Summary

• drop orphaned trailing user leaves that came from inter-session provenance when a fresh prompt is already present
• keep existing queued-user-message repair for normal user prompts intact
• add regression coverage for stale inter-session messages shadowing fresh prompts

Why

A stale inter-session subagent completion can be left as a trailing user leaf. The orphan repair path currently prepends that leaf ahead of a newer prompt, so stale control text such as NO_REPLY can shadow the fresh user/voice request and route incorrectly.

Inter-session leaves are system-delivered completion context, not user text that arrived while a previous turn was active. When a fresh prompt exists, the safer repair is to remove the stale leaf rather than merge it into the new prompt.

Test plan

• git diff --check
• corepack pnpm exec vitest run src/agents/pi-embedded-runner/run/attempt.test.ts src/agents/pi-embedded-runner/run/transcript-repair-runtime-contract.test.ts

Real behavior proof

• Behavior or issue addressed: Stale inter-session trailing user leaves such as NO_REPLY are dropped instead of prepended to a fresh user/voice prompt.
• Real environment tested: Local OpenClaw checkout on this PR branch (fix/drop-stale-inter-session-orphans), rebased onto origin/main at 2daf3d332f; Node 22.22.0 with pnpm/corepack on Linux.
• Exact steps or command run after this patch:

  corepack pnpm exec tsx -e 'import { mergeOrphanedTrailingUserPrompt } from "./src/agents/pi-embedded-runner/run/attempt.prompt-helpers.ts";
  const result = mergeOrphanedTrailingUserPrompt({
    prompt: "fresh voice request",
    trigger: "user" as never,
    leafMessage: {
      content: [{ type: "text", text: "NO_REPLY stale inter-session completion" }],
      provenance: { kind: "inter_session" },
    },
  });
  console.log(JSON.stringify(result, null, 2));
  if (result.prompt.includes("NO_REPLY") || result.merged || !result.removeLeaf) process.exit(1);'

• Evidence after fix: Live terminal output from the patched branch:

  {
    "prompt": "fresh voice request",
    "merged": false,
    "removeLeaf": true
  }

• Observed result after fix: The fresh prompt stayed as fresh voice request; the stale NO_REPLY inter-session leaf was not merged; the helper returned merged: false and removeLeaf: true.
• What was not tested: A full live voice session with a naturally occurring stale inter-session orphan; this proof exercises the actual runtime repair helper on a real patched checkout.

After-fix verification

• Rebased onto latest origin/main and resolved the CHANGELOG.md conflict.
• Scrubbed unrelated rebase/verification lint cleanups from the PR diff; the PR now only changes CHANGELOG.md, attempt.prompt-helpers.ts, and the two focused regression test files.
• git diff --check origin/main...HEAD — passed locally.
• corepack pnpm exec vitest run src/agents/pi-embedded-runner/run/attempt.test.ts src/agents/pi-embedded-runner/run/transcript-repair-runtime-contract.test.ts — passed locally: 4 files, 272 tests.

This also proves the concrete repair behavior through the added runtime-contract regression: an inter-session-provenance trailing user leaf is removed instead of prepended when a fresh prompt exists, while normal queued user prompt repair still merges.