## What changed
- Add the under-development `mcp_oauth_refresh_coordination` feature and pin its selected refresh mode to each MCP connection.
- Treat the refresh mode as part of OAuth connection identity so runtime and MCP configuration refreshes reconnect when the mode changes.
- Keep legacy refresh behavior in builds where coordination is unavailable and emit a warning when coordinated mode is selected.
## Testing
- Cover connection replacement when the feature is toggled through both runtime and MCP configuration refresh paths.
GitOrigin-RevId: 89596150f0338e6ede0e712badecea4450831766
## What changed
- Make `local_thread_store_compression` compress cold rollout files across shared and forked histories without a separate compression mode.
- Retire `local_thread_store_shared_compression` while continuing to accept it in strict configuration without changing compression behavior.
- Read rollout files through the compressed-rollout reader when `codex exec resume` determines the latest turn's working directory.
## Testing
- Cover compression and restoration of an archived fork chain.
- Cover cwd-based resume selection when only the compressed rollout remains.
- Cover the removed compatibility key in strict configuration.
GitOrigin-RevId: 8edebf61eccc1f79cabb8e641f8982c76f337bf1
## What changed
- Add the disabled-by-default `omit_app_server_notification_media` feature.
- When enabled, remove inline image and audio content from `item/started`,
`item/completed`, and `rawResponseItem/completed` notifications, including
tool output and image-generation results.
- Keep the media in model input; the filter only changes app-server
notifications.
## Testing
- Verify that image content is absent from all three notification types while
the model request still receives it.
GitOrigin-RevId: 9a4434d18a3dac6d67c2e0c3723ff4595a9b3797
## Why
Fetching plugin recommendations while building the first-turn context delays that
context when the recommendation catalog is not already cached.
## What changed
- Start fetching recommendations during session initialization, in parallel with
MCP and plugin setup, and reuse the in-flight request when building context.
- Centralize the feature checks that enable plugin recommendations.
- Prevent an invalidated recommendation request from repopulating the cache after
a newer request has completed.
## Testing
Added coverage for startup feature gating, reuse of the in-flight fetch, legacy
behavior when recommendations are unavailable, and cache invalidation races.
GitOrigin-RevId: 708774b9bfc472c9847973ae8b2774b66e7321e4
## Why
Rollout compression skips files that participate in paginated fork lineages because lineage readers rely on byte offsets into the original JSONL. This prevents shared rollout history from being compressed.
## What changed
- Add a seekable rollout reader that preserves logical JSONL offsets for plain and zstd-compressed files without materializing compressed data beside the rollout.
- Use the reader for lineage validation, model-context replay, and SQLite history projection, including when compression races with a read.
- Add the opt-in `local_thread_store_shared_compression` feature. The default mode continues to leave shared lineages uncompressed for compatibility, while the new mode includes referenced sources and fork pointers.
- Record the uncompressed size in new zstd frames so common prefix-bound checks can avoid decoding the full file.
## Testing
Add coverage for seekable compressed reads, prefix validation across zstd frame shapes, compressed lineage replay and projection, concurrent forks, and compression-mode behavior.
GitOrigin-RevId: 83e519f7eabf7448977eff37c55899858cc17a07
## What changed
- Add a stable `sleep_tool` feature that can enable or disable registration of the built-in sleep tool independently of the clock tool.
- Support structured `features.sleep_tool` configuration with `model_driven` and `always_on` modes. The default `model_driven` mode preserves the existing model and `current_time_reminder` behavior, while `always_on` registers sleep whenever the feature is enabled.
- Preserve nested sleep-tool configuration across CLI overrides, config merges, and feature toggles, and expose the settings in the generated config schema.
## Testing
- Cover feature-map overrides, both selection modes, legacy clock settings, config merging and editing, and invalid mode rejection.
GitOrigin-RevId: 18eadc582f8a4445958c29d063e5be495276703e
## What changed
- Add the under-development `powershell_shell_version` feature flag.
- When enabled for a single local PowerShell environment, query the selected
shell executable and include its major/minor version in
`<environment_context>`.
- Cache version lookups, bound command execution and output, and report when a
previously visible version becomes unavailable.
## Testing
- Cover environment-context diffs when the shell version appears or disappears.
- Verify on Windows that the version is model-visible only when the feature is
enabled.
