## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work.
> - Local agents run through the `claude_local` adapter, which spawns
Claude Code and routes its Anthropic API traffic through a shared proxy
(e.g. better-ccflare).
> - That proxy's request log feeds observability dashboards that break
down cost and token usage.
> - But requests from local agents arrive without an agent identifier,
so all traffic collapses into a single unattributed bucket and per-agent
telemetry is impossible.
> - Anthropic's CLI forwards `ANTHROPIC_CUSTOM_HEADERS` onto each API
request, and better-ccflare now reads an `X-Anthropic-Agent-Id` header
to attribute requests per agent.
> - This pull request stamps the agent's id into
`ANTHROPIC_CUSTOM_HEADERS` as `X-Anthropic-Agent-Id`, injected into the
env the adapter actually forwards to the spawned process.
> - The benefit is per-agent cost/token attribution in proxy-backed
dashboards, with zero impact on agents that don't run behind such a
proxy.
## Linked Issues or Issue Description
No public GitHub issue exists; describing inline per CONTRIBUTING.md
(feature template).
**Problem or motivation**
When several `claude_local` agents share a proxy (better-ccflare) in
front of the Anthropic API, the proxy cannot tell which agent issued a
given request. Per-agent cost and token dashboards therefore can't be
built — every request is attributed to one undifferentiated bucket.
**Proposed solution**
Have the `claude_local` adapter stamp each spawned Claude Code process
with `ANTHROPIC_CUSTOM_HEADERS: X-Anthropic-Agent-Id: <agentId>`. The
Anthropic CLI forwards that header on every API call, so the proxy can
attribute requests to the specific agent.
**Alternatives considered**
Parsing per-agent identity from workspace paths or session ids in the
proxy — brittle and proxy-specific. A first-class request header is the
stable contract; it pairs with better-ccflare's `X-Anthropic-Agent-Id`
support
([tombii/better-ccflare#260](https://github.com/tombii/better-ccflare/pull/260))
and dashboards like
[danieltamas/axon](https://github.com/danieltamas/axon).
**Roadmap alignment**
Additive observability glue for an existing adapter; no overlap with
planned core work.
## What Changed
- Added `server/src/adapters/claude-agent-id-header.ts` exporting
`stampClaudeAgentIdHeader`, which wraps the `claude_local` execute and
merges `X-Anthropic-Agent-Id: <agentId>` into the run's
`config.env.ANTHROPIC_CUSTOM_HEADERS`.
- `server/src/adapters/registry.ts`: the `claude_local` adapter now uses
the wrapped execute (`stampClaudeAgentIdHeader(claudeExecute)`).
- The header is merged into **`config.env`** — the env the Claude
adapter actually forwards into the spawned process — rather than
`agent.adapterConfig.env`, which is resolved upstream before `execute`
runs and is never read by the Claude adapter.
- `agentId` is sanitized (CR/LF stripped, capped at 256 chars) before
interpolation to prevent HTTP header injection.
- Passthrough when no agent id is available; a pre-existing
`X-Anthropic-Agent-Id` (manual override) is respected and not
duplicated.
- Added `server/src/adapters/claude-agent-id-header.test.ts` covering
injection into `config.env`, append-to-existing
`ANTHROPIC_CUSTOM_HEADERS`, CR/LF sanitization, length bounding,
no-agent-id passthrough, and the duplicate-header guard.
## Verification
- Unit tests: `cd server && npx vitest run
src/adapters/claude-agent-id-header.test.ts` → 6 passing.
- CI: typecheck, build, server suites, and Greptile gates run on this
PR.
- Manual: configure a `claude_local` agent behind better-ccflare, run a
heartbeat, and confirm the proxy log shows `X-Anthropic-Agent-Id:
<agentId>` on that agent's requests. An agent that already sets
`X-Anthropic-Agent-Id` in its adapter config keeps its override (no
duplicate line).
## Risks
Low risk. The change is additive and non-breaking:
- When no agent id is present, or when an `X-Anthropic-Agent-Id` is
already configured, execution is byte-for-byte unchanged (the original
`ctx` is passed straight through).
- The header only has an effect for deployments whose proxy reads it;
agents without such a proxy are unaffected.
- The agent id is sanitized (CR/LF removed, length-bounded) before it is
interpolated into a header value, preventing header injection.
> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. This is additive
observability glue for an existing adapter and does not overlap planned
core work.
## Model Used
Claude (Anthropic) — Claude Opus 4.8 (`claude-opus-4-8`), via the Claude
Code CLI with extended reasoning and tool use.
## 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] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots (N/A — no UI 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
---------
Co-authored-by: zenprocess <zenprocess@users.noreply.github.com>
Co-authored-by: Devin Foley <devin@paperclip.ing>
Co-authored-by: Paperclip <noreply@paperclip.ing>
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