CTE Configuration Reference

The Causal Tree Engine is configured via the [causal_tree] section in your PRX config file.

The CTE is disabled by default. All parameters below only take effect when causal_tree.enabled = true.

Full Example

[causal_tree]
enabled = true                  # Master switch (default: false)

# Scoring weights (must sum to 1.0)
w_confidence = 0.50             # Weight for confidence dimension
w_cost = 0.25                   # Weight for cost penalty
w_latency = 0.25                # Weight for latency penalty

# Logging
write_decision_log = true       # Log every CTE decision (default: true)
write_metrics = true            # Collect CTE metrics (default: true)

[causal_tree.policy]
max_branches = 3                # Max candidate branches to expand
commit_threshold = 0.62         # Minimum score to commit a branch
extra_token_ratio_limit = 0.35  # Max CTE overhead as ratio of baseline tokens
extra_latency_budget_ms = 300   # Max additional latency budget (ms)
rehearsal_timeout_ms = 5000     # Per-rehearsal timeout (ms)
default_side_effect_mode = "read_only"  # Rehearsal side-effect mode
circuit_breaker_threshold = 5   # Consecutive failures to trip breaker
circuit_breaker_cooldown_secs = 60  # Cooldown before retry (seconds)

Parameter Reference

Top-Level Parameters

Parameter	Type	Default	Description
enabled	bool	false	Master switch. When false, the CTE is completely bypassed.
w_confidence	f32	0.50	Scoring weight for the confidence dimension. Higher values favor branches the model is more confident about.
w_cost	f32	0.25	Scoring weight for cost penalty. Higher values penalize expensive branches more.
w_latency	f32	0.25	Scoring weight for latency penalty. Higher values penalize slow branches more.
write_decision_log	bool	true	When enabled, emits a structured log entry for every CTE decision via tracing::info!.
write_metrics	bool	true	When enabled, collects CTE performance metrics (hit ratios, latency, etc.).

Policy Parameters ([causal_tree.policy])

Parameter	Type	Default	Description
max_branches	usize	3	Maximum number of candidate branches the expander will generate per request.
commit_threshold	f32	0.62	Minimum composite score required to commit a branch. Branches below this score are rejected.
extra_token_ratio_limit	f32	0.35	Maximum ratio of extra tokens consumed by CTE overhead relative to the baseline request. Exceeding this triggers degradation.
extra_latency_budget_ms	u64	300	Maximum additional latency (in milliseconds) the CTE pipeline is allowed to add.
rehearsal_timeout_ms	u64	5000	Timeout for a single rehearsal run in milliseconds.
default_side_effect_mode	string	"read_only"	Side-effect mode for rehearsals. Options: "read_only", "dry_run", "live".
circuit_breaker_threshold	u32	5	Number of consecutive CTE failures before the circuit breaker trips.
circuit_breaker_cooldown_secs	u64	60	Duration in seconds the circuit breaker stays open before allowing a retry.

Scoring Weights

The three scoring weights (w_confidence, w_cost, w_latency) should sum to 1.0. The composite score for each branch is calculated as:

score = w_confidence * confidence - w_cost * normalized_cost - w_latency * normalized_latency

Tuning tips:

• Cost-sensitive — Increase w_cost (e.g., 0.40) and decrease w_confidence (e.g., 0.40)
• Latency-sensitive — Increase w_latency (e.g., 0.40)
• Quality-first — Increase w_confidence (e.g., 0.70) and decrease others

Side-Effect Modes

Mode	Description
read_only	Rehearsals cannot perform any write operations. Safest option.
dry_run	Rehearsals simulate writes but don't persist them.
live	Rehearsals can perform real writes. Use with caution.

Minimal Configuration

To enable CTE with all defaults:

[causal_tree]
enabled = true

Related Pages

• Causal Tree Engine Overview
• Full Configuration Reference