bitrouter 1.0.0-alpha.32

BitRouter: an LLM API router. CLI + assembly library.
Documentation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
use std::collections::BTreeMap;
use std::fs::{self, File, OpenOptions};
use std::io::{BufRead, BufReader, BufWriter, Write};
use std::path::{Path, PathBuf};
use std::sync::Mutex;

use bitrouter_sdk::language_model::types::ReasoningEffort;
use bitrouter_sdk::{BitrouterError, Result};
use chrono::Utc;
use serde::{Deserialize, Serialize};
use sha2::{Digest, Sha256};

use crate::eval::types::{EvalExperimentRef, RouteDecisionMeasurement};
use crate::workflow_state::ir::WorkflowIdentity;

pub const POLICY_DECISION_JSONL_ENV: &str = "BITROUTER_POLICY_DECISION_JSONL";

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct PolicyDecisionRecord {
    #[serde(default)]
    pub captured_at: Option<String>,
    #[serde(default)]
    pub request_id: Option<String>,
    /// Domain-separated commitment to the ingress HTTP request identity.
    /// Guarded policies keep `request_id` owner-opaque; this commitment lets
    /// external evidence perform an exact join without persisting the raw ID.
    #[serde(default)]
    pub ingress_request_id_sha256: Option<String>,
    pub input_model: String,
    #[serde(default)]
    pub input_effort: Option<ReasoningEffort>,
    pub key_strategy: String,
    /// Primary canonical policy projection considered before sparse fallback.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub route_projection: Option<String>,
    pub request_key: String,
    /// Database key for adequacy state. Named policies namespace this while
    /// keeping `request_key` human-readable. Old records omit it.
    #[serde(default)]
    pub ledger_key: Option<String>,
    /// Named lock policy that made the decision.
    #[serde(default)]
    pub policy: Option<String>,
    /// Semantic digest of the active policy lock.
    #[serde(default)]
    pub policy_digest: Option<String>,
    /// Effective preset variant, when known.
    #[serde(default)]
    pub preset_variant: Option<String>,
    /// Strong/default comparison tier used by evaluators.
    #[serde(default)]
    pub baseline_tier: Option<String>,
    #[serde(default)]
    pub baseline_effort: Option<ReasoningEffort>,
    pub legacy_fingerprint: String,
    #[serde(rename = "trace_state", alias = "workflow_state")]
    pub workflow_state: String,
    #[serde(rename = "trace_identity", default, alias = "workflow_identity")]
    pub workflow_identity: WorkflowIdentity,
    #[serde(default)]
    pub static_tier: Option<String>,
    #[serde(default)]
    pub static_model: Option<String>,
    #[serde(default)]
    pub static_effort: Option<ReasoningEffort>,
    #[serde(default)]
    pub selected_tier: Option<String>,
    #[serde(default)]
    pub selected_model: Option<String>,
    #[serde(default)]
    pub selected_effort: Option<ReasoningEffort>,
    #[serde(default)]
    pub continuation_proposed_tier: Option<String>,
    #[serde(default)]
    pub continuation_proposed_model: Option<String>,
    #[serde(default)]
    pub continuation_proposed_effort: Option<ReasoningEffort>,
    #[serde(default)]
    pub continuation_adjustment: Option<String>,
    #[serde(default)]
    pub predicted_role: Option<String>,
    #[serde(default)]
    pub predicted_task_family: Option<String>,
    #[serde(default)]
    pub predicted_action: Option<String>,
    #[serde(default)]
    pub prediction_confidence_ppm: Option<u32>,
    #[serde(default)]
    pub task_family_confidence_ppm: Option<u32>,
    #[serde(default)]
    pub predictor_contract_digest: Option<String>,
    #[serde(default)]
    pub prediction_confidence_kind: Option<String>,
    #[serde(default)]
    pub prediction_reason_codes: Vec<String>,
    #[serde(default)]
    pub task_family_reason_codes: Vec<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub experiment: Option<EvalExperimentRef>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub route_measurement: Option<RouteDecisionMeasurement>,
    #[serde(default)]
    pub observed_route_projection: Option<String>,
    #[serde(default)]
    pub trajectory_episode_id: Option<String>,
    #[serde(default)]
    pub trajectory_sequence: Option<u64>,
    #[serde(default)]
    pub trajectory_completeness: Option<String>,
    #[serde(default)]
    pub trajectory_health_digest: Option<String>,
    #[serde(default)]
    pub candidate_tier: Option<String>,
    #[serde(default)]
    pub progress_clause_ids: Vec<String>,
    pub reason: String,
    pub pinned: bool,
    #[serde(default)]
    pub request_qualified: bool,
    #[serde(default)]
    pub semantic_successes: u32,
    #[serde(default)]
    pub semantic_success_threshold: u32,
    pub locked: bool,
    pub trialed: bool,
}

