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# Suspicion & belief modeling — guide (crewrift tier)

Reference notes, design rationale, and negative results (19).

#### 1. Model suspicion as a Bayesian log-odds posterior with a combinatorial prior, no time decay
`crewrift`

Model per-player suspicion as a real posterior P(imposter) in [0,1] via log-odds: logit(P) = logit(prior) + sum of per-evidence log-likelihood-ratios. Compute the prior combinatorially as prior = K/(P-1) (K imposters among the P-1 others), deriving K from the auto-imposter formula (P-3)//2 when unset, and clamp to [1e-3, 0.99]. Because role is a FIXED latent variable, evidence must NOT decay over wall-clock time (venting at minute 1 is permanent evidence; there is no forgetting) -- keep within-event shape functions distinct from any time decay. Interpret fitted coefficients as log-LRs (positive inculpatory, negative exculpatory): witnessed_kills +4.80 is the strongest inculpatory cue and tasks_completed_watched -10.82 the strongest weight overall; expect L1 to zero out non-predictive features (times_defended = 0.0). Add exculpatory negative-weight evidence (LR<1): a positive-only model makes the prior everyone's FLOOR so a single weak cue names a false 'clear leader', whereas negative weights let innocent-looking players sink below the prior and the suspect field separate. Caveat: the static prior never redistributes the imposter budget as players die, so others stay mis-calibrated; in practice a caught player still reads ~1 via its witnessed log-LR, but a joint/sequential prior is the proper fix.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/design.md, personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion.md, personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion-le, personal_labs/crewrift_lab/crewborg/data/suspicion_weights.json (+2)</sub>

#### 2. Shape each evidence LR as a function of event features; the relationship is often inverted
`crewrift`

Give each suspicion event type its own parameterized log-LR function over the event's details, shaped to the real mechanism, not a flat constant -- the feature-to-guilt relationship is often inverted. Body-proximity log-LR should DECREASE with dwell: a skilled imposter flees, so a BRIEF presence is the killer window while a LONG camp signals an innocent reporter (do NOT gate suspicion behind long dwell). Follow-to-death log-LR INCREASES with how long a now-dead victim was shadowed. Being-tailed needs no death (you read your own position perfectly): score it as a logistic in tail duration saturating at a deliberately MODERATE posterior (~0.72; peak log-LR ln 6.5, half-saturation 30 ticks) because crew genuinely move together, and a sustained tail crossing the 0.6 Accuse threshold should CALL A MEETING, not auto-vote. Reserve the near-certainty log-LR (ln 1e6, P approx 1) only for definitionally witnessed events -- a witnessed kill and witnessed vent emergence/submersion -- detected only from CONSECUTIVE tape transitions with 'in line of sight last frame' confirmed via the decoded shadow mask. Standing on a vent is WEAK (flat past a ~3-tick pass-through) because a real venter teleports and is caught by the vent-transition detector. Keep the LR table in a living design doc as its durable home so weights improve across games.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/design.md, personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion.md, claude-code:25488cd9-61d5-4231-bd87-e2744b6db043, claude-code:f70c9801-7ee7-499b-97f9-4fd0848a6b8e (+4)</sub>

#### 3. Watched task completion is the strongest innocence signal; ignore fake-task dwell
`crewrift`

Do NOT use task dwell ('looking busy') as exculpatory evidence: imposters fake tasks (the Pretend behaviour does exactly this). Exclude other noisy cues (brief proximity, single-body passing where an innocent reporter stands by, crew clustering while tasking), and gate body-proximity events on bodies being CLEARED when a meeting opens (matching the server) so they never fire on a stale location. The single strongest crew-innocence signal is WATCHED REAL-task COMPLETION: imposters produced ZERO watched completions across 62k labelled rows, giving tasks_completed_watched a weight of about -10.8 log-LR (most extreme in the fitted model); detect it via a crew_tasks_remaining decrement plus a dwell gate so the observer actually watched it.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/design.md, personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion.md, personal_labs/crewrift_lab/suspicion_lab/README.md, personal_labs/crewrift_lab/crewborg/data/suspicion_weights.json</sub>

