Remove Forwarding Methods & Fix SSE Parsing by kevalmahajan · Pull Request #2647 · IBM/mcp-context-forge

kevalmahajan · 2026-02-02T11:08:53Z

🐛 Bug-fix PR

Closes #1595

📌 Summary

Addressed two distinct items:

Federation Cleanup: Removes the deprecated forward_request, _forward_request_to_gateway, and _forward_request_to_all methods from gateway_service.py. This finalizes the removal of the unused "Federation" logic as tracked in Issue:
[CHORE]: Cleanup unused Federation module and duplicate Forwarding logic #1912.
SSE Parsing Fix: Updates the SSE parser in llm_proxy_service.py to correctly handle data: lines that are missing a space after the colon (e.g., data:{"key": "value"}).

🔁 Reproduction Steps

1. Federation/Forwarding Removal:

(Code Cleanup) Examine mcpgateway/services/gateway_service.py to see the methods are removed.
Attempt to call resources/read for a non-existent local resource. Previously, it might have attempted to forward. Now, it immediately returns a Resource not found (-32002) error.

2. SSE Parsing Bug:

Configure an LLM provider that returns SSE events formatted as data:{...} (no space) instead of data: {...}.
Initiate a streaming chat completion.
Before: The parser would fail or misinterpret the JSON payload.
After: The parser correctly handles the data regardless of the leading space.

🐞 Root Cause

1. Forwarding: The forwarding logic was legacy code from the "Federation" module which has been deprecated. It was duplicating logic handled by ToolService and was no longer wired correctly into the application lifecycle. This federation/forwarding logic is removed but some functions still existed in gateway_service.py for forwarding to other gateways (this feature is deprecated now.)

2. SSE Parsing: The existing parser assumed a strict data: prefix (with space). While the spec recommended a space, some providers/implementations omit it, causing orjson.loads to fail on the malformed string.

💡 Fix Description

Removed Forwarding Logic:

Deleted forward_request, _forward_request_to_gateway, and _forward_request_to_all from gateway_service.py.
Updated main.py call sites to log a warning and return strict JSON-RPC errors (e.g., -32000 / -32002) when a local resource/tool is not found, rather than attempting a fallback.
Removed unit tests in test_gateway_service.py and test_gateway_service_oauth_comprehensive.py that covered this deprecated functionality.

Robust SSE Parsing:

Updated llm_proxy_service.py (and translate.py) to inspect the line content after data:.
Added logic to conditionally strip the leading space only if it exists, ensuring both data: {...} and data:{...} are parsed correctly as valid JSON.

References:

Issue for Federation: [CHORE]: Cleanup unused Federation module and duplicate Forwarding logic #1912
PR for Federation: Cleanup Federation Redundant Code #1928

🧪 Verification

Check	Command	Status
Lint suite	`make lint`
Unit tests	`make test`
Coverage ≥ 80 %	`make coverage`
Manual regression no longer fails	steps / screenshots

📐 MCP Compliance (if relevant)

Matches current MCP spec
No breaking change to MCP clients

✅ Checklist

Code formatted (make black isort pre-commit)
No secrets/credentials committed

crivetimihai · 2026-02-04T00:53:13Z

Good cleanup — removing the silent forward_request fallback in favor of explicit JSON-RPC errors is the right approach. The deleted forwarding code in gateway_service.py was significant dead weight. CI is all green.

LGTM — ready to merge.

Remove deprecated forward_request, _forward_request_to_gateway, and _forward_request_to_all methods from gateway_service.py. Replace forwarding fallbacks in main.py with proper JSON-RPC error responses. Fix SSE parser in llm_proxy_service.py and translate.py to handle data: lines with or without a space after the colon, per the SSE spec. Closes #1595 Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com>

Simplify except (ValueError, Exception) to except Exception since ValueError is a subclass of Exception. Update SSE data: line parsing in integration and e2e tests to match the spec-correct pattern used in production code. Signed-off-by: Mihai Criveti <crivetimihai@gmail.com>

crivetimihai · 2026-02-11T11:49:49Z

Rebase & Review Notes

Rebased onto current main (resolved 3 merge conflicts) and squashed the original 5 commits into a single clean commit, preserving original authorship. Added a follow-up commit with additional cleanup.

