Architecture — Remove the Legacy Agent Classifier Backfill

Single source of truth for this change. removal-plan.md and removal-testing.md reuse the identifiers, file paths, and rules defined here verbatim.

Naming note: this repository already contains unrelated design docs named architecture.md and testing.md (the "Agent Worker" feature). This change set deliberately uses the removal- prefix so it does not clobber them.

1. Overview

Two review comments on the open PR define the entire scope:

Fix the following failing test: AgentSpanDeploymentContractEndToEndTest > legacyAgentClassifierBackfillUsesConcreteExecutionTimeBounds() java.lang.NoSuchMethodException: ...AgentService.backfillLegacyAgentExecutionClassifiers()
do not add back backfillLegacyAgentExecutionClassifiers method. This method should not be added back.

Both comments resolve to a single decision:

The backfillLegacyAgentExecutionClassifiers method and everything that exists only to serve it are removed from production code. The test that reflectively invoked the method is removed with it. The method is NOT re-added.

The test failed because it reaches for the method by reflection (getDeclaredMethod("backfillLegacyAgentExecutionClassifiers")). Comment 1 asks for the failure to stop; comment 2 forbids the obvious "add the method back" fix. The only resolution satisfying both is to delete the method and delete the test that depends on it. This reverses the prior commit code_subtask add-backfill-method.

Non-goals

No new production behavior, no replacement backfill, no migration utility.
No refactoring of unrelated AgentService members.
No changes to any module other than the two files in section 3.

2. Tech stack (as relevant to this change)

Language / build: Java 21, Gradle. Format with ./gradlew spotlessApply.
Production module: agentspan.
Test module: test-harness (integration tests).
Lombok: AgentService uses @RequiredArgsConstructor, so the constructor is derived from its private final fields. Removing a private final field removes it from the constructor automatically — no constructor edit needed.

3. Complete file layout

This change edits exactly two existing source files and creates no source files.

File	Module	Action
`agentspan/src/main/java/org/conductoross/conductor/ai/agentspan/runtime/service/AgentService.java`	`agentspan`	Delete the backfill method, its two private helpers, its two constants, and the one field + import that becomes dead as a result.
`test-harness/src/test/java/com/netflix/conductor/test/integration/agent/AgentSpanDeploymentContractEndToEndTest.java`	`test-harness`	Delete the `legacyAgentClassifierBackfillUsesConcreteExecutionTimeBounds` test method and its now-unused `java.lang.reflect.Method` import.

Design docs (this set), under docs/design/:

Doc	Responsibility
`removal-architecture.md`	This file. Source of truth: decision, identifiers, dead-code rules.
`removal-plan.md`	File-by-file, line-anchored edit plan derived from this doc.
`removal-testing.md`	What the test change is and how to verify it compiles and passes.

4. Shared contracts

4a. Identifiers to remove

All identifiers below live in AgentService.java, copied verbatim from the current source. Line numbers are current positions (anchors, not guarantees).

Kind	Identifier / signature	Current line
Method	`private void backfillLegacyAgentExecutionClassifiers()`	420
Helper	`private static int backfillVersionOf(Map<String, Object> metadata)`	463
Helper	`private void reindexAgentExecutions(String agentName)`	476
Constant	`private static final String AGENT_CLASSIFIER_BACKFILL_VERSION = "agent_classifier_backfill_version";`	64
Constant	`private static final int AGENT_CLASSIFIER_BACKFILL_VERSION_VALUE = 2;`	68
Field	`private final IndexDAO indexDAO;`	75
Import	the `IndexDAO` import backing the field above	imports block

Remove the Javadoc/comment blocks attached to each of the above (the method Javadoc at 407–419, the reindexAgentExecutions Javadoc at 471–475, and the two comment lines above the AGENT_CLASSIFIER_BACKFILL_VERSION_VALUE constant).

In the test file:

Kind	Identifier / signature	Current line
Test method	`void legacyAgentClassifierBackfillUsesConcreteExecutionTimeBounds()` (incl. `@Test`)	295–338
Import	`import java.lang.reflect.Method;`	18

4b. Identifiers that MUST stay (do not delete)

This is the critical correctness constraint and the correction over any earlier plan. Each identifier below is referenced by code outside the removed backfill block, verified by repository-wide grep against the current source. Removing any of them breaks compilation.

Identifier	Still used at (outside the backfill block)
`WorkflowClassifiers` import + `WorkflowClassifiers.isAgent(...)`	`AgentService.java:316`, `:366`
`SearchResult` import	`:600`, `:728`, `:973`, `:1548`, `:1553`, `:1555`
`WorkflowSummary` import	`:600`, `:728`, `:973`, `:976`, plus search methods
`WorkflowModel` import	`:765`, `:780`
`executionDAO` field (`ExecutionDAO`)	`:765`, `:767`, `:780`, `:782`
`workflowService` field (`WorkflowService`)	throughout the class

Any plan that proposes removing WorkflowClassifiers, SearchResult, WorkflowSummary, WorkflowModel, or executionDAO is wrong for the current source. They are live.

4c. The dead-code rule (governs every deletion)

Remove a helper, constant, field, or import only when its last remaining reference is one of the members already scheduled for deletion in 4a. Confirm each "last reference" with a repository-wide search immediately before deleting.

Grep against the current source establishes exactly one field — indexDAO — as newly dead:

indexDAO is referenced only inside reindexAgentExecutions (AgentService.java:513, indexDAO.indexWorkflow(...)). Once that helper is gone, the field and its IndexDAO import are orphaned and are removed.

If a future grep contradicts these findings, the dead-code rule wins over the tables above: keep anything with a surviving reference; delete only what is truly orphaned.

4d. Naming convention

No new names are introduced. This change is subtractive only.

5. Correctness argument

Comment 1 (failing test) is satisfied: the test is deleted, so its NoSuchMethodException can no longer occur.
Comment 2 (do not re-add the method) is satisfied: the method is removed and stays removed; nothing re-introduces it.
Compilation is preserved because 4b enumerates every reference that survives, and 4c removes only genuinely orphaned members (indexDAO + its import).

6. Change budget

Two source files edited, zero source files created, zero production behaviors added. This is the minimal set that satisfies both review comments at once.