feat: Support HTTP in MCP by Anarion-zuo · Pull Request #6109 · feast-dev/feast

Anarion-zuo · 2026-03-15T13:07:52Z

What this PR does / why we need it:

This PR adds first-class support for Streamable HTTP MCP transport in the Feast Python Feature Server to address reliability issues with the legacy SSE-based MCP endpoint and eliminate the need for external proxies in common MCP clients.

Key changes:

Adds mcp_transport configuration for MCP feature server ( sse | http ), defaulting to sse for backwards compatibility.
When mcp_transport=http , mounts MCP using Streamable HTTP via FastApiMCP.mount_http() .
When mcp_transport=sse , preserves existing behavior, preferring mount_sse() when available (fallback to deprecated mount() for older fastapi_mcp versions).
Fails fast with a clear error when mcp_transport=http is configured but the installed fastapi_mcp version does not support mount_http() .
Adds/updates unit + integration tests covering transport selection and failure modes.
Updates docs and example configuration to show how to enable Streamable HTTP and avoid the GET /mcp 406 by using the correct Accept header.
Touched areas:
MCP config + mounting logic: mcp_config.py , mcp_server.py , feature_server.py
Tests: test_mcp_server.py , test_mcp_feature_server.py
Docs/examples: genai.md , mcp-feature-server.md , feature_store.yaml

Which issue(s) this PR fixes:

Fixes #5853.

Misc

Tests run locally:

pytest sdk/python/tests/unit/infra/feature_servers/test_mcp_server.py
pytest sdk/python/tests/integration/test_mcp_feature_server.py
Notes:
Default remains mcp_transport: sse to avoid behavior changes for existing deployments.
For Streamable HTTP, a plain GET /mcp may return 406 unless the client includes Accept: text/event-stream (expected by the transport).

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 3 additional findings.

franciscojavierarceo · 2026-03-16T14:21:18Z

.github/workflows/unit_tests.yml

      - name: Minimize uv cache
        run: uv cache prune --ci

+  mcp-feature-server-runtime:


this should go in integration tests please

Is it this one? .github/workflows/pr_integration_tests.yml

franciscojavierarceo · 2026-03-16T14:22:15Z

sdk/python/feast/ui_server.py

    tls_key_path: str = "",
    tls_cert_path: str = "",
 ):
+    import uvicorn


why move this here?

No need to import this if start_server is not called. But this is not essential. Will move it to the top.

franciscojavierarceo

overall this lgtm with two minor nits, thanks for doing this!

Anarion-zuo · 2026-03-17T08:24:45Z

Resolved your comments. @franciscojavierarceo

Anarion-zuo · 2026-03-17T14:13:58Z

@franciscojavierarceo Perhaps we can merge this one?

franciscojavierarceo

this lgtm, let's wait for @YassinNouh21 to review

YassinNouh21 · 2026-03-17T15:17:47Z

sdk/python/feast/feature_server.py

+                )
+
+                mcp_transport_not_supported_error = McpTransportNotSupportedError
+            except Exception as e:


except Exception here catches SyntaxError, AttributeError, etc. — not just a missing package. Use except ImportError so real bugs in mcp_server.py are not silently swallowed. @franciscojavierarceo worth fixing before merge.

cc: @franciscojavierarceo

YassinNouh21 · 2026-03-17T15:17:59Z

sdk/python/feast/infra/mcp_servers/mcp_server.py

-        # Mount the MCP server to the FastAPI app
-        mcp.mount()
+        transport: Literal["sse", "http"] = (
+            getattr(config, "mcp_transport", "sse") or "sse"


or "sse" handles None but mcp_transport is now Literal["sse", "http"] so None is impossible. Can simplify to getattr(config, "mcp_transport", "sse").

sdk/python/feast/infra/mcp_servers/mcp_server.py

YassinNouh21 · 2026-03-17T15:18:23Z

sdk/python/feast/infra/mcp_servers/mcp_server.py

+            else:
+                mcp.mount()
+        else:
+            raise McpTransportNotSupportedError(


This branch is unreachable — Literal["sse", "http"] in the config rejects anything else at parse time. Either remove it or add a comment that it's a defensive guard for programmatic callers.

@Anarion-zuo u didn't solve it btw :)

@Anarion-zuo any update on this one?

Sorry. Missed this one. Will look at it ASAP.

@YassinNouh21 Made some changes. Is this aligned with what you intended?

YassinNouh21 · 2026-03-17T15:18:35Z

sdk/python/feast/infra/mcp_servers/mcp_server.py

+    except McpTransportNotSupportedError:
+        raise
    except Exception as e:
        logger.error(f"Failed to initialize MCP integration: {e}")


Missing exc_info=True — loses the traceback. Without it, debugging a broken init means guessing from just the exception message string.

