Decision protocol for managing the context/session state of an AI coding tool:
when to /clear, when to keep context, and how to detect "context bleed" — the
failure mode where stale conversation history biases the model against the
current task. Surfaces a discipline that Aider (/clear), Claude Code (/clear),
CrewAI (memory=False, re-instantiate), and LangGraph (new thread_id, subgraph
isolation) all encode separately but none name as a skill.
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Decision protocol for managing the context/session state of an AI coding tool:
when to /clear, when to keep context, and how to detect "context bleed" — the
failure mode where stale conversation history biases the model against the
current task. Surfaces a discipline that Aider (/clear), Claude Code (/clear),
CrewAI (memory=False, re-instantiate), and LangGraph (new thread_id, subgraph
isolation) all encode separately but none name as a skill.
phase
D
tier
common
frequency
daily
audience
coder-agents and human engineers who run multi-turn LLM coding sessions
One line: context is signal; stale context is noise; clearing restores
signal. A coding session is a sliding window of evidence. Early in a task
the window is pure signal. The longer it runs, the more dead ends, abandoned
plans, and superseded files accumulate — and at some point yesterday's good
context becomes today's bad bias. This skill is the discipline of noticing
that moment and acting on it with the smallest correct cut.
Source posture: every framework-specific claim is cited inline as
[tool/topic]. Resolve tags against references/R1-source-evidence.md (full
URLs) and references/R2-tool-commands.md (copy-pastable commands).
1. 何时激活 (When to Activate)
Activate this skill the moment any of these fire — they are the symptoms of
context bleed, not vague unease:
Topic shift inside a session. You finish feature A and start unrelated
bug B in the same window/REPL/thread. The A-history is now pure noise for B.
Length / window warning. The tool reports the context window is N% full,
or Aider's /tokens crosses ~25k — the empirically observed point where
"most models start to become distracted and become less likely to conform to
their system prompt" [aider/edit-errors].
Weird behavior — the tell-tale signs of bleed:
The model repeats a mistake you already corrected ("don't use
requests" → it uses requests again).
It references a file or decision you already removed / dropped.
It obeys an older instruction over the newest one (it conforms to turn
3 but ignores turn 30).
Edit-format errors climb (Aider "SEARCH block not found" recurs)
[aider/edit-errors].
The activation trap to avoid: when behavior gets weird, the reflex is to
rephrase the prompt, retry, or swap the model. If the history is polluted,
none of those help — you are arguing with a model that is reading stale
evidence. Activate this skill before reaching for a prompt rewrite.
Do not activate for: a single LLM call, a one-shot RAG query, or a brand new
session with <25k tokens that is behaving correctly. Hygiene on a clean window is
just superstition — see §6.
2. 核心心智模型 (Core Mental Model)
Context is signal; stale context is noise; clearing restores signal.
Three load-bearing ideas ride this axiom:
2.1 The session window is evidence, and evidence decays
Every turn you add to a session is evidence the model reasons over. Good
evidence (the current goal, the relevant files, the last working diff) raises
signal. Stale evidence (a failed approach you abandoned, a 5k-token search dump
you no longer need, a file you dropped) raises noise. The signal-to-noise ratio
of the window — not its absolute size — is what governs output quality. A 10k
window of pure noise is worse than a 30k window of pure signal.
2.2 There is a measured distraction threshold
Aider's tooling is built around a hard, published number: above ~25k tokens
"most models start to become distracted" [aider/edit-errors]. No other
framework publishes a number, but the heuristic transfers: treat ~25k as the
point where you should be actively shedding context, not passively letting it
grow. This is why /tokens exists and why it is the first move in Aider's
edit-error remediation, before swapping model or edit format [aider/edit-errors].
