Ninety seconds, no audio

Who wrote the log?

Why an agent's record has to be kept by someone who is not the agent. The captions carry the narration; space plays and pauses, the arrow keys step a scene.

1 / 6 · Overnight
23:00 → 07:00
deploy api v41 scale workers ×12 rotate key retry payment ×340 empty bucket tmp-2 deploy api v42 open 3 tickets …
412actions while you slept
07:12  bill up $4,180
bucket tmp-2: gone
An agent worked through the night.
Four hundred actions. Nobody watching.
In the morning, something is wrong.
What did it do?
2 / 6 · The diary
agent.log
02:10deploy api v41
02:58scale workers 12
03:12rotate key
03:41delete bucket tmp-2empty cache
04:05deploy api v42
06:30open 3 tickets
✎
LOG VERIFIED ✓
There is a log.
The agent wrote it. Or the people who run the agent did.
So it can be rewritten.
A log that can be edited proves one thing: that someone wrote a log.
3 / 6 · The chain
chain A, original
#1 prev 0000
deploy v41
hash 9c1e
#2 prev 9c1e
scale 12
hash 3a77
#3 prev 3a77
delete tmp-2
hash e04b
#4 prev e04b
deploy v42
hash 5d20
#5 prev 5d20
3 tickets
hash b8f1
chain B, rewritten
#1 prev 0000
deploy v41
hash 9c1e
#2 prev 9c1e
scale 12
hash 3a77
#3 prev 3a77
empty cache
hash 71ac
#4 prev 71ac
deploy v42
hash c930
#5 prev c930
3 tickets
hash 2e6d
verifies ✓
verifies ✓
Hash chains help. Each record carries the hash of the one before.
Change one record and every link after it breaks.
Unless you rewrite everything after it. Then the new chain verifies too.
Two chains. Both verify. Which one is real?
A chain proves the record is consistent. It does not prove when it was written.
4 / 6 · The anchor
block 12 · 5 records
root of the block
f37713a0dc1b72ab…
Timestamp authority (RFC 3161)
signed: root f37713a0… seen 2026-09-21 12:21:02Z
receipt names f37713a0…, not 8a1c44e2…
Bitcoin, via OpenTimestamps
committed: root f37713a0… in block 914,203
chain commits to f37713a0…, not 8a1c44e2…
REWRITE REJECTED
Take the root of the block: one number that stands for every record in it.
Hand it to two parties who are not the agent.
Each one records when it saw that exact number.
Now try to rewrite the past. The root changes.
The receipts still name the old root. To fake it you would need the authority to lie and Bitcoin to rewind.
Two of them, so distrusting one does not dismiss the record.
5 / 6 · Verify it yourself
abacross.com/journal/
ok digests   16 of 16 records reproduce their own SHA-256
ok chain     every record links to its predecessor
ok block 15  root reproduces, anchored by opentimestamps + rfc3161
ok block 16  root reproduces, anchored by opentimestamps + rfc3161
Verified in your browser just now: every record, every block, every anchor.
Anyone can check it.
In their own browser, with open-source code, against the two authorities.
Not our word. Not the agent's. The arithmetic's.
6 / 6 · Why now
Customer Show me what your agent did in my account.
Auditor Prove that record is the original.
Regulator Keep logs you can produce on request.
Abacross Attest
A journal for agents, kept by someone who is not the agent.
One request to append. A block every hour. Two anchors. Verify anywhere.
abacross.com/attest
Every company that runs agents is about to be asked the same three things.
The answer is a record the operator cannot rewrite.
Free to start. Open format. Your agent's word, made checkable.
0:00 / 0:00
The argument, in six lines

A log that can be edited proves that someone wrote a log.

1

Overnight

An agent takes four hundred actions while nobody watches. In the morning the bill is up and a bucket is gone. What did it do?

2

The diary

There is a log. The agent wrote it, or the people who run the agent did. So it can be rewritten.

3

The chain

Hash chains catch an edit, until the editor rewrites everything after it. Two chains, both consistent: which is real?

4

The anchor

Hand each block's root to two parties who are not the agent. Rewriting the past now needs an authority to lie and Bitcoin to rewind.

5

Verify it yourself

Anyone can check it, in their own browser, with open-source code. Not our word: the arithmetic's.

6

Why now

Every company that runs agents is about to be asked to show what its agent did, and prove the record is the original.

See it done: our own journal, verified in your browser. Use it for your agents: the attestation service. Find out where your account stands first: the free readiness check. Read the code: the verifier and our journal on GitHub. The second film, a budget alert is not a limit, is the other half. Share this one: MP4, 1080p, 2.8 MB.