## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work.
> - The server config loader reads `.paperclip/config.json` and feeds it
into the shared Paperclip config schema.
> - When a config file exists but cannot be parsed or fails schema
validation, Paperclip should not silently ignore it.
> - The current `readConfigFile()` catch block treats invalid files the
same as missing files, so startup falls back to defaults while the
banner can still point at the ignored config path.
> - This pull request keeps the missing-file fallback, but makes present
invalid config files fail with a path-specific error.
> - The benefit is safer startup behavior and a clear diagnostic that
points at the invalid config field.
## Linked Issues or Issue Description
Fixes#8908
## What Changed
- Changed `readConfigFile()` to return `null` only when the config file
is absent.
- Added explicit errors for unreadable/invalid JSON config files.
- Added explicit Zod validation errors that include the config path and
invalid field path without printing config contents.
- Added server tests for missing config, invalid JSON, schema validation
failure, and valid config parsing.
## Verification
- `pnpm exec vitest run server/src/__tests__/config-file.test.ts`
- `pnpm --filter @paperclipai/server typecheck`
## Risks
Low risk for valid configs and missing configs. This intentionally
changes behavior for present invalid config files from silent fallback
to startup failure, which is the issue being fixed.
> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.
## Model Used
OpenAI Codex based on GPT-5, with repository file inspection, GitHub
CLI, and local command execution.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
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