Summary

Describe the problem and fix in 2–5 bullets:

• Problem: Telegram 2.15 draft streaming could leak intermediate exec/bash failure warnings after successful fallback, and in a specific streamed path the final answer could be dropped when message_end had tool-call-only content.
• Why it matters: Users saw instability/noise (⚠️ Exec ... failed) or only tool-call artifacts instead of the recovered final answer.
• What changed: Added streamed-reply-aware suppression for exec/bash warnings, preserved streamed assistant text when message_end has no text block, and added regressions for both behaviors.
• What did NOT change (scope boundary): No changes to model fallback policy, no cross-channel formatting changes beyond existing shared payload/subscription logic.

Change Type (select all)

• Bug fix
• Feature
• Refactor
• Docs
• Security hardening
• Chore/infra

Scope (select all touched areas)

• Gateway / orchestration
• Skills / tool execution
• Auth / tokens
• Memory / storage
• Integrations
• API / contracts
• UI / DX
• CI/CD / infra

Linked Issue/PR

• Closes [2026.2.15] Exec failure notifications surface in Telegram after successful fallback #17837
• Closes [Bug]: Exec tool error replaces successful message in Telegram channel #18905
• Closes Telegram: tool failure warning (⚠️ 🛠️ Exec ... failed) can overshadow/mask final assistant reply #18687
• Closes [Bug]:Tool errors overwrite conversational responses in Telegram (2026.2.15) #18244

User-visible / Behavior Changes

• Telegram users should no longer see intermediate exec/bash failure warnings when fallback succeeds and user-facing streamed output already exists.
• In the affected 2.15 streaming path, final answer text is retained instead of being lost when message_end contains no text block.

Security Impact (required)

• New permissions/capabilities? (Yes/No) No
• Secrets/tokens handling changed? (Yes/No) No
• New/changed network calls? (Yes/No) No
• Command/tool execution surface changed? (Yes/No) No
• Data access scope changed? (Yes/No) No
• If any Yes, explain risk + mitigation:

Repro + Verification

Environment

• OS: Linux (dev environment)
• Runtime/container: Node 22+, pnpm 10, vitest
• Model/provider: N/A (unit/e2e harness coverage)
• Integration/channel (if any): Telegram draft-streaming path (test harness)
• Relevant config (redacted): block-streaming disabled for Telegram draft stream path

Steps

1. Stream assistant output to Telegram preview.
2. Trigger an intermediate exec/bash failure and recover via fallback tool.
3. End with a turn where message_end may include tool-call-only content.

Expected

• Recovered final answer is delivered.
• Intermediate exec/bash failure warning is suppressed in user-facing output when fallback succeeded.

Actual

• Before fix: warning leaked and/or final answer could be dropped in this path.
• After fix: warning suppressed (when appropriate) and final streamed text retained.

Evidence

Attach at least one:

• Failing test/log before + passing after
• Trace/log snippets
• Screenshot/recording
• Perf numbers (if relevant)

Human Verification (required)

What you personally verified (not just CI), and how:

• Verified scenarios:
  • pnpm vitest run --config vitest.e2e.config.ts src/agents/pi-embedded-runner/run/payloads.e2e.test.ts
  • pnpm vitest run src/telegram/bot-message-dispatch.test.ts
  • pnpm vitest run --config vitest.e2e.config.ts src/agents/pi-embedded-subscribe.subscribe-embedded-pi-session.does-not-emit-duplicate-block-replies-text.e2e.test.ts
• Edge cases checked:
  • exec and bash warning suppression with streamed user-facing output.
  • streamed delta text retained when message_end carries no text block.
• What you did not verify:
  • Live Telegram account/manual device run in production-like environment.

Compatibility / Migration

• Backward compatible? (Yes/No) Yes
• Config/env changes? (Yes/No) No
• Migration needed? (Yes/No) No
• If yes, exact upgrade steps:

Failure Recovery (if this breaks)

• How to disable/revert this change quickly:
  • Revert commits on this PR branch (4daa4d6f2, d9c095c7b) and redeploy.
• Files/config to restore:
  • src/agents/pi-embedded-runner/run/payloads.ts
  • src/agents/pi-embedded-subscribe.handlers.messages.ts
  • src/agents/pi-embedded-subscribe.ts
• Known bad symptoms reviewers should watch for:
  • ⚠️ Exec/Bash failed reappears before/alongside recovered final answer.
  • streamed answer preview appears but no final answer is delivered.

Risks and Mitigations

List only real risks for this PR. Add/remove entries as needed. If none, write None.

• Risk:
  • Suppressing warnings could hide meaningful exec/bash failures in edge cases.
  • Mitigation:
    • Suppression is limited to cases where user-facing reply already exists; tests cover both show/suppress paths.
• Risk:
  • Streamed-text retention fallback could duplicate text in some message-end shapes.
  • Mitigation:
    • Existing duplicate-avoidance logic remains; added targeted regression test for no-text message_end path.

AI Assistance

• AI-assisted: Yes (Codex)
• Testing level: Lightly tested with focused automated tests listed above.