fix(python): add org_id to prompt cache key for cross-org isolation

[colinbennettbrain]

Summary

• Fixes cross-org prompt cache collision bug (Pylon case #10589)
• Adds org_id to cache key format for proper organization isolation
• Adds tests for cross-org cache behavior

Problem

The prompt cache was using a key format of {project_name}:{slug}:{version} which did not include the organization ID. This caused a cross-org cache collision bug where two organizations with the same project name and prompt slug could retrieve each other's cached prompts.

This was reported by HubSpot where a UI-based Python scorer returned a "legal-related prompt" instead of their SDC coverage prompt because the disk cache (~/.braintrust/prompt_cache) returned a prompt from a different org that had been previously cached on the same scorer runtime.

Root Cause

In prompt_cache.py:17-34, the _create_cache_key() function was:

def _create_cache_key(project_id, project_name, slug, version="latest", id=None):
    if id:
        return f"id:{id}"
    prefix = project_id or project_name
    return f"{prefix}:{slug}:{version}"  # No org_id!

When project_name is used (common in scorers), two different organizations with the same project name and prompt slug would have the same cache key, causing cache collisions.

Solution

• Add org_id parameter to _create_cache_key()
• Update cache key format to {org_id}:{prefix}:{slug}:{version} when org_id is available
• Thread org_id through PromptCache.get() and PromptCache.set()
• Pass _state.org_id from load_prompt() to cache operations

Test plan

• Added test_handle_different_orgs_with_same_project_and_slug - verifies prompts from different orgs with same project/slug are isolated
• Added test_org_id_isolation_with_disk_cache - verifies isolation works after memory eviction (via disk cache)
• All 15 prompt cache tests pass

Backward Compatibility

The fix is backward compatible:

• Existing cached prompts without org_id in the key will simply miss and trigger a fresh API fetch
• The org_id parameter is optional and defaults to None
• No breaking changes to the public API

🤖 Generated with Claude Code

[colinbennettbrain]

Hey Olmo, this came up because a customer realized the wrong prompt was getting sent to OpenAI. I am attempting to fix the issue with this. I also have a repro script if that's helpful.

[clutchski]

if org_id is required to prevent cross org issues, it should be required (e.g. not none)

[clutchski]

i think the org_id can always be in the cache key