Issues found and fixed

Issue	Severity	Fix
~24 tests still calling removed methods (`TestForwardRequestToGateway`, `TestForwardRequestDispatch`, `TestForwardRequestToAll`, `TestForwardRequestOAuthAuthCode` in `test_gateway_service.py`)	Critical	Removed all 4 stale test classes
Stale test in `test_main_extended.py` (`test_handle_rpc_fallback_forward_request_model_dump_and_internal_error` still mocking `gateway_service.forward_request`)	Critical	Rewrote test for the new error behavior
Stale docstrings in `gateway_service.py` still listing "Request forwarding" as a feature	Minor	Removed
Unused imports (`urljoin`, `get_db`) left in `gateway_service.py` after method removal	Minor	Cleaned up
Spurious blank line in `translate.py` between `if data:` and `print(data)`	Minor	Removed
Redundant `except (ValueError, Exception):` in fallback handler (`ValueError` is a subclass of `Exception`)	Minor	Simplified to `except Exception:`
Inconsistent SSE parsing in test files — 19 occurrences in `tests/e2e/` and `tests/integration/` still using old `startswith("data: ")` pattern	Minor	Updated to spec-correct pattern matching production code

Review assessment

Forwarding removal: Correct — deprecated federation logic that duplicated ToolService functionality. Reduces attack surface (removes SSRF-capable code paths).
SSE parsing fix: Spec-correct — strips exactly one optional leading space per the SSE specification (HTML Living Standard Section 9.2).
Error codes: Acceptable — -32002 (resource not found) is a valid server-defined error; -32601 (tool not found) matches codebase convention; -32000 (invalid method fallback) is reasonable.
No security or performance concerns introduced.
All 699 affected unit tests pass.

* fix: remove deprecated forwarding methods and fix SSE data parsing Remove deprecated forward_request, _forward_request_to_gateway, and _forward_request_to_all methods from gateway_service.py. Replace forwarding fallbacks in main.py with proper JSON-RPC error responses. Fix SSE parser in llm_proxy_service.py and translate.py to handle data: lines with or without a space after the colon, per the SSE spec. Closes #1595 Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> * fix: clean up redundant except clause and align SSE parsing in tests Simplify except (ValueError, Exception) to except Exception since ValueError is a subclass of Exception. Update SSE data: line parsing in integration and e2e tests to match the spec-correct pattern used in production code. Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> --------- Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> Co-authored-by: Mihai Criveti <crivetimihai@gmail.com>

* fix: remove deprecated forwarding methods and fix SSE data parsing Remove deprecated forward_request, _forward_request_to_gateway, and _forward_request_to_all methods from gateway_service.py. Replace forwarding fallbacks in main.py with proper JSON-RPC error responses. Fix SSE parser in llm_proxy_service.py and translate.py to handle data: lines with or without a space after the colon, per the SSE spec. Closes #1595 Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> * fix: clean up redundant except clause and align SSE parsing in tests Simplify except (ValueError, Exception) to except Exception since ValueError is a subclass of Exception. Update SSE data: line parsing in integration and e2e tests to match the spec-correct pattern used in production code. Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> --------- Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> Co-authored-by: Mihai Criveti <crivetimihai@gmail.com> Signed-off-by: Vishu Bhatnagar <vishu.bhatnagar@ibm.com>

* fix: remove deprecated forwarding methods and fix SSE data parsing Remove deprecated forward_request, _forward_request_to_gateway, and _forward_request_to_all methods from gateway_service.py. Replace forwarding fallbacks in main.py with proper JSON-RPC error responses. Fix SSE parser in llm_proxy_service.py and translate.py to handle data: lines with or without a space after the colon, per the SSE spec. Closes IBM#1595 Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> * fix: clean up redundant except clause and align SSE parsing in tests Simplify except (ValueError, Exception) to except Exception since ValueError is a subclass of Exception. Update SSE data: line parsing in integration and e2e tests to match the spec-correct pattern used in production code. Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> --------- Signed-off-by: Keval Mahajan <mahajankeval23@gmail.com> Signed-off-by: Mihai Criveti <crivetimihai@gmail.com> Co-authored-by: Mihai Criveti <crivetimihai@gmail.com>

kevalmahajan requested review from crivetimihai and madhav165 as code owners February 2, 2026 11:08

crivetimihai added this to the Release 1.0.0-RC1 milestone Feb 3, 2026

crivetimihai self-assigned this Feb 4, 2026

kevalmahajan and others added 2 commits February 11, 2026 11:32

crivetimihai force-pushed the 1595_sse_forwarding_fix branch from d09179d to 055e7c3 Compare February 11, 2026 11:49

crivetimihai approved these changes Feb 11, 2026

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crivetimihai merged commit 0b0895f into main Feb 11, 2026
52 checks passed

crivetimihai deleted the 1595_sse_forwarding_fix branch February 11, 2026 13:19

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Remove Forwarding Methods & Fix SSE Parsing#2647

Remove Forwarding Methods & Fix SSE Parsing#2647
crivetimihai merged 2 commits intomainfrom
1595_sse_forwarding_fix

kevalmahajan commented Feb 2, 2026 •

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kevalmahajan commented Feb 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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🐛 Bug-fix PR

📌 Summary

🔁 Reproduction Steps

🐞 Root Cause

💡 Fix Description

🧪 Verification

📐 MCP Compliance (if relevant)

✅ Checklist

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crivetimihai commented Feb 4, 2026

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crivetimihai commented Feb 11, 2026

Rebase & Review Notes

Issues found and fixed

Review assessment

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kevalmahajan commented Feb 2, 2026 •

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