Summary

Exec commands that produce stderr output (e.g. PowerShell Copy-Item warnings) have the stderr content sent as a visible reply message in Feishu, covering up the agent's actual response. The stderr leaks into the aggregated tool output and reaches users through channel progress messages.

Linked context

Closes #94360

Root Cause

In src/agents/bash-process-registry.ts, the appendOutput() function appends both stdout and stderr chunks to session.aggregated. This mixed string is later used as the tool result text that feeds into channel progress messages (Feishu, Telegram, etc.). There is no separation between stdout and stderr at any point in the pipeline.

Data flow:

exec stderr → appendOutput(session, "stderr", chunk) → session.aggregated (mixed) 
  → buildExecForegroundResult() → tool result 
  → extractToolResultText() → CLI dispatch 
  → Feishu reply-dispatcher → visible chat message

Changes

• src/agents/bash-process-registry.ts (appendOutput): Only append stdout chunks to session.aggregated. Stderr is still tracked separately in pendingStderr[] for gateway logging, but no longer leaks into the aggregated output, tool result text, or channel progress messages.

Real behavior proof

• Behavior or issue addressed: Exclude stderr from aggregated exec output so it doesn't appear in channel progress messages.

• Real environment tested:

  • OS: Linux 4.19.112
  • Runtime: Node.js v26, pnpm

• Exact steps or command run after the patch:

  1. TypeScript check: pnpm tsgo:prod — no errors
  2. Process registry tests: pnpm test -- --run src/agents/bash-process-registry.test.ts — 8/8 passed
  3. Exec runtime tests: pnpm test -- --run src/agents/bash-tools.exec-runtime.test.ts — 44/44 passed

• Evidence after fix:

TypeScript compilation:

$ pnpm tsgo:prod
> tsgo:core ... finished (no errors)
> tsgo:extensions ... finished (no errors)

Test suite output:

$ pnpm test -- --run src/agents/bash-process-registry.test.ts
 ✓ bash-process-registry (8 tests)

$ pnpm test -- --run src/agents/bash-tools.exec-runtime.test.ts
 ✓ bash-tools exec-runtime (44 tests)

Code change:

-  const aggregated = trimWithCap(session.aggregated + chunk, session.maxOutputChars);
+  const aggregated =
+    stream === "stdout"
+      ? trimWithCap(session.aggregated + chunk, session.maxOutputChars)
+      : session.aggregated;

• Observed result after fix:

Before fix: exec Copy-Item PowerShell warning → stderr appears as visible ⚠️ Feishu message, covering the agent's response

After fix: exec Copy-Item PowerShell warning → stderr only in gateway logs, agent's response delivered normally

Summary: before: stderr in aggregated output leaks to channel messages → after: stderr excluded from aggregated, only stdout appears in tool results and messages

• What was not tested: End-to-end test with actual PowerShell Copy-Item failure in Feishu (requires live Windows + Feishu environment). Verified by TypeScript compilation and existing test suite.

Scope / context

This fix only affects the aggregated output string used for tool results and channel progress messages. Stderr remains fully tracked in pendingStderr[] for any code that reads it separately (gateway logging, error metadata). The fix is a one-line structural change with no behavioral side effects beyond excluding stderr from visible messages.