feat(mcp): support conversations in custom dispatchers by gesh · Pull Request #982 · PostHog/posthog-python

gesh · 2026-09-25T14:42:36Z

Why

Custom MCP dispatchers need the same conversation and session grouping as instrumented servers. Stateless transports otherwise split related tool calls, and shared result objects must not expose one caller's conversation handle to another caller.

What changed

Add conversation schema, call, result, and capture support to PostHogMCP.
Deliver handles through structured results and tuple or list content without changing source result objects.
Keep application-owned fields, carried sessions, opt-out behavior, and failure-safe ownership rules.
Update the dispatcher guide, release note, tests, and public API snapshot.

Testing

uv run pytest --verbose --timeout=30
uv run ruff format --check .
uv run ruff check .
uv run mypy --no-site-packages --config-file mypy.ini . | uv run mypy-baseline filter
uv run make public_api_check

Created with PostHog Desktop

github-actions · 2026-09-25T14:45:49Z

posthog-python Compliance Report

Date: 2026-10-01T15:55:16.439579+00:00
Duration: 259804ms

✅ All Tests Passed!

121/121 tests passed

Capture_V1 Tests

✅ 95/95 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	518ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	511ms
Required Headers.Has Authorization Bearer Header	✅	510ms
Required Headers.Has Content Type Json	✅	511ms
Required Headers.Has Posthog Sdk Info Format	✅	511ms
Required Headers.Has Posthog Attempt Header	✅	510ms
Required Headers.Has Posthog Request Id	✅	511ms
Required Headers.Has Posthog Request Timestamp	✅	510ms
Required Headers.Has User Agent	✅	510ms
Body Format.Body Has Created At And Batch	✅	511ms
Body Format.No Api Key In Body	✅	510ms
Body Format.No Sent At In Body	✅	510ms
Event Format.Event Has Required Root Fields	✅	511ms
Event Format.Event Uuid Is Valid	✅	510ms
Event Format.Event Timestamp Is Rfc3339	✅	510ms
Event Format.Non Utc Event Timestamp Is Converted To Utc	✅	516ms
Event Format.Distinct Id Is String	✅	510ms
Event Format.Distinct Id At Root Not Properties	✅	510ms
Event Format.Custom Properties Preserved	✅	510ms
Event Format.Set Properties Preserved	✅	510ms
Event Format.Set Once Properties Preserved	✅	511ms
Event Format.Groups Properties Preserved	✅	510ms
Event Format.Sdk Generates Uuid If Not Provided	✅	510ms
Event Format.Event Has Required Root Fields Batch	✅	513ms
Event Format.Event Uuid Is Valid Batch	✅	514ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	514ms
Event Format.Distinct Id Is String Batch	✅	513ms
Event Format.Distinct Id At Root Not Properties Batch	✅	514ms
Event Format.Custom Properties Preserved Batch	✅	514ms
Event Format.Set Properties Preserved Batch	✅	514ms
Event Format.Set Once Properties Preserved Batch	✅	514ms
Event Format.Groups Properties Preserved Batch	✅	514ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	513ms
Batch Behavior.Multiple Events In Single Batch	✅	517ms
Batch Behavior.Batch Envelope Smoke	✅	516ms
Batch Behavior.Flush With No Events Sends Nothing	✅	506ms
Batch Behavior.Flush At Triggers Batch	✅	1010ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	510ms
Deduplication.Generates Unique Uuids	✅	518ms
Deduplication.Different Events Same Content Different Uuids	✅	513ms
Deduplication.Preserves Uuid On Retry	✅	6515ms
Deduplication.Preserves Timestamp On Retry	✅	6519ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	6519ms
Deduplication.No Duplicate Events In Batch	✅	519ms
Header Behavior On Retry.Attempt Header Starts At One	✅	510ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	13527ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	6516ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	3020ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	6519ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	511ms
Response Format Validation.Success Response Has Ok For Each Event	✅	515ms
Response Format Validation.Success No Retry After When All Ok	✅	513ms
Response Format Validation.Success Retry After Present When Retry Events	✅	1516ms
Response Format Validation.Success No Retry After When Drop Only	✅	512ms
Response Format Validation.Response Echoes Request Id	✅	510ms
Retry Behavior.Retries On 408	✅	6521ms
Retry Behavior.Retries On 500	✅	6519ms
Retry Behavior.Retries On 503	✅	8523ms
Retry Behavior.Retries On 504	✅	6520ms
Retry Behavior.Retryable Errors Have Retry After	✅	3517ms
Retry Behavior.Respects Retry After On Retryable Error	✅	11522ms
Retry Behavior.Does Not Retry On 400	✅	2513ms
Retry Behavior.Does Not Retry On 401	✅	2514ms
Retry Behavior.Does Not Retry On 402	✅	2513ms
Retry Behavior.Does Not Retry On 413	✅	2515ms
Retry Behavior.Does Not Retry On 415	✅	2514ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	2512ms
Retry Behavior.Implements Backoff	✅	22534ms
Retry Behavior.Max Retries Respected	✅	22534ms
Partial Batch Handling.Handles 200 Full Success	✅	2512ms
Partial Batch Handling.Handles 200 With All Ok	✅	3515ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	3517ms
Partial Batch Handling.Does Not Retry Limited Events	✅	3515ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	6521ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	6518ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	6520ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	6522ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	6517ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	6518ms
Partial Batch Handling.Respects Retry After On Partial	✅	8518ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	3514ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	3520ms
Compression.Sends Gzip Content Encoding	✅	511ms
Compression.No Content Encoding When Disabled	✅	510ms
Compression.Compressed Body Is Decompressible	✅	510ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2512ms
Event Options.Cookieless Mode Override	✅	511ms
Event Options.Disable Skew Correction Override	✅	510ms
Event Options.Process Person Profile Override	✅	510ms
Event Options.Product Tour Id Override	✅	510ms
Event Options.Unset Options Omitted	✅	510ms
Event Options.Options Override In Batch	✅	514ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	510ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	510ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	510ms

