[Bug]: OpenAI-compatible adapter doesn't work with some API providers due to not handling empty content fields

[reissbaker]

Your minimal.lua config

---@diagnostic disable: missing-fields

--NOTE: Set config path to enable the copilot adapter to work.
--It will search the follwoing paths for the for copilot token:
--  - "$CODECOMPANION_TOKEN_PATH/github-copilot/hosts.json"
--  - "$CODECOMPANION_TOKEN_PATH/github-copilot/apps.json"
vim.env["CODECOMPANION_TOKEN_PATH"] = vim.fn.expand("~/.config")

vim.env.LAZY_STDPATH = ".repro"
load(vim.fn.system("curl -s https://raw.githubusercontent.com/folke/lazy.nvim/main/bootstrap.lua"))()

-- Your CodeCompanion setup
local plugins = {
  {
    "olimorris/codecompanion.nvim",
    dependencies = {
      { "nvim-treesitter/nvim-treesitter", build = ":TSUpdate" },
      { "nvim-lua/plenary.nvim" },
      { "hrsh7th/nvim-cmp" },
      { "stevearc/dressing.nvim", opts = {} },
      { "nvim-telescope/telescope.nvim" },
    },
    opts = {
      --Refer to: https://github.com/olimorris/codecompanion.nvim/blob/main/lua/codecompanion/config.lua
      strategies = {
        --NOTE: Change the adapter as required
        chat = { adapter = "openai_compatible" },
        inline = { adapter = "copilot" },
      },
      opts = {
        log_level = "DEBUG",
      },
      adapters = {
        openai_compatible = function()
          return require("codecompanion.adapters").extend("openai_compatible", {
            env = {
              url = "https://glhf.chat",
              api_key = "GLHF_API_KEY",
              chat_url = "/api/openai/v1/chat/completions",
            },
            schema = {
              model = {
                default = "hf:Qwen/Qwen2.5-Coder-32B-Instruct",
              },
              num_ctx = {
                default = 32768,
              },
            },
          })
        end,
      },
    },
  },
}

require("lazy.minit").repro({ spec = plugins })

-- Setup Tree-sitter
local ts_status, treesitter = pcall(require, "nvim-treesitter.configs")
if ts_status then
  treesitter.setup({
    ensure_installed = { "lua", "markdown", "markdown_inline", "yaml" },
    highlight = { enable = true },
  })
end

-- Setup completion
local cmp_status, cmp = pcall(require, "cmp")
if cmp_status then
  cmp.setup({
    mapping = cmp.mapping.preset.insert({
      ["<C-b>"] = cmp.mapping.scroll_docs(-4),
      ["<C-f>"] = cmp.mapping.scroll_docs(4),
      ["<C-Space>"] = cmp.mapping.complete(),
      ["<C-e>"] = cmp.mapping.abort(),
      ["<CR>"] = cmp.mapping.confirm({ select = true }),
      -- Accept currently selected item. Set `select` to `false` to only confirm explicitly selected items.
    }),
  })
end

Error messages

No error messages, just a borked chat history where user and assistant messages aren't correctly separated.

Log output

Seems empty?

Health check output

Describe the bug

What I expect to happen:

The user and assistant messages are properly separated and the headers appear

What actually happens:

FYI, this is due to some OpenAI-compatible API providers returning an empty content field for some deltas; CodeCompanion already handles nil role fields, but not nil content fields in deltas. I have a fork with a fix and am happy to make a PR, it's a small change! Opening this issue first as per the CONTRIBUTING.md.

Reproduce the bug

1. Get an API key from Fireworks or GLHF.chat
2. Use it for the OpenAI-compatible API provider
3. CodeCompanion will break

Final checks

• [X] I have made sure this issue exists in the latest version of the plugin
• [X] I have tested with the minimal.lua file from above and have shared this
• [X] I have shared the contents of the log file