feat: Add Copilot support

.editorconfig

@@ -17,4 +17,4 @@ trim_trailing_whitespace = false
 indent_size = 4
 
 [Makefile]
-indent_style = tab
+indent_style = tab

AGENTS.md

@@ -683,6 +683,7 @@ Each provider has a dedicated adapter in `lua/agentic/acp/adapters/`:
 - `opencode_acp_adapter.lua` - OpenCode ACP adapter
 - `cursor_acp_adapter.lua` - Cursor Agent ACP adapter
 - `auggie_acp_adapter.lua` - Auggie ACP adapter
+- `copilot_acp_adapter.lua` - Copilot ACP adapter
 
 These adapters implement provider-specific message formatting, tool call
 handling, and protocol quirks.

README.md

@@ -93,14 +93,15 @@ tools like `nvm`, `fnm`, etc...
 
 **You are free to chose** any installation method you prefer!
 
-| Provider                           | Install                                                                                                                                                       |
-| ---------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| [claude-code-acp][claude-code-acp] | `pnpm add -g @zed-industries/claude-code-acp`<br/> **OR** `npm i -g @zed-industries/claude-code-acp`<br/> **OR** [Download binary][claude-code-acp-releases]  |
-| [gemini-cli][gemini-cli]           | `pnpm add -g @google/gemini-cli`<br/> **OR** `npm i -g @google/gemini-cli`<br/> **OR** `brew install --cask gemini`                                           |
-| [codex-acp][codex-acp]             | `pnpm add -g @zed-industries/codex-acp`<br/> **OR** `npm i -g @zed-industries/codex-acp`<br/> **OR** [Download binary][codex-acp-releases]                    |
-| [opencode][opencode]               | `pnpm add -g opencode-ai`<br/> **OR** `npm i -g opencode-ai`<br/> **OR** `brew install opencode`<br/> **OR** `curl -fsSL https://opencode.ai/install \| bash` |
-| [cursor-agent][cursor-agent]       | `pnpm add -g @blowmage/cursor-agent-acp`<br/> **OR** `npm i -g @blowmage/cursor-agent-acp`                                                                    |
-| [auggie][auggie]                   | `pnpm add -g @augmentcode/auggie`<br/> **OR** `npm i -g @augmentcode/auggie`<br/> **OR** See [Auggie docs][auggie-docs]                                       |
+| Provider                           | Install                                                                                                                                                                    |
+| ---------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| [claude-code-acp][claude-code-acp] | `pnpm add -g @zed-industries/claude-code-acp`<br/> **OR** `npm i -g @zed-industries/claude-code-acp`<br/> **OR** [Download binary][claude-code-acp-releases]               |
+| [gemini-cli][gemini-cli]           | `pnpm add -g @google/gemini-cli`<br/> **OR** `npm i -g @google/gemini-cli`<br/> **OR** `brew install --cask gemini`                                                        |
+| [codex-acp][codex-acp]             | `pnpm add -g @zed-industries/codex-acp`<br/> **OR** `npm i -g @zed-industries/codex-acp`<br/> **OR** [Download binary][codex-acp-releases]                                 |
+| [opencode][opencode]               | `pnpm add -g opencode-ai`<br/> **OR** `npm i -g opencode-ai`<br/> **OR** `brew install opencode`<br/> **OR** `curl -fsSL https://opencode.ai/install \| bash`              |
+| [copilot-cli][copilot-cli]         | `pnpm add -g @github/copilot`<br/> **OR** `npm i -g @github/copilot`<br/> **OR** `brew install copilot-cli`<br/> **OR** `curl -fsSL https://gh.io/copilot-install \| bash` |
+| [cursor-agent][cursor-agent]       | `pnpm add -g @blowmage/cursor-agent-acp`<br/> **OR** `npm i -g @blowmage/cursor-agent-acp`                                                                                 |
+| [auggie][auggie]                   | `pnpm add -g @augmentcode/auggie`<br/> **OR** `npm i -g @augmentcode/auggie`<br/> **OR** See [Auggie docs][auggie-docs]                                                    |
 