GitOrigin-RevId: 3ec8e80425ec3c193134dc1b69f61ef09ede375e
## What changed
- Promote `compaction_image_budget` to stable and enable it by default.
- Charge retained images against the remote compaction context budget unless the feature is explicitly disabled, trimming older images as needed.
## Testing
- Update remote compaction coverage for the default, explicitly enabled, and explicitly disabled behavior.
GitOrigin-RevId: 0f715347cefc33b814bdcfd9b430ef453d3bd6df
## What changed
- Add the `write_stdin_approval` feature flag, disabled by default, to require a fresh approval before sending non-empty input to an escalated unified-exec terminal.
- Route these reviews through hooks, Guardian, app-server, and the TUI as `writeStdin` approvals while keeping the parent command item unchanged.
- Preserve the terminal environment, launch directory, and escalation state across turns, and revalidate the process identity after approval before writing input.
## Testing
- Cover approval routing, policy decisions, process reuse, terminal identity preservation, app-server events, analytics, and TUI rendering.
GitOrigin-RevId: 4ba29eaae6208e934737ba078c96e589c7c2164d
## What changed
- Add the `features.guardianv2.persist_scores` configuration option for debugging.
- Default the option to `false`, so Guardian V2 reviewed actions and risk scores are only written to rollout files when explicitly enabled and the session is not ephemeral.
## Testing
- Cover configuration deserialization, default non-persistence, and opt-in persistence for nested code-mode actions.
GitOrigin-RevId: 452af99ef14553d45140340ececc2913389124d0
## What changed
- Add the opt-in `features.guardianv2.free_guardian` setting to route eligible
Guardian reviews to `/guardian` and asynchronous classifications to
`/guardian-classifier`.
- Support endpoint selection for both HTTP and WebSocket Responses clients,
including endpoint-aware connection reuse.
- Keep `/responses` for API-key authentication, custom provider URLs,
non-Guardian models, and configurations where the option is disabled.
- Omit routing hints and `service_tier` from requests sent to the dedicated
Guardian endpoints.
## Testing
- Cover route selection across authentication modes, provider URLs, HTTP
fallback, WebSocket review sessions, and classifier sampling.
GitOrigin-RevId: 9c88673c710d009e0239559b9245a4e6c4f4befc
## What changed
- Add a feature-gated Amazon Bedrock option to eligible TUI sign-in flows.
- Discover existing AWS profiles and environment credentials, with manual setup for profiles, access keys, environment variables, and Bedrock API keys.
- Collect the AWS Region, mask secrets during entry, persist the selected Bedrock configuration through the app server, and restart the embedded server when the provider changes.
## Testing
- Cover wizard eligibility, sign-in option rendering, credential discovery ordering, region entry, and secret masking.
GitOrigin-RevId: 0a49afb6aca442b88e8448efa80336777848f4ac
## What changed
- Add the opt-in `code_mode_prewarm` feature to establish the code-mode host session during startup, before the first turn.
- Make in-progress host initialization cancellable so a stalled prewarm does not block shutdown.
- Share a failed connection attempt with concurrent callers instead of immediately starting another attempt.
## Testing
- Verify app-server contacts the configured host before the first turn and can shut down while that connection is stalled.
- Exercise shared remote-host behavior with prewarming enabled.
GitOrigin-RevId: 3cfde5509be7b4aba80112c36c5616b9a9b632c6
## What changed
Mark `content_item_kinds` as stable and enable it by default. Remove the
test harness override that previously enabled the feature explicitly.
GitOrigin-RevId: 86b0c3f295c4de3b8900981bfdd8830f275073f5
## What changed
- Add a feature-gated `TurnSettings` operation that can update the model,
reasoning effort, reasoning summary, and service tier for subsequent steps of
a named running turn without changing future thread settings.
- Report whether an update was applied, rejected, or lost its live target.
- Revalidate managed constraints and preserve the turn's admitted approval and
Guardian safety properties before publishing an updated settings snapshot.
## Testing
- Cover sparse updates, step capture and ordering, target replacement, managed
policy changes, model metadata safety, and separation from future settings.
GitOrigin-RevId: ecaaaa95b4fd4ec9d62265bef551582dddb36d78
## What changed
- Add the under-development `skip_host_skill_discovery` feature to bypass host
skill snapshots during session warmup and turn setup.
