Feat: Add --config CLI flag to specify custom config file path #2066

Summary

Currently, opencode supports specifying a custom config file path via the OPENCODE_CONFIG environment variable. It would be more convenient and intuitive to also support this functionality through a CLI flag like --config.

Current Behavior

To use a custom config file, users must set an environment variable:

export OPENCODE_CONFIG=/path/to/my/custom-config.json
opencode run "Hello world"

Proposed Enhancement

Add a --config CLI flag that accepts a file path:

opencode --config /path/to/my/custom-config.json run "Hello world"
opencode --config ./project-specific-config.jsonc run "Implement feature X"

Benefits

1. Better UX: More discoverable through --help and follows common CLI conventions
2. Per-command flexibility: Easier to use different configs for different commands without managing environment variables
3. Script-friendly: Cleaner in shell scripts and CI/CD pipelines
4. Consistency: Aligns with how most CLI tools handle config file specification

Implementation Notes

• The CLI flag should take precedence over the OPENCODE_CONFIG environment variable (or have the same precedence)
• Should maintain backward compatibility with the existing environment variable approach
• The flag should accept both absolute and relative paths
• Should support both .json and .jsonc formats like the current implementation

Current Config Loading Hierarchy

For reference, the current precedence order is:

1. OPENCODE_CONFIG environment variable (highest)
2. Project-level configs (.opencode/opencode.jsonc, etc.)
3. Global configs (~/.config/opencode/opencode.jsonc, etc.)

The new --config flag should either match the precedence of OPENCODE_CONFIG or take even higher precedence.

Related Files

• packages/tui/cmd/opencode/main.go - CLI flag definitions
• packages/opencode/src/config/config.ts - Config loading logic
• packages/opencode/src/flag/flag.ts - Flag processing

Notes

Letting AI write my issues seems like cheating, but also appropriate in this repo. If not, sorry.