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feat(mcp): capture server build metadata - #990

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gesh merged 3 commits into
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posthog/mcp-server-build
Sep 30, 2026
Merged

feat(mcp): capture server build metadata#990
gesh merged 3 commits into
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posthog/mcp-server-build

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@gesh

@gesh gesh commented Sep 29, 2026 •
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💡 Motivation and Context

MCP server owners need to connect events to the exact code that handled each request. MCP server metadata only identifies the release version.

This PR ports server_build from @posthog/mcp 0.21.0. Automatic instrumentation and custom dispatchers record the value as $mcp_server_build on all MCP events.

PostHogMCP.capture() also adds the configured value to custom events. An event-specific value takes precedence over the configured value.

from posthog.mcp import MCPAnalyticsOptions, instrument

instrument(
    server,
    posthog,
    MCPAnalyticsOptions(server_build="git-sha-or-image-digest"),
)

💚 How did you test it?

  • uv run pytest -q posthog/test/mcp --timeout=30
  • uv run ruff check posthog/mcp posthog/test/mcp/test_posthog_mcp.py posthog/test/mcp/test_features_m4.py
  • uv run mypy --no-site-packages --config-file mypy.ini posthog/mcp | uv run mypy-baseline filter
  • make public_api_check

📝 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)

Codex implemented the agreed Python port. The implementation validates the value during setup and applies it to exception events.

Created with PostHog Desktop

@gesh
feat(mcp): capture server build metadata
16f4a55 
Generated-By: PostHog Desktop
Task-Id: dda38523-5b8d-47b6-a11a-64cd59a812fe
@gesh gesh self-assigned this Sep 29, 2026
@github-actions

github-actions Bot commented Sep 29, 2026 •
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posthog-python Compliance Report

Date: 2026-09-30T14:13:07.473495+00:00
Duration: 260002ms

✅ 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 ✅ 519ms
Endpoint And Method.Does Not Use Legacy Endpoints ✅ 511ms
Required Headers.Has Authorization Bearer Header ✅ 511ms
Required Headers.Has Content Type Json ✅ 513ms
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 ✅ 511ms
Body Format.Body Has Created At And Batch ✅ 511ms
Body Format.No Api Key In Body ✅ 510ms
Body Format.No Sent At In Body ✅ 511ms
Event Format.Event Has Required Root Fields ✅ 511ms
Event Format.Event Uuid Is Valid ✅ 511ms
Event Format.Event Timestamp Is Rfc3339 ✅ 511ms
Event Format.Non Utc Event Timestamp Is Converted To Utc ✅ 516ms
Event Format.Distinct Id Is String ✅ 511ms
Event Format.Distinct Id At Root Not Properties ✅ 510ms
Event Format.Custom Properties Preserved ✅ 511ms
Event Format.Set Properties Preserved ✅ 510ms
Event Format.Set Once Properties Preserved ✅ 510ms
Event Format.Groups Properties Preserved ✅ 511ms
Event Format.Sdk Generates Uuid If Not Provided ✅ 511ms
Event Format.Event Has Required Root Fields Batch ✅ 514ms
Event Format.Event Uuid Is Valid Batch ✅ 514ms
Event Format.Event Timestamp Is Rfc3339 Batch ✅ 517ms
Event Format.Distinct Id Is String Batch ✅ 515ms
Event Format.Distinct Id At Root Not Properties Batch ✅ 515ms
Event Format.Custom Properties Preserved Batch ✅ 515ms
Event Format.Set Properties Preserved Batch ✅ 515ms
Event Format.Set Once Properties Preserved Batch ✅ 513ms
Event Format.Groups Properties Preserved Batch ✅ 515ms
Event Format.Sdk Generates Uuid If Not Provided Batch ✅ 520ms
Batch Behavior.Multiple Events In Single Batch ✅ 518ms
Batch Behavior.Batch Envelope Smoke ✅ 516ms
Batch Behavior.Flush With No Events Sends Nothing ✅ 508ms
Batch Behavior.Flush At Triggers Batch ✅ 1011ms
Batch Behavior.Created At Reflects Batch Creation Time ✅ 512ms
Deduplication.Generates Unique Uuids ✅ 517ms
Deduplication.Different Events Same Content Different Uuids ✅ 512ms
Deduplication.Preserves Uuid On Retry ✅ 6520ms
Deduplication.Preserves Timestamp On Retry ✅ 6517ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry ✅ 6524ms
Deduplication.No Duplicate Events In Batch ✅ 520ms
Header Behavior On Retry.Attempt Header Starts At One ✅ 511ms
Header Behavior On Retry.Attempt Header Increments On Retry ✅ 13523ms
Header Behavior On Retry.Request Id Preserved On Retry ✅ 6520ms
Header Behavior On Retry.Different Requests Have Different Request Ids ✅ 3020ms
Header Behavior On Retry.Request Timestamp Changes On Retry ✅ 6521ms
Response Format Validation.Success Response Has Uuid Keyed Results ✅ 512ms
Response Format Validation.Success Response Has Ok For Each Event ✅ 514ms
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 ✅ 512ms
Retry Behavior.Retries On 408 ✅ 6520ms
Retry Behavior.Retries On 500 ✅ 6520ms
Retry Behavior.Retries On 503 ✅ 8524ms
Retry Behavior.Retries On 504 ✅ 6517ms
Retry Behavior.Retryable Errors Have Retry After ✅ 3517ms
Retry Behavior.Respects Retry After On Retryable Error ✅ 11525ms
Retry Behavior.Does Not Retry On 400 ✅ 2514ms
Retry Behavior.Does Not Retry On 401 ✅ 2514ms
Retry Behavior.Does Not Retry On 402 ✅ 2514ms
Retry Behavior.Does Not Retry On 413 ✅ 2514ms
Retry Behavior.Does Not Retry On 415 ✅ 2514ms
Retry Behavior.Non Retryable Errors Have No Retry After ✅ 2513ms
Retry Behavior.Implements Backoff ✅ 22526ms
Retry Behavior.Max Retries Respected ✅ 22531ms
Partial Batch Handling.Handles 200 Full Success ✅ 2513ms
Partial Batch Handling.Handles 200 With All Ok ✅ 3518ms
Partial Batch Handling.Does Not Retry Dropped Events ✅ 3517ms
Partial Batch Handling.Does Not Retry Limited Events ✅ 3516ms
Partial Batch Handling.Prunes Ok Events On Partial Retry ✅ 6521ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry ✅ 6522ms
Partial Batch Handling.Retries Only Retry Events From Partial ✅ 6519ms
Partial Batch Handling.Partial Retry Preserves Uuids ✅ 6523ms
Partial Batch Handling.Partial Retry Attempt Header Increments ✅ 6522ms
Partial Batch Handling.Partial Retry Request Id Preserved ✅ 6518ms
Partial Batch Handling.Respects Retry After On Partial ✅ 8517ms
Partial Batch Handling.Unknown Result Treated As Terminal ✅ 3517ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry ✅ 3521ms
Compression.Sends Gzip Content Encoding ✅ 511ms
Compression.No Content Encoding When Disabled ✅ 510ms
Compression.Compressed Body Is Decompressible ✅ 511ms
Error Handling.Does Not Retry On Unknown 4Xx ✅ 2514ms
Event Options.Cookieless Mode Override ✅ 511ms
Event Options.Disable Skew Correction Override ✅ 511ms
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 ✅ 511ms
Geoip And Historical Migration.Historical Migration Set In Body ✅ 510ms
Geoip And Historical Migration.Historical Migration Absent By Default ✅ 511ms

