## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work.
> - The Claude local adapter lets operators select a Claude model for an
agent.
> - Claude Fable 5.1 was absent from the adapter model lists.
> - The adapter runtime also used a Claude Code build that rejected
Fable 5.1.
> - This pull request adds the direct Anthropic ID and the AWS Bedrock
inference profile ID.
> - It also updates the Claude ACP runtime and keeps the Paperclip usage
and isolation patches.
> - The benefit is that operators can select and run Claude Fable 5.1
through the Claude adapter.
## Linked Issues or Issue Description
Refs #8810. That issue covers related model ID handling. This change
does not change provider-prefixed model IDs.
**Agent or provider**
Claude Code through the built-in `claude_local` adapter. The requested
model is Claude Fable 5.1.
**Why this adapter is useful**
Operators can use Fable 5.1 without entering an undocumented model ID.
The configured model also reaches both supported Claude execution lanes.
**How the agent is invoked**
The CLI lane sends `--model claude-fable-5-1`. The ACP lane sends
`ANTHROPIC_MODEL=claude-fable-5-1` to
`@agentclientprotocol/claude-agent-acp`.
**Are you willing to implement it?**
Yes. This pull request includes the implementation and tests.
**Additional context**
Claude Code 2.1.232 rejected Fable 5.1 and required version 2.1.251 or
newer. ACP package 0.73.0 includes Claude Code 2.1.257. The update keeps
Paperclip's usage metadata and isolated-context behavior.
## What Changed
- Added `claude-fable-5-1` to the direct Claude fallback list.
- Added `us.anthropic.claude-fable-5-1` to the AWS Bedrock list.
- Kept the existing default model at the first position in each list.
- Updated the Claude ACP dependency from 0.70 to 0.73.
- Carried the Paperclip usage and isolated-context changes into the 0.73
patch.
- Added a Claude Code 2.1.251 minimum-version preflight for Fable 5.1
when using the standard `claude` executable, surfaced in both adapter
Test and execution. Explicit custom wrappers retain their existing
compatibility contract.
- Kept local adapter Tests from executing caller-selected binaries: when
runtime `PATH` selects a different Claude executable than the trusted
probe, the Test warns and defers the authoritative version check to
execution instead of approving or rejecting the alternate installation.
- Added tests for model listing, discovery deduplication, Bedrock
filtering, model pass-through in both execution lanes, old-CLI rejection
before launch, custom-wrapper compatibility, and local runtime-PATH
mismatch handling.
## Verification
- `pnpm --filter @paperclipai/adapter-claude-local typecheck`
- `pnpm exec vitest run
packages/adapters/claude-local/src/server/execute.remote.test.ts
packages/adapters/claude-local/src/server/test.remote.test.ts
packages/adapters/claude-local/src/server/test.probe.test.ts
packages/adapters/claude-local/src/server/acp.test.ts
server/src/__tests__/adapter-models.test.ts` (72 tests passed)
- `node --test scripts/acpx-patch-packaging.test.mjs` (13 tests passed)
- `pnpm -r typecheck`
- `pnpm build`
- A local Paperclip agent run completed with `usageJson.model` set to
`claude-fable-5-1` through ACP 0.73.0 and its bundled Claude Code
2.1.257.
- `pnpm test:run` completed 5,638 passing tests and 24 skipped tests. It
also found 24 failures in unrelated workspace-runtime,
path-canonicalization, and runtime-exposure tests on macOS with Node 26.
These failures do not touch this diff. Clean pull request CI is the
final full-suite gate.
## Risks
- The ACP dependency update can change Claude runtime behavior outside
model selection. Focused ACP tests, the full typecheck, the production
build, and a real local Fable run reduce this risk.
- The 0.73 patch must stay aligned with the installed ACP version.
Dependency-resolution CI verifies the manifest and patch pair.
- Fable 5.1 adds a short `claude --version` preflight to standard
CLI-lane Tests and runs. The result is intentionally not cached so an
in-place Claude Code upgrade takes effect without restarting Paperclip.
Explicit custom wrappers are not version-probed because their output and
compatibility contract can differ from the standard executable.
- Local Tests preserve the existing deny-by-default probe boundary and
do not execute a binary selected by caller-controlled `PATH`. A
mismatched runtime binary produces an explicit warning without blocking
an otherwise valid setup; execution independently validates the actual
runtime-selected CLI before launch.
- The AWS Bedrock identifier differs from earlier IDs because Fable 5.1
has no `-v1` suffix. The model-list test locks this exact value.
- There is no schema change or migration.
> 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
Provider: OpenAI. Model: GPT-5 Codex. The host did not expose a more
specific model ID or context-window size. Capabilities used: agentic
reasoning, repository editing, shell execution, web research, and local
runtime verification.
## 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
- [x] All Paperclip CI gates are green
- [x] 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: Paperclip <noreply@paperclip.ing>
Michael Nguyen