MCP prompts/list failure wipes the cached prompt list and announces it as empty #50918

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1. opencodejr commented on Oct 28, 2026

   

   opencodejrBot

   on Oct 28, 2026

   Contributor

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   Thanks for the detailed report. I can confirm this on the latest dev (fa1260d).

   To reproduce it, I changed the resourceServer test fixture so its prompts capability advertises listChanged: true and prompts/list can be made to fail on demand. Then I connected through Mcp.Service and waited until service.prompts() returned ["greet"]. Next I made prompts/list fail and sent notifications/prompts/list_changed:

   • service.prompts() became [].
   • service.servers() still reported { status: "connected" }.

   When I removed Effect.orElseSucceed(() => []) from refreshPrompts, the failed refresh kept greet, which matches how refreshTools behaves. The script below reproduces it against a source checkout.

   Reproduction script (repro.sh)

   #!/usr/bin/env bash
   # Reproduces anomalyco/opencode#50918: a failed MCP prompts/list refresh wipes the server's prompts
   # while the server stays "connected".
   # Usage: REPO=/path/to/opencode-checkout bash repro.sh   (needs `bun install` done in the checkout)
   set -euo pipefail
   REPO=${REPO:-/workspace/repo}
   cd "$REPO/packages/core"
   TEST=test/mcp.test.ts
   cp "$TEST" /tmp/mcp.test.ts.orig
   trap 'cp /tmp/mcp.test.ts.orig "$REPO/packages/core/$TEST"' EXIT
   
   # 1. Let the resourceServer fixture fail prompts/list on demand and send prompts/list_changed.
   python3 - "$TEST" <<'PY'
   import sys
   p = sys.argv[1]
   s = open(p).read()
   s = s.replace("""        sessions: [] as string[],
         }""", """        sessions: [] as string[],
           failPrompts: false,
           promptLists: 0,
         }""", 1)
   s = s.replace("""protocol.setRequestHandler("prompts/list", () => Promise.resolve({ prompts: [{ name: "greet" }] }))""",
   """protocol.setRequestHandler("prompts/list", () =>
             ++state.promptLists && state.failPrompts
               ? Promise.reject(new Error("prompts/list temporarily unavailable"))
               : Promise.resolve({ prompts: [{ name: "greet" }] }),
           )""", 1)
   s = s.replace("""              prompts: {},""", """              prompts: { listChanged: true },""", 1)
   s = s.replace("""        completeElicitation: () =>""", """        sendPromptListChanged: () => current.protocol.sendPromptListChanged(),
           completeElicitation: () =>""", 1)
   s += '''
   
   test("repro #50918: failed prompts/list refresh keeps existing prompts", async () => {
     await Effect.runPromise(
       Effect.scoped(
         Effect.gen(function* () {
           const server = yield* resourceServer()
           yield* Effect.gen(function* () {
             const service = yield* Mcp.Service
             expect(yield* settled(service)).toEqual({ status: "connected" })
             // Initial listing succeeds.
             yield* service.prompts().pipe(
               Effect.filterOrFail((p) => p.length > 0, () => new Error("no prompts yet")),
               Effect.retry({ times: 200, schedule: Schedule.spaced("10 millis") }),
             )
             console.log("before:", JSON.stringify((yield* service.prompts()).map((p) => p.name)))
             // Server announces a change, then fails the re-list.
             server.state.failPrompts = true
             yield* Effect.promise(server.sendPromptListChanged)
             yield* Effect.sleep("500 millis")
             const after = yield* service.prompts()
             console.log("after:", JSON.stringify(after.map((p) => p.name)))
             console.log("prompts/list calls:", server.state.promptLists)
             console.log("status:", JSON.stringify(yield* settled(service)))
             expect(after.map((p) => p.name)).toEqual(["greet"])
           }).pipe(Effect.provide(resourceMcpLayer(server.url)))
         }),
       ),
     )
   })
   '''
   open(p, "w").write(s)
   PY
   
   bun test "$TEST" -t "repro #50918"

   Run it: bash repro.sh
2. opencodejr

   added

   reproduced

   on Oct 28, 2026
3. Tarquinen

   closed this as completedin #62266on Nov 7, 2026