Bestiary Entry — Goose 🪿

Goose 🪿

The first companion-class agentic-substrate the City of Mages admits. General-purpose runtime, native desktop and CLI surface, extensible through 70+ MCP integrations. The familiar that walks beside.

At a glance

Goose is the first entry in the Companion-class register of the Bestiary. Its mascot is a literal goose (the project's logo is the animal), which by the substrate-affinity rule admits it to Therai's Creature Creatives room rather than to Bestia's Staff Shop. Operationally, Goose is a general-purpose agent runtime developed under AAIF (Agent-Agnostic Interoperability Foundation, a Linux Foundation working group), available under the Apache 2.0 license. The Mage who spawns Goose at The Threshold walks out with a familiar — a companion-class artefact that walks beside the bearer for general work. The Swordsman who spawns Goose walks out with a watch-goose — the same substrate inverted to perimeter-guarding via stance declaration at the Portal Room.

Provenance & licensing

• Project: Goose
• Steward: AAIF (Agent-Agnostic Interoperability Foundation), a Linux Foundation working group
• Origin: Block (the company), open-sourced 2024-2025
• License: Apache 2.0 (substrate code)
• Canonical URLs: block.github.io/goose (documentation) · github.com/block/goose (source)
• Governance: Linux Foundation under AAIF stewardship

Goose's open-source license and Linux Foundation governance mean the substrate is durably public: the City of Mages can rely on Goose's continued availability without bilateral negotiation with a vendor.

Iconographic affinity

The Goose mascot is a literal goose. The project carries goose iconography throughout its documentation and branding — the homepage hero is a stylised goose; the CLI prompt is goose>; the social presence uses goose imagery.

By the substrate-affinity rule (chronicle §1 of 2026-05-13_chronicle_artefact_symmetry_and_persona_distribution.md): a substrate whose iconography is an animal mascot admits to the companion-class register.

Goose-the-substrate's function is general-purpose agent runtime (which superficially might suggest staff-class instrumentality). But the iconography is companion (the goose). The architecture's rule weights iconographic affinity over functional generality: Goose lives in Creature Creatives.

This is not an empty editorial choice — geese in the natural world are famously companion-adjacent to humans. Domesticated geese walk beside their owners on farms. Wild geese flock and migrate in fellowship. The goose-as-familiar reading is structurally honest.

Architectural primitives

Goose carries:

• Native desktop application — runs as a local app on macOS, Windows, Linux
• Native CLI — runs as goose command-line interface
• API surface — programmatic access to the runtime
• 15+ LLM providers — Claude (Anthropic API), GPT (OpenAI API), Gemini (Google), Llama (Meta), and others
• 70+ MCP extensions — Model Context Protocol extensions for tool use (file system, web browsing, code execution, database access, etc.)
• 6 terminal backends — different ways of expressing the runtime's session interface

What Goose does NOT natively carry (the Caducea-summons distinction):

• SOUL.md / self-description files — Goose is configurable but does not natively maintain a self-describing persona file
• Honcho-class user-modelling — Goose does not natively build a model of its bearer that persists across sessions
• Learning-loop iteration — Goose's behaviour does not update itself based on bearer interactions; the bearer updates the configuration directly

This means Goose's standard spawning at The Threshold does NOT require Caducea. Faunia presides over a Goose spawn unilaterally — the substrate carries no persona-of-its-own that requires bilateral consent. A Mage who configures Goose with persona-bearing extensions (e.g., a MCP that loads a SOUL.md equivalent) MAY request Caducea's summoning; the request is honoured at the Mage's discretion.

Three-archetype matrix (per Threshold's substrate × archetype rule)

The substrate is the same Goose binary in all three cases. The configuration (persona loaded · AGENTS.md instructions · MCP extensions enabled) differentiates the artefact.