2.3 Clearing is a cut, and cuts have a size
"Clear the context" is not one operation — it is a family ordered by blast
radius. The skill is choosing the smallest cut that removes the noise:
smallest cut largest cut
┌───────────────┬────────────────┬───────────────┬──────────────────┐
│ drop one item │ trim history │ clear history │ fresh session / │
│ (a file, a │ (keep last N │ (keep files, │ new thread_id │
│ message) │ messages) │ drop history) │ (zero carry-over)│
└───────────────┴────────────────┴───────────────┴──────────────────┘
OP-004 partial OP-004 partial OP-002 save+clear OP-003 fresh
Reaching for "fresh session" when a single /drop would do is as wrong as never
clearing at all. Match the cut to the noise.
2.4 The window is not the only state
A subtle trap: "session state" is broader than the visible transcript. CrewAI's
memory=True keeps a separate persistent store (LanceDB by default) that a
Crew() re-instantiation does not wipe [crewai/memory]. LangGraph's state
lives in a checkpointer keyed by thread_id — a new thread_id is clean,
but reusing the old one resumes from the last checkpoint [langgraph/persistence].
"I cleared the chat but it still remembers" almost always means a persistent
store you didn't clear (§6, AP-005).
3. SOP 工作流 (Standard Operating Procedure)
The flow is four steps: recognize → save what's worth → clear → restart
focused. Walk it top-down; each step has a gate.
Step 1 — Recognize (don't act yet)
Gate: name the symptom in one line before touching anything. "The model is
still using the JWT approach we abandoned." "Token count is 38k and edits are
failing." Naming forces you to identify the single offending source —
stale history, an oversized item, or the wrong file set — which then selects the
cut size. If you cannot name a symptom, you do not have bleed; do not clear
(§6, AP-002). This is OP-001.
Step 2 — Save what's worth keeping (before any clear)
Gate: is there a durable artifact in this session you'd hate to retype? A
decision, a file list, a working plan, a passing-test state. If yes,
externalize it to something that survives the clear:
Code → it's already safe if committed (git commit); commit before you clear.
Decisions / conventions → write to CONVENTIONS.md (Aider re-loads it via
--read) or a scratch note [aider/conventions].
The plan / state-of-the-world → ask the model for a one-paragraph summary
(decisions made, files touched, tests passing, open questions), copy it.
The keepers go to disk/git/clipboard — never left only in the volatile
window you are about to wipe. This is OP-002.
If the bug you're hunting depends on the exact phrasing the model used three
turns ago, a summary is too lossy — save the raw transcript instead. But if you
need the raw transcript, ask whether you actually needed to clear.
For code tools, the working tree on disk is never touched by a chat clear —
/clear resets the transcript, not your files [claude-code/slash][aider/commands].
Step 4 — Restart focused
Gate: the first message of the new context is a focused goal statement, not a
data dump. Open with the saved one-paragraph summary (OP-002) plus the single
current objective. Do not paste the old transcript back — that recreates the
pollution with extra steps (§6, AP-003). A clean window seeded with distilled
state is the entire payoff of clearing.
4. 操作模型 (Operation Models)
Each operation: Trigger → Action → Output → Evidence. Full machine-readable
form in intermediate/operation_candidates.json; commands in references/R2.
OP-001 · Detect context bleed
Trigger: Any §1 symptom — topic shift, length warning, or weird behavior
(repeats corrected mistake / cites removed item / obeys old over new).
Action: Stop. Do not edit the prompt, retry, or swap model. Name the
symptom in one line and identify the single offending source.
Output: A named symptom and a chosen cut (OP-002/003/004/006).
Trigger: Continue the same topic but history is full of dead ends.
Action: (1) Have the model summarize decisions + state in one paragraph.
(2) Copy it to disk/clipboard. (3) Clear: Aider /clear, Claude Code
/clear, CrewAI re-instantiate Crew, LangGraph new thread_id, web "New
chat". (4) Paste the summary as the first message.
Output: Fresh history seeded with distilled state; files/working tree untouched.
Trigger: New feature/bug/task AND nothing from the old session is needed.
Action: Start a genuinely new session. Aider: relaunch or /reset. Claude
Code: /clear or exit. CrewAI: a newCrew() instance (do not reuse).
LangGraph: a fresh thread_id (do not reuse the old uuid). Web: New chat.
