diff --git a/src/services/mcp/auth.ts b/src/services/mcp/auth.ts
index ffc1870..5edd215 100644
--- a/src/services/mcp/auth.ts
+++ b/src/services/mcp/auth.ts
@@ -118,6 +118,54 @@ function summarizeHeadersForDebug(
   }
 }
 
+function extractHttpStatusFromErrorMessage(message: string): number | undefined {
+  const statusMatch = message.match(/^HTTP (\d{3}):/)
+  if (!statusMatch) {
+    return undefined
+  }
+  return Number(statusMatch[1])
+}
+
+function summarizeOAuthErrorForDebug(error: unknown): string {
+  const summary: Record<string, boolean | number | string> = {}
+
+  if (error instanceof Error) {
+    summary.errorType = error.constructor.name
+    summary.errorName = error.name
+    summary.hasMessage = error.message.length > 0
+
+    const httpStatus = extractHttpStatusFromErrorMessage(error.message)
+    if (httpStatus !== undefined) {
+      summary.httpStatus = httpStatus
+    }
+
+    if (error instanceof OAuthError) {
+      summary.oauthErrorCode = error.errorCode
+    }
+  } else {
+    summary.errorType = typeof error
+    summary.hasValue = error !== undefined && error !== null
+  }
+
+  const errno = getErrnoCode(error)
+  if (errno) {
+    summary.errno = errno
+  }
+
+  if (axios.isAxiosError(error)) {
+    summary.errorType = 'AxiosError'
+    if (error.code) {
+      summary.axiosCode = error.code
+    }
+    if (typeof error.response?.status === 'number') {
+      summary.httpStatus = error.response.status
+    }
+    summary.hasResponseData = error.response?.data !== undefined
+  }
+
+  return jsonStringify(summary)
+}
+
 /**
  * Some OAuth servers (notably Slack) return HTTP 200 for all responses,
  * signaling errors via the JSON body instead. The SDK's executeTokenRequest
@@ -289,7 +337,9 @@ async function fetchAuthServerMetadata(
     // to the legacy path-aware retry.
     logMCPDebug(
       serverName,
-      `RFC 9728 discovery failed, falling back: ${errorMessage(err)}`,
+      `RFC 9728 discovery failed, falling back: ${summarizeOAuthErrorForDebug(
+        err,
+      )}`,
     )
   }
 
@@ -511,7 +561,7 @@ export async function revokeServerTokens(
               : 'client_secret_basic'
           logMCPDebug(
             serverName,
-            `Revoking tokens via ${revocationEndpointStr} (${authMethod})`,
+            `Revoking tokens via discovered OAuth revocation endpoint (${authMethod})`,
           )
 
           // Revoke refresh token first (more important - prevents future access token generation)
@@ -531,7 +581,9 @@ export async function revokeServerTokens(
               // Log but continue
               logMCPDebug(
                 serverName,
-                `Failed to revoke refresh token: ${errorMessage(error)}`,
+                `Failed to revoke refresh token: ${summarizeOAuthErrorForDebug(
+                  error,
+                )}`,
               )
             }
           }
@@ -552,7 +604,9 @@ export async function revokeServerTokens(
             } catch (error: unknown) {
               logMCPDebug(
                 serverName,
-                `Failed to revoke access token: ${errorMessage(error)}`,
+                `Failed to revoke access token: ${summarizeOAuthErrorForDebug(
+                  error,
+                )}`,
               )
             }
           }
@@ -560,7 +614,10 @@ export async function revokeServerTokens(
       }
     } catch (error: unknown) {
       // Log error but don't throw - revocation is best-effort
-      logMCPDebug(serverName, `Failed to revoke tokens: ${errorMessage(error)}`)
+      logMCPDebug(
+        serverName,
+        `Failed to revoke tokens: ${summarizeOAuthErrorForDebug(error)}`,
+      )
     }
   } else {
     logMCPDebug(serverName, 'No tokens to revoke')
@@ -914,10 +971,7 @@ export async function performMCPOAuthFlow(
     try {
       resourceMetadataUrl = new URL(cachedResourceMetadataUrl)
     } catch {
-      logMCPDebug(
-        serverName,
-        `Invalid cached resourceMetadataUrl: ${cachedResourceMetadataUrl}`,
-      )
+      logMCPDebug(serverName, 'Invalid cached resource metadata URL')
     }
   }
   const wwwAuthParams: WWWAuthenticateParams = {
@@ -987,7 +1041,7 @@ export async function performMCPOAuthFlow(
     } catch (error) {
       logMCPDebug(
         serverName,
-        `Failed to fetch OAuth metadata: ${errorMessage(error)}`,
+        `Failed to fetch OAuth metadata: ${summarizeOAuthErrorForDebug(error)}`,
       )
     }
 