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 ✅ 511ms
Identity.Capture Ai Event Has Uuid ✅ 511ms
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 ✅ 10ms
Request Payload.Flags Request Hits Flags Path Not Decide ✅ 9ms
Request Payload.Flags Request Omits Authorization Header ✅ 12ms
Request Payload.Token In Flags Body Matches Init ✅ 10ms
Request Payload.Groups Round Trip ✅ 10ms
Request Payload.Groups Default To Empty Object ✅ 9ms
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 ✅ 11ms
Request Lifecycle.No Flags Request On Init Alone ✅ 4ms
Request Lifecycle.No Flags Request On Normal Capture ✅ 510ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests ✅ 17ms
Request Lifecycle.Mock Response Value Is Returned To Caller ✅ 11ms
Retry Behavior.Retries Flags On 502 ✅ 314ms
Retry Behavior.Retries Flags On 504 ✅ 314ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event ✅ 514ms

Feature_Flags_Local_Evaluation Tests

✅ 4/4 tests passed

View Details
Test Status Duration
Versioned Boolean Matching.Matching Version Missing ✅ 85ms
Versioned Boolean Matching.Matching Version 1 ✅ 71ms
Versioned Boolean Matching.Matching Version 2 ✅ 74ms
Versioned Boolean Matching.Version Only Reload 1 2 1 2 Missing ✅ 42ms

@greptile-apps

greptile-apps Bot commented Sep 29, 2026 •
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Retrigger

[Medium risk] Adds optional deployment identifier to MCP analytics events.

The PR appears safe to merge.

Reviews (2) · Last reviewed commit: "fix(mcp): preserve validated server buil..."

greptile-apps[bot]
greptile-apps Bot reviewed Sep 29, 2026
View reviewed changes
Comment thread posthog/mcp/_posthog_events.py Resolved
Comment thread posthog/mcp/_capture.py Resolved
Comment thread posthog/mcp/_server_build.py Resolved
@gesh
fix(mcp): preserve validated server build
a876895 
Generated-By: PostHog Desktop
Task-Id: dda38523-5b8d-47b6-a11a-64cd59a812fe
@gesh
gesh marked this pull request as ready for review September 29, 2026 13:08
@gesh
gesh requested a review from a team as a code owner September 29, 2026 13:08
@gesh
gesh requested a review from a team September 29, 2026 13:08
@gesh gesh added posthog-review stamphog Request stamphog review labels Sep 29, 2026
dustinbyrne
dustinbyrne approved these changes Sep 29, 2026
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Reviewed both MCP entry paths, validated build snapshots, exception-event attribution, truncation and final privacy hooks. The earlier review findings are addressed. No issues found.

Validation: static source review and existing CI; no tests or device runs executed for this review.

Human-driven, agent-assisted review.

@gesh
fix(mcp): add server build to custom events
b0fd2be 
Generated-By: PostHog Desktop
Task-Id: dda38523-5b8d-47b6-a11a-64cd59a812fe
@gesh
gesh merged commit 299906b into main Sep 30, 2026
44 checks passed
@gesh
gesh deleted the posthog/mcp-server-build branch September 30, 2026 14:18
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