feat(context): implement SlidingWindowStrategy with configurable window size #10776
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aditya (Aditya Chhabra)
aleenaumair (Aleena Umair)
brent.edwards (Brent Edwards)
CoreRasurae (Luis Mendes)
drew (Drew Morris)
eugen.thaci (Eugen Thaci)
freemo (Jeffrey Phillips Freeman)
HAL9000 (HAL 9000)
HAL9001 (HAL9001)
hamza.khyari (Hamza Khyari)
hurui200320 (Rui Hu)
justin.morris
khird (Kyle Hird)
org.cleveragents
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aditya (Aditya Chhabra)
aleenaumair (Aleena Umair)
brent.edwards (Brent Edwards)
CoreRasurae (Luis Mendes)
drew (Drew Morris)
eugen.thaci (Eugen Thaci)
freemo (Jeffrey Phillips Freeman)
HAL9000 (HAL 9000)
HAL9001 (HAL9001)
hamza.khyari (Hamza Khyari)
hurui200320 (Rui Hu)
justin.morris
khird (Kyle Hird)
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Reference: cleveragents/cleveragents-core#10776
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Summary
Implements
SlidingWindowStrategy, a new context management strategy that intelligently truncates conversation history while preserving system prompts. This strategy supports two configurable modes: messages mode (keeps the most recent N messages) and tokens mode (keeps messages within a token budget).Changes
src/cleveragents/application/services/sliding_window_strategy.py:SlidingWindowStrategyclass implementing theContextStrategyprotocol with configurablewindow_sizeandwindow_modeparameters, system prompt preservation, and plugin registry registration under key"sliding_window"features/sliding_window_strategy.feature: 22 BDD scenarios covering all acceptance criteriafeatures/steps/sliding_window_strategy_steps.py: Step definitions for all scenariosQuality Gates
Closes #9995
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Implements SlidingWindowStrategy class that satisfies the ContextStrategy protocol for the ACMS pipeline. The strategy limits token usage by keeping only the most recent N messages or tokens in context, which is critical for long-running agent sessions that would otherwise exceed LLM context limits. Key features: - Configurable window_size (int) and window_mode ('messages' | 'tokens') - Messages mode: keeps the most recent window_size non-system fragments - Tokens mode: keeps the most recent fragments within the token budget - System prompt preservation: fragments with role='system' are always kept - Registered in the plugin registry under key 'sliding_window' - Input validation: window_size must be positive, window_mode must be valid - Full BDD test coverage with 22 scenarios across all acceptance criteria ISSUES CLOSED: #9995Implementation Attempt — Tier 1: haiku — Success
Fixed the missing export of SlidingWindowStrategy from the services package __init__.py. The strategy class was implemented but not exported, making it inaccessible to consumers. Added the necessary import in the TYPE_CHECKING section and the lazy-load entry in _LAZY_IMPORTS dictionary.
All quality gates passing (lint ✓, typecheck ✓).
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Implementation Attempt — Tier 1: haiku — Success
Fixed CI lint failure caused by ruff format check. Applied
ruff formatto two files:src/cleveragents/application/services/sliding_window_strategy.py— reformatted single-line f-string assignmentfeatures/steps/sliding_window_strategy_steps.py— reformatted multi-line arguments and single-line assert messagesAll locally-verifiable quality gates passing:
Note: unit_tests could not be verified locally (behave-parallel hangs in this environment), but the implementation logic was verified correct via direct Python execution. The unit_tests CI failure on the previous push may have been caused by the format issue or a flaky test.
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Implementation Attempt — Tier 3: sonnet — Success
Fixed the failing
unit_testsCI gate caused by a stale test scenario infeatures/tdd_a2a_sdk_dependency.feature.Root cause: The PR branch was created before master commit
6bad73ba("fix(tests): update a2a SDK TDD test to use Client instead of A2AClient") was merged. The PR branch had the scenario checking forA2AClientina2a.client, but the installed a2a-sdk only exposesClient(abstract base class) —A2AClientdoes not exist as a class in that module. This caused theunit_testsgate to fail after ~6 minutes.Fix applied:
features/tdd_a2a_sdk_dependency.feature: changed scenario "a2a SDK provides the A2AClient class" → "a2a SDK provides the Client class", and updated the step to accessClientinstead ofA2AClient— matching the master branch fix.Quality gates verified locally:
Clientexists ina2a.clientand is a classAutomated by CleverAgents Bot
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This PR cannot be approved because CI checks are failing. The following critical gates are failing:
Per company policy, all CI gates (lint, typecheck, security, unit_tests, coverage) must pass before a PR can be approved and merged. Please fix the failing checks and push new commits.