#### 4. Sum evidence INSTANCES not types, dedup on context, and refit weights before shipping
`crewrift`

Sum evidence INSTANCES rather than evidence TYPES: a player seen near two different bodies is more suspicious than near one, so instance counts enter the model additively (this fell out cleanly in a logistic fit). But naively summing per-event log-LRs over an unbounded log double-counts when one behaviour is re-logged as many short intervals, inflating the posterior -- take the MAX log-LR per type, or if you sum, dedup on distinct CONTEXT (per distinct body, per (target,death), per vent visit) not per logged interval, since Naive Bayes assumes independent LRs. Split evidence that is sometimes certain and sometimes ambiguous into TWO types (a hard-proof path that flips the belief, and a separate graded path that accumulates score but is never proof); collapsing both into one boolean either over-accuses or wastes weak signal (e.g. convert the binary empty-then-occupied-vent first-sighting into a graded distance signal, 100% only for the unambiguous case).
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/design.md, personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion-le, claude-code:0e7b14ca-ffd5-4137-9456-47485d3c6f87, codex:019e1591-004e-7040-b768-062bd8e6acd4 (+1)</sub>

#### 5. Don't ship instance-summing on hand-tuned positive-only weights without refit
`crewrift` · **negative result**

NEGATIVE RESULT: do NOT ship a change that SUMS evidence instances (instead of per-type max) on top of existing hand-tuned positive-only weights without refitting. Summing strictly raises posteriors (more evidence => larger sum), lowering the effective vote bar and producing MORE crew mis-votes (ejecting innocents). Land instance-summing only with weights refitted from ground truth, or pair an early ship with an interim guard such as per-type contribution caps or raised vote thresholds.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/suspicion-le, personal_labs/crewrift_lab/WORKING_CONTEXT.md</sub>

#### 6. Replace scalar suspicion with a structured durative event log of raw observations
`crewrift`

Replace a single-scalar-per-player suspicion belief with a structured per-player EVENT LOG: durative observation intervals (room/task/vent dwell, body/player proximity, being-tailed) plus POINT events for witnessed kills/vents, in round-scoped categories (Sighting, Body, Meeting, Alibi). Store only RAW observations and express compound signals like 'followed a victim who then died' as QUERIES over the log plus life-status, never as their own event kind; do not fold 'witnessed near a body' into a single latest timestamp, which discards ordering and co-witness identity that voting/bandwagon reasoning needs. Bridge brief unobserved gaps so a one-tick occlusion blip does not fragment a dwell; split an interval only when you actually SEE the player and the predicate is false. The decision layer reasons over DERIVED PREDICATES materialized on demand ('witness near event', task-location alibi, vote-cluster bandwagon), deferring computable structures (disappearance inference, co-presence windows) to on-demand computation rather than pre-aggregating in v1. Detecting 'X is now dead and was alive last frame' requires this history -- a current-frame-only model is fragile.
  <sub>sources: bitworld/among_them/players/mod_talks/DESIGN.md, bitworld/among_them/players/modulabot/DESIGN.md, personal_labs/crewrift_lab/crewrift/crewborg/design.md, claude-code:25488cd9-61d5-4231-bd87-e2744b6db043 (+2)</sub>

