fix(harness): resolve runtime paths from project root (#2642)

* fix(harness): resolve runtime paths from project root

* docs(config): update

* fix(config): address runtime path review feedback

* test(config): fix skills path e2e root

* test(config): cover legacy config fallback when project root lacks config files

Verifies that when DEER_FLOW_PROJECT_ROOT is unset and cwd has no
config.yaml/extensions_config.json, AppConfig and ExtensionsConfig fall back
to the legacy backend/repo-root candidates — the backward-compat path
requested in PR #2642 review.

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/docs/CONFIGURATION.md

@@ -321,12 +321,16 @@ models:
 - `DEEPSEEK_API_KEY` - DeepSeek API key
 - `NOVITA_API_KEY` - Novita API key (OpenAI-compatible endpoint)
 - `TAVILY_API_KEY` - Tavily search API key
+- `DEER_FLOW_PROJECT_ROOT` - Project root for relative runtime paths
 - `DEER_FLOW_CONFIG_PATH` - Custom config file path
+- `DEER_FLOW_EXTENSIONS_CONFIG_PATH` - Custom extensions config file path
+- `DEER_FLOW_HOME` - Runtime state directory (defaults to `.deer-flow` under the project root)
+- `DEER_FLOW_SKILLS_PATH` - Skills directory when `skills.path` is omitted
 - `GATEWAY_ENABLE_DOCS` - Set to `false` to disable Swagger UI (`/docs`), ReDoc (`/redoc`), and OpenAPI schema (`/openapi.json`) endpoints (default: `true`)
 
 ## Configuration Location
 
-The configuration file should be placed in the **project root directory** (`deer-flow/config.yaml`), not in the backend directory.
+The configuration file should be placed in the **project root directory** (`deer-flow/config.yaml`). Set `DEER_FLOW_PROJECT_ROOT` when the process may start from another working directory, or set `DEER_FLOW_CONFIG_PATH` to point at a specific file.
 
 ## Configuration Priority
 
@@ -334,12 +338,12 @@ DeerFlow searches for configuration in this order:
 
 1. Path specified in code via `config_path` argument
 2. Path from `DEER_FLOW_CONFIG_PATH` environment variable
-3. `config.yaml` in current working directory (typically `backend/` when running)
-4. `config.yaml` in parent directory (project root: `deer-flow/`)
+3. `config.yaml` under `DEER_FLOW_PROJECT_ROOT`, or under the current working directory when `DEER_FLOW_PROJECT_ROOT` is unset
+4. Legacy backend/repository-root locations for monorepo compatibility
 
 ## Best Practices
 
-1. **Place `config.yaml` in project root** - Not in `backend/` directory
+1. **Place `config.yaml` in project root** - Set `DEER_FLOW_PROJECT_ROOT` if the runtime starts elsewhere
 2. **Never commit `config.yaml`** - It's already in `.gitignore`
 3. **Use environment variables for secrets** - Don't hardcode API keys
 4. **Keep `config.example.yaml` updated** - Document all new options
@@ -350,7 +354,7 @@ DeerFlow searches for configuration in this order:
 
 ### "Config file not found"
 - Ensure `config.yaml` exists in the **project root** directory (`deer-flow/config.yaml`)
-- The backend searches parent directory by default, so root location is preferred
+- If the runtime starts outside the project root, set `DEER_FLOW_PROJECT_ROOT`
 - Alternatively, set `DEER_FLOW_CONFIG_PATH` environment variable to custom location
 
 ### "Invalid API key"
@@ -360,7 +364,7 @@ DeerFlow searches for configuration in this order:
 ### "Skills not loading"
 - Check that `deer-flow/skills/` directory exists
 - Verify skills have valid `SKILL.md` files
-- Check `skills.path` configuration if using custom path
+- Check `skills.path` or `DEER_FLOW_SKILLS_PATH` if using a custom path
 
 ### "Docker sandbox fails to start"
 - Ensure Docker is running

backend/docs/SETUP.md

@@ -23,6 +23,9 @@ DeerFlow uses a YAML configuration file that should be placed in the **project r
    # Option A: Set environment variables (recommended)
    export OPENAI_API_KEY="your-key-here"
 
+   # Optional: pin the project root when running from another directory
+   export DEER_FLOW_PROJECT_ROOT="/path/to/deer-flow"
+
    # Option B: Edit config.yaml directly
    vim config.yaml  # or your preferred editor
    ```
@@ -35,17 +38,20 @@ DeerFlow uses a YAML configuration file that should be placed in the **project r
 
 ## Important Notes
 
-- **Location**: `config.yaml` should be in `deer-flow/` (project root), not `deer-flow/backend/`
+- **Location**: `config.yaml` should be in `deer-flow/` (project root)
 - **Git**: `config.yaml` is automatically ignored by git (contains secrets)
-- **Priority**: If both `backend/config.yaml` and `../config.yaml` exist, backend version takes precedence
+- **Runtime root**: Set `DEER_FLOW_PROJECT_ROOT` if DeerFlow may start from outside the project root
+- **Runtime data**: State defaults to `.deer-flow` under the project root; set `DEER_FLOW_HOME` to move it
+- **Skills**: Skills default to `skills/` under the project root; set `DEER_FLOW_SKILLS_PATH` or `skills.path` to move them
 
 ## Configuration File Locations
 
 The backend searches for `config.yaml` in this order:
 
-1. `DEER_FLOW_CONFIG_PATH` environment variable (if set)
-2. `backend/config.yaml` (current directory when running from backend/)
-3. `deer-flow/config.yaml` (parent directory - **recommended location**)
+1. Explicit `config_path` argument from code
+2. `DEER_FLOW_CONFIG_PATH` environment variable (if set)
+3. `config.yaml` under `DEER_FLOW_PROJECT_ROOT`, or the current working directory when `DEER_FLOW_PROJECT_ROOT` is unset
+4. Legacy backend/repository-root locations for monorepo compatibility
 
 **Recommended**: Place `config.yaml` in project root (`deer-flow/config.yaml`).
 
@@ -77,8 +83,8 @@ python -c "from deerflow.config.app_config import AppConfig; print(AppConfig.res
 
 If it can't find the config:
 1. Ensure you've copied `config.example.yaml` to `config.yaml`
-2. Verify you're in the correct directory
-3. Check the file exists: `ls -la ../config.yaml`
+2. Verify you're in the project root, or set `DEER_FLOW_PROJECT_ROOT`
+3. Check the file exists: `ls -la config.yaml`
 
 ### Permission denied
 
@@ -89,4 +95,4 @@ chmod 600 ../config.yaml  # Protect sensitive configuration
 ## See Also
 
 - [Configuration Guide](CONFIGURATION.md) - Detailed configuration options
-- [Architecture Overview](../CLAUDE.md) - System architecture
+- [Architecture Overview](../CLAUDE.md) - System architecture