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Fix MaxTripLegs constraint allowing infinite same-mode expansion #99

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Merged
robfitzgerald merged 4 commits into from
Feb 3, 2026
Merged

Fix MaxTripLegs constraint allowing infinite same-mode expansion #99

robfitzgerald merged 4 commits into from
Feb 3, 2026

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Copilot AI commented Feb 3, 2026 •
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Multimodal search was being killed by the system due to unbounded memory growth during frontier expansion.

Root Cause

The MaxTripLegs constraint in constraint.rs incorrectly validated same-mode edge continuations:

let n_legs = match active_mode {
    Some(active_mode) if active_mode != edge_mode => n_existing_legs + 1,
    _ => 0,  // Bug: same-mode continuation always returns 0 legs
};
let is_valid = n_legs <= *max_legs;

When active_mode == edge_mode (continuing with the same travel mode), the code returned n_legs = 0, making the constraint check always pass regardless of actual trip leg count. This allowed infinite expansion within a single mode once any mode transition exceeded the limit.

Changes

  • constraint.rs line 92: Changed _ => 0 to _ => n_existing_legs to properly validate same-mode continuations
  • model.rs: Added test_max_trip_legs_same_mode_continuation_at_limit to verify same-mode edges are rejected when over the limit

The constraint now correctly bounds search expansion for both mode transitions and same-mode continuations.

Original prompt

This section details on the original issue you should resolve

<issue_title>bugs during test of template TOML file</issue_title>
<issue_description>while attempting a test run from a bambam-omf import using a new template configuration TOML file as part of #96, we can get as far as running search. however, the app is killed by the system during search, without returning a single successful search result:

queries assigned per executor: [230, 230, 230, 230, 230, 230, 230, 229]
zsh: killed     RUST_LOG=info ../rust/target/release/bambam -c denver/bambam-config-omf.toml

this is likely a search running without bounds. some possible issues:

  • thrashing in the frontier space due to repeated labels
  • solution size is not sufficient for a termination condition with label setting
  • we should be able to run bambam with query-time assignment of available_modes, but, it seems it is only set at config time (see rust/bambam/src/model/frontier/multimodal/service.rs for the build() method implementation)</issue_description>

<agent_instructions>task: identify what could be causing an infinite loop or overflow of resources</agent_instructions>

Comments on the Issue (you are @copilot in this section)

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Copilot AI and others added 3 commits February 3, 2026 23:21
@robfitzgerald
Fix MaxTripLegs constraint bug causing infinite search expansion
3eaad85 
Co-authored-by: robfitzgerald <7003022+robfitzgerald@users.noreply.github.com>
@robfitzgerald
Remove accidentally committed backup file
a015ab0 
Co-authored-by: robfitzgerald <7003022+robfitzgerald@users.noreply.github.com>
@robfitzgerald
Clarify test comments to distinguish buffer size from constraint limit
63f708e 
Co-authored-by: robfitzgerald <7003022+robfitzgerald@users.noreply.github.com>
Copilot AI changed the title [WIP] Fix bugs during test of template TOML file Fix MaxTripLegs constraint allowing infinite same-mode expansion Feb 3, 2026
Copilot AI requested a review from robfitzgerald February 3, 2026 23:28
@robfitzgerald robfitzgerald changed the base branch from main to rjf/omf-config-and-metadata February 3, 2026 23:47
@robfitzgerald robfitzgerald marked this pull request as ready for review February 3, 2026 23:48
@robfitzgerald robfitzgerald merged commit 0a326fb into rjf/omf-config-and-metadata Feb 3, 2026
1 check failed
@robfitzgerald robfitzgerald deleted the copilot/fix-template-toml-search-bug branch February 3, 2026 23:59
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bugs during test of template TOML file

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