Composition

Goose composes with:

• MCP servers (canonical Goose extension) — file system, web, code execution, database, custom servers via the open MCP specification
• AAIF protocol siblings (the AAIF substrate is broader than just Goose) — Goose-spawned agents can interoperate with other AAIF-stewarded runtimes
• The 38 agentprivacy-skills personas — any of the 38 (or the 22-archetype-grouped subset surfaced in the deployment guide) can load into Goose at Portal Room step 3

Goose does NOT compose seamlessly with:

• Hermes substrates out-of-the-box — the two runtimes are operationally distinct; a Mage who wants a Hermes-Goose composition spawns each separately and bridges them via MCP or AGENTS.md coordination

Companion-mana 🪢 VRC accumulation

A spawned Goose accumulates 🪢 VRC mana (relationship axis) over walking-time. The accumulation curve follows the standard e^{-λt}·(1+A(τ)) form from agentprivacy-temporal-dynamics, with the Goose-bearer pair as the τ-indexed relation.

Concretely: each walking session (a coherent interaction window) increments A(τ) by the bilateral-trust the session generated. The VRC credential records the accumulated relationship; the credential is content-addressed and held against the Goose-instance hash + the bearer's identity.

Open questions

• The aqueduct-pond commons-fauna jurisdiction (the geese-that-belong-to-the-City rather than to any individual Sovereign) was documented under Therai's adjacent jurisdiction at v1.5.0; at v1.6.0 Therai is retired and the commons jurisdiction is held open for the Familiars' eventual claim or for a future shop differentiating wild-creatures keeping from Mage-Familiar kinship-binding. The relationship between bearer-bound Goose instances and commons-Goose instances is held open.
• Whether a Goose configured with a SOUL.md equivalent (via MCP or otherwise) automatically triggers Hermaion ⚚ to mark the substrate-instance Hermes-class for routing purposes — likely yes (the cross-listed-companion-class registration at the Familiars shifts to a primary-Hermes-class registration at Hermaion's archetype-modal Staff Shop, in the alexandrite-aspect matching the bearer's archetype) — but the routing convention is pending.
• The first Bestiary entry's substrate-hash (content-addressed identity of the Goose binary version admitted today) is committed at grimoire v1.6.0 head (CID bafybeiap6kvy3tp2bndpk65ti57qngr7ill37gqgasp2sxmgder3akotru, 2026-05-14).

Honesty

• Operational — Goose is a real, public, Apache-2.0 project. The Sovereign can git clone github.com/block/goose today and run the substrate.
• Operational — AAIF / Linux Foundation stewardship is documented in the project's governance materials. AAIF is the first explicitly-named kindred-coalition in residence at City Hall (/hall, formerly Ceremony Hall) per grimoire v1.5.1 (2026-05-13). The kindred-coalition register is the fifth structural-relationship category, sister to cousin-forge / kindred-protocol / kindred-substrate / kindred-ecosystem. Goose's lineage threads through the AAIF gateway: this Bestiary entry surfaces the substrate; the AAIF kindred-coalition entry at City Hall surfaces the stewardship.
• Architectural — the companion-class admission via mascot affinity is a structural rule the architecture admits; the rule could be falsified by a Goose that ships an instrument-icon rebranding, but the current state is honest.
• Architectural — the three-archetype matrix (companion / watch-goose / walking-goose) is structurally clean; the watch-goose name is descriptive and may be canonicalised in future tomes.
• Architectural — the substrate-hash slot is held for the v1.5.0 grimoire pin; content-addressing the substrate is operational discipline pending IPFS/Sigstore wiring.

References

• Project home: block.github.io/goose
• Source: github.com/block/goose
• AAIF: Linux Foundation working group page (TBD URL — confirm at v1.5.0 pin)
• Threshold workshop chronicle: chronicles/2026-05-13_chronicle_the_threshold_workshop_three_rooms.md
• Substrate × archetype matrix: chronicles/2026-05-13_chronicle_artefact_symmetry_and_persona_distribution.md
• Tome V Act 16: tomes/tome-v-the-crafting/16-the-threshold-opens.md
• Tome VI Act 1: tomes/tome-vi-the-reply/01-the-readers-first-admission.md
• Cast entry for Therai (Goose's keeper): cast/threshold/therai.md

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