Agent Client Protocol (ACP)

ACP is an open protocol from Zed for editor-to-agent communication over stdin/stdout JSON-RPC. roborev uses ACP to integrate agents that don’t have built-in adapters. If an agent speaks ACP (or has a wrapper that does), you can plug it in.

How It Works

roborev acts as the ACP client. The agent process is the ACP server.

roborev launches the agent command as a subprocess
Communication happens via stdin/stdout JSON-RPC
roborev negotiates a session mode and model with the agent
Prompts are sent, and the agent streams responses back
roborev enforces file access boundaries (read-only vs read-write) at the operation level

Setup with Well-Known Agents

Several agents have ACP wrappers you can install directly.

Agent	ACP Wrapper	Install
Codex	`codex-acp`	`npm install -g @zed-industries/codex-acp`
Claude Code	`claude-agent-acp`	`npm install -g @zed-industries/claude-agent-acp`
Gemini	`gemini --experimental-acp`	`npm install -g @google/gemini-cli`

Configuring a Wrapper

Set command to the wrapper binary in your ACP config:

[acp]
name = "codex-acp"
command = "codex-acp"

Environment Variable Override

Override the ACP command for a single invocation without editing config files:

ROBOREV_ACP_ADAPTER_COMMAND=/opt/agents/my-custom-acp roborev review HEAD

Verifying the Setup

Confirm the configured command is on your PATH, then run a review to test end-to-end communication:

which codex-acp          # or your configured command
roborev review HEAD

Custom ACP Agents

Any binary that implements the ACP server protocol can be used. Set command to its path:

[acp]
name = "my-agent"
command = "/usr/local/bin/my-acp-agent"
args = ["--verbose"]

Once configured, the agent can be selected with --agent my-agent.

Configuration Reference

Configure ACP in the [acp] section of ~/.roborev/config.toml:

[acp]
name = "my-agent"                  # Agent name (required)
command = "/usr/local/bin/my-acp"  # ACP agent command (required)
args = ["--verbose"]               # Additional arguments
model = "my-model"                 # Default model
timeout = 600                      # Timeout in seconds (default: 600)
read_only_mode = "plan"            # Mode for review flows
auto_approve_mode = "auto-approve" # Mode for agentic flows
disable_mode_negotiation = false   # Skip SetSessionMode RPC

Option	Type	Default	Description
`name`	string	(required)	Agent name used in `--agent` flag
`command`	string	(required)	Path or command for the ACP agent binary
`args`	array	`[]`	Additional CLI arguments passed to the agent
`model`	string		Default model to request from the agent
`timeout`	int	`600`	Command timeout in seconds
`read_only_mode`	string	`"plan"`	Mode value sent for review (read-only) flows
`auto_approve_mode`	string	`"auto-approve"`	Mode value sent for agentic flows
`mode`	string		Default agent mode (overrides `read_only_mode` unless explicitly opting in)
`disable_mode_negotiation`	bool	`false`	Skip ACP `SetSessionMode` RPC while keeping authorization behavior

Modes

roborev selects the ACP session mode automatically based on the workflow.

Review Flow

Uses read_only_mode (default: "plan"). The agent can read files but cannot write or run commands. This is used during roborev review and roborev run (without --agentic).

Fix/Refine Flow

Uses auto_approve_mode (default: "auto-approve"). The agent can edit files and run commands. This is used during roborev refine and roborev run --agentic.

Disabling Mode Negotiation

Some agents don’t support ACP session modes. Set disable_mode_negotiation = true to skip the SetSessionMode RPC call. roborev still enforces its own authorization boundaries (read-only vs read-write) regardless of this setting.

Security

ACP agents run as subprocesses with the following guardrails:

Path validation: File operations (reads, writes, edits) are validated against the repository root using symlink-aware path resolution. Terminal operations in read-write mode are not path-bounded and can execute arbitrary commands.
Mode enforcement: Write and terminal operations are blocked at the operation boundary in read-only mode, independent of what the agent requests.
Bounded reads: File reads are capped at 10 MB. Terminal output is capped at 1 MB.

Troubleshooting

”no Codex ACP wrapper command was found”

The ACP wrapper package is not installed. Install it:

npm install -g @zed-industries/codex-acp

“mode X is not available”

The agent doesn’t support the requested session mode. Check which modes the agent supports, or set disable_mode_negotiation = true in your [acp] config.

”model X is not available”

The agent doesn’t support the requested model. Remove the model field from your [acp] config, or check the agent’s documentation for supported model names.

”write operation not permitted in read-only mode”

This is expected during reviews. The agent attempted a write operation, but roborev blocked it because the task is running in review (read-only) mode. If you need file edits, use roborev refine or roborev run --agentic.