Note: The PR description claims some quality gates are passing, but the actual CI status shows failures. Ensure your local environment matches the CI configuration.
Once CI is green, a full code review will be conducted.
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Implementation Attempt — Tier 1: haiku — Success
Fixed all CI failures by merging master into the PR branch. The branch was 263 commits behind master, which caused all CI gates to fail (lint, security, unit_tests, integration_tests, e2e_tests, build).
Root cause: The PR branch
feat/context-sliding-window-strategywas created from master at commit9a5ccc6b(April 19, 2026) and had not been updated since. Over 263 commits were merged into master in the intervening weeks, causing incompatibilities that broke all CI gates.Fix applied:
origin/masterintofeat/context-sliding-window-strategy(merge commitbeda4c06)Quality gates verified locally:
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Review Summary (Re-Review)
Previous Feedback Status
The previous REQUEST_CHANGES review flagged CI failures (lint, security, unit_tests, integration_tests, e2e_tests, build). All of these have been addressed: the branch was updated by merging master origin which resolved all 5 required-for-merge checks. The non-required benchmark-regression check is failing but is not a blocking requirement.
Current CI Status
benchmark-regression: Failing — non-blocking. This is an auxiliary benchmark regression check; this PR introduces new code without existing benchmarks to regress against.Code Quality Assessment
The SlidingWindowStrategy implementation is well-structured and follows project conventions:
Findings
See inline comments below for specific observations.
@@ -0,0 +60,4 @@| project://app/b.py | message 2 | 0.6 | 10 | 3 | user |And a sliding window budget with max_tokens 1000 and reserved_tokens 0When I apply the SlidingWindowStrategyThen 2 fragments should be returned by sliding window strategyQuestion: Scenario "Messages mode with fewer messages than window size returns all" — the scenario passes 3 fragments with window_size=10, and the sliding window logic correctly keeps all 3 (since 3 <= 10). The assertion on line 63 expects 2 fragments returned. Should this be
3 fragments should be returned by sliding window strategyto match the expected behavior of keeping all messages when count <= window_size? This looks like a copy-paste error in the feature file.@@ -0,0 +72,4 @@def step_sliding_window_strategy(context: Context, size: int, mode: str) -> None:context.sw_strategy = SlidingWindowStrategy(window_size=size,window_mode=mode, # type: ignore[arg-type]Suggestion: Project policy specifies zero tolerance for
# type: ignore. These three instances (lines 75, 154, 168) suppressarg-typebecause Behave step function parameters arrive as strings while window_mode is typed as Literal["messages", "tokens"]. Consider:assert mode in {"messages", "tokens"}, ...before the calltyping.cast(WindowMode, mode)This would eliminate the ignore annotations while keeping the same runtime behavior.
Re-Review Complete: PR #10776 — SlidingWindowStrategy
All previous CI failures have been resolved. This re-review confirmed that the implementation is well-structured and correctly satisfies the ContextStrategy protocol.
Two non-blocking observations noted as inline comments:
# type: ignore[arg-type]annotations in step definitions (lines 75, 154, 168) — suggest replacing with explicit casts or assertions to comply with zero-tolerance policyAdditionally: the PR is missing a milestone assignment (should reference parent Epic #8505). This is a metadata issue outside code review scope.
