[feat] Add Devin CLI provider

[ThePlenkov]

Summary

Add Devin CLI as a new built-in provider alongside the existing 7 (Kiro CLI, Claude Code, Codex, Gemini CLI, Kimi CLI, Copilot CLI, Q CLI).

Devin is Cognition's terminal-based AI agent. It supports --permission-mode dangerous for autonomous operation and --prompt-file for system prompt injection, making it well-suited for CAO orchestration.

Implementation Details

We have a working DevinCliProvider (338 lines) implementing BaseProvider. Key aspects:

Terminal State Detection

Devin's TUI has a unique layout that requires special handling:

> user message           ← user input
Response text            ← agent reply
────────────────────     ← horizontal rule (fixed TUI chrome)
#                        ← input prompt (never disappears)
────────────────────     ← horizontal rule
Mode: ... Model: ...     ← status bar

Challenges solved:

• The # prompt is fixed TUI chrome — it never disappears during processing. Processing must be detected by spinner text (Running tools, esc to interrupt) taking priority over prompt detection.
• Ghost/autocomplete text appears after # (e.g. # may be). A relaxed prompt pattern (^[\s]*#) is used, but only when the status bar (Mode:.*Model:) is also visible — proving the TUI is rendered and avoiding false matches on # in code output.
• Stateless completed detection: User input lines are prefixed with > in Devin's TUI. By scanning for ^> .+, we distinguish idle (no input yet) from completed (input was sent, prompt returned) without ephemeral flags that break on server restart.

Command Construction

devin --permission-mode dangerous --respect-workspace-trust false \
      --prompt-file /tmp/cao_devin_prompt_xxx.md \
      --config /tmp/cao_devin_config_xxx.json

MCP Config Merging

Agent profile MCP servers are merged into Devin's ~/.config/devin/config.json, with CAO_TERMINAL_ID injected into each server's env for cross-agent communication.

Response Extraction

Responses are extracted between the last > user input line and the horizontal rule preceding the # prompt — scanning backwards for 2 horizontal rules (Unicode box-drawing characters U+2500-U+257F).

Provider Properties

• paste_enter_count: 1 (single Enter after paste)
• exit_cli(): /exit
• requires_workspace: true

Agent Profiles

Three ready-to-use agent profiles:

• developer.md — Developer agent with MCP server config and multi-agent handoff protocol
• reviewer.md — Code reviewer (review-only, structured APPROVE/REQUEST_CHANGES output)
• supervisor.md — Supervisor that delegates to developer and reviewer in an iterative loop

Tool Mapping

tool_mapping:
  fs_read: Read
  fs_write: Write
  execute_bash: Bash
  web_search: WebSearch
  list_dir: List

Reference Implementation

Full working implementation available at cao-poc — tested and verified with Devin CLI v2.x in both native and containerized environments.

Related

• [feat] Plugin/provider extension API — register providers without patching source #147 (Plugin/provider extension API) — Devin CLI could be the first provider to use a plugin API if one is built, or it can be added as a built-in provider directly.