YassinNouh21 · 2026-03-17T15:18:48Z

.github/workflows/pr_integration_tests.yml

+            -H "Content-Type: application/json" \
+            -H "mcp-protocol-version: 2025-03-26" \
+            --data '{}' \
+            http://127.0.0.1:6566/mcp || true


|| true swallows connection failures. If the server crashed or is unreachable, curl exits non-zero but the step continues and later grep on a missing/empty file gives a confusing error. Remove || true and let curl fail the step directly.

.github/workflows/pr_integration_tests.yml

Anarion-zuo · 2026-03-17T15:45:50Z

Addressed all of the reviews. Waiting for CI to go green.

Anarion-zuo · 2026-03-18T03:41:11Z

@franciscojavierarceo @YassinNouh21 It's green now.

Anarion-zuo · 2026-03-21T06:21:07Z

@franciscojavierarceo @YassinNouh21 gentle ping

YassinNouh21 · 2026-03-30T12:15:14Z

@Anarion-zuo gentle bump — verified the latest push and these 3 are still unresolved:

mcp_server.py:51 — drop the redundant or "sse" (type is Literal["sse","http"], can't be None)
mcp_server.py:68-70 — remove the unreachable else branch or add a # defensive guard for programmatic callers comment
pr_integration_tests.yml:163 — remove || true on the second curl; -sS already exits 0 on HTTP 4xx, so it only masks connection failures

Anarion-zuo · 2026-04-01T17:19:52Z

@YassinNouh21 pushed some code yesterday. Please review.