Output: Zero bleed; cheapest possible window for the new task.
Evidence: [crewai/memory]; [langgraph/persistence] (different thread_id = different conversation).
OP-004 · Partial clear (drop a subset, keep continuity)
Trigger: History is mostly good; one item (a big paste, a stale tool
result, an unneeded file) is the noise.
Action: Surgical removal, not a full clear. Aider: /drop <file> + confirm
with /tokens. LangGraph: update_state(config, {"messages": trimmed}) or
RemoveMessage. CrewAI: trim a Task's context=[...] to only the needed
upstream tasks.
OP-005 · Fresh thread vs reuse (where to put the seam)
Trigger: Starting a related-but-new subtask; unsure whether to continue.
Action: Default to a fresh thread when the new subtask shares <30% of
relevant context with the old one. Reuse only when the new task strictly
builds on the live state (next step of the same diff).
Output: A session boundary placed at the natural task seam.
OP-006 · Isolate a noisy sub-task in a sub-context
Trigger: A noisy sub-investigation (debugging, big search, exploratory
dump) would pollute the main session if run inline.
Action: Run it in an isolated context and return only the conclusion.
LangGraph: a subgraph with its own state schema. CrewAI: a separate Crew
with memory=False, return result.raw. Aider: a second window whose only
output back to the main task is a committed diff or a note.
Output: Main session receives a one-line conclusion, not the full trace.
Evidence: [langgraph/subgraphs] (child state isolated to shared keys);
[crewai/memory].
OP-007 · Memory off during debug
Trigger: Debugging or evaluating behavior; you need reproducible traces.
Action: Turn off persistent/auto memory so each run starts from a known
state. CrewAI: memory=False (and wipe ~/.crewai/storage/ if memory=True
was used). LangGraph: InMemorySaver or a throwaway thread_id. Aider:
/clear before each repro.
Output: Deterministic starting state; runs become comparable.
Evidence: [crewai/memory] (memory runs extra LLM calls, hard to trace);
[langgraph/persistence].
OP-008 · Inspect before you cut
Trigger: You suspect bloat but haven't confirmed the source.
Action: Look first. Aider: /tokens, /ls, /map. Claude Code:
/context. LangGraph: len(state["messages"]) / get_state. CrewAI: read the
LangSmith/MLflow trace.
Output: The offending source identified, so OP-002/004 cut the right thing.
Trigger: Long-lived setups accumulate abandoned threads / huge old stores.
Action: Expire sessions past a threshold (e.g. 24h). LangGraph: a TTL sweep
on the checkpointer for interrupted-but-never-resumed threads. CrewAI: clear
the long-term store. Aider: end sessions; don't keep one REPL alive for days.
Output: Bounded state growth; no zombie context resurfacing.
Evidence: [langgraph/hitl] (without a sweep, "state is held in the
checkpointer indefinitely").
5. 困境决策案例 (Dilemma Cases)
Case 1 · "The fix depends on a prior file — but bleed is getting worse"
困境: You're 20 turns into refactoring auth.py. The model now mixes in a
JWT approach you explicitly abandoned at turn 8, and the correct new code
genuinely depends on the session.py changes made at turn 5. Clearing risks
losing the dependency; not clearing keeps the bleed.
约束:
The session.py changes are load-bearing for the current edit.
The abandoned JWT history is actively misleading the model.
You don't want to retype the whole refactor plan.
决策步骤:
Recognize (OP-001): name it — "model resurrects abandoned JWT; correct
edit depends on the turn-5 session.py change."
Make the dependency durable, not conversational (OP-002): the turn-5
change is code — commit it (git commit). Now it lives in the working tree,
not the volatile transcript. The model will see the file content after a
/clear because /clear keeps /add-ed files [aider/commands].
Prefer the smallest cut: if only the JWT turns are noise, OP-004 partial —
LangGraph update_state to drop those messages; Aider has no message-level
drop, so escalate to OP-002.
