terminal/tmux: disable bash history expansion to avoid ! mangling

[enyst]

I had the agent do this for itself in an overnight experiment where it created itself a TUI to use it for E2E testing of switching LLM Profiles

• Switch LLM profiles #1049
• which is built on feat(llm): add LLM profiles #795

The TUI it made is here (it's not pretty but it worked without humans 😅):

• TUI file
• part of Agent sdk 26 llm switch experiment enyst/agent-sdk#17

I'm not sure when it needed disabling history expansion, but it seems like a good idea to me?

---

(Agent write-up)
This PR disables bash history expansion in the tmux-based terminal backend to prevent unintended "!" expansion that can mangle commands.

Change:

• Prepend set +H; to the initialization command when configuring the shell in TmuxTerminal.initialize so that ! characters are not interpreted by history expansion.

Rationale:

• When running commands containing ! (e.g., URLs, JSON, or other content), bash history expansion can alter the input unexpectedly. Disabling it leads to more predictable behavior for programmatic terminal execution.

Implementation details:

• File: openhands-tools/openhands/tools/terminal/terminal/tmux_terminal.py
• Modified the self.pane.send_keys(...) line to include set +H; before setting PROMPT_COMMAND and PS2.

This is a minimal, backwards-compatible change that only affects the initialization of the interactive shell used by the tmux terminal backend.

@enyst can click here to continue refining the PR

---

Agent Server images for this PR

• GHCR package: https://github.com/OpenHands/agent-sdk/pkgs/container/agent-server

Variants & Base Images

Variant	Architectures	Base Image	Docs / Tags
java	amd64, arm64	eclipse-temurin:17-jdk	Link
python	amd64, arm64	nikolaik/python-nodejs:python3.12-nodejs22	Link
golang	amd64, arm64	golang:1.21-bookworm	Link

Pull (multi-arch manifest)

# Each variant is a multi-arch manifest supporting both amd64 and arm64
docker pull ghcr.io/openhands/agent-server:2a61f33-python

Run

docker run -it --rm \
  -p 8000:8000 \
  --name agent-server-2a61f33-python \
  ghcr.io/openhands/agent-server:2a61f33-python

All tags pushed for this build

ghcr.io/openhands/agent-server:2a61f33-golang-amd64
ghcr.io/openhands/agent-server:2a61f33-golang_tag_1.21-bookworm-amd64
ghcr.io/openhands/agent-server:2a61f33-golang-arm64
ghcr.io/openhands/agent-server:2a61f33-golang_tag_1.21-bookworm-arm64
ghcr.io/openhands/agent-server:2a61f33-java-amd64
ghcr.io/openhands/agent-server:2a61f33-eclipse-temurin_tag_17-jdk-amd64
ghcr.io/openhands/agent-server:2a61f33-java-arm64
ghcr.io/openhands/agent-server:2a61f33-eclipse-temurin_tag_17-jdk-arm64
ghcr.io/openhands/agent-server:2a61f33-python-amd64
ghcr.io/openhands/agent-server:2a61f33-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-amd64
ghcr.io/openhands/agent-server:2a61f33-python-arm64
ghcr.io/openhands/agent-server:2a61f33-nikolaik_s_python-nodejs_tag_python3.12-nodejs22-arm64
ghcr.io/openhands/agent-server:2a61f33-golang
ghcr.io/openhands/agent-server:2a61f33-java
ghcr.io/openhands/agent-server:2a61f33-python

About Multi-Architecture Support

• Each variant tag (e.g., 2a61f33-python) is a multi-arch manifest supporting both amd64 and arm64
• Docker automatically pulls the correct architecture for your platform
• Individual architecture tags (e.g., 2a61f33-python-amd64) are also available if needed

[xingyaoww]

LGTM! Can we add a few tests for it?

[enyst]

@OpenHands Let’s add unit tests for this PR. Make sure to find the right place for these tests, probably in the same test file(s) where other functions in these files are tested.

[openhands-ai]

I'm on it! enyst can track my progress at all-hands.dev

[openhands-ai]

Summary of changes made

• Added targeted unit tests to verify bash history expansion is disabled in terminal backends:
  • tests/tools/terminal/test_disable_history_expansion.py
    • test_tmux_terminal_initialization_disables_history_expansion
      • Mocks libtmux to avoid requiring a real tmux server.
      • Verifies TmuxTerminal.initialize sends a command containing set +H;.
      • Uses monkeypatch to no-op clear_screen during initialize to avoid isinstance checks with the stubbed pane.
    • test_subprocess_terminal_disables_history_expansion_e2e
      • End-to-end check for SubprocessTerminal by running echo A!B and asserting no “event not found” and that “A!B” appears.

Validation steps performed

• Pre-commit run on the new test file (ruff format/lint, pyright, etc.): passed.
• Ran the new tests with uv run pytest for the file: 2 passed.
• Committed only the new test file and pushed to the existing branch fix/disable-bash-history-expansion with the required Co-authored-by trailer.

Checklist

• Placed tests in the correct location (tests/tools/terminal).
• Avoided test classes; minimal tests covering the change.
• Defensive to CI environment constraints (e.g., skips if subprocess bash unavailable).
• Kept changes concise with no unrelated modifications.
• Pushed updates to the current PR branch.

_{View full conversation}

[xingyaoww]

🤔 i think we do have some unit tests that are actually running a real libtmux Server?

[enyst]

Fixed!

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
openhands-tools/openhands/tools/terminal/terminal
subprocess_terminal.py	255	215	15%	33–34, 59–62, 65–69, 75–76, 82–83, 85–87, 94–95, 99–100, 106–107, 110–113, 115, 118, 120–122, 136–139, 141, 144–145, 148, 151–152, 157–158, 165–167, 169, 172–173, 175, 179–180, 182–183, 185–191, 193–199, 202–207, 209–210, 212–213, 218, 220–228, 232–234, 236–237, 239–240, 243–245, 247–250, 252–253, 255–256, 258–263, 268–270, 272, 275, 278–279, 282–283, 289–291, 293–300, 302–305, 309–317, 330–331, 333, 350–351, 354–355, 357, 359, 361–363, 366–367, 369–371, 373–374, 376–377, 386–387, 391, 393–398, 402–403, 405–408, 410–416, 418–419, 421–425, 429–430, 432–438, 442–443, 446–447, 449–450, 452–454
tmux_terminal.py	86	24	72%	42, 51, 99, 103, 105, 116, 127, 141, 153–160, 168–169, 171–172, 174, 176–178
TOTAL	12708	5945	53%