Anarion-zuo · 2026-04-04T06:48:42Z

@YassinNouh21 @franciscojavierarceo gentle ping

YassinNouh21

LGTM

Signed-off-by: aaronzuo <[email protected]>

# [0.61.0](v0.60.0...v0.61.0) (2026-04-07) ### Bug Fixes * Add grpcio dependency group to transformation server Dockerfile ([2c2150a](2c2150a)) * Add https readiness check for rest-registry tests ([ea85e63](ea85e63)) * Add website build check for PRs and fix blog frontmatter YAML error ([#6079](#6079)) ([30a3a43](30a3a43)) * Added missing jackc/pgx/v5 entries ([94ad0e7](94ad0e7)) * Added MLflow metric charts across feature selection ([#6080](#6080)) ([a403361](a403361)) * Check duplicate names for feature view across types ([#5999](#5999)) ([95b9af8](95b9af8)) * Fix integration tests ([#6046](#6046)) ([02d5548](02d5548)) * Fix missing error handling for resource_counts endpoint ([d9706ce](d9706ce)) * Fix non-specific label selector on metrics service ([a1a160d](a1a160d)) * fix path feature_definitions.py ([7d7df68](7d7df68)) * Fix regstry Rest API tests intermittent failure ([d53a339](d53a339)) * Fixed IntegrityError on SqlRegistry ([#6047](#6047)) ([325e148](325e148)) * Fixed intermittent failures in get_historical_features ([c335ec7](c335ec7)) * Fixed pre-commit check ([114b7db](114b7db)) * Fixed the intermittent FeatureViewNotFoundException ([661ecc7](661ecc7)) * Fixed uv cache permission error for docker build on mac ([ad807be](ad807be)) * Fixes a `PydanticDeprecatedSince20` warning for trino_offline_store ([#5991](#5991)) ([abfd18a](abfd18a)) * Handle existing RBAC role gracefully in namespace registry ([b46a62b](b46a62b)) * Ignore ipynb files during apply ([#6151](#6151)) ([4ea123d](4ea123d)) * Integration test failures ([#6040](#6040)) ([9165870](9165870)) * Mount TLS volumes for init container ([080a9b5](080a9b5)) * **postgres:** Use end_date in synthetic entity_df for non-entity retrieval ([#6110](#6110)) ([088a802](088a802)), closes [#6066](#6066) * Ray offline store tests are duplicated across 3 workflows ([54f705a](54f705a)) * Reenable tests ([#6036](#6036)) ([82ee7f8](82ee7f8)) * SSL/TLS mode by default for postgres connection ([4844488](4844488)) * Use commitlint pre-commit hook instead of a separate action ([35a81e7](35a81e7)) ### Features * Add Claude Code agent skills for Feast ([#6081](#6081)) ([1e5b60f](1e5b60f)), closes [#5976](#5976) [#6007](#6007) * Add complex type support (Map, JSON, Struct) with schema validation ([#5974](#5974)) ([1200dbf](1200dbf)) * Add decimal to supported feature types ([#6029](#6029)) ([#6226](#6226)) ([cff6fbf](cff6fbf)) * Add feast apply init container to automate registry population on pod start ([#6106](#6106)) ([6b31a43](6b31a43)) * Add feature view versioning support to PostgreSQL and MySQL online stores ([#6193](#6193)) ([940e0f0](940e0f0)), closes [#6168](#6168) [#6169](#6169) [#2728](#2728) * Add materialization, feature freshness, request latency, and push metrics to feature server ([2c6be18](2c6be18)) * Add metadata statistics to registry api ([ef1d4fc](ef1d4fc)) * Add non-entity retrieval support for ClickHouse offline store ([4d08ddc](4d08ddc)), closes [#5835](#5835) * Add OnlineStore for MongoDB ([#6025](#6025)) ([bf4e3fa](bf4e3fa)), closes [golang/go#74462](golang/go#74462) * Add Oracle DB as Offline store in python sdk & operator ([#6017](#6017)) ([9d35368](9d35368)) * Add RBAC aggregation labels to FeatureStore ClusterRoles ([daf77c6](daf77c6)) * Add ServiceMonitor auto-generation for Prometheus discovery ([#6126](#6126)) ([56e6d21](56e6d21)) * Add typed_features field to grpc write request (([#6117](#6117)) ([#6118](#6118)) ([eeaa6db](eeaa6db)), closes [#6116](#6116) * Add UUID and TIME_UUID as feature types ([#5885](#5885)) ([#5951](#5951)) ([5d6e311](5d6e311)) * Add version indicators to lineage graph nodes ([#6187](#6187)) ([73805d3](73805d3)) * Add version tracking to FeatureView ([#6101](#6101)) ([ed4a4f2](ed4a4f2)) * Added Agent skills for AI Agents ([#6007](#6007)) ([99008c8](99008c8)) * Added CodeQL SAST scanning and detect-secrets pre-commit hook ([547b516](547b516)) * Added odfv transformations metrics ([8b5a526](8b5a526)) * Adding optional name to Aggregation (feast-dev[#5994](#5994)) ([#6083](#6083)) ([56469f7](56469f7)) * Created DocEmbedder class ([#5973](#5973)) ([0719c06](0719c06)) * Extended OIDC support to extract groups & namespaces and token injection with multiple methods ([#6089](#6089)) ([7c04026](7c04026)) * Feature Server High-Availability on Kubernetes ([#6028](#6028)) ([9c07b4c](9c07b4c)), closes [Hi#Availability](https://github.com/Hi/issues/Availability) [Hi#Availability](https://github.com/Hi/issues/Availability) * **go:** Implement metrics and tracing for http and grpc servers ([#5925](#5925)) ([2b4ec9a](2b4ec9a)) * Horizontal scaling support to the Feast operator ([#6000](#6000)) ([3ec13e6](3ec13e6)) * Making feature view source optional (feast-dev[#6074](#6074)) ([#6075](#6075)) ([76917b7](76917b7)) * Replace ORJSONResponse with Pydantic response models for faster JSON serialization ([65cf03c](65cf03c)) * Support arm docker build ([#6061](#6061)) ([1e1f5d9](1e1f5d9)) * Support distinct count aggregation [[#6116](#6116)] ([3639570](3639570)) * Support HTTP in MCP ([#6109](#6109)) ([e72b983](e72b983)) * Support nested collection types (Array/Set of Array/Set) ([#5947](#5947)) ([#6132](#6132)) ([ab61642](ab61642)) * Support podAnnotations on Deployment pod template ([1b3cdc1](1b3cdc1)) * Use orjson for faster JSON serialization in feature server ([6f5203a](6f5203a)) * Utilize date partition column in BigQuery ([#6076](#6076)) ([4ea9b32](4ea9b32)) ### Performance Improvements * Online feature response construction in a single pass over read rows ([113fb04](113fb04)) * Optimize protobuf parsing in Redis online store ([#6023](#6023)) ([59dfdb8](59dfdb8)) * Optimize timestamp conversion in _convert_rows_to_protobuf ([33a2e95](33a2e95)) * Parallelize DynamoDB batch reads in sync online_read ([#6024](#6024)) ([9699944](9699944)) * Remove redundant entity key serialization in online_read ([d87283f](d87283f))

