feat: LLM and User-controlled compaction via `new_session` tool by taoeffect · Pull Request #2333 · charmbracelet/crush

taoeffect · 2026-03-01T04:21:15Z

This PR closes #2331 by adding:

A new_session tool that allows customizable compaction
A new compaction method switching menu to the UI
Injecting information about the remaining context into the system prompt when the compaction method is switched to LLM/user-driven
By default, the new_session tool is instructed to trigger at 75% context remaining. As a fallback, the auto-compaction remains enabled in case the LLM fails to trigger it.

I think this PR also closes #2240 because new_session can handle custom compaction instructions.

I have read CONTRIBUTING.md.
I have created a discussion that was approved by a maintainer (for new features).

Co-authored by Opus 4.6 using Crush.

Introduce a new agent tool that allows the LLM to create a fresh session when working on long-running tasks, carrying forward a summary of progress and remaining work. This prevents context exhaustion during complex multi-step tasks. The implementation spans four layers: - Tool definition (`internal/agent/tools/new_session.go`): Defines the tool with a `summary` parameter and returns a sentinel `NewSessionError` that propagates up through the agent coordinator. - Coordinator integration (`internal/agent/coordinator.go`): Registers the tool in `buildTools()` alongside existing tools. - UI handling (`internal/ui/model/ui.go`, `internal/ui/chat/`): Catches `NewSessionError` in `sendMessage`, emits a `newSessionMsg` that creates a new session and auto-sends the summary as the first message. Adds a renderer for the tool's pending/completed states. - Config allowlist (`internal/config/config.go`): Adds `"new_session"` to `allToolNames()` so the tool is not filtered out before being sent to the LLM provider. Updates corresponding test expectations.

Introduce a compaction method toggle (auto vs LLM/user-driven) that controls how context window management works. In LLM mode, a <context_status> block is injected each turn so the model can track usage and invoke the new_session tool proactively. The setting is selectable via the command palette and persists across sessions in the data config.

- Use system role (not user) for context status message to avoid provider alternation violations and LLM misdirection - Validate empty/whitespace summaries in new_session tool, returning a tool error so the LLM can retry instead of propagating an agent error - Clamp used_pct to 100 and remaining_tokens to 0 consistently - Document one-step token lag in contextStatusMessage - Register new_session tool only when compaction method is LLM - Normalize CompactionMethod zero value "" to "auto" in setDefaults - Add trailing newline to new_session.md Assisted-by: Claude via Crush <crush@charm.land>

charmcli · 2026-03-01T04:21:25Z

All contributors have signed the CLA ✍️ ✅
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taoeffect · 2026-03-01T04:22:00Z

I have read the Contributor License Agreement (CLA) and hereby sign the CLA.

Copilot

Pull request overview

This PR adds LLM/user-controlled context compaction by introducing a new_session tool, a new CompactionLLM mode, context-status injection into system prompts, and a UI dialog for switching between compaction modes. It closes issue #2331.

Changes:

Added new_session agent tool (returns a sentinel error to trigger UI-side session reset with a summary)
Added CompactionLLM compaction mode with context-status injection, and compactionFlags helper to derive disableAutoSummarize/disableContextStatus from config
Added Compaction dialog for selecting the compaction method, wired into the command palette

Reviewed changes

Copilot reviewed 20 out of 21 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
`internal/agent/tools/new_session.go`	New sentinel tool that signals session reset via `NewSessionError`
`internal/agent/tools/new_session.md`	Tool description embedded in the tool for the LLM
`internal/agent/tools/new_session_test.go`	Tests for the new tool
`internal/agent/agent.go`	Migrated `disableAutoSummarize` to thread-safe `csync.Value`; added `disableContextStatus` field and `SetCompactionFlags` interface method; injects context-status system message per turn
`internal/agent/coordinator.go`	Added `compactionFlags` helper, named field initialization, `new_session` tool conditional registration, and `SetCompactionFlags` call in `UpdateModels`
`internal/agent/coordinator_test.go`	Updated mock to implement new `SetCompactionFlags` interface method
`internal/agent/compaction_flags_test.go`	Tests for `compactionFlags` helper function
`internal/agent/set_compaction_flags_test.go`	Tests for `SetCompactionFlags` and round-trip behavior
`internal/agent/context_status_test.go`	Tests for `contextStatusMessage` method
`internal/agent/common_test.go`	Updated `testSessionAgent` to use named struct fields
`internal/config/config.go`	Added `CompactionMethod` type, `CompactionAuto`/`CompactionLLM` constants, `Options.CompactionMethod` field, `SetCompactionMethod` method, `new_session` in `allToolNames`
`internal/config/load.go`	Added `CompactionMethod` default in `setDefaults`
`internal/config/load_test.go`	Updated tool list assertions and added compaction method default test
`internal/config/compaction_method_test.go`	Tests for `SetCompactionMethod` persistence and defaults
`internal/ui/dialog/compaction.go`	New dialog for selecting compaction method
`internal/ui/dialog/actions.go`	Added `ActionSelectCompactionMethod` action
`internal/ui/dialog/commands.go`	Added "Select Compaction Method" to the command palette
`internal/ui/model/ui.go`	Handles `newSessionMsg`, `ActionSelectCompactionMethod`, and opens compaction dialog
`internal/ui/chat/new_session.go`	New chat UI renderer for the `new_session` tool call
`internal/ui/chat/tools.go`	Wires `NewSessionToolName` to `NewNewSessionToolMessageItem`
`.gitignore`	Added project-local working files