- Let skill invocation contributors declare whether they require host-owned
skills. Preserve host discovery when no contributors are registered or any
contributor requires it.
- Keep executor and orchestrator skill catalogs and instruction loading
available when host discovery is skipped.
## Testing
- Cover executor-only, orchestrator, mixed-contributor, and legacy host-skill
behavior.
GitOrigin-RevId: 48169403090b234e1a304c6523633fd867df454a
## What changed
- Add the under-development `transcript_v2` feature for the interactive
transcript composer and turn-selection UI.
- Keep it disabled by default and expose it through the configuration schema
and `codex features enable transcript_v2`.
## Testing
- Verify explicit configuration overrides and CLI persistence for the new
feature.
GitOrigin-RevId: 138ab7851621c066e8121cc3eb6cd4e7299f9c31
## What changed
- Add `features.guardianv2.review_scope.computer_use_only` to restrict asynchronous classification and fast approvals to browser and computer-use REPL tools.
- Keep other tools on the synchronous approval path without letting them age or reuse scores from in-scope calls.
- Give this scope precedence over `sandboxed_exec_commands` when both options are enabled.
## Testing
- Cover configuration precedence, direct and code-mode tool detection, fast-approval isolation, and end-to-end approval routing for browser, computer-use, and unrelated MCP servers.
GitOrigin-RevId: bfd9ab6abdbd90634b265d354e038724b1e81d65
## What changed
- Add `features.network_proxy.credential_broker` and preserve structured network proxy settings when toggling the feature through config APIs.
- Protect broker enablement and provider context variables from project config, while carrying trusted context into filtered shell environments.
- Propagate brokered credentials through shell snapshots and restore real credentials for unsandboxed escalated commands.
- Normalize broker context environment keys case-insensitively on Windows and avoid conflicting remote managed-network enforcement when no proxy launch configuration is available.
## Testing
- Cover config layering, editing, project sanitization, Windows environment handling, shell snapshots, escalated execution, and end-to-end GitHub credential brokering in the zsh-fork runtime.
GitOrigin-RevId: 500e51e804e1988022052ccfe00b8fac5e495f4f
## What changed
- Add the under-development `content_item_kinds` feature, disabled by default.
- Strip content item classifications from Responses input when the feature is
disabled while preserving other passthrough metadata.
## Testing
- Add coverage that disables the feature and verifies requests omit content item
kinds without removing the turn ID.
GitOrigin-RevId: f938feb2895d766d979b1666fc7b97fd128fe8a7
## What changed
- Register the stable, requirements-only `in_app_local_automation` feature for desktop apps.
- Add the feature to the configuration schema.
- Verify that an enterprise requirement can disable local automation.
GitOrigin-RevId: 939f7f3ee15f662dc85589cd1bcc3838e4cd1287
## Why
Remote compaction's retained-message budget counted text but not images, so
image-heavy history could retain more context than the budget represented.
## What changed
- Add the opt-in `compaction_image_budget` feature to charge retained images
using the existing image size estimate.
- Keep images and their adjacent labels atomic when truncating a boundary
message, while preserving existing text, audio, metadata, and
client-authored developer-message behavior.
- Stop backfilling older messages when an image at the truncation boundary
does not fit.
## Testing
- Add unit coverage for image boundaries, annotations, audio, text-only
messages, and client-authored developer messages.
- Add an integration test covering repeated remote compaction with the feature
enabled, disabled, and left at its default.
GitOrigin-RevId: 88868bbd09d2858939dbae3f8402e1f497b4e3c6
## What changed
- Recognize `cua_repl` alongside `node_repl` when collecting Guardian review evidence, applying computer-use policy, and capturing transcript images.
- Render `cua_repl.js` results with the compact REPL history and transcript views.
- Preserve failed MCP call status and result content when replaying app-server history.
## Testing
- Cover both REPL server names across Guardian policy, evidence, image capture, history rendering, and failed-call replay tests.
GitOrigin-RevId: 8c13a721f718add403b07e727c1634b59203c51a
## What changed
- Add an extension API for spawning host-owned internal sessions and a
`ThreadReadyInput` lifecycle callback that runs after thread registration.
- Add Guardian reviewer session scaffolding that records the parent thread and
effective model, plus the under-development `guardian_ext` feature flag.