pub fn ingress_request_id_sha256(request_id: &str) -> String {
    let mut digest = Sha256::new();
    digest.update(b"bitrouter.ingress-request-id.v1\0");
    digest.update(request_id.as_bytes());
    format!("sha256:{}", hex::encode(digest.finalize()))
}

#[derive(Debug, Default, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct PolicyDecisionSummary {
    pub total: usize,
    pub routed_count: usize,
    pub pinned_count: usize,
    pub locked_count: usize,
    pub trialed_count: usize,
    pub by_selected_tier: BTreeMap<String, usize>,
    pub by_selected_model: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_selected_effort: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_selected_target: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_predicted_role: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_predicted_task_family: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_predicted_action: BTreeMap<String, usize>,
    pub static_tier_replaced_count: usize,
    pub static_model_replaced_count: usize,
    #[serde(default)]
    pub static_effort_replaced_count: usize,
    pub by_tier_transition: BTreeMap<String, usize>,
    pub by_model_transition: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_effort_transition: BTreeMap<String, usize>,
    #[serde(default)]
    pub by_target_transition: BTreeMap<String, usize>,
    pub replacement_by_reason: BTreeMap<String, usize>,
    pub by_reason: BTreeMap<String, usize>,
    #[serde(rename = "by_trace_state", alias = "by_workflow_state")]
    pub by_workflow_state: BTreeMap<String, usize>,
    pub by_agent_role: BTreeMap<String, usize>,
    pub by_context_epoch: BTreeMap<u32, usize>,
}

pub struct PolicyDecisionJsonlRecorder {
    path: PathBuf,
    lock: Mutex<()>,
}

impl PolicyDecisionRecord {
    /// Canonical JSON calls this field `trace_state`; this accessor lets newer
    /// Rust callers use the canonical terminology without breaking older field
    /// access or struct literals.
    pub fn trace_state(&self) -> &str {
        &self.workflow_state
    }

    /// Canonical JSON calls this field `trace_identity`; this accessor lets
    /// newer Rust callers use that terminology without breaking older callers.
    pub fn trace_identity(&self) -> &WorkflowIdentity {
        &self.workflow_identity
    }

    pub fn captured_now(mut self) -> Self {
        self.captured_at = Some(Utc::now().to_rfc3339());
        self
    }

    pub fn load_jsonl(path: impl AsRef<Path>) -> Result<Vec<Self>> {
        let file = File::open(path.as_ref()).map_err(|e| {
            BitrouterError::internal(format!(
                "policy decision jsonl open {}: {e}",
                path.as_ref().display()
            ))
        })?;
        let reader = BufReader::new(file);
        let mut records = Vec::new();
        for (idx, line) in reader.lines().enumerate() {
            let line = line.map_err(|e| {
                BitrouterError::internal(format!(
                    "policy decision jsonl read {}: {e}",
                    path.as_ref().display()
                ))
            })?;
            let trimmed = line.trim();
            if trimmed.is_empty() {
                continue;
            }
            records.push(serde_json::from_str(trimmed).map_err(|e| {
                BitrouterError::bad_request(format!(
                    "policy decision jsonl parse {} line {}: {e}",
                    path.as_ref().display(),
                    idx + 1
                ))
            })?);
        }
        Ok(records)
    }

