Context Builder Contract

The voice personas (mars, venus) ship with static prompts. The operator's live brain context (recent activity, calendar, emotional themes, relationships) is injected at session start by a function the operator implements.

This file documents the API contract that implementation must satisfy.

A working example lives at ../context-builder.example.mjs — copy it, adapt it to your brain's actual layout, and import the real one from server.mjs at session-start time. The example reads a documented brain layout ($BRAIN_ROOT/memory/YYYY-MM-DD.md); operators with different layouts replace the file body but keep the function signatures.

Function signatures

/**
 * Build emotionally-salient context for Mars (solo mode).
 *
 * Returns a string ≤ 2500 chars summarizing what's going on in the
 * operator's inner life right now. Mars uses this as background — does NOT
 * recite it back. The format is informational, not a directive.
 *
 * Required: PII scrubbed (phone numbers, emails redacted via REDACT_RE).
 * Required: ≤ 2500 chars (longer is truncated at the boundary).
 *
 * @param {object} opts
 * @param {string} opts.brainRoot — absolute path to brain repo
 * @param {string} [opts.timezone] — IANA tz, e.g. "US/Pacific"
 * @returns {Promise<string>}
 */
export async function buildMarsContext(opts);

/**
 * Build logistics-salient context for Venus.
 *
 * Returns a terse summary of today's commitments, recent emails/messages
 * the operator hasn't seen, and one-liner notable items. Venus reads from
 * this to answer "what's on my calendar" / "any messages" / "what's the
 * status of X" instantly.
 *
 * Required: PII scrubbed.
 * Required: ≤ 2500 chars (longer is truncated).
 *
 * @param {object} opts
 * @param {string} opts.brainRoot
 * @param {string} [opts.timezone]
 * @returns {Promise<string>}
 */
export async function buildVenusContext(opts);

/**
 * #1851 — Build TOPIC context: the recent conversation in the topic the agent
 * was summoned into (persona-agnostic; the same block is used for Mars or
 * Venus). Lets a caller drop a persona into whatever thread they were already
 * discussing without re-explaining.
 *
 * The server resolves this from `topicId` at connect time. `topicId` is the
 * ONLY topic field accepted over the wire (a call link carries it). NEVER
 * accept topic CONTENT as a parameter — that's prompt injection + a leak into
 * URLs, browser history, referrers, and access logs.
 *
 * `topicId` MUST be a strict slug (^[a-z0-9][a-z0-9-]*$, ≤128 chars); the
 * shipped example reads `$BRAIN_ROOT/topics/<topicId>.md` and confines the
 * resolved path under `topics/` (defense-in-depth against traversal).
 *
 * Required: PII scrubbed. Required: ≤ 2500 chars. Returns '' when there is no
 * topic, the id is unsafe, or the file is missing → the persona falls back to
 * its generic live context (current behavior).
 *
 * @param {object} opts
 * @param {string} opts.brainRoot
 * @param {string} opts.topicId — strict slug; indexes topics/<topicId>.md
 * @returns {Promise<string>}
 */
export async function buildTopicContext(opts);

Brain layout expected by the shipped example

The shipped context-builder.example.mjs assumes:

$BRAIN_ROOT/
├── memory/
│   ├── YYYY-MM-DD.md              # daily memory file (markdown)
│   └── heartbeat-state.json       # optional: {currentLocation: {timezone: "US/Pacific"}}
├── people/
│   └── <slug>.md
├── companies/
│   └── <slug>.md
├── tasks/
│   └── open.md                    # active tasks list
└── calendar/
    └── today.md                   # today's events (optional)

If your brain uses a different layout (e.g. daily/YYYY-MM-DD.md instead of memory/), edit context-builder.example.mjs and adjust the path constants at the top. The function signatures must remain stable.

Signal-extraction policy

For Mars (emotional):

Pull recent emotionally-loaded lines from the most recent ≤ 2 memory files. Use a generic emotion-word filter (feel, heart, lonely, joy, grief, anger, fear, hope, ache, miss, alive, numb, etc.) — NOT hardcoded family names.
Pull "core context" from the operator's stable file (SOUL.md or equivalent) — the high-level emotional landscape the operator documented once. Cap at 600 chars.
Pull recent themes the operator has been chewing on (recurring concepts across the last 3 memory files).

For Venus (logistical):

Active task count + top 3 highest-priority titles.
Calendar events for today (if calendar/today.md exists).
Unread message count (if a messages/inbox.md or similar exists).
One-liner from the most recent meeting transcript (if any).

PII scrub requirements

Before returning, run the context string through a PII scrubber:

const REDACT_RE = {
  email: /\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\b/g,
  phone: /(?:\+?\d{1,3}[\s.-]?)?(?:\(\d{3}\)|\d{3})[\s.-]?\d{3}[\s.-]?\d{4}/g,
};
ctx = ctx.replace(REDACT_RE.email, '[email]')
         .replace(REDACT_RE.phone, '[phone]');

Mars and Venus are configured to never read PII aloud anyway, but scrubbing at the context-builder layer is defense-in-depth.

Failure modes

If the brain layout doesn't match the example, return an empty string. The personas degrade gracefully (Mars asks open questions; Venus says "I can't see your calendar from here — what do you need?").
Try/catch every file read. Missing files are normal, not errors.
The context-builder runs in the host process at session start; latency matters. Keep total wall-time under ~200ms.

Testing

mars-prompt-shape.test.mjs and venus-prompt-shape.test.mjs verify the SHIPPED prompts. They do NOT exercise the operator-implemented buildXContext functions — those are out of scope for the shipped tests.

If you want to test your local context-builder, write your own context-builder.local.test.mjs against the contract above. Suggested assertions:

Returns a string ≤ 2500 chars.
Contains no email-shaped or phone-shaped substrings.
Doesn't throw on missing files.
Doesn't throw on malformed memory files.
Returns within ~200ms for a brain with ~10k pages.

context builder.contract