System: First run over fences from a yard that schools them

Mechanism and rationale

A horse's first chase is the least predictable run of its career, and yards differ in how well prepared their chase debutants are. A yard's record with them carries forward.

The rule

race_type = 'Chase' AND is_handicap = 1 AND prior_chase_runs = 0 AND last_race_type IS NOT NULL AND yard_chase_debut_runs >= 15 AND yard_chase_debut_wins >= 1.3 * yard_chase_debut_expected

Reads: race_type, is_handicap, prior_chase_runs, last_race_type, yard_chase_debut_runs, yard_chase_debut_wins, yard_chase_debut_expected

Pre-registration

Spec hash (sha256 of the canonical pre-spec)

not designed yet

Frozen

not frozen

The definition can still change.

Backing

price-sensitive

Kind

system

Live from

2026-10-13

Matched

none

Published

true

Rules

• The race is a handicap chase and the horse has never run in a chase, but has run before.
• The yard's earlier chase debutants (at least 15) won 30% more often than their prices implied.

Source

Yard patterns, October 2026

System id

chase-debut-from-a-good-yard

Tier

none

Where

race_type = 'Chase' AND is_handicap = 1 AND prior_chase_runs = 0 AND last_race_type IS NOT NULL AND yard_chase_debut_runs >= 15 AND yard_chase_debut_wins >= 1.3 * yard_chase_debut_expected

Discovery result

Not measured yet.

Falsification

No attacks yet. Only promising ideas are attacked.

Sealed holdout (vault)

Not queried. Only a frozen idea can spend its one query against the 2020-25 holdout.

Forward record

No forward record. Shadow tracking starts after the vault and counts only races run after the freeze.

Lineage

No parent and no descendants yet. When an agent mutates, generalises or splits this idea, the new hypotheses appear here.

Agent runs

• investigator v1ok · 1m 2s · 17 Oct, 02:38

  Output (schema-checked)