    pub fn write_jsonl(path: impl AsRef<Path>, records: &[Self]) -> Result<()> {
        if let Some(parent) = path.as_ref().parent()
            && !parent.as_os_str().is_empty()
        {
            fs::create_dir_all(parent).map_err(|e| {
                BitrouterError::internal(format!(
                    "policy decision jsonl mkdir {}: {e}",
                    parent.display()
                ))
            })?;
        }
        let file = File::create(path.as_ref()).map_err(|e| {
            BitrouterError::internal(format!(
                "policy decision jsonl create {}: {e}",
                path.as_ref().display()
            ))
        })?;
        let mut writer = BufWriter::new(file);
        for record in records {
            serde_json::to_writer(&mut writer, record).map_err(|e| {
                BitrouterError::internal(format!("policy decision jsonl serialize: {e}"))
            })?;
            writer.write_all(b"\n").map_err(|e| {
                BitrouterError::internal(format!("policy decision jsonl write: {e}"))
            })?;
        }
        writer
            .flush()
            .map_err(|e| BitrouterError::internal(format!("policy decision jsonl flush: {e}")))
    }
}

impl PolicyDecisionSummary {
    pub fn from_records(records: &[PolicyDecisionRecord]) -> Self {
        let mut summary = Self {
            total: records.len(),
            ..Self::default()
        };
        for record in records {
            if record.selected_model.is_some() {
                summary.routed_count += 1;
            }
            if record.pinned {
                summary.pinned_count += 1;
            }
            if record.locked {
                summary.locked_count += 1;
            }
            if record.trialed {
                summary.trialed_count += 1;
            }
            if let Some(tier) = record.selected_tier.as_deref() {
                *summary
                    .by_selected_tier
                    .entry(tier.to_string())
                    .or_insert(0) += 1;
            }
            if let (Some(static_tier), Some(selected_tier)) = (
                record.static_tier.as_deref(),
                record.selected_tier.as_deref(),
            ) {
                *summary
                    .by_tier_transition
                    .entry(transition_key(static_tier, selected_tier))
                    .or_insert(0) += 1;
                if static_tier != selected_tier {
                    summary.static_tier_replaced_count += 1;
                    *summary
                        .replacement_by_reason
                        .entry(record.reason.clone())
                        .or_insert(0) += 1;
                }
            }
            if let Some(model) = record.selected_model.as_deref() {
                *summary
                    .by_selected_model
                    .entry(model.to_string())
                    .or_insert(0) += 1;
                *summary
                    .by_selected_target
                    .entry(target_key(model, record.selected_effort))
                    .or_insert(0) += 1;
            }
            if let Some(effort) = record.selected_effort {
                *summary
                    .by_selected_effort
                    .entry(effort.to_string())
                    .or_insert(0) += 1;
            }
            if let Some(role) = record.predicted_role.as_deref() {
                *summary
                    .by_predicted_role
                    .entry(role.to_string())
                    .or_insert(0) += 1;
            }
            if let Some(task_family) = record.predicted_task_family.as_deref() {
                *summary
                    .by_predicted_task_family
                    .entry(task_family.to_string())
                    .or_insert(0) += 1;
            }
            if let Some(action) = record.predicted_action.as_deref() {
                *summary
                    .by_predicted_action
                    .entry(action.to_string())
                    .or_insert(0) += 1;
            }
            if let (Some(static_model), Some(selected_model)) = (
                record.static_model.as_deref(),
                record.selected_model.as_deref(),
            ) {
                *summary
                    .by_model_transition
                    .entry(transition_key(static_model, selected_model))
                    .or_insert(0) += 1;
                if static_model != selected_model {
                    summary.static_model_replaced_count += 1;
                }
                *summary
                    .by_target_transition
                    .entry(transition_key(
                        &target_key(static_model, record.static_effort),
                        &target_key(selected_model, record.selected_effort),
                    ))
                    .or_insert(0) += 1;
            }
            if record.static_effort.is_some() || record.selected_effort.is_some() {
                *summary
                    .by_effort_transition
                    .entry(transition_key(
                        effort_key(record.static_effort),
                        effort_key(record.selected_effort),
                    ))
                    .or_insert(0) += 1;
                if record.static_effort != record.selected_effort {
                    summary.static_effort_replaced_count += 1;
                }
            }
            *summary.by_reason.entry(record.reason.clone()).or_insert(0) += 1;
            *summary
                .by_workflow_state
                .entry(record.workflow_state.clone())
                .or_insert(0) += 1;
            *summary
                .by_agent_role
                .entry(record.workflow_identity.role.as_str().to_string())
                .or_insert(0) += 1;
            *summary
                .by_context_epoch
                .entry(record.workflow_identity.context_epoch)
                .or_insert(0) += 1;
        }
        summary
    }
}

