diff --git a/server/src/agent_log/format.rs b/server/src/agent_log/format.rs
index e38a46e4..1629b469 100644
--- a/server/src/agent_log/format.rs
+++ b/server/src/agent_log/format.rs
@@ -1,5 +1,7 @@
 //! Human-readable formatting of raw agent log entries.
 
+use crate::chat::util::truncate_at_char_boundary;
+
 /// Format a single log entry as a human-readable text line.
 ///
 /// `timestamp` is an ISO 8601 string; `event` is the flattened `AgentEvent`
@@ -7,6 +9,7 @@
 ///
 /// Returns `None` for entries that should be skipped (raw streaming noise,
 /// trivial status changes, empty output, etc.).
+#[allow(clippy::string_slice)] // timestamp[11..19]: ISO 8601 is ASCII-only, these byte offsets are always valid
 pub fn format_log_entry_as_text(timestamp: &str, event: &serde_json::Value) -> Option<String> {
     let agent_name = event
         .get("agent_name")
@@ -75,7 +78,7 @@ pub fn format_log_entry_as_text(timestamp: &str, event: &serde_json::Value) -> O
                                         .map(|v| serde_json::to_string(v).unwrap_or_default())
                                         .unwrap_or_default();
                                     let display = if input.len() > 200 {
-                                        format!("{}...", &input[..200])
+                                        format!("{}...", truncate_at_char_boundary(&input, 200))
                                     } else {
                                         input
                                     };
diff --git a/server/src/agent_mode/claim.rs b/server/src/agent_mode/claim.rs
index 3d50129b..c765f2a2 100644
--- a/server/src/agent_mode/claim.rs
+++ b/server/src/agent_mode/claim.rs
@@ -76,6 +76,7 @@ mod tests {
     /// AC: seed a stale claim older than the TTL, attempt a new claim from a
     /// different agent, assert the new claim succeeds and displacement is logged.
     #[test]
+    #[allow(clippy::string_slice)] // stale_holder is a hex/ASCII string literal; [..12] always valid
     fn stale_claim_displaced_and_logged() {
         use crate::crdt_state::{init_for_test, our_node_id, read_item, write_claim, write_item};
 
diff --git a/server/src/agent_mode/mod.rs b/server/src/agent_mode/mod.rs
index e0e005da..b8a52f06 100644
--- a/server/src/agent_mode/mod.rs
+++ b/server/src/agent_mode/mod.rs
@@ -48,6 +48,7 @@ use loop_ops::{
 ///
 /// If `join_token` and `gateway_url` are both provided the agent will register
 /// itself with the gateway on startup using the one-time token.
+#[allow(clippy::string_slice)] // node_id is a UUID (ASCII); min(8) clamps within its length
 pub async fn run(
     project_root: Option<PathBuf>,
     rendezvous_url: String,
diff --git a/server/src/agents/pool/pipeline/advance/mod.rs b/server/src/agents/pool/pipeline/advance/mod.rs
index 68765758..0368fccf 100644
--- a/server/src/agents/pool/pipeline/advance/mod.rs
+++ b/server/src/agents/pool/pipeline/advance/mod.rs
@@ -20,6 +20,7 @@ const MAX_GATE_OUTPUT_BYTES: usize = 8_000;
 
 /// Truncate gate output to [`MAX_GATE_OUTPUT_BYTES`], keeping the **tail**
 /// (where compiler errors and test failures are reported).
+#[allow(clippy::string_slice)] // adjusted is walked forward to a char boundary before slicing
 fn truncate_gate_output(output: &str) -> &str {
     if output.len() <= MAX_GATE_OUTPUT_BYTES {
         return output;
diff --git a/server/src/agents/pool/start/spawn.rs b/server/src/agents/pool/start/spawn.rs
index 91e17eb7..e53c683d 100644
--- a/server/src/agents/pool/start/spawn.rs
+++ b/server/src/agents/pool/start/spawn.rs
@@ -31,6 +31,7 @@ use super::super::types::StoryAgent;
 const GATE_OUTPUT_PROMPT_BYTES: usize = 3_000;
 
