Question 1

What is T0?

Accepted Answer

T0 sells hosted, sandboxed AI coding-agent sessions over a REST API. You create a session, push files into it, send it messages, and stream the agent working in real time. Each session is an isolated Linux workspace that persists between messages, so files the agent wrote, packages it installed and git state are all still there on the next message. T0 sells the runtime — isolation, persistence, orchestration and latency — with model access included in every plan. Base URL: https://api.t0.sikasio.com/v1.

Question 2

How do I get an API key?

Accepted Answer

Create an account at https://t0.sikasio.com/signup with an email and a password, verify the code we email you, and your key is shown once — copy it straight away. Send it as an Authorization: Bearer header on every /v1 request. Keys are the tenant boundary: they identify the account, authorize the request, and are what usage is metered against. Revoke one from the dashboard and it stops working within seconds.

Question 3

Do I need my own coding-agent subscription?

Accepted Answer

No. Model access is included with your plan: sessions run on T0's own Claude Code account behind T0's gateway, so there is nothing to bring, no token to paste and no model credential to manage. The account credential never enters your sandbox, and your plan's credits are the only meter.

Question 4

Which models can I use?

Accepted Answer

Two tiers, named by T0: core for everyday work and max for the hardest tasks. Set the tier when you create a session; core is the default. Model access is included with your plan, so the tier is the only model choice you make.

Question 5

Can I just send a prompt and get an answer back?

Accepted Answer

Yes — POST /v1/runs takes one prompt and returns one answer in the same HTTP call. It creates a session, runs the turn, and hands the container back; you never see the session. Use it for classification, extraction, drafting and summarising, and use a session when the agent needs a workspace, tools or memory of what it just did. Tools are off by default on a run, which is most of why it is cheap: an agent holding a toolkit spends billable seconds deciding whether to use it on a question that needed none. Send tools: "all" when the work genuinely needs the machine. Ask for JSON with response_format — either json_object, or json_schema with a schema — and the answer comes back parsed in output_json. An answer that does not match is sent back once for repair before the call fails. Runs are counted against their own concurrency ceiling rather than against concurrent sessions, so a burst of one-shot calls never locks you out of the sandboxes you are keeping open.

Question 6

What persists between messages?

Accepted Answer

Everything inside /workspace, plus the agent process itself. The process stays alive for the life of the session, so conversation context stays resident and follow-up turns do not re-read everything from scratch. That is the single largest latency win in the system. When a session goes idle the container stops but its volume survives, so resuming is a start rather than a rebuild. Workspaces are also snapshotted to object storage, which is what makes a resume possible days later.

Question 7

What happens when a session goes idle?

Accepted Answer

After idle_timeout (10 minutes by default) the session moves to sleeping: the container stops, the workspace is kept, and a session.idle event is emitted. Sleeping costs nothing — metering counts awake seconds only. The next message wakes it. A resume inside the warm window is a container start; a colder resume restores the workspace from object storage first. Files can be downloaded from a sleeping session without waking it.

Question 8

How is usage metered?

Accepted Answer

A credit is one minute of awake session time. Sleeping sessions cost nothing. T0 meters awake session-seconds, peak workspace bytes and turns; token counts are recorded and shown to you for your own visibility — model usage is included with your plan and never billed separately.

Check live usage any time with GET https://api.t0.sikasio.com/v1/usage.

Question 9

Is there a free plan?

Accepted Answer

Yes, permanently. Free is $0 for 60 credits a month (1 h of awake session time), 20 a day, 1 concurrent session, 400 MB of workspace storage and a 7-day retention window. No card required.

One rule to know: buying credits retires the free monthly allowance permanently — from your first purchase on, usage runs on the credits you bought. Credits never expire.

Question 10

What are the plans and quotas?

Accepted Answer

Free — $0: 60 credits/month (1 h), 20/day, 1 concurrent session, 400 MB storage, 7-day retention, 1 GB / 1 CPU sandbox.

Starter — $19/month: 600 credits/month (10 h), 120/day, 3 concurrent sessions, 5 GB storage, 30-day retention, 2 GB / 1.5 CPU sandbox.

Pro — $59/month: 2,400 credits/month (40 h), 360/day, 10 concurrent sessions, 20 GB storage, 90-day retention, 4 GB / 2 CPU sandbox.

Question 11

Is there a pay-as-you-go option?

