Where a rule arrives

A rule that lives in a file, or in the record, does something only if the host puts its text in front of the model. This page says, for each host the repository starts without an account and without a model, whether it does, in which place the rule is kept, and at which moment of a session. Nothing here says that the model reads the rule or follows it: a request shows what was put in front of the model, never what it made of it.

What was measured

One rule carries a sentinel, a word that nothing the host or the product sends contains (quillfeather-7731), and the measurement is whether the sentinel is in a request the host sends to its model. The host is the real binary, unmodified, in a network namespace that holds only loopback, against a stand-in for its model that answers what the case scripts. The same cases run for the version the workflow pins on every pull request and for the newest one every week; the version is in each run’s “Host measured” summary, and a host that changes what it does turns that host’s job red.

Where the rule is kept (the rows):

• No rule anywhere, the control. It must be absent at every moment of every host, or what the instrument sees does not come from the rule.
• In AGENTS.md.
• In the host’s own instructions file: .claude/rules/ for Claude Code, a .github/instructions/*.instructions.md that applies to every file for Copilot CLI, GEMINI.md for Gemini CLI, QWEN.md for Qwen Code. Codex and OpenCode read AGENTS.md as their own, so for them this row is the one above.
• Behind an import: a file the instructions file names with @, where the rule is in the named file (CLAUDE.md, GEMINI.md or QWEN.md where the host has one, otherwise AGENTS.md).
• Behind a mention: the same file says in prose where the rules are, and the rule is only in the file it names. The case also requires that the sentence of the mention reached the model, so that “not arrived” is not a file the host never read.
• In the mnema record: a decision in force that governs a path, with the plugin or server of mnema configured the way the host contract already does.

The moments (the columns):

• Start: the first request of the work. For OpenCode that is the first one that offers a tool, since it asks the model for a title before.
• Late: a session of three calls to the shell, one per turn, and the request that carries the most results the host sent before it asked for a summary or, where it asked for none, its last. Supposed by nobody: a host sends its conversation again with each request, and this reads it.
• After a compaction: the stand-in tells the host, in the usage of the turn that answers the third call, that the window is full (and, where the host decides by a limit of its own that it lets a person set, Claude Code, Codex and OpenCode, the limit is set small); the host asks for a summary of the conversation, and the stand-in answers with a text of its own that does not hold the rule. What the next request carries of the rule is what the host or the product put back; the case proves that request is the compacted conversation by what it carries of the summary and of the results. A gemini -p run has one turn of the person and its compression finds nothing to compress before a second one, so for Gemini CLI the case takes a second run that resumes the session (--resume): the host restores the conversation, compacts it, and what the request after the summary carries includes what the resumed session’s own start put in front of the model again. That reading says nothing about a compaction in a session that was never resumed (the case).
• At an edit: a write that is permitted and that a rule only governs. The rule arrives if it is in the result of the write, or beside it: for the record, in what the host put in the conversation from the item of the call on (its output, and what a hook said for it), never in the request as a whole, which in that arm already carries the rule from the start. The same read, with the push switched off in the same record (mnema switch off edit-rules-push), finds nothing; that is what says the reading sees the push and not the opening. A refusal is another thing, held by the cases that open and refuse in each host (*-opens-and-refuses.*.test.ts), and a rule kept in a file has no channel at a write.

The four words in a cell: arrived, not arrived (a reading was made and found nothing), not applicable and not measured, each of the last two with its reason in the note under the table. A reading that was made under a condition (Gemini CLI’s after a compaction, in a resumed session) carries a note too.

The table

Claude Code

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in AGENTS.md	arrived	arrived	arrived	not applicable (note 1)
the rule in the host’s own instructions file	arrived	arrived	arrived	not applicable (note 1)
the rule in a file the instructions file imports with @	arrived	arrived	arrived	not applicable (note 1)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not arrived	not applicable (note 1)
the rule in the mnema record, addressed at a path	arrived	arrived	arrived	arrived

1. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model

Codex

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in AGENTS.md	arrived	arrived	arrived	not applicable (note 1)
the rule in the host’s own instructions file	not applicable (note 2)	not applicable (note 2)	not applicable (note 2)	not applicable (note 2)
the rule in a file the instructions file imports with @	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not arrived	not applicable (note 1)
the rule in the mnema record, addressed at a path	arrived	arrived	arrived	arrived

1. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model
2. Not applicable: the instructions file Codex reads is AGENTS.md, the place above

OpenCode

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in AGENTS.md	arrived	arrived	arrived	not applicable (note 1)
the rule in the host’s own instructions file	not applicable (note 2)	not applicable (note 2)	not applicable (note 2)	not applicable (note 2)
the rule in a file the instructions file imports with @	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not arrived	not applicable (note 1)
the rule in the mnema record, addressed at a path	arrived	arrived	arrived	arrived

1. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model
2. Not applicable: the instructions file OpenCode reads is AGENTS.md, the place above

GitHub Copilot CLI

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not measured (note 1)	not applicable (note 2)
the rule in AGENTS.md	arrived	arrived	not measured (note 1)	not applicable (note 2)
the rule in the host’s own instructions file	arrived	arrived	not measured (note 1)	not applicable (note 2)
the rule in a file the instructions file imports with @	arrived	arrived	not measured (note 1)	not applicable (note 2)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not measured (note 1)	not applicable (note 2)
the rule in the mnema record, addressed at a path	arrived	arrived	not measured (note 1)	arrived