  {
    "reflection": "The thread has narrowed to one claim: a held-up pull-up loses its meaning when the horse switches code (H-070b2026, 1.359 on 304, in shadow with no forward bets yet). These observations say the lift is not specific to the pull-up or to one direction of switch. First, chase debutants after a hurdle run beaten 20 lengths or more, with pull-ups excluded, scored 1.24 on 335 (p 0.116, same-race control 0.97, CI 0.87 to 1.71). That is a wider pool than the pull-up-only sharpen H-fbabeb50 (1.50 on 76), and the lift is smaller. Second, held-up chase pull-ups dropped back to hurdles scored 1.38 on 150 (p 0.17). So fences being taken away also shows a lift. Read together, the thread points away from 'a held-up pull-up hides ability' and towards 'a bad last run in the other code is over-read'. For chasing debutants this sits against the killed H124: fit, winning hurdlers on their chase debut scored 0.924. The market seems to price good hurdle form properly and under-price bad hurdle form. Two cautions. Both new pools are thin and neither clears p 0.05. The chase-to-hurdle cut has all 12 winners under 16/1 (0 from 94 at 16/1 or bigger) and a BSP ROI of -18.9%, the same under-16/1 concentration seen across the whole thread. And the debutant effect is GB 1.43 on 187 against IRE 0.91 on 148. That split came from a scan, so it is a lead, not a finding, and it should not be used to slice the rule.",
    "answers": [
      {
        "question_id": "Q-8ff53fc4",
        "answer": "Both directions carry a lift: hurdle-to-chase held-up pull-ups scored 1.50 on 76 and chase-to-hurdle 1.38 on 150, so the cause looks like the change of code rather than a first try over fences. The jumping-error part is still untested."
      },
      {
        "question_id": "Q-df939c41",
        "answer": "The evidence leans towards the broader effect: chase debutants after any hurdle beating of 20 lengths or more, pull-ups excluded, scored 1.24 on 335 (control 0.97). The pull-up is not needed, though the pull-up cut ran higher (1.50 on 76) and neither is conclusive."
      }
    ],
    "questions": [
      {
        "question": "Is the chase-debutant lift after a heavy hurdle beating carried by yards that are good at chase debuts, so that it is really the published yard effect (H104, SYS-chase-debut-from-a-good-yard) and not a misread of form?",
        "rationale": "H-448cb451 passed as a niche at 1.24 on 335, and good chase-debut yards already show 1.18. If the debutants come mostly from those yards, the 'bad hurdle form misread' story adds nothing. A scan would read tx_chase_debut_runs, tx_chase_debut_wins, tx_chase_debut_exp, chase_runs, last_beaten_lengths and last_race_type.",
        "observation_ids": [
          "O-7628ef4c",
          "O-69d892e9"
        ],
        "priority": 0.6
      },
      {
        "question": "Is the GB-only concentration of the debutant lift (GB 1.43, IRE 0.91) a property of the race mix, such as GB novice handicap chases or race class, rather than the country?",
        "rationale": "The country split came from a scan. GB debutants run more often in novice handicap chases, where the handicapper's mark after bad hurdle form may be lenient. A descriptive split of region by is_handicap, is_novice, race_class and last_official_rating would show whether a race property explains it before anyone cuts the rule by country.",
        "observation_ids": [
          "O-69d892e9"
        ],
        "priority": 0.4
      },
      {
        "question": "Across every code-switch cut in this thread, does the lift sit entirely under 16/1, and is that more than the general longshot bias of jumps racing?",
        "rationale": "Chase-to-hurdle pull-ups had 0 winners from 94 bets at 16/1 or bigger; H-070b2026 scored 2.22 under 14/1 against 0.55 at 16/1 or bigger; the debutants scored 1.03 at 16/1 or bigger. Comparing the same price bands for all jumps runners with a bad last run (sp_decimal, last_beaten_lengths, last_pulled_up) would show whether this is the mechanism or just the base rate.",
        "observation_ids": [
          "O-3bed9331",
          "O-7628ef4c"
        ],
        "priority": 0.45
      }
    ],
    "hypotheses": [
      {
        "title": "Test-mechanism: chase debutants beaten heavily last time over hurdles but close up earlier",
        "family": "story",
        "operator": "test-mechanism",
        "question_id": "Q-df939c41",
        "new_question": null,
        "parent_id": "H-448cb451",
        "reasoning": {
          "observation_ids": [
            "O-7628ef4c",
            "O-69d892e9"
          ],
          "question": "If the debutant lift comes from the market over-reading one bad hurdle run, is it strongest when the horse finished close within its last three runs?",
          "mechanism": "A horse that was beaten heavily last time but finished within a few lengths in one of the two runs before it has shown ability that the last run hid. The move to fences gives it new conditions in which that ability can come out again.",
          "market_miss": "The race card and punters lead with the last run, so a 20-length beating dominates the price, while the closer run two or three back is discounted. Fit, winning hurdlers (H124, 0.924) are priced correctly, so the error is specific to bad recent form.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.30 to 1.50 on 150+ bets, above the debutants with no close recent run",
            "falsified_if": "A/E below 1.15, or no higher than heavily beaten debutants whose best of the last three runs was also beaten more than 10 lengths"
          },
          "rule_sketch": "last_race_type = 'Hurdle' AND race_type = 'Chase' AND COALESCE(chase_runs, 0) = 0 AND last_beaten_lengths >= 20 AND best_last3_beaten IS NOT NULL AND best_last3_beaten <= 6"
        },
        "confounders": [
          "yard skill with chase debutants",
          "GB race mix",
          "handicap mark dropping after the bad run",
          "price band under 16/1"
        ],
        "expected_survival": 0.35
      },
      {
        "title": "Rival: the debutant lift is the yard's chase-debut skill, not misread hurdle form",
        "family": "story",
        "operator": "rival-explanation",
        "question_id": null,
        "new_question": 0,
        "parent_id": "H-448cb451",
        "reasoning": {
          "observation_ids": [
            "O-7628ef4c",
            "O-69d892e9"
          ],
          "question": "Do heavily beaten chase debutants from yards without a strong chase-debut record still beat their price?",
          "mechanism": "If the cause is the market over-reading bad hurdle form, the lift should appear whoever the trainer is. If it disappears outside the good chase-debut yards, the published yard effect is the real driver.",
          "market_miss": "Bad hurdle form puts the horse out of the betting regardless of the yard. If the lift survives in ordinary yards, the misread is about the form and not about the trainer's schooling.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.15 to 1.30 on 200+ bets if the form-misread story holds",
            "falsified_if": "A/E at or below 1.05 on 150+ bets, which would mean the yard carries the effect and the story adds nothing"
          },
          "rule_sketch": "last_race_type = 'Hurdle' AND race_type = 'Chase' AND COALESCE(chase_runs, 0) = 0 AND last_beaten_lengths >= 20 AND tx_chase_debut_runs >= 15 AND tx_chase_debut_wins < 1.3 * tx_chase_debut_exp"
        },
        "confounders": [
          "yard samples too small and left out by the runs filter",
          "GB/IRE mix",
          "handicap status",
          "price band"
        ],
        "expected_survival": 0.4
      }
    ],
    "findings": [
      {
        "statement": "A pull-up is not needed for the chase-debut lift: chase debutants after any hurdle beating of 20 lengths or more, pull-ups excluded, scored 1.24 on 335 against a same-race control of 0.97 (p 0.116, niche).",
        "kind": "holds",
        "observation_ids": [
          "O-7628ef4c"
        ]
      },
      {
        "statement": "The code-switch lift for held-up pull-ups appears in both directions: held-up chase pull-ups dropped back to hurdles scored 1.38 on 150 (p 0.17), but every winner came under 16/1 (0 from 94 at 16/1 or bigger) and BSP ROI was -18.9%.",
        "kind": "holds",
        "observation_ids": [
          "O-3bed9331"
        ]
      },
      {
        "statement": "The heavily beaten debutant effect is concentrated in GB (1.43 on 187, 27 winners); Ireland scored 0.91 on 148. This came from a scan, so treat it as a lead and not a basis for slicing the rule.",
        "kind": "data",
        "observation_ids": [
          "O-69d892e9"
        ]
      }
    ]
  }

Timeline

1. hypothesis note SYS-chase-debut-from-a-good-yard

   15 Oct, 23:10 · importer

2. New idea SYS-chase-debut-from-a-good-yard: System: First run over fences from a yard that schools them (import)

   15 Oct, 23:10 · importer

Every change is an event with an actor: an agent and its version, an engine, a human, or the importer. Current stage: Live.