 > [!WARNING]  
 > These install commands are here for convenience, please always refer to the
@@ -122,7 +123,7 @@ tools like `nvm`, `fnm`, etc...
   "carlos-algms/agentic.nvim",
 
   opts = {
-    -- Available by default: "claude-acp" | "gemini-acp" | "codex-acp" | "opencode-acp" | "cursor-acp" | "auggie-acp"
+    -- Available by default: "claude-acp" | "gemini-acp" | "codex-acp" | "opencode-acp" | "cursor-acp" | "auggie-acp" | "copilot-acp"
     provider = "claude-acp", -- setting the name here is all you need to get started
   },
 
@@ -748,3 +749,4 @@ the the acknowledgments 😊.
 [cursor-agent]: https://github.com/blowmage/cursor-agent-acp-npm
 [auggie]: https://www.npmjs.com/package/@augmentcode/auggie
 [auggie-docs]: https://docs.augmentcode.com/cli/setup-auggie
+[copilot-cli]: https://github.com/github/copilot-cli

lua/agentic/acp/adapters/copilot_acp_adapter.lua

@@ -0,0 +1,149 @@
+-- FIXIT: Copilot DON'T send modes like plan, ask for edits, etc. We need to remove it from the header and add a notification
+-- FIXIT: Diff is NOT visible when editing
+-- FIXIT: check if it's possible to dedupe the _handle_tool_call_update across adapters
+-- FIXIT: Check it's possible to always update the tool call in the chat widget when there's body, for all adapters
+-- Copilot is sending descriptive message for skill loads, etc, others might also
+
+local ACPClient = require("agentic.acp.acp_client")
+local FileSystem = require("agentic.utils.file_system")
+local Logger = require("agentic.utils.logger")
+
+--- @class agentic.acp.CopilotRawInput
+--- @field path? string file path on the diff tool calls
+--- @field new_str? string new string for edit tool calls
+--- @field old_str? string old string for edit tool calls
+--- @field url? string URL for fetch tool calls
+--- @field skill? string skill name for skill tool calls
+--- @field command? string command for execute tool calls
+--- @field description? string
+
+--- @class agentic.acp.CopilotToolCallMessage : agentic.acp.ToolCallMessage
+--- @field rawInput? agentic.acp.CopilotRawInput
+
+--- Copilot-specific adapter that extends ACPClient with Copilot-specific behaviors
+--- @class agentic.acp.CopilotACPAdapter : agentic.acp.ACPClient
+local CopilotACPAdapter = setmetatable({}, { __index = ACPClient })
+CopilotACPAdapter.__index = CopilotACPAdapter
+
+--- @param config agentic.acp.ACPProviderConfig
+--- @param on_ready fun(client: agentic.acp.ACPClient)
+--- @return agentic.acp.CopilotACPAdapter
+function CopilotACPAdapter:new(config, on_ready)
+    -- Call parent constructor with parent class
+    self = ACPClient.new(ACPClient, config, on_ready)
+
+    -- Re-metatable to child class for proper inheritance chain
+    self = setmetatable(self, CopilotACPAdapter) --[[@as agentic.acp.CopilotACPAdapter]]
+
+    return self
+end
+
+--- @protected
+--- @param session_id string
+--- @param update agentic.acp.CopilotToolCallMessage
+function CopilotACPAdapter:__handle_tool_call(session_id, update)
+    -- expected state, copilot is sending an empty content first, followed by the actual content
+    if not update.rawInput or vim.tbl_isempty(update.rawInput) then
+        return
+    end
+
+    local kind = update.kind
+
+    -- -- Detect sub-agent tasks: Copilot sends these as "think" with subagent_type in rawInput
+    -- if kind == "think" and update.rawInput.subagent_type then
+    --     kind = "SubAgent"
+    -- end
+
+    --- @type agentic.ui.MessageWriter.ToolCallBlock
+    local message = {
+        tool_call_id = update.toolCallId,
+        kind = kind,
+        status = update.status,
+        argument = update.title,
+    }
+
+    if kind == "read" or kind == "edit" then
+        message.argument = FileSystem.to_smart_path(update.rawInput.path)
+
+        if kind == "edit" then
+            local new_string = update.rawInput.new_str or ""
+            local old_string = update.rawInput.old_str or ""
+
+            -- -- Copilot might send content when creating new files
+            -- new_string = update.rawInput.content or new_string
+
+            message.diff = {
+                new = vim.split(new_string, "\n"),
+                old = vim.split(old_string, "\n"),
+                all = false, -- Copilot doesn't send replace_all info ??
+            }
+        elseif not message.argument or message.argument == "" then
+            message.argument = update.title or update.rawInput.path or ""
+        end
+    elseif kind == "execute" then
+        if update.rawInput.command ~= nil then
+            message.argument = update.rawInput.command
+            message.body = {
+                update.title or update.rawInput.description or "",
+            }
+        end
+    elseif kind == "fetch" then
+        if update.rawInput.url ~= nil then
+            message.argument = update.rawInput.url
+            message.body = {
+                update.title or "",
+            }
+        end
+    elseif kind == "other" then
+        if update.rawInput.skill ~= nil then
+            message.kind = "Skill"
+            message.argument = update.rawInput.skill
+        end
+    end
+
+    self:__with_subscriber(session_id, function(subscriber)
+        subscriber.on_tool_call(message)
+    end)
+end
+
+--- @protected
+--- @param session_id string
+--- @param update agentic.acp.ToolCallUpdate
+function CopilotACPAdapter:__handle_tool_call_update(session_id, update)
+    if not update.status then
+        return
+    end
+
+    --- @type agentic.ui.MessageWriter.ToolCallBase
+    local message = {
+        tool_call_id = update.toolCallId,
+        status = update.status,
+    }
+
+    if update.content and update.content[1] then
+        local content = update.content[1]
+
+        if
+            content.type == "content"
+            and content.content
+            and content.content.text
+        then
+            message.body = vim.split(content.content.text, "\n")
+        elseif content.type == "diff" then -- luacheck: ignore 542 -- intentional empty block
+            -- ignore on purpose, diffs come only on tool call, not updates
+        else
+            Logger.debug("Unknown tool call update content type", {
+                content_type = content.type,
+                content = content.content,
+                session_id = session_id,
+                tool_call_id = update.toolCallId,
+            })
+        end
+    end
+
+    self:__with_subscriber(session_id, function(subscriber)
+        subscriber.on_tool_call_update(message)
+    end)
+end
+
+return CopilotACPAdapter