#### 7. Two belief layers (state + raw tape), role-neutral, with retention decoupled from suspicion math
`crewrift`

Maintain two complementary belief layers: aggregate STATE answering 'what is true now' (roster, bodies), and a bounded RING of recent RAW observation frames answering 'what changed between frames'. Store raw frames (not derived views) plus camera position and line-of-sight mask per frame, so occupancy/adjacency are pure functions over the tape and an ABSENCE is distinguishable from 'we weren't looking there'. Build this memory ROLE-NEUTRAL (an imposter benefits too) and gate only the ACTING on it (suspicion -> accuse/vote) to crewmates, so one knowledge layer serves both roles. Manage lifetime by tying it to game boundaries and decoupling retention from suspicion math: bound growth with spatial+temporal dedup (no new sighting if the last entry for that entity was within ~5 ticks / 16 px; ~10x fewer entries), trim raw high-volume events (Sightings, Alibis) at each meeting close once folded into an O(1) per-entity summary, retain sparse high-value events (Bodies, Meetings, outcomes) for the whole round, clear bodies/transient state on meetings, and clear everything at round reset. Do NOT make suspicion math depend on eviction -- that couples calculation to retention and breaks when retention changes.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/design.md, bitworld/among_them/players/mod_talks/DESIGN.md, bitworld/among_them/players/modulabot/DESIGN.md, claude-code:25488cd9-61d5-4231-bd87-e2744b6db043 (+1)</sub>

#### 8. Track other agents' location as a coarse destination-filter belief with negative LOS
`crewrift`

Model each other agent's LOCATION as a probability distribution that collapses to an exact point when in view and is rolled forward when out of view. Because move speed is bounded and movement deterministic, the only real latent is which destination an agent heads to, so the filter collapses to a small categorical over destinations (~15 rooms) rolled forward along precomputed A* polylines -- avoid live-A*-per-room plus Monte-Carlo (expensive, and MC violates a no-RNG/reproducibility norm). Represent it on a COARSE occupancy grid sized to expected path divergence (the grid IS the error model), not pixel-exact prediction which is falsely confident. Sharpen with NEGATIVE line-of-sight: for any cell you can currently see (via the shadow/LOS mask) where the agent is absent, zero that agent's mass there; combined with a reachability disc bounded by max move speed this prunes the distribution for free and makes 'I swept these rooms and didn't see them' work.
  <sub>sources: personal_labs/crewrift_lab/crewrift/crewborg/docs/designs/agent-tracki, claude-code:25488cd9-61d5-4231-bd87-e2744b6db043</sub>

#### 9. Evaluate voting on PAYOFF, and split thresholds that serve opposing role goals
`crewrift` · _see related: S029 (other tier)_

Evaluate a fitted voting model with a held-out decision simulation tied to game PAYOFF, not just AUC. The crewrift model adopted a crewmate-vote threshold of P>=0.9 (no clear-leader rule) because the sim showed ~94-100% imposter precision and net-positive score-per-100-games, while imposter DEFLECTION kept the legacy clear-leader logic because mis-ejecting crew is the imposter's goal. Before changing a shared decision threshold, enumerate its consumers, because one threshold can serve OPPOSING goals per role: raising crewborg's vote bar to P>=0.9 for crew restraint silently flowed into top_suspect's other consumer, the imposter's meeting deflection (which WANTS lower-confidence accusations), making the imposter go silent in a test -- the fix applied the raised bar only when self_role != 'imposter'. General form: grep a threshold's consumers and ask whose objective each one serves.
  <sub>sources: personal_labs/crewrift_lab/WORKING_CONTEXT.md, personal_labs/crewrift_lab/lessons_archive/TENTATIVE_LESSONS-20260612-</sub>

#### 10. Audit the posterior's CONSUMER, exclude self, and accuse from firsthand evidence only
`crewrift` · ⚠ _session-derived, unverified_

When a player misbehaves, separate the suspicion POSTERIOR from its CONSUMERS -- the bug is usually in the consumer. In crewborg the log-odds path correctly produced imposter_confirmed via the witnessed-kill/vent detector (WITNESSED_LOG_LR = ln(1e6); with a 2/7 prior ~0.9999975, logged p 1.0); the misbehavior lived entirely in the mode-selection THRESHOLD. Two concrete consumer bugs: rank suspicion EXCLUDING self (crewborg ranked its own slot/color top suspect at 0.7619, just under the 0.8 vote bar, skipping only by luck -- filter self before it can vote against itself), and signals the parser reads but the strategy never consumes (a parsed vote tally never used to follow an emerging majority; post-death agents falling to generic behavior). Accuse from FIRSTHAND evidence only (witnessed kill > stood-near-body): a baseline accusing 'most recently seen non-self player' is deterministic and exploitable -- an opponent can walk a crewmate past someone right before a body to misdirect the accusation. When auditing a policy, the decision layer is usually the weak point, not perception/navigation.
  <sub>sources: codex:019e8fc7-ebad-7b00-bc95-df1727641ce0, opencode:ses_21ffeb5ffffeA1Pk6sdyHDzwQW, codex:019eaea8-4f78-7072-b4b0-539df963b7df, opencode:ses_224eeb40bffeZqmBRcrjFgPFul</sub>