@@ -1184,7 +1238,10 @@ export async function performMCPOAuthFlow(
             )
           }
         } catch (error) {
-          logMCPDebug(serverName, `SDK auth error: ${errorMessage(error)}`)
+          logMCPDebug(
+            serverName,
+            `SDK auth error: ${summarizeOAuthErrorForDebug(error)}`,
+          )
           cleanup()
           rejectOnce(new Error(`SDK auth failed: ${errorMessage(error)}`))
         }
@@ -1258,7 +1315,7 @@ export async function performMCPOAuthFlow(
   } catch (error) {
     logMCPDebug(
       serverName,
-      `Error during auth completion: ${errorMessage(error)}`,
+      `Error during auth completion: ${summarizeOAuthErrorForDebug(error)}`,
     )
 
     // Determine failure reason for attribution telemetry. The try block covers
@@ -1300,9 +1357,9 @@ export async function performMCPOAuthFlow(
       // SDK does not attach HTTP status as a property, but the fallback ServerError
       // embeds it in the message as "HTTP {status}:" when the response body was
       // unparseable. Best-effort extraction.
-      const statusMatch = error.message.match(/^HTTP (\d{3}):/)
-      if (statusMatch) {
-        httpStatus = Number(statusMatch[1])
+      const parsedStatus = extractHttpStatusFromErrorMessage(error.message)
+      if (parsedStatus !== undefined) {
+        httpStatus = parsedStatus
       }
       // If client not found, clear the stored client ID and suggest retry
       if (
@@ -1608,7 +1665,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
       } catch (e) {
         logMCPDebug(
           this.serverName,
-          `XAA silent exchange failed: ${errorMessage(e)}`,
+          `XAA silent exchange failed: ${summarizeOAuthErrorForDebug(e)}`,
         )
       }
       // Fall through. Either id_token isn't cached (xaaRefresh returned
@@ -1681,7 +1738,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
       } catch (error) {
         logMCPDebug(
           this.serverName,
-          `Token refresh error: ${errorMessage(error)}`,
+          `Token refresh error: ${summarizeOAuthErrorForDebug(error)}`,
         )
       }
     }
@@ -1796,7 +1853,9 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
     } catch (e) {
       logMCPDebug(
         this.serverName,
-        `XAA: OIDC discovery failed in silent refresh: ${errorMessage(e)}`,
+        `XAA: OIDC discovery failed in silent refresh: ${summarizeOAuthErrorForDebug(
+          e,
+        )}`,
       )
       return undefined
     }
@@ -2055,7 +2114,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
     if (metadataUrl) {
       logMCPDebug(
         this.serverName,
-        `Fetching metadata from configured URL: ${metadataUrl}`,
+        'Fetching metadata from configured override URL',
       )
       try {
         const metadata = await fetchAuthServerMetadata(
@@ -2073,7 +2132,9 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
       } catch (error) {
         logMCPDebug(
           this.serverName,
-          `Failed to fetch from configured metadata URL: ${errorMessage(error)}`,
+          `Failed to fetch from configured metadata URL: ${summarizeOAuthErrorForDebug(
+            error,
+          )}`,
         )
       }
     }
@@ -2225,7 +2286,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
           } else if (cached?.authorizationServerUrl) {
             logMCPDebug(
               this.serverName,
-              `Re-discovering metadata from persisted auth server URL: ${cached.authorizationServerUrl}`,
+              'Re-discovering metadata from persisted auth server URL',
             )
             metadata = await discoverAuthorizationServerMetadata(
               cached.authorizationServerUrl,
@@ -2281,10 +2342,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
         // Invalid grant means the refresh token itself is invalid/revoked/expired.
         // But another process may have already refreshed successfully — check first.
         if (error instanceof InvalidGrantError) {
-          logMCPDebug(
-            this.serverName,
-            `Token refresh failed with invalid_grant: ${error.message}`,
-          )
+          logMCPDebug(this.serverName, 'Token refresh failed with invalid_grant')
           clearKeychainCache()
           const storage = getSecureStorage()
           const data = storage.read()
@@ -2331,7 +2389,7 @@ export class ClaudeAuthProvider implements OAuthClientProvider {
         if (!isRetryable || attempt >= MAX_ATTEMPTS) {
           logMCPDebug(
             this.serverName,
-            `Token refresh failed: ${errorMessage(error)}`,
+            `Token refresh failed: ${summarizeOAuthErrorForDebug(error)}`,
           )
           emitRefreshEvent(
             'failure',
diff --git a/src/services/mcp/client.ts b/src/services/mcp/client.ts
index 306be0a..2f41227 100644
--- a/src/services/mcp/client.ts
+++ b/src/services/mcp/client.ts
@@ -377,6 +377,49 @@ function summarizeStderrForDebug(stderrOutput: string): string {
   return `Server stderr captured (${trimmed.length} chars, ${lineCount} lines)`
 }
 