Save + clear (OP-002): one-paragraph summary ("refactoring auth.py to
use the new session.py API committed at ; do NOT use JWT"), then
/clear, then paste the summary.
Restart focused: the new window has the committed file + the summary —
the dependency survives, the bleed is gone.
结果: The prior-file dependency is preserved through git, not through chat
history — so clearing is safe. The general rule: if the thing you fear losing
can be made durable (committed, written to a note), clearing is always safe.
可提取的操作: OP-002 + OP-001. Never let "I might need it" keep a polluted
window alive — externalize the keeper, then cut freely.
Case 2 · "Long task is 80% done — restart clean or push through?"
困境: A multi-step migration is 80% complete. The window is at 34k tokens
(past the ~25k distraction line [aider/edit-errors]), edits are starting to
fail intermittently, and the model occasionally references a step it already
finished. Do you restart (risking the 80% momentum) or push through the last 20%?
约束:
Restarting costs a re-summary + reload; pushing through risks the failing
edits corrupting the near-done work.
The done 80% is mostly committed code already.
The remaining 20% is well-defined.
决策步骤:
Recognize (OP-001): "34k tokens, intermittent edit failures, model
re-references finished steps" — this is bleed at the distraction threshold,
not bad luck.
Audit the keepers (OP-008 → OP-002): is the 80% durable? If committed,
the momentum lives in git, not the window — restarting loses almost nothing.
If uncommitted, commit first.
Decision rule on the seam (OP-005): the remaining 20% shares little
relevant context with the noisy 80%-of-failed-attempts history (the code is
the shared part, and that's on disk). Shared conversational context is low →
favor a fresh window.
Save + clear (OP-002): summarize the migration state ("steps 1-8 done,
committed at ; remaining: steps 9-10 = update callers + delete shim"),
/clear, paste, finish the last 20% in clean signal.
Counter-case: if the last 20% is a single small edit and tokens are only
slightly over, the cheaper move is OP-004 — /drop the unused files and push
through. Don't pay the restart tax for one trivial step.
结果: At 80% with committed work, a clean restart usually wins — you finish
the hardest 20% on full signal instead of fighting a distracted model. The
threshold is whether the done work is durable; if it is, the sunk-cost feeling of
the long session is an illusion.
可提取的操作: OP-005 + OP-002. "Almost done" is not a reason to push through a
distracted window; it's a reason to make the done part durable and finish clean.
Case 3 · "I cleared it but the model still remembers" (the hidden-store trap)
困境: A CrewAI debugging session: you re-instantiated the Crew() object
between runs, but the agent still recalls a fact from a previous kickoff that you
thought you'd wiped.
约束: You need reproducible runs; the lingering recall makes traces unreadable.
决策步骤:
Recognize (OP-001): the symptom is "cleared but remembers" → the state is
not in the window you cleared. It's in a persistent store (§2.4).
CrewAI memory=True keeps a separate LanceDB store under ~/.crewai/ that a
Crew() re-instantiation does not touch [crewai/memory].
Memory off for debug (OP-007): set memory=False, and if a prior run used
memory=True, wipe the store: rm -rf ~/.crewai/storage/.
Generalize: LangGraph reusing a thread_id resumes from a checkpoint — use a
fresh thread_id (OP-003). Web UIs with cross-chat memory: "New chat" does
not clear it; clear it in Settings [langgraph/persistence].
结果: Deterministic runs once the actual state location is cleared.
可提取的操作: OP-007. Before concluding "clearing doesn't work," ask which
state you cleared — the transcript or the persistent store.
