Files
coder/agent/agentcontextconfig/resolve_test.go
Kyle Carberry ee855f9618 feat: make agent context paths configurable via env vars (#23878)
Replace hardcoded paths for instruction files, skills, and MCP config
with
values read from `CODER_AGENT_EXP_*` environment variables. Template
authors
configure paths via the existing `coder_agent` `env` block. The agent
resolves `~`, relative, and absolute paths locally, then serves the
resolved config over `GET /api/v0/context-config`. `chatd` fetches this
once per workspace attach and falls back to today's defaults for older
agents.

All path env vars are comma-separated, allowing multiple directories:

| Env Var | Default | Controls |
|---|---|---|
| `CODER_AGENT_EXP_INSTRUCTIONS_DIRS` | `~/.coder` | Dirs containing the
instruction file |
| `CODER_AGENT_EXP_INSTRUCTIONS_FILE` | `AGENTS.md` | Instruction file
name |
| `CODER_AGENT_EXP_SKILLS_DIRS` | `.agents/skills` | Skills directories
|
| `CODER_AGENT_EXP_SKILL_META_FILE` | `SKILL.md` | Skill metadata file
name |
| `CODER_AGENT_EXP_MCP_CONFIG_FILES` | `.mcp.json` | MCP config files |

### Example

```hcl
resource "coder_agent" "main" {
  os   = "linux"
  arch = "amd64"
  env = {
    CODER_AGENT_EXP_INSTRUCTIONS_DIRS  = "/opt/company/agent-config,~/.coder"
    CODER_AGENT_EXP_INSTRUCTIONS_FILE  = "CLAUDE.md"
    CODER_AGENT_EXP_SKILLS_DIRS        = "/opt/company/ai-skills,.agents/skills"
    CODER_AGENT_EXP_MCP_CONFIG_FILES   = "/opt/company/mcp.json,.mcp.json"
  }
}
```

<details>
<summary>Implementation Details</summary>

### Architecture

Follows the same pattern as MCP tool discovery:
agent resolves locally → exposes via HTTP → chatd consumes.

**Agent-side** (`agent/agentcontextconfig/`):
- `ResolvePath` / `ResolvePaths` handle `~`, relative, and absolute path
forms; returns `""` for relative paths when baseDir is empty
- `Config` reads env vars, falls back to defaults, resolves all paths
- `GET /api/v0/context-config` serves the resolved config as JSON

**chatd-side** (`coderd/x/chatd/`):
- Calls `conn.ContextConfig()` once on first workspace attach
- Falls back to hardcoded defaults on 404 (older agents)
- Iterates instruction dirs, skills dirs using resolved absolute paths
- `LSRelativityRoot` everywhere — no more home/root juggling

### Key design decisions

- **`EXP_` prefix**: env vars use `CODER_AGENT_EXP_*` to indicate
experimental status
- **Plural names**: comma-separated vars use plural names (`DIRS`,
`FILES`); single-value vars use singular (`FILE`)
- **Defaults in `workspacesdk`**: default constants live in
`codersdk/workspacesdk/` so both agent and server reference them without
cross-layer imports
- **`skillMetaFile` persistence**: stored on context-file parts via
`ContextFileSkillMetaFile` and restored on subsequent chat turns so
custom values survive across turns
- **Working dir dedup**: `slices.Contains` guard prevents reading the
same instruction file from both `InstructionsDirs` and the working
directory
- **MCP server dedup**: first-occurrence-wins dedup prevents leaking
duplicate connections from overlapping config files
- **ResolvePath safety**: returns `""` for relative paths when `baseDir`
is empty, so `ResolvePaths` filters them out

### Files changed

| File | Change |
|---|---|
| `agent/agentcontextconfig/` | New package — path resolution + HTTP
endpoint |
| `codersdk/workspacesdk/agentconn.go` | `ContextConfigResponse` type,
default constants, client method |
| `agent/agent.go` + `agent/api.go` | Wire up endpoint, pass config to
MCP |
| `agent/x/agentmcp/manager.go` | Accept `[]string` MCP config paths,
dedup by name |
| `coderd/x/chatd/chatd.go` | Fetch config, thread through, named
returns |
| `coderd/x/chatd/instruction.go` | Accept configurable dir + file name,
`skillMetaFileFromParts` |
| `coderd/x/chatd/chattool/skill.go` | Accept configurable dirs + meta
file |
| `codersdk/chats.go` | `ContextFileSkillMetaFile` field for persistence
|

### Test coverage

- `TestConfig` (4 cases): defaults, custom env vars, whitespace
trimming, comma-separated dirs
- `TestResolvePath` / `TestResolvePaths`: including empty baseDir edge
case
- `TestPersistInstructionFilesFallbackOnOlderAgent`: backward-compat
path when `ContextConfig` returns 404
- `TestChatMessagePartVariantTags`: updated exclusion list for new
internal field

### Backward compatibility

Older agents return 404 for the new endpoint. `chatd` catches this and
falls back to today's defaults via `readHomeInstructionFile` (using
`LSRelativityHome`). Existing workspaces work with no changes.