1. Not measured: with copilot -p the host asks for its summary at the end of the run and the run ends; a second run that resumed the session sent the whole conversation again, the results and not the summary, so no request of a compacted conversation was seen
2. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model

Gemini CLI

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not arrived (note 1)	not applicable (note 2)
the rule in AGENTS.md	not arrived	not arrived	not arrived (note 1)	not applicable (note 2)
the rule in the host’s own instructions file	arrived	arrived	arrived (note 1)	not applicable (note 2)
the rule in a file the instructions file imports with @	arrived	arrived	arrived (note 1)	not applicable (note 2)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not arrived (note 1)	not applicable (note 2)
the rule in the mnema record, addressed at a path	arrived	arrived	arrived (note 1)	arrived

1. Resumed: read in a second run that resumes the session (--resume), which starts the session again: it says nothing about a compaction in a session that was never resumed
2. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model

Qwen Code

Where the rule is kept	start	late	after a compaction	at an edit
no rule anywhere (the control)	not arrived	not arrived	not arrived	not applicable (note 1)
the rule in AGENTS.md	arrived	arrived	arrived	not applicable (note 1)
the rule in the host’s own instructions file	arrived	arrived	arrived	not applicable (note 1)
the rule in a file the instructions file imports with @	arrived	arrived	arrived	not applicable (note 1)
the rule in a file the instructions file only mentions	not arrived (the mention did)	not arrived	not arrived	not applicable (note 1)
the rule in the mnema record, addressed at a path	arrived	arrived	arrived	arrived

1. Not applicable: a file is read when the session opens and has no channel at a write; the late column says whether it is still in front of the model

What each host did

• Claude Code. The rule in AGENTS.md, in the host’s own instructions file and behind an @ import arrived at the start, late and after a compaction. The rule in a file that is only mentioned did not arrive at the start, late and after a compaction (the sentence that mentions the file did, at the start). The rule in the mnema record arrived at the start, late, after a compaction and at an edit. The files are read into the block the host opens its first message with; the record is put there by the plugin’s SessionStart hook, which runs again after a compaction, and by a hook that runs beside the result of a write.
• Codex. The rule in AGENTS.md arrived at the start, late and after a compaction. The rule behind an @ import did not arrive at the start, late and after a compaction. The rule in a file that is only mentioned did not arrive at the start, late and after a compaction (the sentence that mentions the file did, at the start). The rule in the mnema record arrived at the start, late, after a compaction and at an edit. An @ import is not expanded by the host. At an edit, the hook that runs before the patch answers with the rules of the path as context, and the host records it as an item of its own between the call and its output.
• OpenCode. The rule in AGENTS.md arrived at the start, late and after a compaction. The rule behind an @ import did not arrive at the start, late and after a compaction. The rule in a file that is only mentioned did not arrive at the start, late and after a compaction (the sentence that mentions the file did, at the start). The rule in the mnema record arrived at the start, late, after a compaction and at an edit. An @ import is not expanded by the host. At an edit, the plugin module keeps what the gate answered for the call and appends it to the result of the write.
• GitHub Copilot CLI. The rule in AGENTS.md, in the host’s own instructions file and behind an @ import arrived at the start and late; was not measured after a compaction. The rule in a file that is only mentioned did not arrive at the start and late (the sentence that mentions the file did, at the start); was not measured after a compaction. The rule in the mnema record arrived at the start, late and at an edit; was not measured after a compaction. At an edit, the hook that runs after the write answers with the rules of the path as context, and the host appends it to the result of the write.
• Gemini CLI. The rule in AGENTS.md did not arrive at the start, late and after a compaction. The rule in the host’s own instructions file and behind an @ import arrived at the start, late and after a compaction. The rule in a file that is only mentioned did not arrive at the start, late and after a compaction (the sentence that mentions the file did, at the start). The rule in the mnema record arrived at the start, late, after a compaction and at an edit. AGENTS.md is not among the files it reads with the default settings (its context.fileName can list it). The cells after a compaction are read in a second run that resumes the session (--resume), which starts the session again. At an edit, the hook that runs after the write answers with the rules of the path as context, and the host appends it to the result of the write.
• Qwen Code. The rule in AGENTS.md, in the host’s own instructions file and behind an @ import arrived at the start, late and after a compaction. The rule in a file that is only mentioned did not arrive at the start, late and after a compaction (the sentence that mentions the file did, at the start). The rule in the mnema record arrived at the start, late, after a compaction and at an edit. At an edit, the hook that runs before the write answers with the rules of the path as context, and the host puts it in the result of the write.

How it is held

The table is the-arrival-table.ts of the host contract, and this page shows it as it is. Each host has a case file that starts the host, reads the requests, and requires each cell above that is a reading to be what the host did: Claude Code, Codex, OpenCode, Copilot CLI, Gemini CLI and Qwen Code. A test of the main suite holds this page to the table (the-arrival-page-is-the-table.test.ts), and holds the control to never arriving.

What is not held here

• That the model reads, weighs or follows the rule. That takes a real model, and is another measurement.
• A host that is not here: VS Code’s agent runs only under an editor and Cursor needs an account, so neither is in this table (How each claim is held).
• Another place a rule can live that this does not take: a rule a person types into the session, a user-level instructions file, a skill. Each of these is another row.
• A conversation compacted by a host in a way the stand-in does not provoke: a window filled by real content, a command the person types.