- Start internal sessions with fresh history while preserving parent lineage,
shared session controls, and internal-thread visibility rules.
- Scope internal-session prompt cache keys to their source and parent thread,
and expose `guardian` as an internal session source.
## Testing
- Cover internal-session spawning, parent metadata, history isolation, prompt
cache keys, and extension spawner argument forwarding.
GitOrigin-RevId: 682dae80397d62bb36247796b447042e760ca364
## What changed
- Add the under-development `shell_snapshot_v2` feature and advertise executor support through environment capabilities.
- Use executor-managed, in-memory snapshots for eligible direct `bash`, `zsh`, and `sh` login commands, while applying the configured shell environment policy and avoiding duplicate automatic startup-file effects.
- Keep file-backed snapshots available for user-shell commands and fall back to the existing execution path when in-memory snapshots are unsupported or inapplicable.
## Testing
- Cover policy filtering, snapshot reuse without snapshot files, automatic startup files, local and remote execution, and legacy user-shell snapshots.
GitOrigin-RevId: 4ad6cdf13824913ac8c393ba38b9844230677579
## What changed
Rename the token-budget configuration key and its Rust field from
`use_history_notes_history` to `use_history_notes_extension`. Update the config
schema, extension gating, explicit-setting detection, and tests to use the new
name consistently.
GitOrigin-RevId: b6a514e23f02095fcd1d35dc42eeb7394b800c77
## Why
Token-budget sessions need a way to recover prior conversation context and preserve working state across context-window transitions.
## What changed
- Add direct-model `history` tools for listing windows and items, reading items, and searching conversation contents.
- Add direct-model `notes` tools for listing, reading, searching, appending, and writing persistent notes.
- Route tool calls through the configured Codex backend with trusted session and agent context, bounded request arguments, and truncation-aware output handling.
- Expose the extension when `features.token_budget.use_history_notes_history` is enabled with an OpenAI provider and Codex backend authentication.
## Testing
- Cover tool registration, configuration changes, provider and authentication requirements, backend request context, encrypted output preservation, and request and response limits.
GitOrigin-RevId: 43b259f01014ba3f30803dd7cd5634942407a9bb
## What changed
- Remove the legacy `shell_command` handler and runtime, leaving `exec_command`
and `write_stdin` as the shell execution tools.
- Treat legacy `shell_command` model metadata as `unified_exec`, and normalize
legacy user opt-outs so they do not disable command execution. Managed feature
requirements and `shell_tool` can still disable it.
- Preserve shell approvals, sandboxing, zsh-fork support, and output truncation
through the unified execution path.
## Testing
- Cover legacy configuration and model-metadata compatibility.
- Exercise unified shell execution, approvals, truncation, and `apply_patch`
serialization across the app-server and core test suites.
GitOrigin-RevId: 5c2fd6164fc3519cdae4944cb9db276b8467311c
## What changed
- Exclude sandboxed `exec_command` and `shell_command` calls from Guardian v2 classification by default while continuing to classify calls that request `require_escalated` permissions.
- Add `guardianv2.review_scope.sandboxed_exec_commands` to opt sandboxed shell commands back into classification.
- Keep other tools and namespaced shell tools in scope, and advance tool-call progress when a call is skipped.
## Testing
- Cover the default and configured review scopes, tool namespaces, permission modes, and skipped-call progress tracking.
GitOrigin-RevId: 32fb540c69959b9a82569f0f2fc76b5517496e6b
## What changed
- Add the opt-in `cwd_relative_turn_diffs` feature.
- When enabled, render turn diff paths relative to each selected environment's
working directory instead of the detected Git root.
- Preserve repository-root-relative paths when the feature is disabled.
## Testing
- Cover enabled and disabled behavior for nested working directories across
supported originators.
GitOrigin-RevId: 8b4908706a82b01f33ccd035b0945f9a29fce26f
## What changed
- Expose `send_user_message_async` to root agents whenever the selected model advertises support for it.
- Retain `send_async_message` as a removed compatibility flag so existing configuration is accepted without controlling tool availability.
- Update the async message test to cover model-driven tool exposure without enabling the legacy flag.
GitOrigin-RevId: 558b427c2b203a057dd7c836e0ec702ae6134346
## What changed
- Add the under-development `send_async_message` feature, disabled by default.
- Expose the feature key in the generated configuration schema.
