Priming streamable http events use hardcoded event id of: "0" #791

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1. glicht

   added

   bugSomething is not workingSomething is not working

   on Apr 7, 2026
2. glicht commented on Apr 10, 2026

   

   glicht

   on Apr 10, 2026

   ContributorAuthor

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   @DaleSeo thanks for taking this. The fix in your branch looks good. In a test I ran, I am able to resume on the priming event.

   I would like to raise another issue that the resume only works as long as the ongoing request is executing, which is sub optimal.

   For example using servers_counter_streamhttp example and the tool long_task (which runs for 10 seconds) with the following script works and I am able to get the result when performing a GET request to resume:

   #!/usr/bin/env bash
   
   URL="${1:-http://localhost:8000/mcp}"
   
   echo "Connecting to MCP server at $URL"
   
   # POST initialize and capture session ID from response header
   SESSION_ID=$(curl -s -D - -o /dev/null \
     -X POST "$URL" \
     -H "Accept: application/json, text/event-stream" \
     -H "Content-Type: application/json" \
     -d '{
       "jsonrpc": "2.0",
       "id": 1,
       "method": "initialize",
       "params": {
         "protocolVersion": "2025-06-18",
         "capabilities": {},
         "clientInfo": { "name": "test-client", "version": "1.0.0" }
       }
     }' | grep -i "^mcp-session-id:" | awk '{print $2}' | tr -d '\r')
   
   if [[ -z "$SESSION_ID" ]]; then
     echo "ERROR: No Mcp-Session-Id header in response"
     exit 1
   fi
   
   echo "Session ID: $SESSION_ID"
   export MCP_SESSION_ID="$SESSION_ID"
   
   # POST notifications/initialized to complete the MCP handshake
   STATUS=$(curl -s -o /dev/null -w "%{http_code}" \
     -X POST "$URL" \
     -H "Accept: application/json, text/event-stream" \
     -H "Content-Type: application/json" \
     -H "Mcp-Session-Id: $MCP_SESSION_ID" \
     -H "Mcp-Protocol-Version: 2025-06-18" \
     -d '{
       "jsonrpc": "2.0",
       "method": "notifications/initialized"
     }')
   
   if [[ "$STATUS" != "202" ]]; then
     echo "ERROR: notifications/initialized returned $STATUS, expected 202" >&2
     exit 1
   fi
   
   echo "Handshake complete (202 Accepted)"
   echo "MCP_SESSION_ID=$MCP_SESSION_ID"
   
   
   echo "Calling tool long_task ..."
   
   curl "$URL" \
     -H 'accept: application/json, text/event-stream' \
     -H 'content-type: application/json' \
     -H "Mcp-Protocol-Version: 2025-06-18" \
     -H "mcp-session-id: $MCP_SESSION_ID" \
     --max-time 5 \
     --data-raw '{"method":"tools/call","params":{"name":"long_task","arguments":{},"_meta":{"progressToken":1}},"jsonrpc":"2.0","id":'"1"'}'
   
   echo "sleeping 3 seconds"
   sleep 3
   echo "calling resume on the stream after timeout..."
   
   curl "$URL" \
     -H 'accept: application/json, text/event-stream' \
     -H 'content-type: application/json' \
     -H "Mcp-Protocol-Version: 2025-06-18" \
     -H "mcp-session-id: $MCP_SESSION_ID" \
     -H "last-event-id: 0/0" \
     --max-time 2

   But if I change the script so the curl with the tools/call has a timeout of 8 and then with the sleep of 3., so total time since start of request is 11, the resume GET request will not work.

   From what I understand the cache of the results from the stream is discarded once the request completes processing and thus the resume doesn't work when it extends beyond the time of the request.

   👀React with 👀1Reacted by Dale Seo
3. DaleSeo commented on Apr 10, 2026

   

   DaleSeo

   on Apr 10, 2026

   Member

   More actions

   @glicht Thanks for confirming that the priming fix works and for suggesting the follow-up!

   I've added a second fix in the same PR #799 that keeps the cache after completion. The sender is replaced with a closed dummy, so no new events are routed, but the cached events remain available for resume. The stream ends cleanly after replaying.

   I'd appreciate it if you could take another look when you have a chance.

   👍React with 👍1Reacted by Guy Lichtman
4. alexhancock

   closed this as completedin #799on Apr 16, 2026