 /// Truncate `output` to at most [`GATE_OUTPUT_PROMPT_BYTES`], keeping the tail.
+#[allow(clippy::string_slice)] // adjusted is walked forward to a char boundary before slicing
 fn truncate_for_system_prompt(output: &str) -> &str {
     if output.len() <= GATE_OUTPUT_PROMPT_BYTES {
         return output;
diff --git a/server/src/chat/commands/cost.rs b/server/src/chat/commands/cost.rs
index b0416393..1e251efc 100644
--- a/server/src/chat/commands/cost.rs
+++ b/server/src/chat/commands/cost.rs
@@ -86,6 +86,7 @@ pub(super) fn handle_cost(ctx: &CommandContext) -> Option<String> {
 ///
 /// Agent names like "coder-1", "qa-2", "mergemaster" map to types "coder",
 /// "qa", "mergemaster". If the name ends with `-<digits>`, strip the suffix.
+#[allow(clippy::string_slice)] // pos comes from rfind('-'), so pos+1 is after an ASCII '-' → valid boundary
 pub(super) fn extract_agent_type(agent_name: &str) -> String {
     if let Some(pos) = agent_name.rfind('-') {
         let suffix = &agent_name[pos + 1..];
diff --git a/server/src/chat/commands/coverage.rs b/server/src/chat/commands/coverage.rs
index 93501e8b..3dc1cd4c 100644
--- a/server/src/chat/commands/coverage.rs
+++ b/server/src/chat/commands/coverage.rs
@@ -240,6 +240,7 @@ fn parse_coverage_output(output: &str, passed: bool) -> String {
 }
 
 /// Extract a value from lines like `"Rust line coverage: 62.5%"`.
+#[allow(clippy::string_slice)] // starts_with(prefix) guarantees prefix.len() is a char boundary
 fn extract_line_value(output: &str, prefix: &str) -> Option<String> {
     output
         .lines()
@@ -248,6 +249,7 @@ fn extract_line_value(output: &str, prefix: &str) -> Option<String> {
 }
 
 /// Extract a value from the summary block: `"  Overall:  62.5%"`.
+#[allow(clippy::string_slice)] // starts_with(label) guarantees label.len() is a char boundary
 fn extract_summary_field(output: &str, label: &str) -> Option<String> {
     output
         .lines()
diff --git a/server/src/chat/commands/diff.rs b/server/src/chat/commands/diff.rs
index e354023a..83009000 100644
--- a/server/src/chat/commands/diff.rs
+++ b/server/src/chat/commands/diff.rs
@@ -4,6 +4,7 @@
 //! HEAD, formatted for readability in chat.
 
 use super::CommandContext;
+use crate::chat::util::truncate_at_char_boundary;
 use std::path::Path;
 use std::process::Command;
 
@@ -125,18 +126,6 @@ fn run_git(dir: &Path, args: &[&str]) -> String {
         .unwrap_or_default()
 }
 
-/// Truncate `s` to at most `max_bytes` bytes without splitting a UTF-8 character.
-fn truncate_at_char_boundary(s: &str, max_bytes: usize) -> &str {
-    if s.len() <= max_bytes {
-        return s;
-    }
-    let mut boundary = max_bytes;
-    while !s.is_char_boundary(boundary) {
-        boundary -= 1;
-    }
-    &s[..boundary]
-}
-
 // ---------------------------------------------------------------------------
 // Tests
 // ---------------------------------------------------------------------------
diff --git a/server/src/chat/commands/git.rs b/server/src/chat/commands/git.rs
index 0d527a87..d5f5a03b 100644
--- a/server/src/chat/commands/git.rs
+++ b/server/src/chat/commands/git.rs
@@ -3,6 +3,7 @@
 use super::CommandContext;
 
 /// Show compact git status: branch, uncommitted files, ahead/behind remote.
+#[allow(clippy::string_slice)] // line[..2] and line[3..]: git porcelain XY status codes are always ASCII
 pub(super) fn handle_git(ctx: &CommandContext) -> Option<String> {
     use std::process::Command;
 
