# NousResearch/hermes-agent · CORS headers missing on SSE streaming endpoints

## Open now

- Nothing open on GitHub.

Bug reports and fixes addressing missing CORS headers on Server-Sent Events (SSE) streaming endpoints, which causes cross-origin requests to fail. Multiple fix attempts target the /v1/runs/{run_id}/events endpoint and general streaming responses.

## TL;DR

- 3 member(s): 0 open issue(s), 1 closed issue(s), 0 open PR(s), 1 merged PR(s), 1 PR(s) closed without merging.
- A fix was merged to main in PR #3573. Verify it addresses your case.
- **Recommended:** read PR #3573 (and any competing PRs below) before filing. Confirm the merged change covers your symptom.

## Maintainer resolution verdict

- Internal-tracker verdict over this cluster's issue members: `unresolved`. This is distinct from the fix status above. Weigh it yourself.

## How this cluster was grouped

- Link evidence (`STRUCTURAL_SPANNING`): every member is connected by structural evidence: shared changed files, or a closing/superseded reference.
- Pairwise link density `0.67`: the share of member pairs that carry a link, counting a structural link in full and a relevance-only link at 0.36. `1.00` means every pair is linked.

## Closed / duplicate issues

- #3378: \[Bug\]: headers missing on streaming responses (stream:true)

## Prior & competing PRs

- **#3573: fix(api-server): add CORS headers to streaming SSE responses**. merged to main · fix tier `verified`
  - maintainer direction: category `merged`
  - files: `gateway/platforms/api_server.py`
  - fix hunks:
  - `gateway/platforms/api_server.py`

    ```diff
    @@ -582,10 +582,14 @@ async def _write_sse_chat_completion(
             """
             import queue as _q
     
    -        response = web.StreamResponse(
    -            status=200,
    -            headers={"Content-Type": "text/event-stream", "Cache-Control": "no-cache"},
    -        )
    +        sse_headers = {"Content-Type": "text/event-stream", "Cache-Control": "no-cache"}
    +        # CORS middleware can't inject headers into StreamResponse after
    +        # prepare() flushes them, so resolve CORS headers up front.
    +        origin = request.headers.get("Origin", "")
    +        cors = self._cors_headers_for_origin(origin) if origin else None
    +        if cors:
    +            sse_headers.update(cors)
    +        response = web.StreamResponse(status=200, headers=sse_headers)
             await response.prepare(request)
     
             try:
    ```
- **#3381: fix(api-server): add CORS headers to streaming SSE responses**. closed without merge
  - maintainer direction: category `merged_via`; implication `superseded`; refs `#3573`

## Fix status

- Merged to main in PR #3573 (cited above). No release data is tracked. Verify downstream.
- Fix last verified (merged) `2026-03-28`. This confirmation is old and may be out of date (a revert/reopen would not have invalidated it here); re-verify.
- Subsystem: `gateway`