GitOrigin-RevId: dd27483f2ef802dba49e47f3ce03146ee6a58f1e
## What changed
- Register `in_app_chat` and `in_app_dictation` as stable, default-enabled feature gates for desktop apps.
- Allow requirements to disable either capability and expose both keys in the generated configuration schema.
## Testing
- Add configuration tests that verify enterprise requirements can disable each gate.
GitOrigin-RevId: 5bba35d710fb0b6924aa55df98b2e013fa288f6d
## What changed
- Track the latest tool call and latest scored tool call for each Guardian v2 thread.
- Skip approval review when the score lags by more than `max_tool_call_lag` tool calls.
- Add `max_tool_call_lag` to the Guardian v2 configuration and schema, with a default of three.
## Testing
- Cover approval review at, above, and after recovering from the configured lag limit.
- Cover deserialization of `max_tool_call_lag`.
GitOrigin-RevId: fd870e143d95ee76491180e2aed742717248ff78
## What changed
- Add the `features.guardianv2.transcript.include_images` opt-in setting.
- Include recent images from user and assistant messages and configured tool outputs in Guardian v2 sampling requests.
- Bound image context to the four most recent images and 8 MiB total, and omit image detail hints when constructing the sampling request.
## Testing
- Cover configuration parsing and image forwarding from messages and tool outputs.
GitOrigin-RevId: b0ae6b6182535fd084ea103ed01dc3c803d7d1f7
## What changed
- Add `max_parent_compaction_tokens`, defaulting to 25,000 tokens, to the Guardian v2 feature configuration.
- Reuse the latest encrypted parent compaction only when its complete serialized item fits within the configured limit.
- Fail closed with the maximum action-risk score when the latest encrypted compaction is oversized, instead of sampling with older context.
## Testing
- Cover exact-boundary and oversized compaction items, including oversized passthrough metadata.
- Verify that an oversized latest compaction bypasses sampling and prevents approval.
GitOrigin-RevId: 0b308e7bec0f41d46433dfdf656948cee5cba667
## What changed
- Allow `features.guardianv2` to remain a boolean toggle or specify classifier instructions, the review threshold, reasoning effort, and action and instruction token limits.
- Add transcript controls for included sources, per-entry and total token budgets, and the number of recent non-user entries.
- Validate configured ranges and relationships, expose them in the generated config schema, and apply the resolved settings throughout Guardian v2 classification and approval review.
## Testing
- Cover boolean compatibility, configuration parsing and boundaries, config-manager rejection, and the resulting classifier request and approval decision.
GitOrigin-RevId: dc018b53b782e2d6b4d6a795cca4945130a71678
## What changed
- Enable the stable `unified_exec` feature by default on every platform.
- Update cross-platform integration test expectations so `exec_command` and
`write_stdin` are exposed on Windows instead of `shell_command`.
GitOrigin-RevId: e5c864bacbde7eab109e7a0e399b8f7b843b384c
## What changed
- Add the stable, default-enabled `unbounded_connection_retries` feature.
- Require the feature for unbounded sampling retries after connection failures.
When disabled, connection failures use the existing bounded retry and
transport fallback path.
- Expose the feature in the generated configuration schema.
GitOrigin-RevId: bd80d02ef065ba924f805c29b639752fc817ed64
## What changed
- Preserve valid image content from completed `node_repl` Code Mode responses alongside text evidence for Guardian reviews.
- Enable multimodal evidence for models that require automatic `node_repl` review, or when both `guardian_enhanced_node_repl_transcripts` and `guardian_node_repl_transcript_images` are enabled.
- Bound retained and rendered evidence, deduplicate images already present in review history, and fall back to text-only evidence when the reviewer lacks image support or prompt capacity.
- Keep review evidence out of the parent turn input.
## Testing
- Cover feature gating, mixed text and image ordering, truncation and eviction, unsupported reviewers, prompt pressure, image detail normalization, and reused review sessions.
GitOrigin-RevId: a3e482402f7b3484401b231dadc662e6e3504fdf
## What changed
- Capture accepted, successful `node_repl` results from Code Mode and include them as bounded, untrusted evidence in Guardian review prompts.
- Enable the enhanced transcript through `guardian_enhanced_node_repl_transcripts` or when the selected model requires automatic Node REPL review.