diff --git a/server/src/chat/commands/overview.rs b/server/src/chat/commands/overview.rs
index b673eaee..790cf80d 100644
--- a/server/src/chat/commands/overview.rs
+++ b/server/src/chat/commands/overview.rs
@@ -8,6 +8,7 @@ use super::CommandContext;
 /// git diff --stat (files changed with line counts), and extracts key
 /// function/struct/type names added or modified in the implementation.
 /// Returns a friendly message when no merge commit is found.
+#[allow(clippy::string_slice)] // commit_hash is hex (ASCII), min(8) always within bounds
 pub(super) fn handle_overview(ctx: &CommandContext) -> Option<String> {
     let num_str = ctx.args.trim();
     if num_str.is_empty() {
@@ -129,6 +130,7 @@ fn get_commit_stat(root: &std::path::Path, hash: &str) -> String {
 ///
 /// Scans added lines (`+`) for Rust `fn`, `struct`, `enum`, `type`, `trait`,
 /// and `impl` declarations and returns them formatted as `` `Name` (kind) ``.
+#[allow(clippy::string_slice)] // line starts with '+' (ASCII), so &line[1..] is always a valid boundary
 fn extract_diff_symbols(root: &std::path::Path, hash: &str) -> Vec<String> {
     use std::process::Command;
     let output = Command::new("git")
diff --git a/server/src/chat/commands/run_tests.rs b/server/src/chat/commands/run_tests.rs
index f9f22b8a..3d7606ce 100644
--- a/server/src/chat/commands/run_tests.rs
+++ b/server/src/chat/commands/run_tests.rs
@@ -123,6 +123,7 @@ fn parse_test_counts(output: &str) -> (u64, u64) {
     (total_passed, total_failed)
 }
 
+#[allow(clippy::string_slice)] // pos from line.find(label) → always a char boundary
 fn extract_count(line: &str, label: &str) -> Option<u64> {
     let pos = line.find(label)?;
     let before = line[..pos].trim_end();
diff --git a/server/src/chat/commands/show.rs b/server/src/chat/commands/show.rs
index 6c5d55ca..05b6d8b3 100644
--- a/server/src/chat/commands/show.rs
+++ b/server/src/chat/commands/show.rs
@@ -3,6 +3,7 @@
 use super::CommandContext;
 
 /// Strip YAML front matter and return a summary of useful fields + the remaining body.
+#[allow(clippy::string_slice)] // indices from find("\n---") on ASCII delimiter; "---" and "\n---" are ASCII-only
 fn strip_front_matter(text: &str) -> (String, String) {
     let trimmed = text.trim_start();
     if !trimmed.starts_with("---") {
diff --git a/server/src/chat/commands/status/tests.rs b/server/src/chat/commands/status/tests.rs
index ca7b28e3..366ca9c2 100644
--- a/server/src/chat/commands/status/tests.rs
+++ b/server/src/chat/commands/status/tests.rs
@@ -462,7 +462,7 @@ fn status_shows_crdt_done_story_in_done_not_backlog() {
     );
 
     // Verify it's not in Backlog section specifically.
-    let backlog_section = &output[backlog_pos..done_pos];
+    let backlog_section = output.get(backlog_pos..done_pos).unwrap_or("");
     assert!(
         !backlog_section.contains("503"),
         "503 must not appear in Backlog section: {backlog_section}"
@@ -573,10 +573,16 @@ fn merge_item_failure_snippet_truncated_at_120_chars() {
     );
     // The snippet should not exceed 120 chars plus the ellipsis character.
     let snippet_start = output.find("\u{26D4}").expect("stop sign must be present");
-    let line = output[snippet_start..].lines().next().unwrap_or("");
+    let line = output
+        .get(snippet_start..)
+        .unwrap_or("")
+        .lines()
+        .next()
+        .unwrap_or("");
     // Find the last " — " separator (before the snippet) and take what follows.
     if let Some(sep_pos) = line.rfind(" \u{2014} ") {
-        let snippet = &line[sep_pos + 5..]; // " — " is 5 bytes (space + 3-byte em dash + space)
+        // " — " is 5 bytes (space + 3-byte em dash + space)
+        let snippet = line.get(sep_pos + 5..).unwrap_or("");
         assert!(
             snippet.chars().count() <= 122, // 120 chars + "…" (1 char) + possible trailing
             "snippet should be at most ~121 chars: {snippet}"
diff --git a/server/src/chat/transport/discord/meta.rs b/server/src/chat/transport/discord/meta.rs
index fe0cd78d..db5a497d 100644
--- a/server/src/chat/transport/discord/meta.rs
+++ b/server/src/chat/transport/discord/meta.rs
@@ -3,7 +3,7 @@
 use async_trait::async_trait;
 use serde::Deserialize;
 
