OrcaReplay

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Your agent broke something at 2am. Replay it at 9am — exactly, offline, as many times as you like.

Record any coding agent. Reproduce the run byte-for-byte with no model called. Fork it from any step onto a different model and see who gets it right.

Built by the team behind OrcaRouter — one API key and one endpoint for Claude, GPT, Gemini, Grok, DeepSeek, Qwen and the rest. It is what orca setup points at by default, and what makes orca compare a single command instead of four provider accounts.

Find us: OrcaRouter All model APIs

Github Repos: OrcaCode Review · OrcaRouter Lite

Connect: X · Discord · Hugging Face · Ollama

Real output from one session — a Claude Code run recorded, replayed against the recording, then forked at checkpoint 4 onto two models and graded by npx tsc --noEmit. Nothing here is mocked up.

Try it in three commands

One npm package named orcareplay, which puts one command named orca on your PATH. There is no separate tool called "orca", and nothing is installed into your agent.

npm i -g orcareplay             # the package is orcareplay; the command it installs is orca

orca record claude              # your agent, unmodified, doing whatever it does
orca replay last                # the same run again — no network, no tokens, no charge
orca replay last --from 4 --model claude-haiku-4-5 --ui

The third line is the one people stay for: same files, same conversation prefix, different model from step 4 onward. The model is the only variable, which is what makes the answer mean anything.

The three commands at the top need an agent installed, a key, a network and real tokens. If you have none of those yet, one command brings its own:

orca quickstart

It writes a small project with a genuine bug in it and a recording of an agent fixing that bug, then replays the recording against the project with no model called: two failing tests before, four passing after, three turns served from the trace and nothing spent. --full prints the whole timeline and the replay as it happened.

Read your agent's own system prompt

A proxy that sees the whole loop also sees the prompt the harness assembled before it sent anything. One command captures it, scrubs the machine out of it, and files it by model:

node capture/capture.mjs claude --model claude-opus-5

Interactive prompts and -p prompts are not the same prompt, and neither is the same across models. See capture/README.md for the measured differences, the pitfalls, and the sanitising rules.

Why this exists

Agent debugging today is archaeology. You scroll a terminal, you re-run and get a different failure, you add print statements to someone else's harness. The tools that exist are observability tools: they tell you a run cost $4.12 and used 61k tokens, which is not the question you have. The question you have is why did it delete my migration file.

OrcaReplay answers that by giving you the run back.

	Observability tools	OrcaReplay
Tells you what a run cost	✅	✅
Tells you which tool call deleted the file	sometimes	✅
Runs the agent again and gets the same answer	❌	✅ from the recording, byte-for-byte
Lets you change the model and re-run from step 4	❌	✅
Needs you to modify your agent	usually an SDK wrapper	❌ two env vars
Works after you close the terminal	❌	✅ it is a file
Sees past the model API — shell exit codes, file writes	❌	✅ every turn
Records an agent with no API endpoint to redirect	❌	✅ opt-in --tls-intercept

The last two rows are the ones an SDK wrapper structurally cannot reach. Capture happens below the agent — at the process and socket boundary — so it does not matter whether the agent is yours, whether you can edit it, or whether it even holds an API key: a Codex CLI signed in with a ChatGPT subscription talks to its own backend over TLS, with a credential that only that backend accepts, so it cannot be pointed elsewhere and stay the same session — and orca can still record it. See when the harness will not be redirected.

How it works

Model APIs are stateless, so on every turn an agent resends the entire conversation — including the previous turn's tool results. A proxy in front of the model therefore sees the whole loop: each request, each streamed response, every tool call the model emitted, and every tool result the harness produced. That one property is what the tool is built on, and it is why OrcaReplay does not patch your agent — it stands up a local proxy, sets two environment variables, and gets out of the way.

This is the beginning of the README. Read the rest at the original. Read the full README ↗