Accepted Answer

Yes, and it works on every plan rather than instead of one. Buy credits and they sit unused until the monthly allowance runs out; from then on they pay for the minutes the allowance would have refused, at $0.04 / min. $10 buys 250 credits, $25 buys 625 credits. That means running out mid-month is a choice rather than a wall: with no balance you get the usual 429 and wait for the reset, and with one the work carries on. Nothing changes plan, nothing is entered that has to be left, and the same rate applies whichever model tier you run. Credits never expire, and they are spent by the second — a five-second turn costs five seconds of credit, not a rounded-up minute. When the balance reaches zero the API stops rather than billing on.

Question 12

What happens when I hit a quota?

Accepted Answer

Never a surprise bill. Past the monthly allowance, an account with credits keeps working and spends them; an account without gets 429 quota_exceeded naming the limit, the next plan up, and the option of a top-up. Requests past the per-key rate limit return 429 rate_limited with a Retry-After header. Sessions already awake are not killed mid-turn.

Question 13

How do I stream a response?

Accepted Answer

POST a message to https://api.t0.sikasio.com/v1/sessions/:id/messages — it returns 202 with a turn_id immediately — and read events from GET https://api.t0.sikasio.com/v1/sessions/:id/events, which is Server-Sent Events. Events are ordered and sequence-numbered per session, so if the connection drops you reconnect with a Last-Event-ID header carrying the last sequence you saw and the stream resumes from there with nothing lost or repeated. If you would rather push and pull over one connection, https://api.t0.sikasio.com/v1/sessions/:id/socket is a WebSocket that carries the same events and accepts messages and interrupts.

Question 14

How do I get files in and out?

Accepted Answer

Small files go straight to the API: PUT the raw body to /v1/sessions/:id/files/<path> and it is streamed into the live workspace. Bulk uploads go as a tar.gz to POST /v1/sessions/:id/files. Large transfers are handed a presigned object-storage URL so the bytes never pass through our servers. Every path is resolved and confined to /workspace before it reaches the container; traversal is rejected with 400 invalid_path.

Question 15

How isolated is a session?

Accepted Answer

Each session is its own container: read-only root filesystem, all Linux capabilities dropped, no-new-privileges, a seccomp profile, a pids limit, and hard memory and CPU ceilings set by your plan. It runs as a non-root user and never sees a Docker socket, a host mount or host networking. Egress is default-deny through an allowlist proxy that refuses every private network range, so a session can reach the model provider and — depending on plan — package registries, and nothing else. The proxy fails closed: if it is down, the sandbox has no network at all.

Question 16

Where do I see whether T0 is up?

Accepted Answer

The status page at https://status.t0.sikasio.com shows live component health — gateway, runner, warm-pool depth, queue depth and recent error rate — plus incident notes. It is served from its own host so it stays up when the stack it reports on does not.

Question 17

What does a first request look like?

Accepted Answer

curl -X POST https://api.t0.sikasio.com/v1/sessions -H "Authorization: Bearer t0k_live_YOUR_KEY" -H "Content-Type: application/json" -d '{"name":"my-first-session"}' — that returns a session id and a stream URL, and the session is ready in under a second because it comes from a pool of pre-booted containers.

Pricing

And pay as you go, on any of them

Every limit, side by side

What a credit is

Metered, enforced, and not billed

Metered

Enforced

Not billed by T0

Shown to you anyway

Billing

Questions about plans

	Free	Starter	Pro
Price	$0	$19/mo	$59/mo
Credits / monthone credit = one minute awake	60 (1 h)	600 (10 h)	2,400 (40 h)
Daily capcredits per UTC day	20	120	360
Concurrent sessions	1	3	10
Concurrent runsone-shot /v1/runs, counted apart	2	10	30
Workspace storagedurable, per account	400 MB	5 GB	20 GB
Live disk per sessiontechnical ceiling	5 GB	10 GB	20 GB
Retentionafter a session ends	7 days	30 days	90 days
Sandboxmemory / CPU	1 GB / 1 CPU	2 GB / 1.5 CPU	4 GB / 2 CPU
Past the allowancecredits, on every plan	$0.04 / min	$0.04 / min	$0.04 / min
Top-upscredits never expire	$10 → 250 · $25 → 625	$10 → 250 · $25 → 625	$10 → 250 · $25 → 625