-use crate::chat::{ChatTransport, MessageId};
+use crate::chat::{ChatTransport, MessageId, util::truncate_at_char_boundary};
 use crate::slog;
 
 // ── Discord API base URL (overridable for tests) ──────────────────────
@@ -71,7 +71,7 @@ impl ChatTransport for DiscordTransport {
 
         // Discord messages have a 2000-char limit. Truncate if needed.
         let content = if plain.len() > 2000 {
-            format!("{}…", &plain[..1999])
+            format!("{}…", truncate_at_char_boundary(plain, 1999))
         } else {
             plain.to_string()
         };
@@ -118,7 +118,7 @@ impl ChatTransport for DiscordTransport {
         );
 
         let content = if plain.len() > 2000 {
-            format!("{}…", &plain[..1999])
+            format!("{}…", truncate_at_char_boundary(plain, 1999))
         } else {
             plain.to_string()
         };
diff --git a/server/src/chat/transport/matrix/bot/mentions.rs b/server/src/chat/transport/matrix/bot/mentions.rs
index 83839b88..21b217a7 100644
--- a/server/src/chat/transport/matrix/bot/mentions.rs
+++ b/server/src/chat/transport/matrix/bot/mentions.rs
@@ -37,6 +37,7 @@ pub fn mentions_bot(body: &str, formatted_body: Option<&str>, bot_user_id: &Owne
 }
 
 /// Returns `true` if `haystack` contains `needle` at a word boundary.
+#[allow(clippy::string_slice)] // all indices from find() or abs+needle.len() → always char boundaries
 pub(super) fn contains_word(haystack: &str, needle: &str) -> bool {
     let mut start = 0;
     while let Some(rel) = haystack[start..].find(needle) {
@@ -87,6 +88,7 @@ pub(super) async fn is_reply_to_bot(
 ///
 /// Used in ambient mode to suppress responses when a message is clearly
 /// directed at a different participant (e.g. another bot in the same room).
+#[allow(clippy::string_slice)] // word_end and colon_pos from find() → always char boundaries
 pub fn is_addressed_to_other(body: &str, bot_user_id: &OwnedUserId, bot_name: &str) -> bool {
     let trimmed = body.trim_start();
     let lower = trimmed.to_lowercase();
diff --git a/server/src/chat/transport/matrix/htop.rs b/server/src/chat/transport/matrix/htop.rs
index 1382bb3b..ef7ef89d 100644
--- a/server/src/chat/transport/matrix/htop.rs
+++ b/server/src/chat/transport/matrix/htop.rs
@@ -101,6 +101,7 @@ fn parse_duration(s: &str) -> Option<u64> {
 ///
 /// Returns a short string like `"load average: 1.23, 0.98, 0.75"` on success,
 /// or `"load: unknown"` on failure.
+#[allow(clippy::string_slice)] // idx comes from output.find("load average") → always a char boundary
 fn get_load_average() -> String {
     let output = std::process::Command::new("uptime")
         .output()
diff --git a/server/src/chat/transport/whatsapp/format.rs b/server/src/chat/transport/whatsapp/format.rs
index d62a83f5..6c220674 100644
--- a/server/src/chat/transport/whatsapp/format.rs
+++ b/server/src/chat/transport/whatsapp/format.rs
@@ -1,4 +1,5 @@
 //! WhatsApp message formatting — Markdown-to-WhatsApp conversion and message chunking.
+use crate::chat::util::truncate_at_char_boundary;
 use regex::Regex;
 use std::sync::LazyLock;
 
@@ -24,13 +25,13 @@ pub fn chunk_for_whatsapp(text: &str) -> Vec<String> {
         }
 
         // Find the best split point within the limit.
-        let window = &remaining[..WHATSAPP_MAX_MESSAGE_LEN];
+        let window = truncate_at_char_boundary(remaining, WHATSAPP_MAX_MESSAGE_LEN);
 
         // Prefer paragraph boundary.
         let split_pos = window
             .rfind("\n\n")
             .or_else(|| window.rfind('\n'))
-            .unwrap_or(WHATSAPP_MAX_MESSAGE_LEN);
+            .unwrap_or(window.len());
 
         let (chunk, rest) = remaining.split_at(split_pos);
         let chunk = chunk.trim();
diff --git a/server/src/chat/util.rs b/server/src/chat/util.rs
index 3d1ff245..73f5dd84 100644
--- a/server/src/chat/util.rs
+++ b/server/src/chat/util.rs
@@ -3,6 +3,23 @@
 //! These functions are transport-agnostic helpers for processing chat messages:
 //! prefix stripping, bot-mention handling, and paragraph buffering.
 
