fix(prompt-cache): align default key with production semantics

[kxzk]

Summary

• Default prompt cache key now appends :production when neither version nor label is specified, aligning with JS/Python SDK semantics.
• Corrected docs/PROMPTS.md which incorrectly described the default fetch behavior as "latest" — it actually resolves to the production-labeled prompt.

Test plan

• bundle exec rspec — 1198 examples, 0 failures, 98.06% coverage
• bundle exec rubocop — no offenses

[greptile-apps]

Greptile Summary

Updated prompt cache key generation to default unlabeled/unversioned fetches to name:production format, aligning with Langfuse JS/Python SDK semantics.

Key changes:

• Modified PromptCache.build_key to append :production when both version and label are nil
• Correctly maintains existing behavior for explicit version/label parameters
• Updated all test expectations across cache, API client, and Rails adapter specs
• Added CHANGELOG entry documenting the breaking change

Validation:

• All 1154 tests passing with 98.04% coverage
• No Rubocop offenses
• Langfuse CLI contract verified per PR description

Confidence Score: 5/5

• Safe to merge - straightforward cache key format change with comprehensive test coverage
• Single-line logic change with clear intent, all tests updated consistently, validates against Langfuse API contract, and maintains backward compatibility for explicit version/label usage
• No files require special attention

Important Files Changed

Filename	Overview
lib/langfuse/prompt_cache.rb	Added :production suffix to cache keys when no version/label specified, aligning with API default behavior
spec/langfuse/prompt_cache_spec.rb	Updated test expectations for build_key to expect :production suffix on unlabeled prompts
spec/langfuse/api_client_spec.rb	Updated cache key expectations throughout API client integration tests to use :production suffix

_{Last reviewed commit: 7a4cbb1}

[Copilot]

Pull request overview

This PR updates the default prompt cache key generation behavior to align with JavaScript and Python SDK semantics. When fetching prompts without specifying a version or label, the cache key now defaults to name:production instead of just name, ensuring consistency across Langfuse SDKs.

Changes:

• Modified PromptCache.build_key to append :production suffix when both version and label are nil
• Updated all test expectations across prompt cache, Rails cache adapter, and API client specs to reflect the new default behavior
• Added unreleased changelog entry documenting the change and cross-SDK alignment

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lib/langfuse/prompt_cache.rb	Core implementation: adds :production suffix to cache keys when version and label are unspecified
spec/langfuse/prompt_cache_spec.rb	Updated test expectations for name-only cache key generation
spec/langfuse/rails_cache_adapter_spec.rb	Updated test expectations for Rails cache adapter key building
spec/langfuse/api_client_spec.rb	Updated mock expectations to use :production suffix in cache key assertions
CHANGELOG.md	Documented the semantic change in the unreleased section

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.