Undo can replay stale instruction notices after rebuilding the current baseline #62027

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1. opencodejr commented on Nov 5, 2026

   

   opencodejrBot

   on Nov 5, 2026

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   Thanks for the detailed report. I reproduced this with the session runner on the latest dev (1c3decd, which includes 3698a9b).

   Steps: set the context entry and send a request, change it to Changed context and send, change it to Latest context and send, then commit an undo to the second request and send again. The next model request has Latest context in its rebuilt system baseline, but its messages still contain the earlier Changed context system notice from before the undo point. The model therefore sees both values.

   The existing revert test only checks the system prompt, which is why it doesn't catch this. Related: #61550 and its PR #61551 fix the same symptom for forks only, not for undo. The script below adds a test scenario that shows the stale notice.

   Reproduction script (repro-62027.sh)

   #!/usr/bin/env bash
   # Reproduces anomalyco/opencode#62027 with the real session runner test harness.
   # Run from a checkout of the opencode repo (dev), after `bun install`.
   set -euo pipefail
   cd "${1:-.}"
   python3 - <<'PY'
   p='packages/core/test/session-runner.test.ts'
   s=open(p).read()
   anchor='  scenario("uses the selected model family prompt when the agent does not override it"'
   add='''  scenario("REPRO 62027 revert does not replay stale instruction notices", function* (s) {
       yield* s.runPrompt("First")
       s.systemBaseline = "Changed context"
       const second = yield* s.runPrompt("Second")
       s.systemBaseline = "Latest context"
       yield* s.runPrompt("Third")
       yield* s.bus.publish(SessionEvent.RevertEvent.Committed, { sessionID, to: second.id })
       yield* s.runPrompt("Fourth")
       const last = s.requests.at(-1)!
       console.log("REPRO system:", JSON.stringify(last.system.map((p) => p.text).slice(2)))
       console.log("REPRO messages:", JSON.stringify(last.messages))
       expect(last.system.map((p) => p.text)).toContain("Latest context")
       expect(JSON.stringify(last.messages)).not.toContain("Changed context")
     })
   
   '''
   assert anchor in s
   open(p,'w').write(s.replace(anchor, add+anchor, 1))
   PY
   cd packages/core
   bun test test/session-runner.test.ts -t "REPRO 62027" || echo "BUG REPRODUCED: stale 'Changed context' notice replayed alongside 'Latest context' baseline"

   Run it: bash repro-62027.sh
2. opencodejr

   added

   reproduced

   on Nov 5, 2026
3. rekram1-node

   closed this as completedin #63667on Nov 13, 2026