+/// Truncate `s` to at most `max_bytes` bytes without splitting a UTF-8 codepoint.
+///
+/// If `s.len() <= max_bytes` the original slice is returned unchanged.
+/// Otherwise the returned slice ends at the largest char boundary ≤ `max_bytes`,
+/// preventing any panic that would result from slicing mid-codepoint.
+pub fn truncate_at_char_boundary(s: &str, max_bytes: usize) -> &str {
+    if s.len() <= max_bytes {
+        return s;
+    }
+    let mut boundary = max_bytes;
+    while !s.is_char_boundary(boundary) {
+        boundary -= 1;
+    }
+    #[allow(clippy::string_slice)] // boundary is guaranteed to be a char boundary by the loop above
+    &s[..boundary]
+}
+
 /// Returns `true` if the message body is an affirmative permission response.
 ///
 /// Recognised affirmative tokens (case-insensitive): `yes`, `y`, `approve`,
@@ -26,6 +43,7 @@ pub fn is_permission_approval(body: &str) -> bool {
 
 /// Case-insensitive prefix strip that also requires the match to end at a
 /// word boundary (whitespace, punctuation, or end-of-string).
+#[allow(clippy::string_slice)] // prefix.len() is safe: `get(..prefix.len())` already validated the boundary
 pub fn strip_prefix_ci<'a>(text: &'a str, prefix: &str) -> Option<&'a str> {
     let candidate = text.get(..prefix.len())?;
     if !candidate.eq_ignore_ascii_case(prefix) {
@@ -50,6 +68,7 @@ pub fn strip_prefix_ci<'a>(text: &'a str, prefix: &str) -> Option<&'a str> {
 /// - `DisplayName, rest` → `rest`  (Element tab-completion may insert a comma)
 /// - `DisplayName ⚡️: rest` → `rest`  (display name with emoji)
 /// - `[DisplayName](https://matrix.to/#/@user:server) rest` → `rest`  (Element mention pill)
+#[allow(clippy::string_slice)] // all indices come from str::find / str::find_map → always char boundaries
 pub fn strip_bot_mention<'a>(message: &'a str, bot_name: &str, bot_user_id: &str) -> &'a str {
     let trimmed = message.trim();
 
@@ -98,6 +117,7 @@ pub fn strip_bot_mention<'a>(message: &'a str, bot_name: &str, bot_user_id: &str
 /// emoji from display names (e.g. `Timmy ⚡️`), and Element tab-completion
 /// separators (`:` or `,`).  This function skips all of that and returns a
 /// slice starting at the first ASCII alphanumeric character (the command).
+#[allow(clippy::string_slice)] // byte_skip comes from char_indices → guaranteed char boundary
 fn strip_mention_separator(rest: &str) -> &str {
     let byte_skip = rest
         .char_indices()
@@ -132,6 +152,7 @@ fn is_inside_code_fence(text: &str) -> bool {
 /// block (delimited by ` ``` ` lines) is **not** treated as a paragraph
 /// boundary.  This prevents a blank line inside a code block from splitting
 /// the fence across multiple messages, which would corrupt the rendering.
+#[allow(clippy::string_slice)] // abs_pos comes from str::find → always a char boundary
 pub fn drain_complete_paragraphs(buffer: &mut String) -> Vec<String> {
     let mut paragraphs = Vec::new();
     let mut search_from = 0;
@@ -259,6 +280,47 @@ pub fn normalize_line_breaks(text: &str) -> String {
 mod tests {
     use super::*;
 