fn transition_key(from: &str, to: &str) -> String {
    format!("{from} -> {to}")
}

fn effort_key(effort: Option<ReasoningEffort>) -> &'static str {
    effort.map_or("inherit", ReasoningEffort::as_str)
}

fn target_key(model: &str, effort: Option<ReasoningEffort>) -> String {
    format!("{model}@{}", effort_key(effort))
}

impl PolicyDecisionJsonlRecorder {
    pub fn new(path: impl Into<PathBuf>) -> Result<Self> {
        let path = path.into();
        if let Some(parent) = path.parent()
            && !parent.as_os_str().is_empty()
        {
            fs::create_dir_all(parent).map_err(|e| {
                BitrouterError::internal(format!(
                    "policy decision recorder mkdir {}: {e}",
                    parent.display()
                ))
            })?;
        }
        Ok(Self {
            path,
            lock: Mutex::new(()),
        })
    }

    pub fn from_env() -> Result<Option<Self>> {
        let Some(path) =
            std::env::var_os(POLICY_DECISION_JSONL_ENV).filter(|value| !value.is_empty())
        else {
            return Ok(None);
        };
        Self::new(PathBuf::from(path)).map(Some)
    }

    pub fn record(&self, record: &PolicyDecisionRecord) -> Result<()> {
        let _guard = self.lock.lock().map_err(|_| {
            BitrouterError::internal("policy decision recorder lock poisoned".to_string())
        })?;
        let mut file = OpenOptions::new()
            .create(true)
            .append(true)
            .open(&self.path)
            .map_err(|e| {
                BitrouterError::internal(format!(
                    "policy decision jsonl append {}: {e}",
                    self.path.display()
                ))
            })?;
        serde_json::to_writer(&mut file, record).map_err(|e| {
            BitrouterError::internal(format!("policy decision jsonl serialize: {e}"))
        })?;
        file.write_all(b"\n")
            .map_err(|e| BitrouterError::internal(format!("policy decision jsonl write: {e}")))
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn record() -> PolicyDecisionRecord {
        PolicyDecisionRecord {
            captured_at: None,
            request_id: Some("request-1".to_string()),
            ingress_request_id_sha256: None,
            input_model: "inbound".to_string(),
            input_effort: None,
            key_strategy: "agent_trace".to_string(),
            route_projection: None,
            request_key: "agent_trace/v1|tool_followup|normal".to_string(),
            ledger_key: Some("agent_trace/v1|tool_followup|normal".to_string()),
            policy: None,
            policy_digest: None,
            preset_variant: None,
            baseline_tier: Some("capable".to_string()),
            baseline_effort: None,
            legacy_fingerprint: "after_read_file".to_string(),
            workflow_state: "tool_followup".to_string(),
            workflow_identity: WorkflowIdentity::default(),
            static_tier: Some("capable".to_string()),
            static_model: Some("vendor/capable".to_string()),
            static_effort: None,
            selected_tier: Some("cheap".to_string()),
            selected_model: Some("vendor/cheap".to_string()),
            selected_effort: None,
            continuation_proposed_tier: None,
            continuation_proposed_model: None,
            continuation_proposed_effort: None,
            continuation_adjustment: None,
            predicted_role: None,
            predicted_task_family: None,
            predicted_action: None,
            prediction_confidence_ppm: None,
            task_family_confidence_ppm: None,
            predictor_contract_digest: None,
            prediction_confidence_kind: None,
            prediction_reason_codes: Vec::new(),
            task_family_reason_codes: Vec::new(),
            experiment: None,
            route_measurement: None,
            observed_route_projection: None,
            trajectory_episode_id: None,
            trajectory_sequence: None,
            trajectory_completeness: None,
            trajectory_health_digest: None,
            candidate_tier: None,
            progress_clause_ids: Vec::new(),
            reason: "static_table".to_string(),
            pinned: false,
            request_qualified: true,
            semantic_successes: 1,
            semantic_success_threshold: 0,
            locked: false,
            trialed: false,
        }
    }

