fix(adapters): conform to standard tool structure (#3077)

Author: olimorris

.codecompanion/adapters/adapters.md

@@ -108,6 +108,25 @@ This structure provides clear separation of concerns:
 - **response**: Pure transformations for parsing responses (chat, inline, tokens)
 - **tools**: Tool-specific operations (formatting calls and responses)
 
+### Canonical Tool-Result Shape
+
+Tool result messages produced by `format_response` are stored in `chat.messages` and re-read by every adapter's `build_messages`/`form_messages`. To keep messages portable across adapters, every adapter must write to the same canonical shape:
+
+```lua
+{
+  role    = "tool",
+  content = output,
+  tools = {
+    call_id = tool_call.id,                  -- required: matches the LLM's tool call
+    name    = tool_call["function"].name,    -- required: function name (Gemini uses this)
+    is_error = false,                        -- optional: Anthropic uses this
+  },
+  opts = { visible = false },
+}
+```
+
+Adapter-specific extras (e.g. OpenAI Responses' `id`) are allowed but ignored by other adapters. When reading these messages back, an adapter should treat any message with `role == "tool"` as a tool result — never gate on adapter-specific fields.
+
 ### Calling Handlers
 
 Throughout CodeCompanion, handlers are called using the `adapters.call_handler()` function, which provides backwards compatibility:

lua/codecompanion/adapters/http/anthropic.lua

@@ -245,14 +245,13 @@ return {
         -- 6. Treat 'tool' role as user and convert tool results to Anthropic format
         if m.role == "tool" then
           m.role = self.roles.user
-          -- Convert tool result from CodeCompanion format to Anthropic format
-          if m.tools and m.tools.type == "tool_result" then
+          if m.tools then
             -- Handle content that might already be in Anthropic's format
             if type(m.content) == "table" and m.content.type == "tool_result" then
               -- Already in Anthropic format, keep it as-is but ensure it's in an array
               m.content = { m.content }
             else
-              -- Convert from CodeCompanion format to Anthropic format
+              -- Convert from the canonical tool-result shape to Anthropic's format
               m.content = {
                 {
                   type = "tool_result",
@@ -624,9 +623,9 @@ return {
           role = "tool",
           content = output,
           tools = {
-            type = "tool_result",
             call_id = tool_call.id,
             is_error = false,
+            name = tool_call["function"].name,
           },
           -- Chat Buffer option: To tell the chat buffer that this shouldn't be visible
           opts = { visible = false },
@@ -667,7 +666,7 @@ return {
         ["claude-haiku-4-5"] = {
           formatted_name = "Claude Haiku 4.5",
           meta = { context_window = 200000, max_tokens = 64000 },
-          opts = { can_reason = true, has_vision = true },
+          opts = { can_reason = false, has_vision = true },
         },
 
         -- Legacy models

lua/codecompanion/adapters/http/openai.lua

@@ -363,6 +363,7 @@ return {
           role = self.roles.tool or "tool",
           tools = {
             call_id = tool_call.id,
+            name = tool_call["function"].name,
           },
           content = output,
           opts = { visible = false },

lua/codecompanion/adapters/http/openai_responses.lua

@@ -573,8 +573,9 @@ return {
         return {
           role = self.roles.tool or "tool",
           tools = {
-            id = tool_call.id,
             call_id = tool_call.call_id,
+            id = tool_call.id,
+            name = tool_call["function"].name,
           },
           content = output,
           opts = { visible = false },

lua/codecompanion/interactions/chat/init.lua

@@ -701,12 +701,33 @@ end
 ---Change the adapter in the chat buffer
 ---@param adapter string
 ---@param cb? function
+---@return boolean swapped Whether the adapter was actually swapped
 function Chat:change_adapter(adapter, cb)
   local function fire()
     return utils.fire("ChatAdapter", { bufnr = self.bufnr, adapter = adapters.make_safe(self.adapter) })
   end
 
-  self.adapter = require("codecompanion.adapters").resolve(adapter)
+  local new_adapter = require("codecompanion.adapters").resolve(adapter)
+
+  -- Block adapter swaps once tool calls or reasoning have happened. Adapter-
+  -- specific state (tool-call signatures, encrypted reasoning blobs) cannot
+  -- be carried into a different vendor's API. Model swaps within the same
+  -- adapter are unaffected.
+  if self.adapter.name ~= new_adapter.name then
+    local has_state = vim.iter(self.messages or {}):any(function(m)
+      return m.reasoning ~= nil or (m.tools and m.tools.calls ~= nil)
+    end)
+    if has_state then
+      utils.notify(
+        fmt("Adapter cannot be changed after tool executions. Start a new chat to use `%s`", new_adapter.name),
+        vim.log.levels.WARN
+      )
+      return false
+    end
+  end
+
+  self.acp_connection = nil
+  self.adapter = new_adapter
   self.ui.adapter = self.adapter
 
   if self.adapter.type == "acp" then
@@ -722,6 +743,7 @@ function Chat:change_adapter(adapter, cb)
   self:update_metadata()
   self:apply_settings()
   fire()
+  return true
 end
 
 ---Set a model in the chat buffer

lua/codecompanion/interactions/chat/keymaps/change_adapter.lua

@@ -244,7 +244,6 @@ function M.callback(chat)
     end
 
     if current_adapter ~= selected_adapter then
-      chat.acp_connection = nil -- Ensure we reset this
       chat:change_adapter(selected_adapter, on_adapter_ready)
     else
       return on_adapter_ready()

tests/adapters/http/test_openai.lua

@@ -156,6 +156,7 @@ T["OpenAI adapter"]["can output tool call"] = function()
     role = "tool",
     tools = {
       call_id = "call_RJU6xfk0OzQF3Gg9cOFS5RY7",
+      name = "weather",
     },
   }, adapter.handlers.tools.output_response(adapter, tool_call, output))
 end

tests/adapters/http/test_openai_responses.lua

@@ -57,8 +57,9 @@ T["Responses"]["can output tool calls"] = function()
     },
     role = "tool",
     tools = {
-      id = "fc_0cf9af0f913994140068e27139a1948193bbf214a9664ec92c",
       call_id = "call_a9oyUMlFhnX8HvqzlfIx5Uek",
+      id = "fc_0cf9af0f913994140068e27139a1948193bbf214a9664ec92c",
+      name = "weather",
     },
   }, adapter.handlers.tools.format_response(adapter, tool_call, output))
 end