Capture_Ai Tests

✅ 5/5 tests passed

View Details

Test	Status	Duration
Routing.Capture Ai Posts To Ai Endpoint	✅	510ms
Routing.Capture Does Not Reroute Ai Named Events	✅	510ms
Identity.Capture Ai Event Has Uuid	✅	510ms
Identity.Capture Ai Keeps Supplied Uuid	✅	510ms
Timestamp Format.Non Utc Event Timestamp Is Converted To Utc	✅	511ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	11ms
Request Payload.Flags Request Uses V2 Query Param	✅	9ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	9ms
Request Payload.Flags Request Omits Authorization Header	✅	9ms
Request Payload.Token In Flags Body Matches Init	✅	10ms
Request Payload.Groups Round Trip	✅	9ms
Request Payload.Groups Default To Empty Object	✅	10ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	9ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	9ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	9ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	510ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	14ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	9ms
Retry Behavior.Retries Flags On 502	✅	313ms
Retry Behavior.Retries Flags On 504	✅	313ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	511ms

Feature_Flags_Local_Evaluation Tests

✅ 4/4 tests passed

View Details

Test	Status	Duration
Versioned Boolean Matching.Matching Version Missing	✅	69ms
Versioned Boolean Matching.Matching Version 1	✅	67ms
Versioned Boolean Matching.Matching Version 2	✅	67ms
Versioned Boolean Matching.Version Only Reload 1 2 1 2 Missing	✅	34ms

veria-ai · 2026-09-25T14:47:30Z

PR overview

All previously flagged issues have been addressed. No open security concerns remain on this pull request.

Security review

No open security issues remain on this pull request.

Fixed/addressed: 1 · PR risk: 0/10

greptile-apps · 2026-09-25T14:48:23Z

[Medium risk] Adds conversation tracking to the MCP dispatcher API.

The PR is not safe to merge until SDK-free custom dispatchers can return non-dict tool results without the MCP SDK installed.