    #[test]
    fn decision_records_emit_trace_names_and_read_legacy_workflow_names() {
        let value = serde_json::to_value(record()).unwrap();
        assert_eq!(value["trace_state"], "tool_followup");
        assert!(value.get("workflow_state").is_none());
        assert!(value.get("trace_identity").is_some());
        assert!(value.get("workflow_identity").is_none());

        let mut legacy = serde_json::to_value(record()).unwrap();
        let object = legacy.as_object_mut().unwrap();
        let state = object.remove("trace_state").unwrap();
        let identity = object.remove("trace_identity").unwrap();
        object.insert("workflow_state".to_string(), state);
        object.insert("workflow_identity".to_string(), identity);
        let parsed: PolicyDecisionRecord = serde_json::from_value(legacy).unwrap();
        assert_eq!(parsed.workflow_state, "tool_followup");
        assert_eq!(parsed.workflow_identity, WorkflowIdentity::default());
    }

    #[test]
    fn decision_record_reads_legacy_jsonl_without_predictive_fields() {
        let legacy = r#"{
            "input_model":"inbound",
            "key_strategy":"agent_trace",
            "request_key":"agent_trace/v1|tool_followup|normal",
            "legacy_fingerprint":"after_read_file",
            "trace_state":"tool_followup",
            "trace_identity":{"role":"unknown","context_epoch":0,"transition":"none","fingerprint":"","source":"","confidence":"none"},
            "reason":"static_table",
            "pinned":false,
            "locked":false,
            "trialed":false
        }"#;

        let parsed: PolicyDecisionRecord = serde_json::from_str(legacy).unwrap();

        assert_eq!(parsed.route_projection, None);
        assert_eq!(parsed.predicted_role, None);
        assert_eq!(parsed.predicted_task_family, None);
        assert_eq!(parsed.predicted_action, None);
        assert_eq!(parsed.prediction_confidence_ppm, None);
        assert_eq!(parsed.task_family_confidence_ppm, None);
        assert_eq!(parsed.predictor_contract_digest, None);
        assert_eq!(parsed.prediction_confidence_kind, None);
        assert_eq!(parsed.prediction_reason_codes, Vec::<String>::new());
        assert_eq!(parsed.task_family_reason_codes, Vec::<String>::new());
        assert_eq!(parsed.observed_route_projection, None);
        assert_eq!(parsed.ingress_request_id_sha256, None);
        assert_eq!(parsed.input_effort, None);
        assert_eq!(parsed.selected_effort, None);
    }

    #[test]
    fn decision_record_serializes_compound_effort_treatment() -> anyhow::Result<()> {
        let mut decision = record();
        decision.input_effort = Some(ReasoningEffort::High);
        decision.static_effort = Some(ReasoningEffort::Low);
        decision.selected_effort = Some(ReasoningEffort::Medium);
        decision.baseline_effort = Some(ReasoningEffort::High);
        decision.continuation_proposed_effort = Some(ReasoningEffort::Low);

        let value = serde_json::to_value(&decision)?;

        assert_eq!(value["input_effort"], "high");
        assert_eq!(value["static_effort"], "low");
        assert_eq!(value["selected_effort"], "medium");
        assert_eq!(value["baseline_effort"], "high");
        assert_eq!(value["continuation_proposed_effort"], "low");
        Ok(())
    }

    #[test]
    fn ingress_request_commitment_is_domain_separated_and_does_not_expose_raw_id() {
        let raw = "br-bench-sensitive-request-id";
        let digest = ingress_request_id_sha256(raw);

        assert!(digest.starts_with("sha256:"));
        assert_eq!(digest.len(), 71);
        assert!(!digest.contains(raw));
        assert_ne!(digest, ingress_request_id_sha256("other-request-id"));
    }

    #[test]
    fn summary_emits_by_trace_state_and_reads_legacy_workflow_summary() {
        let summary = PolicyDecisionSummary::from_records(&[record()]);
        assert_eq!(summary.by_workflow_state["tool_followup"], 1);
        let value = serde_json::to_value(&summary).unwrap();
        assert!(value.get("by_trace_state").is_some());
        assert!(value.get("by_workflow_state").is_none());

        let mut legacy = serde_json::to_value(&summary).unwrap();
        let object = legacy.as_object_mut().unwrap();
        let states = object.remove("by_trace_state").unwrap();
        object.insert("by_workflow_state".to_string(), states);
        let parsed: PolicyDecisionSummary = serde_json::from_value(legacy).unwrap();
        assert_eq!(parsed.by_workflow_state["tool_followup"], 1);
    }