+    // -- truncate_at_char_boundary ------------------------------------------
+
+    #[test]
+    fn truncate_ascii_within_limit() {
+        assert_eq!(truncate_at_char_boundary("hello", 10), "hello");
+    }
+
+    #[test]
+    fn truncate_ascii_at_exact_limit() {
+        assert_eq!(truncate_at_char_boundary("hello", 5), "hello");
+    }
+
+    #[test]
+    fn truncate_ascii_over_limit() {
+        assert_eq!(truncate_at_char_boundary("hello world", 5), "hello");
+    }
+
+    #[test]
+    fn truncate_multibyte_mid_codepoint_snaps_back() {
+        // "héllo": 'é' is U+00E9, 2 bytes. max_bytes=2 lands inside it → snap to 1.
+        let s = "héllo";
+        assert_eq!(truncate_at_char_boundary(s, 2), "h");
+    }
+
+    #[test]
+    fn truncate_multibyte_on_char_boundary() {
+        // "héllo": h(1) + é(2) = 3 bytes. max_bytes=3 is a valid boundary.
+        let s = "héllo";
+        assert_eq!(truncate_at_char_boundary(s, 3), "hé");
+    }
+
+    #[test]
+    fn truncate_max_bytes_zero_returns_empty() {
+        assert_eq!(truncate_at_char_boundary("hello", 0), "");
+    }
+
+    #[test]
+    fn truncate_max_bytes_greater_than_len() {
+        assert_eq!(truncate_at_char_boundary("hi", 100), "hi");
+    }
+
     // -- is_permission_approval ---------------------------------------------
 
     #[test]
diff --git a/server/src/cli.rs b/server/src/cli.rs
index 05d44e5e..2ee8604a 100644
--- a/server/src/cli.rs
+++ b/server/src/cli.rs
@@ -24,6 +24,7 @@ pub(crate) struct CliArgs {
 }
 
 /// Parse CLI arguments into `CliArgs`, or exit early for `--help` / `--version`.
+#[allow(clippy::string_slice)] // all slices use ASCII prefix lengths (e.g. "--port=".len()), always valid
 pub(crate) fn parse_cli_args(args: &[String]) -> Result<CliArgs, String> {
     let mut port: Option<u16> = None;
     let mut path: Option<String> = None;
diff --git a/server/src/crdt_state/state/init.rs b/server/src/crdt_state/state/init.rs
index 87430306..c91cfcfa 100644
--- a/server/src/crdt_state/state/init.rs
+++ b/server/src/crdt_state/state/init.rs
@@ -34,6 +34,7 @@ use crate::slog;
 /// Opens the SQLite database, loads or creates a node keypair, replays any
 /// persisted ops to reconstruct state, and spawns a background persistence
 /// task.  Safe to call only once; subsequent calls are no-ops.
+#[allow(clippy::string_slice)] // op_id is hex::encode output (ASCII-only), &op_id[..12] is always valid
 pub async fn init(db_path: &Path) -> Result<(), sqlx::Error> {
     if CRDT_STATE.get().is_some() {
         return Ok(());
diff --git a/server/src/crdt_state/write/migrations.rs b/server/src/crdt_state/write/migrations.rs
index 6c4d9b2c..7bcd6f14 100644
--- a/server/src/crdt_state/write/migrations.rs
+++ b/server/src/crdt_state/write/migrations.rs
@@ -49,6 +49,7 @@ pub fn name_from_story_id(story_id: &str) -> String {
 ///
 /// Returns `Some("664")` for `"664_story_my_feature"`, and `None` for IDs
 /// that are already numeric-only (`"664"`) or have no valid numeric prefix.
+#[allow(clippy::string_slice)] // idx comes from find('_') → always a char boundary
 pub(super) fn numeric_id_from_slug(story_id: &str) -> Option<String> {
     // Already numeric-only — no migration needed.
     if story_id.chars().all(|c: char| c.is_ascii_digit()) {
diff --git a/server/src/http/gateway/mcp.rs b/server/src/http/gateway/mcp.rs
index a6f154d0..dce5b9b7 100644
--- a/server/src/http/gateway/mcp.rs
+++ b/server/src/http/gateway/mcp.rs
@@ -225,6 +225,7 @@ async fn proxy_and_respond(state: &GatewayState, bytes: &[u8], id: Option<Value>
 ///
 /// On sled disconnect mid-stream a JSON-RPC error event is emitted so the
 /// client does not hang forever.
+#[allow(clippy::string_slice)] // pos from buf.find('\n'); '\n' is ASCII so pos and pos+1 are valid boundaries
 async fn proxy_and_respond_sse(state: &GatewayState, bytes: &[u8], id: Option<Value>) -> Response {
     let url = match state.active_url().await {
         Ok(u) => u,
diff --git a/server/src/http/workflow/bug_ops/bug.rs b/server/src/http/workflow/bug_ops/bug.rs
index a3000d1d..d7179e67 100644
--- a/server/src/http/workflow/bug_ops/bug.rs
+++ b/server/src/http/workflow/bug_ops/bug.rs
@@ -90,6 +90,7 @@ pub(super) fn is_bug_item(stem: &str) -> bool {
 }
 