+function summarizeMcpErrorForDebug(error: unknown): string {
+  const summary: Record<string, boolean | number | string> = {}
+
+  if (error instanceof Error) {
+    summary.errorType = error.constructor.name
+    summary.errorName = error.name
+    summary.hasMessage = error.message.length > 0
+    summary.hasStack = Boolean(error.stack)
+
+    const errorObj = error as Error & {
+      code?: unknown
+      errno?: unknown
+      syscall?: unknown
+      status?: unknown
+      cause?: unknown
+    }
+
+    if (typeof errorObj.code === 'string' || typeof errorObj.code === 'number') {
+      summary.code = errorObj.code
+    }
+    if (
+      typeof errorObj.errno === 'string' ||
+      typeof errorObj.errno === 'number'
+    ) {
+      summary.errno = errorObj.errno
+    }
+    if (typeof errorObj.syscall === 'string') {
+      summary.syscall = errorObj.syscall
+    }
+    if (typeof errorObj.status === 'number') {
+      summary.status = errorObj.status
+    }
+    if (errorObj.cause !== undefined) {
+      summary.hasCause = true
+    }
+  } else {
+    summary.errorType = typeof error
+    summary.hasValue = error !== undefined && error !== null
+  }
+
+  return jsonStringify(summary)
+}
+
 /**
  * Shared handler for sse/http/claudeai-proxy auth failures during connect:
  * emits tengu_mcp_server_needs_auth, caches the needs-auth entry, and returns
@@ -1077,20 +1120,22 @@ export const connectToServer = memoize(
         )
         try {
           const testUrl = new URL(serverRef.url)
-          logMCPDebug(
-            name,
-            `Parsed URL: host=${testUrl.hostname}, port=${testUrl.port || 'default'}, protocol=${testUrl.protocol}`,
-          )
+          logMCPDebug(name, 'Parsed HTTP endpoint for preflight checks')
 
           // Log DNS resolution attempt
           if (
             testUrl.hostname === '127.0.0.1' ||
             testUrl.hostname === 'localhost'
           ) {
-            logMCPDebug(name, `Using loopback address: ${testUrl.hostname}`)
+            logMCPDebug(name, 'Using loopback HTTP endpoint')
           }
         } catch (urlError) {
-          logMCPDebug(name, `Failed to parse URL: ${urlError}`)
+          logMCPDebug(
+            name,
+            `Failed to parse HTTP endpoint for preflight: ${summarizeMcpErrorForDebug(
+              urlError,
+            )}`,
+          )
         }
       }
 