#### 11. Tag every belief with provenance; never let chat overwrite mechanical truth
`crewrift`

Tag every role/team belief with a PROVENANCE source and treat it by reliability tier, because mechanically-revealed/game-rendered info is ALWAYS truthful while free-text chat can lie. Tiers: mutual role exchange = mechanical truth (confidence 1.0, the only thing satisfying the Persephone win condition); color exchange = high (Spy caveat); behavioral observation = medium; elimination/absence inference = medium-high; chat claims = unverified. As a HARD invariant, never let a lower-confidence chat claim overwrite higher-confidence mechanical knowledge from a server-confirmed exchange or info-screen; the LLM may reason about claims but must not overwrite mechanical truth. Provenance is part of the observation itself -- a minimap sighting must report color+position PLUS a 'came from minimap' flag so the updater treats low-fidelity reports differently from full-fidelity overworld sightings. Store EVIDENCE not collapsed conclusions: prefer {"yellow": {"incriminating":[...],"exculpatory":[...],"chat_mentions":[...]}} over {"yellow":"sus"}, distinguishing hard vs probabilistic, observation vs inference, public vs private, stale vs current, incriminating vs exculpatory vs ambiguous.
  <sub>sources: players_checkouts/players/users/james/personal_cogs/persephone/GAME_AP, players_checkouts/players/users/james/personal_cogs/persephone/README., players_checkouts/players/users/james/personal_cogs/persephone/RULEBOO, personal_cogs/persephone/agents/eurydice/DESIGN.md (+6)</sub>

#### 12. Model perceived identity as uncertain; collapse only when color AND shape are known
`crewrift` · ⚠ _session-derived, unverified_

Model perceived player IDENTITY as explicitly uncertain (candidate set + confidence), never as a known index, because false certainty corrupts everything downstream. Identity is only fully known when BOTH color and shape are observed and classified, but many surfaces are color-only (minimap dots, hostage grid, target picker) and shape is often None (chat senders, speech bubbles, exchange entries); with >8 players colors repeat (10-player default already collides). Eagerly collapsing a color-only observation into one player_index can overwrite a confirmed identity or attach a role reveal to the wrong player -- use an IdentityRef with candidate sets/confidence and reconcile rather than assert. When an interaction has 3+ participants you often cannot attribute an exchange to a single counterpart, so return None and DROP it rather than mis-attribute, and test that gap explicitly so a later 'fix' does not start guessing.
  <sub>sources: codex:019dfe49-9c5e-76c0-86b8-99fbc2cf01b3, codex:019e067b-643a-7100-abdb-8d6a0c79d242</sub>

#### 13. Spy roles invert the cheap signal: trust only mutual role exchange; verify constants vs composition
`crewrift`

When a deduction game has a 'Spy'-type role, its color reveal and visual team indicator show the OPPOSITE (enemy) team, while only its one-way role reveal and a CONSENT-COMPLETED mutual role exchange show the truth. Treat color/team signals as untrustworthy for Spy detection and trust only the mutual exchange (or explicit role label) for allegiance -- completing it confirms a partner is genuine AND satisfies the win condition. When any role CAN fake the cheap signal, model it as unreliable team-wide (a Spy showing the wrong color weakens every color-exchange trust signal for everyone) and budget for the costly mutual-exchange path; when no such role is present, do not pay for error that cannot occur. Verify baked-in confidence constants against the ACTUAL default composition: a doc hardcoded team_confidence 0.9 for ~10% Spy error, but the default roster has NO Spy so the real error is 0%, encoding a false assumption. Capture global MATCH COMPOSITION early and use it as a prior (in a standard 10-player Persephone game, 5 Shades + 5 Nymphs across two rooms, expect ~2-3 teammates in your room) to budget how many color-exchange probes are worth running.
  <sub>sources: players_checkouts/players/users/james/personal_cogs/persephone/RULEBOO, players_checkouts/players/users/james/personal_cogs/persephone/agents/, players_checkouts/players/users/james/personal_cogs/persephone/agents/, codex:019e067b-643a-7100-abdb-8d6a0c79d242 (+4)</sub>