</details>
2026-04-01 12:28:47 -04:00

153 lines
4.6 KiB
Go

package agentcontextconfig_test
import (
"path/filepath"
"runtime"
"testing"
"github.com/stretchr/testify/require"
"github.com/coder/coder/v2/agent/agentcontextconfig"
)
// platformAbsPath constructs an absolute path that is valid
// on the current platform. On Windows paths must include a
// drive letter to be considered absolute.
func platformAbsPath(parts ...string) string {
if runtime.GOOS == "windows" {
return `C:\` + filepath.Join(parts...)
}
return "/" + filepath.Join(parts...)
}
func TestResolvePath(t *testing.T) { //nolint:tparallel // subtests using t.Setenv cannot be parallel
t.Run("EmptyInput", func(t *testing.T) {
t.Parallel()
require.Equal(t, "", agentcontextconfig.ResolvePath("", platformAbsPath("base")))
})
t.Run("WhitespaceOnly", func(t *testing.T) {
t.Parallel()
require.Equal(t, "", agentcontextconfig.ResolvePath(" ", platformAbsPath("base")))
})
// Tests that use t.Setenv cannot be parallel.
t.Run("TildeAlone", func(t *testing.T) {
fakeHome := t.TempDir()
t.Setenv("HOME", fakeHome)
t.Setenv("USERPROFILE", fakeHome)
got := agentcontextconfig.ResolvePath("~", platformAbsPath("base"))
require.Equal(t, fakeHome, got)
})
t.Run("TildeSlashPath", func(t *testing.T) {
fakeHome := t.TempDir()
t.Setenv("HOME", fakeHome)
t.Setenv("USERPROFILE", fakeHome)
got := agentcontextconfig.ResolvePath("~/docs/readme", platformAbsPath("base"))
require.Equal(t, filepath.Join(fakeHome, "docs", "readme"), got)
})
t.Run("AbsolutePath", func(t *testing.T) {
t.Parallel()
p := platformAbsPath("etc", "coder")
got := agentcontextconfig.ResolvePath(p, platformAbsPath("base"))
require.Equal(t, p, got)
})
t.Run("RelativePath", func(t *testing.T) {
t.Parallel()
base := platformAbsPath("work")
got := agentcontextconfig.ResolvePath("foo/bar", base)
require.Equal(t, filepath.Join(base, "foo", "bar"), got)
})
t.Run("RelativePathWithWhitespace", func(t *testing.T) {
t.Parallel()
base := platformAbsPath("work")
got := agentcontextconfig.ResolvePath(" foo/bar ", base)
require.Equal(t, filepath.Join(base, "foo", "bar"), got)
})
t.Run("RelativePathWithEmptyBaseDir", func(t *testing.T) {
t.Parallel()
got := agentcontextconfig.ResolvePath(".agents/skills", "")
require.Equal(t, "", got)
})
}
func TestResolvePath_HomeUnset(t *testing.T) {
// Cannot be parallel — modifies HOME env var.
t.Setenv("HOME", "")
// Also clear USERPROFILE for Windows compatibility.
t.Setenv("USERPROFILE", "")
require.Equal(t, "", agentcontextconfig.ResolvePath("~", platformAbsPath("base")))
require.Equal(t, "", agentcontextconfig.ResolvePath("~/docs", platformAbsPath("base")))
}
func TestResolvePaths(t *testing.T) { //nolint:tparallel // subtests using t.Setenv cannot be parallel
t.Run("EmptyString", func(t *testing.T) {
t.Parallel()
require.Nil(t, agentcontextconfig.ResolvePaths("", platformAbsPath("base")))
})
t.Run("WhitespaceOnly", func(t *testing.T) {
t.Parallel()
require.Nil(t, agentcontextconfig.ResolvePaths(" ", platformAbsPath("base")))
})
t.Run("SingleEntry", func(t *testing.T) {
t.Parallel()
p := platformAbsPath("abs", "path")
got := agentcontextconfig.ResolvePaths(p, platformAbsPath("base"))
require.Equal(t, []string{p}, got)
})
// Tests that use t.Setenv cannot be parallel.
t.Run("MultipleEntries", func(t *testing.T) {
fakeHome := t.TempDir()
t.Setenv("HOME", fakeHome)
t.Setenv("USERPROFILE", fakeHome)
b := platformAbsPath("b")
base := platformAbsPath("base")
got := agentcontextconfig.ResolvePaths("~/a,"+b+",rel", base)
require.Equal(t, []string{
filepath.Join(fakeHome, "a"),
b,
filepath.Join(base, "rel"),
}, got)
})
t.Run("TrimsWhitespace", func(t *testing.T) {
t.Parallel()
a := platformAbsPath("a")
b := platformAbsPath("b")
got := agentcontextconfig.ResolvePaths(" "+a+" , "+b+" ", platformAbsPath("base"))
require.Equal(t, []string{a, b}, got)
})
t.Run("SkipsEmptyEntries", func(t *testing.T) {
t.Parallel()
a := platformAbsPath("a")
b := platformAbsPath("b")
got := agentcontextconfig.ResolvePaths(a+",,"+b+",", platformAbsPath("base"))
require.Equal(t, []string{a, b}, got)
})
t.Run("TrailingComma", func(t *testing.T) {
t.Parallel()
p := platformAbsPath("only")
got := agentcontextconfig.ResolvePaths(p+",", platformAbsPath("base"))
require.Equal(t, []string{p}, got)
})
t.Run("RelativePathSkippedWhenBaseDirEmpty", func(t *testing.T) {
fakeHome := t.TempDir()
t.Setenv("HOME", fakeHome)
t.Setenv("USERPROFILE", fakeHome)
got := agentcontextconfig.ResolvePaths("~/.coder,.agents/skills", "")
require.Equal(t, []string{filepath.Join(fakeHome, ".coder")}, got)
})
}