@@ -1142,30 +1187,29 @@ export const connectToServer = memoize(
         if (serverRef.type === 'sse' && error instanceof Error) {
           logMCPDebug(
             name,
-            `SSE Connection failed after ${elapsed}ms: ${jsonStringify({
-              url: serverRef.url,
-              error: error.message,
-              errorType: error.constructor.name,
-              stack: error.stack,
-            })}`,
+            `SSE connection failed after ${elapsed}ms: ${summarizeMcpErrorForDebug(
+              error,
+            )}`,
+          )
+          logMCPError(
+            name,
+            `SSE connection failed: ${summarizeMcpErrorForDebug(error)}`,
           )
-          logMCPError(name, error)
 
           if (error instanceof UnauthorizedError) {
             return handleRemoteAuthFailure(name, serverRef, 'sse')
           }
         } else if (serverRef.type === 'http' && error instanceof Error) {
-          const errorObj = error as Error & {
-            cause?: unknown
-            code?: string
-            errno?: string | number
-            syscall?: string
-          }
           logMCPDebug(
             name,
-            `HTTP Connection failed after ${elapsed}ms: ${error.message} (code: ${errorObj.code || 'none'}, errno: ${errorObj.errno || 'none'})`,
+            `HTTP connection failed after ${elapsed}ms: ${summarizeMcpErrorForDebug(
+              error,
+            )}`,
+          )
+          logMCPError(
+            name,
+            `HTTP connection failed: ${summarizeMcpErrorForDebug(error)}`,
           )
-          logMCPError(name, error)
 
           if (error instanceof UnauthorizedError) {
             return handleRemoteAuthFailure(name, serverRef, 'http')
@@ -1176,9 +1220,16 @@ export const connectToServer = memoize(
         ) {
           logMCPDebug(
             name,
-            `claude.ai proxy connection failed after ${elapsed}ms: ${error.message}`,
+            `claude.ai proxy connection failed after ${elapsed}ms: ${summarizeMcpErrorForDebug(
+              error,
+            )}`,
+          )
+          logMCPError(
+            name,
+            `claude.ai proxy connection failed: ${summarizeMcpErrorForDebug(
+              error,
+            )}`,
           )
-          logMCPError(name, error)
 
           // StreamableHTTPError has a `code` property with the HTTP status
           const errorCode = (error as Error & { code?: number }).code
@@ -1257,7 +1308,9 @@ export const connectToServer = memoize(
         } catch (error) {
           logMCPError(
             name,
-            `Failed to send ide_connected notification: ${error}`,
+            `Failed to send ide_connected notification: ${summarizeMcpErrorForDebug(
+              error,
+            )}`,
           )
         }
       }
@@ -1291,7 +1344,10 @@ export const connectToServer = memoize(
         hasTriggeredClose = true
         logMCPDebug(name, `Closing transport (${reason})`)
         void client.close().catch(e => {
-          logMCPDebug(name, `Error during close: ${errorMessage(e)}`)
+          logMCPDebug(
+            name,
+            `Error during close: ${summarizeMcpErrorForDebug(e)}`,
+          )
         })
       }
 
@@ -1355,7 +1411,10 @@ export const connectToServer = memoize(
               `Failed to spawn process - check command and permissions`,
             )
           } else {
-            logMCPDebug(name, `Connection error: ${error.message}`)
+            logMCPDebug(
+              name,
+              `Connection error: ${summarizeMcpErrorForDebug(error)}`,
+            )
           }
         }
 
@@ -1456,12 +1515,20 @@ export const connectToServer = memoize(
           try {
             await inProcessServer.close()
           } catch (error) {
-            logMCPDebug(name, `Error closing in-process server: ${error}`)
+            logMCPDebug(
+              name,
+              `Error closing in-process server: ${summarizeMcpErrorForDebug(
+                error,
+              )}`,
+            )
           }
           try {
             await client.close()
           } catch (error) {
-            logMCPDebug(name, `Error closing client: ${error}`)
+            logMCPDebug(
+              name,
+              `Error closing client: ${summarizeMcpErrorForDebug(error)}`,
+            )
           }
           return
         }
@@ -1487,7 +1554,10 @@ export const connectToServer = memoize(
               try {
                 process.kill(childPid, 'SIGINT')
               } catch (error) {
-                logMCPDebug(name, `Error sending SIGINT: ${error}`)
+                logMCPDebug(
+                  name,
+                  `Error sending SIGINT: ${summarizeMcpErrorForDebug(error)}`,
+                )
                 return
               }
 