6. 反模式与边界 (Anti-Patterns & Boundaries)
#
Anti-pattern
Symptom
Fix
AP-001
Never-clear marathon
Hours-long session; model "forgets" instructions, invents files dropped 50 turns ago
Clear on any topic shift OR every ~25k tokens (OP-002). /clear is a stop-the-line tool, not a panic button [aider/edit-errors]
AP-002
Reflexive clear-every-message
Clearing so often the model loses useful continuity — re-asks answered questions, forgets which files are in scope
Clear only on a named symptom (OP-001). "Feels off" is not a trigger
AP-003
Dump the whole old transcript back in
You /clear then paste 50 messages back — pollution recreated with extra steps
Paste a summary (OP-002), not raw history. If you truly need the raw history, you didn't need to clear
AP-004
Clear instead of fixing the real bug
/clear after every failed edit, but the bug is in the prompt or model
If the failure repeats after a clean clear, the history wasn't the cause — fix the prompt/model
AP-005
Forget memory is on (hidden store)
"Cleared" the session but the agent still recalls a fact
The persistent store survived (§2.4, Case 3). memory=False in debug, or wipe the store [crewai/memory]
AP-006
Keep huge old dumps "just in case"
A 10k-token log/file sits in context for 30 turns "in case it's useful"
If unused for several turns, /drop it (OP-004). It can be re-added in seconds; the noise tax is paid every turn
AP-007
Buy a bigger window instead of clearing
Moving to a 1M-context model to avoid /clear
A bigger window doesn't remove stale signal — it just lets more noise accumulate. Signal-to-noise, not size, governs quality
Hard boundaries — when this skill does not apply:
A single LLM call or one-shot RAG query: no session to keep hygienic.
A clean window (<~25k, behaving correctly, on-topic): clearing is superstition.
When the real problem is the prompt or the model: clearing the history is
treating a symptom (AP-004). Confirm the bug isn't in the live turn first.
7. 跨框架对照 (Cross-Framework Reference)
All surveyed coding tools expose the same primitive under different names. The
convergence is itself the argument that this SOP deserves to be a surfaced skill.
Need
Aider
Claude Code
CrewAI
LangGraph
ChatGPT/Gemini web
Inspect context size
/tokens
/context
LangSmith / MLflow trace
len(state["messages"])
(UI hint)
Clear chat, keep files
/clear
/clear
re-instantiate Crew()
new thread_id
New chat
Hard reset everything
/reset
exit CLI
new process + wipe store
new thread_id
New chat (+ clear memory in Settings)
Partial clear (drop subset)
/drop <files>
n/a
trim Task context=[...]
update_state({"messages":...}) / RemoveMessage
n/a
Isolate a sub-task
second window
sub-process
separate Crew, memory=False
subgraph w/ own schema
New chat
Memory off (debug)
/clear per repro
/clear per repro
memory=False
InMemorySaver / throwaway thread
n/a
Concrete, copy-pastable commands per tool are in references/R2-tool-commands.md.
The four primitives, side by side
Aider[aider/commands]: file-level granularity. /clear wipes chat but
keeps the /add-ed working set (so the model still knows what it can edit);
/reset wipes both. /drop is the partial cut; /tokens is the gauge. The
cleanest published distraction threshold (~25k) lives here [aider/edit-errors].
Claude Code[claude-code/slash]: /clear resets the in-memory transcript;
files on disk are the durable state and are never touched. /context to
inspect. Hard reset = exit the process.
CrewAI[crewai/memory]: session state is split — the in-process Crew
and an opt-in persistent store. memory=False (the default) is the debug
posture; a Crew() re-instantiation clears the in-process state but not the
persistent LanceDB store. agent.reset() / fresh Agent() clears per-agent
state. Always memory=False while debugging.
LangGraph[langgraph/persistence][langgraph/subgraphs]: state is keyed
by thread_id in a checkpointer. A new thread_id = a clean conversation;
reusing one resumes from the checkpoint. update_state(messages=...) is the
finest-grained partial clear in any surveyed tool. Subgraphs give structural
isolation — a sub-task with its own state schema can't bleed into the parent
except on shared keys, the architecture-level analogue of /clear.
Picking across them
The SOP is identical everywhere: detect bleed → save what's durable → cut at
the smallest correct size → restart focused. Only the command changes. If you
work across tools, internalize the move, not the syntax — the table above maps
the move onto each tool's command.
附录 · 引用速查 (Citation Index)
Short tags used inline → full sources in references/R1-source-evidence.md.
