fix(core): correct exitCode null check in shell sandbox denial heuristic by chelsealong · Pull Request #29186 · google-gemini/gemini-cli

chelsealong · 2026-09-03T16:20:13Z

What broke

ShellToolInvocation's "Heuristic Sandbox Denial Detection" block
(packages/core/src/tools/shell.ts:868) checked:

(result.exitCode !== undefined && result.exitCode !== 0) ||

but ExecutionResult.exitCode is typed number | null
(packages/core/src/services/executionLifecycleService.ts:23) — it is
never undefined. Since null !== undefined is true, a process
killed by a signal without a captured signal string (exitCode === null) spuriously satisfied this guard and entered the sandbox-denial
heuristic, even though nothing indicates a sandbox denial in that
case. Three other checks in the same function already correctly use
!== null (e.g. the two result.exitCode !== null && result.exitCode !== 0 sites earlier in the method).

Fix

Changed the guard to result.exitCode !== null && result.exitCode !== 0, matching the sibling checks and the actual type.

Testing

Added a regression test in
packages/core/src/tools/shell.test.ts (sandbox heuristics
describe block) that resolves the execution promise with
exitCode: null, signal: null, error: null, aborted: false and
asserts sandboxManager.parseDenials is not called and the result
is not flagged SANDBOX_EXPANSION_REQUIRED.

Confirmed the test fails without the fix:

$ git checkout HEAD~1 -- packages/core/src/tools/shell.ts
$ npx vitest run src/tools/shell.test.ts -t "should NOT run sandbox denial detection"
 FAIL  src/tools/shell.test.ts > ShellTool > sandbox heuristics > should NOT run sandbox denial detection when exitCode is null without a signal
AssertionError: expected "spy" to not be called at all, but actually been called 1 times
$ git checkout HEAD -- packages/core/src/tools/shell.ts

And passes with the fix applied:

$ npx vitest run src/tools/shell.test.ts
 ✓ src/tools/shell.test.ts (90 tests | 1 skipped) 488ms
 Test Files  1 passed (1)
      Tests  89 passed | 1 skipped (90)

Also ran, both clean:

$ npx eslint packages/core/src/tools/shell.ts packages/core/src/tools/shell.test.ts --max-warnings 0
$ npx tsc --noEmit   # in packages/core

AI assistance disclosure

This change was prepared with the assistance of an AI coding agent
(Claude), including drafting the fix, the regression test, and this
PR description. All changes were reviewed and verified locally before
submission.

The sandbox denial heuristic in ShellToolInvocation checked `result.exitCode !== undefined`, but ExecutionResult.exitCode is typed `number | null`, never undefined. This meant signal-killed processes with exitCode === null (and no captured signal) spuriously triggered the sandbox-denial detection path. Three other checks in the same function already use `!== null`; this aligns the fourth with them.

github-actions · 2026-09-03T16:20:30Z

📊 PR Size: size/S

Lines changed: 36
Additions: +35
Deletions: -1
Files changed: 2

github-actions · 2026-09-03T16:20:39Z

🛑 Action Required: Evaluation Approval

Steering changes have been detected in this PR. To prevent regressions, a maintainer must approve the evaluation run before this PR can be merged.

Maintainers:

Go to the Workflow Run Summary.
Click the yellow 'Review deployments' button.
Select the 'eval-gate' environment and click 'Approve'.

Once approved, the evaluation results will be posted here automatically.

gemini-code-assist · 2026-09-03T16:20:52Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a bug in the shell tool's sandbox denial detection logic where an incorrect type check caused processes with null exit codes to be erroneously flagged as sandbox denials. By aligning the guard condition with the actual type definition of the exit code, the fix ensures more accurate heuristic behavior and includes a regression test to prevent future occurrences.

Highlights

Corrected exitCode null check: Updated the sandbox denial heuristic in ShellToolInvocation to correctly check for null instead of undefined when evaluating exitCode, preventing spurious sandbox denial triggers.
Added regression test: Introduced a new test case in shell.test.ts to verify that processes exiting with null exit codes without signals do not trigger the sandbox denial heuristic.

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Code Review

This pull request modifies the sandbox denial detection logic in ShellToolInvocation to check if result.exitCode is not null instead of undefined. It also adds a unit test to ensure sandbox denial detection is not executed when exitCode is null without a signal. No review comments were provided, so there is no feedback to address.

gemini-cli · 2026-09-11T01:44:29Z

Hi there! Thank you for your interest in contributing to Gemini CLI.

To ensure we maintain high code quality and focus on our prioritized roadmap, we only guarantee review and consideration of pull requests for issues that are explicitly labeled as 'help wanted'.

This PR will be closed in 7 days if it remains without that designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

gemini-cli · 2026-09-18T01:47:03Z

This pull request is being closed as it has been open for 14 days without a 'help wanted' designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

chelsealong requested a review from a team as a code owner September 3, 2026 16:20

github-actions Bot added the size/s A small PR label Sep 3, 2026

chelsealong had a problem deploying to eval-gate September 3, 2026 16:20 — with GitHub Actions Failure

gemini-code-assist Bot reviewed Sep 3, 2026

View reviewed changes

gemini-cli Bot added priority/p1 Important and should be addressed in the near term. area/security Issues related to security labels Sep 3, 2026

gemini-cli Bot added the status/pr-nudge-sent label Sep 11, 2026

github-actions Bot mentioned this pull request Sep 11, 2026

📊 AI CLI 工具社区动态日报 2026-09-11 96loveslife/big_model_radar#471

Open

gemini-cli Bot closed this Sep 18, 2026

github-actions Bot mentioned this pull request Sep 18, 2026

📊 AI CLI 工具社区动态日报 2026-09-18 96loveslife/big_model_radar#507

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fix(core): correct exitCode null check in shell sandbox denial heuristic - #29186

fix(core): correct exitCode null check in shell sandbox denial heuristic#29186
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chelsealong:fix/shell-exitcode-null-check

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chelsealong commented Sep 3, 2026

What broke

Fix

Testing

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