- Keep this evidence out of the parent model history, exclude encrypted and failed results, and avoid resending admitted evidence when a Guardian session is reused.
- Clear retained evidence and invalidate review sessions when a thread is rolled back.
## Testing
- Add unit coverage for evidence ordering, escaping, truncation, and empty responses.
- Add an integration test covering feature-disabled, feature-enabled, and model-required behavior, including filtering and review-session reuse.
GitOrigin-RevId: edc3dca5d5b88d472a492f35531ec46889a89d72
## What changed
- Register `retain_client_developer_messages` as an under-development feature
that is disabled by default.
- Expose the feature in the configuration schema.
GitOrigin-RevId: dc56c48fe79a9f288b7fe0a11d97af992d36797f
## What changed
- Add the under-development `psp` feature and expose it in the config schema.
- Use the feature to attach the PSP cookie to first-party ChatGPT clients.
- Remove the hidden `--psp` flag and its process-scoped configuration plumbing.
- Preserve configured ChatGPT cookies when creating the PSP client used for GET and POST requests.
## Testing
- Update the config manager service test to verify that enabling `features.psp` retains the setting in the effective config and configures the expected ChatGPT cookie.
GitOrigin-RevId: 53acb5495d2ff71e4ed25f674a0cff787aea474a
## What changed
- Remove effective-config lockfile export, replay, and validation from session startup.
- Remove the `debug.config_lockfile` settings and generated schema entries.
- Remove feature-config materialization helpers that were only used to create lockfiles.
GitOrigin-RevId: a8c07c1c06325b3ec3dae9a97c36c2488d37df25
## What changed
- Add the `apply_patch_preserve_line_endings` feature, disabled by default, to
preserve CRLF, CR, and mixed line endings when `apply_patch` updates files.
- Apply the feature consistently to built-in patch handling and patches invoked
through shell, user-shell, unified-exec, and app-server command execution.
- Keep the active feature configuration authoritative over inherited, shell
snapshot, and client-provided environment values.
## Testing
- Cover line-ending behavior with the feature enabled and disabled for custom
tool calls, shell heredocs, command execution, and the `apply_patch` CLI.
GitOrigin-RevId: 531a7c66761959c650270559f57941929f03e6c4
## What changed
- Add the under-development `guardian_reuse_parent_compaction` feature.
- Restart Guardian review sessions after parent history rewrites and seed them with the latest encrypted compaction that has a response item ID.
- Keep the existing reviewer when a rewritten history has no reusable compaction, preserving authorization and restriction context held by that session.
## Testing
- Cover reuse-key invalidation and compaction eligibility.
- Verify review-session behavior across parent compaction and a subsequent summary-free history reset.
GitOrigin-RevId: 891805d3c3dca34ddda6e3bfc5097be4ff164267
## Why
Interrupting a turn should also stop code-mode work that the turn left running.
## What changed
- Add the disabled-by-default `code_mode_interrupt` feature.
- When an interrupted turn has the feature enabled, terminate all active code-mode cells and propagate cancellation through nested tool calls.
- Keep the reusable code-mode session alive so its stored state remains available to later turns.
## Testing
Add an integration test that interrupts a long-running nested tool, verifies that active and background cells are removed, and confirms that session state is preserved.
GitOrigin-RevId: 2b8634776a89b636318a39b9e9ad2eefc07cead8
## What changed
- Add the tool call ID to `_meta.callId` for every MCP tool request.
- Rename `features.tool_registry.include_tool_metadata` to
`features.tool_registry.turn_metadata_includes_tool_info` to clarify that the
setting controls authoritative tool information in per-turn metadata.
- Update config parsing, schema generation, and session config locking for the
renamed setting.
## Testing
- Cover `callId` metadata for custom, plugin, and Codex Apps MCP calls.
- Update strict-config, config-loading, feature-config, and config-lock tests for
the renamed setting.
GitOrigin-RevId: ac0e58c489b03bd9b55a356f545de86c8ecaf865
## What changed
Rename `features.tool_registry.include_tool_namespaces_info` to
`features.tool_registry.include_tool_metadata` across configuration parsing,
schema generation, resolved configuration locking, and tests. Update its
description to cover authoritative tool information in request metadata.
GitOrigin-RevId: 93b404483b71fed04031d767a41ac2bb70b836b2