 /// Extract bug name from content (heading or front matter).
+#[allow(clippy::string_slice)] // colon_pos from find(": "); +2 skips ASCII ": " → valid boundary
 pub(super) fn extract_bug_name_from_content(content: &str) -> Option<String> {
     // Try front matter first.
     if let Ok(meta) = parse_front_matter(content)
diff --git a/server/src/http/workflow/story_ops/criterion.rs b/server/src/http/workflow/story_ops/criterion.rs
index 8a93cd29..d0c6b787 100644
--- a/server/src/http/workflow/story_ops/criterion.rs
+++ b/server/src/http/workflow/story_ops/criterion.rs
@@ -9,6 +9,7 @@ use super::super::{
 };
 
 /// Toggle an acceptance criterion checkbox (`- [ ]` → `- [x]`) by its 0-based index among unchecked items.
+#[allow(clippy::string_slice)] // indent_len = line.len() - trimmed.len(); trim() returns a sub-slice → valid boundary
 pub fn check_criterion_in_file(
     project_root: &Path,
     story_id: &str,
@@ -107,6 +108,7 @@ pub fn remove_criterion_from_file(
 ///
 /// Finds the criterion at `criterion_index` (0-based, counting all criteria regardless
 /// of checked state) and replaces its text with `new_text`.
+#[allow(clippy::string_slice)] // indent_len = line.len() - trimmed.len(); trim() returns a sub-slice → valid boundary
 pub fn edit_criterion_in_file(
     project_root: &Path,
     story_id: &str,
diff --git a/server/src/http/workflow/test_results.rs b/server/src/http/workflow/test_results.rs
index 2c874a7f..2fc88b7d 100644
--- a/server/src/http/workflow/test_results.rs
+++ b/server/src/http/workflow/test_results.rs
@@ -124,6 +124,7 @@ fn format_test_line(t: &TestCaseResult) -> String {
 }
 
 /// Parse `StoryTestResults` from the JSON embedded in the `## Test Results` section.
+#[allow(clippy::string_slice)] // json_end from rfind("-->") → always a char boundary
 fn parse_test_results_from_contents(contents: &str) -> Option<StoryTestResults> {
     for line in contents.lines() {
         let trimmed = line.trim();
diff --git a/server/src/llm/oauth.rs b/server/src/llm/oauth.rs
index 76ec4ee5..370ff9f2 100644
--- a/server/src/llm/oauth.rs
+++ b/server/src/llm/oauth.rs
@@ -409,6 +409,7 @@ pub async fn swap_to_next_available_account(
 ///
 /// Returns the URL portion when the error indicates missing or expired credentials,
 /// `None` otherwise.
+#[allow(clippy::string_slice)] // start + marker.len() is after the ASCII marker found by find() → valid boundary
 pub fn extract_login_url_from_error(err: &str) -> Option<&str> {
     let marker = "Please log in: ";
     let start = err.find(marker)?;
diff --git a/server/src/llm/providers/claude_code/mod.rs b/server/src/llm/providers/claude_code/mod.rs
index 598edae9..e3af11d9 100644
--- a/server/src/llm/providers/claude_code/mod.rs
+++ b/server/src/llm/providers/claude_code/mod.rs
@@ -182,6 +182,7 @@ impl ClaudeCodeProvider {
 /// via `--permission-prompt-tool`. Claude Code calls the MCP tool when it
 /// needs user approval, and the server bridges the request to the frontend.
 #[allow(clippy::too_many_arguments)]
+#[allow(clippy::string_slice)] // end is walked to a char boundary before slicing &trimmed[..end]
 fn run_pty_session(
     user_message: &str,
     cwd: &str,
diff --git a/server/src/llm/providers/ollama.rs b/server/src/llm/providers/ollama.rs
index 77715a82..a363a8f5 100644
--- a/server/src/llm/providers/ollama.rs
+++ b/server/src/llm/providers/ollama.rs
@@ -43,6 +43,7 @@ impl OllamaProvider {
     }
 
