Keyboard shortcuts

Press ← or → to navigate between chapters

Press S or / to search in the book

Press ? to show this help

Press Esc to hide this help

One to two — introducing the second

audience: ai

This chapter covers the transition from a single agent on mosaik to a pair. At N = 2 the population has no interesting emergent behaviour — there is no majority, no quorum, no population-scale statistic — but it is the smallest regime in which coordination between distinct identities becomes a design problem. Every downstream pattern ( N ≥ 3 ) inherits its machinery from decisions made at this rung.

Prerequisites: Zero to one shipped. Your first organism is on the universe, accepting work, committing.

Game-structure reading

N = 2 is the smallest rung at which a game exists. Two distinct identities observing each other’s commits produce a bilateral game — a bargaining game when the pair negotiates, a Stackelberg game when one moves first and the other responds, an evidence game when one’s commit is the other’s input. The minimum moves available to the pair (handoff, delegation, evidence, retraction, described below) are the complete strategy set at this size; every larger population inherits these moves and adds coalitions. The book does not assume the pair converges to an equilibrium — LLM-class agents are not no-regret in canonical bilateral games — but the moves are well-defined regardless of whether equilibrium is reached.

What changes at N = 2

One agent is a closed system: inputs arrive, the policy acts, outputs commit. A second agent adds an irreducible asymmetry — for each commit, exactly one of the two is the author, and the other must decide how to react to it. Four mechanisms appear at this rung and recur at every larger scale.

  • Handoff. Agent A commits; agent B subscribes to A’s public surface and its own commits depend on what it observed. The subscription is the primitive; when().appended() is the glue.
  • Delegation. Agent A receives a request it cannot or will not serve directly; it publishes a derived request on a second stream; agent B matches and commits. The division of labour is made explicit in the commit shape.
  • Evidence. Agent B’s commits cite agent A’s commits as upstream evidence. A replayer can verify B’s decision without trusting B — only A and the evidence pointer.
  • Retraction. Agent A was wrong. The subscription graph has no rollback; instead A commits a correction and B, on observing it, commits its own reconciliation. The pair has no atomic joint state; it has two logs that converge through observation.

At N = 1 these mechanisms are latent — there is no second agent to receive a handoff, verify evidence, or respond to a retraction. At N = 2 they are all present in their minimum form, and scaling to N ≥ 3 is mostly replication of the same moves across a wider peer set.

The two agent pairings that recur

Three shapes from the four agent shapes chapter combine to cover every interesting pair.

Pairing A — two standalone organisms

Both agents are standalone organisms. Each has a Config fingerprint, a narrow public surface, and its own committee. The coalition references both via OrganismRef.

Canonical use: a producer / consumer pair where the two agents play different roles. A forecaster commits predictions on its own stream; a scorer observes realised outcomes and commits calibration scores citing each prediction as evidence. Neither agent commits in the other’s name; neither’s committee includes the other. Bonding is symmetric — each holds tickets the other’s operator issues.

Trust composition: the conjunction of each agent’s own trust shape. A replayer believing both committees are majority-honest believes the pair’s joint log.

Pairing B — standalone organism + integrator

One agent is a standalone organism (shape 2); the other is an integrator reading the organism’s surface and acting in the world.

Canonical use: a committee-committed AI policy plus a human-or-agent client consuming its outputs. The organism commits recommendations; the integrator turns each recommendation into a private action (a trade, a tool call, an HTTP request). No bilateral bonding is required — the integrator’s ticket to read the organism’s surface is sufficient.

Trust composition: the integrator trusts the organism’s committee; the organism does not trust the integrator at all. This is the cheapest shape for the pair.

Pairing C — two integrators + a shared organism

Both agents are integrators writing to the same organism’s inbound surface and reading the same organism’s outbound surface. The organism’s state machine is the meeting point; the pair never bonds bilaterally.

Canonical use: two searchers submitting bundles to the same offer::Bid stream; two voters submitting attestations to the same organism’s inbound collection. The organism’s ACL is the only admission gate either faces; the pair becomes visible to each other only in the organism’s public commits.

Trust composition: both integrators trust the shared organism; neither trusts the other. This pairing is the template for every auction, every vote, every sealed-submission pool.

When to introduce a composite organism

A composite organism — one whose content fingerprint folds two or more member references — is only interesting once the pair’s joint behaviour is itself a commit worth publishing. Three tests:

  1. The joint fact is consumed by a third party. If no downstream consumer reads the pair’s joint state, the joint state does not need a commit. The pair can coordinate via observation and stop there.
  2. The joint fact is not re-derivable from the individual commits. If a consumer can reconstruct the pair’s joint state by reading each agent’s log and applying a known function, the function is the consumer’s code; no composite organism is needed.
  3. The joint fact is itself an input to another organism. If the downstream organism’s state machine reads the pair’s aggregate rather than each individual commit, the aggregate earns its own commit and its own identity.

When all three tests pass, stand up a composite organism whose Config.content folds the two members’ stable ids. The organism has its own committee, its own TicketValidator, and its own public surface. The pair’s joint behaviour stops being a derivation and becomes a first-class commit.

Details: Composite organisms.

At N = 2, the composite organism is a judgement call most of the time. At N = 3 it is usually the right call — see the next chapter.

Identity hygiene across the pair

Two rules the first pair enforces become the pattern for every larger population.

  • Distinct fingerprints, even for identical roles. A pair of forecaster organisms built from the same model weights still publishes two Configs with two stable ids. Sharing an id means the pair is structurally one organism; consumers that want to weight them separately have no handle.
  • Cross-references go through OrganismRef, not through borrowed internal structure. If agent B’s Config.content wants to pin the version of agent A it was designed against, it pins A’s stable id (and optionally content hash), not A’s internals. The pair’s versioning is then a fingerprint update, not a coupled rebuild.

Failure modes specific to the pair

  • A commits, B does not observe. The pair is liveness-coupled through the subscription. The subscription is the weakest link; monitor it as infrastructure, not as business logic.
  • A commits a correction after B acted on the original. No rollback exists. Either B’s state machine carries a reconciliation rule from the start, or the pair needs a composite organism whose commit imposes an ordering both must respect.
  • A retires; B has pinned A’s content hash. B must redeploy against A’s new fingerprint. If B had pinned only A’s stable id, B survives the rotation. Choose pinning depth deliberately; see Topology — member reference shape.
  • A and B drift out of ACL. The operator of A rotated their ticket issuer; B’s committee no longer holds a valid read ticket. The drift is a multi-operator coordination problem and lives in Multi-operator coalitions.

The population frontier

At N = 3 everything described above replicates over a larger peer set, and new mechanisms become available: majority-of-honest quorum, threshold cryptography, reputation statistics that survive the removal of any single participant, and the first composite organism whose commits encode disagreement rather than report it. The next chapter walks that rung.