# [0.62.0](v0.61.0...v0.62.0) (2026-04-08) ### Bug Fixes * Added missing jackc/pgx/v5 entries ([94ad0e7](94ad0e7)) * Fix missing error handling for resource_counts endpoint ([d9706ce](d9706ce)) * fix path feature_definitions.py ([7d7df68](7d7df68)) * Fix regstry Rest API tests intermittent failure ([d53a339](d53a339)) * Fixed intermittent failures in get_historical_features ([c335ec7](c335ec7)) * Fixed the intermittent FeatureViewNotFoundException ([661ecc7](661ecc7)) * Handle existing RBAC role gracefully in namespace registry ([b46a62b](b46a62b)) * Ignore ipynb files during apply ([#6151](#6151)) ([4ea123d](4ea123d)) * Mount TLS volumes for init container ([080a9b5](080a9b5)) * **postgres:** Use end_date in synthetic entity_df for non-entity retrieval ([#6110](#6110)) ([088a802](088a802)), closes [#6066](#6066) * SSL/TLS mode by default for postgres connection ([4844488](4844488)) * Sync v0.61-branch so v0.61.0 tag is reachable from master ([af66878](af66878)) ### Features * Add Claude Code agent skills for Feast ([#6081](#6081)) ([1e5b60f](1e5b60f)), closes [#5976](#5976) [#6007](#6007) * Add decimal to supported feature types ([#6029](#6029)) ([#6226](#6226)) ([cff6fbf](cff6fbf)) * Add feast apply init container to automate registry population on pod start ([#6106](#6106)) ([6b31a43](6b31a43)) * Add feature view versioning support to PostgreSQL and MySQL online stores ([#6193](#6193)) ([940e0f0](940e0f0)), closes [#6168](#6168) [#6169](#6169) [#2728](#2728) * Add metadata statistics to registry api ([ef1d4fc](ef1d4fc)) * Add Oracle DB as Offline store in python sdk & operator ([#6017](#6017)) ([9d35368](9d35368)) * Add RBAC aggregation labels to FeatureStore ClusterRoles ([daf77c6](daf77c6)) * Add ServiceMonitor auto-generation for Prometheus discovery ([#6126](#6126)) ([56e6d21](56e6d21)) * Add typed_features field to grpc write request (([#6117](#6117)) ([#6118](#6118)) ([eeaa6db](eeaa6db)), closes [#6116](#6116) * Add UUID and TIME_UUID as feature types ([#5885](#5885)) ([#5951](#5951)) ([5d6e311](5d6e311)) * Add version indicators to lineage graph nodes ([#6187](#6187)) ([73805d3](73805d3)) * Add version tracking to FeatureView ([#6101](#6101)) ([ed4a4f2](ed4a4f2)) * Added Agent skills for AI Agents ([#6007](#6007)) ([99008c8](99008c8)) * Added odfv transformations metrics ([8b5a526](8b5a526)) * Created DocEmbedder class ([#5973](#5973)) ([0719c06](0719c06)) * Extended OIDC support to extract groups & namespaces and token injection with multiple methods ([#6089](#6089)) ([7c04026](7c04026)) * Replace ORJSONResponse with Pydantic response models for faster JSON serialization ([65cf03c](65cf03c)) * Support distinct count aggregation [[#6116](#6116)] ([3639570](3639570)) * Support HTTP in MCP ([#6109](#6109)) ([e72b983](e72b983)) * Support nested collection types (Array/Set of Array/Set) ([#5947](#5947)) ([#6132](#6132)) ([ab61642](ab61642)) * Support podAnnotations on Deployment pod template ([1b3cdc1](1b3cdc1)) * Utilize date partition column in BigQuery ([#6076](#6076)) ([4ea9b32](4ea9b32)) ### Performance Improvements * Online feature response construction in a single pass over read rows ([113fb04](113fb04))

Anarion-zuo requested a review from a team as a code owner March 15, 2026 13:07

Anarion-zuo mentioned this pull request Mar 15, 2026

Support Streamable HTTP transport for Feature Server MCP integration #5853

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franciscojavierarceo requested a review from YassinNouh21 March 17, 2026 14:25

franciscojavierarceo approved these changes Mar 17, 2026

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YassinNouh21 approved these changes Apr 5, 2026

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Anarion-zuo added 2 commits April 5, 2026 20:22

feat: Support HTTP in MCP

fc7974c

Signed-off-by: aaronzuo <[email protected]>

dev

3b517b2

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Anarion-zuo added 11 commits April 5, 2026 20:22

format

e69098e

Signed-off-by: aaronzuo <[email protected]>

fix

2725f43

Signed-off-by: aaronzuo <[email protected]>

fix

82bb408

Signed-off-by: aaronzuo <[email protected]>

fix

26a01a2

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dev

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fix

58cddeb

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fix reviews

face1ed

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fix logger

f9dec18

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fix logger test

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fix comment

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resolve comments

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ntkathole force-pushed the aaronzuo/mcp_http_config branch from da3aacf to ea6358f Compare April 5, 2026 14:52

ntkathole added the ok-to-test label Apr 5, 2026

ntkathole merged commit e72b983 into feast-dev:master Apr 5, 2026
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