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internal/agent/agent.go

internal/agent/tools/new_session.md

Handle NewSessionError specially in agent.Run() error dispatch to avoid persisting a spurious "Provider Error" finish entry. Update new_session.md to document the context_window field in the context_status payload.

…ously loaded skills

…g files across sessions The file history system hit a UNIQUE constraint violation on (path, session_id, version) when the same file was edited in multiple sessions — particularly after the new_session tool created a fresh session that re-edited files from a prior session. Two bugs were identified: 1. CreateVersion() used ListFilesByPath which queried ALL sessions for a file path, then picked max(version)+1 globally. But the UNIQUE constraint is per-session, so version numbers from session A leaked into session B, causing sparse versions and eventual collisions. 2. Create() always hardcoded version 0 (InitialVersion). The retry loop only attempted 3 increments (0, 1, 2), so if those versions already existed for (path, session_id), it exhausted retries and failed. The fix: - Add a ListFilesByPathAndSession SQL query scoped to a single session. - Change CreateVersion() to use the session-scoped query so version numbers are independent per session. - Make Create() delegate to CreateVersion() so it always picks the correct next version instead of hardcoding 0. - Add regression tests covering both bugs plus basic version semantics.

Wrap goose.SetBaseFS and goose.SetDialect in sync.Once to prevent concurrent writes to package-level globals when parallel tests each call db.Connect. Assisted-by: Opus 4.6 via Crush <crush@charm.land>

compactionFlags() was returning disableAutoSummarize=true for CompactionLLM mode, which completely disabled the StopWhen auto-compaction check. This meant that if the LLM failed to call new_session (expected at ~75% context usage), there was no fallback — context would silently overflow. Now auto-summarize stays enabled in LLM mode so it kicks in at 80% as a safety net. Assisted-by: Claude via Crush <crush@charm.land>

taoeffect · 2026-03-05T03:49:17Z

Updated behavior and edited the PR description to add:

By default, the new_session tool is instructed to trigger at 75% context remaining. As a fallback, the auto-compaction remains enabled in case the LLM fails to trigger it.

taoeffect · 2026-03-05T03:59:15Z

One question I have for @andreynering: should it keep/remember the permissions granted from the current session when the new_session tool is called, or reset them as it currently does?

taoeffect added 3 commits February 28, 2026 16:42

taoeffect requested a review from a team as a code owner March 1, 2026 04:21

taoeffect requested review from Copilot, meowgorithm and raphamorim and removed request for a team March 1, 2026 04:21

charmcli added area: session area: tools labels Mar 1, 2026

Copilot started reviewing on behalf of taoeffect March 1, 2026 04:21 View session

taoeffect mentioned this pull request Mar 1, 2026

Better tools for long-term work: detecting remaining context + new_session tool for AI #2331

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Copilot AI reviewed Mar 1, 2026

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fix: address Copilot review feedback for new_session tool

6dfbacc

Handle NewSessionError specially in agent.Run() error dispatch to avoid persisting a spurious "Provider Error" finish entry. Update new_session.md to document the context_window field in the context_status payload.

taoeffect changed the title ~~LLM and User-controlled compaction via new_session tool~~ feat: LLM and User-controlled compaction via new_session tool Mar 1, 2026

taoeffect mentioned this pull request Mar 1, 2026

Crush clears the context losing all work #2240

Open

taoeffect added 7 commits March 1, 2026 08:15

explicitely state new sessions must preserve user directive and previ…

cebbc19

…ously loaded skills

improve new_session.md instructions even more

cd8512c

fix: resolve data race in goose global state during parallel tests

299d00a

Wrap goose.SetBaseFS and goose.SetDialect in sync.Once to prevent concurrent writes to package-level globals when parallel tests each call db.Connect. Assisted-by: Opus 4.6 via Crush <crush@charm.land>

Merge branch 'main' into taoeffect

a034d1f

Merge branch 'main' into taoeffect

d1c4bce

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feat: LLM and User-controlled compaction via `new_session` tool#2333

feat: LLM and User-controlled compaction via `new_session` tool#2333
taoeffect wants to merge 11 commits intocharmbracelet:mainfrom
taoeffect:new_session_tool

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