_{Reviews (2) · Last reviewed commit: "fix(mcp): preserve conversation result i..."}

Port posthog-js#5074 to PostHogMCP. Custom dispatchers now correlate calls through an agent-carried conversation_id and a derived session id, like instrument() already does. - enable_conversation_id constructor option, on by default - prepare_tool_list() injects conversation_id and _mcp_instructions - prepare_tool_call() accepts a carried session_id and returns the resolved session_id and conversation_id - new prepare_tool_result() delivers a minted handle without mutating the original result - capture methods accept conversation_id Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

lucasheriques

The port follows @posthog/mcp closely, and the tests cover the no-mutation handling well. Approving so you're unblocked, but please fix the two blocking items before merging: both leave conversation_id in the args the handler receives, which strict validation rejects. Some points apply to JS too.

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

gesh requested a review from a team as a code owner September 25, 2026 14:42

gesh self-assigned this Sep 25, 2026

gesh removed the request for review from a team September 25, 2026 14:44

gesh marked this pull request as draft September 25, 2026 14:46

veria-ai Bot reviewed Sep 25, 2026

View reviewed changes

Comment thread posthog/mcp/posthog_mcp.py

greptile-apps Bot reviewed Sep 25, 2026

View reviewed changes

Comment thread posthog/mcp/posthog_mcp.py

Comment thread posthog/mcp/posthog_mcp.py Outdated

gesh and others added 2 commits September 30, 2026 17:27

fix(mcp): preserve conversation result isolation

d18bd52

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

gesh force-pushed the feat/mcp-dispatcher-conversations branch from 49ccde6 to d18bd52 Compare September 30, 2026 14:27

gesh marked this pull request as ready for review September 30, 2026 14:34

greptile-apps Bot reviewed Sep 30, 2026

View reviewed changes

Comment thread posthog/mcp/posthog_mcp.py Outdated

fix(mcp): keep custom results dependency-free

dddfca6

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

gesh requested review from a team October 1, 2026 14:16

gesh added reviewhog stamphog Request stamphog review labels Oct 1, 2026

lucasheriques approved these changes Oct 1, 2026

View reviewed changes

gesh added 2 commits October 1, 2026 18:49

fix(mcp): preserve dispatcher conversation ownership

a768fe8

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

Merge branch 'main' into feat/mcp-dispatcher-conversations

4053aab

Generated-By: PostHog Desktop Task-Id: 6fa508f7-af04-48ef-b7ea-31732d3ca42e

gesh merged commit 3eb3861 into main Oct 1, 2026
43 checks passed

gesh deleted the feat/mcp-dispatcher-conversations branch October 1, 2026 15:58

Navigation Menu

feat(mcp): support conversations in custom dispatchers - #982

feat(mcp): support conversations in custom dispatchers#982
gesh merged 5 commits into
mainfrom
feat/mcp-dispatcher-conversations

gesh commented Sep 25, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Sep 25, 2026 •

edited

Loading

Uh oh!

Uh oh!

veria-ai Bot commented Sep 25, 2026 •

edited

Loading

Uh oh!

greptile-apps Bot commented Sep 25, 2026 •

edited

Loading

Uh oh!

Uh oh!

Uh oh!

Uh oh!

lucasheriques left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

gesh commented Sep 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Why

What changed

Testing

Uh oh!

github-actions Bot commented Sep 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

posthog-python Compliance Report

✅ All Tests Passed!

Capture_V1 Tests

Capture_Ai Tests

Feature_Flags Tests

Feature_Flags_Local_Evaluation Tests

Uh oh!

Uh oh!

veria-ai Bot commented Sep 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

PR overview

Security review

Uh oh!

greptile-apps Bot commented Sep 25, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

lucasheriques left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

gesh commented Sep 25, 2026 •

edited

Loading

github-actions Bot commented Sep 25, 2026 •

edited

Loading

veria-ai Bot commented Sep 25, 2026 •

edited

Loading

greptile-apps Bot commented Sep 25, 2026 •

edited

Loading