@@ -1541,7 +1611,12 @@ export const connectToServer = memoize(
                       try {
                         process.kill(childPid, 'SIGTERM')
                       } catch (termError) {
-                        logMCPDebug(name, `Error sending SIGTERM: ${termError}`)
+                        logMCPDebug(
+                          name,
+                          `Error sending SIGTERM: ${summarizeMcpErrorForDebug(
+                            termError,
+                          )}`,
+                        )
                         resolved = true
                         clearInterval(checkInterval)
                         clearTimeout(failsafeTimeout)
@@ -1574,7 +1649,9 @@ export const connectToServer = memoize(
                         } catch (killError) {
                           logMCPDebug(
                             name,
-                            `Error sending SIGKILL: ${killError}`,
+                            `Error sending SIGKILL: ${summarizeMcpErrorForDebug(
+                              killError,
+                            )}`,
                           )
                         }
                       } catch {
@@ -1606,7 +1683,12 @@ export const connectToServer = memoize(
               })
             }
           } catch (processError) {
-            logMCPDebug(name, `Error terminating process: ${processError}`)
+            logMCPDebug(
+              name,
+              `Error terminating process: ${summarizeMcpErrorForDebug(
+                processError,
+              )}`,
+            )
           }
         }
 
@@ -1614,7 +1696,10 @@ export const connectToServer = memoize(
         try {
           await client.close()
         } catch (error) {
-          logMCPDebug(name, `Error closing client: ${error}`)
+          logMCPDebug(
+            name,
+            `Error closing client: ${summarizeMcpErrorForDebug(error)}`,
+          )
         }
       }
 
@@ -1671,9 +1756,14 @@ export const connectToServer = memoize(
       })
       logMCPDebug(
         name,
-        `Connection failed after ${connectionDurationMs}ms: ${errorMessage(error)}`,
+        `Connection failed after ${connectionDurationMs}ms: ${summarizeMcpErrorForDebug(
+          error,
+        )}`,
+      )
+      logMCPError(
+        name,
+        `Connection failed: ${summarizeMcpErrorForDebug(error)}`,
       )
-      logMCPError(name, `Connection failed: ${errorMessage(error)}`)
 
       if (inProcessServer) {
         inProcessServer.close().catch(() => {})
@@ -2038,7 +2128,10 @@ export const fetchToolsForClient = memoizeWithLRU(
         })
         .filter(isIncludedMcpTool)
     } catch (error) {
-      logMCPError(client.name, `Failed to fetch tools: ${errorMessage(error)}`)
+      logMCPError(
+        client.name,
+        `Failed to fetch tools: ${summarizeMcpErrorForDebug(error)}`,
+      )
       return []
     }
   },
@@ -2070,7 +2163,7 @@ export const fetchResourcesForClient = memoizeWithLRU(
     } catch (error) {
       logMCPError(
         client.name,
-        `Failed to fetch resources: ${errorMessage(error)}`,
+        `Failed to fetch resources: ${summarizeMcpErrorForDebug(error)}`,
       )
       return []
     }
@@ -2136,7 +2229,9 @@ export const fetchCommandsForClient = memoizeWithLRU(
             } catch (error) {
               logMCPError(
                 client.name,
-                `Error running command '${prompt.name}': ${errorMessage(error)}`,
+                `Error running command '${prompt.name}': ${summarizeMcpErrorForDebug(
+                  error,
+                )}`,
               )
               throw error
             }
@@ -2146,7 +2241,7 @@ export const fetchCommandsForClient = memoizeWithLRU(
     } catch (error) {
       logMCPError(
         client.name,
-        `Failed to fetch commands: ${errorMessage(error)}`,
+        `Failed to fetch commands: ${summarizeMcpErrorForDebug(error)}`,
       )
       return []
     }
@@ -2247,7 +2342,10 @@ export async function reconnectMcpServerImpl(
     }
   } catch (error) {
     // Handle errors gracefully - connection might have closed during fetch
-    logMCPError(name, `Error during reconnection: ${errorMessage(error)}`)
+    logMCPError(
+      name,
+      `Error during reconnection: ${summarizeMcpErrorForDebug(error)}`,
+    )
 
