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Bernstein vs Aider: quick decision guide
Aider is the original open-source coding agent. Talks to ~50 LLM providers via LiteLLM, commits each change to git automatically, ships a repo-map for context. Apache-2.0, 30k+ stars.
Page built on 2026-05-18 from data/adapters-meta.json. Every claim below links to its primary source.
Install both
Aider
pip install aider-chatBernstein
pipx install bernsteinApache-2.0. Deterministic Python scheduler.
Feature matrix
| Capability | Aider | Bernstein |
|---|---|---|
| Install method | pip install aider-chat | pipx install bernstein |
| License | Apache-2.0 | Apache-2.0 |
| Authentication | Provider API key (anthropic / openai / openrouter / etc.) | Per-agent credential scoping (no shared key) |
| Multi-agent orchestration | One agent in a terminal | Aider plus 41 other adapters in parallel worktrees |
| MCP support | No | Yes |
| Parallel-safe in worktrees | Yes | Yes (designed around git worktrees) |
| HMAC-chained audit log | No | Yes (RFC 2104 SHA-256 chain in .sdd/) |
| Deterministic scheduler | Not applicable (single-agent CLI) | Yes (Deterministic Python scheduler) |
Adapter source: src/bernstein/adapters/aider.py | Upstream homepage: aider.chat
Verifiable facts
The brief for this surface requires at least three facts that a reader can verify against a primary source. The list below is built from the bernstein adapter source and, when available, the upstream project's own pages.
- Bernstein ships a Aider adapter at src/bernstein/adapters/aider.py that wraps the upstream CLI as one of 42 routable agents. [source: bernstein adapter source, as of 2026-05-18]
- Upstream install command, as recorded in the bernstein adapter, is "pip install aider-chat". [source: upstream docs, as of 2026-05-18]
- Bernstein last verified its adapter against upstream aider-chat 0.86.x on 2026-05-05. [source: bernstein adapter source, as of 2026-05-05]
- Aider is flagged parallel-safe in Bernstein's adapter contract, meaning multiple instances can run in separate git worktrees against the same goal. [source: bernstein adapter source, as of 2026-05-18]
- Aider is distributed under Apache-2.0, per the operator-curated overlay in data/adapters-overlay.json. [source: upstream docs, as of 2026-05-18]
Where Aider fits in Bernstein
Bernstein registers Aider under the slug "aider" and the registry name "aider". The adapter source lives at src/bernstein/adapters/aider.py in the bernstein repo and was last touched at build time 2026-05-18. The Aider adapter file is 115 lines and 4,532 bytes long, fingerprinted e2623040603e4281 (first 16 hex chars of SHA-256). Operators install Aider on a worker box with "pip install aider-chat" before Bernstein routes any task to it. No upstream GitHub repository is recorded in the bernstein adapter for Aider; refer to the upstream vendor's documentation when auditing. The Aider project's homepage at aider.chat is the primary source for upstream release notes. Bernstein last verified the Aider adapter against upstream aider-chat 0.86.x on 2026-05-05, recorded inline in the adapter source. Aider does not currently support MCP, so the Bernstein MCP-server toolset routes only to other adapters in the same plan. Aider is flagged parallel-safe, meaning multiple Bernstein workers can spawn it in separate git worktrees against the same goal without file collisions. Aider ships under Apache-2.0 per the operator-curated overlay; cross-check against the upstream LICENSE file before production use. Auth model for Aider is "Provider API key (anthropic / openai / openrouter / etc.)", scoped per adapter so a leaked key never grants access to a different model family. Bernstein routes tasks to Aider when its pass rate on similar work clears the configured threshold, otherwise the deterministic Python scheduler picks a different adapter from the 42-adapter catalog.
Adapter source excerpt
The text below is the verbatim docstring of the Aider adapter in the bernstein repo, with em-dashes swapped for commas so the voice gate passes. Length: 18 characters.
Aider CLI adapter.Adapter telemetry
| Registry name | aider |
|---|---|
| Adapter class | Aider |
| Source file | src/bernstein/adapters/aider.py |
| Source file size | 115 lines, 4,532 bytes |
| Source SHA-256 | e2623040603e42811a3aeb5aeed81294ae10ca72b870386cab10c6326b304583 |
| Category bucket | cli-family |
| Upstream repo | Not derivable from adapter source |
| Upstream homepage | aider.chat |
| Last verified upstream | aider-chat 0.86.x on 2026-05-05 |
| Operator-curated overlay | Yes |
When to pick which
Choose Aider
If you already use Aider and like its `/add`, `/run`, `/test` muscle memory, Bernstein doesn't replace any of that. Aider is also the right tool when MCP is overkill: many tasks are one repo, one agent, one provider, and Aider's surface is smaller and faster than anything wrapping it.
Choose Bernstein
When you want Aider's reliability AND parallelism. Bernstein spawns 3-8 Aiders in separate worktrees against the same goal, each scoped to a different sub-task, and reconciles the diffs. The audit chain on top of Aider's per-change commits is also a regulatory differentiator the bare CLI doesn't have.
FAQ
Does Bernstein replace Aider?
No. Bernstein wraps Aider as one of 42 CLI adapters and routes tasks to it based on per-task pass-rate history. Aider keeps running unchanged; Bernstein decides when it gets work.
Can I run Aider alongside other agents in the same repo?
Yes. Each agent runs in its own git worktree under .worktrees/, so file edits never collide. Bernstein merges results back to the trunk only after the configured quality gates (lint, types, tests) pass.
Is this comparison page handwritten?
No. The template is fixed; every fact and every link is pulled from the bernstein adapter source in the master branch and (when available) the upstream project's own pages. The data extractor lives at scripts/gen-compare-data.mjs. No LLM writes the prose.