feat(ai): expose prompt config on fetched prompts

[jurajmajerik]

💡 Motivation and Context

PostHog prompt versions can now store a config object next to the prompt content (PostHog/posthog#74264): model parameters, tools, or any agent configuration, versioned with the prompt and returned by the fetch endpoint. The SDK parses API responses into typed objects, so without this change the field is fetched and then thrown away.

With this change:

result = prompts.get("summarizer", label="production", with_metadata=True)
client.chat.completions.create(
    model=(result.config or {}).get("model", "gpt-4o"),
    temperature=(result.config or {}).get("temperature", 0),
    messages=[{"role": "system", "content": result.prompt}],
)

PromptResult gains config (object or None), CachedPrompt stores it so cache hits and the stale-cache fallback keep it, and servers that don't send the field (or send an unexpected shape) read as None. The hardcoded fallback string has no config, hence the defensive access in the example.

💚 How did you test it?

Five new tests in test_prompts.py: config surviving the API fetch and a cache hit, the stale-cache path preserving it, and a parameterized matrix for responses where config is absent, null, or a non-object (all read as None). Full file (67 tests) green, ruff clean.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran sampo add to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Claude Code authored this under my direction, as the SDK follow-up to PostHog/posthog#74264. The changeset file was written manually in .sampo/changesets/ rather than via interactive sampo add. Docs for the config feature land separately on posthog.com once both SDKs support it.

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
posthog/ai/prompts.py:362
**Cached config shares mutable state**

When a caller mutates a fetched `PromptResult.config`, the shared dictionary stored in `CachedPrompt` is also modified, causing later cache-hit and stale-cache results to return caller-modified model parameters or agent configuration instead of the server-provided version.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "chore: add changeset" | Re-trigger Greptile}

[github-actions]

posthog-python Compliance Report

Date: 2026-07-30 08:53:30 UTC
Duration: 338844ms

✅ All Tests Passed!

111/111 tests passed

---

Capture_V1 Tests

✅ 94/94 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	517ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	1010ms
Required Headers.Has Authorization Bearer Header	✅	1008ms
Required Headers.Has Content Type Json	✅	1009ms
Required Headers.Has Posthog Sdk Info Format	✅	1008ms
Required Headers.Has Posthog Attempt Header	✅	1009ms
Required Headers.Has Posthog Request Id	✅	1009ms
Required Headers.Has Posthog Request Timestamp	✅	1008ms
Required Headers.Has User Agent	✅	1009ms
Body Format.Body Has Created At And Batch	✅	1008ms
Body Format.No Api Key In Body	✅	1009ms
Body Format.No Sent At In Body	✅	1009ms
Event Format.Event Has Required Root Fields	✅	1009ms
Event Format.Event Uuid Is Valid	✅	1009ms
Event Format.Event Timestamp Is Rfc3339	✅	1009ms
Event Format.Distinct Id Is String	✅	1008ms
Event Format.Distinct Id At Root Not Properties	✅	1009ms
Event Format.Custom Properties Preserved	✅	1009ms
Event Format.Set Properties Preserved	✅	1008ms
Event Format.Set Once Properties Preserved	✅	1010ms
Event Format.Groups Properties Preserved	✅	1008ms
Event Format.Sdk Generates Uuid If Not Provided	✅	1009ms
Event Format.Event Has Required Root Fields Batch	✅	1012ms
Event Format.Event Uuid Is Valid Batch	✅	1013ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	1012ms
Event Format.Distinct Id Is String Batch	✅	1012ms
Event Format.Distinct Id At Root Not Properties Batch	✅	1013ms
Event Format.Custom Properties Preserved Batch	✅	1012ms
Event Format.Set Properties Preserved Batch	✅	1013ms
Event Format.Set Once Properties Preserved Batch	✅	1012ms
Event Format.Groups Properties Preserved Batch	✅	1012ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	1012ms
Batch Behavior.Multiple Events In Single Batch	✅	1507ms
Batch Behavior.Batch Envelope Smoke	✅	1014ms
Batch Behavior.Flush With No Events Sends Nothing	✅	1005ms
Batch Behavior.Flush At Triggers Batch	✅	1508ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	1011ms
Deduplication.Generates Unique Uuids	✅	1506ms
Deduplication.Different Events Same Content Different Uuids	✅	1508ms
Deduplication.Preserves Uuid On Retry	✅	7515ms
Deduplication.Preserves Timestamp On Retry	✅	7511ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7515ms
Deduplication.No Duplicate Events In Batch	✅	1503ms
Header Behavior On Retry.Attempt Header Starts At One	✅	1010ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	14516ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	7516ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	3515ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	7510ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	1010ms
Response Format Validation.Success Response Has Ok For Each Event	✅	1506ms
Response Format Validation.Success No Retry After When All Ok	✅	1507ms
Response Format Validation.Success Retry After Present When Retry Events	✅	2510ms
Response Format Validation.Success No Retry After When Drop Only	✅	1508ms
Response Format Validation.Response Echoes Request Id	✅	1008ms
Retry Behavior.Retries On 408	✅	7511ms
Retry Behavior.Retries On 500	✅	7517ms
Retry Behavior.Retries On 503	✅	9511ms
Retry Behavior.Retries On 504	✅	7516ms
Retry Behavior.Retryable Errors Have Retry After	✅	4509ms
Retry Behavior.Respects Retry After On Retryable Error	✅	12511ms
Retry Behavior.Does Not Retry On 400	✅	3510ms
Retry Behavior.Does Not Retry On 401	✅	3507ms
Retry Behavior.Does Not Retry On 402	✅	3509ms
Retry Behavior.Does Not Retry On 413	✅	3508ms
Retry Behavior.Does Not Retry On 415	✅	3508ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	3508ms
Retry Behavior.Implements Backoff	✅	23531ms
Retry Behavior.Max Retries Respected	✅	23510ms
Partial Batch Handling.Handles 200 Full Success	✅	3012ms
Partial Batch Handling.Handles 200 With All Ok	✅	4508ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	4507ms
Partial Batch Handling.Does Not Retry Limited Events	✅	4507ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	7511ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	7516ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	7513ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	7511ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	7508ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	7516ms
Partial Batch Handling.Respects Retry After On Partial	✅	9508ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	4508ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	4511ms
Compression.Sends Gzip Content Encoding	✅	1006ms
Compression.No Content Encoding When Disabled	✅	1009ms
Compression.Compressed Body Is Decompressible	✅	1009ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	3509ms
Event Options.Cookieless Mode Override	✅	1007ms
Event Options.Disable Skew Correction Override	✅	1009ms
Event Options.Process Person Profile Override	✅	1008ms
Event Options.Product Tour Id Override	✅	1009ms
Event Options.Unset Options Omitted	✅	1009ms
Event Options.Options Override In Batch	✅	1012ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	1009ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	1009ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	1009ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1007ms
Request Payload.Flags Request Uses V2 Query Param	✅	1006ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1007ms
Request Payload.Flags Request Omits Authorization Header	✅	1007ms
Request Payload.Token In Flags Body Matches Init	✅	1006ms
Request Payload.Groups Round Trip	✅	1007ms
Request Payload.Groups Default To Empty Object	✅	1007ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1007ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1006ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1008ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1011ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1002ms
Retry Behavior.Retries Flags On 502	✅	1007ms
Retry Behavior.Retries Flags On 504	✅	1007ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1509ms