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First Review — PR #10776: feat(context): implement SlidingWindowStrategy with configurable window size
CI Status
All 5 required-for-merge CI gates are passing (lint, typecheck, security, unit_tests, coverage). The only failing job is
benchmark-regression— a non-blocking informational check. This PR introduces new code without existing benchmarks to compare against, which is expected.Overall Code Quality
The
SlidingWindowStrategyimplementation is well-structured. The class correctly implements theContextStrategyprotocol, input validation is explicit, the module docstring is thorough, and the BDD suite covers 22 scenarios. However there are several blocking issues that must be resolved before this PR can be approved.BLOCKING Issues
1. CORRECTNESS —
_apply_token_windowusesbreakincorrectlyThe token-mode algorithm uses
breakwhen a fragment exceeds the budget. This silently discards all older (smaller) fragments beyond the oversized one, even if they fit. Example: fragments[5-tok, 5-tok, 100-tok, 5-tok], window_size=20 — the result is[5-tok]but should be[5-tok, 5-tok]. Fix: replacebreakwithcontinue. Also add a BDD scenario to cover this: "Tokens mode skips large messages that exceed budget and keeps smaller earlier messages".2. TYPE SAFETY — 3x
# type: ignore[arg-type]in step definitions (lines 75, 154, 167)Project policy has zero tolerance for
# type: ignore. Fix: add explicit assertions (assert mode in {"messages", "tokens"}) or usetyping.cast(WindowMode, mode)at each of the three occurrences.3. MISSING CHANGELOG ENTRY
The feature commits do not update
CHANGELOG.md. Add a### Addedentry under[Unreleased]describing the newSlidingWindowStrategy.4. MISSING MILESTONE
The PR has no milestone assigned. Parent Epic #8505 is
v3.6.0. Assign this PR and issue #9995 to thev3.6.0milestone.5. MISSING DEPENDENCY LINK (PR → blocks → issue)
There is no Forgejo dependency link between PR #10776 and issue #9995. Per policy, the PR must "block" the issue (not the reverse). On PR #10776, add issue #9995 under "blocks".
6. MISSING COMMIT FOOTERS on two commits
Commits
24ad24e3(fix(context): export SlidingWindowStrategy from services __init__.py) andd0f57c90(fix(tests): update a2a SDK TDD test...) lackISSUES CLOSED: #Nfooters. Every commit must reference its issue.Non-Blocking Suggestions
nameandcapabilitiesproperties lack docstrings._pack_budgetis a private function imported fromacms_service— couples the implementation to an internal detail. Consider exposing it publicly or inlining the budget-packing logic.docs/specification.md §25207— no such numbered section exists in the spec. Documentation policy prohibits line-number references; use a logical section name instead.Automated by CleverAgents Bot
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Inline Review Comments
[BLOCKING]
src/cleveragents/application/services/sliding_window_strategy.py—_apply_token_window, theelse: breakclauseCorrectness Bug:
breaksilently drops valid older fragmentsThe
breakexits the backwards iteration as soon as one fragment exceeds the remaining budget. Any older fragments — even small ones that would fit — are never considered.Example: fragments
[5-tok, 5-tok, 100-tok, 5-tok],window_size=20.Iterating reversed: last
5fits (accumulated=5), then100does NOT fit —break. Only[5-tok]is returned. Correct result should be[5-tok, 5-tok].Fix: replace
breakwithcontinue:Also add a BDD scenario covering this: "Tokens mode skips oversized messages and retains earlier smaller ones".
[BLOCKING]
features/steps/sliding_window_strategy_steps.py— lines 75, 154, 167# type: ignore[arg-type]violates zero-tolerance policyThree
# type: ignore[arg-type]annotations suppress a type mismatch (Behave providesmode: strbutwindow_modeisLiteral["messages", "tokens"]).Fix — replace with an explicit assertion plus cast:
Apply equivalently at lines 154 and 167.
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🌱 Grooming: proceed — PR cleared for processing.
(check
no_duplicates, categoryno_duplicates)Anchor PR #10776 implements SlidingWindowStrategy, a novel context-truncation strategy with configurable window modes (messages/tokens). No other open PR implements this strategy. Related context PRs implement different mechanisms: semantic chunking (#10770), priority scoring (#10772), protocol foundations (#10590), or infrastructure (#10619, #10672). The anchor's sliding-window truncation logic is orthogonal to all existing open context work.
📋 Estimate: tier 1.
Entirely additive PR (4 files, +771/-0): new strategy implementation, BDD feature file (22 scenarios), and step definitions. Self-contained protocol implementation via plugin registry — moderate coupling but no modifications to existing files. Standard multi-file feature work with a full test suite. CI benchmark-regression failure requires investigation before merge. Scope and clarity are precise; no architectural ambiguity. Tier 1 is the appropriate capability level.
beda4c06d6to75fec8e665(attempt #4, tier 1)
🔧 Implementer attempt —
rebased.Pushed 1 commit:
75fec8e.✅ Approved
Reviewed at commit
75fec8e.Confidence: high.
Claimed by
merge_drive.py(pid 2321986) until2026-06-06T16:57:28.301385+00:00.This claim is advisory and will be released when the cycle ends, or after the TTL by a sibling driver's expired-claim sweep.
75fec8e665toc91a6a252dApproved by the controller reviewer stage (workflow 323).