     /// Streaming chat that calls `on_token` for each token chunk.
+    #[allow(clippy::string_slice)] // newline_pos from find('\n'); '\n' is ASCII so pos and pos+1 are valid
     pub async fn chat_stream<F>(
         &self,
         model: &str,
diff --git a/server/src/main.rs b/server/src/main.rs
index 5c4f2c75..20f7e11d 100644
--- a/server/src/main.rs
+++ b/server/src/main.rs
@@ -3,6 +3,8 @@
 // matrix-sdk-crypto's deeply nested types require a higher recursion limit
 // when the `e2e-encryption` feature is enabled.
 #![recursion_limit = "256"]
+// Prevent panics from direct &str indexing that could split multi-byte UTF-8 codepoints.
+#![deny(clippy::string_slice)]
 
 mod agent_log;
 mod agent_mode;
diff --git a/server/src/node_identity.rs b/server/src/node_identity.rs
index 4868f086..e81f6c9e 100644
--- a/server/src/node_identity.rs
+++ b/server/src/node_identity.rs
@@ -248,6 +248,7 @@ fn hex_encode(bytes: &[u8]) -> String {
     bytes.iter().map(|b| format!("{b:02x}")).collect()
 }
 
+#[allow(clippy::string_slice)] // s is hex (ASCII-only); i advances in steps of 2, always within bounds
 fn hex_decode(s: &str) -> Option<Vec<u8>> {
     if !s.len().is_multiple_of(2) {
         return None;
@@ -330,6 +331,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(clippy::string_slice)] // sig is hex (ASCII-only); subtracting 4 stays within bounds for any valid sig
     fn verify_rejects_truncated_signature() {
         let kp = make_keypair();
         let pubkey = public_key_hex(&kp);
diff --git a/server/src/service/git_ops/porcelain.rs b/server/src/service/git_ops/porcelain.rs
index 3038481b..7c544147 100644
--- a/server/src/service/git_ops/porcelain.rs
+++ b/server/src/service/git_ops/porcelain.rs
@@ -7,6 +7,7 @@
 ///
 /// Returns `(staged, unstaged, untracked)` where each entry is the file path
 /// string from the porcelain line.
+#[allow(clippy::string_slice)] // line[3..]: git porcelain format has 2 ASCII status chars + ASCII space
 pub fn parse_git_status_porcelain(stdout: &str) -> (Vec<String>, Vec<String>, Vec<String>) {
     let mut staged: Vec<String> = Vec::new();
     let mut unstaged: Vec<String> = Vec::new();
diff --git a/server/src/service/oauth/io.rs b/server/src/service/oauth/io.rs
index 745083ab..26268fb6 100644
--- a/server/src/service/oauth/io.rs
+++ b/server/src/service/oauth/io.rs
@@ -109,10 +109,11 @@ pub(super) fn save_credentials(
 
     // Build the pool key: prefer email, fall back to token prefix.
     let key = if email.is_empty() {
-        format!(
-            "account-{}",
-            &token.access_token[..token.access_token.len().min(16)]
-        )
+        let prefix = token
+            .access_token
+            .get(..token.access_token.len().min(16))
+            .unwrap_or(&token.access_token);
+        format!("account-{prefix}")
     } else {
         email.to_string()
     };
diff --git a/server/src/service/shell/path_guard.rs b/server/src/service/shell/path_guard.rs
index 33cdc596..af1912c3 100644
--- a/server/src/service/shell/path_guard.rs
+++ b/server/src/service/shell/path_guard.rs
@@ -88,6 +88,7 @@ pub fn parse_test_counts(output: &str) -> (u64, u64) {
 ///
 /// For example, `extract_count("5 passed; 0 failed", "passed")` returns
 /// `Some(5)`. Returns `None` if no digit sequence precedes `label`.
+#[allow(clippy::string_slice)] // pos from line.find(label) → always a char boundary
 pub fn extract_count(line: &str, label: &str) -> Option<u64> {
     let pos = line.find(label)?;
     let before = line[..pos].trim_end();