Audit — R93 B6 stake_discount_bps Rename

Round: R93 debug-sweep (fix #6 of 6, XS) Branch: feature/r93-b6-reputation-field-rename Base SHA: fbc8808a β task: 2e8978e9-e83d-4c3a-a20a-bf66cacc9251

§1. Goal

Rename the stake_discount_bps output field of reputation_check_gates to effective_stake_bps. The current name is misleading — it sounds like a percent discount but is in fact the effective stake amount in BPS-multiplied form.

§2. The misleading semantics

src/domains/reputation/limits.ts:172-180 defines stake_discount(required_stake, rep_execution):

stake_discount = safe_div(safe_mul(stake, BPS_100_PERCENT), max(score, 1000n))

For an unknown node with score=0 and the canonical input stake=BPS_100_PERCENT=10000, the result is 100000 — which the tool surfaces as stake_discount_bps: 100000. The docstring on the tool says this is “10× stake required”. The field name implies “1000% discount”. Those mean opposite things.

Per the live MCP probe in the R93 debug audit:

mcp__colibri__reputation_check_gates {node_id:"unknown", current_epoch:0}
  → {can_arbitrate:false, can_govern:false, max_parallel_tasks:0,
     rate_limit_bonus_factor:0, stake_discount_bps:100000}

A consumer reading this naïvely sees “1000% stake discount, free entry!” — the opposite of the actual meaning.

§3. Scope of the rename

rg stake_discount_bps E:\AMS returns 5 files:

File	Occurrences
src/domains/reputation/tools.ts	output type (§C); handler return (§G); docstring example (§G); MCP tool description string
src/__tests__/domains/reputation/tools.test.ts	tests asserting on the field
docs/contracts/p2-5-1-tools-contract.md	heritage P2.5.1 contract doc — describes the field shape that shipped
docs/audits/p2-5-1-tools-audit.md	heritage P2.5.1 audit doc
docs/guides/implementation/task-prompts/p2.1-lambda-reputation.md	source prompt for the work

Notable absent: docs/3-world/social/reputation.md and docs/spec/s04-reputation.md do not reference the field by name — they document the formula, not the wire shape. The underlying stake_discount(...) function name (src/domains/reputation/limits.ts:172) describes the formula and stays unchanged.

§4. Constraints

• MUST NOT rename the underlying stake_discount(...) function — its name describes the formula and is referenced from spec docs (docs/spec/s04-reputation.md §Derived limits row 4 describes the formula by that name).
• MUST update every stake_discount_bps field-name reference (tool wire shape) to effective_stake_bps.
• MUST update tests that assert on the field name.
• MAY update heritage docs (p2-5-1-tools-*) to reflect the new wire shape; the original audit/contract/packet chain stays intact as historical, but the field-name reference is brought in line with what’s actually emitted today.
• The MCP tool description string in tools.ts:436 references the field by name — update.

§5. Path forward

Six replace_all operations on the literal stake_discount_bps → effective_stake_bps across the 5 files. Update the docstring example block in tools.ts:330-334 to use the new name. Update the docstring rationale paragraph to make clear this is the effective stake, not a discount factor.

Proceeding to contract + packet (compact for XS scope).