lua/agentic/acp/agent_instance.lua

@@ -66,6 +66,10 @@ function AgentInstance.get_instance(provider_name, on_ready)
         local AuggieACPAdapter =
             require("agentic.acp.adapters.auggie_acp_adapter")
         client = AuggieACPAdapter:new(config, on_ready)
+    elseif provider_name == "copilot-acp" then
+        local CopilotACPAdapter =
+            require("agentic.acp.adapters.copilot_acp_adapter")
+        client = CopilotACPAdapter:new(config, on_ready)
     else
         error("Unsupported ACP provider: " .. provider_name)
     end

lua/agentic/config_default.lua

@@ -4,6 +4,7 @@
 --- | "codex-acp"
 --- | "opencode-acp"
 --- | "cursor-acp"
+--- | "copilot-acp"
 --- | "auggie-acp"
 
 --- @alias agentic.UserConfig.HeaderRenderFn fun(parts: agentic.ui.ChatWidget.HeaderParts): string|nil
@@ -100,6 +101,16 @@ local ConfigDefault = {
             },
             env = {},
         },
+
+        ["copilot-acp"] = {
+            name = "Copilot ACP",
+            command = "copilot",
+            args = {
+                "--acp",
+                "--stdio",
+            },
+            env = {},
+        },
     },
 
     --- @class agentic.UserConfig.Windows.Chat

lua/agentic/session_manager.lua

@@ -574,6 +574,9 @@ function SessionManager:_show_diff_in_buffer(tool_call_id)
     local tracker = tool_call_id
         and self.message_writer.tool_call_blocks[tool_call_id]
 
+    -- FIXIT: Copilot is sending wrong tool call id in the permission request
+    -- instead of tying it to the edit tool call, it always send `write-permission`
+    -- https://github.com/github/copilot-cli/issues/989#issuecomment-3826381550
     if not tracker or tracker.kind ~= "edit" or tracker.diff == nil then
         return
     end