#### 14. Spy exchange discipline and behavioral role inference; conceal high-value intel
`crewrift`

Playing a Spy: NEVER accept a mutual role exchange from an enemy or unknown (it exposes the 'Spy' label), but DO accept one early with a confirmed real teammate so exactly one ally knows the truth -- the only reliable verification of a Spy's allegiance. Beware the refusal tell: a normal grunt accepts exchanges freely, so a Spy that repeatedly declines R.OFFERs is suspicious; balance cover by accepting with real allies rather than blanket-refusing. An objective-less grunt can safely reveal team and role ('just a grunt' tells the enemy nothing) and should exploit this to verify others and build false trust. Derive opponent role hypotheses from ACCUMULATED behavioral patterns, not single observations: approaching only same-team players => key role/searcher; refusing an exchange => key role or Spy; offering one within ~48 ticks of whisper entry => eager searcher; avoiding interaction => Persephone protecting her identity; chatty in global => grunt or decoy. Halve confidence for single-datapoint flags, and treat 'avoids interaction' as meaningful only when the player was genuinely observable (high visible-tick count). Identifying the enemy key role (Hades) is the highest-value intel, so VERIFY an ally via mutual exchange before sharing it, and do NOT signal you know a high-value target -- relay it privately.
  <sub>sources: players_checkouts/players/users/james/personal_cogs/persephone/agents/, players_checkouts/players/users/james/personal_cogs/persephone/agents/, personal_cogs/persephone/agents/eurydice/DESIGN.md, players_checkouts/players/users/james/personal_cogs/persephone/agents/ (+1)</sub>

#### 15. Keep the belief-UPDATE phase mechanical, per-view, with a preservation rule and lobby reset
`crewrift`

Keep the belief-UPDATE phase strictly MECHANICAL: record chat verbatim, populate fields from perception, tag provenance, but make NO inferences, trust judgments, or strategic assessments (those belong to modes or the outer loop). Use a 'preservation rule': only fields explicitly named in a view's update rules change; everything else carries over unchanged from the prior tick, so partial-view frames never silently wipe accumulated knowledge. Specify update behavior PER PERCEIVED VIEW, not as a flat field schema -- a field-list-only schema hid gaps like an identity field never set and a win-condition field with no update rule. A framework typically updates only from instantaneous sensory data, so aggregating momentary updates into persistent multi-tick behavioral inferences (the single strongest social-deduction signal) is the PLAYER's job in a post-update/pre-decide hook. On detecting the LOBBY view for the first time after a non-lobby view, RESET the entire belief state to handle the game-over-to-new-game transition.
  <sub>sources: orpheus/DESIGN.md (Orpheus agent framework design), opencode:ses_201713d2dffe7pZ6AcZMDZXvNZ, opencode:ses_1fb8906dcffete6Fy63Vc7IEPv</sub>

#### 16. Stand up a typed core-data-types layer first; audit the schema against real mechanics
`crewrift` · ⚠ _session-derived, unverified_

