Remove unused apply_patch prompt fallback (#38291)

## What changed

- Delete the unused standalone `apply_patch` instruction template and its
  `codex-prompts` export.
- Simplify prompt-caching coverage to assert that requests use the model's base
  instructions.

GitOrigin-RevId: 8c0dc9426d9ac0184d587272622db608a75e8436

codex-rs/core/tests/suite/prompt_caching.rs

@@ -6,7 +6,6 @@ use std::path::Path;
 use codex_core::TurnInputRequest;
 use codex_core::shell::default_user_shell;
 use codex_features::Feature;
-use codex_prompts::APPLY_PATCH_TOOL_INSTRUCTIONS;
 use codex_protocol::config_types::CollaborationMode;
 use codex_protocol::config_types::ModeKind;
 use codex_protocol::config_types::ReasoningSummary;
@@ -198,23 +197,11 @@ async fn prompt_tools_are_consistent_across_requests() -> anyhow::Result<()> {
     ]);
     let body0 = req1.single_request().body_json();
 
-    let expected_instructions = if expected_tools_names.contains(&"apply_patch") {
-        base_instructions
-    } else {
-        [base_instructions, APPLY_PATCH_TOOL_INSTRUCTIONS.to_string()].join("\n")
-    };
-
-    assert_eq!(
-        body0["instructions"],
-        serde_json::json!(expected_instructions),
-    );
+    assert_eq!(body0["instructions"], serde_json::json!(base_instructions),);
     assert_tool_names(&body0, &expected_tools_names);
 
     let body1 = req2.single_request().body_json();
-    assert_eq!(
-        body1["instructions"],
-        serde_json::json!(expected_instructions),
-    );
+    assert_eq!(body1["instructions"], serde_json::json!(base_instructions),);
     assert_tool_names(&body1, &expected_tools_names);
 
     Ok(())

codex-rs/prompts/src/apply_patch.rs

@@ -1,3 +0,0 @@
-/// Detailed instructions for gpt-4.1 on how to use the `apply_patch` tool.
-pub const APPLY_PATCH_TOOL_INSTRUCTIONS: &str =
-    include_str!("../templates/apply_patch_tool_instructions.md");

codex-rs/prompts/src/lib.rs

@@ -1,4 +1,3 @@
-mod apply_patch;
 mod compact;
 mod goals;
 mod permissions_instructions;
@@ -6,7 +5,6 @@ mod realtime;
 mod review_exit;
 mod review_request;
 
-pub use apply_patch::APPLY_PATCH_TOOL_INSTRUCTIONS;
 pub use compact::SUMMARIZATION_PROMPT;
 pub use compact::SUMMARY_PREFIX;
 pub use goals::budget_limit_prompt;

codex-rs/prompts/templates/apply_patch_tool_instructions.md

@@ -1,75 +0,0 @@
-## `apply_patch`
-
-Use the `apply_patch` shell command to edit files.
-Your patch language is a stripped‑down, file‑oriented diff format designed to be easy to parse and safe to apply. You can think of it as a high‑level envelope:
-
-*** Begin Patch
-[ one or more file sections ]
-*** End Patch
-
-Within that envelope, you get a sequence of file operations.
-You MUST include a header to specify the action you are taking.
-Each operation starts with one of three headers:
-
-*** Add File: <path> - create a new file. Every following line is a + line (the initial contents).
-*** Delete File: <path> - remove an existing file. Nothing follows.
-*** Update File: <path> - patch an existing file in place (optionally with a rename).
-
-May be immediately followed by *** Move to: <new path> if you want to rename the file.
-Then one or more “hunks”, each introduced by @@ (optionally followed by a hunk header).
-Within a hunk each line starts with:
-
-For instructions on [context_before] and [context_after]:
-- By default, show 3 lines of code immediately above and 3 lines immediately below each change. If a change is within 3 lines of a previous change, do NOT duplicate the first change’s [context_after] lines in the second change’s [context_before] lines.
-- If 3 lines of context is insufficient to uniquely identify the snippet of code within the file, use the @@ operator to indicate the class or function to which the snippet belongs. For instance, we might have:
-@@ class BaseClass
-[3 lines of pre-context]
-- [old_code]
-+ [new_code]
-[3 lines of post-context]
-
-- If a code block is repeated so many times in a class or function such that even a single `@@` statement and 3 lines of context cannot uniquely identify the snippet of code, you can use multiple `@@` statements to jump to the right context. For instance:
-
-@@ class BaseClass
-@@ 	 def method():
-[3 lines of pre-context]
-- [old_code]
-+ [new_code]
-[3 lines of post-context]
-
-The full grammar definition is below:
-Patch := Begin { FileOp } End
-Begin := "*** Begin Patch" NEWLINE
-End := "*** End Patch" NEWLINE
-FileOp := AddFile | DeleteFile | UpdateFile
-AddFile := "*** Add File: " path NEWLINE { "+" line NEWLINE }
-DeleteFile := "*** Delete File: " path NEWLINE
-UpdateFile := "*** Update File: " path NEWLINE [ MoveTo ] { Hunk }
-MoveTo := "*** Move to: " newPath NEWLINE
-Hunk := "@@" [ header ] NEWLINE { HunkLine } [ "*** End of File" NEWLINE ]
-HunkLine := (" " | "-" | "+") text NEWLINE
-
-A full patch can combine several operations:
-
-*** Begin Patch
-*** Add File: hello.txt
-+Hello world
-*** Update File: src/app.py
-*** Move to: src/main.py
-@@ def greet():
--print("Hi")
-+print("Hello, world!")
-*** Delete File: obsolete.txt
-*** End Patch
-
-It is important to remember:
-
-- You must include a header with your intended action (Add/Delete/Update)
-- You must prefix new lines with `+` even when creating a new file
-- File references can only be relative, NEVER ABSOLUTE.
-
-You can invoke apply_patch like:
-
-```
-shell {"command":["apply_patch","*** Begin Patch\n*** Add File: hello.txt\n+Hello, world!\n*** End Patch\n"]}
-```