    #[test]
    fn summary_reads_old_json_without_predictive_dimensions() {
        let legacy = r#"{
            "total":1,
            "routed_count":1,
            "pinned_count":0,
            "locked_count":0,
            "trialed_count":0,
            "by_selected_tier":{"cheap":1},
            "by_selected_model":{"vendor/cheap":1},
            "static_tier_replaced_count":0,
            "static_model_replaced_count":0,
            "by_tier_transition":{"cheap->cheap":1},
            "by_model_transition":{"vendor/cheap->vendor/cheap":1},
            "replacement_by_reason":{},
            "by_reason":{"static_table":1},
            "by_trace_state":{"tool_followup":1},
            "by_agent_role":{"unknown":1},
            "by_context_epoch":{"0":1}
        }"#;

        let parsed: PolicyDecisionSummary = serde_json::from_str(legacy).unwrap();

        assert_eq!(parsed.by_predicted_role, BTreeMap::new());
        assert_eq!(parsed.by_predicted_task_family, BTreeMap::new());
        assert_eq!(parsed.by_predicted_action, BTreeMap::new());
        assert_eq!(parsed.by_selected_effort, BTreeMap::new());
        assert_eq!(parsed.by_selected_target, BTreeMap::new());
    }

    #[test]
    fn summary_distinguishes_same_model_at_different_efforts() {
        let mut low = record();
        low.static_model = Some("vendor/model".into());
        low.selected_model = Some("vendor/model".into());
        low.static_effort = Some(ReasoningEffort::High);
        low.selected_effort = Some(ReasoningEffort::Low);
        let mut high = low.clone();
        high.selected_effort = Some(ReasoningEffort::High);

        let summary = PolicyDecisionSummary::from_records(&[low, high]);

        assert_eq!(summary.by_selected_model.get("vendor/model"), Some(&2));
        assert_eq!(summary.by_selected_target.get("vendor/model@low"), Some(&1));
        assert_eq!(
            summary.by_selected_target.get("vendor/model@high"),
            Some(&1)
        );
        assert_eq!(summary.static_effort_replaced_count, 1);
    }

    #[test]
    fn summary_does_not_treat_inherited_effort_as_a_router_replacement() {
        let mut inherited = record();
        inherited.input_effort = Some(ReasoningEffort::Low);
        inherited.static_model = Some("vendor/model".into());
        inherited.selected_model = Some("vendor/model".into());
        inherited.static_effort = Some(ReasoningEffort::Low);
        inherited.selected_effort = Some(ReasoningEffort::Low);

        let summary = PolicyDecisionSummary::from_records(&[inherited]);

        assert_eq!(summary.static_effort_replaced_count, 0);
        assert_eq!(summary.by_selected_target.get("vendor/model@low"), Some(&1));
    }

    #[test]
    fn summary_counts_predictions_and_selected_model_exposure() {
        let mut predicted = record();
        predicted.predicted_role = Some("implement".to_string());
        predicted.predicted_task_family = Some("code:review".to_string());
        predicted.predicted_action = Some("mutate".to_string());
        predicted.selected_model = Some("vendor/cheap".to_string());

        let mut unpredicted = record();
        unpredicted.selected_model = Some("vendor/flagship".to_string());

        let summary = PolicyDecisionSummary::from_records(&[predicted, unpredicted]);

        assert_eq!(
            summary.by_predicted_role,
            BTreeMap::from([("implement".to_string(), 1)])
        );
        assert_eq!(
            summary.by_predicted_task_family,
            BTreeMap::from([("code:review".to_string(), 1)])
        );
        assert_eq!(
            summary.by_predicted_action,
            BTreeMap::from([("mutate".to_string(), 1)])
        );
        assert_eq!(
            summary.by_selected_model,
            BTreeMap::from([
                ("vendor/cheap".to_string(), 1),
                ("vendor/flagship".to_string(), 1),
            ])
        );
    }
}