For a rule-based deduction agent, stand up a deliberate 'core data types' layer FIRST and in isolation before behavior: a typed per-player knowledge record keyed by stable color (last-known location, alive/dead status, role-if-known, interactions), a global strategic-state object, per-round accumulators with an explicit reset_for_new_round, a dead-body-to-color mapper, and a central registry of belief_state.ext keys as documented string constants (free-form ext dicts are easy to typo and hard to grep). Structure belief as named sub-models (identity, spatial, temporal, per-player, comms) not a flat blob, and distinguish transient per-tick observations (currently-visible chatroom occupants -> per-tick rebuilt SET) from persistent registry state so stale presence never lingers. Audit the schema against ACTUAL game mechanics in BOTH directions: generic templates silently OMIT game-critical state (tick/version, room size, cooldowns, pending offers/role-swap, chatroom occupants, entry requests, menu state, hostage selections, mechanical evidence, source/confidence on claims) and CARRY dead fields the game has no mechanic for (an 'alive' field with no death mechanic). Derive fields by enumerating a full match timeline per role and cross-check every field against a real source of truth, removing any with none.
  <sub>sources: codex:019e05c4-f9e2-74d0-bcd3-53bbf33c209b, opencode:ses_20aad554dffe3dzhaUQ8zuBnZT, opencode:ses_2051bd225ffefNc9y2aOEEFjHW, opencode:ses_201713d2dffe7pZ6AcZMDZXvNZ (+1)</sub>

#### 17. Verify the game actually exposes a signal before modeling evidence on it
`crewrift` · **negative result** · ⚠ _session-derived, unverified_

NEGATIVE RESULT / discipline: before implementing ANY perception-derived evidence signal, verify what the game actually exposes -- the naive interpretation is often wrong and collapses the signal. Feed game-rule INVARIANTS into bug analysis early, because an internally consistent report can rest on a false premise: a hypothesis that 'the agent sees and chases other players' tasks' was flatly wrong because any task icon in vision is by definition the agent's OWN, reframing the symptom as a navigation/rect-containment bug. Gate every event-stream schema feature on whether the underlying perception supplies the signal: defer features whose signal does not exist (chat speaker-attribution for who-accused-whom) but implement ones whose signal IS available (vote-screen who-voted-for-whom), reserving a schema slot for each blocked signal. Before adding a strategy branch on a perceived distinction, confirm the belief contract RETAINS it (the HUD ghost icon maps to self_role=='dead' without distinguishing dead imposter vs crewmate, so a strategy cannot branch on that). Also audit for fields exposed and scored but NEVER populated -- a timesWitnessedKill field fed the LLM prompt and heuristic yet no code incremented it; grep for WRITERS of each signal, not just readers.
  <sub>sources: opencode:ses_21f5b8db7ffe8xs4COwtdx913c, opencode:ses_1ff325156ffei2UiDygaVOZo5O, opencode:ses_21fdab7c0ffeyW9gOCR3FyrI7b, codex:019ea961-a6a9-7f42-ba2e-c8b65df11c22 (+1)</sub>

#### 18. Verified Among Them game constants (manifest 0.1.20)
`crewrift`

Verified Among Them game constants (manifest version 0.1.20): screen 128x128, 4-bit PICO-8 palette; 8 player slots (max 16); imposterCount 2; tasksPerPlayer 8; one emergency-button call per player; voteTimerTicks 6000; killCooldownTicks 900; taskCompleteTicks 72; messageCooldownTicks 100; maxTicks 10000; killRange 20, ventRange 16, reportRange 20 pixels.
  <sub>sources: players_checkouts/players/archive/players/among_them/coborg/PLAN.md</sub>

#### 19. Measure the strong-imposter/weak-crew league asymmetry; model allies in three tiers
`crewrift` · ⚠ _session-derived, unverified_

Strong-imposter / weak-crew asymmetry is a recognizable league signature worth measuring: over 86 episodes imposters won ~53% vs crew ~11%. Meeting chat mainly helps imposters survive votes, while crew need BOTH task efficiency AND good vote selection, making crew the harder, higher-leverage thing to improve. Win-score buckets can estimate the role split heuristically (~100-115 = crew win, >115 = imposter win). Relatedly, model allies in THREE tiers rather than a binary self-vs-other split: (1) self-policy agents identified via the talk handshake, (2) 'coordinators' -- likely allies inferred from behavior even without the handshake, and (3) uncooperative agents; document the talk-handshake variant in the game info docs.
  <sub>sources: claude-code:d48f9347-7884-4ea2-8659-230051d86410, claude-code:829e80cb-6031-4b81-af72-52b3a12289f3</sub>