     // Return with failed status
     return {
@@ -2422,7 +2520,9 @@ export async function getMcpToolsCommandsAndResources(
       // Handle errors gracefully - connection might have closed during fetch
       logMCPError(
         name,
-        `Error fetching tools/commands/resources: ${errorMessage(error)}`,
+        `Error fetching tools/commands/resources: ${summarizeMcpErrorForDebug(
+          error,
+        )}`,
       )
 
       // Still update with the client but no tools/commands
@@ -2509,7 +2609,7 @@ export function prefetchAllMcpResources(
     }, mcpConfigs).catch(error => {
       logMCPError(
         'prefetchAllMcpResources',
-        `Failed to get MCP resources: ${errorMessage(error)}`,
+        `Failed to get MCP resources: ${summarizeMcpErrorForDebug(error)}`,
       )
       // Still resolve with empty results
       void resolve({
@@ -3371,7 +3471,12 @@ export async function setupSdkMcpClients(
         }
       } catch (error) {
         // If connection fails, return failed server
-        logMCPError(name, `Failed to connect SDK MCP server: ${error}`)
+        logMCPError(
+          name,
+          `Failed to connect SDK MCP server: ${summarizeMcpErrorForDebug(
+            error,
+          )}`,
+        )
         return {
           client: {
             type: 'failed' as const,
diff --git a/src/services/mcp/config.ts b/src/services/mcp/config.ts
index c5cee9c..c3c8e8d 100644
--- a/src/services/mcp/config.ts
+++ b/src/services/mcp/config.ts
@@ -1397,6 +1397,7 @@ export function parseMcpConfigFromFilePath(params: {
     configContent = fs.readFileSync(filePath, { encoding: 'utf8' })
   } catch (error: unknown) {
     const code = getErrnoCode(error)
+    const fileName = parse(filePath).base
     if (code === 'ENOENT') {
       return {
         config: null,
@@ -1415,7 +1416,7 @@ export function parseMcpConfigFromFilePath(params: {
       }
     }
     logForDebugging(
-      `MCP config read error for ${filePath} (scope=${scope}): ${error}`,
+      `MCP config read error (scope=${scope}, file=${fileName}, errno=${code ?? 'none'}, errorType=${error instanceof Error ? error.name : typeof error})`,
       { level: 'error' },
     )
     return {
@@ -1439,7 +1440,7 @@ export function parseMcpConfigFromFilePath(params: {
 
   if (!parsedJson) {
     logForDebugging(
-      `MCP config is not valid JSON: ${filePath} (scope=${scope}, length=${configContent.length}, first100=${jsonStringify(configContent.slice(0, 100))})`,
+      `MCP config is not valid JSON (scope=${scope}, file=${parse(filePath).base}, length=${configContent.length})`,
       { level: 'error' },
     )
     return {
diff --git a/src/utils/sessionStorage.ts b/src/utils/sessionStorage.ts
index 6d775d6..b47a143 100644
--- a/src/utils/sessionStorage.ts
+++ b/src/utils/sessionStorage.ts
@@ -1344,7 +1344,11 @@ class Project {
 
   setRemoteIngressUrl(url: string): void {
     this.remoteIngressUrl = url
-    logForDebugging(`Remote persistence enabled with URL: ${url}`)
+    logForDebugging(
+      url
+        ? 'Remote persistence enabled (remote ingress configured)'
+        : 'Remote persistence disabled',
+    )
     if (url) {
       // If using CCR, don't delay messages by any more than 10ms.
       this.FLUSH_INTERVAL_MS = REMOTE_FLUSH_INTERVAL_MS