0.5
• github.com/srwiley/rasterx 0.0.0-20220730225603-2ab79fcdd4ef
• github.com/yosida95/uritemplate/v3 3.0.2
• github.com/Masterminds/goutils 1.1.1
• github.com/Masterminds/semver/v3 3.4.0
• github.com/containerd/errdefs 1.0.0
• github.com/andybalholm/brotli 1.2.0
• github.com/alecthomas/chroma/v2 2.14.0
• github.com/beorn7/perks 1.0.1
• github.com/containerd/cgroups 1.1.0
• github.com/containerd/continuity 0.4.4
• github.com/containerd/log 0.1.0
• github.com/containerd/stargz-snapshotter/estargz 0.18.1
• github.com/creachadair/otp 0.5.0
• github.com/davidlazar/go-crypto 0.0.0-20200604182044-b73af7476f6c
• github.com/docker/cli 29.0.3+incompatible
• github.com/docker/docker 28.5.2+incompatible

...and 47 more

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